CD44 and lip and oral cavity carcinoma: Although some previous studies have suggested that high expression of HA in both tumor and stromal cells from resected oral cancer patients may correlate with poor prognosis [11,14], these studies also confirm previous observations that proteolytic cleavage of HA by hyaluronidases and matrix metalloproteinases (MMPs) may trigger the invasion and metastasis via the receptor for hyaluronan (HA)-mediated motility (RHAMM) CD44 [18,25].