Gemcitabine-resistant Pancreatic Ductal Adenocarcinoma Cells Research Articles

Cholesterol esterification inhibition and gemcitabine synergistically suppress pancreatic ductal adenocarcinoma proliferation.

Recent advances have recognized metabolic reprogramming as an underlying mechanism for cancer drug resistance. However, the role of cholesterol metabolism in drug resistance remain elusive. Herein, we report an increased accumulation of cholesteryl ester in gemcitabine-resistant pancreatic ductal adenocarcinoma (PDAC) cells. A potent inhibitor of acyl-CoA cholesterol acyltransferase-1 (ACAT-1), avasimibe, effectively suppressed proliferation of gemcitabine-resistant PDAC cells. Combination of avasimibe and gemcitabine showed strong synergistic effect in suppressing PDAC cell viability in vitro and tumor growth in vivo. Immunoblotting analysis suggests downregulation of Akt by avasimibe is likely to contribute to the synergism. Collectively, our study demonstrates a new combinational therapeutic strategy to overcome gemcitabine resistance for PDAC treatment.

Difluoromethylornithine Combined with a Polyamine Transport Inhibitor Is Effective against Gemcitabine Resistant Pancreatic Cancer.

Pancreatic ductal adenocarcinoma (PDAC) is highly chemo-resistant and has an extremely poor patient prognosis, with a survival rate at five years of <8%. There remains an urgent need for innovative treatments. Targeting polyamine biosynthesis through inhibition of ornithine decarboxylase with difluoromethylornithine (DFMO) has had mixed clinical success due to tumor escape via an undefined transport system, which imports exogenous polyamines and sustains intracellular polyamine pools. Here, we tested DFMO in combination with a polyamine transport inhibitor (PTI), Trimer44NMe, against Gemcitabine-resistant PDAC cells. DFMO alone and with Trimer44NMe significantly reduced PDAC cell viability by inducing apoptosis or diminishing proliferation. DFMO alone and with Trimer44NMe also inhibited in vivo orthotopic PDAC growth and resulted in decreased c-Myc expression, a readout of polyamine pathway dysfunction. Moreover, dual inhibition significantly prolonged survival of tumor-bearing mice. Collectively, these studies demonstrate that targeting polyamine biosynthesis and import pathways in PDAC can lead to increased survival in pancreatic cancer.

Curcumin sensitizes pancreatic cancer cells to gemcitabine by attenuating PRC2 subunit EZH2, and the lncRNA PVT1 expression

Development of resistance to chemotherapeutic drugs is a major challenge in the care of patients with pancreatic ductal adenocarcinoma (PDAC). Acquired resistance to chemotherapeutic agents in PDAC has been linked to a subset of cancer cells termed 'cancer stem cells' (CSCs). Therefore, an improved understanding of the molecular events underlying the development of pancreatic CSCs is required to identify new therapeutic targets to overcome chemoresistance. Accumulating evidence indicates that curcumin, a phenolic compound extracted from turmeric, can overcome de novo chemoresistance and re-sensitize tumors to various chemotherapeutic agents. However, the underlying mechanisms for curcumin-mediated chemosensitization remain unclear. The Enhancer of Zeste Homolog-2 (EZH2) subunit of Polycomb Repressive Complex 2 (PRC2) was recently identified as a key player regulating drug resistance. EZH2 mediates interaction with several long non-coding RNAs (lncRNAs) to modulate epithelial-mesenchymal transition and cancer stemness, phenomena commonly associated with drug resistance. Here, we report the re-sensitization of chemoresistant PDAC cells by curcumin through the inhibition of the PRC2-PVT1-c-Myc axis. Using gemcitabine-resistant PDAC cell lines, we found that curcumin sensitized chemoresistant cancer cells by inhibiting the expression of the PRC2 subunit EZH2 and its related lncRNA PVT1. Curcumin was also found to prevent the formation of spheroids, a hallmark of CSCs, and to down-regulate several self-renewal driving genes. In addition, we confirmed our in vitro findings in a xenograft mouse model where curcumin inhibited gemcitabine-resistant tumor growth. Overall, this study indicates clinical relevance for combining curcumin with chemotherapy to overcome chemoresistance in PDAC.

Abstract 4166: Role of CD44 as a regulator of adaptive plasticity in pancreatic cancer cells

Abstract Purpose: Patients with pancreatic ductal adenocarcinoma (PDAC) may show an initial objective response to chemotherapy that is usually of short duration. Our research goal is to understand the molecular mechanisms for this short duration response and to more fully define differences between chemosensitive and chemoresistant cells. Cancer cells that undergo an EMT and metastatic tumors show an increase in CD44s expression. In this study, we use CD44 Low and CD44 High isogenic cell models to identifying key molecular networks and potential targets that could benefit therapy. Experiments design: CFPAC1-CD44 Hi and Low cells were sorted by flowcytometry and single clone selection. Isogenic model systems were generated by overexpression CD44s in CF-Low cells. Western blot, MTT, migration and invasion assays had been used to characterize cell growth, invasiveness and gemcitabine sensitivity. Receptor Tyrosine Kinase arrays were used to identify the CD44 regulated molecular networks in these isogenic cell models treated with/without CD44 ligand hyaluronan acid (HA). Summary: CD44s high cells show an EMT phenotype (increase of vimentin and loss of E-cadherin) and increase invasion. Expression of CD44s in CD44 low cells was sufficient to drive EMT partially and drive invasion. By in vitro testing over expressing CD44s is not sufficient to decrease sensitivity to gemcitabine. By Receptor Tyrosine Kinase arrays, CD44 Hi clone cells show increase in IGF-1R phosphorylation. Preliminary data had shown that HA may stimulate ROR2, VEGFR1, and EphB2 phosphorylation in CD44 Hi clone cells. Conclusion: Our previous study suggested that CD44 could be a therapeutic target in Gemcitabine resistant PDAC cells. The current study will further identify the molecular targets that regulated by CD44 pathways. These newly identified targets could be hopefully used for the optimized multimodality therapy to sensitize the PDAC cells to therapy and to benefit the pancreatic cancer patients. Citation Format: Chen Chen, Shujie Zhao, Xiangru Zhao, James W. Freeman. Role of CD44 as a regulator of adaptive plasticity in pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4166. doi:10.1158/1538-7445.AM2017-4166

Inhibitor of Pancreatic Cancer by RHIL1RA—Letter

We have read the article with interest by Zhuang and colleagues ([1][1]) on the combination of IL1R antagonist and gemcitabine in gemcitabine-resistant pancreatic ductal adenocarcinoma (PDAC). The article showed that gemcitabine-induced NF-κB and ERK activation in gemcitabine-resistant PDAC cells

14-3-3σ regulation of and interaction with YAP1 in acquired gemcitabine resistance via promoting ribonucleotide reductase expression.

Gemcitabine is an important anticancer therapeutics approved for treatment of several human cancers including locally advanced or metastatic pancreatic ductal adenocarcinoma (PDAC). Its clinical effectiveness, however, is hindered by existence of intrinsic and development of acquired resistances. Previously, it was found that 14-3-3σ expression associates with poor clinical outcome of PDAC patients. It was also found that 14-3-3σ expression is up-regulated in gemcitabine resistant PDAC cells and contributes to the acquired gemcitabine resistance. In this study, we investigated the molecular mechanism of 14-3-3σ function in gemcitabine resistance and found that 14-3-3σ up-regulates YAP1 expression and then binds to YAP1 to inhibit gemcitabine-induced caspase 8 activation and apoptosis. 14-3-3σ association with YAP1 up-regulates the expression of ribonucleotide reductase M1 and M2, which may mediate 14-3-3σ/YAP1 function in the acquired gemcitabine resistance. These findings suggest a possible role of YAP1 signaling in gemcitabine resistance.

Choline Kinase Alpha (CHKα) as a Therapeutic Target in Pancreatic Ductal Adenocarcinoma: Expression, Predictive Value, and Sensitivity to Inhibitors.

Choline kinase α (CHKα) plays a crucial role in the regulation of membrane phospholipid synthesis and has oncogenic properties in vitro. We have analyzed the expression of CHKα in cell lines derived from pancreatic ductal adenocarcinoma (PDAC) and have found increased CHKα expression, associated with differentiation. CHKα protein expression was directly correlated with sensitivity to MN58b, a CHKα inhibitor that reduced cell growth through the induction of apoptosis. Accordingly, CHKα knockdown led to reduced drug sensitivity. In addition, we found that gemcitabine-resistant PDAC cells displayed enhanced sensitivity to CHKα inhibition and, in vitro, MN58b had additive or synergistic effects with gemcitabine, 5-fluorouracil, and oxaliplatin, three active drugs in the treatment of PDAC. Using tissue microarrays, CHKα was found to be overexpressed in 90% of pancreatic tumors. While cytoplasmic CHKα did not relate to survival, nuclear CHKα distribution was observed in 43% of samples and was associated with longer survival, especially among patients with well/moderately differentiated tumors. To identify the mechanisms involved in resistance to CHKα inhibitors, we cultured IMIM-PC-2 cells with increasingly higher concentrations of MN58b and isolated a subline with a 30-fold higher IC50. RNA-Seq analysis identified upregulation of ABCB1 and ABCB4 multidrug resistance transporters, and functional studies confirmed that their upregulation is the main mechanism involved in resistance. Overall, our findings support the notion that CHKα inhibition merits further attention as a therapeutic option in patients with PDAC and that expression levels may predict response.

MiRNA-181b increases the sensitivity of pancreatic ductal adenocarcinoma cells to gemcitabine in vitro and in nude mice by targeting BCL-2

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease and is usually resistant to chemotherapy. MicroRNA‑181b (miR-181b) has been reported to be associated with chemoresistance in various types of cancer. In this study, we investigated the effects of miR-181b on the chemosensitivity of PDAC cells to gemcitabine and the underlying molecular events. miR-181b mimics and inhibitors were synthesized for transient gene transfection in vitro. Lentivirus carrying miR-181b mimics were used to infect PDAC cells for nude mouse xenograft assays by implanting infected PDAC cells into recipient mice. Cell viability was determined by MTT assays, while gene expression was assessed using qRT-PCR, western blot analysis and enzyme-linked immunosorbent assay (ELISA). miR-181b targeting BCL-2 expression was assessed by a dual-luciferase activity assay. The data showed that miRNA-181b expression sensitized PDAC cells to gemcitabine treatment. Although gemcitabine-resistant PDAC cell sublines (SW1990/GR and CFPAC-1/GR) expressed higher levels of miRNA-181b, gemcitabine induced higher levels of apoptosis in PDAC cells transfected with miRNA-181b mimics. The nude mouse xenograft assay data showed that miR-181b transfection also sensitized the cells to gemcitabine treatment in vivo. Molecularly, bioinformatics data predicted that miR-181b was able to bind to BCL-2 mRNA 3'UTR. The dual luciferase activity assay revealed that miRNA-181b downregulated BCL-2 expression. The results from western blot analysis showed a reduced BCL-2 expression following miR-181b transfection but an enhanced caspase-3 activity in miRNA-181b mimic-transfected PDAC cells. This study demonstrates that miRNA-181b sensitizes PDAC cells to gemcitabine by targeting BCL-2.

Cyclopamine reverts acquired chemoresistance and down-regulates cancer stem cell markers in pancreatic cancer cell lines

The hedgehog (Hh) pathway has been implicated in the pathogenesis of cancer including pancreatic ductal adenocarcinoma (PDAC). Recent studies have suggested that Hh plays an important role in maintaining the cancer stem cell (CSCs) pool. Gemcitabine-resistant pancreatic cancer cells highly express some of the CSCs markers. However, the expression level of Hh members in gemcitabine-resistant pancreatic cancer cells remains unknown. The aim of this study was to verify the expression of HH members, such as Shh, Ptc, SMO and Gli-1 in gemcitabine-resistant PDAC cell lines, and to explore a new strategy to overcome chemoresistance in PDAC. Quantitative real-time RT-PCR (Q-PCR) and western blot were used to evaluate the relative expression level of HH members in SW1990, CFPAC-1 cells and gemcitabine-resistant SW1990, CFPAC-1 cells. The change of cancer stem cell markers and the expression level of HH members before and after cyclopamine treatment was evaluated using flow cytometry and Q-PCR, western blot, respectively. Cell apoptosis after cyclopamine treatment was measured by flow cytometry. CD44, CD133 and the expression level of HH members, including Shh, SMO, Gli-1, were found to be highly expressed in gemcitabine-resistant cells, which were significantly down-regulated by cyclopamine treatment. Flow cytometry analysis showed increased cell apoptosis after cyclopamine treatment. Gemcitabine-resistant pancreatic cancer cells highly express CSCs markers and some of the HH members, and inhibition of HH by cyclopamine is an effective method of reversing gemcitabine resistance in pancreatic cancer.