DNA fingerprinting of renal cell carcinoma with special reference to tumor heterogeneity

Nuclear DNA content-derived parameters correlated with heterogeneous expression of p53 and bcl-2 proteins in clear cell renal carcinomas

BACKGROUND

p53 and bcl-2 are two key genes involved in cell cycle and cell death regulation. Altered expression or mutation of these genes has been found in human cancers and also has been identified in clear cell renal carcinoma (RCC). Their role in RCC progression, however, is still unclear. By contrast, the prognostic significance of ploidy and S-phase fraction (SPF) have been studied extensively in RCC. To better characterize the biologic role of p53 and bcl-2 oncoproteins in RCC, we offer a multisample correlative analysis of the expression of these two proteins with ploidy and SPF.

METHODS

Ploidy and SPF along with p53 and bcl-2 expression were analyzed in 296 specimens, selected by multiple sampling of 33 consecutive operable RCCs. The expression of p53 and bcl-2 proteins was studied by immunohistochemistry, and SPF and tumor ploidy were studied by flow cytometry.

RESULTS

In our study, 4 of 32 (12.5%) were found to be diploid, and 28 of 32 (87.5%) cases showed an abnormal DNA content. Among the aneuploid tumors, 14 of 28 (50%) were multiploid. Heterogeneous DNA content was detected in 21 of 32 (65.6%) tumors and was correlated with the more advanced Robson stage tumor (P = 0. 03). Intratumor heterogeneity also was detected for p53 and bcl-2 protein expression. Expression of p53 protein correlated with the lack of bcl-2 protein expression (P = 0.0032), aneuploidy (P < 0. 0001), and high SPF (P = 0.0006), whereas bcl-2 expression was associated with a normal DNA content (P < 0.0001) and low SPF (P = 0. 035).

CONCLUSIONS

Within each RCC, p53 and bcl-2 expression is markedly heterogeneous. Our results depicted a scenario in which bcl-2 protein, expressed by normal renal parenchyma, is still present in euploid cell clones of RCC but disappears during the progression of renal neoplasm toward a more aggressive phenotype characterized by overexpression of p53 protein, aneuploidy, and high SPF.

Heterogeneity in renal cell carcinoma and its impact no prognosis--a flow cytometric study

In the process of tumour progression genetic instability is the basis for the evolution of tumour cell clones with various genotypic and phenotypic characteristics causing heterogeneity. Renal cell carcinoma has a long prediagnostic growth period, which increases the probability of clonal evolution. We have studied 200 consecutive renal cell carcinomas, addressing the interrelationship between intratumour heterogeneity and clinicopathological factors. DNA ploidy patterns were analysed in multiple samples from each tumour using flow cytometry and compared with clinical stage, tumour invasion, metastatic rate and survival. Eighty-five of 192 evaluable tumours (44%) were homogeneous concerning DNA ploidy (62% diploid, 38% aneuploid). Among 107 heterogeneous tumours a majority (79%) contained aneuploid as well as diploid cell clones. Homogeneously diploid tumours had a lower incidence of local tumour spread compared with tumours with aneuploid cell clones (P < or = 0.001), but the frequency of distant metastasis at time of diagnosis was similar. The presence of aneuploidy in at least one sample from a tumour was a significant adverse prognostic factor (P < 0.001), whereas the degree of heterogeneity had no influence on survival. The frequent heterogeneity demonstrated indicates that multiple samples must be investigated to evaluate properly the malignant character of renal cell carcinoma.

DNA fingerprint analysis in acute leukemias

Restriction fragment length polymorphism (RFLP) analysis by Southern blotting or direct in-gel hybridization is a routine procedure in any genetic laboratory. Minisatellites and simple repeat probes for RFLP analysis have proved to be highly informative genetic markers, depending on their degree of homology and index of heterozygosity. Several of these probes have considerable individualization potential, thus yielding 'fingerprint' pattern. In the setting of acute leukemia DNA fingerprint (DNA-F) analysis is able to provide considerable information concerning the genetic instability of the leukemic clone. DNA-F is capable of detecting randomly occurring genetic alterations of unknown localization and to identify new hotspots of malignant transformation. As DNA-F analysis is not likely to be hampered by the effects of chemotherapy or DNA methylation, altered fingerprints may be regarded as characteristic of the leukemic clone. With the introduction of polymerase chain reaction (PCR) and increasing sensitivity, DNA-F analysis is likely to be of significant importance in monitoring minimal residual disease in human leukemia.

DNA analysis in forensics, disease and animal/plant identification

During 1993, significant advances have been achieved in applications of DNA analysis to forensic science, disease assessment, and animal/plant identification. These advances include the development of simple and high sample-throughput techniques for highly informative personal identification, rapid screening for pathogens and the development of polymorphic genetic markers in plants and animals.