BDNF and ovarian cancer: Cervical cancer and ovarian cancer promote their own PNI via the release of neurotrophins (Allen et al., 2018; Long et al., 2018), axonal guidance molecules (Madeo et al., 2018), and exosomes (Madeo et al., 2018; Lucido et al., 2019; Vermeer, 2019; Kovacs et al., 2020).