Allelic loss of the active X chromosome during bladder carcinogenesis.

Abstract

Previous studies have shown that loss of the X chromosome is involved in the carcinogenesis of certain human malignancies. To determine whether X-linked allelic losses occur during bladder tumorigenesis and whether such losses involve the active or the inactive X chromosome. We analyzed the deletion status of the X-linked human androgen receptor gene locus in 6 female patients who underwent radical cystectomies for muscle-invasive urothelial carcinoma of the urinary bladder. Four patients had coexisting urothelial carcinoma in situ. Analysis for inactivation of the X chromosome was carried out in parallel. Three cases were informative. Invasive tumor samples showed loss of heterozygosity involving the active allele at the androgen receptor locus in all 3 positive cases, whereas carcinoma in situ showed nonrandom X chromosome inactivation but not allelic deletion. Our data suggest that allelic loss of the activated X chromosome is involved in bladder carcinogenesis and cancer progression.