Our finding that Pfn1 overexpression suppresses orthotopic tumorigenicity of MDA-MB-231 cells reproduces previous results reported for another breast cancer cell line in subcutaneous xenograft models (Janke et al, 2000; Wittenmayer et al, 2004), and thus provides a further supportive evidence for the tumour-suppressive property of Pfn1 in breast cancer. This evidence concerns the gene PFN1 and neoplasm.