Chemicals and tumors

Tumorigenesis is driven usually by non-lethal genetic alterations such as malfunctioning regulatory systems; mainly by inactivating suppressor genes or activating proto-oncogenes or malfunctioning of apoptatic system or decresed activity of the DNA repair system. Several chemicals induces mutations in the regulatory genes forces the cell for continous divisions increasing the chance of accumulation of further mutations. Chemicals, inducing mutations (mutagens) increase the rate of tumor occurrence, are carcinogens.