The ability of CSCs to form tumors at low densities is one important test for determining prospective CSC population.[52] In vivo limiting dilution assays, as the gold standard commonly used to estimate active CSC frequencies,[52] revealed knockdown of TMEM65 compromised the potential tumor‐forming ability of TNBC cells in xenograft tumor assays (Figure 7I,J). Here, TMEM65 is linked to neoplasm.