AMPLIFICATION-INDEPENDENT OVEREXPRESSION OF THYMOSIN BETA-10 MESSENGER-RNA IN HUMAN RENAL-CELL CARCINOMA

The structurally related small (< 5 kD) polypetides, namely thymosins beta-4 and beta-10, were originally defined in the rat immune system. Previously it was Shown that both the beta-4 and beta-10 genes are con stitutively expressed at higher levels in neoplastic human kidney. Als o, it was shown that human embryonic kidney contained more of these pr oteins than the adult tissue. The present study used a human thymosin beta-10 cDNA to examine the possibility that overexpression of the bet a-10 mRNA in renal cell carcinoma was due to gene amplification. South ern blot analysis of genomic DNA extracted from normal and neoplastic tissue indicated no amplification of the thymosin beta-10 gene in RCC. No amplification or rearrangements were found in the human RAR-alpha gene in normal versus RCC tissue. Decreased expression of both the thy mosin beta-4 and beta-10 proteins in the normal adult human kidney was found to be derived from a corresponding decrease in levels of the co gnate mRNAs. These findings suggest that the thymosin beta-10 gene is deregulated in renal cell carcinoma.