Cancer cells are rapidly dividing cells that no longer are controlled by the mechanisms listed above. Cancer cells can form tumors due to this unchecked growth. Cancers are caused by genetic mutations . Sometimes these mutations are found in the germline , and result in inherited cancers or a predisposition to cancer. Most often these mutations are found in somatic cells.
Somatic mutations accumulate over our lifetime.
Cancers are caused by multiple genetic mutations. Except in rare cases, cancer cells have accumulated a number of mutations. Look at figure 17.16 in Purves to follow the accumulation of multiple mutations in colon cancer . Proto-oncogenes include growth factors, growth factor receptors, and cyclins. Oncogenes are mutated forms of these genes that result in unregulated stimulation of cell division.