Obesity confers risks to
cancer development and progression but the mechanisms underlying these risks remain unclear. In this study, we identify a role for the
obesity cytokine leptin, which has been implicated previously in
breast cancer development, as a determinant for the
tumor-promoting activity of cancer-associated fibroblasts (CAF) in both wild-type (WT) and K303R mutant
estrogen receptor-α (ERα)-expressing
breast cancer cells. Human CAFs stimulated a greater increase in the proliferation and migration of
breast cancer cells expressing the K303R-ERα hyperactive receptor than WT-ERα-expressing cells. A concomitant increase was seen in
leptin receptor isoform expression and activation of the
leptin signaling pathway in cells expressing K303R-ERα compared with WT-ERα, correlating with
leptin effects on cell growth, motility, and invasiveness in mutant cells.
Epidermal growth factor and other factors secreted by K303R-ERα cells stimulated CAF proliferation, migration, and subsequent
leptin secretion. Moreover, K303R-ERα expression generated a
leptin hypersensitive phenotype in vivo. Together, our results reveal a bidirectional cross-talk between
breast cancer cells and "educated" CAFs that drives
tumor progression via
leptin signaling. In elucidating a mechanism that connects
obesity and
cancer, these findings reinforce the concept that blocking
cancer-stromal cell communication may represent an effective strategy for targeted
therapy of
breast cancer.