Acrp30 inhibits leptin-induced metastasis by downregulating the JAK/STAT3 pathway via AMPK activation in aggressive SPEC-2 endometrial cancer cells

Obesity is a well-established risk factor for endometrial cancer, due inpart to the adipokines generated by adipose tissue, such as adiponectin (alsoknown as Acrp30) and leptin, which are associated with many endocrine-relatedcancers. Recent reports suggested that Acrp30 inhibits leptin-stimulated cellproliferation in HEC-1A and RL95-2 endometrial cancer cell lines, and that theserum leptin/Acrp30 ratio plays an important role in endometrial cancer development.We explored whether Acrp30 could reverse the leptin-induced metastasis phenotypein the SPEC-2 endometrial cancer cell line. Transcripts for Acrp30 receptors (AdipoR1and AdipoR2) and leptin receptor (Ob-Rb) were detected by quantitative real-timeRT-PCR (qRT-PCR) in six endometrial cancer cell lines. Leptin (1 µg/ml) treatmentstimulated SPEC-2 cell proliferation by inducing cell cycle arrest and apoptosis,while Acrp30 (10 µg/ml) treatment inhibited the growth of SPEC-2 cells. Importantly,Acrp30 was able to inhibit leptin-induced SPEC-2 cell proliferation. Leptin promotedSPEC-2 cell invasion in a Matrigel transwell assay, while Acrp30 partly suppressedthe invasion stimulated by leptin. To investigate the molecular mechanism underlyingthis phenomenon, we monitored the AMPK and JAK/STAT3 signaling pathways by westernblotting and cell immunofluorescence. Acrp30 reduced leptin-induced STAT3 phosphorylationand nuclear translocation via activation of the MAPK pathway. AG490 (JAK/STAT3inhibitor) reduced MMP-2 and MMP-9 protein levels in cells treated with leptin,while IL-6 (JAK/STAT3 stimulator) and Compound C (AMPK inhibitor) elevated MMP-2and MMP-9 protein levels in cells treated with Acrp30. In conclusion, we demonstratedthat Acrp30 effectively reversed the invasion stimulated by leptin, and AMPK andJAK/STAT3 pathways mediated the invasive phenotype of SPEC-2 cells.