Intra-tumor genetic heterogeneity in Wilms tumor samples

SUMMARY Childhood renal tumors account for ~7% of all childhood cancers, and most cases are embryonic Wilms' tumors (WT). Children with WT are usually treated by either COG or SIOP. The later treats the children using preoperative chemotherapy, but both have around 90% of overall survival in five years. WT is a genetically heterogeneous group with a low prevalence of known somatic alterations. Only around 30% of the cases present mutation in known genes, and there is a relatively high degree of intra-tumor genetic heterogeneity (ITGH). Besides potentially having an impact on the clinical outcome of patients, ITGH may interfere with the search for molecular markers that are prospectively being tested by COG and SIOP. In this review, we present the proposal of the current UMBRELLA SIOP Study 2017/Brazilian Renal Tumor Group that requires the multi-sampling collection of each tumor to better evaluate possible molecular markers, as well as to understand WT biology

RESUMO Os tumores renais pediátricos correspondem a aproximadamente 7% de todos os tumores infantis, sendo o mais frequente o tumor de Wilms (TW). Crianças com TW são geralmente tratadas seguindo dois distintos protocolos terapêuticos (COG ou SIOP), sendo que no último, os pacientes recebem tratamento quimioterápico pré-operatório. Ambos apresentam sobrevida global em cinco anos em torno de 90%. TW é geneticamente heterogêneo, apresentando baixa prevalência de alterações somáticas conhecidas, com cerca de 30% dos casos apresentando mutações em genes conhecidos e um alto grau de heterogeneidade genética intratumoral (HGIT). Além de potencialmente ter um impacto sobre o desfecho clínico dos pacientes, a HGIT pode interferir na busca de marcadores moleculares que estão sendo testados prospectivamente pelos grupos COG e Siop. Nesta revisão, apresentamos a proposta do atual estudo Umbrella Siop 2017/Grupo de Tumores Renais Brasileiros (GTRB), que orienta a coleta de três diferentes regiões do tumor para melhor avaliar possíveis marcadores moleculares, bem como para compreender a biologia do TW.

Growth inhibition of breast cancer cell line MCF-7 by siRNA silencing of Wilms tumor 1 gene.

BACKGROUND: RNA interference (RNAi) is sequence-specific inhibition of gene expression induced by double-stranded RNA. OBJECTIVE: Define the role of Wilms tumor 1 gene (WT1) in breast cancer oncogenesis using RNAi. MATERIAL AND METHOD: MCF-7 breast cancer cells, which express a high level of WT1, were transfected with synthetic small interfering RNA (siRNA) targeting WT1 (siRNA(WT1)) resulting in inhibition of WTI expression, as well as growth, in a dose- and time-dependent manner. RESULT: The minimum concentration of siRNA(WT1) for growth inhibition and WT1 silencing was 25 nM and 50 nM respectively. WT1 expression was completely abolished at 200 nM siRNA,. CONCLUSION: These data suggest that WTI1is indispensable for the survival of breast cancer MCF-7 cell line.

Molecular biology and genetics affecting pediatric solid tumors

Since the discovery of oncogenes more than 20 years ago, it has been proven that cancer is a genetically determined disease. Multiple genetic alteration occurs during the course of an illness for neoplasia to develop. Transformation of positive cell growth regulators (oncogenes) and inactivations of negative cell growth regulators (tumor suppressor genes) merge to express a malignant phenotype. These genetic alterations occur as chromosomal translocations, deletions, inversion, amplification or point mutation. The objective of this review is to introduce basic concepts of molecular biology and describe the molecular genetics and biologic clinical findings of the most important solid malignant tumors in children, namely Neuroblastoma, Wilms and Rhabdomyosarcoma. It is the oncology surgeons responsibility to learn basic molecular genetics and tumor biology to provide rational and appropriate care in the setting of multidisciplinary management. Identifications of new oncogenes will continue to be important milestones in diagnosis, early detection of tumor recurrence, and as potential targets for gene therapy. Fusion proteins generated by mutated translocations are true tumor specific antigens and potential targets for therapy. The predicament is that they are proteins needing therapeutic manipulation within the tumor cell nuclei. Technological advances in molecular and genetics will develop tools necessary to manipulate the cell nuclear DNA and target cancer cell

Analysis of the p53 gene by PCR-SSCP in ten cases of WilmsÆ tumor

CONTEXT: Mutations of the p53 tumor suppressor gene are the most frequent alterations observed in human neoplasias affecting adults. In pediatric oncology, however, they have seldom been identified. WilmsÆ tumor is a renal neoplasia commonly occurring in children and is associated with mutations of the WT1 gene. The correlation between WilmsÆ tumor and alterations of the p53 gene has not been well established, with a low frequency of mutations having been reported in this type of tumor. Mutation may be associated with advanced stage disease and unfavorable histology. OBJECTIVE: To screen for mutations of the p53 gene by the PCR-SSCP method and DNA sequencing in cases of WilmsÆ tumor sug-gestive of mutation. DESIGN: Case Report. CASE REPORT: Evaluations of exons 5-9 of the p53 gene in DNA samples extracted by PCR-SSCP from 10 WilmsÆ tumors in children at different stages, and DNA sequencing. Changes in SSCP analy-sis were observed in exon 8 in two samples. The probable muta-tions were not confirmed by DNA sequencing. The absence of point mutations in p53 gene observed in the 10 samples of WilmsÆ tumor studied agrees with literature data, with DNA sequencing being of fundamental importance for the confirmation of possible mutations

Genomic imprinting relevant to genetic diseases.

Genomic imprinting is a new concept proposed to explain unusual observations in early mammalian development, the occurrence of certain genetic diseases, genetic anticipation or incomplete penetrance, and tumorigenesis. The basic mechanism of the imprinting has remained obscure, although DNA-methylation, chromatin structure, and/or DNA replication may have a role. Genomic imprinting is a biological phenomenon determined by an evolutionally acquired, underlying system that may control harmonious development and growth in mammals. It is also relevant to the occurrence of some genetic disorders in man.

Monitoring of WT-1 gene expression in peripheral blood of patients with acute leukemia by semiquantitative RT-PCR; possible marker for detection of minimal residual leukemia

The expression of the WT-1 gene which is found exclusively in human leukemic blasts frequently disappears from bone marrow of leukemia patients in complete remission (CR). Using semiquantitative RT-PCR, we investigated the expression of the WT-1 gene in peripheral bloods (PBs) of 33 patients with acute leukemia (AML 26; ALL 7) and monitored its expression after achievement of CR. None of the 6 normal controls expressed detectable levels of WT-1 transcripts (< 10(-4), background level), whereas 31 (93.9%) of 33 patients expressed variable levels of WT-1 transcripts (range, 10(-4) to 10(1)) at diagnosis. The level of WT-1 expression was not different between AML and ALL. By monitoring WT-1 gene expression in PB of 31 patients during CR, 5 patients relapsed (two from the 18 patients with undetectable levels of WT-1 gene expression and three from the 13 with WT-1 gene expression in low levels). Three of the 5 relapsed patients showed preceding reappearance or rise of WT-1 gene expression. From these results, we reconfirmed that the WT-1 gene is a pan-acute leukemic marker, which can be used to monitor minimal residual leukemia (MRL) after chemotherapy or in patients with CR.

Analise citogenética de três casos de tumor de wilms da infância / Cytogenetics analysis of 3 cases of children with Wilms tumor

Relatamos os resultados da análise citogenética de três casos de tumor de wilms em crianças. O estudo cromossômico foi realizado a partir do material obtido de cultura de curta duraçäo de células tumorais. observamos alteraçöes numéricas e estruturais, incluindo aberraç 8es estruturais do cromossomo 1 e trissomiais dos cromossomos 8 e 12