It is not easy for a normal cell to become a cancer cell. The process is complex. Cancer cell will develop from a normal cell only when its DNA is damaged. DNA is in every cell and directs all the cell’s activities. Most of the time when DNA is damaged, either the cell dies or is able to repair the damaged DNA.
But if the damaged DNA cannot be repaired, it will result in a cancer cell. In a cancer cell, the damaged DNA (mutations) in particular genes may mean that a cell starts making too many proteins that triggers a cell to divide and at the same time the cell stops making those proteins that normally tell a cell to stop dividing. The result of such genetic alteration leads to abnormal proliferation of a single cell. Cell proliferation then leads to the outgrowth of a population of clonally derived tumor cells.
The first page or two of this review gives a short and concise overview as to how a cell can become cancerous, and why agents causing specific types of DNA damage can be the cancer cell's Achilles heel.
In studies of formation of carcinomas, the most common form of solid tumors in humans, tumors of epithelial tissue origin, it is common to characterize the changes in terms of drivers and processes that produce epithelial to mesenchymal transition. Here are some review articles.
Article The Epithelial-to-Mesenchymal Transition in Development and Cancer
Article Epithelial-Mesenchymal Transition in Cancer: A Historical Overview
Article The molecular mechanisms and therapeutic strategies of EMT i...