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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Adenocarcinoma, Animals, Bone Marrow Cells, Cell Differentiation, Diphosphonates, Disease Models, Animal, Humans, Imidazoles, Mice, Mice, Inbred C57BL, Myeloid Cells, Pancreatic Neoplasms, Tumor Microenvironment, Up-Regulation, Zoledronic Acid.
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Does pancreatic adenocarcinoma induce bone marrow mobilization of myeloid-derived suppressor cells which promote primary tumor growth? Context: Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immunosuppressive cells that are upregulated in cancer. Little is known about the prevalence and importance of MDSC in pancreas adenocarcinoma (PA). Peripheral blood, bone marrow, and tumor samples were collected from pancreatic cancer patients, analyzed for MDSC (CD15(+)CD11b(+)) by flow cytometry and compared to cancer-free controls. The suppressive capacity of MDSC (CD11b(+)Gr-1(+)) and the effectiveness of MDSC depletion were assessed in C57BL/6 mice inoculated with Pan02, a murine PA, and treated with placebo or zoledronic acid, a potent aminobisphosphonate previously shown to target MDSC. The tumor microenvironment was analyzed for MDSC (Gr1(+)CD11b(+)), effector T cells, and tumor cytokine levels. Patients with PA demonstrated increased frequency of MDSC in the bone marrow and peripheral circulation which correlated with disease stage. Normal pancreas tissue showed no MDSC infiltrate, while human tumors avidly recruited MDSC. Murine tumors similarly recruited MDSC that suppressed CD8(+) T cells in vitro and accelerated tumor growth in vivo. Treatment with zoledronic acid impaired intratumoral MDSC accumulation resulting in delayed tumor growth rate, prolonged median survival, and increased recruitment of T cells to the tumor. This was associated with a more robust type 1 response with increased levels of IFN-γ and decreased levels of IL-10.
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MDSC are important mediators of tumor-induced immunosuppression in pancreatic cancer. Inhibiting MDSC accumulation with zoledronic acid improves the host anti-tumor response in animal studies suggesting that efforts to block MDSC may represent a novel treatment strategy for pancreatic cancer. Final Decision: yes