CD81 and breast cancer: Abu-Saleh et al. and colleagues (2023) concluded that CD81 knockout inhibits metastasis in vivo and vitro in breast cancer. Quagliano et al. (2020) found that CD81 knockout induces chemosensitivity in ALL. Other studies have shown that CD81 is an adverse prognostic marker in AML and multiple myeloma (MM) (Boyer et al., 2016; Paiva et al., 2012).