Mechanism of MTA1 Protein Overexpression-linked Invasion: MTA1 REGULATION OF HYALURONAN-MEDIATED MOTILITY RECEPTOR (HMMR) EXPRESSION AND FUNCTION

Even though the hyaluronan-mediated motility receptor (HMMR), a cell surface oncogenic protein, is widely up-regulated in human cancers and correlates well with cell motility and invasion, the underlying molecular and nature of its putative upstream regulation remain unknown. Here, we found for the first time that MTA1 (metastatic tumor antigen 1), a master chromatin modifier, regulates the expression of HMMR and, consequently, its function in breast cancer cell motility and invasiveness. We recognized a positive correlation between the levels of MTA1 and HMMR in human cancer. Furthermore, MTA1 is required for optimal expression of HMMR. The underlying mechanism includes interaction of the MTA1·RNA polymerase II·c-Jun coactivator complex with the HMMR promoter to stimulates its transcription. Accordingly, selective siRNA-mediated knockdown of HMMR in breast cancer cells substantially reduces the invasion and migration of cells. These findings reveal a regulatory role for MTA1 as an upstream coactivator of HMMR expression and resulting biological phenotypes. Although MTA1 is overexpressed in advanced human cancer, its role in cancer invasion and migration needs to be elucidated. MTA1 transcriptionally stimulates expression of the hyaluronan-mediated motility receptor (HMMR) and consequently regulates cancer invasion and migratory function. HMMR is a mediator of MTA1-mediated invasion and motility. This is the first report connecting MTA1 with HMMR expression and function.