LOSS OF THE CDKN2A/p16 LOCUS DETECTED IN BLADDER IRRIGATION SPECIMENS BY FLUORESCENCE IN SITU HYBRIDIZATION

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Abstract
Purpose: We measured the CDKN2A/p16 tumor suppressor gene locus in bladder irrigation specimens and correlated the measurement with the clinical status of patients with bladder cancer. Materials and Methods: Irrigation specimens were obtained at cystoscopy from 10 normal controls, 21 patients with bladder cancer in whom no concurrent bladder tumor was seen and 23 patients with bladder tumors. Deoxyribonucleic cytometry and fluorescence in situ hybridization measurements were made. One fluorescence in situ hybridization probe was specific to the chromosome 9 centromere and the other, COSp16, targeted the CDKN2A/p16 region on chromosome 9p21. Three rates were calculated, including the hyperdiploid fraction from deoxyribonucleic acid cytometry, disomic fraction from the 9 centromere count and COSp16F, the frequency of COSp16 in association with 9 centromere. Specimens were classified as positive or negative for each of these rates using cutoff points based on previous studies and the distribution of values obtained for the normal control specimens. Results: Hyperdiploid fraction values were positive (greater than 8%) in 1 normal and 1 nontumor specimen. Ten specimens from patients with tumor showed elevated hyperdiploid fraction values. In 4 nontumor and 13 tumor irrigation specimens the chromosome 9 disomic fraction values were positive (less than 80%). COSp16F was positive (less than 83%) for 18 nontumor irrigation specimens and 18 tumor irrigation specimens. One normal, and 39 of 44 nontumor and tumor irrigation specimens were positive by at least 1 test. Conclusions: COSp16 loss is measurable in irrigation specimens and it correlates with clinical status. This assay may prove useful in screening for and managing bladder cancer.