A genome‐wide si RNA screen for regulators of tumor suppressor p53 activity in human non‐small cell lung cancer cells identifies components of the RNA splicing machinery as targets for anticancer treatment

Reinstating wild‐type tumor suppressor p53 activity could be a valuable option for the treatment of cancer. To contribute to development of new treatment options for non‐small cell lung cancer ( NSCLC ), we performed genome‐wide si RNA screens for determinants of p53 activity in NSCLC cells. We identified many genes not previously known to be involved in regulating p53 activity. Silencing p53 pathway inhibitor genes was associated with loss of cell viability. The largest functional gene cluster influencing p53 activity was mRNA splicing. Prominent p53 activation was observed upon silencing of specific spliceosome components, rather than by general inhibition of the spliceosome. Ten genes were validated as inhibitors of p53 activity in multiple NSCLC cell lines: genes encoding the Ras pathway activator SOS 1, the zinc finger protein TSHZ 3, the mitochondrial membrane protein COX 16, and the spliceosome components SNRPD 3, SF 3A3, SF 3B1, SF 3B6, XAB 2, CWC 22, and HNRNPL . Silencing these genes generally increased p53 levels, with distinct effects on CDKN 1A expression, induction of cell cycle arrest and cell death. Silencing spliceosome components was associated with alternative splicing of MDM 4 mRNA , which could contribute to activation of p53. In addition, silencing splice factors was particularly effective in killing NSCLC cells, albeit in a p53‐independent manner. Interestingly, silencing SNRPD 3 and SF 3A3 exerted much stronger cytotoxicity to NSCLC cells than to lung fibroblasts, suggesting that these genes could represent useful therapeutic targets.