RB1 and small cell lung carcinoma: Intriguingly, in various tumors (i.e., retinoblastoma and bladder, breast, colorectal, and small cell lung carcinomas [SCLCs]), γ-tubulin and RB1 moderate each other’s expression, and, in the absence of γ-tubulin and RB1, the uncontrolled transcriptional activities of E2Fs upregulate apoptotic genes that cause cell death.13,14 In some tumor types, the RB1 gene is deleted or carries somatic mutations.