Mutational analysis of StAR gene in adrenal tumors

Adrenal adenomas and carcinomas are mostly monoclonal, suggesting that a genetic alteration in a progenitor cell may contribute to their development. However, the molecular pathogenesis of these tumors still remains unclear. It has been already excluded that activating mutations of the ACTH receptor or of G protein stimulator alpha sub-units, affecting cAMP pathway, is involved in the tumorigenesis. Therefore, this work has been focused on post-transductional (ACTH) signal alterations and in particular on the mutational analysis of the Steroid Acute Regulatory protein (StAR) gene to verify whether somatic mutations or genomic polymorphisms of this gene may be correlated with adrenal tumorigenesis. Tissue DNA was extracted from 40 functional and non-functional adrenocortical tumors that were removed from patients aged between 17 and 72 years (mean 43 +/- 4). Blood DNA was obtained from 24 patients (aged between 26 and 70 years) affected by adrenal tumors and from 100 healthy subjects without radiological and clinical evidence of adrenal masses, aged between 25-35 years (90 Caucasians and 10 Africans). The DNA was used as the template for the amplification of the StAR gene using the polymerase chain reaction. The amplified DNA of each exon of the StAR gene was purified and sequenced in automatic sequenciator. With the exception of exon 5 showing in codon 203 an homozygous missense mutation, the sequence of the other exons of the StAR gene resulted normal in all tumors studied. The same homozygous mutation (Asp203Ala) was observed in the sequence of exon 5 performed on genomic DNA of the 24 affected patients and in the control subjects. The homozygosity of the mutation observed in all patients (either in tissue or blood samples) and in control subjects, independently of their ethnic origin, led us to suggest that the Asp203Ala cannot be considered as mutation or as polymorphism, but that it must be considered as a mistake in the sequence entered in the Genbank, which needs to be modified accordingly. These data, and those up to now reported in the literature, allow us to suggest that mutations of the gene coding for the protein involved in the initial step of the steroidogenesis could not be considered as a possible cause for the development of adrenal tumors.