TNF and breast cancer: As one of pro-inflammatory cytokines, IL-8 is associated with fatigue in breast cancer patients (Cohen et al., 2020), and increased levels of TNF-α can cause mitochondrial damage and result in fatigue (Muluye et al., 2016), Polymorphisms in TNF-α have also been reported in association with fatigue in a small longitudinal study of prostate cancer patients (Jim et al., 2012; Bower, 2014).