What are the causes of cancer?

(N/A) The transformation of normal cells into cancerous neoplastic cells can be induced by physical, chemical, and biological agents.
Cancer-causing agents are known as $Carcinogens$.
$1$. Physical agents: Ionizing radiations like $X$-rays and $\gamma$ rays, and non-ionizing radiations like $UV$ rays cause $DNA$ damage, leading to neoplastic transformation.
$2$. Chemical agents: Chemical carcinogens present in tobacco smoke are identified as a major cause of lung cancer.
$3$. Biological agents: Cancer-causing viruses, known as oncogenic viruses, possess genes called viral oncogenes. Additionally, normal cells contain genes called cellular oncogenes $(c-onc)$ or proto-oncogenes, which, when activated under certain conditions, lead to the oncogenic transformation of cells.