SIRT3 deacetylates and promotes degradation of P53 in PTEN-defective non-small cell lung cancer.

PURPOSE: In non-small cell lung cancer (NSCLC), success of targeted therapy has promoted researches explicitly orientated based on genetic background. Although PTEN deficiency is common in NSCLC, carcinogenesis about such genetic type has not been fully explored. Here, we have found that classical tumor suppressor P53 could be modulated by deacetylase sirtuin-3 (SIRT3) depending on the PTEN condition in NSCLC, which may be a novel breakpoint for handling PTEN deficiency NSCLC.
METHODS: First, we examined SIRT3 and P53 expression files in PTEN-deficient NSCLC clinical samples and investigated their correlation. Second, we built SIRT3 high or low expression models in different PTEN conditions by plasmid overexpression or si-RNA interference in NSCLC cell lines and explored the effect of SIRT3 upon P53. Furthermore, we investigated the influence of SIRT3 upon the ubiquitin-proteasome dependent degradation pathway of P53 in PTEN-deficient NSCLC cell lines. Finally, we probed into the deacetylation modification of P53 via SIRT3.
RESULTS: We found that SIRT3 expression was strongly positive and P53 expression was almost negative in PTEN-deficient NSCLC clinical samples. Further, we demonstrated that SIRT3 promoted degradation of P53 in PTEN-deficient NSCLC cell lines via the ubiquitin-proteasome pathway. Finally, we demonstrated that SIRT3 could deacetylate P53 at lysines 320 and 382, which may account for the observed degradation of P53 in PTEN-deficient tumor cells.
CONCLUSIONS: We have identified a novel mechanism by which P53 was inactivated via SIRT3 in PTEN-deficient cells. This may shed light on the mechanisms underlying the malignancy of PTEN-deficient NSCLC.