IRS1 and breast carcinoma: This effect of uPA‐PAI‐1‐primed neutrophils on the proliferation of breast cancer cells was largely dependent on NE which is thought to degrade insulin receptor substrate 1, a key regulator of phosphoinositide 3‐kinase, and upregulate MAPK activity, ultimately stimulating tumor cell proliferation (Chen etal, 2004; Houghton etal, 2010).