What causes some cancer cells to avoid going through apoptosis and avoid self-destruction?

Cancer cells can avoid apoptosis, or programmed cell death, through several mechanisms:

1. Mutation in Apoptosis-Regulating Genes: Some cancer cells have mutations in the genes that regulate apoptosis. For example, the p53 gene, often referred to as the "guardian of the genome," is responsible for detecting DNA damage and initiating apoptosis. If this gene is mutated, it may not function properly, allowing damaged cells to survive and proliferate.

2. Overexpression of Anti-Apoptotic Proteins: Cancer cells can also overexpress anti-apoptotic proteins, such as Bcl-2 and Bcl-xL. These proteins inhibit the release of cytochrome c from the mitochondria, a key step in the apoptotic pathway, thereby preventing cell death.

3. Downregulation of Pro-Apoptotic Proteins: Conversely, cancer cells may downregulate or decrease the production of pro-apoptotic proteins, such as Bax and Bak. This imbalance between anti- and pro-apoptotic proteins can tip the scale in favor of cell survival.

4. Activation of Survival Pathways: Cancer cells can activate survival pathways, such as the PI3K/Akt pathway, which promotes cell growth and survival and inhibits apoptosis.

5. Evasion of Immune Surveillance: Cancer cells can evade the immune system, which normally recognizes and destroys abnormal cells. They can do this by downregulating the expression of proteins that make them recognizable to immune cells or by secreting immunosuppressive molecules.

6. Alteration in Death Receptors: Death receptors on the cell surface can trigger apoptosis when bound by specific ligands. Some cancer cells can avoid apoptosis by downregulating these receptors or by increasing the expression of decoy receptors that bind the ligands without triggering cell death.

These mechanisms allow cancer cells to evade apoptosis and continue to grow and divide, contributing to tumor progression.