Association of renal cell carcinoma phenotype and prognosis with differential changes of substance p and substance P degrading enzyme levels

Renal cell carcinoma (RCC) is a malignancy with a rising incidence and has effective treatment modalities for a limited group of patient which does not response well to conventional chemotherapy and radiotherapy. Hence recently, the identification of molecules involved in the development and progression of this disease is of high priority. ADAMs (A Disintegrin A Metaloproteases) are a family of metaloproteases and increased expression of ADAM9, ADAM10 and ADAM17 was associated with tumor progression in some but not in all studies. Similarly effects of different levels of neprilisin (NEP), a peptidase which is responsible for hydrolyzing neuropeptides, on tumorogenesis and tumor progression is not clear. These discrepancies may reflect the fact that changes in protein levels do not always correlate with the functional changes. Changes in alpha-secretase activity as an assay for ADAM9, 10 and 17 functions in freshly frozen 60 consecutive renal cell carcinoma samples were examined. Adjacent renal tissue ~2cm distant to primary tumor was also used. Changes in the level and localization of the ADAMs were evaluated in both tumor tissue and neighboring uninvolved kidney tissue by immunohistochemistry. Pathological grading of the samples was calculated using immunreactivity scale. Subtypes of RCC and the number of patients examined were as follows: Clear cell carcinoma (n=34) (58%), papillary cell carcinoma (n=12) (16%), Cromophobe cell type (n=8) (11%) and other types (n=6). Alpha-secretase activity and neprylisin was significantly lower (78% and 57%) in tumor tissue compared to the neighboring renal tissue regardless of tumor type (p < 0,0001 paired t test). Statistical analysis done according to tumor types. In papillary type RCC NEP and alpha secretase activity in tumor tissue is markedly and statistically significant lower than neighbouring uninvolved kidney. NEP level decrease was higher than alpha secretase decrease. Renal alpha secretase activity in RCC was significantly higher than alpha secretase activity in patients underwent simple nephrectomy for nonfunctioning kidney because of nephrolitiazis (p<0,05) (2-4 times). But in chromophobe type RCC patients renal neprylisin activity was significantly lower (44%) than patients underwent simple nephrectomy for nonfunctioning kidney because of nephrolitiazis. Immunostaining for ADAM9 demonstrated that ADAM9 levels were markedly lower in tumor tissue compared to neighboring renal tissue regardless of cell type. ADAM17 levels however were lower in early disease compared to advanced carcinoma (metastatic disease or with T3a tumors) as well as neighboring renal tissue in papillary type but not clear cell carcinoma. In fact decreased expression of ADAM17 in advanced carcinoma of clear cell was observed. ADAM10 levels were significantly lower in all types compared to neighboring renal tissue and there was no difference between early and advanced disease. Overall, of all ADAMs, ADAM17 was expressed the highest. The aberrant (cytoplasmic) expression of all ADAMs however was observed in tumor tissue explaining the decreased alpha secretase activity. Our results also suggested that aberrant expression of ADAM17 may promote tumor progression in papillary cell type. The role of alpha-secretase activity in tumor progression as well as tumorogenesis is not well-known. Our results demonstrated for the first time that alpha-secretase activity was significantly decreased in RCC which might be involved in pathogenesis. Further studies however are needed to evaluate possible anti-tumoral effects of alpha-secretase activity. Key words: Renal cell carcinoma, Substance P, NEP/CD10, ADAM, alpha secretase.