Background: Hyaluronan (HA) is a cell-surface glycosaminoglycan that has been implicated in cancer progression. Cells isolated from metastatic colon carcinoma (SW620) produce greater amounts of pericellular HA than cells isolated from a primary tumor (SW480). Inhibition of hyaluronan synthases (HAS) by transfection with antisense cDNA decreases HA production. Because adhesion to the extracellular matrix (ECM) is required for invasion and metastasis, we hypothesized that pericellular HA mediates adhesion to ECM proteins such as laminin, collagen, and fibronectin and that inhibition of HA production or removal of HA by digestion with hyaluronidase would impair adhesion.
Materials and methods: SW480, SW620, and antisense transfectants (SW620 cells transfected with vector alone, antisense HAS2, antisense HAS3, and both antisense HAS2 and HAS3) were assessed for adhesion to laminin, Type 1 collagen, or fibronectin-coated plates. To confirm that adhesion was mediated by HA, cells were treated with or without hyaluronidase prior to the assays.
Results: Metastatic SW620 cells adhered well to laminin; SW480 cells demonstrated 46% less adhesion (P < 0.05; Student's t test). SW620 cell adhesion to Type 1 collagen and fibronectin was >50% less than adhesion to laminin. Inhibition of HAS2 and/or HAS3 or pretreatment with hyaluronidase significantly decreased adhesion of SW620 cells to laminin (P < 0.05), suggesting that adhesion was dependent upon pericellular HA.
Conclusions: Metastatic SW620 cells that produce large amounts of pericellular HA adhered well to laminin. Inhibition of HAS2 and/or HAS3 expression, or hyaluronidase digestion of pericellular HA significantly inhibited adhesion. These data suggest that HA promotes adhesion to laminin and may thereby facilitate invasion of the basement membrane and metastasis in colon carcinoma.