DETECTION OF LOSS OF HETEROZYGOSITY IN THE P53 TUMOR-SUPPRESSOR GENE WITH PCR IN THE URINE OF PATIENTS WITH BLADDER CANCER

Somatic TP53 mutations are relatively rare among adrenocortical cancers with the frequent 17p13 loss of heterozygosity

PURPOSE

Allelic losses [loss of heterozygosity (LOH)] at the 17p13 locus are frequent (85%) in adrenocortical cancers. The tumor suppressor gene TP53 is located at 17p13. The aim of the study was to determine the frequency of TP53 somatic inactivating mutations in adrenocortical tumors with 17p13 LOH and their clinico-biological correlations.

EXPERIMENTAL DESIGN

TP53 somatic mutations, intragenic LOH (VNTR1 marker), and p53 overexpression were studied in 36 adrenocortical tumors with 17p13 LOH determined by Southern blot.

RESULTS

TP53 mutations were detected in 33% of the tumors, and VNTR1 LOH was present in 44% of the cases and did not always correlate with the presence of a TP53 mutation. Only the TP53-mutant tumors exhibit a strong nuclear immunoreactivity. TP53-mutant tumors were significantly larger than wild-type TP53 tumors (median tumor weight: 640 versus 185 g; P=0.02), were associated with a more advanced stage of tumor progression (MacFarlane stage IV; P=0.01), and had a shorter disease-free survival (P=0.03).

CONCLUSIONS

The finding that only a minority of adrenocortical tumors with 17p13 LOH had either a VNTR1 LOH or a TP53 mutation indicates that TP53 might not be the only or major tumor suppressor gene at 17p13 involved in adrenocortical cancer progression. We suggest that a genetic instability of the 17p13 region, occurring early in adrenocortical cancer development, involves various genes located in this region. TP53 might be only one of them, and its alteration by the occurrence of inactivating mutation is associated with the development of more aggressive tumors.

The significance of p53 and bcl-2 overexpression and other prognostic factors in transitional cell carcinoma of the bladder

The aim of this study was to investigate the expression of bcl-2 and p53 oncoproteins in a series of transitional cell bladder carcinomas and its relation to traditional prognostic indicators and patients' survival. Specimens from 59 patients who underwent transurethral resection from March 1992 to February 1997 were included in this study. Tumors were graded based on WHO grades 1-3 and staged according to the 1997 TNM classification. Three patients lost to follow-up were excluded from the analysis. We could not establish a statistically significant relation between bcl-2 and p53 and other parameters such as sex, age, stage and grade. Tumor grade and stage were the most important factors for predicting tumor recurrence and aggressiveness. Only sex seems to significantly affect the statistics of the risk of death (p<0.05). Women had quadruple risk of death compared to men.

Detection of methylated apoptosis-associated genes in urine sediments of bladder cancer patients

PURPOSE

There is increasing evidence for a fundamental role for epigenetic silencing of apoptotic pathways in cancer. Changes in DNA methylation can be detected with a high degree of sensitivity, so we used the MethyLight assay to determine how methylation patterns of apoptosis-associated genes change during bladder carcinogenesis and whether DNA methylation could be detected in urine sediments.

EXPERIMENTAL DESIGN

We analyzed the methylation status of the 5' regions of 12 apoptosis-associated genes (ARF, FADD, TNFRSF21, BAX, LITAF, DAPK, TMS-1, BCL2, RASSF1A, TERT, TNFRSF25, and EDNRB) in 18 bladder cancer cell lines, 127 bladder cancer samples, and 37 samples of adjacent normal bladder mucosa using the quantitative MethyLight assay. We also analyzed the methylation status in urine sediments of 20 cancer-free volunteers and 37 bladder cancer patients.

RESULTS

The 5' regions of DAPK, BCL2, TERT, RASSFIA, and TNFRSF25 showed significant increases in methylation levels when compared with nonmalignant adjacent tissue (P < or = 0.01). Methylation levels of BCL2 were significantly associated with tumor staging and grading (P < or = 0.01), whereas methylation levels of RASSF1A and ARF were only associated with tumor stage (P < or = 0.04), and TERT methylation and EDNRB methylation were predictors of tumor grade (P < or = 0.02). To investigate clinical usefulness for noninvasive bladder cancer detection, we further analyzed the methylation status of the markers in urine samples of patients with bladder cancer. Methylation of DAPK, BCL2, and TERT in urine sediment DNA from bladder cancer patients was detected in the majority of samples (78%), whereas they were unmethylated in the urine sediment DNA from age-matched cancer-free individuals.

CONCLUSIONS

Our results indicate that methylation of the 5' region of apoptosis-associated genes is a common finding in patients with bladder carcinoma. The ability to detect methylation not only in bladder tissue, but also in urine sediments, suggests that methylation markers are promising tools for noninvasive detection of bladder cancers. Our results also indicate that some methylation markers, such as those in regions of RASSF1A and TNFRSF25, might be of limited use for detection because they are also methylated in normal bladder tissues.

Advances in the clinical laboratory assessment of urinary sediment

Urinalysis has been used extensively in clinical practice to aid in the diagnosis of various renal and urologic diseases. The innovation of urinalysis is marching on right along with the rapid developments in biotechnology and astride from the solo urine cytology to sophisticated studies of individual component in the urinary sediment. In this review article, we focus on the use of flow cytometry and other technical advances in the examination of urinary sediment, the detection of urologic malignancies by the presence of microsatellite alteration in the urinary sediment, as well as the quantification of cytokine messenger RNA (mRNA) expression in urinary sediment by reverse transcription and real-time quantitative polymerase chain reaction (RT-QPCR). Notably, the study of cytokine mRNA expression in urinary sediment by RT-QPCR has recently been reported to provide important diagnostic information in kidney allograft recipients and patients with lupus nephritis. This simple and non-invasive method requires further study to determine its role in risk stratification and monitoring of therapeutic response in patients with other kidney diseases.

[Molecular diagnostics in urologic oncology. Detection of nucleic acids in urine samples]

The goal of molecular diagnostics in oncology is the early diagnosis of malignant disease processes during initial work-up or as part of follow-up. Body fluids serve as the primary material for non-invasive diagnostic methods. Besides actual tumor cells, the examination of urine can yield evidence of secreted proteins or even free nucleic acids. In principle, all of the methods available for the detection of tumor markers in tissue or blood samples can be successfully applied to the examination of urine samples. However, molecular biological examination of urine samples is associated with important problems because the cells in such samples are exposed to significant degradation and regression effects and because certain components of the urine act to inhibit the polymerase chain reaction. The present overview discusses the respective strengths and weakness of the available technology as applied to the diagnosis of urologic malignancies. Experimental studies conducted to date have reported high sensitivities and specificities for molecular diagnostics using urine samples. It is important to note that not only carcinomas of the urinary bladder can be diagnosed from material obtained in urine samples: in fact, the method can be used to diagnose entities such as renal cell and prostate carcinomas and, due to renal filtration of DNA, even non-urologic malignancies. The diagnostic application of these methods, however, remains in an experimental stage and must still clear several hurdles before becoming available for routine clinical use.

N-(4-hydroxyphenyl)retinamide (4-HPR) modulates GADD45 expression in radiosensitive bladder cancer cell lines

We previously demonstrated that N-(4-hydroxyphenyl)retinamide (4-HPR) and gamma-irradiation, when used in combination, had a synergistic effect in inducing apoptosis in bladder cancer cells, suggesting that 4-HPR may increase radiosensitivity in bladder cancer cells. To unravel molecular correlates in this radiosensitizing effect of 4-HPR, we examined the baseline and 4-HPR-induced expression of GADD45 to elucidate possible mechanisms by which 4-HPR enhanced the effect of gamma-irradiation in three bladder cancer cell lines. To investigate the role of p53 in mediating the radiosensitizing effect of 4-HPR, we also examined mutations in exons 5-9 by using direct sequencing and the levels of p53 expression by using RT-PCR and Western blot, before and after treatment with 4-HPR in these bladder cancer cell lines. Two cell lines had low expression of GADD45, and a dose-dependent increase in GADD45 expression induced by 4-HPR was found in bladder cancer cell lines without p53 mutations in exons 5-9. A combination of gamma-irradiation and 4-HPR showed a significantly greater effect in enhancing GADD45 expression than either agent used alone. The results indicate that the combined treatment with 4-HPR and gamma-irradiation has a stronger effect on GADD45 expression than the treatment with either agent alone, which suggests that the two agents may have an additive/synergistic effect. However, a normal p53 function appears to be necessary for the dose-dependent induction of GADD45 by 4-HPR. Once our results are verified and replicated by other investigators, 4-HPR may have a potential clinical implication in effectively treating bladder cancer in combination with low-gamma-irradiation therapy.

DNA alterations in body fluids as molecular tumor markers for urological malignancies

OBJECTIVES

DNA-based tumor markers are characterized by unique specificity rendering them an attractive target for molecular diagnosis of cancer in body fluids like blood serum/plasma and urine. Both cell-free tumor DNA circulating in plasma/serum and cellular tumor DNA are detectable by minimally invasive measures.

METHODS

Three main detection methods, microsatellite analysis, mutation analysis in genomic or mitochondrial DNA and gene promoter hypermethylation analysis are applied. Detection of gene promoter hypermethylation by methylation-specific PCR enables the best methodical sensitivity requiring a ratio of tumor DNA within normal DNA of less than 1:1000.

RESULTS/CONCLUSIONS

Tumor DNA derived from renal cell carcinoma, bladder cancer or prostate cancer is detectable in considerably more than 50% of plasma/serum samples and more than 70% of urine samples from these patients. Because the targeted DNA alterations are absent or very rare in controls, the specificity of DNA-based tumor detection methods reaches almost 100%. Although the methodology currently is experimental, automatization will make it easier and less expensive. This review is focused on the potential clinical value of DNA-based analysis of body fluids for the initial diagnosis and the follow-up of urologic cancer patients.