Cancer

Cancer is a multifactorial disease:

Cancer is multifactorial disease. Genetic, environmental, medical, and lifestyle factors interact together to produce a certain malignancy. Cancer genetic is a challenging area of research that is evolving aiming to understand the biology of cancer. This will expand our knowledge to characterize each malignancy, identify individuals at risk, and unlimited implications on cancer prevention and management.

Public awareness of risk factors, genetic susceptibility and familial predisposition is increasing recently. The revolutionary availability and easiness to reach medical information as well as consultation through the internet raised concerns among persons who have a relevant medical or family history. Identifying individuals and families at increased cancer risk s a very important issue in cancer prevention and management.

Molecular pathways to cancer involve alterations in the following genes:
 

1. Oncogene: (they cause cancer when they gain function).

• Proto-oncogene (oncogene precursor): these are normal cellular genes. Their mutation results in gain of function (c-onc) or overexpression. They code for proteins that regulate cell growth and differentiation. Examples of proto-oncogenes include Ras, Wnt, and Myc.
 

• Oncogene (v-onc): these are viruses' transduced oncogenes through an error prone process of the retroviral replication. The first oncogene discovered is src (pronounced sarc) discovered by Dr G. Steve Martin (the University of California, Berkeley) in 1970.

2. Tumor suppressor genes (they cause cancer when they lose function).

These genes contribute also to cell growth and or differentiation. They play also important roles in the apoptosis process and cell-to-cell adhesion. To the contrary, of oncogenes tumor suppressors contribute to cancer formation when their function is lost. Examples of tumor suppressor genes are Rb, p53 and its family of proteins p63 and p73.

The Bcl2 and p53 family of genes are examples of group of family of genes whose members may be oncogene or tumor suppressor.

3- DNA repair genes:

Normally during the cell cycle some errors occur in the DNA, these errors are corrected by the so-called Mismatch-repair genes MMR. Exposure to certain factors (like ionizing radiation) may result in DNA defects that cannot be repaired. For MMR genes to lose function, the two copies of the gene must be altered. When these errors accumulate together with the alteration in any of the genes mentioned above tumor formation occurs

Theory of cancer development:

Cancers are thought to develop passing from a nonmalignant precursor lesions into cancer ones through major three stages; initiation, promotion and progression.

Initiation is usually seen as irreversible changes that results from a single gene mutation.

During promotion, cells are more proliferative and form benign neoplasm like lesions that may be irreversible.

Cells from these lesions may evolve into a malignant one that enters the progression phase of uncontrolled self-replication and invasion.