ICOSLG and cancer: Its counter ligand inducible co-stimulator ligand (ICOSL) can be found in professional APCs such as dendritic cells (DCs), B lymphocytes, as well as some cancer cells (e.g., implanted-transfected tumors) (Aspord et al., 2013; Le et al., 2016; Martin-Orozco et al., 2010; Schreiner et al., 2003; Wang et al., 2012).