The Dual PI3K/mTOR Inhibitor NVP-BEZ235 Induces Tumor Regression in a Genetically Engineered Mouse Model of PIK3CA Wild-Type Colorectal Cancer

Jatin Roper,Erin M Coffee,Wei Chen,Eric S Martin,Kenneth E Hung,Roderick T Bronson,Peng-Chieh Chen,Mark J Sinnamon,Michael P Richardson,Larissa Georgeon Richard,Lydia Lee,Wei Vivian Wang,Alfons Navarro

doi:10.1371/journal.pone.0025132

Abstract

PurposeTo examine the in vitro and in vivo efficacy of the dual PI3K/mTOR inhibitor NVP-BEZ235 in treatment of PIK3CA wild-type colorectal cancer (CRC).Experimental Design PIK3CA mutant and wild-type human CRC cell lines were treated in vitro with NVP-BEZ235, and the resulting effects on proliferation, apoptosis, and signaling were assessed. Colonic tumors from a genetically engineered mouse (GEM) model for sporadic wild-type PIK3CA CRC were treated in vivo with NVP-BEZ235. The resulting effects on macroscopic tumor growth/regression, proliferation, apoptosis, angiogenesis, and signaling were examined.Results In vitro treatment of CRC cell lines with NVP-BEZ235 resulted in transient PI3K blockade, sustained decreases in mTORC1/mTORC2 signaling, and a corresponding decrease in cell viability (median IC50 = 9.0–14.3 nM). Similar effects were seen in paired isogenic CRC cell lines that differed only in the presence or absence of an activating PIK3CA mutant allele. In vivo treatment of colonic tumor-bearing mice with NVP-BEZ235 resulted in transient PI3K inhibition and sustained blockade of mTORC1/mTORC2 signaling. Longitudinal tumor surveillance by optical colonoscopy demonstrated a 97% increase in tumor size in control mice (p = 0.01) vs. a 43% decrease (p = 0.008) in treated mice. Ex vivo analysis of the NVP-BEZ235-treated tumors demonstrated a 56% decrease in proliferation (p = 0.003), no effects on apoptosis, and a 75% reduction in angiogenesis (p = 0.013).ConclusionsThese studies provide the preclinical rationale for studies examining the efficacy of the dual PI3K/mTOR inhibitor NVP-BEZ235 in treatment of PIK3CA wild-type CRC.

Highlights

In 2011, colorectal cancer (CRC) will continue to be the third most common cause of cancer-related mortality in the U.S [1]
In vivo treatment of colonic tumor-bearing mice with NVP-BEZ235 resulted in transient phosphatidylinositol 3-kinase (PI3K) inhibition and sustained blockade of mTOR complex 1 (mTORC1)/mTOR complex 2 (mTORC2) signaling
Ex vivo analysis of the NVP-BEZ235treated tumors demonstrated a 56% decrease in proliferation (p = 0.003), no effects on apoptosis, and a 75% reduction in angiogenesis (p = 0.013). These studies provide the preclinical rationale for studies examining the efficacy of the dual PI3K/Mammalian target of rapamycin (mTOR) inhibitor NVP-BEZ235 in treatment of PIK3CA wild-type CRC

Summary

Introduction

In 2011, colorectal cancer (CRC) will continue to be the third most common cause of cancer-related mortality in the U.S [1]. MTOR binds regulatory associated protein of mTOR (Raptor) and mammalian LST8/G-protein b-subunit like protein (mLST8/ GbL) to form the mTOR complex 1 (mTORC1), which promotes translation through phosphorylation of p70 S6 kinase (S6K), S6 ribosomal protein (S6), and eukaryotic initiation factor 4E binding protein 1(4E-BP1). Point mutations in PIK3CA cluster at two hotspots: E545K in the helical domain (exon 9) and H1047R in the catalytic kinase domain (exon 20). These mutations increase p110a activity and promote CRC cell growth, invasion, and migration in vitro via activation of the PI3K pathway [7]. AKT is a critical downstream effector of the PI3K pathway and promotes cell growth and survival via a number of mechanisms, including phosphorylation of TSC2, which results in mTORC1 activation [5]. Full activation of AKT is achieved after phosphorylation at Thr308 and Ser473 by PDK1 and mTORC2, respectively [5,8,9,10,11]

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Results

Conclusion