ESR1 and colorectal neoplasm: Observational and experimental studies have also suggested that sex hormones, particularly estrogen, may play a protective role in colorectal carcinogenesis either indirectly by reducing secondary bile acids and insulin-like growth factor-I (IGF- I) or directly by regulating cell growth in the colonic epithelium and inhibiting cell proliferation of colorectal tumors by binding to the estrogen receptor [4].