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RB1 gene mutations in retinoblastoma and its clinical correlation.

ABSTRACT: PURPOSE:To find correlation between the type of mutations observed and the severity of the disease using multiple techniques like polymerase chain reactions (PCR), quantitative multiplex PCR, sequencing and RNA analysis. METHODS:Prospective, observational study. Patients who had been screened for mutations in the RB1 gene were included in the study. Patient details including demographic data; age and sex, laterality, international classification of intraocular retinoblastoma (ICIOR) staging, modality of management, histopathology high risk factors if the eyes were enucleated and metastasis rate were assessed. RESULTS:Seventy four patients were studied. Fifty three patients had bilateral and 21 unilateral disease. Complete genetic data was analyzed for 74 patients and complete clinical correlation was established for all the 49 patients with mutations. Of the total mutations identified, 11/49 (22.4%) of patients had large deletions, 12/49 (24.5%) had small deletions or insertions, 14/49 (28.6%) had nonsense mutations, 7/49 (14.3%) had splice mutations and 5/49 (10.2%) of patients had missense mutations. Four cases were familial. Group E ICIOR stage at presentation was noted in 40% of patients with large deletions, 33% with small deletions whereas 38.5% with splice mutations and 44.4% of patients with missense mutations presented with Group B ICIOR. Twenty five percentages of eyes with large deletions had high risk features on histopathology and one patient among these developed metastasis. CONCLUSION:Current laboratory testing of RB1 mutations may be feasible in determining the severity of the disease and patient counseling. The study provides a starting point for looking at correlations.

SUBMITTER: Ali MJ

PROVIDER: S-EPMC3729507 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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RB1 gene mutations in retinoblastoma and its clinical correlation.

Ali Mohammad Javed MJ Parsam Vidya Latha VL Honavar Santosh G SG Kannabiran Chitra C Vemuganti Geeta K GK Reddy Vijay Anand P VA

Saudi journal of ophthalmology : official journal of the Saudi Ophthalmological Society 20100206 4

<h4>Purpose</h4>To find correlation between the type of mutations observed and the severity of the disease using multiple techniques like polymerase chain reactions (PCR), quantitative multiplex PCR, sequencing and RNA analysis.<h4>Methods</h4>Prospective, observational study. Patients who had been screened for mutations in the RB1 gene were included in the study. Patient details including demographic data; age and sex, laterality, international classification of intraocular retinoblastoma (ICIO ...[more]

PMID: 23960888

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Project description:Retinoblastoma (RB) is an inherited childhood ocular cancer caused by mutations in the tumor suppressor RB1 gene. Identification of RB1 mutations is essential to assess the risk of developing retinoblastoma in the patients´ relatives. Retinoblastoma is a potentially curable cancer and an early diagnosis is critical for survival and eye preservation. Unilateral retinoblastoma is mostly non-heritable and results from two somatic mutations whereas bilateral retinoblastoma is heritable and results from one germline and one somatic mutation, both have high penetrance, 90%. The purpose of this study was to identify causative RB1 mutations in RB patients with different clinical presentations. A comprehensive approach was used to study a cohort of 34 patients with unilateral, bilateral and trilateral retinoblastoma. Blood and tumor DNA was analyzed by sequencing and multiplex ligation-dependent probe amplification (MLPA) assay. Validation of an insertion mutation was performed by cloning the PCR product. Most of the patients in our cohort had unilateral RB, eight patients had bilateral RB and one patient had a trilateral tumor with ocular and suprasellar/sellar locations. Other tumors in addition to retinoblastoma were also found in the affected families. One patient had two syndromes, retinoblastoma and schwannomatosis, and another RB patient had a father with a retinoma. Five out of the 25 unilateral RB patients carried germinal mutations (20%), which were mostly missense mutations. The bilateral and trilateral patients carried splice-site, nonsense and frameshift mutations as well as a whole RB1 gene deletion. Missense mutations were associated with mild phenotype: unilateral retinoblastoma, retinoma or no tumor. In this study we identified causative RB1 mutations in most bilateral RB patients and in some unilateral RB patients, including five novel mutations. These data are crucial for genetic counseling and confirm the need to perform complete genetic screening for RB1 mutations in both constitutional and tumor tissues.

Project description:Purpose:Retinoblastoma (RB) is a retinal tumor that most commonly occurs in children. Approximately 40% of RB patients carry germline mutations in the RB1 gene. RB survivors with germline mutations are at increased risk of passing on the disease to future offspring and of secondary cancer in adulthood. This highlights the importance of genetic testing in disease management and counseling. This study aimed to identify germline RB1 mutations and to correlate the mutations with clinical phenotypes of RB patients. Methods:Genomic DNA was extracted from peripheral blood mononuclear cells isolated from 52 RB patients (27 unilaterally and 25 bilaterally affected probands). Mutations in the RB1 gene, including the promoter and exons 1-27 with flanking intronic sequences, were identified by direct sequencing. The samples with negative test results were subjected to multiplex ligation-dependent probe amplification (MLPA) to detect any gross mutations. A correlation of germline RB1 mutations with tumor laterality or age at diagnosis was determined for RB patients. Age at diagnosis was examined in regard to genetic test results and the presence of extraocular tumor extension. Results:Germline RB1 mutations were detected in 60% (31/52) of patients. RB1 mutations were identified in 92% (22/25) of bilateral RB patients, and a high rate of germline RB1 mutations was found in unilateral RB cases (33% or 9/27). Whole gene and exon deletions were reported in five patients. Twenty-three distinct mutations as a result of base substitutions and small deletions were identified in 26 patients; seven mutations were novel. Nonsense and splicing mutations were commonly identified in RB patients. Furthermore, a synonymous mutation was detected in a patient with familial RB; affected mutation carriers in this family exhibited differences in disease severity. The types of germline RB1 mutations were not associated with age at diagnosis or laterality. In addition, patients with positive and negative test results for germline RB1 mutations were similar in age at diagnosis. The incidence of extraocular tumors was high in patients with heritable RB (83% or 5/6), particularly in unilateral cases (33% or 3/9); the mean age at diagnosis of these patients was not different from that of patients with intraocular tumors. Conclusions:This study provides a data set of an RB1 genotypic spectrum of germline mutations and clinical phenotypes and reports the distribution of disease-associated germline mutations in Thai RB patients who attended our center. Our data and the detection methods could assist in identifying a patient with heritable RB, establishing management plans, and informing proper counseling for patients and their families.

Project description:PurposeRetinoblastoma (RB) is a rare childhood malignant disorder caused by the biallelic inactivation of the RB1 gene. Early diagnosis and identification of carriers of heritable mutations in RB1 can improve disease outcome and management. In this study, we present the spectrum of mutations in the RB1 gene in Vietnamese patients with RB.MethodsTumor RNA from 50 probands with RB, including 12 bilateral and 38 unilateral cases, was extracted. cDNA, after reverse transcription, was sequenced to identify the RNA mutation of the RB1 gene. At the genomic DNA level, mutational analysis of all RB1 exons, exon-intron boundaries, and the promoter region was conducted using PCR and direct sequencing. Multiplex ligation-dependent probe amplification (MLPA) analysis was performed for patients for whom the first two results were negative. For patients for whom either the sequencing or MLPA results were positive for a tumor mutation, patients' and their parents' blood DNA was analyzed to determine the germline mutation.ResultsForty-one different kinds of RB1 tumor mutations were identified in 41 probands (82.0%), including 11 of 12 bilateral cases (91.7%) and 30 of 38 unilateral cases (78.9%). The majority of the detected mutations were nonsense (15 different kinds), followed by frameshift (11 kinds), and splice site mutations (nine kinds). Each splice site mutation was confirmed to create a deletion of the corresponding exon with RNA sequencing. The single promoter mutation c.-197G>A was reported previously; however, both missense mutations identified in exon 6 (c.601G>C: p.A201P) and exon 22 (c.2264T>C: p.F755S) were novel. Gross deletions were detected with MLPA in three probands. The detection rate of germline mutations in bilateral and unilateral cases with mutations were 81.8% and 30.0%, respectively. Only one father out of the 20 parents tested was positive for a germline mutation.ConclusionsMutations in the RB1 gene in Vietnamese patients were heterogeneous and highly prevalent with pathogenic truncated mutations. With advancement in therapeutics, early detection of RB is important for eye salvation.

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RB1 gene mutations in retinoblastoma and its clinical correlation.

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RB1 gene mutations in retinoblastoma and its clinical correlation.

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