Expression of CD44 isoforms in human renal cell carcinomas

CD44 is associated with tumor recurrence and is an independent poor prognostic factor for patients with localized clear cell renal cell carcinoma after nephrectomy

CD44 has been implicated in tumor development and progression in several types of cancer. CD44 expression is altered in renal cell carcinoma (RCC) and has been suggested as a useful prognostic marker, but its prognostic role in RCC remains controversial. We investigated the expression of CD44 in a large homogeneous set of localized clear cell RCC to determine its potential prognostic value. We examined 110 patients with localized clear cell RCC who underwent nephrectomy. The clinicopathological data were obtained retrospectively and the expression level of CD44 was studied by immunohistochemistry. Correlations between CD44 expression and clinical parameters as well as survival were determined. The CD44-high expression group (HEG) was significantly associated with a higher nuclear grade (P=0.014) and tumor recurrence (P<0.001) when compared with the CD44-low expression group (LEG). Concerning survival, the 5-year recurrence-free survival (RFS) rates for the CD44-HEG and CD44-LEG groups were 38.9 and 91.3%, respectively (P<0.001), and the 5-year disease-specific survival (DSS) rates for the CD44-HEG and CD44-LEG groups were 55.6 and 94.6%, respectively (P<0.001). Multivariate analyses showed that CD44 expression [hazard ratio (HR), 9.204; P<0.001] was an independent risk factor predicting RFS in patients with clear cell RCC. CD44 expression remained an independent prognostic factor for DSS (P=0.002). In conclusion, these data indicate that CD44 expression is associated with the progression of clear cell RCC and is an independent poor prognostic factor for tumor recurrence and survival, suggesting that CD44 may serve as a useful molecular marker.

The prognostic value of adhesion molecule CD44v6 in women with primary breast carcinoma: a clinicopathologic study

AIMS

CD44 functions as an adhesion molecule. Within the family of CD44 isoforms, the spliced variant 6 has been causally associated with the development of metastases and poor prognosis in animal models and several human cancers. The aim of this study was to investigate the prognostic value of CD44v6 in women with primary breast carcinoma.

MATERIALS AND METHODS

The women with primary breast carcinoma in this study were followed up clinically for a period of 5 years. Clinicopathologic features, including tumour size, axillary nodal status, histological grade and pTNM stage, were determined for a cohort of 78 women presenting with primary breast carcinoma. Standard immunohistochemistry was used to explore CD44v6 expression. The data obtained were analysed by univariate and multivariate analyses.

RESULTS

Forty-three out of 78 (55%) women with breast carcinoma were CD44v6-positive (i.e. over 5% of tumour cells exhibited positive staining). Significant sequential increase of CD44v6 expression was observed in women with metastases of axillary nodes, tumour size more than 2 cm, advanced pTNM stage and survival period less than 5 years. Univariate analysis showed that axillary nodal status, primary tumour size, histological grade, and pTNM stage were associated with 5-year survival, and CD44v6 expression was associated with primary tumour size, axillary nodal status, pTNM stage and 5-year survival. In multivariate analysis, using the Cox-regression model, CD44v6 expression was not an independent prognostic factor.

CONCLUSIONS

CD44v6 expression was correlated with tumour size, metastases of axillary nodes, pTNM stage, and 5-year survival; however, multivariate analysis revealed that CD44v6 expression failed to be an independent predictor of patient prognosis.

Expression of osteopontin and CD44 molecule in papillary renal cell tumors

The aim of the study was to analyze the expression of CD44 adhesion molecule and its ligand osteopontin in papillary renal cell tumors, and to assess the possible prognostic significance of CD44 and osteopontin expression in papillary renal cell carcinomas. The expression of the standard and v6 exon containing isoforms of CD44 molecule, as well as of its ligand osteopontin, was immunohistochemically evaluated in 43 papillary renal cell tumors, which included 5 adenomas and 38 carcinomas. In order to assess their prognostic significance, the results obtained in papillary renal cell carcinomas were compared to usual clinicopathological parameters such as tumor size, histological grade, pathological stage, and Ki-67 proliferation index. Normal renal tissue was negative for CD44s and v6 isoforms, while the expression of osteopontin was found in distal tubular epithelial cells in the form of cytoplasmic granular positivity. CD44s and v6 isoforms were upregulated in 22 (58%) and 12 (32%) out of 38 carcinomas, respectively. Among all clinicopathological parameters examined, we only found significant association of CD44s-positive carcinomas with lower pathological stage (p=0.026). Papillary renal cell adenomas were generally negative for CD44s, except for focal positivity found in one sample. The osteopontin protein was detected in all adenomas and all papillary renal cell carcinomas, except one. Our results show constitutive expression of osteopontin in papillary renal tumors, including papillary renal cell adenomas. The upregulation of CD44s and v6 isoforms, although found in a considerable number of papillary renal cell carcinomas, does not appear to have any prognostic value in this type of renal cancer.

Tumor antigens and markers in renal cell carcinoma

Tumor markers are mainly used to diagnose specific malignancies. The methods commonly involve immunohistochemistry and cytogenetics, including FISH and RT-PCR. In RCC, the investigated tumor markers (summarized in Table 1) show additional prognostic value over classical prognostic factors such as stage and grade. These markers can be used for better patient selection, a more accurate individualization of treatment, and improved follow-up. Nevertheless, their definitive value must be reconfirmed in larger patient cohorts. Ultimately, these factors should be shown to be of value in a prospective well-controlled trial. One of the most promising new techniques involves gene expression profiling of solid tumors. This cDNA microarray technique applied in RCC has improved understanding of the molecular mechanism of the underlying tumor genesis and its correlation to the clinical course. Tumor antigens that are specific for RCC (eg, G250) and that induce a specific immune response can be used for vaccine treatment modalities. With the use of dendritic cells, antigen presentation can be improved. Several phase I studies are currently underway. More research is needed to obtain better antigens and markers in RCC to improve insight into the molecular mechanism of the development of RCC, to improve the selection of patients for treatment, and to increase its effectiveness.

Expression of CD44 protein in renal cell carcinomas: association with p53 expression

CD44 is an adhesion molecule involved in cell-to-cell and cell-to-matrix interactions. Recent evidence indicates a role of CD44 in tumor growth and metastatic potential of tumor cells. Moreover, it is widely known that the p53 tumor suppressor gene controls cell proliferation and loss of its normal function may lead to carcinogenesis. To investigate the role of these biomarkers in renal cancer, we analyzed the immunohistochemical distribution of CD44's expression on formalin fixed paraffin embedded tissue from 67 renal cell carcinomas and correlated with clinicopathologic parameters as well as with p53 suppressor gene expression. The monoclonal antibodies CD44 and p53 were applied to the tissues using the streptavidin biotin peroxidase method after microwave antigen retrieval. For CD44 and p53 more than 10% membranous and 5% nuclear staining, respectively, were estimated as positive. CD44's membranous immunoreactivity was detected in 24/67 tumors (35%) and mostly in carcinomas of clear/granular cell type. Nine tumors expressed nuclear immunoexpression of p53 protein (13.4%). Statistically significant correlation was noted between CD44 expression and nuclear grade (P < 0.001), tumor stage (P < 0.001), vascular invasion (P < 0.05) and p53 expression (P < 0.01). These results suggest that CD44s and p53 are markers of tumor progression in renal cell cancer.

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.

Up-regulation of the tumour-associated marker CD44V6 in experimental kidney disease

CD44 is an adhesion molecule involved in a wide range of cell-cell and cell-matrix interactions. The standard form of CD44 (CD44S) is a 85-90-kD glycoprotein, but alternative splicing of RNA encoding 10 variable exons (V1-V10) can give rise to many different CD44 variant protein isoforms of higher molecular weight. CD44 isoforms containing the V6 exon play a crucial role in tumour metastasis and lymphocyte activation. However, the role of CD44V6 in the kidney is unknown. The aim of this study was to examined renal CD44V6 expression in health, disease and in vitro. Immunohistochemistry staining with the V6-specific 1.1ASML antibody identified constitutive CD44V6 expression by occasional cortical tubular epithelial cells and medullary tubules in normal rat kidney. In immune-induced kidney disease (rat anti-glomerular basement membrane glomerulonephritis), there was a marked increase in CD44V6 expression by cortical tubules, particularly in areas of tubulointerstitial damage, which was associated with focal macrophage infiltration. There was also a marked increase in CD44V6 expression by damaged tubules in a model of non-immune kidney disease (unilateral ureteric obstruction). Reverse transcription-polymerase chain reaction revealed a complex pattern of CD44V6-containing mRNA isoforms in normal rat kidney. This pattern of CD44V6 splicing was essentially unaltered in disease. The NRK52E normal rat kidney tubular epithelial cell line expresses both CD44S and CD44V6. Stimulation of NRK52E cells with IL-1 or transforming growth factor-beta 1 induced a two-to-five-fold increase in the expression of both CD44S and CD44V6. Furthermore, triggering of NRK52E cells by antibodies to CD44S or CD44V6, but not isotype control antibodies, induced secretion of monocyte chemoattractant protein-1. In conclusion, this study has identified expression of the tumour-associated marker CD44V6 in tubular epithelial cells in normal and diseased rat kidney, and suggests that signalling through the CD44V6 molecule may participate in the pathogenesis of experimental kidney disease.

Expression of CD44 adhesion molecules in nonpapillary renal cell carcinoma and normal kidneys

OBJECTIVES

To analyze the relationship between the alterations in the expression of the CD44 gene in nonpapillary renal cell carcinoma (RCC) and several clinicopathologic factors.

METHODS

The expression of the CD44 gene in 10 human RCC cell lines, 60 nonpapillary RCC tumor samples, and 15 normal kidney samples was investigated by reverse-transcription polymerase chain reaction (RT-PCR) using a set of primers capable of amplifying all CD44 variant isoforms. The results were analyzed with respect to several clinicopathologic factors.

RESULTS

Nine of the 10 human RCC cell lines predominantly expressed the standard CD44 isoform (CD44s); CD44v10 was the major isoform in the 10th RCC cell line. The 15 normal kidney samples revealed the identical CD44 gene expression pattern; that is, CD44s, CD44v8-10, and CD44v10 were detectable in normal kidneys, and among them, CD44s was expressed most dominantly. In the 60 nonpapillary RCC samples, CD44s, CD44v8-10, and CD44v10 were the major isoforms in 46 (77%), 11 (18%), and 3 (5%) cases, respectively. Furthermore, the incidence of the predominant expression of CD44v8-10 in high-stage RCC was significantly higher than that in low-stage RCC. CD44s was more frequently expressed as a major isoform in clear cell RCC than in other histologic types of RCC.

CONCLUSIONS

The results of this study show that the alternative splicing pattern of CD44 gene in RCC is different in each histologic type of RCC and suggest that CD44v8-10 upregulation in the progression of nonpapillary RCC is important.