Abstract 1125: Altered therapeutic response to metronomic chemotherapy in a metabolic syndrome model of mice bearing a mammary adenocarcinoma: Implication of intestinal ABC transporters

Breast cancer is one of the most prevalent and deadly cancers worldwide. Its prognosis depends on the cell type, as well as the age and comorbidities of each patient. A novel therapeutic approach is metronomic chemotherapy (MCT) characterized by chronic, low dose drug administration with therapeutic efficacy andlow or null toxicity as majoradvantages. The comorbidity that worsens cancer prognosis is metabolic syndrome (MS) characterized by obesity, insulinresistance, hyperglycemia, hypertriglyceridemia and hypercholesterolemia, and a chronic systemic inflammatory state. These conditions influence the intestinal biochemical barrier, altering the multidrug resistance-associated protein 2 (Mrp2) and P-glycoprotein (P-gp activities. Significantly, these two efflux pumps transport chemotherapeutics drugs such as cyclophosphamide (Cy). Our aim was to evaluate the effectiveness and toxicity of MCT with Cy in mice with metabolic syndrome bearing a mammary adenocarcinoma. Simultaneously, the activities of the intestinal efflux transporters were assessed. CBi male mice (5 weeks n=20/group), were fed with a chow diet (C) and a diet with 40% calories of fat (HFD) throughout the experiment. At 16 weeks, the development of MS was confirmed by biochemical and morphological parameters. The Mrp2 and P-gp activities were evaluated using the in vitro model of everted intestinal sacs. Once the MS features were settled, mice werechallenged s.c. with triple negative M-406 mammary adenocarcinoma (day 0); when the tumor was palpable, mice were distributed into 4 groups (n=8/group):GI: C no treatment, GII:C+Cy (30 mg/kg/day in drinking water), GIII: HFD no treatment and GIV: HFD+Cy. Efflux of Mrp2 substrate DNP-SG decreased 64% in HFD respect to C (P