Expression of relaxin-like factor is down-regulated in human testicular Leydig cell neoplasia

In addition to their role in steroidogenesis in the male, testicular Leydig cells constitutively express large amounts of the peptide relaxin-like fac tor (RLF), also known as Ley-IL. The Leydig cell-derived RLF belongs to the insulin-like superfamily, which also includes relaxin, insulin and the ins ulin-like growth factors, and within the testis is a specific marker of Ley dig cells. Little information is available either on the regulation of gene expression or on the function of this Leydig cell-derived peptide. In the present study we have investigated the expression pattern of human RLF in p atients with rare Leydig cell hyperplasia and adenoma. The expression of bo th mRNA and protein appear to be decreased in hyperplastic Leydig cells, wh ereas in the Leydig cell adenomas studied, large central areas of the adeno ma were devoid of RLF mRNA and protein. Only Leydig cells located at the pe riphery of the adenoma displayed expression of RLF, with full agreement bet ween in-situ hybridization and immunohistochemistry. It thus appears that t he expression of the RLF gene and its products are down-regulated in Leydig cell hyperplasia and adenoma, consistent with a concomitant dedifferentiat ion of these cells.