PTK2 and fibrosarcoma: Additionally, both HA fragments and low molecular weight HA (15–40 kDa) have been shown to have the capacity to bind RHAMM directly [93,94,95], and investigators have reported that in fibrosarcoma cells low molecular weight HA increases adhesion via RHAMM-mediated focal adhesion kinase (FAK) and ERK1/2 signaling [93], while in endothelial cells HA fragments bind to RHAMM and stimulate tyrosine phosphorylation of p125FAK, paxillin and p42/44 ERK associated with induction of adhesion and proliferation [95].