APC and adenoma: CRC is a stepwise progression of premalignant lesions; approximately 70% of sporadic CRCs are initiated from adenomatous polyps via the adenoma–carcinoma sequence (Figure 2A), governed by mutation of the tumor-suppressor APC (adenomatous polyposis coli), followed by the acquisition of mutations in proto-oncogene KRAS (Kirsten rat sarcoma virus) and the tumor-suppressor P53 (tumor protein P53; transformation-related protein 53; TRP53), chromosomal, and microsatellite instability (MSI), in increasing adenomas and invasive adenocarcinomas.