The past few decades have witnessed scientists gaining a considerable understanding of the molecular pathogenesis of human diseases, especially of cancer. Studies of the molecular basis of carcinogenesis have led to the realization that cancer is fundamentally a disease of genetic alterations. The multiple genetic changes in cancer are predominantly the result of accumulating mutations that have occurred in the genome over time. These genetic changes lead to the production of gene products with upreguated, repressed, or loss of function, which in turn produce aberrant signal transduction pathways and dysregulated cellular functions. The bulk of evidence demonstrates that dysregulated signal transduction pathways promote malignant transformation and support the formation, maintenance and progression of tumors.