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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]

Tumour-associated macrophages have been implicated in pancreatic ductal adenocarcinoma (PDAC) therapy response and Extracellular vesicles (EVs) shed by macrophages might have a role in this process. Here, we demonstrated that large EVs released by anti-inflammatory human macrophages decreased PDAC cellular sensitivity to gemcitabine. Using proteomic analysis, chitinase 3-like-1 (CHI3L1) and fibronectin (FN1) were identified as two of the most abundant proteins in the cargo of macrophages-derived EVs. Overexpression of CHI3L1 and FN1, using recombinant human proteins, induced PDAC cellular resistance to gemcitabine through ERK (extracellular-signal-regulated kinase) activation. Inhibition of CHI3L1 and FN1 by pentoxifylline and pirfenidone, respectively, partially reverted gemcitabine resistance. In PDAC patient samples, CHI3L1 and FN1 were expressed in the stroma, associated with the high presence of macrophages. The Cancer Genome Atlas analysis revealed an association between CHI3L1 and FN1 gene expression, overall survival of PDAC patients, gemcitabine response, and macrophage infiltration. Altogether, our data identifies CHI3L1 and FN1 as potential targets for pharmacological inhibition in PDAC. Further pre-clinical in vivo work is warranted to study the possibility of repurposing pentoxifylline and pirfenidone as adjuvant therapies for PDAC treatment. [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]