Cell surface antigens in renal tumour cells: detection by immunoluminescence and enzymatic analysis

Two renal cell carcinoma cell lines (49RC 43STR and 75RC 2STR) were characterized by detection of the cell surface proteins: CD44(var), intercellular adhesion molecule-1 (ICAM-1), urokinase-type plasminogen activator (uPA) and its receptor and aminopeptidase N (APN). To detect their localization the immunoluminescent technique was used. In addition, the enzyme activity of uPA and APN was investigated in cell suspensions as well as in monolayers. The latter procedure was more advantageous since the additional use of HPLC permits a single registration of the fluorescent hydrolysis-product AMC (7-amino-4-methylcoumarin) without interference by cellular autofluorescence or non-reacted fluorescent substrate. Unlike 75RC 2STR, the cell line 49RC 43STR expressed high levels of uPA and APN. Contrary to that the cell line 75RC 2STR expressed high levels of ICAM-1 and CD44(v6), whereas 49RC 43STR showed a low level of ICAM-1 and no distinct light signal with anti-CD44(v6). The uPA activity was measured directly as well as indirectly (via plasmin) with the substrate Z-Gly-Gly-Arg-AMC. Both activator and plasmin activity were inhibited by D-Val-Phe-Lys-CMK and phenylmethylsulfonyl fluoride. The anti-catalytic antibody to uPA and that to uPA receptor were found to be inhibiting the uPA activity in a concentration-dependent manner. APN activity was assayed using alanine-p-nitroanilide. Peptidase activity was effectively inhibited by 1,10-phenanthroline and partly inhibited by ethylenediamine-tetraacetic acid.

Endopeptidase 24.11/CD10 is down-regulated in renal cell cancer

The regulatory mechanisms responsible for malignant transformation, tumor progression and metastasis in renal cell cancer (RCC) are still unclear, but there is some evidence that biologically active peptides might have regulatory effects on the behavior of this malignancy. Tumor cells can change local concentrations of active peptides by modulating their cell-surface enzymes. Using immunohistochemistry and enzyme-histochemistry, the expression of various membrane peptidases was examined in RCC and adjacent noninvaded renal parenchyma (n = 44). We describe the down-regulation of neutral endopeptidase 24.11 (NEP) protein expression in RCC of the clear cell/chromophilic type when compared with renal parenchyma, and show for the first time the lack of enzyme activity of NEP in RCC. The strongest expression could be found for dipeptidyl peptidase IV (DPIV) which is only decreased in RCC of the chromophobe cell type and is even present in oncocytoma. Aminopeptidase N (APN) and aminopeptidase A (APA) show attenuated expression in up to one third of clear cell/ chromophilic RCC. Chromophobe RCC and oncocytomas do not express APN, APA, NEP and gamma-glutamyltranspeptidase.

Regulation of the expression of aminopeptidase A, aminopeptidase N/CD13 and dipeptidylpeptidase IV/CD26 in renal carcinoma cells and renal tubular epithelial cells by cytokines and cAMP-increasing mediators

Aminopeptidase (AP) A is a transmembrane type II molecule widely distributed in mammalian tissues. Since APA expression may be absent in renal cell carcinoma (RCC), it is possible that there is an altered regulation or other defect of APA upon malignant transformation of proximal tubular cells. However, investigations into the regulation of APA on tumour cells are rare. We report, for the first time, that both transforming growth factor-beta 1 (TGF-beta1) and tumour necrosis factor-alpha (TNF-alpha) down-regulate APA mRNA as well as protein expression in renal tubular epithelial cells and RCC cells in culture. In addition to this, both cytokines decrease dipeptidylpeptidase (DP) IV/CD26 mRNA, but not APN/CD13 mRNA expression. Otherwise, IL-4 and IL-13 increase CD13 as well as CD26 expression, but do not alter APA expression. Interferon-alpha (IFN-alpha), IFN-beta and IFN-gamma increase mRNA expression of all the three membrane ectopeptidases, whereas IL-1, IL-6, IL-7, IL-12 and granulocyte-macrophage colony-stimulating factor (GM-CSF) have been found to be without any significant effect. Treatment of cultured cells with cAMP-increasing agents, such as 8-bromo-cAMP or A23187, results in an increase in APA and DPIV/CD26, but no change in APN/CD13 mRNA expression or even a decrease in it. Furthermore, AP inhibitors can influence APA mRNA expression, since bestatin causes an increase in APA expression in a time- and dose-dependent manner, whereas bestatin does not change CD13 or CD26 expression. No difference could be found with respect to the modulation by different mediators between RCC cells and renal epithelial cells, though permanent tumour cell lines such as Caki-1 and Caki-2 may have lost some of the normally expressed peptidases.

Concentrations of lysosomal cysteine proteases are decreased in renal cell carcinoma compared with normal kidney

Renal cell carcinoma contains significantly lower concentrations of the lysosomal cysteine proteases, cathepsins B, C, H, L and S, than does normal kidney, as shown by several methods, such as activity determination, enzyme-linked immunosorbent assay, immunoblotting and immunohistochemistry. The same low levels of enzyme activity and concentration have been determined in renal cell carcinoma metastases in the lung. Our results on the decreased concentration of cysteine peptidases at the protein level would seem to conflict with earlier results on an increased concentration of the cathepsin L mRNA in renal cell carcinoma.

Prognostic value of the immunomonitoring of patients with renal cell carcinoma under therapy with IL-2/IFN-alpha-2 in combination with 5-FU

After tumor nephrectomy, patients suffering from metastatic renal cell carcinoma (RCC) received interleukin-2 (IL-2), interferon (IFN)-alpha-2b and 5-fluorouracil (5-FU) in one to three treatment cycles over 8 weeks. Using flow cytometry, we investigated the immunophenotype of peripheral blood lymphocytes from 22 patients during therapy. In all patients, we found an increase in the absolute number of T lymphocytes, especially of the CD4 type, and in the number of HLA-DR+, CD25+ T cells and natural killer (NK) cells. The mean number of B cells did not increase during therapy. The numbers of CD4+, CD8+ and CD25+ T cells correlated significantly with the clinical response. In addition, we found that the pretherapeutic number of T lymphocytes and B cells but not of NK cells was significantly higher in patients with a therapy-induced clinical response. In conclusion, we describe the predictive value of the number of lymphocytes from peripheral blood for the efficiency of IL-2/IFN-alpha-2b therapy in combination with 5-FU in patients with metastatic renal cell carcinoma.

Expression of aminopeptidase N/CD13 in tumour-infiltrating lymphocytes from human renal cell carcinoma

We have previously demonstrated the expression of aminopeptidase N (APN, CD13) on synovial T cells from patients with different forms of arthritis. T cells of peripheral blood and serous body fluids are CD13-negative but can be stimulated to express CD13 after activation, e.g., with Con A. In the present report, double-labelling and flow cytometry analyses were performed to characterize the phenotype of tumour-infiltrating lymphocytes (TIL). A large panel of antibodies specific for different activation-associated molecules on T cells was used. In contrast to TIL of lung cancer, TIL of renal cell carcinoma (RCC) consisted of significantly higher percentages of T cells expressing CD13, dipeptidylpeptidase N (DPIV, CD26) and HLA-DR, whereas T cells of lung cancer expressed more CD25, CD69 and CD54/ICAM1. No differences could be found in the expression of CD45RO, CD49a/VLA-1 and CD62L/L-selectin. Our results demonstrate that T cells in RCC and lung cancer differ in their phenotype, especially with respect to surface aminopeptidases. Investigations into the function of APN on T cells could be of help in gaining deeper insight into tumour defence as well as into general mechanisms of T cell functions.