Leptin receptor is involved in STAT3 activation in human colorectal adenoma

The possible role of leptin in colorectal tumors has been investigated in previous studies; however, to date, the conclusions remain under debate. Therefore, we investigated the serum leptin levels in colorectal adenoma patients. In addition, expression of the leptin receptor, and the leptin receptor-mediated signaling pathways were investigated in biopsy specimens collected from human patients with colorectal adenoma. No significant difference in the mean serum leptin level was observed between the colorectal adenoma patients and the control subjects; however, increased expression and activation of the leptin receptor, as indicated by findings such as the phosphorylation of Tyr 1141, was observed in the colorectal adenoma tissues. In addition, activation of the JAK/STAT signaling pathway mediated by the leptin receptor and increased transcriptional regulation of downstream target molecules were observed in colorectal adenomas compared with the non-adenoma tissues. These results indicate STAT3-mediated leptin receptor signaling pathways may be activated in human colorectal adenomas. (Cancer Sci 2011; 102: 367-372)