What is the relationship between environmental factors and cancer?
Environment factors like UV rays, X rays, EtBr, aflatoxins etc causes mutations in DNA.
such mutated cells undergo apoptosis and are killed
Incase mutated cells continue to divide in an uncontrolled manner they can generate tumor.
there are various check points in cell cycle to stop the division of damaged cell.
beside this there are some inactivated oncogenes in human body if they get mutated they can also lead to formation of tumor