Although both the anti- and pro-tumor effects of irisin seem to involve the PI3K/AKT pathway, the underlying mechanism that might explain these discrepancies remains unknown (Moon and Mantzoros, 2014; Gannon et al., 2015; Shao et al., 2017; Shi et al., 2017; Liu et al., 2019). The gene discussed is FNDC5; the disease is neoplasm.