PTPN1 and neoplasm: The mechanism by which adiponectin antagonizes leptin in promoting tumor is not clear, but studies have found that adiponectin can inhibit the activation of ERK and AKT in the leptin signaling axis; increase the expression and activity of protein tyrosine phosphatase 1B (PTP1B), a physiological inhibitor of leptin signaling, and block the growth of breast cancer cells induced by leptin (156).