ABSTRACT: Pancreatic ductal adenocarcinoma (PDAC), commonly referred to as pancreatic cancer, ranks among the leading causes of cancer-related deaths in the Western world due to disease presentation at an advanced stage, early metastasis and generally a very limited response to chemotherapy or radiotherapy. Gemcitabine remains a cornerstone of PDAC treatment in all stages of the disease despite suboptimal clinical effects primarily caused by molecular mechanisms limiting its cellular uptake and activation and overall efficacy, as well as the development of chemoresistance within weeks of treatment initiation. To circumvent gemcitabine resistance in PDAC, several novel therapeutic approaches, including chemical modifications of the gemcitabine molecule generating numerous new prodrugs, as well as new entrapment designs of gemcitabine in colloidal systems such as nanoparticles and liposomes, are currently being investigated. Many of these approaches are reported to be more efficient than the parent gemcitabine molecule when tested in cellular systems and in vivo in murine tumor model systems; however, although promising, their translation to clinical use is still in a very early phase. This review discusses gemcitabine metabolism, activation and chemoresistance entities in the gemcitabine cytotoxicity pathway and provides an overview of approaches to override chemoresistance in pancreatic cancer.
Project description:Gemcitabine-based chemotherapy is the most common treatment option for pancreatic ductal adenocarcinoma (PDAC). However, it offers little therapeutic value in many cases due to the rapid development of chemoresistance. MicroRNAs (miRNAs) have been found to play pivotal roles in the chemotherapeutic resistance of PDAC. We found that miR-410-3p was significantly down-regulated in human pancreatic cancer xenograft (HPCx) tumor tissues from gemcitabine-treated mice. Low miR-410-3p expression correlated with gemcitabine resistance in HPCx tumors and PDAC cells as well as poor prognosis in PDAC patients. We also found that miR-410-3p attenuated the gemcitabine resistance of PDAC by targeting the 3'-UTR of HMGB1. Moreover, our study clearly demonstrated that miR-410-3p enhanced chemosensitivity to gemcitabine via inhibiting HMGB1-induced autophagy during chemotherapy in PDAC cells. Our study suggests that miR-410-3p expression may be a useful indicator of the potential for chemoresistance to gemcitabine and provide a potential new therapeutic target for chemoresistance in PDAC.
Project description:Resistance to chemotherapy is a long-standing problem in the management of cancer, and cancer stem cells are regarded as the main source of this resistance. This study aimed to investigate metallothionein (MT)-1G involvement in the regulation of cancer stemness and provide a strategy to overcome chemoresistance in pancreatic ductal adenocarcinoma (PDAC). <b>Methods:</b> MT1G was identified as a critical factor related with gemcitabine resistance in PDAC cells by mRNA microarray. Its effects on PDAC stemness were evaluated through sphere formation and tumorigenicity. LC-MS/MS analysis of conditional medium revealed that activin A, a NF-?B target, was a major protein secreted from gemcitabine resistant PDAC cells. Both loss-of-function and gain-of-function approaches were used to validate that MT1G inhibited NF-?B-activin A pathway. Orthotopic pancreatic tumor model was employed to explore the effects on gemcitabine resistance with recombinant follistatin to block activin A. <b>Results:</b> Downregulation of <i>MT1G</i> due to hypermethylation of its promoter is related with pancreatic cancer stemness. Secretome analysis revealed that activin A, a NF-?B target, was highly secreted by drug resistant cells. It promotes pancreatic cancer stemness in Smad4-dependent or independent manners. Mechanistically, MT1G negatively regulates NF-?B signaling and promotes the degradation of NF-?B p65 subunit by enhancing the expression of E3 ligase TRAF7. Blockade of activin A signaling with follistatin could overcome gemcitabine resistance. <b>Conclusions:</b> MT1G suppresses PDAC stemness by limiting activin A secretion <i>via</i> NF-?B inhibition. The blockade of the activin A signaling with follistatin may provide a promising therapeutic strategy for overcoming gemcitabine resistance in PDAC.
Project description:Pancreatic ductal adenocarcinoma (PDAC), generally known as pancreatic cancer (PC), ranks the fourth leading cause of cancer-related deaths in the western world. While the incidence of pancreatic cancer is displaying a rising tendency every year, the mortality rate has not decreased significantly because of late diagnosis, early metastasis, and limited reaction to chemotherapy or radiotherapy. Adjuvant chemotherapy after surgical resection is typically the preferred option to treat early pancreatic cancer. Although 5-fluorouracil/leucovorin with irinotecan and oxaliplatin (FOLFIRINOX) and gemcitabine/nab-paclitaxel can profoundly improve the prognosis of advanced pancreatic cancer, the development of chemoresistance still leads to poor clinical outcomes. Chemoresistance is multifactorial as a result of the interaction among pancreatic cancer cells, cancer stem cells, and the tumor microenvironment. Nevertheless, more pancreatic cancer patients will benefit from precision treatment and targeted drugs. Therefore, we outline new perspectives for enhancing the efficacy of gemcitabine after reviewing the related factors of gemcitabine metabolism, mechanism of action, and chemoresistance.
Project description:Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease, which is characterized by its high invasiveness, rapid progression, and profound resistance to therapy. Gemcitabine is the first-line treatment option for pancreatic cancer patients, but the overall survival is quite low. Therefore, it is an urgent issue to identify new molecules for improved therapies, with better efficacy and less toxicity. Our previous data indicated that Euchromatic histone-lysine N-methyltransferase 2 (EHMT2) functions as a therapeutic target to override GEM resistance and promote metastasis in the treatment of pancreatic cancer. Here, we screened a small-molecule library of 143 protein kinase inhibitors, to verify cytotoxicity of different inhibitors in EHMT2-depleted cells. We determined that the EHMT2 plays a promising modulating role for targeted PI3K/mTOR inhibition. Our data revealed that EHMT2 down-regulates p27 expression, and this contributes to tumor growth. The depletion of EHMT2, ectopic expression of methyltransferase-dead EHMT2, or treatment with an EHMT2 inhibitor decreases H3K9 methylation of p27 promoter and induces G1 arrest in PANC-1 pancreatic cancer cells. Consistent with these findings, in vivo tumor xenograft models, primary tumors, and the Oncomine database utilizing bioinformatics approaches, also show a negative correlation between EHMT2 and p27. We further demonstrated that low EHMT2 elevated BEZ235 sensitivity through up-regulation of p27 in PDAC cells; high levels of SKP2 decrease BEZ235 responsiveness in PDAC cells. Altogether, our results suggest the EHMT2-p27 axis as a potential marker to modulate cell response to dual PI3K/mTOR inhibition, which might provide a strategy in personalized therapeutics for PDAC patients.
Project description:Pancreatic ductal adenocarcinoma (PDAC) is extremely stroma-rich. Cancer-associated fibroblasts (CAFs) secrete proteins that activate survival and promote chemoresistance of cancer cells. Our results demonstrate that CAF secretome-triggered chemoresistance is abolished upon inhibition of the protein synthesis mTOR/4E-BP1 regulatory pathway which we found highly activated in primary cultures of ?-SMA-positive CAFs, isolated from human PDAC resections. CAFs selectively express the sst1 somatostatin receptor. The SOM230 analogue (Pasireotide) activates the sst1 receptor and inhibits the mTOR/4E-BP1 pathway and the resultant synthesis of secreted proteins including IL-6. Consequently, tumour growth and chemoresistance in nude mice xenografted with pancreatic cancer cells and CAFs, or with pieces of resected human PDACs, are reduced when chemotherapy (gemcitabine) is combined with SOM230 treatment. While gemcitabine alone has marginal effects, SOM230 is permissive to gemcitabine-induced cancer cell apoptosis and acts as an antifibrotic agent. We propose that selective inhibition of CAF protein synthesis with sst1-directed pharmacological compounds represents an anti-stromal-targeted therapy with promising chemosensitization potential.
Project description:Gemcitabine-based chemotherapy is the first-line treatment for pancreatic cancer. However, chemoresistance is a major obstacle to drug efficacy, leading to poor prognosis. Little progress has been achieved although multiple mechanisms are investigated. Therefore, effective strategies are urgently needed to overcome drug resistance. Here, we demonstrate that the transcription factor GATA binding protein 1 (GATA1) promotes gemcitabine resistance in pancreatic cancer through antiapoptotic pathway. GATA1 is highly expressed in pancreatic ductal adenocarcinoma (PDAC) tissues, and GATA1 status is an independent predictor of prognosis and response to gemcitabine therapy. Further investigation demonstrates GATA1 is involved in both intrinsic and acquired gemcitabine resistance in PDAC cells. Mechanistically, we find that GATA1 upregulates Bcl-XL expression by binding to its promoter and thus induces gemcitabine resistance through enhancing Bcl-XL mediated antiapoptosis in vitro and in vivo. Moreover, in PDAC patients, Bcl-XL expression is positively correlated with GATA1 level and predicts clinical outcomes and gemcitabine response. Taken together, our results indicate that GATA1 is a novel marker and potential target for pancreatic cancer. Targeting GATA1 combined with Bcl-XL may be a promising strategy to enhance gemcitabine response.
Project description:BACKGROUND & AIMS:Gemcitabine resistance is rapidly acquired by pancreatic ductal adenocarcinoma (PDAC) patients. Novel approaches that predict the gemcitabine response of patients and enhance gemcitabine chemosensitivity are important to improve patient survival. We aimed to identify genes as novel biomarkers to predict the gemcitabine response and the therapeutic targets to attenuate chemoresistance in PDAC cells. METHODS:Genome-wide RNA interference screening was conducted to identify genes that regulated gemcitabine chemoresistance. A cell proliferation assay and a tumor formation assay were conducted to study the role of lethal giant larvae homolog 1 (LLGL1) in gemcitabine chemoresistance. Levels of LLGL1 and its regulating targets were measured by immunohistochemical staining in tumor tissues obtained from patients who received gemcitabine as a single therapeutic agent. A gene-expression microarray was conducted to identify the targets regulated by LLGL1. RESULTS:Silencing of LLGL1 markedly reduced the gemcitabine chemosensitivity in PDAC cells. Patients had significantly shorter survival (6 months) if they bore tumors expressing low LLGL1 level than tumors with high LLGL1 level (20 months) (hazard ratio, 0.1567; 95% CI, 0.05966-0.4117). Loss of LLGL1 promoted cytokine receptor oncostatin M receptor (OSMR) expression in PDAC cells that led to gemcitabine resistance, while knockdown of OSMR effectively rescued the chemoresistance phenotype. The LLGL1-OSMR regulatory pathway showed great clinical importance because low LLGL1 and high OSMR expressions were observed frequently in PDAC tissues. Silencing of LLGL1 induced phosphorylation of extracellular signal-regulated kinase 2 and specificity protein 1 (Sp1), promoted Sp1 (pThr453) binding at the OSMR promoter, and enhanced OSMR transcription. CONCLUSIONS:LLGL1 possessed a tumor-suppressor role as an inhibitor of chemoresistance by regulating OSMR-extracellular signal-regulated kinase 2/Sp1 signaling. The data sets generated and analyzed during the current study are available in the Gene Expression Omnibus repository (ID: GSE64681).
Project description:<h4>Background</h4>TM4SF1 is overexpressed in pancreatic ductal adenocarcinoma (PDAC) and affects the development of this cancer. Also, multidrug resistance (MDR) is generally associated with tumor chemoresistance in pancreatic cancer. However, the correlation between TM4SF1 and MDR remains unknown. This research aims to investigate the effect of TM4SF1 on gemcitabine resistance in PDAC and explore the possible molecular mechanism between TM4SF1 and MDR.<h4>Methods</h4>The expression of TM4SF1 was evaluated in pancreatic cancer cell lines and human pancreatic duct epithelial (HPDE) cell lines by quantitative RT-PCR. TM4SF1 siRNA transfection was carried out using Hiperfect transfection reagent to knock down TM4SF1. The transcripts were analyzed by quantitative RT-PCR, RT-PCR and western blotting for further study. The cell proliferation and apoptosis were obtained to investigate the sensitivity to gemcitabine of pancreatic cancer cells after silencing TM4SF1 in vitro. We demonstrated that cell signaling of TM4SF1 mediated chemoresistance in cancer cells by assessing the expression of multidrug resistance (MDR) genes using quantitative RT-PCR. In vivo, we used orthotopic pancreatic tumor models to investigate the effect of proliferation after silencing TM4SF1 by a lentivirus-mediated shRNA in MIA PaCa-2 cell lines.<h4>Results</h4>The mRNA expression of TM4SF1 was higher in seven pancreatic cancer cell lines than in HPDE cell lines. In three gemcitabine-sensitive cell lines (L3.6pl, BxPC-3, SU86.86), the expression of TM4SF1 was lower than that in four gemcitabine-resistant cell lines (MIA PaCa-2, PANC-1, Hs766T, AsPC-1). We evaluated that TM4SF1 was a putative target for gemcitabine resistance in pancreatic cancer cells. Using AsPC-1, MIA PaCa-2 and PANC-1, we investigated that TM4SF1 silencing affected cell proliferation and increased the percentages of cell apoptosis mediated by treatment with gemcitabine compared with cells which were treated with negative control. This resistance was associated with the expression of multidrug resistance genes including ABCB1 and ABCC1. In vivo, silencing of TM4SF1 in MIA PaCa-2 cell lines increased the effectiveness of gemcitabine-based treatment in orthotopic pancreatic tumor models evaluated using noninvasive bioluminescent imaging.<h4>Conclusion</h4>These findings suggest that TM4SF1 is a surface membrane antigen that is highly expressed in pancreatic cancer cells and increases the chemoresistance to gemcitabine. Thus, TM4SF1 may be a promising target to overcome the chemoresistance of pancreatic cancer.
Project description:Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with poor survival rates. The presence of cancer stem-like cells (CSCs) is believed to be among the underlying reasons for the aggressiveness of PDAC, which contributes to chemoresistance and recurrence. However, the mechanisms that induce chemoresistance and inhibit apoptosis remain largely unknown.We used serum-free medium to enrich CSCs from panc-1 human pancreatic cancer cells and performed sphere formation testing, flow cytometry, quantitative reverse transcription polymerase chain reaction (RT-qPCR) and semi-quantitative western blotting to confirm the stemness of panc-1 CSCs. Hallmarks of endoplasmic reticulum (ER) stress, including IRE1, PERK, ATF4, ATF6?, GRP78 and uPA expression, were detected after gemcitabine treatment. Effects of gemcitabine-induced uPA expression on cell invasion, sphere formation, colony formation and gemcitabine sensitivity were detected. Electrophoretic mobility shift assays (EMSAs) and RNA-immunoprecipitation (RIP) were performed to detect interaction between the uPA mRNA 3'-UTR and mutant p53-R273H expressed by panc-1 CSCs. The effects of upregulated uPA by gemcitabine on apoptosis were detected by Annexin V-FITC/PI staining, and the impact of uPA on small molecule CP-31398-restored mutant p53 transcriptional activity was measured by a luciferase reporter assay.Enriched panc-1 CSCs expressing high levels of CD44 and CD133 also produced significantly higher amounts of Oct4 and Nanog. Compared with panc-1 cells, panc-1 CSCs presented chemoresistance to gemcitabine. ER stress gene detections demonstrated effects of gemcitabine-induced ER stress on both the pro-apoptotic and pro-survival branches. ER stress-induced ATF6? upregulated level of uPA by transcriptionally activating GRP78. Gemcitabine-induced uPA promoted invasion, sphere formation and colony formation and attenuated apoptosis induced by gemcitabine in panc-1 CSCs, depending on interaction with mutant p53-R273H. Upregulation of uPA abolished CP-31398-mediated restoration of mutant p53 transcriptional activity in panc-1 CSCs.Gemcitabine treatment induced ER stress and promoted mutant p53-R273H stabilization via transcriptionally activated uPA which may contribute to chemoresistance to gemcitabine. Notably, upregulation of uPA by gemcitabine treatment may lead to the failure of CP-31398; thus, a novel strategy for modulating mutant p53 function needs to be developed.