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.

Establishment and genomic characterization of a novel retinoblastoma cell line without RB1 mutationderived from a Han Chinese donor / 上海交通大学学报（医学版）

Objective: To develop and characterize a novel retinoblastoma cell line from a Han Chinese patient. Methods: Cells were dispersed from tumor tissue harvested from an enucleated eyeball harbouring retinoblastoma under sterile conditions. The dissociated cells were cultured, purified and passaged in vitro. Morphologic and genetic analysis and detection of surface biomarkers were performed on the cell line and primary tumor by immunofluorescence, immunohistochemical staining, DNA short tandem repeat (STR) analysis, karyotype analysis, and exome sequencing. Results: This human retinoblastoma cell line was designated as SNPH-Rb-C24. It expressed neural cell adhesion molecule 1 and synaptophysin, which confirmed its neuronal derivation. DNA STR analysis showed an identical match between SNPH-Rb-C24 and primary tumor. Karyotype analysis showed complex chromosomal abnormalities in SNPH-Rb-C24, while no alteration in 13q was observed. Comparative exome sequencing identified common mutated genes and RB1+/+ in both SNPH-Rb-C24 and primary tumor. Orthotopic xenograft tumors derived from early passage cells were established. Conclusion: A human retinoblastoma cell line (SNPH-Rb-C24) derived from a Han Chinese patient with RB1+/+ retinoblastoma is developed, which retains critical biological and genomic features of the donor tumor.

Emphasizing on the importance of RB1 genetic testing in diagnosis/treatment and genetic counseling of retinoblastoma / 中华实验眼科杂志

Retinoblastoma (RB) is the prototype of hereditary neoplasms in humans.It is the most common intraocular malignancy in children,which is mainly caused by RB1 gene mutation.RB1 genetic testing and genetic counseling supports optimal care and follow-up plan for RB patients and their families.RB is the first cancer to officially acknowledge the seminal role of genetics in cancer,by incorporating "H" into the eighth edition of cancer staging (2017);those who carry the RB1 cancer-predisposing gene are H1;those proven to not carry the familial RB1 mutation are H0;and those at unknown risk are HX.However,due to the complexity of RB1 gene mutation,the limitation of current genetic test,the lack of genetic counseling specialty,there is limited application of genetic testing and counseling in China.In the era of precision medicine,we need to advocate the application of RB1 genetic testing in the management of RB patients in China.

CGA codons multiplex PCR in rapid diagnosis of retinoblastoma.

Background: Multiplex polymerase chain reaction allows amplification of multiple target sequences of a genome under identical conditions in a single tube. This "one-shot" polymerase chain reaction detection is time and cost effective when large or multiple genes, with many target fragments are investigated. This is applicable for retinoblastoma susceptibility gene having 27 exons with recurrent mutations reported at most of the 12 CGA codons. Materials and Methods: Multiplex polymerase chain reaction assay for the amplification of 12 CGA codons, which constitutes about 50 % of retinoblastoma susceptibility gene mutations has been designed. The time and cost (includes only reagent cost) involved in both multiplex and uniplex polymerase chain reaction was also calculated. Results: Twelve CGA codons were multiplexed in 5 instead of 12 uniplex polymerase chain reactions, which took 36 hours and 9.78 US$ whereas multiplex polymerase chain reaction took 15 hours and 6.88 US$. Multiplex polymerase chain reaction method saved 58.3% of time and 29.6% of cost over uniplex polymerase chain reaction. Conclusion: Saving time by more than half and cost by nearly a third would help clinicians and geneticists while counseling retinoblastoma patients.

Germline Mutation of Rb1 Gene in Korean Retinoblastoma Patients / 대한암학회지

PURPOSE: Retinoblastoma is an intraocular tumor occurring almost exclusively in young children. Germline mutations in the Rb1 gene confer hereditary predisposition to retinoblastoma. To identify germline mutations in the Rb1 gene in Korean retinoblastoma patients, we analyzed germline mutations of the Rb1 gene in 4 Korean retinoblastoma patients from 3 families. MATERIALS AND METHODS: All patients were bilaterally affected in early childhood. First patient and second patient were same family members (SNU-RB1-1 and -2), and in the third patient (SNU-RB2), tumor cells had metastasized to the central nervous system 2 years after treatment of retinoblastoma. Fourth patient (SNU-RB3) developed secondary osteosarcoma in the nasal cavity 15 years after treatment of retinoblastoma. We have used PCR-SSCP analysis and DNA sequencing analysis to screen germline mutations. RESULTS: We found one missense mutation in the fourth patient (SNU-RB3). This was a point mutation from AAA (lysine) to GAA (glutamine) at codon 616 in exon 19 of the Rb1 gene. CONCLUSION: We confirmed one germline mutation of the Rb1 gene in one Korean patient who had a sporadic bilateral retinoblastoma and osteosarcoma. Identification of the germline mutation in Rb1 gene would help to improve the presymptomatic diagnosis and clinical management of retinoblastoma patients.

Deletion of Rb1 gene in late osteosarcoma from survivor of unilateral retinoblastoma: a case report

It has been well known that the survivors of retinoblastoma are prone to have osteosarcoma. But the secondary tumor usually occurs in bilateral, hereditary type of retinoblastoma. We report one case of osteosarcoma in a survivor of unilateral, sporadic retinoblastoma. A fourteen year old male presented with a painfully swollen distal forearm of 2 month duration. He had enucleated his left eye 10 years ago due to retinoblastoma with no other adjuvant therapy. We managed him with our conventional protocol and identified deletion of Rb gene from his pathological specimen by using the PCR-RFLP method. This result is unusual for unilateral nonhereditable retinoblastoma and may suggest gene level change even in sporadic cases. And Rb gene study may be helpful for unilateral, sporadic retinoblastoma patient in detecting the possibility of late osteosarcoma.

Loss of retinoblastoma gene and amplification of N-myc gene in retinoblastoma

We have analyzed paired samples of genomic DNA from peripheral leukocyte and primary tumor tissue from nine patients with retinoblastoma (RB) and from two RB cell lines, WERI-Rb-1 and Y79, to detect the molecular alterations of the retinoblastoma susceptibility gene (RB-1) and N-myc gene. In Southern analysis, RB-1 deletions in tumor tissues were detected in five patients (56%), one of these revealed a total loss of RB-1. N-myc amplification was found only in one (11.1%) out of nine patients. We also observed a total loss of RB-1 in WERI-Rb-1, and a more than 100-fold amplification of N-myc in Y79. The analysis of the relationship between molecular events and clinical characteristics such as age, sex, tumor laterality did not reveal any specific correlation. These results suggest that genetic backgrounds of RB in Korean patients are quite similar to those of reported cases elsewhere. The high sensitivity of our method in detecting the RB-1 loss indicates that this method can be a useful tool for initially screening a large number of tumors.