CD44 is an integral hyaluronan receptor that can either promote or inhibit motogenic signaling in tumor cells. Rhamm is a non-integral cell surface (CD168) and intracellular hyaluronan binding protein that promotes cell motility in vitro and whose expression is strongly upregulated in aggressive tumors. The present invention describes compositions and methods for the prognosis and diagnosis of cancer by the detection of CD44/Rhamm complexes. The use of labeled Rhamm-binding agents in culture and in vivo to identify tumorigenic progenitor cells that exhibit an aggressive phenotype characterized by high Rhamm and CD44 expression is further described. Specific methods include using hyaluronan to target imaging or therapeutic agents to these progenitor tumor subsets in breast and likely other cancers.
STATEMENT OF GOVERNMENTAL SUPPORT
 This invention was made with government support under Grant number MOP-57694 awarded by the Canadian Institutes of Health Research (CIHR), under the Breast Cancer Society of Canada Translational Breast Cancer Research Unit, under Grant number DOD-PC050959 awarded by the U.S. Department of Defense, and under Contract No. DE-AC02-05CH11231 awarded by the U.S. Department of Energy. The government has certain rights in this invention.