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

Delving Into Retinoblastoma Genetics: Discovery of Novel Mutations and Their Clinical Impact: Retrospective Cohort Study

BACKGROUND

Retinoblastoma (Rb) is a rare intraocular malignancy that originates in the retina of children under 5 years of age. Approximately one-third of children diagnosed with retinoblastoma are associated with germline mutations in one of the RB1 alleles. In this study, we aim to identify RB1 mutations in retinoblastoma patients using Sanger sequencing in combination with multiplex ligation-dependent probe amplification (MLPA).

METHOD

The genomic DNA of 167 Rb patients was isolated from peripheral blood and their clinical information was extracted from medical records. The mutations in the RB1 gene were identified through PCR sequencing. Negative results from the PCR sequencing were further analyzed using MLPA reactions.

RESULTS

RB1 mutations were identified in 56 of the 167 (33.5%) patients. The common mutation types were frameshift mutations (n = 19), followed by nonsense (n = 20), splicing (n = 8), missense (n = 5), and whole exon deletion (n = 2). The overall survival rate was 98.2%, with an average follow-up duration of 59 months. Moreover, germline RB1 mutation's correlation with enucleation rates is less pronounced in unilateral cases (12.1%) compared to bilateral cases (65.5%). A total of 13 novel mutations have been identified, of which four are specifically associated with enucleation.

CONCLUSION

This study provides a comprehensive analysis of RB1 germline mutations in a group of cases with Rb, leading to the identification of 13 novel mutations in Rb patients at a referral center in Iran. We expect that our findings will yield valuable insights to inform the management and genetic counseling of Rb patients, as well as their relatives who are at a higher risk.

Strategies to improve diagnosis and access to treatment of retinoblastoma in low- and middle-income countries: A systematic review

Retinoblastoma, the most common intraocular tumor in childhood, still faces challenges in diagnosis and treatment, particularly in low- and middle-income countries. Identifying strategies to improve the time to diagnosis and access to treatment is crucial to enhance survival rates and preserve ocular health. We conducted a systematic review to identify interventions that have demonstrated potential in addressing these challenges. We performed a comprehensive search across databases until March 2023. Out of the studies reviewed, 21 met the inclusion criteria and were categorized into five main areas: surveillance strategies, genetic counseling, education, public assistance, and international partnership. Despite the obstacles faced, the initiatives identified in this review present acts toward improving the time to diagnosis and access to treatment for retinoblastoma. Based on the extracted data, we propose a comprehensive chain of initiatives. We firmly believe that implementing this chain of initiatives can lead to improved clinical outcomes for retinoblastoma patients.

Focused cancer pathway analysis revealed unique therapeutic targets in retinoblastoma

Retinoblastoma (RB) is a pediatric cancer of the eye that occurs in 1/15000 live births worldwide. Albeit RB is initiated by the inactivation of RB1 gene, the disease progression relies largely on transcriptional alterations. Therefore, evaluating gene expression is vital to unveil the therapeutic targets in RB management. In this study, we employed an RT2 Profiler™ PCR array for a focused analysis of 84 cancer-specific genes in RB. An interaction network was built with gene expression data to identify the dysregulated pathways in RB. The key transcript alterations identified in 13 tumors by RT2 Profiler™ PCR array was further validated in 15 tumors by independent RT-qPCR. Out of 84 cancer-specific genes, 68 were dysregulated in RB tumors. Among the 68 genes, 23 were chosen for further analysis based on statistical significance and abundance across multiple tumors. Pathway analysis of altered genes showed the frequent perturbations of cell cycle, angiogenesis and apoptotic pathways in RB. Notably, upregulation of MCM2, MKI67, PGF, WEE1, CDC20 and downregulation of COX5A were found in all the tumors. Western blot confirmed the dysregulation of identified targets at protein levels as well. These alterations were more prominent in invasive RB, correlating with the disease pathogenesis. Our molecular analysis thus identified the potential therapeutic targets for improving retinoblastoma treatment. We also suggest that PCR array can be used as a tool for rapid and cost-effective gene expression analysis.

Impact of RB1 gene screening from blood collected on a single day from 411 family members of 113 Retinoblastoma survivors in India

OBJECTIVES

To analyse the profile and implication of genetic testing in a cohort of retinoblastoma (RB) patients and their families conducted on a single day during World Retinoblastoma Awareness Week 2017.

METHODS

Retrospective analysis of blood samples were collected from 411 subjects, including 113 probands at a camp organised for RB awareness and were analysed for RB1 mutations by Sanger sequencing and Multiplex Ligation-dependent Probe Amplification (MLPA). If germline mutations were detected, the parents and siblings of the proband were tested for the same mutation.

RESULTS

Germline RB1 mutations were identified in 61/113(54%) probands with a mutation detection rate of 96% (47/49) and 22% (14/64) for bilateral and unilateral RB, respectively. Ten novel pathogenic mutations were identified. Splice mutation was most common (31%) followed by nonsense mutation (26%). The mean age at RB diagnosis was significantly lower in patients having germline RB1 mutation (mean 10.7 months ±2.5) compared to those without (mean 27.2 months ±6.5) (p = <0.0001). Parental transmission of the mutant allele was detected in 15/61(25%) cases of which 11(18%) parents were unaffected indicating incomplete penetrance. The origin of the variant allele was both paternal (n = 7) and maternal (n = 4) wherein 5 were bilateral and 6 unilateral.

CONCLUSIONS

The detection of a germline mutation impacts the proband and family members due to its implications on change in prognosis, frequency of subsequent evaluations, screening for ocular and non-ocular cancers, and surveillance of family and future progeny.

Improving visual outcomes in patients with rare paediatric eye diseases

Introduction

Rare paediatric eye diseases (RPEDs) threaten both vision and life. Recently, rare diseases were recognised as a global public health agenda, with children specified as a priority in the World Health Organization's VISION 2020 against avoidable visual loss.

Method

We conducted a review through a query of online databases (PubMed, Embase and Cochrane Library). Articles related to RPEDs were selected based on relevance by 2 authors, with any disagreements adjudicated by the third author.

Results

We synthesise the current state of knowledge regarding RPEDs, barriers to their care, and recommendations for the future. RPEDs often result in significant visual loss, profoundly impacting the way children comprehend and participate in the world. These diseases may also reduce life expectancy and even be life-threatening. Barriers to the care of RPEDs include an unclear definition of "rare diseases", missed or delayed diagnosis, inadequate knowledge and expertise in management, and challenging research environments.

Conclusion

Our findings provide an update on the diagnosis and management of RPEDs, which is of relevance to ophthalmologists, paediatricians, healthcare policymakers and social workers. We propose supportive policies and adequate resource allocation to these diseases, comprehensive and patient-centred care, alongside improved education and training, enhanced research capabilities and continued collaboration across institutions.

Multiplex ligation-dependent probe amplification versus fluorescent in situ hybridization for screening RB1 copy number variations in Egyptian patients with retinoblastoma

BACKGROUND

Retinoblastoma (RB) is the most common primary intraocular malignant tumor in children. RB is mostly caused by biallelic mutations in RB1 and occurs in hereditary and non-hereditary forms according to the "two-hit" theory. RB1 mutations comprise point mutations, indels, large deletions, and duplications. Genetic testing is essential for the comprehensive treatment and management of patients with RB.

AIM

The aim was to evaluate RB1 copy number variations (CNVs) using MLPA versus FISH assays in group of Egyptian patients with RB.

RESULTS

16.67% showed an RB1 deletion, abnormal methylation status, or both.

CONCLUSION

Our results suggested MLPA is a fast, reliable, and powerful method and should be used as a first-line screening tool for detecting RB1 CNVs in patients with RB. Moreover, MLPA is advantageous as it evaluates the methylation status/inactivation of RB1, not possible by FISH.

Identification of novel genes by targeted exome sequencing in Retinoblastoma

BACKGROUND

Retinoblastoma (RB) is initiated by mutation in both alleles of RB1 gene. However, few cases may occur even in the absence of RB1 mutation suggesting the role of genes other than RB1.

METHODOLOGY

The current study was planned to utilize targeted exome sequencing in Indian RB patients affected with unilateral non-familial RB. 75 unilateral RB patients below 5 years of age were enrolled. Genomic DNA was extracted from blood and tumor tissue. From peripheral blood DNA, all coding and exon/intron regions were amplified using PCR and direct sequencing. Cases which did not harbor pathogenic variants in peripheral blood DNA were further screened for mutations in their tumor tissue DNA using targeted exome sequencing. Three pathogenicity prediction tools (Mutation Taster, SIFT, and PolyPhen-2) were used to determine the pathogenicity of non-synonymous variations. An in-house bioinformatics pipeline was devised for the mutation screening by targeted exome sequencing. Protein modeling studies were also done to predict the effect of the mutations on the protein structure and function.

RESULTS

Using the mentioned approach, we found two novel variants (g.69673_69674insT and g.48373314C>A) in RB1 gene in peripheral blood DNA. We also found novel variants in eight genes (RB1, ACAD11, GPR151, KCNA1, OTOR, SOX30, ARL11, and MYCT1) that may be associated with RB pathogenesis.

CONCLUSION

The present study expands our current knowledge regarding the genomic landscape of RB and also highlights the importance of NGS technologies to detect genes and novel variants that may play an important role in cancer initiation, progression, and prognosis.

Germline RB1 Mutation in Retinoblastoma Patients: Detection Methods and Implication in Tumor Focality

Purpose

The study aimed to generate a stepwise method to reduce the workload of full-scale RB1 sequencing for germline mutation screening in retinoblastoma (RB) patients. The implication of germline mutation in tumor focality was also determined in this study.

Methods

A stepwise method was created on the basis of "hotspot" exons analyzed using data on germline RB1 mutation in the RB1-Leiden Open Variation Database and then tested for mutation screening in the blood DNA of 42 patients with RB. The method was compared with the clinical next-generation sequencing (NGS) panel in terms of sequencing outcomes. The germline RB1 mutation was examined in association with multifocality in RB.

Results

Germline RB1 mutation was identified in 61% of all bilateral cases in the first step of the 3 stepwise method and in 78% and 89% for the two and three steps combined, respectively. NGS detected a mosaic variant of RB1 that was not detected by the first two steps and increased the sensitivity from 78% to 83%. Analysis of the relationship between mutation status and tumor focality indicated that multifocality in RB was dependent on germline RB1 mutation, confirming a higher tendency to have a germline RB1 mutation in patients with multifocal RB.

Conclusions

A 3 stepwise method reduces the workload needed for sequencing of the RB1 for bilateral cases. NGS outweighs conventional sequencing in terms of the identification of germline mosaic variants. Multifocal tumors in RB may be used to presume germline mutation.

Translational Relevance

The presence of "hotspot" exons of germline RB1 mutation in bilateral cases facilitates a mutation screening. However, when genetic testing is not available, multifocality in RB regardless of tumor laterality is predictive of germline RB1 mutation.

Identification of novel RB1 genetic variants in Retinoblastoma patients and their impact on clinical outcome

BACKGROUND

Retinoblastoma (RB) is an intraocular childhood cancer develops due to inactivation of RB1 gene. Identification of RB1 genetic variants, correlating and confirming genetic test results with clinical outcomes are crucial for effective RB management.

METHODS

Retrospective study of 62 RB patients and 14 family members who underwent genetic testing either by next generation sequencing (NGS) or multiplex ligation-dependent probe amplification (MLPA) or by both for screening RB1 germline mutations present in peripheral blood. Mutational outcomes were correlated with clinical outcomes evaluated over a follow-up period of 12 months.

RESULTS

Of the 62 patients, 35 (56%) had bilateral RB and 27 (44%) had unilateral RB. Out of 24 (52%) variants detected by NGS, 9 (37.5%) were novel and 15 (62.5%) were known in 46 probands. Six (18%) gross deletions were detected by MLPA in 34 probands. The mutation detection rate by NGS and MLPA in unilateral cases was 15% (n = 4) and 74% (n = 26) in bilateral cases. In patients with RB1 genetic mutations versus those without, the rate of primary enucleation (7 (12%) vs 18 (44%) eyes; p = .0008) was inversely proportional to tumor recurrence (25 (45%) vs 6 (15%) eyes; p = .002). There was no difference in the rate of globe salvage and metastasis, over a mean follow-up period of 12 months.

CONCLUSION

The mutations screening is important for risk assessment in future siblings and offspring of RB patients and most important in unilateral RB for determining if hereditary or not hereditary RB. Its role in predicting clinical outcomes is yet to be determined.

Retinoblastoma genetics screening and clinical management

BACKGROUND

India accounts for 20% of the global retinoblastoma (RB) burden. However, the existing data on RB1 gene germline mutations and its influence on clinical decisions is minimally explored.

METHODS

Fifty children with RB underwent complete clinical examination and appropriate multidisciplinary management. Screening of germline RB1 gene mutations was performed through next-generation sequencing and Multiplex Ligation-dependent Probe Amplification (MLPA) analysis. The mutation and non-mutation groups were compared for clinical parameters especially severity, progression and recurrence.

RESULTS

Twenty-nine patients had bilateral RB (BLRB) and 21 had unilateral RB (ULRB). The genetic analysis revealed 20 RB1 variations in 29 probands, inclusive of 3 novel mutations, known 16 mutations and heterozygous whole gene deletions. The mutation detection rate (MDR) was 86.2% in BLRB and 19% in ULRB. Associations of disease recurrence (p = 0.021), progression (p = 0.000) and higher percentage of optic nerve invasion, subretinal seeds and high-risk pathological factors were observed in the mutation group. Clinical management was influenced by the presence of germline mutations, particularly while deciding on enucleation, frequency of periodic follow up and radiotherapy.

CONCLUSIONS

We identified novel RB1 mutations, and our mutation detection rate was on par with the previous global studies. In our study, genetic results influenced clinical management and we suggest that it should be an essential and integral component of RB-care in India and elsewhere.

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

Clinical evaluation of the genetic testing strategy is essential for ensuring the correct determination of mutation carriers. The current study retrospectively analyzed genetic and clinicopathological data from 62 Vietnamese patients with retinoblastoma (RB) referred to the Vinmec Hi-Tech Center for RB transcriptional corepressor 1 (RB1) genetic testing between 2017 and 2019. The present study aimed to evaluate the sensitivity of the Next Generation Sequencing (NGS) method to identify novel RB1 mutations, and to consider using age at diagnosis as a risk factor. Genomic DNA was analyzed with custom panel based targeted NGS. NGS was performed on the Beijing Genomics Institute (BGI) sequencing platform, and pathogenic or likely pathogenic variants were confirmed by Sanger sequencing, quantitative PCR (qPCR) or Multiplex Ligation-dependent Probe Amplification assay (MLPA). Constitutional RB1 variants were identified in 100% (25/25) of the bilateral cases, while several common previously reported RB1 mutations were also recorded. In addition, in Vietnamese patients with RB, nine novel RB1 mutations were identified. Children aged between 0-36 months were more likely to be RB1 carriers compared with those aged >36 months. The current findings indicated that the NGS method implemented in the Vinmec Hi-Tech Center was highly accurate, and age at diagnosis may be used to assess the risk of hereditary RB. Furthermore, the newly identified RB1 mutations may provide additional data to improve the current understanding of the mechanisms underlying RB1 inactivation and the development of rapid assays for detecting RB1 mutations. Overall, the present study suggested that NGS may be applied for detecting germline RB1 mutations in routine clinical practice.

Cancer Stem Cells with Overexpression of Neuronal Markers Enhance Chemoresistance and Invasion in Retinoblastoma

BACKGROUND

Retinoblastoma is a sight and life-threatening embryonal tumor in children. Though chemotherapy is the main mode of therapy, evolving resistance remains a major obstacle in treatment success. The presence of cancer stem cells (CSC) is frequently reported to be responsible for chemoresistance in multiple tumors.

OBJECTIVE

Our study aims to identify the molecular factors that facilitate the chemoresistance through cancer stem cells in retinoblastoma.

METHODS

We developed etoposide and carboplatin resistant retinoblastoma (Y79) cell lines by stepwise drug increment treatment, validated with MTT and TUNEL assays. Colony forming and invasive ability were studied by soft-agar colony forming and transwell assays, respectively. Similar analysis in non-responsive retinoblastoma tumors were carried out by histopathology. Finally, expression of CSC/neuronal markers and ABC transporters were examined by quantitative PCR and protein expression of neuronal stem cell markers was confirmed by Western blot.

RESULTS

Larger colony size of resistant cells in soft-agar assay provided evidence for increased selfrenewability. Histopathology in non-responsive tumors showed poorly differentiated cells predominantly. Besides, both resistant cell lines and non-responsive tumors showed increased invasion with higher expression of neuronal stem cell markers - SOX2, NANOG, OCT4 and ABC transporters - ABCB1 and ABCC3. Increased self-renewal ability and invasion along with overexpression of stemness markers in resistant cells and tumors provide evidence for stemness driving chemoresistance and invasion in retinoblastoma.

CONCLUSION

We have demonstrated Neuronal stem cell/CSC markers that facilitate the maintenance of cancer stem cells. Developing therapies targeting these factors will help in overcoming resistance and improving retinoblastoma treatment.

Retinoblastoma discordance in families with twins

Retinoblastoma has an increased inheritance risk of germline RB1 mutations in offspring and siblings, especially twins. Three families, each having one retinoblastoma-affected twin, were selected for genetic analysis and DNA profiling. Germline RB1 mutations were found in all probands. DNA profiling carried on similar-looking twins of families I and II, proved them to be fraternal. This study demonstrates the importance of genetic analysis of RB1 gene for risk prediction in retinoblastoma families. It also emphasizes that DNA profiling is a mandate for genetic screening of families with twins, thus adding a new dimension in counseling of retinoblastoma.

Knudson's hypothesis revisited in Indian retinoblastoma patients

AIM

Retinoblastoma (RB) is the most common primary intraocular malignancy affecting children under 5 years of age. This study aims to correlate the clinical parameters with RB1 mutation in the light of Knudson's two-hit hypothesis in Indian RB patients.

METHODS

We analyzed the clinical details of 73 RB patients visiting Aravind Eye Hospital, Madurai, India, between January and October 2012. Data on gender, presenting age and sign, laterality, number of tumors in each eye and family history were collected. A semi log plot was derived based on Knudson's two-hit hypothesis. Genetic analysis of RB1 was carried out to identify the two hits.

RESULTS

The mean age at diagnosis for unilateral and bilateral cases was 24.0 ± 15.1 and 9.8 ± 11.5 months, respectively. Familial RB was seen in 13 (17.8%) patients of whom 11 were bilateral. Multiple tumors were observed more frequently in bilateral than in unilateral cases. All unilateral and bilateral patients followed the two-hit and one-hit curves, respectively, confirming Knudson's hypothesis in Indian patients. Genetic analysis identified two somatic mutations in tumor samples of sporadic unilateral cases. Among the two bilateral patients, one received the first hit from her father and the other patient developed a de novo germline mutation during early development.

CONCLUSION

The two-hit hypothesis has been reestablished in Indian patients. Genetic analysis of tumor samples has also complemented the statistical analysis to reaffirm the two hits in tumor development.