Tumour Pathology 4 and 5

Question 1

Mitosis

Answer 1

Mechanism of cellular replication. A diploid cell becomes 2 diploid cells.

Question 2

Cell cycle

Answer 2

The time interval between mitotic divisions.
G2 = preparation for mitosis and cell growth.
M = mitosis and cell division
G1 = synthesis of components required for DNA synthesis and a checkpoint.
S = DNA synthesis.
G1, S and G2 are known as the interphase.
There are approximately 25 x 10^(6) cell divisions per second.

Question 3

Number of cells in body

Answer 3

Approximately 10^(13)

Question 4

Carcinogenesis

Answer 4

Caused by a mutation of genetic material that upsets the normal balance between proliferation and apoptosis. Only mutations in genes regulating cell division, apoptosis and DNA repair cause a cell to lose control of proliferation.

Question 5

Abnormal cell cycle

Answer 5

The primary defect in cancer is uncontrolled proliferation via cell cycle dysregulation

Question 6

Cell pathways disrupted

Answer 6

1. Cyclin D-pRb-E2F
2. p53
   - Virtually all cancers are dysregulated at G1-S because of mutation in one of four genes; Rb, CDK4, cyclin D, p16.

Question 7

Aetiological cancer agents

Answer 7

Chemicals, radiation, oncogenic viruses, age, inherited.

Question 8

How do aetiological agents cause abnormalities

Answer 8

The purine and pyramidine bases in DNA are critical cellular targets for damage by radiation and various oxidising and alkylating agents. Chemical carcinogens/active metabolites react with DNA to form adducts. Adduct formation at particular sites in DNA leads to the activation of oncogenes and suppression of tumour suppressor genes.

Question 9

Tumour formation

Answer 9

More than one mutation is necessary for carcinogenesis. All sporadic cancers harbour multiple genetic abberations and abnormalities which accumulate with time. Activation of several oncogenes and loss of 2 or more anti-oncogenes occurs in most cancers.

Question 10

Genetic changes in cancer

Answer 10

Mutations can be sporadic and/or inherited and they accumulate over time. Loss of cell cycle control leads to malignant transformation. Key regulators include; p16, cyclin D, CDK4 and Rb and are mutated in majority of cancers. Loss or mutation of p53 allows genetically damaged cells to proliferate forming malignant neoplasms.