Decrease in the expression of a novel TGF beta1-inducible and ras-recision gene, TSC-36, in human cancer cells.

TSC-36, a TGF beta1-inducible gene, encodes a polypeptide that shows significant similarity to SPARC (secreted protein rich in cysteine), and follistatin, an activin-binding protein. The expression of the TSC-36 gene was reported to be extinguished in v-ras-transformed mouse fibroblastic cells, and also was found also to be abrogated in cells transformed with v-myc. The level of expression was, however, not affected in cells transformed with v-src, v-abl, or v-raf. The TSC-36 cDNA was first isolated from mouse cells, and recently its rat and human homologues have been reported which show striking similarity with each other. In various human tumor cells, TSC-36 mRNA was almost undetectable. TSC-36 mRNA was detected in various mouse organs, but its level was the highest in the lung. TSC-36 mRNA level was the highest in the lung among mouse organs, and on in situ hybridization, the TSC-36 transcript was detected in the alveolar epithelium but not in the bronchial epithelium. These features suggest possible usage of TSC-36 as one of the markers in human tumors.