Laminin-γ2 overexpression in head-and-neck squamous cell carcinoma

To identify molecular markers for the progression of head-and-neck squamous cell carcinoma (HNSCC), we used RNA arbitrarily primed (RAP) PCR to determine the qualitative and quantitative differences in gene expression between normal epithelial cells, those derived from dysplastic oral mucosa and invasive and metastatic HNSCC. Three differentially expressed DNA fragments (RAP20, RAP21, RAP26) that were upregulated in a tumor cell line (T45) were identified as being regions of the γ2 subunit of human laminin-5. Northern blot analysis of total cellular RNA revealed over-expression of these transcripts in 6 of 7 HNSCC cell lines compared with normal epidermal keratinocytes. In contrast, no differences were observed in HeLa (cervical carcinoma) or HCT116 (colon carcinoma) cells. Immunostaining of HNSCC cells derived from primary (HN4) and metastatic (HN 12) tumors indicated elevated levels of endogenous laminin-γ2 protein. Furthermore, HNSCC tissues demonstrated strong laminin-γ2 staining, particularly in the peripheral basaloid cells of tumor islands at the invasion front. In contrast, only minimal staining of laminin-γ2 was detected in basal cells of the normal epithelium. The data indicate that laminin-γ2 is frequently overexpressed in HNSCCs and derivative cell lines and that its overexpression is likely to be useful as a marker of head-and-neck squamous malignancy.