What are proto-oncogenes, oncogenes, and tumor suppressor genes and what is their involvement in cancer?

Explain how epigenetic changes can contribute to tumorigenesis.

Metastasis occurs when cells from a primary tumor invade and colonize other tissues. Metastasis is a complex, multistep process. Tumor cells must lose adhesion with other tumor cells, invade local tissues and vessels, move through the circulation, leave the vessels, and finally, establish new colonies at distant sites. Tumor cells gain the ability to cross epithelial layers and migrate through tissues by mutations, although the nature of the mutations that drive metastasis is poorly understood. Mutations that block expression of the E-cadherin gene are thought to be an important step in metastasis. The absence of E-cadherin expression could affect metastasis by blocking cell adhesion directly, by releasing signaling proteins bound to the cytoplasmic domain of E-cadherin, or by both mechanisms. To better understand how loss of E-cadherin contributes to metastasis, scientists created two cell lines that differed in their expression of E-cadherin. One cell line was blocked for expression…

Why do mutations in genes that encode DNA-repair enzymes often produce a predisposition to cancer?