Resistance Of Pancreatic Cancer Cells Research Articles

Abstract 2188: Comparing effects of small molecular weight compounds on proliferation and chemotaxis of pancreatic cancer cells

Abstract Background & Aims: The new therapy for pancreatic cancer which has the poorest prognosis among malignant tumors is high demand nowadays. The overall 5-year survival rate in all stages of this type of cancer is less than 5%, even with the multimodality therapy, including surgery, chemotherapy and radiotherapy. Although gemcitabine (GEM) is a key drug in the treatment of advanced pancreatic cancer, the therapeutic effect is limited because of drug resistance. Heat shock protein 90 (HSP90) is known to be overexpressed in several types of cancer cells, and its inhibition has shown promise in the treatment of solid malignancies. Src kinases work as a signal switch for multiple molecular signal transduction pathways. The objective of this study is to evaluate an antitumor effect of three kinds of small molecular weight compounds (antimetabolite Gemcitabine, HSP90 inhibitor NVP-AUY922, and Src kinase inhibitor Dasatinib) on tumor growth and chemotaxis in pancreatic cancer cell lines. Methods: Pancreatic cancer cell lines were treated with each of the 3 compounds to examine the effect on proliferation assay, apoptosis assay, Western blotting, and chemotaxis assay. Results: Of these compounds, HSP90 inhibitor inhibited cell proliferation in pancreatic cancer cells best in a dose- and time-dependent manner. Growth inhibitory effect of HSP90 inhibitor for pancreatic cancer cells were highest of the three. Further, HSP90 inhibitor inhibited the growth of gemcitabine sensitive and resistant pancreatic cancer cell lines. With flowcytometry and immunostaining, HSP90 inhibitor had higher apoptosis-inducing effect than gemcitabine. In the chemotaxis assay, HSP90 inhibitor inhibited the migration of pancreatic cancer cell best in the three compounds. In western blotting, HSP90 inhibitor suppressed the expression of multiple receptor tyrosine kinase proteins as well as the signal transduction in PI3K-Akt and RAS-MAPK pathways. Conclusion: In this study, HSP90 inhibitor was the best of 3 small molecular compounds and has proven effective in gemcitabine sensitive and resistant pancreatic cancer. The HSP90 inhibitor is useful as an antitumor drug by inhibiting proliferation and chemotaxis of pancreatic cancer cells through multiple kinase pathways. Citation Format: Masahiro Yamamura, Akira Yamauchi, Naoki Katase, Masakiyo Sakaguchi, Yosuke Katata, Hiroaki Tanioka, Makoto Okawaki, Takeshi Nagasaka, Yoshiyuki Yamaguchi. Comparing effects of small molecular weight compounds on proliferation and chemotaxis of pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2188.

Harmine suppresses the proliferation of pancreatic cancer cells and sensitizes pancreatic cancer to gemcitabine treatment.

PurposePancreatic carcinoma is one of the most deadliest types of cancer, and relatively insensitive to the currently available chemotherapy. Thus, the discovery of novel therapeutic agents to prolong the survival times of patients with pancreatic cancer is urgently required.MethodsCell proliferation was assessed using the sulforhodamine B and cell clone formation assay, apoptosis was analyzed through Annexin V/PI staining, analysis of cell cycle distribution was determined by PI staining, and the expression of proteins was detected via Western blotting.ResultsOur data showed that harmine exerted an anti-proliferative effect and cell cycle arrest at G2/M in pancreatic cancer cells. Meanwhile, harmine plus gemcitabine showed strong synergy in inhibiting the proliferation of pancreatic cancer cells. Furthermore, harmine induced apoptosis and enhanced the gemcitabine-induced apoptosis in pancreatic cancer cells. The AKT/mTOR pathway is involved in mechanisms of gemcitabine resistance in pancreatic cancer cells, our data demonstrated that harmine plus gemcitabine significantly suppressed the AKT/mTOR signaling pathway.ConclusionHarmine may be a potential candidate for the treatment of pancreatic cancer. Morever, the combination of harmine with gemcitabine appears to be an attractive option for the treatment of patients with pancreatic cancer.

Effect of ARK5 on the anti-tumour activity of OSI-027 via regulation of epithelial-mesenchymal transition in pancreatic cancer.

e15758 Background: Pancreatic cancer (PC) is one of the most common lethal malignancies,OSI-027, a selective inhibitor of mTOR, has anti-tumour activity in PC and is currently in phase II clinical trials. According to the results of our previous study, OSI-027 sensitivity varies across pancreatic cancer cell lines; however, the underlying mechanisms are unclear. Methods: In this study,We sought to investigate the regulatory mechanisms underlying OSI-027 resistance in PC under both in vitro and in vivo conditions. Results: We demonstrated that in PC, sensitivity to OSI-027 was negatively correlated with ARK5 expression, and ARK5 knockdown could enhance OSI-027 sensitivity. Further, the mechanistic experiments showed that ARK5 inhibition could reverse EMT induced by OSI-027. Suppression of EMT by Twist siRNA could sensitize pancreatic cancer cells to OSI-027, but the combination of Twist siRNA and ARK5 siRNA did not enhance the anti-tumour effect of OSI-027. Moreover, under hypoxia-induced EMT, the cancer cells were less sensitive to OSI-027, but ARK5 siRNA could block the EMT process. The in vivo experiments showed that the combination of ARK5 and Twist siRNAs could enhance the anti-tumour effect of OSI-027 and restrain OSI-027-induced EMT. Conclusions: The results indicate that ARK5 plays a role in the resistance of pancreatic cancer cells to OSI-027 by regulating EMT and lay the groundwork for future clinical studies.

HNF1A inhibition induces the resistance of pancreatic cancer cells to gemcitabine by targeting ABCB1

BackgroundPancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with poor prognosis, and gemcitabine-based chemotherapy remains an effective option for the majority of PDAC patients. Hepatocyte nuclear factor 1α (HNF1A) is a tumor-suppressor in PDAC, but its role in gemcitabine chemoresistance of PDAC has not been clarified. MethodsThe function of HNF1A in gemcitabine was detected by overexpression and knockdown of HNF1A in vitro and in vitro. The regulatory network between HNF1A and ABCB1 was further demonstrated by luciferase assays, deletion/mutation reporter construct assays and CHIP assays. FindingsHere, we found that HNF1A expression is significantly associated with gemcitabine sensitivity in PDAC cell lines. Moreover, we identified that HNF1A overexpression enhanced gemcitabine sensitivity of PDAC both in vitro and in vitro, while inhibition of HNF1A had the opposite effect. Furthermore, by inhibiting and overexpressing HNF1A, we revealed that HNF1A regulates the expression of MDR genes (ABCB1 and ABCC1) in PDAC cells. Mechanistically, we demonstrated that HNF1A regulates ABCB1 expression through binding to its specific promoter region and suppressing its transcription levels. Finally, the survival analyses revealed the clinical value of HNF1A in stratification of gemcitabine sensitive pancreatic cancer patients. InterpretationOur study paved the road for finding novel treatment combinations using conventional cytotoxic agents with functional restoration of the HNF1A protein, individualized treatment through HNF1A staining and improvement of the prognosis of PDAC patients. FundNational Natural Science Foundations of China and National Natural Science Foundation of Guangdong Province.

Can intracellular drug delivery using hyaluronic acid functionalised pH-sensitive liposomes overcome gemcitabine resistance in pancreatic cancer?

Chemoresistance poses a major challenge in cancer treatment. This study aims to investigate whether intracellular drug delivery using hyaluronic acid (HA) functionalised pH-sensitive liposomes (HA-pSL) can circumvent gemcitabine resistance in pancreatic cancer (PC). HA-pSL were obtained by covalently conjugating HA with preformed pSL. A resistant PC cell line Gr2000 was developed by exposing MIA PaCa-2 cells to gemcitabine, and characterised for their expression of CD44, a receptor for HA, and drug transporters. Cellular uptake and intracellular trafficking of liposomes were determined by confocal microscopy and HPLC analysis of intracellular drug content. Following a pharmacokinetic study in rats, anti-tumour efficacy was compared between MIA PaCa-2 and Gr2000 xenograft mouse models. HA-pSL with an HA density of 179 μg/μmol had a larger size (152.3 vs 136.3 nm), and higher zeta potential (−46.8 vs −10.5 mV) than pSL. The sensitivity of Gr2000 to gemcitabine reduced 444 times compared to its parental cell line, despite no change to the total drug influx, as drug influx- and efflux-transporters in Gr2000 cells were simultaneously up-regulated. Both cell lines had high expression of CD44. HA facilitated cell uptake without compromising the endosome-escape ability of pSL as evidenced by confocal images and co-localization analysis of the dual-fluorescence labelled liposomes and Lysotracker. HA-pSL significantly outperformed pSL, and increased cellular drug influx by 3.6 times in MIA PaCa-2 cells, and 4.6 times in Gr2000 cells. Both liposomes improved the pharmacokinetic profile of free drug. HA-pSL treatment was superior to pSL, and resulted in 6.4 times smaller tumours (weight) in the MIA PaCa-2 xenograft models, and 3.1 smaller in the Gr2000 models compared with the free drug. Taken together, this study highlighted the use of intracellular delivery strategies (HA-CD44 interaction and endosome escape) to overcome gemcitabine resistance, however, the overall improvement was marginal and tumours still existed. Further improvement in delivery efficiency of HA-pSL to target tumours and additional manipulation of the cellular metabolism of gemcitabine are needed to tackle chemoresistance.

Retraction: Targeting the Warburg effect with a novel glucose transporter inhibitor to overcome gemcitabine resistance in pancreatic cancer cells

Retraction: Targeting the Warburg effect with a novel glucose transporter inhibitor to overcome gemcitabine resistance in pancreatic cancer cells

PARP14 promotes the proliferation and gemcitabine chemoresistance of pancreatic cancer cells through activation of NF-κB pathway.

Pancreatic cancer (PC) is the most fatal gastrointestinal malignancy in the world, with a 5-year relative survival of only 8%. Poly(ADP-ribose) polymerase (PARP)14, a member of the macro-PARP subfamily proteins, has been reported to participate in various biologic and pathologic processes in multiple cancers. The roles and underlying molecular mechanisms of PARP14 in PC carcinogenesis, however, remain to be elucidated. In this study, we for the first time discovered that PARP14 was highly expressed in human primary PC specimens and significantly correlated with poor patient prognosis. Using loss-of-function studies in vitro and in vivo, we showed that the knockdown of PARP14 led to enhanced apoptosis, repressed proliferation, and gemcitabine (GEM) resistance of PC cells. Further investigations revealed that PARP14 was significantly overexpressed in GEM-resistant PC cells (SW1990/GZ). And silencing of PARP14 significantly reversed the GEM resistance of SW1990/GZ cells. To the mechanism, PARP14 could stimulate PC progression by the activation of nuclear factor-κB (NF-κB) signaling pathway. And inhibition of NF-κB signal could significantly reverse PARP14-overexpression triggered PC carcinogenesis. In conclusion, PARP14 could promote PC cell proliferation, antiapoptosis, and GEM resistance via NF-κB signaling pathway, highlighting its potential role as a therapeutic target for PC.

GLI inhibitors overcome Erlotinib resistance in human pancreatic cancer cells by modulating E-cadherin

Inhibition of hedgehog (Hh) signalling pathway, including its end effector GLI1, can reverse epithelial-to-mesenchymal transition (EMT) which plays an important role in drug resistance of pancreatic cancer cells to Erlotinib (ETB). This study investigated the effect of GLI inhibitors Forskolin (FSK), GANT-61 (GNT), and Arsenic trioxide (ATX) on suppressing the resistance of pancreatic cancer cells to ETB. The effect of GLI inhibitors was evaluated by measuring mRNA expression levels of EMT factors using quantitative RT-PCR. Immunocytochemistry and flow cytometry were used to assess E-cadherin (E-Cad) and GLI1 protein levels. MTT and apoptosis assays were used to evaluate the synergistic effects for the combination treatment of each GLI inhibitor with ETB. Pancreatic cancer cells PANC-1 treated by GNT showed the highest significant reduction in mRNA levels of GLI1 and other EMT pathway genes. Moreover, GNT was able to upregulate E-Cad and downregulate GLI1 proteins, more than FSK, while ATX had no effect. Apoptosis levels of PANC-1 cells following treatment with LD30 concentrations of FSK, GNT, or ATX, showed 57%, 62% and 67%, respectively, in comparison to ETB (∼48%). Importantly, combination treatments of ETB with either FSK, GNT, or ATX demonstrated a significant increase in apoptotic cells reaching 61% (ETB + FSK), 80% (ETB + GNT) or 88% (ETB + ATX). FSK did not have much effect on the drug resistance of PANC-1 cells to ETB. However, GNT, but more effectively ATX, were able to reduce the drug resistance of this cell line to ETB.

MiR-590-5p Sensitizes Pancreatic Ductal Adenocarcinoma Cells to Radiation by Blocking Autophagy via Targeting ATG3

Background: Resistance against radio therapy is growing concern in treating patients of pancreatic cancer (PC). Improving our depth with regards to mechanisms involved in radio resistance could help in developing strategies for increasing patient's response to this therapy. Here we investigated the role of micro RNAs (miRs) and specifically miR-590-5p in radio-resistance of PC cells. Methods: We successfully developed radio resistant PC cell lines in our lab and subjected them to microarray analysis to compare the levels of miRs with their original parental cell lines. We then transfected the PC cells using miR mimics or inhibitor and performed clonogenic survival assay to study the effects on radiation sensitivity. We also studied the effect of miR-590-5p on autophagy using electron microscopy and Immunoblotting analysis. Luciferase assay was done for identifying mRNA targets of miR-590-5p. Results: The radio resistant PC cells exhibited decreased expression of miR-590-5p with elevated autophagy against the parental cells. The over expression of miR-590-5p inhibited the radiation mediated autophagy and the miR-590-5p inhibitor encouraged autophagy in PC cells. The up-regulation of miR-590-5p enhanced the sensitivity of PC cells towards radiation. We confirmed that ATG-3 as a favorable target of miR-590-5p and was unregulated in radio resistant cells, we also found that ATG-3 was associated with autophagy. MiR-590-5p inhibited radiation-mediated autophagy and enhanced radio sensitivity of PC cells. The results suggested an inverse correlation for miR-590-5p and autophagy in PC tissues. Conclusions: The expression of miR-590-5p in PC cells is associated with elevated levels of autophagy along with ATG-3, which leads to radio resistance; miR-590-5p can be employed to enhance the radio sensitivity of PC cells. Funding Statement: The project was self financed. Declaration of Interests: The authors have no conflict of interest. Ethics Approval Statement: All the patients were educated about the study and informed consent forms were signed before the study. The study was approved from institutional review of research committee at The Second Xiangya Hosipital of Central South University, Changsha, Hunan, China

ROCK2 Confers Acquired Gemcitabine Resistance in Pancreatic Cancer Cells by Upregulating Transcription Factor ZEB1

Background: Gemcitabine resistance is a major clinical challenge in the treatment of pancreatic ductal adenocarcinoma (PDAC). The increasing attention to Rho-associated coil protein kinase 2 (ROCK2)-mediated chemotherapy resistance in a variety of cancers reminded us to explore the effect of ROCK2 signalnaling in the acquired gemcitabine-resistant pancreatic cancer cells (GR cells). Methods: The relative expression of related proteins and mRNA were detected by western blot and real-time PCR, respectively. Short hairpin RNA (shRNA) was used to silencing related genes. The double luciferase reporter gene experiment was used to explore the activation of related gene promoter. Chromatin immunoprecipitation technique (CHIP) was used to detect the ability of transcription factor binding to the promoter. Many other cell based assays were adopted to explore the mechanism of ROCK2 on resistance of GR cells to gemcitabine. Findings: Pharmacological inhibition or gene silencing of ROCK2 markedly sensitized GR cells to gemcitabine by suppressing the expression of zinc-finger-enhancer binding protein 1 (ZEB1). Mechanically, ROCK2-induced sp1 phosphorylation at Thr-453 enhanced the ability of sp1 binding to ZEB1 promoter regions in a p38-dependent manner. Moreover, transcriptional activation of ZEB1 facilitated GR cells to repair gemcitabine-mediated DNA damage via ATM/p-CHK1 signaling pathway. Interpretation: ROCK2 contributed to EMT-induced gemcitabine resistance in pancreatic cancer cells and might provided strong evidence for the clinical application of fasudil, a ROCK2 inhibitor, in gemcitabine-refractory PDAC. Funding Statement: This work was supported by the National Natural Science Foundation of China (No.81372268, No.81672816 and No.81872337), the Program for Jiangsu Province Innovative Research (KYLX16_1120), the Natural Science Foundation for Distinguished Young Scholars of Jiangsu Province (No. BK20130026), the Project Program of State Key Laboratory of Natural Medicines, China Pharmaceutical University (No. ZJ11173). Declaration of Interests: The authors declare that they have no conflict of interest. Ethics Approval Statement: All experiments were performed in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals, and all animal experimental procedures were approved by Experimentation Ethics Review Committee of China Pharmaceutical.

Protein Arginine Methyltransferase 3 Enhances Chemoresistance in Pancreatic Cancer by Methylating hnRNPA1 to Increase ABCG2 Expression.

Pancreatic cancer is poorly responsive to chemotherapy due to intrinsic or acquired resistance. Our previous study showed that epigenetic modifying enzymes including protein arginine methyltransferase 3 (PRMT3) are dysregulated in gemcitabine (GEM)-resistant pancreatic cancer cells. Here, we attempt to elucidate the role of PRMT3 in chemoresistance. Overexpression of PRMT3 led to increased resistance to GEM in pancreatic cancer cells, whereas reduction of PRMT3 restored GEM sensitivity in resistant cells. We identified a novel PRMT3 target, ATP-binding cassette subfamily G member 2 (ABCG2), which is known to play a critical role in drug resistance. PRMT3 overexpression upregulated ABCG2 expression by increasing its mRNA stability. Mass spectrometric analysis identified hnRNPA1 as a PRMT3 interacting protein, and methylation of hnRNPA1 at R31 by PRMT3 in vivo and in vitro. The expression of methylation-deficient hnRNPA1-R31K mutant reduced the RNA binding activity of hnRNPA1 and the expression of ABCG2 mRNA. Taken together, this provides the first evidence that PRMT3 methylates the RNA recognition motif (RRM) of hnRNPA1 and promotes the binding between hnRNPA1 and ABCG2 to enhance drug resistance. Inhibition of PRMT3 could be a novel strategy for the treatment of GEM-resistant pancreatic cancer.

Hypoxia potentiates gemcitabine-induced stemness in pancreatic cancer cells through AKT/Notch1 signaling

BackgroundProfound chemoresistance remains an intractable obstacle in pancreatic cancer treatment. Pancreatic cancer stem cells (CSCs) and the ubiquitous hypoxic niche have been proposed to account for drug resistance. However, the mechanism involved requires further exploration. This study investigated whether the hypoxic niche enhances gemcitabine-induced stemness and acquired resistance in pancreatic cancer cells by activating the AKT/Notch1 signaling cascade. The therapeutic effects of blockading this signaling cascade on gemcitabine-enriched CSCs were also investigated.MethodsThe expression levels of CSC-associated markers Bmi1 and Sox2 as well as those of proteins involved in AKT/Notch1 signaling were measured by Western blot analysis. The expression level of the pancreatic CSC marker CD24 was measured by flow cytometry. Change in gemcitabine sensitivity was evaluated by the MTT assay. The ability of sphere formation was tested by the sphere-forming assay in stem cell medium. The ability of migration and invasion was detected by the transwell migration/invasion assay. A mouse xenograft model of pancreatic cancer was established to determine the effect of Notch1 inhibition on the killing effect of gemcitabine in vivo. The ability of metastasis was investigated by an in vivo lung metastasis assay.ResultsGemcitabine promoted pancreatic cancer cell stemness and associated malignant phenotypes such as enhanced migration, invasion, metastasis, and chemoresistance. The AKT/Notch1 signaling cascade was activated after gemcitabine treatment and mediated this process. Blockading this pathway enhanced the killing effect of gemcitabine in vivo. However, supplementation with hypoxia treatment synergistically enhanced the AKT/Notch1 signaling pathway and collaboratively promoted gemcitabine-induced stemness.ConclusionsThese findings demonstrate a novel mechanism of acquired gemcitabine resistance in pancreatic cancer cells through induction of stemness, which was mediated by the activation of AKT/Notch1 signaling and synergistically aggravated by the ubiquitous hypoxic niche. Our results might provide new insights for identifying potential targets for reversing chemoresistance in patients with pancreatic cancer.

Insights into gemcitabine resistance and the potential for therapeutic monitoring.

Gemcitabine is an important component of pancreatic cancer clinical management. Unfortunately, acquired gemcitabine resistance is widespread and there are limitations to predicting and monitoring therapeutic outcomes. To investigate the potential of metabolomics to differentiate pancreatic cancer cells that develops resistance or respond to gemcitabine treatment. We applied 1D 1H and 2D 1H-13C HSQC NMR methods to profile the metabolic signature of pancreatic cancer cells. 13C6-glucose labeling identified 30 key metabolites uniquely altered between wild-type and gemcitabine-resistant cells upon gemcitabine treatment. Gemcitabine resistance was observed to reprogram glucose metabolism and to enhance the pyrimidine synthesis pathway. Myo-inositol, taurine, glycerophosphocholine and creatinine phosphate exhibited a "binary switch" in response to gemcitabine treatment and acquired resistance. Metabolic differences between naïve and resistant pancreatic cancer cells and, accordingly, their unique responses to gemcitabine treatment were revealed, which may be useful in the clinical setting for monitoring a patient's therapeutic response.

Increased miR-142 and decreased DJ-1 enhance the sensitivity of pancreatic cancer cell to adriamycin.

Phosphatidylinositol-3 kinase (PI3K)/protein kinase B (AKT) signaling pathway is related to tumorigenesis by up-regulating survivin. Phosphatase and tensin homologue deleted on chromosome ten (PTEN) can suppress PI3K/AKT signaling pathway, while DJ-1 is the negative regulator of PTEN. DJ-1 up-regulation is closely correlated with the occurrence, progression, and drug resistance of pancreatic cancer. MicroRNA-142 (MiR-142) is significantly declined in pancreatic cancer tissue. Bioinformatics analysis demonstrated that complementary binding site exists between miR-142 and DJ-1. This investigation, therefore, aimed to study the role of miR-142 in the regulation of DJ-1-PTEN/PI3K/AKT/Survivin signaling pathway as well as in pancreatic cancer cell proliferation, apoptosis, and adriamycin (ADM) resistance. Dual luciferase assay was performed to assess the targeted relationship between miR-142 and DJ-1. MiR-142, DJ-1, and PTEN expressions in SW1990 cells and drug-resistant SW1990/ADM cells were compared. SW1990/ADM cells were divided into five groups, including mimic-NC, miR-142 mimic, small interfere normal control (si-NC), si-DJ-1, and miR-142 mimic + si-DJ-1 groups. DJ-1, PTEN, phosphorylated-AKT (p-AKT), and Survivin expressions were tested. Cell apoptosis was determined by flow cytometry. Cell proliferation was evaluated by EdU staining. MiR-142 targeted inhibited DJ-1 expression. MiR-142, PTEN, and cell apoptosis significantly down-regulated, while DJ-1, p-AKT, Survivin, and cell proliferation significantly elevated in SW1990/ADM cells compared with SW1990 cells. MiR-142 mimics and/or si-DJ-1 transfection markedly reduced DJ-1, p-AKT, and Survivin expressions enhanced PTEN level, attenuated cell proliferation, enhanced cell apoptosis, and weakened ADM resistance. MiR-142 over-expression weakened ADM resistance in pancreatic cancer cells by targeting DJ-1 to enhance PTEN expression and attenuate PI3K/AKT signaling pathway activity.

Knockdown of AGR2 induces cell apoptosis and reduces chemotherapy resistance of pancreatic cancer cells with the involvement of ERK/AKT axis

BackgroundPancreatic cancer (PC), an aggressive human malignancy, presents with a striking resistance to chemotherapy. Interesting, AGR2 has been found to be upregulated in various cancers and has been found to promote the dissemination of PC cells. Thereby, a series of in-vitro experiments were performed to investigate the relationship between AGR2 and the ERK/AKT axis, and to explore whether it affects PC cells. MethodsPositive expression of AGR2 protein in the PC and paracancerous tissues collected from 138 patients with PC was detected using immunohistochemistry. After treatment with FGF2 (an ERK/AKT axis agonist), siRNA against AGR2 or their combination respectively, cell viability, chemotherapy resistance, radiotherapy resistance, migration, invasion and apoptosis in PC cells were detected using CCK8 assay, MTT assay, clone formation assay, wound healing assay, Transwell assay and flow cytometry, respectively. The expressions of AGR2 and ERK/AKT axis-related genes and proteins in tissues and cells were detected using reverse transcription quantitative polymerase chain reaction and Western blot assay. ResultsPC tissues exhibited highly-expressed AGR2 and abnormally activated ERK/AKT axis. FGF2 promoted the expression of AGR2, ERK/AKT axis activation, cell viability, chemotherapy resistance, migration and invasion, but decreased cell apoptosis in PC cells. However, knockdown of AGR2 resulted in inhibition of the ERK/AKT axis, reduced PC cell viability, chemotherapy resistance, migration and invasion but increased cell apoptosis in PC cells. ConclusionThe findings reveal that AGR2 silencing could promote cell apoptosis and inhibit cell migration, invasion and chemotherapy resistance of PC cell with the involvement of the ERK/AKT axis.

Microarray analysis of circular RNA expression profiles associated with gemcitabine resistance in pancreatic cancer cells

Pancreatic cancer (PC) is one of the most malignant tumors of the digestive system due to its rapid progression, metastasis and resistance to chemotherapy. Gemcitabine (GEM) chemotherapy is the first‑choice treatment for advanced PC. However, the effect of GEM‑based chemotherapy on PC is limited due to the development of chemoresistance, and the molecular mechanisms underlying this resistance have yet to be investigated. Circular RNAs (circRNAs), which can function as microRNA sponges, have been found to be involved in the development of several types of cancer. However, research on circRNAs in PC drug resistance is limited. In the present study, the GEM‑resistant PC cell line, SWl990/GZ, was successfully established by treating parental SWl990 cells invitro with increasing concentrations of GEM in culture medium intermittently for 10months. By analyzing the expression profiles of circRNAs in microarray between SWl990/GZ and parental SW1990 cells, we identified 26upregulated and 55downregulated circRNAs (fold change≥2 and P<0.05) among 12,866 detected circRNAs in SWl990/GZ compared with SW1990 cells. Furthermore, the changes in the expression of six representative circRNAs was validated by reverse transcription‑quantitative PCR. In addition, Kyoto Encyclopedia of Genes and Genomes pathway analysis and Gene Ontology analysis were performed. These analyses revealed that the dysregulated circRNAs regulated several cancer‑related pathways, such as the mitogen‑activated protein kinase (MAPK) and mammalian target of rapamycin (mTOR) signaling pathways, and may be involved in the biological process of the regulation of chemoresistance, including nucleic acid metabolic process and cellular response to stress. The present study undertook a comprehensive expression analysis and revealed the functional profiles of differentially expressed circRNAs associated with GEM‑resistance in PC, thereby indicating the possible participation of these dysregulated circRNAs in the development of chemoresistance and providing novel potential therapeutic targets for PC.

Tyrphostin B42 attenuates trichostatin A-mediated resistance in pancreatic cancer cells by antagonizing IL-6/JAK2/STAT3 signaling.

Drug-resistance is the key reason for the ineffectiveness of chemotherapy in pancreatic cancer. Thus, it is very important to explore the molecular mechanisms of drug‑resistance and the methods ofeffective intervention. In the present study, we investigated the effect of tyrphostin B42, also called AG490, on histone deacetylase (HDAC) inhibitor trichostatin A (TSA)‑induced resistance in pancreatic cancer cells (PCCs). Evidence from phase contrast microscope revealed that TSA‑resistant cells (PANC‑1‑TSA) had higher proliferative activity than non‑resistant cells (PANC‑1). This over‑proliferative activity induced by TSA may be associated with abnormal activation of JAK2/STAT3 signaling, which can be strengthened by interleukin‑6 (IL‑6), a STAT3‑upstream inducer, resulting in enhanced expression of STAT3-downstream target genes including c‑Myc, c‑Src, HIF‑1α, and CCND1. In addition, increased expression of Bcl‑2 mRNA and decreased expression of Bax mRNA in PANC‑1‑TSA cells indicated that TSA induced the inhibition of mitochondrial-dependent apoptosis in PCCs. Tyrphostin B42 treatment evidently antagonized the activation of IL‑6/JAK2/STAT3 in a dose‑dependent manner. As a result, tyrphostin B42 inhibited the over‑proliferative activity of PANC‑1‑TSA cells, and downregulated the expression of IL‑6/JAK2/STAT3‑downstream target genes. Moreover, tyrphostin B42 induced the apoptosis of PCCs by regulating the expression of mitochondrial‑related genes. Therefore, these findings demonstrated that tyrphostin B42 attenuated TSA‑mediated resistance in PCCs by antagonizing the IL‑6/JAK2/STAT3 signaling.

MiR-1266 Contributes to Pancreatic Cancer Progression and Chemoresistance by the STAT3 and NF-κB Signaling Pathways

Pancreatic cancer is characterized by chemoresistance after several cycles of chemotherapy, which is a major issue responsible for treatment failure of pancreatic cancer. Therefore, it is necessary to explore the specific mechanism underlying chemotherapeutic resistance to overcome this issue. Here we report that miR-1266 is dramatically elevated and correlates with poor survival and chemotherapy response in pancreatic cancer patients. Upregulation of miR-1266 enhanced the chemoresistance of pancreatic cancer cells to gemcitabine (GEM) in vitro and in vivo; conversely, inhibition of miR-1266 yielded the opposite effect. Importantly, silencing of miR-1266 restored the sensitivity of pancreatic cancer cells to GEM in a dose-dependent manner in vivo. Furthermore, our results demonstrate that miR-1266 promotes resistance of pancreatic cancer cells to GEM by targeting multiple negative regulators of the STAT3 and NF-κB pathways, including SOCS3, PTPN11, ITCH, and TNIP1, leading to constitutive activation of STAT3 and NF-κB signaling. Thus, our findings clarify a novel mechanism by which miR-1266 induces chemotherapeutic resistance in pancreatic cancer, indicating that miR-1266 may be used as chemotherapeutic response indicator. Antagomir-1266 as a chemotherapeutic sensitizer, in combination with GEM, may serve as a rational regimen in the treatment of chemotherapy-resistant pancreatic cancer.

Enzyme-treated Asparagus Extract Down-regulates Heat Shock Protein 27 of Pancreatic Cancer Cells.

From the standpoint of cancer therapy, it is valuable to enhance the anticancer effects of chemotherapy. Our previous reports revealed that up-regulation of heat-shock protein 27 (HSP27) has been linked to gemcitabine resistance of pancreatic cancer cells. Enzyme-treated asparagus extract (ETAS) is an extract that is produced from asparagus. The purpose of this study was to investigate the effect of ETAS on the expression of HSP27 and other HSPs in the gemcitabine-resistant pancreatic cancer cell line KLM1-R. KLM1-R cells were treated with ETAS, and expression levels of HSPs, including HSP27, were investigated by western blotting. ETAS down-regulated HSP27 and pHSP27 (serine 78) in KLM1-R cells, but, HSP70 and GRP78 levels were not altered. This study suggests the potential therapeutic benefit of ETAS in enhancing anticancer effects by its combination with gemcitabine for patients with pancreatic cancer.

Nanoparticle Augmented Radiotherapy using Titanium Oxide Nanoparticles

Titanium oxide is a photoactive material that generates hydroxyl free radicals via water splitting. When doped with rare earth ions titanium oxide nanoparticles are activated by X-rays and X-ray generated electrons and are used to enhance radiotherapy treatment of solid tumours. As the nanoparticles generate free radicals by water splitting the presence of molecular oxygen is not required and aggressive hypoxic tumours may be targeted. A clonogenic assay of radio resistant pancreatic cancer (PANC- 1) cells shows a radiotherapy dose enhancement factor of 1.9 at clinically relevant nanoparticle loadings. A fast growing oropharyngeal cancer (FaDu) xenograft demonstrates that rare earth doped titanium oxide nanoparticles delivered by intratumoural injection disperse throughout the tumour, being taken up by cancer cells and undergoing passive accumulation in the Golgi apparatus. Incident radiotherapy activates the nanoparticles to produce hydroxyl free radicals, destroying the Golgi apparatus, and inducing tumour cell apoptosis. This results in a reduction in proliferating cancer cells and a consequent reduction in tumour regrowth rate by a factor of 3.8. There is no increase in systemic toxicity when using nanoparticles in addition to radiotherapy. Rare earth doped titanium oxide nanoparticles therefore represent a novel approach to tumour treatment via destruction of the cells Golgi apparatus during radiotherapy.