In SCLC tumors, the loss of Renitoblastoma 1 (RB1) gene expression has been correlated to 95% of tumors development, whereas mutations in the tumor protein p53 gene have been reported in 65% of SCLC cases [42].To a lesser extent, the inactivation of the methyltransferase lysine methyltransferase 2D gene (KMT2D has been observed in 8% of SCLC tumors and 17% of SCLC cell lines (e.g., NCI-H2171) [43]. Here, RB1 is linked to small cell lung carcinoma.