Rearrangement of squamous cell carcinoma antigen genes--detection of SCCA fusion transcripts.

Squamous cell carcinoma antigen (SCCA), a member of the serine protease inhibitor (serpin) family, is a tumor-associated antigen and a serological marker for squamous cell carcinomas (SCC). Elevated serum levels are correlated with the clinical stage of the disease. Gene cloning has previously revealed two tandemly arrayed genes, SCCA1 and SCCA2. Using RT-PCR, an SCCA1/A2 transcript was identified in 6 out of 8 cell lines and the reciprocal SCCA2/A1 transcript was identified in 6 out of 8 analysed cell lines. Southern blot analysis showed an aberrant band pattern in 3 out of 5 cell lines. The cell lines demonstrating a normal band pattern corresponded to the cell lines where no fusion transcript was detected using PCR. Complex binding studies show that SCCA1/A2 binds to cathepsin G but not to cathepsin L, indicating that the SCCA1/A2 fusion protein has the specificity of SCCA2, but the transcription may be regulated as that of SCCA1. SCCA2/A1 reacts in the opposite way. The clinical relevance of these fusion transcripts is not yet known. Studies using primary tumours are underway to elucidate if these fusion transcripts are tumour specific and if they might be used as a diagnostic and prognostic marker for SCC.