Syndecan-1 (CD138), a cell-surface
heparan sulfate proteoglycan, is involved in cell-cell, cell-matrix interaction and
growth factor binding. Loss of expression of
syndecan-1 in
tumor cells leads to decreased intercellular cohesion, increased potential for
tumor invasiveness, and metastatic spread. Furthermore, induction of
syndecan-1 expression in the
tumor stroma has been postulated to promote
tumor angiogenesis via its binding to
growth factors such as
basic fibroblast growth factor. Although
syndecan-1 expression within
tumor cells has been investigated in
head and neck squamous cell carcinoma, stromal expression has not been studied in detail. We analyzed 38 cases of
head and neck squamous cell carcinoma by immunohistochemical staining for
syndecan-1 expression within the stroma. The expression of
syndecan-1 within
tumor cells of various histologic grades of differentiation,
squamous cell carcinoma in situ cells, and benign squamous epithelium was also determined. Variable levels of diminished
syndecan-1 expression were noted within the dysplastic cells of 9 of 16 (60%)
squamous cell carcinoma in situ lesions and in all 38 (100%) invasive
squamous cell carcinoma. In general, higher levels of
syndecan-1 expression were observed in the well-differentiated
tumors, in contrast to significant reduction of expression seen in poorly differentiated
tumors.
Syndecan-1 expression was observed within the stroma (in fibroblasts) surrounding infiltrating
carcinoma cells in 28 of 38 (74%) cases. The intensity of
syndecan-1 staining within the stroma showed generally an inverse correlation with the degree of
tumor cell differentiation.
Syndecan-1 expression was not detected in the stroma beneath normal squamous epithelium or adjacent to areas of
squamous cell carcinoma in situ. We conclude that induced expression of
syndecan-1 in the stroma surrounding
tumor cells of invasive
head and neck squamous cell carcinoma is a frequent event. The increased stromal
syndecan-1 expression, coupled with its loss from the surface of
carcinoma cells, may contribute to
tumor cell invasion and the development of
metastases.