Aberrant promoter methylation and silencing of the RASSF1A gene in pediatric tumors and cell lines

Malignant abdominal masses in children: quick guide to evaluation and diagnosis

A palpable mass in the abdomen of a child is a serious finding. In this article the authors present their single-institution experience of how these malignancies present and their distribution by age and diagnosis. The most common abdominal malignancies diagnosed in the pediatric population include neuroblastoma, Wilms' tumor, hepatoblastoma, lymphoma, and germ cell tumors. This article provides the busy general pediatrician with some guidelines of how to proceed after discovering a suspiciousmass.

Hypomethylation and hypermethylation of DNA in Wilms tumors

We quantitatively analysed hypermethylation at CpG islands in the 5' ends of 12 genes and one non-CpG island 5' region (MTHFR) in 31 Wilms tumors. We also determined their global genomic 5-methylcytosine content. Compared with various normal postnatal tissues, approximately 40-90% of these pediatric kidney cancers were hypermethylated in four of the genes, MCJ, RASSF1A, TNFRSF12 and CALCA as determined by a quantitative bisulfite-based assay (MethyLight). Interestingly, the non-CpG island 5' region of MTHFR was less methylated in most tumors relative to the normal tissues. By chromatographic analysis of DNA digested to deoxynucleosides, about 60% of the Wilms tumors were found to be deficient in their overall levels of DNA methylation. We also analysed expression of the three known functional DNA methyltransferase genes. No relationship was observed between global genomic 5-methylcytosine levels and relative amounts of RNA for DNA methyltransferases DNMT1, DNMT3A, and DNMT3B. Importantly, no association was seen between CpG island hypermethylation and global DNA hypomethylation in these cancers. Therefore, the overall genomic hypomethylation frequently observed in cancers is probably not just a response or a prelude to hypermethylation elsewhere in the genome. This suggests that the DNA hypomethylation contributes independently to oncogenesis or tumor progression.

Novel complex integrating mitochondria and the microtubular cytoskeleton with chromosome remodeling and tumor suppressor RASSF1 deduced by in silico homology analysis, interaction cloning in yeast, and colocalization in cultured cells

Availability of the complete sequence of the human genome and sequence homology analysis has accelerated new protein discovery and clues to protein function. Protein-protein interaction cloning suggests multisubunit complexes and pathways. Here, we combine these molecular approaches with cultured cell colocalization analysis to suggest a novel complex and a pathway that integrate the mitochondrial location and the microtubular cytoskeleton with chromosome remodeling, apoptosis, and tumor suppression based on a novel leucine-rich pentatricopeptide repeat-motif-containing protein (LRPPRC) that copurified with the fibroblast growth factor receptor complex. One round of interaction cloning and sequence homology analysis defined a primary LRPPRC complex with novel subunits cat eye syndrome chromosome region candidate 2 (CECR2), ubiquitously expressed transcript (UXT), and chromosome 19 open reading frames 5 (C19ORF5) but still of unknown function. Immuno, deoxyribonucleic acid (DNA), and green fluorescent protein (GFP) tag colocalization analyses revealed that LRPPRC appears in both cytosol and nuclei of cultured cells, colocalizes with mitochondria and beta-tubulin rather than with alpha-actin in the cytosol of interphase cells, and exhibits phase-dependent organization around separating chromosomes in mitotic cells. GFP-tagged CECR2B was strictly nuclear and colocalized with condensed DNA in apoptotic cells. GFP-tagged UXT and GFP-tagged C19ORF5 appeared in both cytosol and nuclei and colocalized with LRPPRC and beta-tubulin. Cells exhibiting nuclear C19ORF5 were apoptotic. Screening for interactive substrates with the primary LRPPRC substrates in the human liver complementary DNA library revealed that CECR2B interacted with chromatin-associated TFIID-associated protein TAFII30 and ribonucleic acid splicing factor SRP40, UXT bridged to CBP/p300-binding factor CITED2 and kinetochore-associated factor BUB3, and C19ORF5 complexed with mitochondria-associated NADH dehydrogenase I and cytochrome c oxidase I. C19ORF5 also interacted with RASSF1, providing a bridge to apoptosis and tumor suppression.