At the cell surface, extracellular RHAMM is required for tumour cell motility and invasion, affecting hyaluronan and growth factor-induced MAPK (ERK1, 2) signalling via associations with transmembrane hyaluronan receptors such as CD44 and protein tyrosine kinase (PTK) receptors such as PDGFR and RON [42, 43]. This evidence concerns the gene CD44 and neoplasm.