In vitro assessment of antitumor activities of the PI3K/mTOR inhibitor GSK2126458.

Alia Albawardi,Abdul-Kader Souid,Saeeda Almarzooqi,Mohamed Al Bashir,Muna Al Ayyan

doi:10.1186/s12935-014-0090-z

Abstract

BackgroundUp-regulation of the PI3K/mTOR (phosphatidylinositol-3′ kinase/mammalian target of rapamycin) signaling is common in carcinoma. Consistently, targeting these molecules has been shown to halt the growth of many tumors. The main purpose of this study was to develop surrogate biomarkers of the antitumor activity of PI3K/mTOR inhibitors.MethodsFragments from eight tumors were collected immediately after resection in ice-cold RPMI gassed with 95% O2 :5% CO2. Viability was determined by measuring tumor cellular respiration (mitochondrial O2 consumption). The specimens were incubated at 37°C with and without 50 nM GSK2126458 (a highly potent and selective inhibitor of PI3K/mTOR) for 90 min. The tissue was then processed for histology, measurement of intracellular caspase-3 activity (using the caspase-3 substrate N-acetyl-asp-glu-val-asp-7-amino-4-methylcoumarin), and immunohistochemical detection of the apoptotic biomarkers caspase-3, cytochrome C, and annexin A2.ResultsGSK2126458 induced morphologic changes in four tumors (two invasive ductal carcinomas, one invasive lobular carcinoma, and one ovarian dysgerminoma), intracellular caspase-3 activity in three tumors (two invasive ductal carcinomas and one poorly differentiated signet ring adenocarcinoma of gastric origin), and immunohistochemical evidence of apoptosis in at least four tumors (three invasive ductal carcinomas and one adenocarcinoma of gastric origin). Two tumors (ovarian serous carcinoma and moderately differentiated adenocarcinoma of colorectal origin) demonstrated no treatment effect.ConclusionThese preliminary results demonstrate the feasibility of using in vitro biomarkers for detecting antitumor activities of the rapidly emerging PI3K/mTOR inhibitors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12935-014-0090-z) contains supplementary material, which is available to authorized users.

Highlights

Up-regulation of the phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin 1/2 complexes (mTOR) signaling is common in carcinoma
GSK2126458, a highly potent and selective inhibitor of class I phosphoinositide 3-kinase (PI3K) and mammalian target of rapamycin 1/2 complexes [1,2], is in clinical trials for treatment of various solid tumors [3]. This agent targets the critical survival pathway PI3K/ PTEN/Akt/mTOR [4,5]. Inhibiting these signals has been shown to promote apoptosis in tumor cells and impair cellular bioenergetics [6,7]
The first tumor was invasive ductal carcinoma of the breast (Nottingham histological grade 3). It was positive for estrogen receptor (ER+), negative for progesterone receptor (PR-), expressed human epidermal growth factor receptor 2-neu (Her2-neu+), and had a Ki-67 proliferation index of 70%

Summary

Introduction

Up-regulation of the PI3K/mTOR (phosphatidylinositol-3′ kinase/mammalian target of rapamycin) signaling is common in carcinoma. GSK2126458, a highly potent and selective inhibitor of class I phosphoinositide 3-kinase (PI3K) and mammalian target of rapamycin 1/2 complexes (mTOR) [1,2], is in clinical trials for treatment of various solid tumors [3]. This agent targets the critical survival pathway PI3K/ PTEN/Akt/mTOR [4,5]. Akt and mTOR with phosphorylation of key substrates involved in preventing cell death [8] These signals are highly triggered in many cancer types; and mutations in PI3K/AKT have been implicated in the pathogenesis of several human carcinomas [9]. Inhibitors of PI3K possess potent activities in these tumors [11]; and many of these drugs are in clinical trials with promising results [12,13]

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