Characterization of Wnt/ß-catenin signaling in rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and accounts for about 5% of all malignant paediatric tumours. ß-Catenin, a multifunctional nuclear transcription factor in the canonical Wnt signaling pathway, is active in myogenesis and embryonal somite patterning. Dysregulation of Wnt signaling facilitates tumour invasion and metastasis. This study characterizes Wnt/ß-catenin signaling and functional activity in paediatric embryonal and alveolar RMS. Immunohistochemical assessment of paraffin-embedded tissues from 44 RMS showed ß-catenin expression in 26 cases with cytoplasmic/membranous expression in 9/14 cases of alveolar RMS, and 15/30 cases of embryonal RMS, whereas nuclear expression was only seen in 2 cases of embryonal RMS. The potential functional significance of ß-catenin expression was tested in four RMS cell lines, two derived from embryonal (RD and RD18) RMS and two from alveolar (Rh4 and Rh30) RMS. Western blot analysis demonstrated the expression of Wnt-associated proteins including ß-catenin, glycogen synthase kinase-3ß, disheveled, axin-1, naked, LRP-6 and cadherins in all cell lines. Cell fractionation and immunofluorescence studies of the cell lines (after stimulation by human recombinant Wnt3a) showed reduced phosphorylation of ß-catenin, stabilization of the active cytosolic form and nuclear translocation of ß-catenin. Reporter gene assay demonstrated a T-cell factor/lymphoid-enhancing factor-mediated transactivation in these cells. In response to human recombinant Wnt3a, the alveolar RMS cells showed a significant decrease in proliferation rate and induction of myogenic differentiation (myogenin, MyoD1 and myf5). These data indicate that the central regulatory components of canonical Wnt/ß-catenin signaling are expressed and that this pathway is functionally active in a significant subset of RMS tumours and might represent a novel therapeutic target.

Somatic mutations and progressive monosomy modify SAMD9-related phenotypes in humans.

It is well established that somatic genomic changes can influence phenotypes in cancer, but the role of adaptive changes in developmental disorders is less well understood. Here we have used next-generation sequencing approaches to identify de novo heterozygous mutations in sterile α motif domain-containing protein 9 (SAMD9, located on chromosome 7q21.2) in 8 children with a multisystem disorder termed MIRAGE syndrome that is characterized by intrauterine growth restriction (IUGR) with gonadal, adrenal, and bone marrow failure, predisposition to infections, and high mortality. These mutations result in gain of function of the growth repressor product SAMD9. Progressive loss of mutated SAMD9 through the development of monosomy 7 (-7), deletions of 7q (7q-), and secondary somatic loss-of-function (nonsense and frameshift) mutations in SAMD9 rescued the growth-restricting effects of mutant SAMD9 proteins in bone marrow and was associated with increased length of survival. However, 2 patients with -7 and 7q- developed myelodysplastic syndrome, most likely due to haploinsufficiency of related 7q21.2 genes. Taken together, these findings provide strong evidence that progressive somatic changes can occur in specific tissues and can subsequently modify disease phenotype and influence survival. Such tissue-specific adaptability may be a more common mechanism modifying the expression of human genetic conditions than is currently recognized.

Enterobius vermicularis and colitis in Children.

OBJECTIVES: We observed a cohort of children presenting with rectal bleeding that were identified as having Enterobius vermicularis at colonoscopy and questioned the reliability of conventional diagnostic methods of identifying E. vermicularis. PATIENTS AND METHODS: The study was retrospective in nature and subjects were investigated by colonoscopy between May 1997 and December 1999. Patients were identified as having E. vermicularis infestation by direct visualisation of the adult worms at colonoscopy. Patients were treated with mebendazole and a record of their clinical response documented. RESULTS: A total of 180 colonoscopic examinations were performed during the study period. E. vermicularis was identified macroscopically in 31 cases (17.2%). The symptom profile of patients with E. vermicularis were abdominal pain, 19 of 26 (73%); rectal bleeding, 16 of 26 (62%); chronic diarrhoea, 13 of 26 (50%) and weight loss, 11 of 26 (42%). Ova cysts and parasites were identified in none of the saline swabs analysed in 20 patients. Sellotape testing was performed in only 4 patients and was negative in all. Of the 26 children, 21 (81%) demonstrated histopathological features of nonspecific colitis. There was clinical resolution of symptoms in 19 of 23 patients. CONCLUSIONS: We suggest that in patients with symptoms suggestive of inflammatory bowel disease, E. vermicularis infestation must be excluded as a common cause of nonspecific colitis. We also suggest that diagnostic tests such as saline swabs and Sellotape testing may be lacking in sensitivity.