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KRAS mutation is associated with the progression and growth of pancreatic cancer and contributes to chemo-resistance, which poses a significant clinical challenge in pancreatic cancer. Here, we developed a RT22-ep59 antibody (Ab) that directly targets the intracellularly activated GTP-bound form of oncogenic KRAS mutants after it is internalized into cytosol by endocytosis through tumor-associated receptor of extracellular epithelial cell adhesion molecule (EpCAM) and investigated its synergistic anticancer effects in the presence of gemcitabine in pancreatic cancer. We first observed that RT22-ep59 specifically recognized tumor-associated EpCAM and reached the cytosol by endosomal escape. In addition, the anticancer effect of RT22-ep59 was observed in the high-EpCAM-expressing pancreatic cancer cells and gemcitabine-resistant pancreatic cancer cells, but it had little effect on the low-EpCAM-expressing pancreatic cancer cells. Additionally, co-treatment with RT22-ep59 and gemcitabine synergistically inhibited cell viability, migration, and invasion in 3D-cultures and exhibited synergistic anticancer activity by inhibiting the RAF/ERK or PI3K/AKT pathways in cells with high-EpCAM expression. In an orthotopic mouse model, combined administration of RT22-ep59 and gemcitabine significantly inhibited tumor growth. Furthermore, the co-treatment suppressed cancer metastasis by blocking EMT signaling in vitro and in vivo. Our results demonstrated that RT22-ep59 synergistically increased the antitumor activity of gemcitabine by inhibiting RAS signaling by specifically targeting KRAS. This indicates that co-treatment with RT22-ep59 and gemcitabine might be considered a potential therapeutic strategy for pancreatic cancer patients harboring KRAS mutation. [ABSTRACT FROM AUTHOR]

Background and Aims: Pancreatic cancer is an aggressive malignancy with poor prognosis. Gemcitabine is the standard chemotherapeutic drug used to treat the disease; however, it has a low response rate. Therefore, there is an urgent need to develop new and safe therapies to enhance sensitivity to gemcitabine in treating pancreatic cancer.Methods: The synergistic effect of gemcitabine combined with specific B cell CLL/lymphoma 2 (Bcl-2) inhibitor ABT-199 against pancreatic cancer was tested using cell viability, cell cycle, and apoptosis assays in vitro and in an MIA Paca-2 xenograft model in vivo. Its underlying mechanism was explored using western blotting analysis of Bcl-2 family proteins.Results: ABT-199 not only enhanced the effect of gemcitabine on cell growth inhibition but also promoted gemcitabine-induced apoptosis in pancreatic cancer cell lines. Gemcitabine decreased the expression of anti-apoptotic protein Mcl-1 but increased the expression of anti-apoptotic protein Bcl-2. ABT-199 downregulated the gemcitabine-induced production of Bcl-2 and increased the expression of pro-apoptotic protein Bcl-2 interacting protein (BIM). Mouse xenograft experiments also confirmed the synergistic effect of gemcitabine and ABT-199 on tumor growth inhibition and the induction of tumor cell apoptosis.Conclusion: Our results indicated that ABT-199 improved the anti-tumor effect of gemcitabine on pancreatic cancer by downregulating gemcitabine-induced overexpression of Bcl-2. ABT-199 has already been investigated in phase 3 clinical trials for chronic lymphocytic leukemia; therefore, it may serve as a potential drug to improve the sensitivity of pancreatic cancer to gemcitabine. [ABSTRACT FROM AUTHOR]

As a fundamental metabolic enzyme, anti-Thymidylate synthase (TS) strategy has been shown to be an effective therapy for human cancers. However, the genuine effects of TS in pancreatic ductal adenocarcinoma (PDA) are still conflicting. We systemically assessed the prognostic value and whether TS associated with malignant progression in PDA. Protein and mRNA expression level of TS were evaluated in en bloc PDA samples, the prognostic effect of TS expressed in cytoplasm or cytonuclear was determined separately in the first time. The impact of TS on tumor cell behaviors was assessed in in vitro assays, and the TS associated metastatic potential was further determined in two different PDA metastatic models. The retrospective clinical analysis firstly demonstrated that tumor cytonuclear TS expression was positively correlated with lymphatic metastasis and negatively correlated with the overall survival (OS) in PDA patients. The subsequent experiments further confirmed that TS depletion can effectively abate EMT (epithelial to mesenchymal) process in in vitro and decline most of the metastatic lesions in two different PDA mice models, and the deoxythymidine monophosphate (dTMP) biosynthesis malfunction resulted imbalanced dNTP pools may be the fundamental causation. Collectively, the present study suggested the prospective strategy of combined anti-TS scheme for metastatic PDA, and we strongly suggest further clinical standardization research with a large cohort to verify the prognostic value and the therapeutic potential of TS in PDA. [ABSTRACT FROM AUTHOR]

Background and Aims: Pancreatic ductal adenocarcinoma (PDAC) represents the fourth cause of cancer-related death. We aimed to evaluate whether gemcitabine treatment shapes the gut microbiota in a model of PDAC xenografted mice.Materials and Methods: Pancreatic cancer xenograft mice were subjected to gemcitabine injection once per week for 3 weeks to assess the tumor volume as compared to control mice injected with normal saline solution. The composition of fecal microbiota, the activation of NF-kB pathway in cancer tissues and the serum metabolomics were further analyzed.Results: Gemcitabine considerably decreases the proportion of Gram- positive Firmicutes (from about 39 to 17%) and the Gram- negative Bacteroidetes (from 38 to 17%) which are the two dominant phyla in the gut of tumor-bearing control mice. This downshift was replaced by an increase of Proteobacteria (Escherichia coli and Aeromonas hydrophila) from 15 up to 32% and Verrucomicrobia (Akkermansia muciniphila) from 5 to 33% in the gut of drug-receiving mice. An overall increase in inflammation-associated bacteria was observed upon gemcitabine. Consistently, activation of the NF-kB canonical pathway was found in cancer tissues from gemcitabine-treated mice. Serum metabolomics revealed a significant decrease of the purine compounds inosine and xanthine, and a decreasing trend for their metabolically-related molecule hypoxanthine.Discussion: Understanding chemotherapy side effects may explain the lack of activity or the chemoresistant processes and it may help to set up strategies to improve the effectiveness of therapy. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the safety and efficacy of mocetinostat (a Class I/IV HDAC inhibitor) in combination with gemcitabine in patients with solid tumors, including pancreatic cancer.Methods: In this open-label, non-randomized Phase I/II study (NCT00372437) sequential cohorts of patients with solid tumors received gemcitabine (1000 mg/m2, day 1 of three consecutive weeks, 4-week cycles) and oral mocetinostat [50-110 mg, three times per week (TIW)]. The maximum tolerated dose (MTD) and recommended Phase II dose (RP2D) was determined based on dose-limiting toxicities in Cycle 1 (Phase I study). The MTD/RP2D was further evaluated in patients with advanced pancreatic cancer (Phase II study) using a two-stage design. The Phase II primary endpoint was overall response rate (ORR).Results: Forty-eight patients were enrolled into the Phase I (n = 25) and Phase II (n = 23) studies. In the Phase I study, the MTD/RP2D was mocetinostat 90 mg TIW + gemcitabine 1000 mg/m2. Grade ≥ 3 treatment-related adverse events (AEs) were reported by 81% of all patients, the most frequent being fatigue (38%) and thrombocytopenia (19%). The ORR was 11% in the Phase I study (n = 2 patients with pancreatic cancer, responses lasting for 16.8 and 4.0 months, respectively). As no responses were seen in the Phase II cohort, the study was terminated.Conclusions: Mocetinostat TIW in combination with gemcitabine was associated with significant toxicities in patients with advanced pancreatic cancer. The level of clinical activity of this treatment combination was not considered high enough to merit further testing in this setting. [ABSTRACT FROM AUTHOR]

Purpose: Following a previously published pre-clinical validation, this phase I study evaluated the safety, maximum tolerated dose, anti-tumour activity and immune status of a gemcitabine-chloroquine combination as a first- or late-line treatment in patients with metastatic or unresectable pancreatic cancer.Methods: In this 3 + 3 dose escalation study, patients received a single weekly standard dose of intravenous gemcitabine, followed by single weekly oral intake of 100, 200 or 300 mg of chloroquine. Tumour response was assessed using the Response Evaluation Criteria in Solid Tumors version 1.1. Immune status was evaluated by RT-PCR to measure the relative expression of immune-related genes in peripheral blood mononuclear cells (PBMCs).Results: Overall, nine patients [median age 72 years; interquartile range (IQR), 68-78 years] were treated. No dose-limiting toxicities as defined in the protocol were observed. Three patients experienced partial response, and two patients had stable disease. The median time to progression was 4 months (95% CI 0.8-7.2), and the median overall survival was 7.6 months (95% CI 5.3-9.9). Among 86 assayed immune genes, three were significantly differentially expressed in PBMCs from responding versus non-responding patients: interferon-gamma receptor-1, toll-like receptor 2, and beta-2 microglobulin.Conclusions: The addition of chloroquine to gemcitabine was well tolerated and showed promising effects on the clinical response to the anti-cancer chemotherapy. Based on these initial results, the efficacy of the gemcitabine-chloroquine combination should be further assessed. [ABSTRACT FROM AUTHOR]

Background: Chk1 inhibitors have emerged as promising anticancer therapeutic agents particularly when combined with antimetabolites such as gemcitabine, cytarabine or hydroxyurea. Here, we address the importance of appropriate drug scheduling when gemcitabine is combined with the Chk1 inhibitor MK-8776, and the mechanisms involved in the schedule dependence.Methods: Growth inhibition induced by gemcitabine plus MK-8776 was assessed across multiple cancer cell lines. Experiments used clinically relevant "bolus" administration of both drugs rather than continuous drug exposures. We assessed the effect of different treatment schedules on cell cycle perturbation and tumor cell growth in vitro and in xenograft tumor models.Results: MK-8776 induced an average 7-fold sensitization to gemcitabine in 16 cancer cell lines. The time of MK-8776 administration significantly affected the response of tumor cells to gemcitabine. Although gemcitabine induced rapid cell cycle arrest, the stalled replication forks were not initially dependent on Chk1 for stability. By 18 h, RAD51 was loaded onto DNA indicative of homologous recombination. Inhibition of Chk1 at 18 h rapidly dissociated RAD51 leading to the collapse of replication forks and cell death. Addition of MK-8776 from 18-24 h after a 6-h incubation with gemcitabine induced much greater sensitization than if the two drugs were incubated concurrently for 6 h. The ability of this short incubation with MK-8776 to sensitize cells is critical because of the short half-life of MK-8776 in patients' plasma. Cell cycle perturbation was also assessed in human pancreas tumor xenografts in mice. There was a dramatic accumulation of cells in S/G₂ phase 18 h after gemcitabine administration, but cells had started to recover by 42 h. Administration of MK-8776 18 h after gemcitabine caused significantly delayed tumor growth compared to either drug alone, or when the two drugs were administered with only a 30 min interval.Conclusions: There are two reasons why delayed addition of MK-8776 enhances sensitivity to gemcitabine: first, there is an increased number of cells arrested in S phase; and second, the arrested cells have adequate time to initiate recombination and thereby become Chk1 dependent. These results have important implications for the design of clinical trials using this drug combination. [ABSTRACT FROM AUTHOR]

The high mobility group A1 (HMGA1) proteins are overexpressed in pancreatic cancers. They are architectural nuclear proteins, which regulate expression of multiple genes implicated in the malignant phenotype. In this study, we hypothesized that HMG A1 silencing will promote chemosensitivity in pancreatic adenocarcinoma. We studied highly malignant pancreatic adenocarcinoma cell lines (MiaPaCa2 and PANC1). Lentiviral short-hairpin RNA (shHMGA1) expression vectors targeting HMGA1 were used for generation of lentiviral particles. Stable transfectants were developed after lentiviral transduction. Nuclear expression of HMGA1 was assayed using Western blot analysis. Chemosensitivity to gemcitabine was determined by IC50 analysis. Caspase activity was quantitated using fluorometric caspase profiling. Apoptosis was assessed by flow cytometric analysis. Lentivirus-mediated RNA interference resulted in 90% silencing of HMGA1 expression in each of MiaPaCa2 and PANC1 cell lines. HMGA1 silencing enhanced chemosensitivity to gemcitabine with an approximately 50% reduction in IC50 in each cell line. Lentivirus-mediated HMGA1 silencing promoted the activation of caspases 3, 2, 9, and 8, on exposure to gemcitabine. HMGA1 silencing resulted in reduction in Akt kinase activity. Lentivirus-mediated RNA interference of HMGA1 promoted chemosensitivity to gemcitabine in pancreatic adenocarcinoma. HMGA1 may represent a novel therapeutic target in pancreatic cancer. [Copyright &y& Elsevier]

Pancreatic cancer remains a highly chemoresistant malignancy. Gemcitabine, the most effective first-line agent available, acts by disrupting cellular replication. Caspases belong to a family of proteases that function as key components of the apoptotic death machinery. We investigated the mechanisms by which gemcitabine blocks proliferation and whether it can induce apoptosis in pancreatic cancer cells. Quiescent pancreatic cancer cells (BxPC-3) were stimulated to proliferate (10% fetal calf serum) with or without gemcitabine, PS-341 (26S proteasome inhibitor), or both. Proliferation was measured by MTT assay and apoptosis by propidium iodine staining. To determine activation of the apoptotic regulatory cell proteins, caspase-3 and cleavage of poly(ADP-ribose)polymerase (PARP) into its 85-kDa fragment were assessed by Western blotting. Gemcitabine at even low doses (10 μmol/L) significantly inhibited cellular proliferation, whereas PS-341 (10 nmol/L) had no effect. With combined treatment, PS-341 potentiated the antiproliferative effects of gemcitabine (P=0.001). At 48 hours, the apoptotic fraction was greatly enhanced by the presence of PS-341 compared with gemcitabine alone. Caspase-3 accumulated as early as 30 minutes and was associated with cleavage of PARP to its apoptotic fragment. Gemcitabine, a nucleoside analogue, may in part exert its antiproliferative effects by directing pancreatic cancer cells to a default pathway of apoptosis. 26S proteasome inhibition potentiates this effect, suggesting its potential clinical value against chemoresistance in pancreatic cancer. [Copyright &y& Elsevier]