Cell Cycle and Cancer

Cancer Terms

• Neoplasm – new, abnormal growth of cells• Benign – not cancerous• Malignant - cancerous• Cancer – cellular growth disorder that results

from the mutation of the genes that regulate the cell cycle

• Carcinogenesis – development of cancer

Characteristics of Cancer Cells• Table 9.2 (page 159)• Cancer cells– Lack differentiation, do not contribute to body– Have abnormal nuclei, enlarged, abnormal # of

chromosomes– No apoptosis– Form tumors, no contact inhibition, disorganized and

multilayered– Not encapsulated– Undergo metastasis and angiogenesis

• Telomeres – a region of repetitive DNA at the end of a chromosome, which protects the end of the chromosome from deterioration. Cancer cells have longer regions so they can continue to reproduce.

Prognosis (probable outcome)

1. Whether the tumor has invaded surrounding tissue

2. Whether there is lymph node involvement3. Whether there are metastatic tumors in

distant parts of the body

Proto-oncogenes• specify proteins that directly and indirectly promote the cell

cycle• Found at the end of a stimulatory pathway• A mutated proto-oncogene = oncogene

Tumor-suppressor genes

• At the start of inhibitory pathway• Directly or indirectly inhibit the cell cycle• When mutates, inhibitory proteins fail to be

active and cell cycle is unchecked.• Ex. P53, mutated mostly in human cancers,

works to turn on the expression of other genes who inhibit cell cycle and stimulates apoptosis.

oncogenes

• Cancer causing genes• Cause acceleration of the cell cycle by coding

for a faulty receptor protein or specify an abnormal protein product that stimulates the cell cycle to begin.

• Can bring about excess cyclin and excess inhibitors of p53 so that apoptosis does not occur.

• Ex. rasK, rasN, BRCA1