Jan J.M. van Groningen

Expression of nma, a novel gene, inversely correlates with the metastatic potential of human melanoma cell lines and xenografts.

nma, a novel gene, was isolated by using a subtractive hybridization technique in which the gene expression was compared in a panel of human melanoma cell lines with different metastatic potential. nma mRNA expression (1.5 kb) is high in poorly metastatic human melanoma cell lines and xenografts and completely absent in highly metastatic human melanoma cell lines. Fluorescence in situ hybridization combined with the analysis of a panel of human‐rodent somatic cell hybrids indicated that the nma gene is located on human chromosome 10, in the region p11.2–p12.3. Sequence analysis of nma showed no homologies with other known genes or proteins, except for several partially sequenced cDNAs. The predicted amino acid sequence suggests that the protein encoded by nma contains a transmembrane domain. Expression of nma is high in human kidney medulla, placenta and spleen, low in kidney cortex, liver, prostate and gut and absent in lung and muscle. Whereas nma is not expressed in normal skin tissue, expression is high in melanocytes and in 3 out of 11 melanoma metastases tested.

Impairment of MAD2B–PRCC interaction in mitotic checkpoint defective t(X;1)-positive renal cell carcinomas

The papillary renal cell carcinoma (RCC)-associated (X;1)(p11;q21) translocation fuses the genes PRCC and TFE3 and leads to cancer by an unknown molecular mechanism. We here demonstrate that the mitotic checkpoint protein MAD2B interacts with PRCC. The PRCCTFE3 fusion protein retains the MAD2B interaction domain, but this interaction is impaired. In addition, we show that two t(X;1)-positive RCC tumor cell lines are defective in their mitotic checkpoint. Transfection of PRCCTFE3, but not the reciprocal product TFE3PRCC, disrupts the mitotic checkpoint in human embryonic kidney cells. Our results suggest a dominant-negative effect of the PRCCTFE3 fusion gene leading to a mitotic checkpoint defect as an early event in papillary RCCs.

Transformation capacities of the papillary renal cell carcinoma-associated PRCCTFE3 and TFE3PRCC fusion genes.

A recurrent chromosomal abnormality associated with a subset of papillary renal cell carcinomas is t(X;1)(p11;q21). This translocation leads to the formation of two fusion genes, TFE3PRCC and the reciprocal product PRCCTFE3. Both fusion genes are expressed in t(X;1)-positive renal cell carcinomas and contain major parts of the coding regions of the parental transcription factor PRCC and TFE3 genes, respectively. To find out whether these fusion genes possess transforming capacity, we transfected NIH3T3 and rat-1 cells with the fusion products, either separately or combined. When using soft agar assays, we observed colony formation in all cases. NIH3T3 cells transfected with PRCCTFE3 or PRCCTFE3 together with TFE3PRCC yielded the highest colony forming capacities. Examination of other characteristics associated with malignant transformation, i.e., growth under low-serum conditions and formation of tumors in athymic nude mice, revealed that cells transfected with PRCCTFE3 exhibited all these transformation-associated characteristics. Upon transfection of the fusion products into conditionally immortalized kidney cells, derived from the proximal tubules of an H-2Kb-tsA58 transgenic mouse, and consecutive incubation under non-permissive conditions, growth arrest was observed, followed by differentiation except for those cells transfected with PRCCTFE3. Therefore, we conclude that PRCCTFE3 may be the t(X;1)-associated fusion product that is most critical for the development of papillary renal cell carcinomas.

nmd, a novel gene differentially expressed in human melanoma cell lines, encodes a new atypical member of the enzyme family of lipases

© 1997 Federation of European Biochemical Societies.

Increased expression of retroviral sequences in progressionally advanced rat prostatic tumors.

Differential hybridization analysis revealed two cDNA clones, pBUS19 and pBUS30, to be overexpressed in progressionally advanced rat prostatic tumors. Northern blot analysis suggested the clones to be related although no homology in nucleotide sequence could be shown. Isolation and characterization of a pBUS19-related clone, pJG116, and computer-assisted database comparison showed that all three clones could be mapped within a rat-specific endogenous retrovirus. The importance of overexpression of retroviral sequences in advanced prostatic cancer remains unclear.