DNA slit-scan flow cytometry of bladder irrigation specimens and the importance of recognizing urothelial cells

Analytical capabilities of the ImageStream cytometer

Imaging cytometry has recently become an important achievement in development of flow cytometric technologies. The ImageStream cytometer combines the vast features of classical flow cytometry including an impartial analysis of great number of cells in short period of time which results in strong statistical data output, with essential features of fluorescence microscopy such us collecting of real multiparameter images of analyzed objects. In this chapter, we would like to introduce an overview of imaging cytometry platform and emphasize the potential advantages of using this system for several experimental purposes. Moreover, both well established as well as potential applications of imaging cytometry will be described. Eventually, we would like to illustrate the unique use of ImageStream cytometer for identification and characterization of subpopulations of stem/ progenitor cells present in different biological specimens.

Assessment of DNA flow cytometry as a surrogate end point biomarker in a bladder cancer chemoprevention trial

Although conventional cytology represents the most widely performed cytometric analysis of bladder cancer cells, DNA flow cytometry has, over the past decade, been increasingly used to evaluate cell proliferation and DNA ploidy in cells from bladder washings. We have investigated whether DNA flow cytometry and conventional cytology of epithelial cells obtained from bladder washings provide reliable surrogate endpoint biomarkers in clinical chemoprevention trials. We used cytometric and clinical data from a chemoprevention trial of the synthetic retinoid Fenretinide on 99 patients with superficial bladder cancer. A total of 642 bladder washing specimens obtained from the patients at 4 month intervals was analyzed. Intra-individual agreement and correlation of flow cytometric DNA ploidy (diploid vs. aneuploid), DNA Index, Hyper-Diploid-Fraction (proportion of cells with DNA content higher than 2C), and conventional cytologic examination, as assessed by kappa statistics and Spearman's correlation test, were poor from baseline through 24 months. Moreover, no correlation was found between DNA ploidy and cytology at each time point. The same results were obtained when the analyses were stratified by treatment group. In addition, the association between the results of bladder washing (by either DNA flow cytometry or cytology) and concomitant tumor recurrence was significant only for abnormal cytology, while neither biomarker was predictive of tumor recurrence at the subsequent visit. During the time of this study only four patients progressed to muscle-invasive bladder cancer, indicating the "low-risk" features of the patient population. We conclude that DNA flow cytometry and conventional cytology on epithelial cells obtained from bladder washings do not appear to provide suitable surrogate endpoint biomarkers during the early stages of bladder carcinogenesis.

DNA cytometry and chromosome 9 aberrations by fluorescence in situ hybridization of irrigation specimens from bladder cancer patients

OBJECTIVES

To determine the sensitivity and specificity of combining fluorescence in situ hybridization (FISH) measurement of chromosome 9 and DNA cytometry of bladder irrigation specimens in the detection of bladder cancer.

METHODS

Bladder irrigation specimens were obtained from 37 normal control patients and 317 bladder cancer patients during cystoscopic examinations. Bladder cancer patients were sampled in the absence of observable tumor (256 specimens) and concurrently with tumor (204 specimens). Chromosome 9 copy number was determined on a cellular basis by FISH, and cellular DNA content was determined by Feulgen DNA staining and image cytometry.

RESULTS

Sensitivity of chromosome 9 FISH was 42% for all tumors and was not correlated to transitional cell carcinoma tumor grade, while the sensitivity of DNA cytometry was 55% and improved with increasing grade from 38% for grade 1 to 90% for grade 3 tumors. The results of FISH and DNA cytometry were combined, resulting in specificity of 92% and sensitivity of 69% for grade 1, 76% for grade 2, and 97% for grade 3 tumors.

CONCLUSIONS

The lack of increase with grade in the percentage of positive specimens by FISH supports the hypothesis that chromosome 9 aberrations are critical events in bladder tumorigenesis for many patients. These data demonstrate the presence of cells in irrigation specimens with specific genomic lesions of chromosome 9 and DNA content. Combining FISH on chromosome 9 and DNA cytometry provides an increase in sensitivity to transitional cell carcinoma over either test alone.

Loss of the CDKN2A/p16 locus detected in bladder irrigation specimens by fluorescence in situ hybridization

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.

Abnormal flow cytometry profiles in patients with interstitial cystitis

Flow cytometry was performed on bladder cells from patients with interstitial cystitis and control patients. Cells were processed in standard fashion for flow cytometry with propidium iodide staining and analysis was restricted to samples with sufficient cells for cytokeratin gating and acceptable coefficients of variation. Of 14 interstitial cystitis patients 4 (29%) demonstrated aneuploid deoxyribonucleic acid (DNA) profiles as evidenced by a discrete peak with a DNA index of 1.2 or greater in the cytokeratin positive population. The aneuploid peak accounted for up to 54% of the cytokeratin positive population in these samples. No such aneuploid DNA profiles were evident in specimens obtained from control patients. A significant DNA tetraploid population, as evidenced by a 4C (G2) peak greater than 20%, was observed in 6 of 14 interstitial cystitis patients (43%) and 8 of 11 controls (72%). Manual counting of the per cent of binucleated cytokeratin positive cells in the cytokeratin stained population and nuclear preparations of several samples for flow analysis indicate that apparent DNA tetraploidy in the interstitial cystitis and control patients is due to an abundance of binucleated cells. Aneuploid DNA profiles on barbotage specimens from interstitial cystitis patients may reflect a real karyotypic abnormality or altered chromosome complement (true aneuploidy), abnormal chromatin structure or abnormal cytoplasmic binding of the propidium iodide stain. This finding may signal an underlying abnormality of the epithelial cell population in some patients with the clinical diagnosis of interstitial cystitis.

Bladder irrigation specimens assayed by fluorescence in situ hybridization to interphase nuclei

Bladder irrigation specimens provide a sampling of the entire bladder urothelium and are the most practical sample for longitudinally monitoring patients. This study presents cross-sectional fluorescence in situ hybridization (FISH) analyses with correlated DNA cytometry data on 76 patients monitored for recurrent bladder tumors. FISH probes complementary to centromeric satellite sequences for chromosomes 1, 7, 9, 11, 15, and 17 were used. Aberrations in copy number were observed for chromosomes 1, 7, 11, and 17 principally in patients with aneuploid tumors. Monosomy of chromosome 9 was observed in 39% of the diploid and 31% of the specimens with high hyperdiploid fraction. Significantly, 24% of patients with a history of bladder cancer but with no clinical evidence of disease exhibited monosomy of chromosome 9. This suggests a persistent and significantly large population of abnormal cells in the absence of clinical evidence of disease. Loss of chromosome 9 relative to DNA ploidy was observed in 24% of patients with no evidence of disease, in 59% of patients with tumor, and in 79% of patients with histologically confirmed transitional cell carcinoma, grades 1-3. Loss of chromosome 15 was also observed in a large percentage of patients. Loss of chromosome 15 was observed in 41% of specimens from patients in whom no tumor was seen, in 38% of specimens from patients with tumor, and in 67% of specimens from patients with histologically confirmed transitional cell carcinoma. Results of this study document the use of bladder irrigation specimens as a specimen source for FISH analyses.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow and image cytometry for DNA analysis in bladder washings: improved concordance by using internal reference for flow

Using flow or image cytometry, we compared the DNA distribution of cells from bladder washings from 52 patients with bladder cancer. For image cytometry, urothelial nuclei (recognized visually) were analyzed for DNA content using polymorphonuclear nuclei as internal diploid reference. For flow cytometry, two methods can be used: either all cells can be analyzed, as commonly performed, or urothelial cells can be analyzed alone, after specific detection. In this flow cytometry study, cells were doubly stained for panurothelial antigens T16 and for DNA. All the cells were first analyzed using peripheral lymphocytes as an external reference; 79% of the results were similar with results obtained from image analysis. For discordant results, flow-cytometric data were reprocessed to identify immunologically stained urothelial cells; one additional case became concordant with image cytometry when only urothelial cells were analyzed, with lymphocytes as diploid reference; a better concordance (94%) was found when the nonurothelial cells of the samples served as a diploid reference instead of peripheral lymphocytes. This suggests that we achieved an improvement of the flow-cytometric evaluations for ploidy assessment, and we conclude that, on these conditions, flow or image analysis can be considered as equivalent methods for DNA content studies of tumors.

Failure of anticytokeratin 18 antibody to improve flow cytometric detection of bladder cancer

BACKGROUND

Bladder washing specimens containing inflammatory or squamous cells have been difficult to accurately analyze with single-parameter DNA flow cytometric (FCM) methods.

METHODS

The anticytokeratin 18 antibody, CK5, was used in a multiparameter assay of 275 bladder washing and voided urine specimens to immunoselect only the bladder transitional cells for DNA analysis.

RESULTS

Flow cytometric detection of transitional cell carcinoma was increased by immunoselection of CK5-positive cells in specimens from patients with disease. Unfortunately, a similar increase in hyperdiploid cells in pathologically benign specimens was observed, which resulted in a false-positive rate of 45%. In some instances, multiparameter FCM assays with CK5 could detect aneuploid cell populations not clearly evident by single-parameter analysis.

CONCLUSIONS

However, the results from this study of the hyperdiploid cell fraction showed that the increased sensitivity resulting from the use of CK5 was not clinically useful because of the decrease in specificity.