Screening for MEN1 tumor suppressor gene mutations in sporadic pituitary tumors.

The molecular pathogenesis of the majority of sporadic pituitary tumors is largely unknown. Pituitary adenomas can develop sporadically or as a part of multiple endocrine neoplasia type 1 (MEN1). The MEN1 is thought to be a tumor suppressor gene based on loss of heterozygosity (LOH) for polymorphic markers on 11q13 in tumors of the pancreas, parathyroid, and pituitary. Most patients with familial and sporadic MEN1 carry germ-line mutations in the MEN1 gene. Two previous studies and recently a third one have analyzed mutations by sequencing the MEN1 gene in sporadic pituitary tumors but yielded conflicting results. This study was to investigate and clarify the potential role of MEN1 mutations, in sporadic pituitary adenomas. First, we examined 59 sporadic pituitary adenomas by analyzing LOH on 11q13 in the MEN1 minimal interval with microsatellite analysis. We found 3 tumors with LOH in 1 to 4 polymorphic markers in the MEN1 region. Sequencing analysis did not reveal any mutations in the coding region of the MEN1 gene. However, we found 3 polymorphisms, one of which was a novel CAC to CAT transition encoding His433His, in exon 9. The data show that while LOH occurs in some sporadic pituitary tumors, inactivating mutations of the tumor suppressor gene MEN1 are rare. These results also suggest there may be another additional tumor suppressor gene at this locus which is involved in the pathogenesis of sporadic pituitary neoplasms.