Evaluation Of Anti-tumor Activity Of Dual PI3K-mTOR Inhibitor And Preliminary Study Of Its Mechanism

The PI3K-AKT-mTOR signaling pathway regulates the processes of survival,growth,proliferation,differentiation,autophagy and apoptosis in cells.Hence it plays a vital role in the life course of cells.It has been found that dysregulation and mutation of PI3K-AKT-mTOR signaling pathway occur in many cancer patients.Thus PI3K-AKT-mTOR signaling pathway has extremely close relationship with tumor development and can be used as an anti-tumor target.But so far,only the pan-PI3K inhibitor Copanlisib and the isoform-specific PI3K inhibitor Idelalisib have been successfully used in clinics.However,both drugs have certain defects.Therefore,the development of dual PI3K-mTOR inhibitors with better clinical effects and lower toxic and side effects has important application value.In this study,a series of PO compounds,potential inhibitors of PI3K-mTOR pathway with novel structure,were evaluated at enzyme level,cellular level and animal level.Besides,the pharmacokinetics and pharmacokinetic properties were also analyzed.the compound with the best druggability s were selected.Then,the possible mechanism underlying its anti-tumor effect was preliminarily explored at the molecular level.The results show that the selected dual PI3K-mTOR inhibitor PO-1023?hereinafter referred to as PO-23?can significantly inhibit the activity of four PI3K isoforms and mTOR kinase.Besides,it has good kinase selectivity,excellent anti-tumor activity in vivo and in vitro,moderate pharmacokinetic characteristics and safety.At the kinase level,PO-23 inhibited PI3K?,?,?and?isoforms and mTOR with IC₅₀s of 0.2 nM,0.58 nM,1.20 nM,0.5 nM and 21 nM,respectively.At the cellular level,compound PO-23 can reduce the phosphorylation levels of AKT and p70S6K in HCT116 and HT29 cellsin time-and dose-dependent manner.It has a good inhibitory effect in a variety of tumor cells with IC₅₀s in the range of 5 nM-1.93?M.It has been found that tumor cells with abnormal PI3K-AKT-mTOR signaling pathway or its upstream and downstream signaling molecules were more sensitive to PO-23.Meanwhile PO-23 inhibited the proliferation of normal cells HUVEC with an IC₅₀0 of 15.53?M,indicating that the compound might have good safety.In nude mice xenograft models of HCT116 and HT29 cells,compound PO-23 exhibited good antitumor activity in vivo,with tumor inhibition rate of more than 60%,which was comparable to the marketed drug Copanlisib.However,PO-23 caused some kind of liver toxicity.This study demonstrates that compound PO-23 can reduce the phosphorylation levels of AKT and p70S6K by inhibiting the activity of PI3K and mTOR in HCT116and HT29 cells.Furthermore,we found that PO-23 showed different effects in different cells:proapoptotic in HCT116 cells while inducing autophagy in SJSA-1cells.Why compound PO-23 induced different effects and some kinds of tumor cells are more sensitive than other cells need further investigation.In summary,the efficacy of compound PO-23 at the molecular,cellular,and animal levels,and preliminary tests on its pharmacokinetic characteristics,safety,and molecular mechanism were measured in this project.The results confirmed that the compound has certain druggability.Modification of this compound might produce a new drug candidate for cancer treatment,which lay a preliminary foundation for the development of new anti-cancer drug targeted on PI3K-mTOR pathway.