BDNF and cancer: In tumors, paracrine and autocrine neurotrophins directly activate their receptors in cancer cells, activating PI3K/AKT, Ras/ERK, and PLCγ/PKC signaling pathways for survival and proliferation (Fig. 3).204,205 Ovarian cancer cells (OVCAR-3, SKOV-3, OVCA420, OVCA429, and OVCA433) overexpress TrkB, in fact, HGF induces TrkB expression.