Loss of heterozygosity at the retinoblastoma locus in human pituitary tumors.

Recent studies using knockouts of the Retinoblastoma (Rb) gene by homologous recombination in transgenic mice have revealed that a high frequency of heterozygous animals develop pituitary tumors associated with loss of heterozygosity (LOH) at the Rb locus. The authors have determined the frequency of LOH at the Rb locus in 42 benign human pituitary tumors. Polymerase chain reaction- (PCR) amplification of polymorphic regions in introns 17 and 20 of the human Rb gene was used to detect heterozygosity in pituitary tumor DNA and matched control DNA samples. The PCR assay was informative in 42 of 48 pituitary tumors examined, and no allelic deletion of Rb was detected in any of the tumors. These studies confirmed a recent report that LOH at the Rb locus is rare in benign human pituitary tumors.