Overall, carcinogenesis involves
Full malignant transformation usually requires the cooperative action of multiple oncogenes and the loss of tumor suppressors. A single oncogene is rarely sufficient because cells possess multiple barriers—apoptosis, senescence, DNA-damage checkpoints—that must be overcome. Classic experiments demonstrated that Ras and Myc together bypass these barriers more effectively than either alone, illustrating the multi-hit nature of carcinogenesis.
Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)
