Bloqueio simultâneo da angiogênese pelas vias de sinalização PI3K e MAPK/AKT/mTOR após tratamento com metformina e LY294002 no câncer de mama

Abstract

Introduction: Hypoxia is a known adverse factor to cancer treatment, able to activate the signaling pathways PI3K and AMPK/Akt/mTOR, the two major pathways involved in the angiogenesis process. This process is regulated by many factors, being the most important factors the Hypoxia-Inducible Factor-1α (HIF-1α) and Vascular Endothelial Growth Factor (VEGF). Metformin has demonstrated its ability to reduce the incidence of cancer in diabetic patients with positive results especially in breast cancer, inhibiting cell growth by AMPK/Akt/mTOR signaling pathway. Likewise, LY294002 is the major inhibitor of PI3K/AKT/mTOR signaling pathway that has anti-angiogenic properties, capable to reduce the release of growth factors such as VEGF. The treatment with metformin in addition to the inhibitor LY294002 in both normal oxygen and hypoxia conditions, as well as the action in the process of angiogenesis in canine mammary tumors is unprecedented. Objectives: To evaluate the influence of metformin and LY294002 inhibitor treatment in tumor angiogenesis as a therapeutic strategy in mammary tumors in a in vitro and in vivo study. Material and Methods: In the in vitro study, we analyzed the cell viability of canine mammary tumor cell lines CMT-U229 (benign mixed tumor) and CF41 (metastatic carcinoma) before and after treatment with metformin and/or LY294002 by MTT assay. The cell cycle distribution was analyzed by flow cytometry flow, protein and gene expression of VEGF and HIF-1α by immunohistochemistry and RT-PCR, respectively. All experiments were performed in normal oxygen conditions and under hypoxia by the addition of cobalt chloride (CoCl2). For the in vivo study, CF41 cells were implanted in 20 female mice BALB / c nude nude. After 28 days of treatment with metformin and LY294002, it was analyzed micro vessel density by CD31 expression by immunohistochemistry as well as gene and protein expression of HIF-1α and VEGF in the tumor tissue. Results: The treatment with metformin and LY294002 was able to reduce the cellular viability after 24 hours. The protein and gene expression of HIF-1α and VEGF decreased after treatment with metformin and LY294002, both in normal oxygen conditions and hypoxia. In the in vivo study, there was a decrease in tumor size, protein and gene expression of HIF-1α and VEGFA, in addition to the decreasing of CD31 expression after all treatments. Conclusions: Our results demonstrated the effective action of metformin and LY294002 inhibitor in controlling the angiogenesis process in mammary tumors by the angiogenic factors VEGF and HIF-1α.