LIF and cancer: Distinct subpopulations of CAFs are especially proficient in secreting a multitude of pro-stemness paracrine factors, including interleukin (IL)-6, IL-8, leukemia inhibitory factor (LIF), IGF-2, PGE-2, C-C motif chemokine ligand (CCL)-2, and nodal [27,32,33,34,35,36,37], thereby promoting the conversion of cancer cells into CSCs or supporting the self-renewal and the stemness properties of existing CSCs in tumors.