Beige adipocytes contribute to breast cancer progression

Adipocytes are the main stromal cells in the mammary microenvironment, and crosstalk between adipocytes and breast cancer cells may play a critical and important role in cancer maintenance and progression. Tumor‑induced differentiation to beige/brown adipose tissue is an important contribution to the hypermetabolic state of breast cancer. However, the effect of epithelial cell‑beige adipocyte communication on tumor progression remains unclear. To contribute to the understanding of this phenomenon, we characterized components present in conditioned media (CM) from beige adipocytes (BAs) or white adipocytes (WAs), and evaluated the effects of BA‑ and WA‑CM on both adhesion and migration of tumor (LM3, 4T1 and MC4‑L1) and non‑tumor (NMuMG) mouse mammary epithelial cell lines. Additionally, we analyzed the expression of ObR, CD44, vimentin, MMP‑9, MCT1 and LDH in tumor and non‑tumor mouse mammary epithelial cell lines incubated with BA‑CM, WA‑CM or Ctrol‑CM (control conditioned media). 3T3‑L1 preadipocytes differentiated into beige adipocytes upon PPARγ activation (rosiglitazone) displaying characteristics that morphologically resembled brown/beige adipocytes. Levels of UCP1, CIDEA, GLUT4, leptin, MCT4 and FABP4 were increased, while adiponectin, caveolin 1 and perilipin 1 levels were decreased in BAs with respect to WAs. Tumor cell lines revealed lower cell adhesion and increased cell migration after incubation with BA‑ and WA‑CM vs. Ctrol‑CM. ObR and MMP‑9 in MC4‑L1 cells were significantly increased after incubation with BA‑CM vs. WA‑ and Ctrol‑CM. In addition, MC4‑L1 and LM3 cells significantly increased their migration in the presence of BAs, suggesting that new signals originating from the crosstalk between BAs and tumor cells, could be responsible for this change. Our results indicate that beige adipocytes are able to regulate the behavior of both tumor and non‑tumor mouse mammary epithelial cells, favoring tumor progression.