TP53 and cancer: On the other hand, we do not know why cancer cells, such as MDA-MB-231 cells, have very low but detectable levels of miR-96/182 expression even in the absence of intact p53 (i.e., leaky expression of miR-96/182 in the parental cells and shp53 cells), whereas normal epithelial cells have undetectable levels of miR-96/182 upon the loss of intact p53.