Combination Therapy with PIK3R3-siRNA and EGFR-TKI Erlotinib Synergistically Suppresses Glioblastoma Cell Growth In Vitro

BACKGROUND: Up-regulation of PIK3R3 (Phosphoinositide-3-Kinase Regulatory Subunit 3), the regulatory subunit of PI3K is correlated with the drug resistance of the glioblastoma cells. In the present study, the effect of PIK3R3 siRNA on erlotinib sensitivity of the U373-MG glioblastoma cells was explored. METHODS: After PIK3R3 siRNA transfection, the expression of PIK3R3 mRNA was measured using RT-qPCR. Trypan blue exclusion assay was used to explore the effect of PIK3R3 siRNA on cell proliferation. The effects of PIK3R3 siRNA and erlotinib, alone and in combination, on cell survival and apoptosis were measured using MTT assay and ELISA cell death assay, respectively. RESULTS: Our data showed that PIK3R3 siRNA markedly suppressed the expression of PIK3R3 in a time dependent way, inhibited the proliferation of the U373-MG cells and triggered apoptosis (p <0.05, relative to blank control). Pretreatment with PIK3R3 siRNA synergistically decreased the cell survival rate and lowered the IC(50) of erlotinib. Moreover, PIK3R3 siRNA markedly enhanced the apoptotic effect of erlotinib. CONCLUSIONS: Our data propose that suppression of PIK3R3 can effectively triggers apoptosis and enhances the sensitivity of the glioblastoma cells to EGFR-TKI erlotinib. Thus, PIK3R3 can be a potential therapeutic target in glioblastoma patients.