Cancer is caused by the complex interplay
between various non-genetic (carcinogens, tobacco, chemicals, radiations and
infectious organisms), and genetic factors (inherited mutations, hormones,
immune conditions and mutations that occur from metabolism).
These causal factors may act together, or in
sequence to initiate or promote carcinogenesis. At a molecular level, it starts with the activation
of oncogenes in the cells
leading to subsequent inactivation of tumor suppressor genes.
The genes involved in the development of
cancer can be grouped under two categories, viz. (i) Oncogenes and (ii) Tumor
suppressor genes (TSGs). Oncogenes are responsible for transforming normal
cells into their cancerous counterparts. Oncogenes are mutated form of
otherwise normal genes known as proto-oncogene. These proto-oncogenes carry out
critical functions like cell cycle regulation, and differentiation.
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