A total of 48 cases of CCSK, Wilms tumor (WT), renal rhabdoid tumor, mesoblastic nephroma, renal Ewing sarcoma and neuroblastoma were included in the study.All cases were stained with cyclin D1.
DNA methylation changes in neuroblastoma affect not only promoters but also intragenic and intergenic regions at cytosine-phosphate-guanine (CpG) and non-CpG sites, and target functional chromatin domains of development and cancer-related genes such as CCND1.
Cyclin D1 immunohistochemistry helps distinguish CCSK from blastemal WT and metanephric adenoma and rhabdoid tumors, but not from neuroblastomas and mesoblastic nephromas.
In addition, we observed that neuroblastoma is associated to significantly higher levels of cyclin D1 as compared to both ganglioneuroma and ganglioneuroblastoma.
In particular, differential methylation in CCND1 affected mostly an evolutionary conserved functionally relevant 3' untranslated region, suggesting that hypomethylation outside promoter regions may play a role in NB pathogenesis.
To identify upstream regulators, we searched in mRNA profiles of neuroblastoma tumor series for transcription factors with expression patterns correlating to Cyclin D1.
This suggests an involvement of G(1)-regulating genes in neuronal differentiation processes which we further evaluated using RNA interference against Cyclin D1 and its kinase partners CDK4 and CDK6 in several neuroblastoma cell lines.
The main target for induction of cyclin D1 transcription by oncogenic ras in neuroblastoma cells is a cyclic AMP response element (CRE) located in proximal promoter sequences, and T3 represses the transcriptional activity of b-Zip transcription factors such as CREB (CRE-binding protein) or ATF-2 (activation transcription factor 2) that are direct targets of Rsk2 and bind to this sequence.
Our data suggest that dysregulation of cyclin D1 (a candidate bcl-1, PRAD1 oncogene) can be involved in the pathogenesis of some additional tumor types (e.g., sarcomas and neuroblastomas) besides those reported for amplification and/or mRNA overexpression of this oncogene.(ABSTRACT TRUNCATED AT 250 WORDS)