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Menez C.,National Polytechnic Institute of Toulouse | Mselli-Lakhal L.,National Polytechnic Institute of Toulouse | Foucaud-Vignault M.,National Polytechnic Institute of Toulouse | Balaguer P.,Institute Of Recherche En Cancerologie Of Montpellier | And 4 more authors.
Biochemical Pharmacology | Year: 2012

Ivermectin is widely used in human and veterinary medicine for the control of helminth infections. Ivermectin is known to interact with P-glycoprotein (P-gp/MDR1), being a good substrate and a potent inhibitor, however, the influence of ivermectin on the expression of the transporter has not been investigated. Expression of P-glycoprotein was investigated in cultured mouse hepatocytes acutely exposed to ivermectin. The two P-glycoprotein murine isoforms, Mdr1a and Mdr1b, mRNA levels were assessed by real-time RT-PCR. Ivermectin induced a clear time- and concentration-dependent up-regulation of Mdr1a and Mdr1b mRNA levels (as early as a 12-h exposure and up to 2.5-fold at 10 μM). Moreover, ivermectin-treated cells displayed enhanced cellular efflux of the P-glycoprotein substrate calcein that was inhibited by the P-glycoprotein blocker valspodar, providing evidence that the ivermectin-induced P-glycoprotein was functional. The mechanisms underlying these effects were investigated. Ivermectin-mediated Mdr1 mRNA induction was independent of the two nuclear receptors CAR and PXR, which are known to be involved in drug transporters regulation. Moreover, by using reporter cell lines that detects specific ligand-activated transcription factors, we showed that ivermectin did not displayed CAR, PXR or AhR ligand activities. However, studies with actinomycin D revealed that the half-life of Mdr1a and Mdr1b mRNA were significantly prolonged by two-fold in ivermectin-treated cells suggesting a post-transcriptional mode of ivermectin regulation. This study demonstrates for the first time that ivermectin induces P-glycoprotein overexpression through post-transcriptional mRNA stabilization, thus offering insight into the mechanism of reduced therapeutic efficacy and development of ivermectin-resistant parasites. © 2011 Elsevier Inc. All rights reserved.

Freiss G.,Institute Of Recherche En Cancerologie Of Montpellier | Freiss G.,French Institute of Health and Medical Research | Freiss G.,Montpellier University | Chalbos D.,Institute Of Recherche En Cancerologie Of Montpellier | And 2 more authors.
Anti-Cancer Agents in Medicinal Chemistry | Year: 2011

Protein tyrosine phosphorylation plays a major role in many cellular functions implicated in cancer development and progression, but only a few of the known protein tyrosine phosphatases have yet been clearly classified as oncogenes or tumor suppressors. PTPL1 interacts with tumor-associated proteins, suggesting a link between PTPL1, the PTPN13 gene product, and tumorigenesis or cancer progression. However, the impact of PTPL1 on cancer is divided between its capacity to counteract the activity of oncogenic tyrosine kinases and its inhibitory interaction with the death receptor, Fas. In this manuscript, we review the PTPL1-interacting proteins implicated in cancer. In addition, we examine the phenotypic arguments concerning both the PTPL1/Fas interaction and the ability of PTPL1 to inhibit signaling from growth factor receptors or oncogenes with tyrosine kinase activity. Finally, we compare the alterations in expression and the genetic and epigenetic arguments supporting an oncogenic or an anti-oncogenic impact of PTPL1. © 2011 Bentham Science Publishers Ltd.

Westover D.,Roswell Park Cancer Institute | Ling X.,Roswell Park Cancer Institute | Ling X.,Canget Biotekpharma, Llc | Lam H.,Roswell Park Cancer Institute | And 6 more authors.
Molecular Cancer | Year: 2015

Background: Irinotecan is a camptothecin analogue currently used in clinical practice to treat advanced colorectal cancer. However, acquired resistance mediated by the drug efflux pump ABCG2 is a recognized problem. We reported on a novel camptothecin analogue, FL118, which shows anticancer activity superior to irinotecan. In this study, we sought to investigate the potency of FL118 versus irinotecan or its active metabolite, SN-38, in both in vitro and in vivo models of human cancer with high ABCG2 activity. We also sought to assess the potency and ABCG2 affinity of several FL118 analogues with B-ring substitutions. Methods: Colon and lung cancer cells with and without ABCG2 overexpression were treated with FL118 in the presence and absence of Ko143, an ABCG2-selective inhibitor, or alternatively by genetically modulating ABCG2 expression. Using two distinct in vivo human tumor animal models, we further assessed whether FL118 could extend time to progression in comparison with irinotecan. Lastly, we investigated a series of FL118 analogues with B-ring substitutions for ABCG2 sensitivity. Results: Both pharmacological inhibition and genetic modulation of ABCG2 demonstrated that, in contrast to SN-38, FL118 was able to bypass ABCG2-mediated drug resistance. FL118 also extended time to progression in both in vivo models by more than 50% compared with irinotecan. Lastly, we observed that FL118 analogues with polar substitutions had higher affinity for ABCG2, suggesting that the nonpolar nature of FL118 plays a role in bypassing ABCG2-mediated resistance. Conclusions: Our results suggest that in contrast to SN-38 and topotecan, FL118 is a poor substrate for ABCG2 and can effectively overcome ABCG2-mediated drug resistance. Our findings expand the uniqueness of FL118 and support continued development of FL118 as an attractive therapeutic option for patients with drug-refractory cancers resulting from high expression of ABCG2. © Westover et al.; licensee BioMed Central.

Le Maire A.,French Institute of Health and Medical Research | Le Maire A.,French National Center for Scientific Research | Teyssier C.,French Institute of Health and Medical Research | Teyssier C.,French National Center for Scientific Research | And 18 more authors.
Nature Structural and Molecular Biology | Year: 2010

In the absence of ligand, some nuclear receptors, including retinoic acid receptor (RAR), act as transcriptional repressors by recruiting corepressor complexes to target genes. This constitutive repression is crucial in metazoan reproduction, development and homeostasis. However, its specific molecular determinants had remained obscure. Using structural, biochemical and cell-based assays, we show that the basal repressive activity of RAR is conferred by an extended Β-strand that forms an antiparallel Β-sheet with specific corepressor residues. Agonist binding induces a Β-strand-to-α-helix transition that allows for helix H11 formation, which in turn provokes corepressor release, repositioning of helix H12 and coactivator recruitment. Several lines of evidence suggest that this structural switch could be implicated in the intrinsic repressor function of other nuclear receptors. Finally, we report on the molecular mechanism by which inverse agonists strengthen corepressor interaction and enhance gene silencing by RAR. © 2010 Nature America, Inc. All rights reserved.

Fritz V.,Institute Of Recherche En Cancerologie Of Montpellier | Fritz V.,Montpellier University | Fajas L.,Institute Of Recherche En Cancerologie Of Montpellier | Fajas L.,Montpellier University
Oncogene | Year: 2010

Cancer development involves major alterations in cells metabolism. Enhanced glycolysis and de novo fatty acids synthesis are indeed characteristic features of cancer. Cell proliferation and metabolism are tightly linked cellular processes. Others and we have previously shown a close relationship between metabolic responses and proliferative stimuli. In addition to trigger proliferative and survival signaling pathways, most oncoproteins also trigger metabolic changes to transform the cell. We present herein the view that participation of cell-cycle regulators and oncogenic proteins to cancer development extend beyond the control of cell proliferation, and discuss how these new functions may be implicated in metabolic alterations concomitant to the pathogenesis of human cancers. © 2010 Macmillan Publishers Limited All rights reserved.

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