PFN1 and breast cancer: Next, to determine the effect of Pfn1 perturbation on the total cellular PIP2 pool, we performed biochemical PIP2 lipid dot-blot assay with lipids extracted from both normal (MCF10A, a nontumorigenic immortalized mammary epithelial cell line) and breast cancer cell lines (MDA-231, BT-474)—all three cell lines showed reduced total PIP2 content when Pfn1 expression was silenced (Fig. 2H; knockdown of Pfn1 expression in MCF10A cells is shown in Fig. S1).