ANALYSIS OF THE FHIT GENE AND ITS PRODUCT IN SQUAMOUS-CELL CARCINOMASOF THE HEAD AND NECK

The FHIT gene has been implicated as a tumor suppressor gene in human malignancies. To determine if FHIT alterations play a role in human sq uamous cell carcinogenesis of the head and neck (HNSCC), we examined t he gene and its product by RT-PCR, SSCP, Northern, Southern, and Weste rn blot analysis in primary HNSCC and/or HNSCC cell lines. Three of 32 tumor samples lacked detectable expression of FHIT by RT-PCR but show ed amplification of a control gene of similar size. One of 29 primary tumors and 2/9 HNSCC cell lines exhibited aberrant transcripts generat ed by RT-PCR methods using one set of 40 cycles of amplification. FHIT mRNA expression was absent in seven HNSCC cell lines but detectable i n primary keratinocytes by Northern analysis. Using specific polyclona l antiserum to the full-length I;HIT protein in immunoblot analyses, 4 /9 cell lines analysed showed no expression of pFhit, two exhibited lo w levels of expression, and three expressed a putative truncated pFhit . One of 15 tumors analysed also exhibited an overexpressed truncated protein. PCR/SSCP and Southern analysis of one cell line DNA that expr essed a truncated protein indicated that it sustained homozygous loss of FHIT exon 5. Our results suggest that alterations in FHIT at the DN A, RNA, and protein levels exist at a low but significant frequency in HNSCCs. Further studies regarding the potential biological activity o f FHIT are needed to clarify the role of this gene in HIVSCC tumorigen esis.