Cytogenetic Analysis of False-Positive Mucosa by Photodynamic Diagnosis Using 5-Aminolevulinic Acid - Possible Existence of Premalignant Genomic Alterations Examined by in vitro Experiment

Objective: Although photodynamic diagnosis is a powerful tool for the detection of flat urothelial tumors, false-positive fluorescent mucosa still requires further elucidation. Thus, we aimed to study the significance of nonmalignant fluorescent mucosa by a cytogenetic approach. Methods: Sixty specimens of bladder mucosa were collected from 20 patients who were suspected of having carcinoma in situ by fluorescence cystoscopy with 5-aminolevulinic acid. To detect the copy number aberrations, the multi-color fluorescence in situ hybridization technique was performed, and the variant fractions ( total fractions other than those of the modal copy number) of chromosomes 7, 9 and 17 and the chromosomal instability were determined. To delineate the relevant gene to the fluorescent mucosa, a comparative genomic hybridization technique was applied for 8 established bladder cancer cell lines, and these results were compared with the in vitro fluorescent expression experiment. Results: Fluorescent mucosa was detected in 33 of the 34 malignant tissue specimens ( 16 carcinoma in situ, 18 other transitional cell carcinomas) and in 11 of the 26 nonmalignant tissue specimens ( 6 dysplasia, 20 normal mucosa), with a false-positive rate of 42.3%. The variant fraction of chromosome 9 was significantly higher in fluorescent than in non-fluorescent mucosa, not only for all tissues ( 33 vs. 17%; p = 0.0069), but also for nonmalignant tissues ( 28 vs. 15%; p = 0.0225). There was no alteration in chromosome 9 in 1 cell line without fluorescent mucosa, while 5 of the 7 cell lines with fluorescent mucosa had a common deleted region on 9q24.1. Conclusion: These data suggest that a substantial portion of nonmalignant fluorescent mucosa harbors alterations in chromosome 9. Copyright (C) 2009 S. Karger AG, Basel