Although our matrigel invasion data successfully demonstrate that Pfn1 is a negative regulator of the intrinsic invasiveness MDA-MB-231 breast cancer cells, because of heterogeneity of tumour cells, it will be valuable to extend these studies to both primary cancer cells and other invasive/noninvasive breast cancer cell lines with different endogenous levels of Pfn1. Here, PFN1 is linked to breast cancer.