Abstract 77: Caloric restriction mimetics prevent tumor progression by tumor microenvironment remodeling

Abstract

Abstract The only non-pharmacological intervention known to date to alleviate the age-related deleterious conditions is caloric restriction (CR). We have previously reported that CR induces metabolic and signaling changes that affect the tumor microenvironment preventing mammary tumors growth and metastases. Despite the beneficial effects of CR, it is not feasible to maintain long-term dietary restriction in humans. Based on this, investigators have been focused on the discovery of CR mimetics that evoke some of the benefits of CR without an actual reduction in the calorie intake. Metformin (MET) is an anti-diabetic and a well-known CR mimetic; while Orlistat (OR) is an anti-obesity drug which has also antitumor properties. In this study we used 4T1, a highly metastatic breast cancer, and the B16F10 melanoma mouse models. At first, we evaluated the effects of CR and MET alone. Then, we investigated whether the combination of MET+OR will enhance the CR mimetic properties of MET alone. Our overall hypothesis is that CR mimetics decrease tumor progression by affecting extracellular matrix, epithelial-to-mesenchymal transition (EMT) and inflammation. Briefly, 8-weeks old female mice were fed with normal diet (ND) or 40% CR and received vehicle, MET (in drinking water, 3mg/ml), OR i.p. injection (240mg/kg/d) or MET+OR. After 5 weeks on diets, 4T1 or B16F10 cells were injected into BALB/c or C57BL6 mice respectively; diets and treatments continued for the remainder of the experiment. CR and Mimetics treated-mice had a reduction in body weight (p<0.01) and adiposity (p<0.05) without any signs of toxicity. CR and mimetics treatments reduced tumor growth (p<0.01), microvessel density, total vessel length (p<0.01) and decreased the number and size of spontaneous lung metastases (p<0.01). Also, CR and mimetics tumor bearing mice had significantly lower levels of intra-tumor uPA, MMP-9 and TGF-β. Moreover, CR and mimetics-treated mice had lower levels of circulating insulin, leptin and increased levels of adiponectin and fibroblast growth factor 21 (FGF21) (p<0.01). In a cell invasion assay, we also showed that MET+OR resulted in a significantly reduction on invasion (p<0.01). It is known that the loss of E-Cadherin promotes metastasis. We observed that CR and treated-mice had greater expression of E-Cadherin compared to the controls; in particular MET+OR had higher expression compared to either agent alone. NFĸB activation, the linker between inflammation and cancer, induces the expression of genes that promote a mesenchymal phenotype. We found that the MET+OR decreased phosphorylated P65S536 in 4T1 tumors, which corresponded with a decreased expression in COX-2 and Bcl-2; and an increased expression of P53 and cleaved caspase-3. Our results suggest that CR and MET+OR reduce tumor growth and metastases may in part be due to NFĸB inhibition and by remodeling the ECM, preventing the loss of E-Cadherin and the local invasion. Citation Format: Anirudh Goyal, Shakir M. Saud, Jessica D. Bedele, Mariana S. De Lorenzo. Caloric restriction mimetics prevent tumor progression by tumor microenvironment remodeling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 77.