<p>ARHGAP4 mediates the Warburg effect in pancreatic cancer through the mTOR and HIF-1α signaling pathways</p>

Abstract

Objective The phenomenon that cancer cells avidly exhibit glycolysis with lactate secretion and decrease in mitochondrial activity under aerobic conditions is known historically as the Warburg effect. Rho GTPase-activating protein 4 (ARHGAP4) is an important negative regulator of the Rho signaling pathway that was associated with the tumorigenesis. Our study aims to determine the function of ARHGAP4 in controlling the glycolytic process of pancreatic cancer in vitro and possible molecular mechanism involved. Methods ARHGAP4 and PKM2 expressions in pancreatic cancer tissues were measured by immunohistochemistry. Human pancreatic cancer cells transfected with ARHGAP4 expressing lentivirus or siRNA were treated with either mTOR inhibitor (Rapamycin) or HIF-1α inhibitor (YC-1), and the effects were analyzed on cell viability, glucose uptake, lactate release, and the levels of ARHGAP4, p-mTOR, mTOR, PKM2, and HIF-1α expression. Results Our findings showed that ARHGAP4 and PKM2 expressions were, respectively, down-regulated and up-regulated in pancreatic cancer tissues. Overexpression of ARHGAP4 significantly inhibited cell viability, glucose uptake, lactate release, PKM2 expression, and activation of mTOR and HIF-1α signaling pathways in pancreatic cancer cells while ARHGAP4 silencing and treatment of Rapamycin or YC-1 showed inverse effects. Additionally, ARHGAP4 downregulation induced cell morphology of pancreatic cancer was inhibited by Rapamycin or YC-1 treatment. Conclusion These findings suggest that mTOR and HIF-1α signaling pathways can regulate the ARHGAP4-mediated glycolytic process of pancreatic cancer.

<p>miR-939-5p Contributes to the Migration and Invasion of Pancreatic Cancer by Targeting ARHGAP4</p>

“…Previous studies showed that ARHGAP4 inhibited invasion and migration in pancreatic cancer cells through inhibiting βcatenin activation 12 and regulated Warburg effect through HIF-1α and mTOR signaling pathways. 13 β-catenin as well as its target C-myc expression was increased in ovarian cancer cells with miR-939 up-regulation, but decreased with miR-939 down-regulation. 34 C-myc has also been reported to regulate aerobic glycolysis and promote tumor progression in pancreatic cancer.…”

“…25 In addition to p190 RhoGAP, only ARHGAP4 has been found to correlate with pathological stages, vascular invasion and prognosis of pancreatic cancer patients and regulate Warburg effect as well as cell invasion and migration. 12,13 Our previous study demonstrated decreased ARHGAP4 protein levels in pancreatic cancer tissues based on the immunohistochemical staining on tissue microarrays. Here, the decreased ARHGAP4 mRNA levels in pancreatic cancer tissues were also observed compared with the adjacentnormal tissues.…”

“…Our previous studies have shown decreased ARHGAP4 protein expression in pancreatic cancer tissues compared with the non-tumor tissues by immunohistochemistry. 12,13 Here, the ARHGAP4 mRNA expression was also measured by Real-time PCR analysis in pancreatic cancer tissues. ARHGAP4 mRNA levels in pancreatic cancer tissues were markedly decreased compared with the adjacent-normal tissues ( Figure 1A).…”

“…9 Besides, evidences have been reported that ARHGAP4 inhibits cell motility and axon outgrowth, 10 associates with nephrogenic diabetes insipidus and intellectual disability, 11 correlates with pathological stages, vascular invasion and prognosis of pancreatic cancer patients, and regulates glycolysis, invasion and migration in pancreatic cancer. 12,13 Nevertheless, the regulation of ARHGAP4 in pancreatic cancer is still undiscovered microRNAs (miRNA) are small endogenous non-coding RNA molecules with a length of about 18-25 nucleotides that repress protein translation through binding to the 3ʹ-untranlated region (UTR) of their target mRNA and are significantly involved in various cancers, including pancreatic cancer. [14][15][16] High expression of miR-196a, miR-27a, miR-221, miR-143, miR-135b, miR-199b-5p and miR-21, but low expression of miR-744, miR-455-3p and miR-655, in pancreatic cancer samples were found compared with normal samples and associated with poor prognosis.…”

An overview of biological research on hypoxia-inducible factors (HIFs)

“…ARHGAP4 mediates the Warburg effect of pancreatic cancer through mTOR and HIF-1a signalling pathway [74]. Necrostatin 1 (NEC-1) effectively protects renal ischaemia-reperfusion (I/R) injury by inhibiting necrotising ptosis, oxidative stress, and inflammatory response, and may function by mediating HIF-1a/miR-26a/TRPC6/PARP1 signalling pathway [75]. HIF-1a/phosphokinase 4/autophagy pathway has a protective effect on the vascular smooth muscle cell calcification induced by advanced glycation end products, i.e.…”