Hsps expressed on the cell surface have been associated with
tumor invasiveness and used as targets for molecular surveillance. The present study utilized four human
oral squamous cell carcinoma cells lines, SCC-4, SCC-9, SCC-15, SCC-25, the murine
epidermoid carcinoma cell line LL/2, and primary cultures of human gingival fibroblasts to assess the cell surface expression of
colligin/Hsp47, a proposed marker for
malignancy. Immunoprecipitation studies following
protein crosslinking revealed that Hsp47 was associated with a number of
membrane proteins including the
tetraspanin CD9. Cytometric analyses were performed to determine the distribution of cell surface
colligin/Hsp47 during the phases of the cell cycle. These studies showed that
colligin/Hsp47 was not limited to any phase of the cell cycle in
epidermoid carcinoma cells. Boyden chamber
tumor invasion assays and
colloidal gold migration assays utilizing a reconstituted basement membrane (
Matrigel),
collagen type I, and
laminin-5 substrates revealed that cell lines expressing constitutive high levels of
colligin/Hsp47 manifested the lowest invasion and migration indices. The incorporation of
antibodies against Hsps into the migration and invasion assays, likewise, increased the invasion indices and the phagokinetic migration indices. These data indicate that
colligin/Hsp47 is anchored to the cell membrane in a complex with CD9 where it moderates
tumor cell invasion and motility possibly by acting as a
serpin protein inhibitor or as a receptor for
collagen.