RB1 and glioblastoma: Loss of the RB1 gene coupled with a loss in homologous recombination DNA repair pathway genes in other cancers, particularly high-grade ovarian carcinoma, has been associated with increased CD8+ tumor-infiltrating lymphocytes (TILs), PFS, and OS.29 In GBM, an increase in TILs has been associated with RB1 mutations.30 Additionally, it has been suggested that RB1 mutations provoke replication stress in tumor cells, leading to DNA damage and activation of the innate immune system.