Explore The Anti-tumor Mechanism Of PI3Kα Inhibitor BYL719 Against Gastric Cancer Cells

Gastric cancer is one of the most deadliest diseases among cancer which holds the third and second position in China regarding on incidence and morality.However,surgical resection combined with chemotherapy and radiotherapy remain the main treatment of gastric cancer.The targets of approved anti-gastric cancer agents only include HER-2,VEGFR and PD-1,targeting which shows limited therapeutic benefit in part of gastric cancer patients.The above scenario indicates that it is urgent to develop more targeted drugs for gastric cancer treatment.The PI3K signaling pathway is abnormally activated in gastric cancers,which involved in the tumorigenesis and progression of gastric cancer.Importantly,PIK3CA encoding the catalytic subunit of PI3Kαmutates in 7-25%gastric cancer patients.In addition,the activation of PI3K signaling pathway facilitates the resistance of gastric cancer patients to existing drugs.It has also been reported that inhibiting PI3K in vitro has anti-gastric cancer effect.Therefore,PI3Kαis the potential target for treating gastric cancer.BYL719 is a selective PI3Kαinhibitor that reduces the on-target adverse reactions of pan PI3K inhibitors.However,the reported data in vitro and vivo showed that the PIK3CA mutation alone is not enough to predict the anti-tumor activity of PI3K inhibitors.Therefore,it is necessary to explore biomarkers that indicate or predict the anti-tumor activity of PI3Kαinhibitors.Based on the existing reports,this study firstly evaluated the anti-gastric cancer effect of BYL719 at the gastric cancer cellular and animal levels.Secondly,we explored the biomarkers which can indicate or predict the anti-gastric cancer effect of BYL719 by cellular biology and molecular biology techniques.First of all,the SRB results showed that BYL719 differentially inhibited the proliferation of various gastric cancer cells.The GI₅₀ values of BYL719 against sensitive gastric cancer cells AGS,NCI-N87 were at nanomole level.While,the GI₅₀value of BYL719 against resistance gastric cancer cells SGC-7901 was greater than10μM.Western Blot results showed that BYL719 could reduce the phosphorylation levels of Akt and S6,which are the vital proteins in PI3K/AKT/mTOR signaling pathway,in both sensitive and resistant gastric cancer cells.Then,we evaluated the anti-tumor effect of BYL719 in gastric cancer cell line-derived xenograft models.The results showed that BYL719 could inhibit NCI-N87 cells derived xenograft tumors growth in dose-dependent manner.While the SGC-7901 cells derived xenograft tumors were resistant to BYL719.Western Blot results showed that BYL719 reactivated the phosphorylation levels of AKT and S6 in NCI-N87 cells derived xenograft tumors after a long term treatment,but had no effect on the phosphorylation levels of AKT and S6in SGC-7901 cells derived xenograft tumors.In conclusion,PI3Kαinhibitor BYL719can significantly inhibit the proliferation of sensitive gastric cancer cells at both cellular and animal levels.In order to further explore the molecular mechanism mediating the sensitivity of BYL719 in gastric cancer.We first used the si RNAs specifically to p110αand p110βrespectively to verify the dependence of different gastric cancer cells on PI3Kα.We found that down-regulation p110αcould inhibit the proliferation of AGS cells effectively,but had no significant inhibitory effect on the proliferation of SGC-7901cells.The decreased p110βexpression had no effect on the proliferation of AGS and SGC-7901 cells.These results indicated that the proliferation of AGS depended on PI3Kα.Then,the RNA-seq technique was used to analyze the transcriptomics differences of NCI-N87 and SGC-7901 cells after BYL719 treatment.We found that PIK3IP1 was markedly up-regulated in NCI-N87 cells.q RT-PCR and Western Blot experiments further confirmed that BYL719 could up-regulate PIK3IP1 in sensitive gastric cancer cells.In order to further investigate the role of PIK3IP1 in the anti-proliferative activity of BYL719.sh RNAs were used to decrease the expression of PIK3IP1.Reduced PIK3IP1 can partially antagonized the anti-proliferative effects of BYL719 in AGS cells.These results suggested that the up-regulation of PIK3IP1mediated the sensitivity of gastric cancer cells to BYL719.In summary,we found BYL719 markedly inhibits the proliferation of some gastric cancer cells at the cellular and animal levels.Meanwhile,this study first found that the up-regulation of PIK3IP1 mediating the sensitivity of different gastric cancer cells to BYL719.These findings provide valuable theoretical and experimental proof for targeting PI3Kαin the treatment of gastric cancer.