Leptin receptors are products of a single Ob-R [146] and its binding to leptin, explained in Section 3.1., promotes the expression of antiapoptotic proteins (e.g., X-linked inhibitor of apoptosis protein (XIAP)), systemic inflammation (e.g., IL6), angiogenic factors (e.g., VEGF) and hypoxia inducible factor-1α (HIF-1α), which promotes cancer cell survival, proliferation, and migration [147]. Here, IL6 is linked to cancer.