A stepwise strategy for rapid and cost-effective RB1 screening in Indian retinoblastoma patients

Abstract

India has the highest number of retinoblastoma (RB) patients among the developing countries owing to its increasing population. Of the patients with RB, about 40% have the heritable form of the disease, making genetic analysis of the RB1 gene an integral part of disease management. However, given the large size of the RB1 gene with its widely dispersed exons and no reported hotspots, genetic testing can be cumbersome. To overcome this problem, we have developed a rapid screening strategy by prioritizing the order of exons to be analyzed, based on the frequency of nonsense mutations, deletions and duplications reported in the RB1-Leiden Open Variation Database and published literature on Indian patients. Using this strategy for genetic analysis, mutations were identified in 76% of patients in half the actual time and one third of the cost. This reduction in time and cost will allow for better risk prediction for siblings and offspring, thereby facilitating genetic counseling for families, especially in developing countries.

Knudson's hypothesis revisited in Indian retinoblastoma patients

“…Two somatic mutations were identified in tumor samples of each patient 35 and 47. In addition, we have carried out the genetic analysis of 50 patients and the results were very much consistent with Knudson's two‐hit hypothesis …”

“…After the first hit has occurred, the second hit can be due to loss of heterozygosity (LoH), promoter methylation or a second mutation in another allele . Among them, LoH had been the most common second hit and our case series involving more than 50 patients also had more LoH …”

Clinical evaluation of RB1 genetic testing reveals novel mutations in Vietnamese patients with retinoblastoma

“…In addition, Multiplex Ligation-dependent Probe Amplification (MLPA), quantitative PCR (qPCR) or array Comparative Genomic Hybridization (aCGH) can identify large RB1 rearrangements. The combination of the aforementioned methods is essential for detecting all possible RB1 mutations (17)(18)(19). Recently, Next Generation Sequencing (NGS) has been implemented as rapid and effective strategy for identification of RB1 mutations since all variations can be detected in a single test, thus providing a number of advantages, including high sensitivity and cost-effectiveness (20)(21)(22)(23)(24)(25).…”

Retinoblastoma discordance in families with twins

“…Family III had a positive family history of RB. Mutational screening was done with blood DNA in sequential manner as described[5] based on the calculated frequency of mutations in RB1 gene.…”