Diverse mutational spectrum in the 13q14 chromosomal region in a Brazilian cohort of retinoblastoma.

Retinoblastoma is a rare childhood tumor caused by the inactivation of both copies of the RB1 gene. Early diagnosis and identification of heritable RB1 mutation carriers can improve the disease outcome and management via genetic counseling. We used the Multiplex Ligation-dependent Probe Amplification (MLPA) method to analyze the RB1 gene and flanking regions in blood samples from 159 retinoblastoma patients previously negative for RB1 point mutations via Sanger sequencing. We detected a wide spectrum of germline chromosomal alterations, ranging from partial loss or duplication of RB1 to large deletions spanning RB1 and adjacent genes. Mutations were validated via karyotyping, fluorescent in situ hybridization (FISH), SNP-arrays (Single Nucleotide Polymorphism-arrays) and/or quantitative relative real-time PCR. Patients with leukocoria as a presenting symptom showed reduced death rate (p = 0.013) and this sign occurred more frequently among carriers of two breakpoints within RB1 (p = 0.05). All unilateral cases presented both breakpoints outside of RB1 (p = 0.0075). Patients with one breakpoint within RB1 were diagnosed at earlier ages (p = 0.017). Our findings characterize the mutational spectrum of a Brazilian cohort of retinoblastoma patients and point to a possible relationship between the mutation breakpoint location and tumor outcome, contributing to a better prospect of the genotype/phenotype correlation and adding to the wide diversity of germline mutations involving RB1 and adjacent regions in retinoblastoma.

Cancer genetic counseling in public health care hospitals: the experience of three Brazilian services.

In Brazil, genetic counseling is usually available in university-affiliated medical genetics services located in tertiary centers that provide cancer diagnosis and treatment. The present study aims to describe the structure and characteristics of three cancer genetic services in Brazilian public health care hospitals and discuss alternatives for the identification and prevention of hereditary cancer syndromes in developing countries. The three services presented here are similar in their structure, routine procedures for cancer risk estimation and criteria for the indication of genetic testing. They all demand that genetic counseling be an essential part of the cancer risk evaluation process, before and after cancer predisposition testing. However, when high-risk patients are identified, all services describe difficulties in the access and continuity of genetic and medical services to the patient and his/her at-risk relatives. The services differ in the type of population served, reflecting distinct referral guidelines. This study emphasizes the importance of the creation of new cancer genetic services in other Brazilian regions and the necessity for establishing a collaborative network to facilitate the diagnosis and research of cancer genetic syndromes.

Array CGH Analysis of Paired Blood and Tumor Samples from Patients with Sporadic Wilms Tumor.

Wilms tumor (WT), the most common cancer of the kidney in infants and children, has a complex etiology that is still poorly understood. Identification of genomic copy number variants (CNV) in tumor genomes provides a better understanding of cancer development which may be useful for diagnosis and therapeutic targets. In paired blood and tumor DNA samples from 14 patients with sporadic WT, analyzed by aCGH, 22% of chromosome abnormalities were novel. All constitutional alterations identified in blood were segmental (in 28.6% of patients) and were also present in the paired tumor samples. Two segmental gains (2p21 and 20q13.3) and one loss (19q13.31) present in blood had not been previously described in WT. We also describe, for the first time, a small, constitutive partial gain of 3p22.1 comprising 2 exons of CTNNB1, a gene associated to WT. Among somatic alterations, novel structural chromosomal abnormalities were found, like gain of 19p13.3 and 20p12.3, and losses of 2p16.1-p15, 4q32.5-q35.1, 4q35.2-q28.1 and 19p13.3. Candidate genes included in these regions might be constitutively (SIX3, SALL4) or somatically (NEK1, PIAS4, BMP2) operational in the development and progression of WT. To our knowledge this is the first report of CNV in paired blood and tumor samples in sporadic WT.