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Wilms tumor is one of the most common pediatric malignant tumors of the kidney. Although the WT1 gene, located at 11p13, has been proven to be implicated in the development of Wilms tumor, other genes such as MYCN are also involved. The purpose of this study is to genetically characterize a Wilms tumor metastasis xenotransplanted in nude mice. Immunogenotype evolution of the xenografts material was monitored for 29 months using molecular techniques, fluorescent in situ hybridization and multiplex ligation-dependent probe amplification, in addition to immunohistochemistry in tissue microarrays. Genetic alterations present in the original tumor and retained in the xenotransplanted tumor were located in 1q, 3, 6, −7p, 7q, 8, −9p, 9q, 12. The multiplex ligation-dependent probe amplification detected a nondeleted status of genes located close to WT genes, except for a deletion of the EGFR gene (located at 7p11.2) and the GHRHR gene (located at 7p15), both flanking the WT5 gene. The MYCN gene (2p24 exon 3) and DDX1 gene (2p24 exons 2, 7, 15, and 24) were gained in passage 4 and the following passages. MYCN expression was positive from the beginning, without evidence of MYCN gain by fluorescent in situ hybridization. Histopathologic and growth rate changes were observed at those passages where low extra copy number of MYCN was present. In addition to other genetic abnormalities, the WT5 gene located at 7p13-14 is deleted and the MYCN gene gain began after 16 months in vivo evolution in athymic nude mice. MYCN is already used as a stratifying marker in neuroblastomas, and it may be also useful in implementing MYCN testing in prospective studies of Wilms tumors.

Osteosarcoma (OS) displays complex karyotypes with numerical changes as well as structural abnormalities suggesting that several oncogenes and tumor suppressor genes may be implicated in the biology of OS. The aim of our study was to investigate the possible implication of the molecular alterations of the G1to S-phase checkpoint genes in the pathogenesis of OS. We analyzed samples from 29 patients and found molecular alterations of the RBand TP53genes in 6 (21) and 3 (10) cases, respectively. Homozygous deletion of the INK4A/ARFlocus and methylation of INK4Awas detected in 3 (10) and 2 (7) cases, respectively. CDK4and MDM2co-amplification was observed in 1 case (3). Cyclin D3 is differentially expressed in a greater proportion than D1- and D2-type cyclins. Cytogenetically, all cases had complex karyotypes being especially significant the losses of the chromosomes 4, 13, and 17. As a whole, 11 of 29 (38) analyzed OS presented alterations in some of the analyzed G1to S-phase checkpoint genes. These alterations were more frequently present in adults (P0.032). All patients with genetic alterations in the G1/S-phase checkpoint died during their clinical follow-up, whereas more than 53 of the remaining cases were alive in this period (P0.007). Hence, in the pathogenesis of human OS, deregulation of the G1/S checkpoint genes, especially RB, TP53,and INK4/ARFlocus, plays an important role and defines a subgroup of patients with a poor outcome.

Our study was undertaken to better understand the role of G1/S transition abnormalities in the malignant progression of renal cell carcinomas (RCCs), exposed to long-term low doses of ionizing radiation (IR), from patients living in radiocontaminated areas of the Ukraine after the Chernobyl accident. We studied p16INK4Aand p15INK4Bgene alteration in association with oxidative stress markers, including inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2). We analyzed 88 samples collected from 22 patients with RCCs and with different exposure to IR. Homozygous deletion of the p16INK4Aand p15INK4Bgenes, as well as hypermethylation of the 5CpG island in the promoter region of the same genes, were analyzed by differential PCR and Methylation-Specific PCR respectively, in association with histopathology and immunohistochemical analysis of p16INK4Aand p15INK4Bproteins. COX2 and iNOS expression in the same tumors were likewise analyzed. Aberrant hypermethylation was observed in 7 (32) and 5 (23) cases accompanied, by immunohistochemical loss of expression for p16INK4Aand p15INK4Bgenes respectively, in both high stage and grade tumors from patients living in radiocontaminated areas, this being especially outstanding for the p16INK4Agene. An association with COX2 and less iNOS overexpression in the same tumors was observed. Our data suggest that inactivation of p16INK4Agene, but not p15INK4B, induced by increased oxidative stress generated by persistent chronic exposure to IR, could be one of the major pathways responsible for RCCs malignant progression.

This study describes a new case of Ewing sarcoma (ES)-peripheral primitive neuroectodermal tumor (pPNET) with unusual phenotype and fusion gene structure. The tumor located in the inguinal area of a 15-year-old boy showed a highly aggressive behavior with hematogenous metastases after intensive chemotherapy and bone marrow transplant, causing death 28 months after diagnosis. The tumor displayed a clear cell pattern, and several neuroectodermal markers proved positive both in the original tumor and in xenografts. This neuroectodermal character was confirmed by electron microscopy. Moreover, cytogenetically the tumor has an unusual chromosomal rearrangement, t(2;22)(q13;q22),t(3;18)(p21;q23), representing a new EWS-FEVfusion type in which exon 7 of EWSgene is fused with exon 2 of FEVgene. This is the third published study of an ES-pPNET showing EWS-FEVfusion described, but it is the first study of a tumor with the aforementioned fusion points. These findings support the genetic and morphologic heterogeneity existing within the group of ES-pPNET tumors.