Proliferating cell nuclear antigen expression in renal cell carcinoma. Prognostic implications

VEGF, COX-2, and PCNA expression in renal cell carcinoma subtypes and their prognostic value

OBJECTIVE

To evaluate the prognostic value of new markers such as VEGF (vascular endothelial growth factor), COX-2 (cyclooxygenase-2), and PCNA (proliferating cell nuclear antigen) and review their differences in expression by histological subtype in patients with renal cell carcinoma (RCC).

METHODS

About 99 patients who underwent radical (n = 79) or partial nephrectomy (n = 20) were included in this study. Histopathological specimens from the subjects were retrospectively analyzed immunohistochemically for the presence of VEGF, COX-2, or PCNA.

RESULTS

Mean staining ratios for VEGF, COX-2, and PCNA were 16.5, 16.8, and 31%, respectively. Correlations were evaluated among these three prognostic factors. There was no correlation between PCNA and VEGF (P = .068), but there were significant correlations between COX-2 and both PCNA and VEGF (P = .005 and P = .000, respectively). A significant correlation was found between the expression of VEGF and both pathologic stage and vascular invasion (P = .018 and P = .025, respectively). In addition, patients with conventional RCC had significantly lower VEGF and COX-2 levels than those with papillary RCC (P < .012).

CONCLUSIONS

It is obvious that prognostic factors such as VEGF, COX-2, and PCNA may vary depending on histological subtype. The level of expression of these factors together with histological subtype may provide valuable predictive information about the outcome of treatment.

Expression of cyclin D1, D3, E, and p27 in human renal cell carcinoma analysed by tissue microarray

Aberrations in the G1/S transition of the cell cycle have been observed in many malignancies and seem to be critical in the transformation process. Few studies have delineated the presence of G1/S regulatory defects and their clinical relevance in renal cell carcinoma (RCC). Therefore, we have examined the protein contents of cyclin D1, D3, E, and p27 in 218 RCCs, using tissue microarray and immunohistochemistry. The results from a subset of tumours were confirmed by Western blotting and immunohistochemical staining of regular tissue sections. Interestingly, low protein contents of cyclin D1 and p27 were associated with high nuclear grade, large tumour size, and poor prognosis for patients with conventional tumours. We further observed substantial differences in the pattern of G1/S regulatory defects between the different RCC subtypes. The majority of both conventional and papillary cases expressed p27; however, chromophobe tumours generally lacked p27 staining. In addition, conventional RCCs often expressed high cyclin D1 protein levels, while papillary RCCs exhibited high cyclin E. In summary, we have shown that G1/S regulatory defects are present in RCC and are associated with clinico-pathological parameters. The pattern of cell cycle regulatory defects also differed between RCC subtypes.

Apoptosis and expression of Bcl-2, Bcl-XL, and Bax in renal cell carcinomas

There are at present disparate published results with regard to the relevance of the Bcl-2 gene family, levels of apoptosis, and cell proliferation in the development and progression of renal cell carcinoma (RCC). The present study analyses the inter-relationship between the expression of representatives of the anti-apoptotic (Bcl-2, Bcl-XL) or pro-apoptotic (Bax) Bcl-2 proteins, incidence of apoptosis, and mitosis in a selected small group of 22 graded RCCs that had paired normal renal tissue, or non-neoplastic tissue in the renal biopsy specimen. The cases were chosen to determine the feasibility of measuring these parameters as potential surrogate markers of progression or treatment failure of the cancers. The results showed that in approximately 50% of the RCCs, where Bcl-2 and/or Bcl-XL expression was high, apoptosis was not detected, and when expression of these proteins was low or not found, increased levels of apoptosis were seen. In most of the remaining 50% of samples, high levels of Bcl-XL but not Bcl-2 were negatively correlated with low levels of apoptosis (Bcl-XL: r = -0.437, P = 0.07 and Bcl-2: r = +0.560, P = 0.02). For the same group of samples, high Bax expression was found in association with apoptosis (r = +0.578, P = 0.02). A novel finding was an association between low expression of Bcl-2 and/or Bcl-XL in normal tissue and the level of expression of these proteins in the RCCs, an intrinsic variation that may be an individual patient factor. The results indicate that, in RCCs with increased expression of Bcl-2 and/or Bcl-XL, levels of apoptosis are minimal and these combined factors may assist in progression of the cancers and resistance to treatments.

Cell proliferation in renal cell carcinoma--a comparative study of cell kinetic methods

Four different methods of assessing cell proliferation in renal cell carcinoma were compared in a total of 136 samples to analyze their degree of agreement and usefulness. The methods compared were flow cytometric S-phase (S-FCM) analysis, proliferating cell nuclear antigen expression detected by immunohistochemistry (PCNA-IHC), in vivo iododeoxyuridine incorporation analyzed with immunohistochemistry (IdUrd-IHC), and flow cytometry (IdUrd-FCM). The mean S-FCM fraction was 5.9%, compared with a mean PCNA-IHC labeling index of 4.7%. The mean labeling indices obtained by IdUrd-IHC and IdUrd-FCM were 1.2% and 1.7%, respectively. The four methods correlated well with each other. When the methods were compared according to Bland and Altman, good agreement was shown. A statistically significant difference in proliferation between diploid and aneuploid tumor samples was found with all methods (P < 0.001). The results showed that the four different methods provided comparable information on proliferative activity, although different cell cycle compartments were monitored.