Expression of calpain I messenger RNA in human renal cell carcinoma: Correlation with lymph node metastasis and histological type

Calpain, also named CANP (for calcium-activated neutral protease), is an in tracellular cytoplasmatic non-lysosomal cysteine endopeptidase that require s calcium ions for activity. Many substrates of the calpain isoenzymes, suc h as the transcription factors c-Fos and c-Jun, the tumor supressor protein p53, protein kinase C, pp60(c-src) and the adhesion molecule integrin, hav e been implicated in the pathogenesis of different human tumors, suggesting an important role of the calpains in malignant diseases. We now report dif ferential expression of the calpain I gene (CL I) in a variety of tumors, e xtending our study to a larger series of renal cell carcinomas. Using North ern-blot analysis, we studied calpain I expression in 30 renal cell carcino mas as compared with matched healthy tissues. Tumor samples were classified according to their histological type: 21 clear cell carcinomas, 4 chromoph obe carcinomas, 3 papillary carcinomas and 2 oncocytomas. in renal tumor sa mples, calpain I gene mRNA was expressed at highly variable levels, signifi cantly depending on the different histological types. Moreover, there was a correlation of higher calpain I expression with increased malignancy: with in the clear cell carcinoma subset, tumor samples with advanced nodal statu s (N1 and N2) showed a significantly higher calpain I expression than tumor s without metastasis to regional lymph nodes. Our data suggest an important role of calpain isoenzymes in carcinogenesis and tumor progression. (C) 19 99 Wiley-Liss, Inc.