Frequent loss of KAI1 expression in squamous and lymphoid neoplasms - An immunohistochemical study of archival tissues

The metastasis suppressor gene KAI1 was identified by its ability to inhibi t the formation of pulmonary metastases in experimental models for prostati c carcinoma. Down-regulation of this gene may be correlated with the invasi ve phenotype in melanomas and colon and bladder carcinomas and with the met astatic phenotype in carcinomas of the lung, breast, prostate, and pancreas . The goal of our study was to establish an immunohistochemical method to d etect KAI1 expression in archival tissues. Using cell lines with known KAI1 levels and paraffin-embedded KAI1 positive tissues as controls,we observed strong membrane staining in lymphoid follicular centers and squamous epith elia. We then demonstrated the utility of our assay by studying KAI1 expres sion in 34 lymphoid and 57 squamous lesions. All eight reactive lymph nodes were KAI1 positive. In contrast, three of 13 follicular small cleaved and five of 13 diffuse large cell lymphomas were KAI1 negative. Seventy-nine pe rcent (37 of 47) of invasive squamous cell carcinomas from the lung (n = 15 ), head and neck (n = 18), and cervix (n = 14) showed extensive KAI1 down-r egulation. Loss of KAI1 expression was also found in a subset of 10 high-gr ade cervical dysplasias. Our data show that (i) immunohistochemistry is a s uitable technique for evaluating KAI1 expression in archival tissues; (ii) KAI1 was not expressed in a subset of both low-grade and high-grade lymphom as; and (iii) there was extensive down-regulation of KAI1 in squamous cell carcinomas, suggestive of an important role of the gene in the suppression of invasion in these malignancies.