Index >>Viruses and Cancer >>Somatic Mutation Hypothesis

Somatic Mutation Hypothesis - According to this hypothesis cancer is the result of somatic mutations (i.e. mutations not involving germ cells), without viral infection occurring in a cell.
Such a mutation may alter the control mechanism of the cell, leading to unregulated division or cancer.
The mutations may involve the activation of normally repressed genes. This could take place by.
(i) Mutations in the repressed genes themselves, or

(ii) mutations that block the production of repressor proteins, thus unblocking inactive genes and making them active.
Most cancerous cells have abnormal chromosomal components.
Often there are different numbers of chromosomes in different cells of one tumour.

The evidence for chromosomal alteration as a cause of cancer does not look strong.
Sachs and his group have postulated hat cells contain effector (E) chromosomes which cause malignacy and suppressor (S) chromosomes which suppress malignancy.
Whether a cells is malignant or, not depends upon a balance in the number of E and S chromosomes.
It has been suggested that in the hamster karyotype chromosome 57 is the E chromosome, chromosome 73 the S chromosome for transformation and chromosome 72 the S chromosome for malignancy.