PFKFB3 Inhibition Attenuates Oxaliplatin-Induced Autophagy and Enhances Its Cytotoxicity in Colon Cancer Cells.

Siyuan Yan,Deru Zhang,Kaile Zhang,Yonghua Bao,Wenao Zheng,Nan Zhou,Wancai Yang

doi:10.3390/ijms20215415

Abstract

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform 3 (PFKFB3), a glycolytic enzyme highly expressed in cancer cells, has been reported to participate in regulating metabolism, angiogenesis, and autophagy. Although anti-cancer drug oxaliplatin (Oxa) effectively inhibits cell proliferation and induces apoptosis, the growing resistance and side-effects make it urgent to improve the therapeutic strategy of Oxa. Although Oxa induces the autophagy process, the role of PFKFB3 in this process remains unknown. In addition, whether PFKFB3 affects the cytotoxicity of Oxa has not been investigated. Here, we show that Oxa-inhibited cell proliferation and migration concomitant with the induction of apoptosis and autophagy in SW480 cells. Both inhibition of autophagy by small molecule inhibitors and siRNA modification decreased the cell viability loss and apoptosis induced by Oxa. Utilizing quantitative PCR and immunoblotting, we observed that Oxa increased PFKFB3 expression in a time- and dose-dependent manner. Meanwhile, suppression of PFKFB3 attenuated both the basal and Oxa-induced autophagy, by monitoring the autophagic flux and phosphorylated-Ulk1, which play essential roles in autophagy initiation. Moreover, PFKFB3 inhibition further inhibited the cell proliferation/migration, and cell viability decreased by Oxa. Collectively, the presented data demonstrated that PFKFB3 inhibition attenuated Oxa-induced autophagy and enhanced its cytotoxicity in colorectal cancer cells.

Highlights

Colorectal cancer (CRC) is one of the major human malignant tumors, which ranks as the third most common and fourth most common cancer according to morbidity and mortality, respectively
A new finding in the present study is that Oxa induces autophagy with a concomitant promotion of PFKFB3 expression at both mRNA and protein levels in SW480 colon cancer cells
Inhibition of PFKFB3 promotes the cytotoxic effect of Oxa, such as cell viability, proliferation, and migration

Summary

Introduction

Colorectal cancer (CRC) is one of the major human malignant tumors, which ranks as the third most common and fourth most common cancer according to morbidity and mortality, respectively. As a highly conversed process in maintaining homeostasis during stresses, autophagy plays double-edged sword role in tumorigenesis and cancer therapy, during which autophagy is an attempt to resist the factors that changing the cell state [10]. Akt-mTOR negatively regulates autophagy by attenuating the activity of Ulk (unc-51-like kinase 1), which plays an essential role in autophagy initiation [14]; whereas AMPK can activate autophagy indirectly by deactivating the Akt-mTOR pathway [15,16], or directly by inducing Ulk activity [17]. The rapid proliferation of cancer cells results in the lack of normal and mature vessels in the internal solid tumor, and the consequent hypoxia and nutrition deficiency microenvironment may activate the AMPK pathway and autophagy process to maintain cancer cell survival [18,19]

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Results

Conclusion