Previous studies have revealed the genetic backgrounds of certain types of cancers, for example, the MSH2 gene in familial nonpolyposis colon cancer, the BRCA gene in familial breast cancer, the APC gene in colorectal cancer, and the RB gene in retinoblastoma (Golabchi et al., 2018; Aghabozorgi et al., 2019; Tamura et al., 2019; Venkitaraman, 2019). Here, RB1 is linked to colorectal cancer.