However, it has been reported previously, that in HaCaT keratinocytes and MCF-7 breast cancer cells, WDR7 siRNA knockdown reduces DND-99 staining of acidic vesicles even under steady-state conditions40; thus the degree of WDR7 requirement for V-ATPase function could be also cell-specific. This evidence concerns the gene WDR7 and breast carcinoma.