Differential expression of thymosin genes in human tumors and in the developing human kidney

Thymosins β 4 and β 10 are 2 structurally related polypeptides originally defined in the rat immune system. To date, no truly unambiguous functions have been formally ascribed to these small (<4.9 kDa) acidic proteins. Previous research has demonstrated relationships between expression of these genes and cell growth/differentiation. These observations prompted the present study which has used cDNA and synthetic oligonucleotide probes in combination with high‐performance liquid chromatography (HPLC) to examine the differential expression of these 2 genes in normal and neoplastic human tissues and in the developing human kidney. Low levels of β 4 and β 10 mRNA species prevailed in normal tissues; in contrast, these gene transcripts were notably more abundant in malignant renal tumors and in the normal human embryonic kidney. These findings show that the thymosin β 4 and β 10 genes are constitutively expressed at higher levels in embryonic/neoplastic as compared to normal/benign tissues and that thymosin in β 10 in particular may be a new molecular marker for renal‐cell carcinoma as well as other malignancies.