The pattern of expression of the microtubule-binding protein RHAMM/IHABP in mammary carcinoma suggests a role in the invasive behaviour of tumour cells

Intracellular hyaluronic acid binding protein (RHAMM/IHABP), which was rece ntly identified as a novel member of the microtubule-associated protein (MA P) family, has the capacity to interact not only with microtubules but also with microfilaments. The molecule, which is known to be expressed in mamma ry carcinoma cells, might, through virtue of its intracellular interactions , influence tumour cell morphology and motility. This possibility was exami ned in a series of 189 mammary carcinomas by immunohistochemistry, using a polyclonal antibody to RHAMM/IHABP. Tumours were selected to include approx imately equal numbers of consecutive grade I, II and III ductal carcinomas and invasive lobular carcinomas. Higher grade tumours had significantly low er expression of RHAMM/IHABP in the cytoplasm (p = 0.02), but significantly increased expression in trabeculae (p = 0.002) and further enhancement at the tumour island edges (p = 0.002). Tumours of infiltrating lobular type h ad stronger expression in the overall cytoplasm (p = 0.02) and trabeculae ( p = 0.08) than carcinomas of ductal type. The presence of strong trabecular expression was associated with a reduced overall survival time (p = 0.017) . These results suggest that RHAMM/IHABP expression may contribute to the m otility and invasiveness of a tumour cell sub-population in breast cancers. Copyright (C) 2001 John Wiley & Sons, Ltd.