Apoptosis and response to

chemotherapy

Content

• Apoptosis – what is it?

• Apoptosis vs necrosis

• Radiation vs chemotherapy

• Apoptosis vs mitosis

• Tumour hijacking apoptosis

• Therapeutic strategies

Apoptosis

“Apoptosis is a cell suicide mechanism

that enables metazoans to control cell

number in tissues and to eliminate

individual cells that threaten the

animal’s survival”

Ashkenazi, Science 1998

Inhibition of apoptosis underlies many

carcinogenic processes

• Growth in the absence of normal growth

signals

• Growth in the presence of growth

inhibitory factors

• Metastases

• Chemoresistance

• Promotion of angiogenesis

FADD

TNFR1

NF

TRADD

FADD TRAF-2

RIP

TNFα

C-FLIP

Caspases 3, 6, 7

SURVIVAL

SIGNALS

Caspase 9

FAS

FAS-L

NUCLEUS

tBID/BAX

Caspase 8

IAPS

ENDO G & AIF

UV

CYTOKINE DEPRIVATION

STEROID

Bcl-2

BH3 only

ROS

DISC

ATR/ATM/DNA PK

STRESS /

DNA DAMAGE

CHEMOTHERAPY

p53

SMAC/DIABLO

JNK

jBID

CTL/NK

cell

Granzymes APOPTOSOME

3 main apoptotic pathways

•Extrinsic

•Intrinsic

•Interaction between activated CTL

receptors and MHC-class 1 molecules

SENSITIZERS

PRO-APOPTOTIC p53, Smac/Diablo, Omi/HtrA2,

Bik, Bim, Bad, Noxa, Puma, Noxa, Bmf,

Bid, Bax, Bak, JNK, APAF-1,

cytochrome c

ANTI-APOPTOTIC Bcl-2, BclXL, Bcl-w, A1, Mcl-1, IAPs,

Heat shock proteins

STIMULATORS

Fas, TNF, TGF, IFN, ROS, CTL, viruses, steroids, staurosporin,

hypoxia, telomere erosion, X-rays, UV, DNA damage,

hormones, Ca2+ flux

PROCESSORS DFF40, Endo G, DNase II, AIF, Proteases

FADD

TNFR1

NF

TRADD

FADD TRAF-2

RIP

TNFα

C-FLIP

Caspases 3, 6, 7

SURVIVAL

SIGNALS

Caspase 9

FAS

FAS-L

NUCLEUS

tBID/BAX

Caspase 8

IAPS

ENDO G & AIF

UV

CYTOKINE DEPRIVATION

STEROID

Bcl-2

BH3 only

ROS

DISC

ATR/ATM/DNA PK

STRESS /

DNA DAMAGE

p53

SMAC/DIABLO

JNK

jBID

CTL/NK

cell

Granzymes APOPTOSOME

BH3 only “Trigger” proteins Bik, Bim, Bid, Bmf, Puma, Noxa, Bad

Anti-apoptotic “Arbitrator” proteins Bcl-2, BclXL, Bcl-w, A1, Mcl-1

“Killer” proteins Bax and Bak

Bcl-2 gene family

Activation of initiator

caspases in apoptosome or DISC

Activation of executioner

caspases by active

initiator caspases

IAPS

Smac/Diablo

Demolition of the cell

P

P

P

P

L

S L

L

L

L

L

L

L

S S

S

S

S

S S

Critical role of caspases

Necrosis vs Apoptosis

Taken from Cytometry 1997

Cancer therapies can induce

apoptosis

• Irradiation

DNA strand breaks

Free radical formation

Ceramide (independent of DNA damage)

• Chemotherapy

DNA crosslinks

toxic effects

death receptor upregulation

Successful chemotherapy?

Drug

cure

+

Stem cells

A tumour will not evolve if its stem cells are

prevented from continued cell proliferation

Cell death after radiation

• Apoptosis

• Mitotic catastrophe

• Terminal growth arrest (senescence)

Tumours can hijack

apoptosis

regulatory mechanisms in normal cells

to guard against inadvertent apoptosis

mechanisms hijacked by tumour cells

• Downregulation of Fas

•Prevalance of Fas-L expressing tumour cells Fas TIL killed by Fas-L expressing tumour cells

? Downregulation of MHC class 1 molecules on tumour cells

Successful chemotherapy

Drug

Stem cell

regrowth

Oncogenes

TSG

Controlled destruction of certain cells

Pro apoptotic

Anti-apoptotic

MMC Response Pathways

Mitomycin-C +

DNA repair

No drug-target interaction

No effect

DNA mutation

Apoptosis

p53

Bcl2

Cellular response

Fas

Environmental factors

Immunostaining as an adjunct in

pathology

• Antibodies raised against biomarkers

• Biomarkers can be localised in tissue

sections

Mitochondrial role

Bcl-2

p53

Bax Bak

Pore formation

Bcl-2 associated with cisplatin resistance Bcl-2 :Bax ratios predictive

BH3 mimetics

• Some function as death agonists directly

mimicking the activity of tBid

• Others have been synthesized on the

premise that they will inhibit the anti-

apoptotic function of Bcl-2 and Bcl-xL.

TRAIL ? Therapeutic agent

• TRAIL is tumour necrosis factor–related

apoptosis-inducing ligand

• TRAIL induces apoptosis independently of

p53

• TRAIL demonstrates preferential

apoptosis induction in tumour cells while

sparing most normal cells

Carcinogen

Ionising radiation Mutagen

DNA damage

p53 activated

DNA repair BAX

apoptosis Normal cell

success fail

Bcl-2

Jia Li, Liau 2007

DNA repair as a target

DNA repair

Carcinogen

Ionising radiation Mutagen

DNA damage

p53 activated

BAX

apoptosis Tumour cell

Bcl-2

Jia Li, Liau 2007

?????

Current Strategies

Drug Target

CCDO FLIP

PRIMA-1 Mutant p53

Embelin IAPs

Genasense Bcl-2

Gossypol Bcl-2

HGS-ERT1 TRAIL

BH3 mimetics Anti-apoptotic proteins

Bortezomib (VELCADE) 26S proteosome

MKT-007 mitochondria

IRESSA growth factor receptor

TNF α

PROLIFERATION/

SURVIVAL

INFLAMMATION APOPTOSIS

NF-кB

ONCOGENIC RAS Bcl-2

p53 JNK