Obesity enhances carcinogen 7, 12-Dimethylbenz [a] anthracene -induced tumorigenesis in vitro and in vivo.

Growing body of evidence shows that extra adiposity influences on the progression of multiple cancers, including breast cancer. The aim of this study is to investigate whether obesity correlates with mammary tumor development in vitro and in vivo. We found that obesity-related mediators, 3T3-L1 adipocyte conditioned medium, enhanced formation of cancerous foci induced by the carcinogen 7,12-Dimethylbenz[a]anthracene (DMBA) in NIH/3T3 fibroblasts, in vitro. Additionally, we tested the effect of obesity in mouse model of DMBA-induced breast cancer. C57BL/6J female mice were fed a low fat (LF), or high fat (HF) diet, and DMBA was administered by oral gavage (LF plus DMBA [LFD] and HF plus DMBA [HFD]). Our results indicated that HFD mouse developed a tumor which weight was 169mg, whereas the LFD mouse developed a tumor weight of 77mg. Histological analysis of the mammary tumor from HFD group showed morphological aggressiveness and multiple cell type infiltration compared to LFD group. The epididymal adipose tissue from the DMBA groups showed more macrophage infiltration, polarized towards an M1 phenotype compared to the non-DMBA mice. HF mice showed less accumulation of M2 macrophages in the adipose tissue. In summary, obese mediators enhanced DMBA induced tumorigenesis in vitro and in vivo.