Chromosomal abnormalities study for anembryonic pregnancy by BACs-on-Beads technique.

OBJECTIVE: This study evaluated the BACs-on-Beads™ (BoBs) efficiency assay in detecting chromosomal anomalies in products of conception (POC) specimens associated with anembryonic pregnancy (AP) among Thai pregnant women. METHOD: Retrospective analysis applied the BoBs™ assay to examine AP samples from 2010 to 2022. The incidences of AP with chromosomal abnormalities were reported. RESULT: Assessment of villi from anembryonic pregnancy samples found normal chromosome complement in 50% of the cases, while the remainder showed chromosomal abnormalities. Trisomy 16 was found in 15% of the cases and trisomies 22, 15, and 19 in 9.6%, 3.8%, and 3.8%, respectively. Advanced maternal age was associated with a higher incidence of aneuploidy. CONCLUSION: The BoBs™ assay effectively detected diverse chromosomal abnormalities in villi samples from POC. The diagnostic utility of the BoBs™ assay was highlighted in identifying chromosomal irregularities in AP cases. Trisomy 16 possessed the most chromosomal abnormalities in the AP samples.

Therapeutic potential of third-generation chimeric antigen receptor T cells targeting B cell maturation antigen for treating multiple myeloma.

Multiple myeloma (MM) is an incurable hematologic malignancy characterized by the rapid proliferation of malignant plasma cells within the bone marrow. Standard therapies often fail due to patient resistance. The US FDA has approved second-generation chimeric antigen receptor (CAR) T cells targeting B-cell maturation antigen (anti-BCMA-CAR2 T cells) for MM treatment. However, achieving enduring clinical responses remains a challenge in CAR T cell therapy. This study developed third-generation T cells with an anti-BCMA CAR (anti-BCMA-CAR3). The CAR incorporated a fully human scFv specific to BCMA, linked to the CD8 hinge region. The design included the CD28 transmembrane domain, two co-stimulatory domains (CD28 and 4-1BB), and the CD3ζ signaling domain (28BBζ). Lentiviral technology generated these modified T cells, which were compared against anti-BCMA-CAR2 T cells for efficacy against cancer. Anti-BCMA-CAR3 T cells exhibited significantly higher cytotoxic activity against BCMA-expressing cells (KMS-12-PE and NCI-H929) compared to anti-BCMA-CAR2 T cells. At an effector-to-target ratio of 10:1, anti-BCMA-CAR3 T cells induced lysis in 75.5 ± 3.8% of NCI-H929 cells, whereas anti-BCMA-CAR2 T cells achieved 56.7 ± 3.4% (p = 0.0023). Notably, after twelve days of cultivation, anti-BCMA-CAR3 T cells nearly eradicated BCMA-positive cells (4.1 ± 2.1%), while anti-BCMA-CAR2 T cells allowed 36.8 ± 20.1% to survive. This study highlights the superior efficacy of anti-BCMA-CAR3 T cells against both low and high BCMA-expressing MM cells, surpassing anti-BCMA-CAR2 T cells. These findings suggest potential for advancing anti-BCMA-CAR3 T cells in chimeric antigen receptor T (CAR-T) therapy for relapsed/refractory MM.

Genotyping of the rare Para-Bombay blood group in southern Thailand

ABSTRACT Introduction: The para-Bombay phenotype, or H-deficient secretor, results from different mutations of the FUT1, with or without the FUT2 mutation. Consequently, there is an absent or weak expression of the H antigen on red blood cells (RBCs). Routine ABO blood grouping for two siblings with blood group O showed discrepant results with their parental blood group AB. Fragments encompassing the entire coding region of the FUT1 and FUT2 genes were investigated. Methods: Blood and saliva specimens were collected to verify the correct ABO grouping by cell grouping, serum grouping and the hemagglutination inhibition (HI) test, respectively. The FUT1 and FUT2 genomes were identified using the whole-exome sequencing (WES) in two children's DNA blood specimens and may have caused, or been relative to, their blood group. Genetic variations of the FUT1 and FUT2 genes have been investigated in the other family members using the Sanger sequencing. Results: The serologic reaction results of the proband revealed that A, B and H antigens were absent on RBCs, and that the serum contained anti-H. However, ABH and AH antigens were present in the saliva PB1 and PB2, respectively. The probands PB1 and PB2 were assigned as AB and A blood groups, respectively. Blood genotyping confirmed that heterozygous mutations of the FUT1 gene, c.551_552delAG, were identified. Three family members, PB3, PB, and PB8, also showed normal ABO blood groups, but their genotypes were also the FUT1 mutation c.551_552delAG. Conclusions: The FUT1 mutation c.551_552delAG may result in the reduced or absent H antigen production on RBCs, which characterizes the para-Bombay phenotypes. Blood genotyping is essential if these individuals need a blood transfusion or are planning to donate blood.

Upregulation of miR-20a-5p as the Potential MicroRNA Marker in Red Blood Cell Storage Lesion.

Background: Packed red blood cells (PRBCs) can be preserved for 42 days, and stored PRBCs have slow, dangerous changes over time during storage. miRNA is approximately 22 nucleotides long, a small single-stranded noncoding RNA molecule. miRNA guides by pairing bases with their downstream target mRNA to regulate negative expression. They are essential in many life processes, including cell differentiation, proliferation, and apoptosis. Therefore, miRNA alterations may represent possible biomarkers of PRBC storage lesions. This study is aimed at validating the miR-20a-5p in PRBC storage. Study Design and Methods. A total of 20 PRBC samples were divided into day 1 and day 20 storage groups. Total miRNA was extracted and quantified by probe-based RT-qPCR assays to explore the potential role of miRNAs in PRBC storage lesions. Results: Upregulated miR-20a-5p in PRBC storage on day 20 compared to day 1. MiR-20a-5p promoted cell survival, which may affect the downstream regulation and decrease PRBC viability in prolonged storage. Conclusion: On this basis, this detection may help to assess the quality of stored PRBCs.

Genotyping of the rare Para-Bombay blood group in southern Thailand.

INTRODUCTION: The para-Bombay phenotype, or H-deficient secretor, results from different mutations of the FUT1, with or without the FUT2 mutation. Consequently, there is an absent or weak expression of the H antigen on red blood cells (RBCs). Routine ABO blood grouping for two siblings with blood group O showed discrepant results with their parental blood group AB. Fragments encompassing the entire coding region of the FUT1 and FUT2 genes were investigated. METHODS: Blood and saliva specimens were collected to verify the correct ABO grouping by cell grouping, serum grouping and the hemagglutination inhibition (HI) test, respectively. The FUT1 and FUT2 genomes were identified using the whole-exome sequencing (WES) in two children's DNA blood specimens and may have caused, or been relative to, their blood group. Genetic variations of the FUT1 and FUT2 genes have been investigated in the other family members using the Sanger sequencing. RESULTS: The serologic reaction results of the proband revealed that A, B and H antigens were absent on RBCs, and that the serum contained anti-H. However, ABH and AH antigens were present in the saliva PB1 and PB2, respectively. The probands PB1 and PB2 were assigned as AB and A blood groups, respectively. Blood genotyping confirmed that heterozygous mutations of the FUT1 gene, c.551_552delAG, were identified. Three family members, PB3, PB, and PB8, also showed normal ABO blood groups, but their genotypes were also the FUT1 mutation c.551_552delAG. CONCLUSIONS: The FUT1 mutation c.551_552delAG may result in the reduced or absent H antigen production on RBCs, which characterizes the para-Bombay phenotypes. Blood genotyping is essential if these individuals need a blood transfusion or are planning to donate blood.

The Utilization of MS-MLPA as the First-Line Test for the Diagnosis of Prader-Willi Syndrome in Thai Patients.

Prader-Willi syndrome (PWS) is a genetic disorder caused by the expression disruption of genes on the paternally inherited allele of chromosome 15q11.2-q13. Apart from clinical diagnostic criteria, PWS is confirmed by genetic testing. Methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) is one of the molecular techniques used to analyze this syndrome. This study aimed to evaluate the concordance of the test results of MS-MLPA with conventional techniques in the diagnosis of PWS in Thai patients. Forty leftover specimens from routine genetic testing (MS-PCR and FISH) were tested to obtain MS-MLPA results. By comparison, perfect concordance was shown between the result of MS-MLPA and those of conventional techniques. In conclusion, MS-MLPA is an accurate and cost-effective assay that can be used to confirm PWS diagnosis with explicit deletion of affected genes.

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.

Genomic findings of hypertrophic and dilated cardiomyopathy characterized in a Thai clinical genetics service.

Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are the most common referrals in the Inherited Cardiovascular Condition (ICC) Genetics Service. Several issues must be discussed with patients and their families during the genetic consultation session, including the options for genetic testing and cardiovascular surveillance in family members. We developed an ICC registry and performed next-generation-based DNA sequencing for all patients affected by non-syndromic HCM and idiopathic DCM in our joint specialist genetics service. The target gene sequencing panel relied on the Human Phenotype Ontology with 237 genes for HCM (HP:0001639) and 142 genes for DCM (HP:0001644). All subjects were asked to contact their asymptomatic first-degree relatives for genetic counseling regarding their risks and to initiate cardiovascular surveillance and cascade genetic testing. The study was performed from January 1, 2014, to December 31, 2020, and a total of 62 subjects (31-HCM and 31-DCM) were enrolled. The molecular detection frequency was 48.39% (32.26% pathogenic/likely pathogenic, 16.13% variant of uncertain significance or VUS for HCM, and 25.81% (16.13% pathogenic/likely pathogenic, 9.68% VUS) for DCM. The most prevalent gene associated with HCM was MYBPC3. The others identified in this study included ACTN2, MYL2, MYH7, TNNI3, TPM1, and VCL. Among the DCM subjects, variants were detected in two cases with the TTN nonsense variants, while the others were missense and identified in MYH7, DRSP3, MYBPC3, and SCN5A. Following the echocardiogram surveillance and cascade genetic testing in the asymptomatic first-degree relatives, the detection rate of new cases was 8.82% and 6.25% in relatives of HCM and DCM subjects, respectively. Additionally, a new pre-symptomatic relative belonging to an HCM family was identified, although the genomic finding in the affected case was absent. Thus, ICC service is promising for the national healthcare system, aiming to prevent morbidity and mortality in asymptomatic family members.

Extracellular Vesicle-Based Method for Detecting MYCN Amplification Status of Pediatric Neuroblastoma.

MYCN amplification is the strongest predictor of high-risk neuroblastoma (NB). The standard procedure to detect MYCN status requires invasive procedures. Extracellular vesicles (EVs) contain molecular signatures of originated cells, present in biofluids, and serve as an invaluable source for cancer liquid biopsies. This study aimed to establish an EV-based method to detect the MYCN status of NB. Two EV subtypes, i.e., microvesicles (MVs) and exosomes, were sequentially isolated from the culture supernatant by step-wise centrifugation, ultrafiltration, and size-exclusion chromatography. Quantitative RT-PCR was performed to detect MYCN mRNA. As a result, MYCN mRNA was detectable in the MVs, but not exosomes, of MYCN-amplified NB cells. MYCN mRNA-containing MVs (MYCN-MV) were successfully detected in three distinct MYCN-amplified NB cell lines but absent in three MYCN non-amplification cells. The simulated samples were prepared by pulsing MVs into human serum. MYCN-MV detection in the simulated samples showed a less interfering effect from the human blood matrix. Validation using clinical specimens (2 mL bone marrow plasma) obtained from patients at various disease stages showed a promising result. Five out of six specimens of MYCN-amplified patients showed positive results, while there were no false positives in four plasma samples of the MYCN non-amplification group. This study communicated a novel EV-based method for detecting the MYCN status of pediatric NB based on MYCN mRNA contents in MVs. Future studies should be pursued in a prospective cohort to determine its true diagnostic performance.

Clinical Features to Predict 22q11.2 Deletion Syndrome Proven by Molecular Genetic Testing.

The 22q11.2 deletion syndrome (22q11.2 DS) is the most common microdeletion syndrome with a wide variety of clinical features. However, as there are no clinical criteria for diagnosis, confirmation is solely done by genetic tests if clinicians recognize the syndrome. Therefore, we aimed to identify clinical features that may help clinicians recognize 22q11.2 DS. Participants with at least two anomalies were enrolled, complete patient history and physical examinations were performed, then multiplex ligation-dependent probe amplification (MLPA) analysis for 22q11.2 DS was utilized. We identified 11/48 (23%) cases with 22q11.2 DS. Palatal anomalies, hypocalcemia, and ≥3 affected body systems were highly significant presentations in the 22q11.2 DS group versus the group without deletion ( p < 0.05). Therefore, a comprehensive physical examination is crucial at identifying any subtle features which may lead to testing and a definite diagnosis.

Cardiac rhabdomyoma as a possible new prenatal sonographic feature of Prader-Willi syndrome.

We describe a unique case of a pregnancy with fetal Prader-Willi syndrome (PWS). A 40-year-old pregnant woman prenatally presented with polyhydramnios, decreased fetal movements, fetal growth restriction with normal Doppler study, and fetal cardiac rhabdomyoma, a possible new sonographic markers for PWS, at 31 weeks of gestation. The newborn had hypotonia and feeding difficulty. Molecular genetic study showed a normal copy number of the 15q11.2-q13.1 chromosomal region but hypermethylation pattern of this region, indicating PWS. Other than the combination of polyhydramnios, fetal growth restriction, and decreased fetal movements, cardiac rhabdomyoma was detected and possibly associated with PWS. In conclusion, PWS should be listed in differential diagnoses if fetuses having the following perinatal factors: polyhydramnios, decreased fetal movements, and growth restriction. Finally, cardiac rhabdomyoma, observed in this case, might possibly be associated with PWS, although further studies to confirm are needed.

Incidence and Types of Fetal Chromosomal Abnormalities in First Trimester of Thai Pregnant Women between Miscarriages and Intrauterine Survivals.

Abortion is a common pregnancy complication. Fetuses with several types of chromosomal abnormalities are aborted during the first trimester, while others have a better chance of surviving. This research aims to study and compare the incidence and types of fetal chromosomal abnormalities during the first trimester of Thai pregnant women between miscarriages and intrauterine survivals. Cytogenetic and BACs-on-Beads™ assays were assessed from 2010 to 2020 in Ramathibodi Hospital using first trimester samples of 265 chorionic villi as a retrospective study. Chromosomal abnormalities were observed in 135 cases (50.94%) including 38.11% miscarriages and 12.83% intrauterine survivals. In total, 75.56% single autosomal trisomies, 18.52% sex chromosome aneuploidies, 5.19% double aneuploidies, and 0.74% structural abnormalities were detected. In miscarriages, all chromosomes were involved in abnormalities except chromosomes 1, 5, 8, 9, 11, and 17, while survivals had only trisomy 13, 18, 21, and sex chromosome aneuploidy. Trisomy 16 and 18 were the most common abnormalities in miscarriages and intrauterine survivals, respectively. The highest rate of chromosomal aberrations was demonstrated in 8-9+6 and 12-13+6 weeks of gestation in miscarriages and intrauterine survivals, respectively. Correlation between chromosomal abnormalities and maternal age <35 years and ≥35 years was significant (p < 0.05) in intrauterine survival and first trimester groups.

Targeting UCHL1 Induces Cell Cycle Arrest in High-Risk Multiple Myeloma with t(4;14).

Multiple myeloma (MM) patients considered to be at high cytogenetic risk commonly fail to respond to standard treatment. A thorough understanding of the molecular mechanism of MM development is, therefore, needed. We endeavored to explore the transcriptional signature among different subgroups of newly diagnosed MM using gene chip-based expression microarray. Bone marrow samples of 15 newly diagnosed Thai MM patients were included. The chromosomal translocation t(4;14) was the most frequently identified genetic alteration in the high-risk subgroup. Cluster analysis from expression profiling demonstrated that high-risk MM have a distinctly different expression pattern compared to standard-risk patients. The most significant differentially expressed gene was UCHL1. Functional enrichment analysis by Gene Set Enrichment Analysis, FUNRICH, and Gene Ontology Panther pathway revealed the gene sets involved in cell cycle control to be enriched in the t(4;14) high-risk group. Interestingly, among the well-established downstream targets of UCHL1, only CCND2 was significantly expressed in the t(4;14) high-risk group. Suppression of UCHL1 protein level by LDN-5744 inhibitor could arrest the cell cycle in G1 phase in cell lines. These findings shed light on the molecular mechanism of UCHL1 in t(4;14) high-risk MM and support the evidence that alteration of the UCHL1 pathway may play a role in the pathogenesis of high-risk MM.

High Expression of miR-483-5p Predicts Chemotherapy Resistance in Epithelial Ovarian Cancer.

BACKGROUND: Ovarian cancer is the most deadly cancer that requires novel diagnostics and therapeutics. MicroRNAs are viewed as essential gene regulatory elements involved in different pathobiological mechanisms of many cancers, including ovarian cancer. OBJECTIVE: This study examined the relationship between microRNA (miRNA) expression and response to platinum-based chemotherapy. METHODS: Genome-wide miRNA expression analysis was conducted using Epithelial Ovarian Cancer (EOC) tissues from 25 patients with 17 malignant tumors and eight benign ovarian tumors. Candidate miRNAs that respond to platinum-based chemotherapy were selected for validation by quantitative RT-PCR. RESULTS: Among 2,578 mature human miRNAs, high expression of miR-483-5p correlated with poor responses to platinum-based chemotherapy in EOC patients. Furthermore, high levels of miR-483-5p in the resistant group suppressed expression of the apoptotic regulator TAOK-1. CONCLUSION: A possible marker for the prediction of chemotherapy response and resistance in patients may be miR-483-5p. Choosing the right treatment for each patient with EOC can avoid the risk of developing chemotherapy resistance.

Klinefelter Syndrome Mosaicism 46,XX/47,XXY: A New Case and Literature Review.

Most cases of Klinefelter syndrome (KS) have 47,XXY karyotype. We reported the first case of 46,XX/47,XXY KS whose genital ambiguity was detected prenatally with postnatal confirmation of the mosaicism and ovotesticular disorder of sex development (OT-DSD). The paternal origin of the extra X chromosome was identified using trio cytogenomic single-nucleotide polymorphism array. Additional 18 cases were also reviewed. The clinical presentation of 46,XX/47,XXY is age-dependent with two age peaks, including ambiguous genitalia during infancy and gynecomastia with or without cyclical hematuria and left scrotal pain and mass in adolescence. The 46,XX is the predominant karyotype both in peripheral blood and gonadal tissue. The risk of germ cell tumor is very high throughout life in these individuals. Individuals with 46,XX/47,XXY mosaicism should be treated more as OT-DSD other than a simple mosaic KS. A multidisciplinary approach and long-term monitoring are necessary.

MicroRNA Expression Profiling of Epithelial Ovarian Cancer Identifies New Markers of Tumor Subtype.

BACKGROUND: Epithelial Ovarian Cancer (EOC) is often challenging to diagnose, even though histological examination. MicroRNA (miRNA or miRNA) is bound to the target messenger RNA (mRNA) due to which the mRNA molecules are silenced. The identification of miRNA expression- based EOC subtypes is considered a critical means of prognostication. So far, the studies on EOC subtypes have not been well characterized. OBJECTIVE: This study aimed to confirm the existence of miRNAs in EOC and to assess their potential as clinical biomarkers for EOC. METHODS: We sampled 25 ovarian tumor tissues from patients with human ovarian tumors (17 malignant; 12 serous EOC, five non-serous EOC, and eight benign ovarian tumors). miRNA microarray detection was performed to identify EOC miRNAs. Real-time PCR was adapted for the validation of differentially expressed miRNAs detected by microarray analysis related to hybridization intensity. RESULTS: The results confirmed that miRNAs exist in EOC, relative expression of EOC miRNAs demonstrated that the upregulation of miR-483-5p, and downregulation of miR-127-3p, and miR- 532-5p were significantly expressed in the malignant group than in the benign group at p < 0.05. Besides, miR-483-5p could also distinguish EOC subtypes between serous EOC and non-serous EOC, with a p < 0.05. CONCLUSION: A comprehensive miRNA expression profiling can help to refine subtype classification in EOC, opening new opportunities for identifying clinically applicable markers for improved stratification and diagnostics of ovarian tumors.

Performance of the MLPA technique for detecting common mutations in Leber hereditary optic neuropathy.

Leber hereditary optic neuropathy (LHON) causes painless vision loss resulting from mitochondrial DNA (mtDNA) mutation. Over 95% of LHON cases result from one of three mtDNA point mutations (m.3460G>A, m.11778G>A, and m.14484T>C). There is no established cure for LHON; early and accurate diagnosis would enable patients to be given appropriate treatments leading to a reduction of the disease progression. To increase the accessibility to molecular genetic testing for LHON, an accurate and cost-effective technique is required. The purpose of this study was to evaluate the accuracy of multiplex ligation-dependent probe amplification (MLPA) for detecting the three common mutations in 18 LHON blood specimens. Validation of the results using direct DNA sequencing technology proved that the MLPA technique had 100% accuracy, with no false-positive results. This study demonstrates that MLPA could provide a highly accurate, economical, and widely accessible technique for routine molecular genetic testing for mitochondrial disorders.

The Frequency of SF3B1 Mutations in Thai Patients with Myelodysplastic Syndrome

Genetic mutations in genes encoding critical component of RNA splicing machinery including SF3B1 are frequently identified and recognized as the pathogenesis in the development of myelodysplatic syndrome (MDS). In this study, PCR sequencings specific for SF3B1 exon 13, 14, 15, and 16 were performed to analyse genomic DNA isolated from bone marrow samples of 72 newly diagnosed MDS patients. We found that 10 of 72 (14%) patients harbor SF3B1 missense mutations including E622D (1/72), R625C/G (2/72), H662Q (1/72), K666T (1/72), K700E (4/72) and G740E (1/72), respectively. Mutations were predominantly located on exon 14 and 15 of SF3B1 coding sequence. Interestingly, patients with SF3B1 mutations exhibited higher platelet counts (195×109/L VS. 140×109/L, p-value = 0.025) as well as lower hemoglobin levels (81 g/L VS. 92 g/L, p-value = 0.009) and associated with ring sideroblast phenotype (p-value < 0.001) when compared with patients without the SF3B1 mutation. In summary, we reported the frequency of SF3B1 mutations in Thai patients with different subtypes of MDS. SF3B1 mutations were predominantly occurred in MDS-RS and considered as favourable prognosis value. This study further highlighted the clinical important of SF3B1 mutations analysis for the classification of MDS.

EGFL7 and RASSF1 promoter hypermethylation in epithelial ovarian cancer.

DNA methylation is one of the epigenetic mechanisms associated with gene expression and plays a key role as in activation and deactivation of oncogenes and tumor suppressor genes, respectively. This study employed DNA methylation array to identify methylated genes which are highly correlated with various phenotypes of epithelial ovarian cancer (EOC) in Thai patients and to quantify promoter CpG-island methylation of candidate genes. Tissues from patients with serous and non-serous EOC showed significantly higher promoter methylation of EGFL7 and RASSF1 compared to benign cases. These results indicate the potential of investigating promoter CpG-island methylation of cancer-associated genes as biomarkers of disease progression and even possibly of early detection.

Spectrum of germline RB1 mutations and clinical manifestations in retinoblastoma patients from Thailand.

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.