CD44 and neoplasm: As CD73 is overexpressed in tumor-initiating cells (TIC) to promote stemness (Katsuta et al., 2016; Song et al., 2017), and that TIC rely on OXPHOS to support tumorigenesis (Snyder et al., 2018), we next evaluated the impact of CD73 on the metabolic fitness of putative TIC (ALDHHigh CD44+ CD24-) derived from MDA-MB-231 cell cultures (Figure 2—figure supplement 2C).