Nayera Anwar

CHAPTER

7

Introduction, 56 Injurious agents, 56

Degeneration, 57 Accumulations, 58

Apoptosis, 61 Necrosis, 64

Miscellaneous types, 66 (Autolysis, autophagy, immune-

genic cell death, keratinization, mitotic catastrophe, anoikis, ex-

citotoxicity, paraptosis, pyropto-sis, necroptosis, autoschizis, en-

tosis, symplastic changes, cell ageing and Wallerian degenera-

tion) After effects of cell death, 68

Gangrene and pathologic calcifi-cation, 68

Clinical relevance, 68 ( Diagnostic role , predictor of

survival, guide to therapy, apop-tosis targeted therapy, arterial

embolization)

Outline

INTRODUCTION

The cells undergo a variety of changes when subjected to stress or injury, usually referred to

as retrogressive changes. The type of change is largely dependent on the degree and duration of

injury. Thus, mild injuries of short duration are unlethal and produce reversible changes called

degeneration. Conversely, severe injuries of long duration, result in irreversible damage, namely

cell death. In addition, a miscellaneous group of various retrogressive changes are reported with

overlapping features and mechanisms. Biochemi-cal and electron microscopic changes appear first

(Table 7-1). The microscopic and gross changes subsequently appear. In degeneration, apoptosis

and necrosis, the changes affect the biochemical structure of the cell itself. Conversely, in another

group of retrogressive change, namely: cell accu-mulation or infiltration, an abnormal material

accumulates intracellular or extracellular as a re-sult of genetic or metabolic disorder. The cellular

degenerative changes in this case are secondary to a pressure effect of the accumulated material.

Thus, both degeneration and accumulations are characterized by abnormal structural changes

and decreased functions. The present chapter reviews these cellular retrogressive changes and

their mechanisms.

INJURIOUS AGENTS

Cell injury may be attributed to intrinsic

(genetic) or extrinsic (environmental) factors. Intrinsic or genetic factors include gene muta-

tions or deficiency of functional proteins such as enzyme defects in inborn errors of metabo-

lism or accumulation of damaged DNA. Extrin-sic factors include: (1) hypoxia, is the most

common injurious agent, (2) free radicals which are two types: (a) reactive oxygen species, ROS

(superoxide O2−, hydrogen peroxide H2O2, hydroxyl radical-OH, nitric oxide NO, peroxy-

nitrite ONOO, halide reagent HOCl), and (b) non ROS radicals (CCl4 generates highly toxic

CCl3), (3) physical agents as ionizing radiation, (4) chemical agents (chemotherapeutic drugs

and toxins), (5) infections (bacteria, rickettsia, viruses and fungi), (6) immunologic agents

(hypersensitivity reactions, anaphylactic reac-tions and autoimmune diseases), (7) nutritional

deficiency, (8) ageing, and 9) idiopathic.

DEGENERATION

The Mechanism

A common initial cause of all types of degen-

eration is damage of cell membrane and mito-chondrial membrane (adenosine triphosphate,

ATP depletion). This results in a series of chang-es including: (1) failure of sodium-potassium

pump: lack of ATP interferes with generation of phospholipids essential for membrane integrity.

This results in damage to membrane pumps (sodium-potassium and calcium pump) with con-

sequent intracellular accumulation of sodium and depletion of potassium in the cell. The accumu-

lation of sodium in the cell results in increase in intracellular water to maintain iso-osmotic pump

(hydropic degeneration), (2) intracellular lactic acidosis: with continuous depletion in ATP, aer-

obic respiration fails, followed by switch to an-aerobic glycolysis. This results in rapid depletion

of glycogen, accumulation of lactic acid, lowering the intracellular pH with subsequent clumping in

nuclear chromatin, (3) failure of calcium pump: calcium influx within the cell, causes mitochon-

drial swelling and increased permeability, and (4) reduced protein synthesis: membranes of endo-

plasmic reticulum and Golgi apparatus swell up and ribosomes detach from rough endoplasmic

reticulum. Polysomes are degraded to mono-somes, thus dispersing ribosomes in the cyto-

plasm and alter their role in protein synthesis through disturbance in protein trafficking mech-

anism (that takes proteins from one location and targets them to a second location. Within Golgi,

proteins are modified and packaged into vesicles in the ER. A group of these vesicles fuse, and

form the cisterna. As the protein moves through the stack, it is modified by resident Golgi en-

zymes at specific locations in the apparatus. The-se modifications are important because they pro-

vide the signal that determines the final destina-tion of the protein whether to lysosomes or to

cell membrane). Release of lysosomal enzymes triggers biochemical changes (mucoid degenera-

tion). Depletion of protein synthesis occurs in Golgi apparatus as well. Thus, degeneration is

the accumulation of metabolites or other sub-stances in a cell damaged by preceding injury. Up

to this point, withdrawal of the injurious agent can reverse cell injury with cell recovery.

Ultrastructural Features The plasma membrane is intact with dimin-

ish and blunting of microvilli. There is swelling of mitochondria with formation of small phos-

pholipid-rich amorphous densities in mitochon-drial matrix due to calcium influx. Swelling of

endoplasmic reticulum and Golgi apparatus is observed with ribosomes detached from rough

endoplasmic reticulum. There are intracytoplas-mic myelin figures, derived from degenerating

membranes (cell membranes, mitochondrial membranes and lysosomal membranes), enclos-

ing water and dissociated lipoproteins between the lamellae of injured membranes. Cytoskele-

ton is aggregated and nucleus shows clumped chromatin (Table 7-1).

Pathologic Features

There are three morphologic forms of degener-ation:

1. Hydropic Degeneration. Also known as cloudy swelling is the initial event in all types of degen-

eration. The condition is best seen in organs with intense metabolic rate such as the liver,

kidneys and brain. The main pathologic feature is either formation of one large clear cytoplas-

mic vacuole (ballooning degeneration) or multi-ple small vacuoles (vacuolar degeneration). The-

se cytoplasmic vacuoles represent distended segments of the ER (P 7-1).

2. Hyaline Degeneration: This is a common de-

scriptive histologic term for the pathologic ap-

pearance of glassy, homogeneous, eosinophilic,

proteinaceous material that may be intracellular

or extracellular. Four examples of intracellular

hyaline degeneration are described: (1) proximal

renal tubular epithelial cells, (2) Mallory‟s bodies

in alcoholic liver which are hyaline aggregates of

intermediate filaments/hyaline aggresomes that

form in liver cells (aggresome, multiubiquitinat-

ed molecules formed when the capacity of the

proteasome is exceeded by the production of

aggregation-prone misfolded protein), (3) cyto-

plasmic Russell bodies are immunoglobulins

that escape intracellular degradation and can

gather in distended endoplasmic reticulum, and

form intracytoplasmic globules without block-

ing normal secretory pathways. Russell bodies

are observed in inflammatory and neoplastic

plasma cells (P 7-2), and (4) Dutcher bodies are

Cell Degeneration and Death 57

cytoplasmic immunoglobulin inclusions that

invaginate within the nucleus. Intranuclear

Dutcher bodies accumulate in macroglobuline-

mia and neoplastic plasma cells and in any cIg-

producing B-cell lymphoma (P 7-3). Extracellu-

lar hyaline examples include: hyaline degenera-

tion in leiomyoma (P 7-4), old scars, hyaline ar-

teriolosclerosis in hypertension and diabetes

mellitus, renal glomeruli in chronic glomerulo-

nephritis and corpora amylacea.

3.Mucoid Degeneration: Mucoid degeneration is a deposition of mucinous material in epithelial

and connective tissue in excessive amounts. It is a mucus like composed of proteins complexed

with mucopolysaccharides. Myxoid degenera-tion is a biochemical change that occurs in col-

lagen with pathologic weakening of fibrous tis-sue through the action of lysosomal enzymes.

Fibrous tissue collagen (type I), a fibrous pro-tein of complex helical structure, is changed to

acid glycosaminoglycans with fragmentation of collagen fibrils. Both epithelial and connective

tissue mucin stain by Alcian blue. However, epi-thelial mucin is periodic acid-Schiff (PAS) posi-

tive, whereas, connective tissue mucin is posi-tive with colloidal iron. Mucoid degeneration

may affect epithelium or connective tissue: (1) epithelial mucin: Catarrhal inflammation of mu-

cinous aero-digestive mem branes, mucocele in oral cavity and gall bladder, and mucinous tu

mors of ovary and gastrointestinal tract (P 7-5)

and (2) connective tissue mucin: myxoid changes in some tumors (e.g. myxomas, neurofibromas,

fibroadenoma, soft tissue sarcomas), myxoma-tous changes of dermis in myxedema, myxoid

changes in fibrous tissue of ganglion of joints (P 7-6).

ACCUMULATIONS

Accumulations may be intracellular or extra-

cellular. Stockpiled substances may be lipids, pro-tein, glycogen or pigment. There are four main

pathways of abnormal intracellular accumula-tions: (1) accumulation of normal constituents of

deranged cell metabolism as in steatosis, (2) pro-tein misfolding transport leading to accumulation

of abnormal proteins as in Parkinson‟s disease and Alzheimer‟s disease (3) accumulation of ab-

normal endogenous substances produced as a result of abnormal metabolism due to lack of

some metabolic enzymes. This occurs in lysoso-mal storage disease or inborn errors of metabo-

lism, and (4) inhalation or ingestion of indigesti-ble material with subsequent accumulation of

exogenous material due to lack of enzymatic mechanism to degrade the accumulated material

or transport them to other sites (exogenous pig-ments, anthracosis, asbestosis, silicosis, and

pneumoconiosis). Accumulations could be he-reditary or acquired. Degeneration is the ultimate

secondary effect of cell accumulation.

El-Bolkainy Surgical Pathology 58

Cell Content Degeneration Cell Death

Cell Membranes

Microvilli

Mitochondria

Intact

Diminished

Swelling

Disrupted and deposits

of myelin figures Lost

Vacuoles and deposits of calcium salts

RER

Ribosomes

Intact and swollen

Detached from RER

Lysis

Dispersed

Lysosomes Cytoskeleton

Nucleus

Intact Intact and aggregated

Condensed

Rupture Dispersed

Fragmentation or lysis

Table 7-1 Ultrastructure of Retrogressive Changes

RER, rough endoplasmic reticulum

Intracellular Accumulations

1. Lipid Accumulations is lipid degradation prod-

ucts in the cytoplasm of cells, which accumulate in lysosome bound vacuoles. These materials are

usually products of peroxidation of fat and may be lipofuscins, ceroid, or cholesterol. These lipid

particles accumulating in the cytoplasm of cells convert into complex, non-degradable products.

Lipid accumulation, also known as fatty changes or fatty degeneration, includes two subtypes :

a-Triglyceride accumulations; (steatosis, fatty met-amorphosis, fatty degeneration and fatty infiltra-

tion), occurs in hypoxic, toxic (CCl4, chloro-form, aflatoxins) or metabolic injury (alcohol,

obesity, diabetes and protein calorie malnutri-tion). It is seen mainly in cells involved in and

dependent on fat metabolism, mostly in liver and myocardial cells (P 7-7). Mechanism of fatty

changes of liver occur through one of following: (i) increased entry or synthesis of free fatty acids

in liver, (ii) decreased fatty acids oxidation into ketone bodies resulting in increased triglycerides,

(iii) increased α-glycerophosphate causing in-creased esterification of fatty acids to triglycer-

ides, and (iv) block in lipoprotein excretion. Fat-ty liver from chronic alcoholism is multifactorial.

b-Cholesterol accumulations: (i) xanthoma and xanthelasma (P 7-8), (ii) cholesteatosis, with fo-

cal accumulation of cholesterol laden macro-phages in gall bladder, and (iii) Niemann-Pick

disease type C, a lysosomal storage disease due to mutation in enzyme responsible for choles-

terol trafficking. 2. Protein Accumulations. These are due to bio-

chemical change in proteins or excessive accu-mulation of immunoglobulins synthesized in cis-

ternae of the rough endoplasmic reticulum of the plasma cells. Accumulations occur through dis-

turbance in protein trafficking mechanism. Pro-tein trafficking mechanism is as follows; proteins

from the rough endoplasmic reticulum are sent to the Golgi that takes proteins from one loca-

tion and targets them to a second location. With-in Golgi, proteins are modified and packaged

into vesicles in the ER. A group of these vesicles fuse, and form the cis-cisterna. As the protein

moves through the stack, resident Golgi enzymes at specific locations in the apparatus modify it.

These modifications are important because they provide the signal that determines the final desti-

nation of the protein whether to lysosomes or to cell membrane. The histology is charachterized

by protein accumulations present as hyalin, ho-mogeneous glassy eosinophilic cytoplasmic drop-

lets. Protein accumulates intracellular or extracel-lular. Intracellular variant occurs in; renal tubular

epithelium in diabetes, Mallory bodies in alcohol-ic liver, Russell bodies and Dutcher bodies in

plasma cell. 3. Glycogen Accumulations. These occur in some

diseases characterized by prolonged hyperglyce-mia such as diabetes mellitus or Cushing‟s dis-

ease (excess glucocorticoids), both are associated with defective glycogen or glucose metabolism,

thus, glycogen accumulates as clear cytoplasmic vacuoles in hepatocytes.

4. Pigment Accumulations. The pigment may be exogenous or endogenous in origin. Exogenous

indigestible pigments, such as carbon. Endoge-nous such as iron (usually due to overload, as in

hemosiderosis) or due to altered metabolism of breakdown products of melanin and hemoglo-

bin. There are three types of endogenous pig-ment: (1) melanin is the most common, and its

accumulation develops through defect in tyrosine metabolism. Melanin is granular protein contain-

ing pigment produced by melanocytes where its increased production occurs in association with

tumours of the melanocytes, excessive irradia-tion, and effect of sunlight, (2) haemoproteins

are derived from haemoglobin, cytochromes and their break down products. Haem-drived pig-

ments are “porphyrin, hemosiderin, acid hematin and bilirubin”. (i) Porphyrin accumulation is due

to inborn errors in porphyrin metabolism at-tributed to genetic deficiency of one of the en-

zymes required for haem synthesis. Porphyrin accumulation occurs in bone marrow or in liver

(erythropoietic or hepatic porphyrias), (ii) Hemo-siderin is iron pigment, encountered in trauma,

excessive hemorrhage or hemolysis. It accumu-lates in parenchymal cells (liver, pancreas, kidney,

and heart) or reticuloendothelial cells (the liver, spleen, and bone marrow). A common example

is hemochromatosis, where excess iron is stored in organs, leading to organ toxicity. Hereditary

hemochromatosis is an error of iron metabolism characterized by inappropriately high iron ab-

sorption resulting in progressive iron overload (P 7-9). Hereditary hemochromatosis occurs due to

HFE gene missense mutations, located at band 6p22. It leads to enhanced accumulation of iron

in liver, heart, pancreas, pituitary, joints, and skin. However, two other types of hemochromatosis

have been identified: juvenile hemochromatosis

Cell Degeneration and Death 59

or type 2 (gene HFE2), and an adult form de-fined as hemochromatosis type 3 (gene HFE3).

Regardless to the type of hemochromatosis, the histopathologic features are similar. Once the

toxic level of iron is reached, there is four times increased rate of liver phospholipid lipoperoxida-

tion, protein oxidation and cell damage. Excess iron is hazardous, because it produces free radi-

cals. These, can produce DNA cleavage, im-paired protein synthesis, and impairment of cell

integrity and cell proliferation, leading to cell in-jury and fibrosis, (iii) Acid hematin (non- iron

pigment), seen in chronic malaria and mis-matched blood transfusion and it accumulates in

macrophages and hepatocytes, and (iv) Bilirubin or haematoidin (non-iron containing pigment) -

following excessive hemorrhage or hemolysis, and failure of the liver to conjugate bilirubin into

bile, thus, bilirubin accumulates in hepatocytes and kupffer cells, and (3) lipofuscin, lipid derived

pigment „wear-and-tear pigment‟. It is a golden brown pigment seen in ageing particularly in liver

and heart or in debilitating diseases. It is break-down product of lipid peroxidation.

Extracellular Accumulations

The two major types of extracellular accumu-

lations are cholesterol and protein. which share a common mechanism leading to changes in quan-

tity and quality of normal components, as well as the appearance of abnormal materials. The etiol-

ogy may be either congenital defect or acquired pathology.

1. Cholesterol Accumulations: it is a distinct type of lipid accumulation, different from fatty accu-

mulation in which cholesterol accumulates extra-cellularly either due to disturbance of cholesterol

and cholesterol esters metabolism or due to dis-turbance in neutral fat metabolism causing depo-

sition of lipids and lipoproteins. LDL oxidation is regulated by enzyme lipoprotein associated

phospholipase A2(Lp-PLA2), which is an en-zyme linked to inflammation of blood vessels,

and free radicals in endothelium. The common-est example is cholesterol accumulations in ath-

erosclerosis in which plaque builds up inside ar-teries. Plaque is formed of fat, cholesterol, calci-

um, and other blood substances where cholester-ol and cholesterol esters accumulate as lipid vac-

uoles within intima of arteries and crystalize in the form of long needles and present morpho-

logically as clefts within tissues (P 7-10).

2. Protein Accumulations: includes amyloidosis, hyalinosis, myxoid accumulation and elastosis:

a- Amyloidosis; (P 7-11) is the extracellular variant of protein accumulation. It is deposits of

misfolded protein of variable causes as idio-pathic, myeloma (AL protein) and chronic in-

flammatory conditions as tuberculosis or rheu-matoid arthritis (AA protein). This abnormal pro-

tein is positive for Congo red and produces green birefringence on polarized light. Amyloidosis

causes pressure atrophy and degeneration of epi-thelium in affected organs with subsequent func-

tional failure. Mechanism: during proteins synthe-sis, some misfolded protein fragments are

formed which escape proteolysis by protease, they aggregate to form oligomers. The oligomers

aggregate together to make amyloid that inter-feres with proper organ function. The type of

protein that is misfolded and the organ or tissue in which the misfolded proteins are deposited

determine the clinical manifestations of amyloi-dosis. There are four types of amyloidosis: (i) my-

eloma-associated amyloidosis, occurs in multiple myeloma where up to 15% of patients may have

systemic deposits of amyloid, (ii) familial amyloi-dosis, as in Mediterranean fever, (iii) Alzheimer‟s-

associated amyloidosis, of ageing, and (iv) endo-crine amyloidosis, is a major component in me-

dullary thyroid carcinoma and pancreatic islets, associated with type 2 diabetes mellitus where the

precursor protein, termed islet amyloid or islet-associated polypeptide (IAPP) is secreted by

β−cells of the islets. b- Hyalinosis: which is accumulation of

pathological albumin (molecules composed of albumin, lipid, carbohydrates, and antibodies). It

is a complex structure variable in variable types of vascular hyalinosis: (i) simple, consists of pro-

tein only and it occurs in hypertension, (ii) lipo-hyalin (consists of proteins and lipids) which oc-

cur in diabetes mellitus, and (iii) complex (protein and immune complex) which occurs in rheumatic

fever, autoimmune diseases. Hyalinosis occurs in old scars, thrombi and wall of renal arterioles in

long standing diabetes mellitus, autoimmune dis-eases and chronic hypertension. Hyalinosis is the

finale of fibrinoid changes and necrosis. c- Myxoid accumulation: which is accumulation

of acid mucopolysaccharides. Diagnosed histo-logically by toluidin blue, PAS reaction.

d- Elastosis: may be actinic stimulation of fibro-blasts, promoting synthesis of elastotic material;

or that the material is a degradation product of

60 El-Bolkainy Surgical Pathology

collagen, elastin or both. The responsible gene is ELN gene, lies on chromosome 7 and en-

codes a protein that is one of the two compo-nents of elastic fibers. Deletions and mutations

in ELN gene are associated with supravalvular aortic stenosis and autosomal dominant cutis

laxa.

CELL DEATH

The five types of cell death are illustrated in (Figure 7-1) most important types are apoptosis

and necrosis. Comparison between the two types are illustrated in ( Table 7-2).

APOPTOSIS

Apoptosis is a Greek term means "falling

off" leaves of tree. It is a process of pro-grammed cell death that occurs in multicellular

organisms. Apoptosis is type I cell death which may be physiologic or pathologic. Physiologic Pro-

cesses: separation of finger webs in embryo, en-dometrial shedding, regression of lactating

breast, normal cell destruction followed by re-placement proliferation such as in intestinal

epithelium, and involution of the thymus in ear-ly age. Between 50 and 70 billion cells die each

day due to apoptosis in the average human adult. Pathologic Processes: which is due to: therapy

effect (radiotherapy, chemotherapy), cytotoxic T cell in immune mechanisms (graft- rejection re-

actions), progressive depletion of CD4+ T cells in the pathogenesis of AIDS, viral infections,

prostatic atrophy after orchiectomy, and neuro-degenerative diseases of CNS.

The Mechanism

Apoptosis is executed through the action of a family of 12 cytoplasmic enzymes, called

caspases, which cleave the protein of cytoskele-ton. They have been divided into two main clas-

ses, namely: initiator procaspases (caspase 1, 2, 4, 5, 8, 9, 11 and 12) and effector caspases

(caspase 3, 6 and 7). Initiator caspases initiate and propagate the apoptotic signal, whereas, ef-

fector caspases cleave cell proteins. Caspase 3 is the main caspase, which mediate apoptosis. It is

critical executioner of apoptosis, as it is either partially or totally responsible for the proteolytic

cleavage of many key proteins such as the nucle-ar enzyme poly (ADP-ribose) polymerase

Cell Degeneration and Death 61

Fig 7-1 Types of cell death. (A) Apoptosis. The cell shrinks, chromatin is condensed and fragmented, develops blebs, but cell membrane is intact. The resulting apoptotic sacs are phagocytosed by histiocytes. (B) Necrosis. The

cell swells, cell membrane rupture and cell organelles are indistinct. (C) Autophagy (self eating). The cell contains a prominent lysosomal vesicle which leads to autophagocytosis. (D) Paraptosis. The cell is normal in

size but contains multiple cytoplasmic vacuoles. (E) Autoschizis. The cell shrinks in size mainly due to loss of cytoplasmic mass.

(PARP), thus, activation of caspase 3 leads to the activation of other enzymes such as endonucleas-

es and proteases. Endonucleases induce the clas-sic internucleosomal DNA fragmentation of

multiple of 180 base pairs producing a character-istic ladder-like pattern by electrophoresis. Prote-

ases induce protein cross-linking and cell shrink-age. There are two main pathways to activate

caspases, namely: the extrinsic or membranous, and the intrinsic or mitochondrial pathways (Fig

7-2).

The extrinsic apoptotic pathway recognizes and eliminates cells with foreign protein on their sur-

face. Examples include: (1) NK and cytotoxic lymphocytes expression of perforin and

granzyme B, (2) FAS-mediated elimination of autoreactive T-cells in the thymus, and (3) TNF-

α and death receptors. The procaspase 8 is acti-vated by these membrane signals.

The intrinsic pathway functions to eliminate se-

nescent or damaged cells of the organism, and caspases are activated by the liberation of cyto-

chrome c from the mitochondria to the cyto-plasm. Telomere shortening or any DNA dam-

age by anoxia, irradiation or mutation is sensed by the tumor suppressor gene TP53 which acti-

vates the proapoptotic genes (BAX and BAD) leading to the liberation of cytochrome c from

the mitochondria to the cytoplasm (Fig 7-2). Cy-tochrome c binds with the adapter protein Apaf-

1, and procaspase-9 to form an “apoptosome” complex, which activates caspases. It is paradoxi-

cal that cytochrome c, a most useful electron transfer agent in oxidative phosphorylation in

mitochondrion, becomes a deadly killer to the cell when released into the cytoplasm.

Apoptosis is under strict control by a variety of genes (Fig 7-2). BAX and BAD gene expressions

are proapoptotic, whereas, Bcl-2 and Bcl-x are antiapoptotic. NOXA, which inhibits Bcl-2, is

considered proapoptotic. These proteins act by affecting the permeability of mitochondrial

membrane to cytochrome-c. Thus, BAX in pres-ence of calcium ions increases mitochondrial

membrane permeability, a process blocked by Bcl-2.

Apoptosis is considered the physiologic mech-anism of choice to remove cells damaged by ag-

ing or genetic mutation, hence protection against cancer. Normal adult cells have only a limited

capacity of cell division.

The ends of chromosomes (telomeres) contain many copies of guanine (G)- rich repeats

(TTAGGG)N . The enzyme DNA polymerase is unable to replicate telomeres, which shorten by

about 100 base pairs with each division. This is referred to as the end replication problem. When

DNA shortening reaches a critical level after 50 divisions, it is sensed by TP53 as a DNA break,

resulting in expression of p21 and Bax with per-manent arrest of cell cycle (cell senescence) and sub-

sequent apoptosis. In this way, telomeres may be considered as death timers. The enzyme telomer-

ase can correct telomere shortening (Chapter 2). Germ cells, stem cells and malignant cells are

rich in telomerase, hence they are immortal. Con-versely, normal somatic cells lacking this enzyme

are short-lived.

Role of Apoptosis in Carcinogenesis Generally, the mechanisms by which evasion

of apoptosis occurs can be broadly divided into: (1) disrupted balance of pro-apoptotic and anti-

apoptotic proteins, (2) reduced caspase function, and (3) impaired death receptor signaling.

Morphologic Features

1. Ultrastructural Features: there is extensive plasma membrane blebbing, but with maintained

integrity until the final stages of the process, apoptotic bodies (near spherical bodies, com-

posed of cytoplasm and condensed organelles, with or without nuclear fragments), nuclear

shrinkage (pyknosis), nuclear fragmentation into two or more fragments (karyorrhexis), chromatin

condensation, chromosomal DNA fragmenta-tion, and global mRNA decay. It is worthy to

mention that early phases of apoptosis do not affect membrane permeability, nor do they alter

mitochondrial activity (Table 7-2, P 7-12). 2. Histopathologic Features: apoptotic cells ap-

pear as round to oval shrunken cell of intensely eosinophilic cytoplasm containing pyknotic nu-

cleus with condensed chromatin (Fig 7-1A and P 7-13). Apoptosis is not associated with any in-

flammation since apoptotic cells do not break and release their cell contents. Also, apoptotic

cells are immediately phagocytosed by surround-ing cells, thus, escaping necrosis, and these phag-

ocytes do not produce anti-inflammatory cyto-kines. In general, the light microscopy approach

can provide both qualitative and quantitative data (Table 7-2).

62 El-Bolkainy Surgical Pathology

Cell Degeneration and Death 63

Feature Apoptosis Necrosis

Pathobiology

Etiology Genetically determined (suicidal) Accidental (homicidal)

Nature Physiologic or pathologic Pathologic

Mechanism Mitochondrial membrane

permeability Cell membrane damage

Trigger pathway

DNA breakdown

Intrinsic or extrinsic

Internucleosomal

Extrinsic

Random

Degrading

enzymes

Caspases Non-caspase

Caspase inhibtors* Present Absent

ATP Sustained Lost

Cell Morphology

Cell death

Single cells

Groups of cells

Cell size Shrinkage Swelling initially

Cell membrane Intact Ruptured

Cell contents Present Released

Nucleus Fragmentation Lysis

Apoptotic bodies Lysosomes

Present Intact

Absent Breakdown

Inflammation Absent Always present

Table 7-2 Comparison of Apoptosis and Necrosis

Fig 7-2 The two pathways of apoptosis. The extrinsic pathway is a reaction to foreign protein, whereas, the intrinsic pathway is a programmed cell death to eliminate senescent or DNA damaged cells. The enzymes

caspases play a major role in both pathways.

* Includes : (zVAD, FmK, p53, BAF), Xiap and Bcl-xL

64

Detection Techniques

These can be grouped into four main

groups, namely:

1. The immunohitochemical techniques: These detect

apoptosis by using antibodies which recognize activated caspase-3, caspase-cleaved cytokeratin

18 or TUNEL assay.

(a) Cleaved Caspase 3: detection of activated caspase-3 is an easy, sensitive, and reliable meth-

od for detecting and quantifying apoptosis. It is a specific tool for identifying apoptotic cells in tis-

sue sections, even before all the morphological features of apoptosis occur.

(b) Cleaved Cytokeratin 18 (CK18): during apop-tosis, CK18 undergoes dramatic reorganization

and is cleaved by the caspases (caspase-3, -6, -7 or -9), generating an apoptosis-specific neo-

epitope recognized by the monoclonal antibody M30 (MAb M30). C-K18 is expressed in carcino-

mas such as lung, liver, prostate, breast and co-lon, but absent in lymphoid, bone marrow and

neuronal cells (P 7-14). (c) TUNEL Assay: The terminal deoxynucleo-

tidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) technique has been used for

the detection and quantification of late apoptosis in histological tissue sections (P 7-15). It is time-

consuming and needs numerous cells to be ex-amined and is associated with a number of tech-

nical problems. 2. Apoptotic index: is determined by the number

of apoptotic cells per 1000 tumor cells or the number of apoptotic cells per 10 high-power

fields. This could be assessed by computer-assisted image analysis. Apoptotic index has been

shown to be of clinical and biological relevance in breast carcinomas, hepatocellular carcinoma,

renal cell carcinoma, prostatic carcinoma, laryn-geal carcinoma, and cervical carcinoma. Accurate

detection of apoptosis in various stages help in assessing apoptotic index, which is known to be

a predictor of chemotherapy response and is an indicator of prognosis and metastasis thereby

predicts outcome of the treatment. 3. Flow Cytometry (FCM); is applied by using

labeled annexin, which is Annexin V in conjunc-tion with fuorescent dye (DNA marker) such as

propidium iodide (PI). Thus, combination of the two can be used to monitor the progression of

apoptosis: early-stage apoptosis shows annexin expression whereas; late-stage apoptosis and cell

death show both annexin and PI expression. Other flow cytometric fuorescent dyes include

propidium iodide (PI) and DAPI staining (4,6-diamidino-2-phenylindole) , however, it is not

highly specific. 4. DNA-Ladder electrophoresis assays; the princi-

ple is to demonstrate the Apoptotic DNA frag-mentation in the DNA of treated cells.

NECROSIS

Persistent effect of injurious agent, results in

irreversible damage or point of no return and cell death. Irreversible cell injury is characterized by

severe damage of three vital cell systems: (1) irre-versible mitochondrial damage, (2) severe dam-

age of the membranes (cell membrane, mito-chondrial, and lysosomal), and (3) Damage of

genetic apparatus (DNA and RNA).

The Mechanism

The mechanism of cell death is mainly through excess calcium influx that causes cell

injury through several mechanisms: (1) mito-chondrial damage: due to excess calcium influx

where calcium collects in the mitochondria disa-bling its function, (2) Severe membrane damage:

is due to activated phospholipases and is accom-plished by: (a) either decreased mitochondrial

phospholipid synthesis or increased phospholip-id breakdown due to calcium overload, (b) acti-

vation of endogenous phospholipases which de-grade membrane phospholipids, (c) activation of

intracellular proteases, break down both mem-brane and cytoskeletal proteins, and (d) reactive

oxygen species that trigger lipid peroxidation and cause phospholipid depletion, (3) lysosomal

membrane damage: due to activated lysosomal hydrolytic enzymes by oxygen depletion in the

cell and acidic pH. Activation of hydrolytic en-zymes (e.g. hydrolase, RNAase, DNAase, prote-

ase, glycosidase, phosphatase, lipase, amylase, cathepsin etc) induces enzymatic digestion of

cellular components and hence cell death, and (4) nuclear damage: is due to activation of endo-

nuclease. Finally, the cell dies by necrosis, invari-ably associated with inflammation and ends with

autolysis. The enzymes that digest the necrotic cells are derived from lysosomes of the dying

cells or from lysosomes of leuckocytes (induced as a component of inflammatory reaction).

Estimation of the elevated serum lysosomal en-zymes (glutamic oxaloacetic transaminase

(SGOT), lactic dehydrogenase (LDH), isoen-zyme of creatine kinase (CK-MB), and cardiac

troponins (cTn) may be used as clinical parame-

El-Bolkainy Surgical Pathology

65 Cell Degeneration and Death

ters of cell death.

Morphologic Features 1. Ultrastructural Features: There is nuclear

lysis. Plasma membranes appear discontinuous and may show rupture. This discontinuous mem-

brane is caused by cell blebbing and the loss of microvilli. There are evident myelin figures

(phospholipids derived from damaged cell mem-branes), and indistinct organelles (Fig 7-1B).

There is marked dilatation of mitochondria showing large flocculent, amorphous densities

(formed of calcium salts) in mitochondrial matrix (Table 7-1 and Table 7-2).

2. Histopathologic Features: The nuclear chang-

es in necrosis are determined by the manner in which its DNA breaks down: (a) Pyknosis, is

shrinkage, condensation and clumping of nucleus which becomes dark basophilic, (b) karyorrhex-

is, the shrunken nucleus fragments into small dispersed bits, and (c) karyolysis, is dissolution of

the nucleus due to the loss of the DNA by deg-radation. The two main features of cell necrosis

are: nuclear staining (usually negative) and evi-dence of inflammation and damage in surround-

ing tissues. Based on etiology and morphologic appearance, there are six distinctive morphologic

patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid and hemorrhagic necrosis:

Coagulative Necrosis

This is the most common type of necrosis caused by sudden cessation of blood flow,

(ischemic necrosis), and less commonly due to bacterial and chemical agents. It is necrosis of

portion in some organs as heart, kidney, adrenal and spleen in which the architecture of the tis-

sue is maintained, and can be observed by light microscopy. Coagulation occurs as a result of

protein denaturation, causing albumin to trans-form into a firm and opaque state. Gangrenous

necrosis can be considered a type of coagulative necrosis, characterized by ischemia of lower

limb and the gastrointestinal tracts with super-imposed infection

Histopathologic features; the cellular outlines are retained for a long time but their cytoplasmic and

nuclear details are lost. The necrotic cells are swollen and have eosinophilic cytoplasm, at-

tributed in part to the loss of cytoplasmic RNA and in part to denatured cytoplasmic proteins (P

7-16).

Liquefactive Necrosis Liquefactive necrosis is characterized by the

digestion of dead cells to form cystic spaces. It is encountered in suppurative inflammation and

brain infarcts. Because brain has high amounts of digestive enzymes and lipids, cells therefore

can be readily digested by their own enzymes. Histopathologic features; There are necrotic dead

leukocytes (pus), surrounding wall is formed by histiocytes, inflammatory cells with proliferating

capillaries and fibroblasts (P 7-17).

Caseous Necrosis

Caseous necrosis is a distinct type of coagula-tive necrosis with esinophilic granular appearance

(Dead cells disintegrate but are not completely digested, leaving granular particles). Caseous ne-

crosis is typically caused by mycobacteria (tuberculosis) due to cytotoxic effect of lipopoly-

saccharides present in the capsule of the tubercle bacilli.

Histopathologic features: Granuloma center shows areas of necrosis, formed of structureless

eosinophilic material having amorphous granular debris. Necrosis is rimmed by elongated radially

arranged epithelioid cells (modified elongated macrophages having slipper-shaped vesicular nu-

clei), fibroblasts, lymphocytes, histiocytes and Langhans giant cells (P 7-18).

Fat Necrosis Fat necrosis may be due to traumatic or enzy-

matic factors. It results from the action of acti-vated lipases on fat-rich anatomic location such

as breast, pancreas and mesenteric fat respec-tively (P 7-19). Enzymatic fat necrosis is ob-

served in peritoneal cavity after acute pancreati-tis because the released lipases cause hydrolysis

and rupture of adipocytes and release of neutral fat that changes into glycerol and free fatty ac-

ids. The leaked out free fatty acids complex with calcium to form calcium soaps (saponification)

and dystrophic calcification.

Fibrinoid Necrosis

Fibrinoid necrosis is a special form of necro-sis caused by immune-mediated vascular dam-

age. This occurs when complexes of antigens and antibodies are deposited in the walls of ar-

teries. These “immune complexes,” together with fibrin that has leaked out of vessels, result

in a pink filamentous structure or network

66

called fibrinoid. Histopathologic features: fi-brinoid necrosis is identified by bright eosino-

philic, hyaline-like deposition in the arterial wall. Necrotic focus is surrounded by nuclear debris

of neutrophils (P 7-20). .

Hemorrhagic Necrosis Hemorrhagic necrosis is necrosis associated

with hemorrhage. Hence, it is common in high-ly vascular organs such as the spleen and intes-

tine due to blockage of arterial and venous drainage of the affected organ. It may result

from vascular occlusion (volvulus) or non-occlusive intestinal infarction. In spleen, it is

due to embolism (splenic infarction), which is typically triangular in shape grossly.

Histopathologic features: there is diffuse hemor-rhage in intestinal mucosa, engorgement of mu-

cosal and submucosal veins with some fibrin thrombi in capillaries of necrotic mucosa (P 7-

21).

MISCELLANEOUS RETROGRESSIVE CHANGES

A heterogeneous group of retrogressive changes some have special features and represent special types of apoptosis and others have their

own mechanism of action.

Autolysis Autolysis (i.e. self-digestion) is total disintegra-

tion of the cell by its own hydrolytic enzymes generated and liberated from lysosomes. It is

encountered in vascular occlusions or as a post-mortem change or when tissue biopsy is re-

moved from the body and left unfixed. Autolysis is fast in tissues rich in hydrolytic enzymes such

as in the pancreas, and gastric mucosa; interme-diate in heart, liver and kidney; and slow in fi-

brous tissue. Autolysis is identified pathologically as homogeneous eosinophilic cytoplasm with

loss of cellular details and remains of cell debris (P 7-22).

Autophagy Autophagy (self eating) is classically observed

in starvation. Biochemically, autophagy is caspa-se-independent with increased lysosomal activity.

Autophagic cell contains massive autophagic vacuolization of the cytoplasm, prominent lyso-

somal vesicle and absent chromatin condensa-tion (Fig 7-1C). Detection methods include: elec-

tron microscopy, protein-degradation assays, as-says for marker-protein translocation to au-

tophagic membranes, but no DNA laddering.

Immunogenic cell death (ICD) Immunogenic cell death or immunogenic

apoptosis is a form of cell death caused by cyto-static agents such as anthracyclines, or radiother-

apy and photodynamic therapy (PDT), bacteria and viruses. Injury produces structural modifica-

tion of proteins and rendering them antigenic. The best example of immunogenic cancer cell

death is methotrexate therapy in gestational cho-riocarcinoma. Unlike normal apoptosis, immuno-

genic apoptosis of cancer cells can trigger an an-titumor immune response through activation of

dendritic cells (DCs) and consequent activation of specific T cell response. Most of the agents

inducing immunogenic cell death are targeting endoplasmic reticulum (ER), leading to ER stress

and production of reactive oxygen species (ROS). Both ER stress and ROS have a role in

regulating the immunogenicity of dying cancer cells. ICD is characterized by secretion of dam-

age-associated molecular patterns (DAMPs). These DAMPs are translocated after the induc-

tion of immunogenic apoptosis to the surface of dying cell where it functions as an “eat me” sig-

nal for professional phagocytes.

Keratinization Keratinization represents both: (1) a terminal

differentiation of stem cells and epidermis ending in a process of apoptosis and exfoliation and (2)

elimination of cytosolic organelles. It leads to the formation of corneocytes by protease activation.

Keratinization of squamous epithelium, both normal and neoplastic, is a biologic process that

terminates in apoptosis, hence, the term terminal differentiation. Cleaved CK18 immunohisto-

chemistry is conclusive for apoptosis. Cornifica-tion is exclusive to the eyes.

Mitotic Catastrophe

This denotes abnormalities in cell cycle, which explain a mechanism of a delayed mitotic-linked

cell death. It results from defective cell cycle check points or damage to microtubules leading

to aberrant chromosomal segregation. The main causes are chemotherapy and ionizing radiation.

Mitotic catastrophe is caspase-independent (at early stage) and shows abnormal CDK1/cyclin B

activation. The common detection methods in-clude: electron microscopy and assays for mitotic

El-Bolkainy Surgical Pathology

Cell Degeneration and Death 67

markers (mitotic phosphoprotein 2 (MPM2). Mitotic catastrophe produce three outcomes

namely: (1) aneuploid cells with malignant potential, (2) multinucleated giant cell (P 7-23), a result of en-

domitosis (nuclear division without cytoplasmic division) this results in a sterile multinucleated

giant cells, (3) Micronuclei which result if small fragments of chromosomes fail to segregate dur-

ing telophase (P 7-24). Multinucleated giant cells, as well as, cells with micronuclei are sterile non-

dividing cells that will ultimately die.

Anoikis

Anoikis (means, to be homeless). It is a type of programmed cell death almost identical to

apoptosis except in its induction. It is induced by a loss of correct cell/extracellular matrix attach-

ment. Cells require intact integrin family recep-tors to suppress anoikis, and the process requires

mitochondrial integrity. Metastatic cells are re-sistant to anoikis and often have increased levels

of the death receptor-inhibiting protein FLIP.

Excitotoxicity Excitotoxicity is the pathological process

by which nerve cells are damaged or killed by excessive stimulation by neurotransmitters such

as glutamate. This occurs when receptors for the excitatory neurotransmitter glutamate (glutamate

receptors) are over activated by glutamatergic storm. Excitotoxins bind to these receptors.

Pathologically high levels of glutamate, can cause excitotoxicity by allowing high levels of Ca2+ in-

flux into cells with subsequent mitochondrial damage, thus, activates a number of enzymes

(phospholipases, endonucleases, and proteases such as calpain). These enzymes damage some

cell structures (cytoskeleton, membrane, and DNA). Excitotoxicity may be involved in spinal

cord injury, hearing loss (through ototoxicity), multiple sclerosis, Alzheimer's disease and Park-

inson‟s disease.

Paraptosis Paraptosis is a type of programmed cell death,

morphologically distinct from apoptosis and ne-crosis. It presents as multiple cytoplasmic vacu-

oles (Fig 7-1D). Paraptosis lacks several charac-teristics of apoptosis: (1) it is independent of

caspase activation, and (2) it lacks apoptotic mor-phology such as membrane blebbing, chromatin

condensation, and nuclear fragmentation. Several cancer drugs that can avoid many harmful side

effects of traditional chemotherapy could induce parapotosis.

Pyroptosis

Pyroptosis is a programmed cell death observed in cells infected by microbes. Unlike paraptosis,

pyroptosis involves activation of caspase-1. The cell is normal in size but contains multiple cyto-

plasmic vacuoles.

Necroptosis Necroptosis occurs in viral infections (ligation

of viral protein to TNFR1). It resembles necrosis morphologically and apoptosis in its mechanism

(programmed cell death). It resembles necrosis in being: caspase- independent, associated with re-

lease of reactive oxygen species (ROS), lysoso-mal membrane injury, cell membrane damage

and associated inflammation. Necroptosis is con-sidered the most understood form of regulated

or programmed necrosis.

Autoschizis Autoschizis is a term derived from the Greek

language, which means, "split itself". It describes a unique form of cell death induced during can-

cer treatment by ATP depletion (Fig 7-1E). The cell shrinks in size due to the loss of cytoplasmic

mass without loss of cell organelles. Only the nucleus and organelles remain surrounded by a

thin rim of cytoplasm. There is mitochondrial condensation as well as morphologic degradation

of the nucleus and nucleolus without the for-mation of apoptotic bodies and destruction of

the cell membrane. Thus, autoschizis shows both apoptotic and necrotic morphologic characteris-

tic.

Entosis Entosis was originally described as a form of

„cellular cannibalism‟ in lymphoblasts from pa-tients with Huntington's disease, in which one

cell engulfs one of its live neighbors, which then dies within the phagosome through lysosomal

degradation. Entosis is not inhibited by Bcl-2 or Z-VAD-fmk.

Symplastic Changes

This denotes a deformed shape, and is ob-served in nuclei of some soft tissue and endo-

crine tumors. It is characterized by large pleo-morphic hyperchromatic nuclei that characteristi-

cally lack mitotic activity (P 7-25). This phenom-

68

-enon is probably the result of disturbed cell cycle with DNA synthesis without mitosis

(unsynchronized cycle) resulting in hyperploidy. The ultimate fate of such abnormal cells is most

probably degeneration and death.

Cell Ageing Cell ageing or senescence is the impaired ability

of the cell to undergo replication or repair. Cellu-lar ageing result from a combination of several

factors including: (1) increased cell damage, (2) reduced ability of DNA repair, (3) impaired

chaperone and proteasome functions (defective protein homeostasis), and (4) reduced capacity of

cells to divide secondary to progressive shorten-ing of chromosomal ends, namely the telomeres.

Ubiquitin is a stress protein that directs intra-cellular protein molecules for either degradation

or synthesis. An age-related impairment of ubiq-uitin-dependent proteolysis results in enhanced

accumulation of abnormal damaged-cytotoxic proteins. This mechanism is associated with neu-

rodegenerative disorders including Alzheimer‟s and Parkinson‟s disease. It is noteworthy that

damaged and aggregated proteins are turned over by two proteolytic pathways: ubiquitin- pro-

teasome system and autophagy.

Wallerian Degeneration Wallerian degeneration occurs in nervous sys-

tem, in which part of a neuron or axon degener-ates without affecting the main nerve cell body.

This term describes degeneration of cell process-es only (incomplete degeneration), (P 7-26).

AFTER EFFECTS OF CELL DEATH

Gangrene: Gangrene is defined as ischemic necrosis with

super-added putrefaction, as a result of vascular occlusion. There are three main types of gan-

grene dry, wet and gas: (1) Dry gangrene. It results from arterial occlusion and common causes in-

clude: atherosclerosis, Burger disease and diabe-tes with affection of foot. A line of separation

marks the junction of viable and gangrenous tis-sues. (2) Wet gangrene. It results from simultane-

ous occlusion of both arteries and veins supply-ing the tissues. Common sites affected include

the small intestine (volvulous or mesenteric vas-cular occlusion) and lung infarcts. The line of

demarcation is indistinct between viable and gan

grenous tissues. Any case of dry gangrene can progress to wet gangrene if there is secondary

bacterial infection (C. Perfringens). (3) Gas gan-grene is a special form of wet gangrene caused by

gas forming clostridia.

Pathologic Calcification Pathologic calcification is deposition of calci-

um salts in tissues other than osteoid or enamel. It is of two types: dystrophic and metastatic cal-

cification. (1) Dystrophic calcification is characterized by deposition of calcium salts in dead and degen-

erated tissues with normal calcium metabolism and normal serum calcium level e.g. in caseous

granuloma, infarction, dead parasites, severe ath-erosclerosis, old scars and in some tumors

(papillary thyroid tumors, serous papillary ovari-an carcinoma, breast carcinoma). The mecha-

nism of calcium deposition in dystrophic calcifi-cation is increased binding of phosphates with

degenerated and dead tissues, which in turn bind to calcium forming calcium phosphate deposits.

(2) Metastatic calcification is caused by hypercalcae-mia which is encountered in : hyperparathyroid-

ism and pathologic bone destruction (myeloma, metastasis). The condition is reversible and

commonly affects kidney, stomach and lung due to change in pH at these sites.

CLINICAL RELEVANCE

The various retrogressive phenomena dis-

cussed in this chapter have important clinical applications, particularly in oncology, both diag-

nostic and therapeutic. The following is a short account of the main uses.

Diagnostic Role of Necrosis

Necrosis is helpful in: (1) differentiation be-tween caseous granuloma (TB) and non caseous

granulomas (sarcoidosis), (2) typing and grading of astrocytoma where necrosis is a feature of

glioblastoma, and (3) necrosis has an essential diagnostic criterion in some soft tissue sarcomas

as leiomyosarcoma and GIST. Grading of Therapy Effect

Histopathological grading of neoadjuvant chemotherapy effect in resected specimens is

usually applied in patients with osteosarcoma or breast carcinoma. In osteosarcoma, a 3-tiered

grading system is used (Picci et al, 1985) based on the extent of tumor necrosis. Thus grade I.

El-Bolkainy Surgical Pathology

69 Cell Degeneration and Death

<50% necrosis, Grade II. 50 – 80% necrosis, and grade III. > 80% necrosis, indicating a good

therapeutic response. In breast cancer, a 5-tiered grading system is used (Ogston et al, 2003) which

depends on quantitation of residual tumor tissue after therapy. Thus, grade I shows no tumor cell

loss (a poor response), grade II minor cell loss (<30%), grade III moderate cell loss (30-90%),

grade IV marked cell loss (only microscopic re-sidual tumor cell) and grade V 100% cell loss, no

viable tumor cells, denoting complete therapy response.

Also, therapy effect is graded according to percent of necrosis in other tumors nephroblas-

toma, germ cell tumors and the primitive neu-roectodermal tumors (PNET/Ewing‟s).

Prediction of Survival

Post chemotherapy tumor necrosis is a power-ful predictor of survival in patients with skeletal

osteosarcoma and the primitive neuroectodermal tumors Ewing‟s/PNET. Data are more conflict-

ing regarding the prognostic significance of ne-crosis in other soft tissue sarcomas. This is relat-

ed in part to the greater heterogeneity of soft tissue subtypes and to the inherent necrosis asso-

ciated with high-grade sarcomas unrelated to therapy effect. Therapy response is graded based

on percentage of necrosis in Ewing‟s/PNET and percentage of acellular osteoid in osteosarcoma.

Tumors with at 95% or more necrosis have a superior prognosis.

Guide to Therapy

Necrosis is a guide to therapy; (1) poor thera-py response in Ewing‟s is indicative of postop-

erative radiotherapy, (2) complete therapy re-sponse in low risk nephroblastoma patients

(good responders; 100% necrosis), is indicative of no postoperative chemotherapy and (3) com-

plete therapy response in germ cell tumors (100% necrosis), is indicative of no postopera-

tive chemotherapy.

Apoptosis Targeted Therapy

Both chemotherapy and radiotherapy kill can-cer cells by apoptosis. Accordingly, the aim of

targeted therapy in this case is to enhance apop-tosis in the tumor. This is accomplished by the

following different strategies: 1) to restore wild p53 in tumor through gene therapy hence, re-

storing normal p53 apoptotic action, 2) targeting mutated p53 in tumor cells by introducing a ge-

netically engineered adenovirus, leading to selec-tive destruction of tumor cells, 3) caspase–based

targeted therapy to activate these apoptosis in-ducing enzymes and 4) targeting the antiapoptot-

ic gene Bcl-2, through silencing its expression and 5) inhibition of expression of the prolifera-

tion promoting gene (survivin). These approach-es are currently under trial in patients with leuke-

mia, hepatocellular carcinoma, small cell lung cancer, lymphoma and melanoma.

Arterial Embolization

The rationale behind embolization therapy is to occlude the feeding vessel of a tumor, hence,

induce its necrosis with minimal harmful effect on surrounding normal cells. Microspheres of

microscopic size (1 nm to 1 mm) made of glass or resin are used as emboli. To enhance their

effect, microspheres may contain a chemothera-peutic agent (chemoembolization) or radioactive

mat e r i a l suc h as y t t r i um – 9 0 (radioembolization). Palliative arterial emboliza-

tion is used in hepatic, head and neck, as well as brain tumors. A favourable response rate was

reported in about 34% of cases.

REFERENCES

Archana M, Bastian, Yogesh TL, Kumaraswamy KL: Various methods available for detection

of apoptotic cells- A review- Indian J Cancer. Date of Web Publication 23- Sep-2013

Kroemer G, Galluzzi L, Vandenabeele P,

Abrams J, Alnemri, ES, Baehrecke EH et al: Classification of cell death: Recommendations

of the Nomenclature Committee on Cell Death (NCCD) 2009. Cell Death and Differ.

16 (1); 3-11, 2009

Mohan H: Cell Injury, Cellular Adaptations and

Cellular Ageing, Chapter 2 in Textbook of Pathology, 7th ed. The Health Sciences Pub-

lishers. New Delhi, 2015

Ogston KN, Miller ID and Payne: A new histo-

logical grading system to assess response of breast cancer to primary chemotherapy.

Breast, 12: 320-327, 2003

Picci P, Bacci G and Campanacci: Histologic evaluation of necrosis in osteosarcoma induced

by chemotherapy, regional mapping of viable and non-viable tumor. Cancer, 56: 1515-1521,

1985

Robbins and Cotran: Cellular Responses to Stress

and Toxic Insults: Adaptation, Injury, and

70

Death, Chapter 2, in Pathologic Basis of Dis-ease, 9th ed. Elsevier Saunders, 2015

Saadat YR, Saeidi N, Vahed SZ, Barzegari A, and Barar J: An update to DNA ladder assay

for apoptosis detection. Bioimpacts. 5 (1): 25-28, 2015

Wong R SY: Apoptosis in cancer: from patho-genesis to treatment. Journal of Experimental

and Clinical Cancer Research. 30:87, 2011.

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