GPNMB and cancer: Our group reported that GPNMB is actively transcribed when macrophages are co-cultured with cancer cells (Solinas et al. 2010); furthermore, it is preferentially expressed by M2 macrophages (Liguori et al. 2021; Yu et al. 2016) and TAMs in mouse experimental tumors are positive for GPNMB (Liguori et al. 2021).