CD4 and melanoma: CD4+ T cells that express NK cell markers and cytotoxic enzymes have also been reported in human bladder cancer (Oh et al. 2020), NSCLC (Guo et al. 2018), melanoma (Kitano et al. 2013), and hepatocellular carcinoma (Zheng et al. 2017), and these CD4+ NK-like T cells have been shown to have tumor killing activity (Oh et al. 2020).