The PI3K subunits, P110\u03b1 and P110\u03b2 are potential targets for overcoming P-gp and BCRP-mediated MDR in cancer

Lei Zhang,Qianchao Wang,Chaohua Hu,Xiaoyun Li,Zhuo Chen,Zhe-Sheng Chen,Yidong Li,Wei Zhang,Zhuoxun Wu,Dan Liao

doi:10.1186/s12943-019-1112-1

Abstract

BackgroundPI3K/AKT is a vital signaling pathway in humans. Recently, several PI3K/AKT inhibitors were reported to have the ability to reverse cancer multidrug resistance (MDR); however, specific targets in the PI3K/AKT pathways and the mechanisms associated with MDR have not been found because many of the inhibitors have multiple targets within a large candidate protein pool. AKT activation is one presumed mechanism by which MDR develops during cancer treatment.MethodsThe effects of inhibiting PI3K 110α and 110β by BAY-1082439 treatment and CRISPR/Cas9 knockout were examined to determine the possible functions of BAY-1082439 and the roles of PI3K 110α and 110β in the reversal of MDR that is mediated by the downregulation of P-gp and BCRP. Inhibition of AKT with GSK-2110183 showed that the downregulation of P-gp and BCRP is independent of generalized AKT inactivation. Immunofluorescence, immunoprecipitation, MTT, flow cytometry and JC-1 staining analyses were conducted to study the reversal of MDR that is mediated by P-gp and BCRP in cancer cells. An ATPase assay and a structural analysis were also used to analyze the potential mechanisms by which BAY-1082439 specifically targets PI3K 110α and 110β and nonspecifically influences P-gp and BCRP.ResultsBy inhibiting the activation of the PI3K 110α and 110β catalytic subunits through both the administration of BAY-1082439 and the CRISPR/Cas9 deletion of Pik3ca and Pik3cb, the ATP-binding cassette transporters P-gp/ABCB1 and BCRP/ABCG2 were downregulated, thereby reestablishing the drug sensitivity of human epidermoid carcinoma and non-small cell lung cancer (NSCLC) MDR cells. Inhibition of AKT did not reverse the MDR mediated by P-gp or BCRP. The ABC family proteins and AKT may play MDR-enhancing roles independently.ConclusionsThe reversal of the dual functions of ABC-transporter-mediated and AKT-activation-enhanced MDR through the inhibition or knockout of PI3K 110α or 110β promises to improve current strategies based on combined drug treatments to overcome MDR challenges.

Highlights

In human tissues, the phosphoinositide 3-kinase (PI 3kinase, known as Phosphoinositide 3kinase (PI3K)) signaling pathway is a vital regulatory component involved in balancing metabolism, regulating a series of factors, and influencing cell survival and neuronal functions [1,2,3,4,5,6,7,8,9,10]
BAY-1082439 reversed the drug resistance mediated by overexpressed P-gp and BCRP in the multidrug resistance (MDR) cancer cells BAY-1082439 is a small-molecule that inhibits PI3K class I P110α, P110β, and mutated forms of P110α (Fig. 1a)
Compared to that of the parental cells, the cell viability of the KB-C2 and H460/MX20 cells was decreased, which indicated that inhibiting the PI3K 110α and 110β subunits with nontoxic or minimally toxic concentrations of BAY1082439 can potentially reverse the P-gp- or BCRP- mediated MDR in these cells, which express the drug-efflux transporters P-gp or BCRP, a primary characteristic that distinguishes them from their parent cells

Summary

Introduction

The phosphoinositide 3-kinase (PI 3kinase, known as PI3K) signaling pathway is a vital regulatory component involved in balancing metabolism, regulating a series of factors, and influencing cell survival and neuronal functions [1,2,3,4,5,6,7,8,9,10]. PI3Ks are vital components of the PI3K/AKT/mTOR pathways and are regulated by many factors (enhancers such as EGF, shh, IGF-1, insulin and CaM, and antagonists such as PTEN, GSK3β and HB9). They are critical to many functions related to AKT activation, such as cancer, chemoresistance, and longevity [14,15,16,17,18]. AKT activation is one presumed mechanism by which MDR develops during cancer treatment

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