TSPAN1 and breast cancer: TM4SF includes several types of proteins possessing the four transmembrane-helix structure, such as the classical TM4SF (tetraspanin) and MARVEL-domain containing proteins, and such proteins have been linked to breast cancer development and progression (Bouchagier et al., 2014; Jiang et al., 2019; Lara-Lemus, 2019).