Vase mini-exon usage by NCAM is not restricted to tumours of neuroectodermal origin

The neural cell adhesion molecule (NCAM) plays an important role in normal development. Many variants of NCAM are generated through post-transcriptional and post-translational modifications. These variants are tissue-specific and their expression is developmentally regulated. NCAM is also re-expressed in a number of human tumours, including neuroblastoma, rhabdomyosarcoma, Wilms' tumour and Ewing's sarcoma. We have characterized the NCAM variants associated with rhabdomyosarcoma. Polysialylated NCAMs are present in this tumour and, after neuraminidase treatment, they resolve into 2 bands of 140 and 120 kDa. These data were corroborated by Northern-blot analysis where mRNA species of 6.7 and 5.5 kb are detected. These mRNA code for the 140- and 120-kDa NCAM proteins respectively. PCR analysis shows that the previously described VASE mini-exon is also present in NCAM found in rhabdomyosarcoma. The VASE mini-exon, spliced at exon 7-8 junctions, has previously been detected in neural and heart NCAM, as well as in NCAMs found in human small-cell lung carcinoma (SCLC). DNA sequencing confirmed that the VASE mini-exon in rhabdomyosarcoma is identical to that found in neuroblastoma and SCLC.