ID1 and breast cancer: Moreover, we demonstrated that E6/E7 onco-proteins of HPV type 16 convert non-invasive breast cancer cells to an invasive phenotype (Yasmeen et al, 2007a); this is accompanied by an overexpression of Id-1, which regulates cell invasion and metastasis of human breast cancer cells (Desprez et al, 1998; Fong et al, 2003).