ZSTK474, a specific class I phosphatidylinositol 3-kinase inhibitor, induces G1 arrest and autophagy in human breast cancer MCF-7 cells.

Yaochen Wang,Yuling Qiu,Xi Chen,Dexin Kong,Meihua Jin,Ran Wang,Jing Liu,Guanwei Fan

doi:10.18632/oncotarget.7658

Abstract

Multifaceted activities of class I phosphatidylinositol 3-kinase (PI3K) inhibitor ZSTK474 were investigated on human breast cancer cell MCF-7. ZSTK474 inhibited proliferation of MCF-7 cells potently. Flow cytometric analysis indicated that ZSTK474 induced cell cycle arrest at G1 phase, but no obvious apoptosis occurred. Western blot analysis suggested that blockade of PI3K/Akt/GSK-3β/cyclin D1/p-Rb pathway might contribute to the G1 arrest induced. Moreover, we demonstrated that ZSTK474 induced autophagy in MCF-7 cells by use of various assays including monodansylcadaverine (MDC) staining, transmission electron microscopy (TEM), tandem mRFP-GFP-LC3 fluorescence microscopy, and western blot detection of the autophagy protein markers of LC3B II, p62 and Atg 5. Inhibition of class I PI3K and the downstream mTOR might be involved in the autophagy-inducing effect. Combinational use of ZSTK474 and autophagy inhibitors enhanced cell viability, suggesting ZSTK474-induced autophagy might contribute to the antitumor activity. Our report supports the application of ZSTK474, which is being evaluated in clinical trials, for breast cancer therapy.

Highlights

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among females worldwide, with an estimated 1.7 million cases and over 521 thousand deaths in 2012 [1]
Class I phosphatidylinositol 3-kinases (PI3Ks), often referred to as PI3Ks, are lipid kinases that preferentially phosphorylate phosphatidylinositol 4,5-bisphosphate (PIP2) to generate phosphatidylinositol 3,4,5-trisphosphate (PIP3) which activates the downstream Akt and mammalian target of rapamycin, and stimulates signal pathways involved in cell proliferation, etc
Since cell cycle progression is required for cell proliferation, we investigated the effect of ZSTK474 on cell cycle distribution in MCF7 cells

Summary

Introduction

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among females worldwide, with an estimated 1.7 million cases and over 521 thousand deaths in 2012 [1]. Clinical treatment of breast cancer mainly includes surgery, radiation, and chemotherapy [2]. Numbness often occur after surgery and radiation, and current chemotherapy often leads to impaired fertility and premature osteoporosis, etc. Class I phosphatidylinositol 3-kinases (PI3Ks), often referred to as PI3Ks, are lipid kinases that preferentially phosphorylate phosphatidylinositol 4,5-bisphosphate (PIP2) to generate phosphatidylinositol 3,4,5-trisphosphate (PIP3) which activates the downstream Akt and mammalian target of rapamycin (mTOR), and stimulates signal pathways involved in cell proliferation, etc. The frequent amplification and gain-of-function mutations of PIK3CA which encodes PI3K catalytic subunit p110a, the dysregulation of PI3K/Akt pathway due to the upstream receptor tyrosine kinase (RTK), and the loss-of-function mutations of PTEN (phosphatase and tensin homolog deleted on chromosome 10), in cancer, suggest that PI3K is a desired target for cancer therapy [4]. ZSTK474, 2(2-difluoromethylbenzimidazol-1-yl) -4, 6-dimorpholino-1, 3, 5-triazine, is an orally administered pan-class I PI3K inhibitor identified by JFCR39 drug discovery system [6]

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Results

Conclusion