RB1 and retinoblastoma: Accordingly, in various tumors (retinoblastoma, bladder, breast, colorectal and small cell lung carcinoma (SCLC) tumors), γtubulin and RB1 moderate each other’s expression, and in the absence of γtubulin and RB1, the uncontrolled transcriptional activity of E2Fs upregulates apoptotic genes, causing cell death [88,108].