MTA1 and breast cancer: MTA1 was initially isolated from highly invasive breast cancer cell lines, and its expression was associated with cancer progression and metastasis in a variety of human cancers [62–64] However, the factor responsible for upregulating MTA1 in cancer was unknown until Mazumdar et al. found that heregulin, a ligand for HER3, was capable of inducing MTA1 expression [65].