ZNF217 and breast cancer: Second, our in vitro data revealed that ectopic overexpression of the ZNF217-ΔE4 isoform in breast cancer cells leads to: (i) increased endogenous mRNA and protein levels of the ZNF217-WT isoform; and (ii) features of cell aggressiveness (increased cell proliferation, increased anchorage-independent growth and resistance to paclitaxel) previously described when ZNF217-WT is ectopically overexpressed (4, 5).