Retinoblastoma: from discovery to clinical management.

The retinoblastoma gene (RB1) was the first tumour suppressor cloned; the role of its protein product (RB) as the principal driver of the G1 checkpoint in cell cycle control has been extensively studied. However, many other RB functions are continuously reported. Its role in senescence, DNA repair and apoptosis, among others, is indications of the significance of RB in a vast network of cellular interactions, explaining why RB loss or its malfunction is one of the leading causes of a large number of paediatric and adult cancers. RB was first reported in retinoblastoma, a common intraocular malignancy in the paediatric population worldwide. Currently, its diagnosis is clinical, and in nondeveloped countries, where the incidence is higher, it is performed in advanced stages of the disease, compromising the integrity of the eye and the patient's life. Even though new treatments are being continuously developed, enucleation is still a major choice due to the late disease stage diagnosis and treatments costs. Research into biomarkers is our best option to improve the chances of good results in the treatment and hopes of patients' good quality of life. Here, we recapitulated the history of the disease and the first treatments to put the advances in its clinical management into perspective. We also review the different functions of the protein and the progress in the search for biomarkers. It is clear that there is still a long way to go, but we should offer these children and their families a better way to deal with the disease with the community's effort.

Eag1 Gene and Protein Expression in Human Retinoblastoma Tumors and its Regulation by pRb in HeLa Cells.

Retinoblastoma is the most common pediatric intraocular malignant tumor. Unfortunately, low cure rates and low life expectancy are observed in low-income countries. Thus, alternative therapies are needed for patients who do not respond to current treatments or those with advanced cases of the disease. Ether à-go-go-1 (Eag1) is a voltage-gated potassium channel involved in cancer. Eag1 expression is upregulated by the human papilloma virus (HPV) oncogene E7, suggesting that retinoblastoma protein (pRb) may regulate Eag1. Astemizole is an antihistamine that is suggested to be repurposed for cancer treatment; it targets proteins implicated in cancer, including histamine receptors, ATP binding cassette transporters, and Eag channels. Here, we investigated Eag1 regulation using pRb and Eag1 expression in human retinoblastoma. The effect of astemizole on the cell proliferation of primary human retinoblastoma cultures was also studied. HeLa cervical cancer cells (HPV-positive and expressing Eag1) were transfected with RB1. Eag1 mRNA expression was studied using qPCR, and protein expression was assessed using western blotting and immunochemistry. Cell proliferation was evaluated with an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. RB1 transfection down-regulated Eag1 mRNA and protein expression. The human retinoblastoma samples displayed heterogeneous Eag1 mRNA and protein expression. Astemizole decreased cell proliferation in primary retinoblastoma cultures. Our results suggest that Eag1 mRNA and protein expression was regulated by pRb in vitro, and that human retinoblastoma tissues had heterogeneous Eag1 mRNA and protein expression. Furthermore, our results propose that the multitarget drug astemizole may have clinical relevance in patients with retinoblastoma, for instance, in those who do not respond to current treatments.

Expression and purification of the recombinant full-length retinoblastoma protein and characterisation of its interaction with the oncoprotein HDM2.

Retinoblastoma (Rb) was the first tumour suppressor factor described, and it is dysfunctional in several types of cancers. Structurally, Rb is a very large, multifunctional protein organized in different domains connected by intrinsically disordered regions. Due to the complex structure of Rb, biochemical manipulation is difficult. The Rb protein has been implicated in many different cellular processes, such as the cell cycle control, senescence and even apoptosis. The activity of Rb is regulated by phosphorylation, and many different sites of phosphorylation have been described. However, the oncoprotein HDM2, can promote Rb degradation by the proteasome. This form of Rb regulation is largely unknown. Here we report the expression and purification of the full-length Rb protein and its phosphomimetic form, Rb(S567D), in a recombinant system. We also produced and purified the HDM2 protein and its phosphomimetic mutant, HDM2(S395D). The proteins interacted strongly when we used the phosphomimetic mutants, mimicking damaged DNA conditions. The expression of the proteins in E. coli allowed us to control the phosphorylation status of the proteins.

Hyper-phosphorylation of Rb S249 together with CDK5R2/p39 overexpression are associated with impaired cell adhesion and epithelial-to-mesenchymal transition: Implications as a potential lung cancer grading and staging biomarker.

Prediction of lung cancer metastasis relies on post-resection assessment of tumor histology, which is a severe limitation since only a minority of lung cancer patients are diagnosed with resectable disease. Therefore, characterization of metastasis-predicting biomarkers in pre-resection small biopsy specimens is urgently needed. Here we report a biomarker consisting of the phosphorylation of the retinoblastoma protein (Rb) on serine 249 combined with elevated p39 expression. This biomarker correlates with epithelial-to-mesenchymal transition traits in non-small cell lung carcinoma (NSCLC) cells. Immunohistochemistry staining of NSCLC tumor microarrays showed that strong phospho-Rb S249 staining positively correlated with tumor grade specifically in the squamous cell carcinoma (SCC) subtype. Strong immunoreactivity for p39 positively correlated with tumor stage, lymph node invasion, and distant metastases, also in SCC. Linear regression analyses showed that the combined scoring for phospho-Rb S249, p39 and E-cadherin in SCC is even more accurate at predicting tumor staging, relative to each score individually. We propose that combined immunohistochemistry staining of NSCLC samples for Rb phosphorylation on S249, p39, and E-cadherin protein expression could aid in the assessment of tumor staging and metastatic potential when tested in small primary tumor biopsies. The intense staining for phospho-Rb S249 that we observed in high grade SCC could also aid in the precise sub-classification of poorly differentiated SCCs.

microRNA-3129 promotes cell proliferation in gastric cancer cell line SGC7901 via positive regulation of pRb.

Several microRNAs (miRNAs) have been reported as oncogenes or tumor suppressors in many cancers, including gastric cancer (GC). However, the role and molecular mechanism of miR-3129 in GC is largely unknown. We aimed to explore the function and the underlying molecular mechanism of miR-3129 in GC. Cancer tissues and corresponding adjacent tissues were collected from 50 patients with GC, and the expression of miR-3129 was detected by RT-qPCR. The expression of miR-3129 and pRb in human GC cell line SCG7091 was altered by transient transfection. Thereafter, MTT and flow cytometry assays were used to analyze cell viability and cell cycle. The expression of cyclin E, CDK2, CDK2 inhibitors (p16 and 21), and pRb were detected by RT-qPCR and western blot. A significant up-regulation of miR-3129 was observed in GC tissues compared to adjacent tissues. Overexpression of miR-3129 significantly improved cell viability after 4 days of post-transfection. Flow cytometry assay results showed that the miR-3129 overexpression arrested more SGC7901 cells at S phase. Moreover, overexpression of miR-3129 down-regulated the expression of CDK2 inhibitors while it up-regulated the expression levels of cyclin E, CDK2, and pRb. Interestingly, we found that pRb inhibition reversed the effect of miR-3129 inhibitor on cell proliferation in SGC7901 cells, increased cell viability, reduced cells at G0/1 phase, and modulated the expression of proliferation-related factors. Our results revealed that miR-3129 functioned as an oncogene through positive regulation of pRb and may prove to be a promising option for molecular therapy of GC.

microRNA-3129 promotes cell proliferation in gastric cancer cell line SGC7901 via positive regulation of pRb

Several microRNAs (miRNAs) have been reported as oncogenes or tumor suppressors in many cancers, including gastric cancer (GC). However, the role and molecular mechanism of miR-3129 in GC is largely unknown. We aimed to explore the function and the underlying molecular mechanism of miR-3129 in GC. Cancer tissues and corresponding adjacent tissues were collected from 50 patients with GC, and the expression of miR-3129 was detected by RT-qPCR. The expression of miR-3129 and pRb in human GC cell line SCG7091 was altered by transient transfection. Thereafter, MTT and flow cytometry assays were used to analyze cell viability and cell cycle. The expression of cyclin E, CDK2, CDK2 inhibitors (p16 and 21), and pRb were detected by RT-qPCR and western blot. A significant up-regulation of miR-3129 was observed in GC tissues compared to adjacent tissues. Overexpression of miR-3129 significantly improved cell viability after 4 days of post-transfection. Flow cytometry assay results showed that the miR-3129 overexpression arrested more SGC7901 cells at S phase. Moreover, overexpression of miR-3129 down-regulated the expression of CDK2 inhibitors while it up-regulated the expression levels of cyclin E, CDK2, and pRb. Interestingly, we found that pRb inhibition reversed the effect of miR-3129 inhibitor on cell proliferation in SGC7901 cells, increased cell viability, reduced cells at G0/1 phase, and modulated the expression of proliferation-related factors. Our results revealed that miR-3129 functioned as an oncogene through positive regulation of pRb and may prove to be a promising option for molecular therapy of GC.

RB1 gene mutations in Argentine retinoblastoma patients. Implications for genetic counseling.

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.

Rb family proteins enforce the homeostasis of quiescent hematopoietic stem cells by repressing Socs3 expression.

Prolonged exit from quiescence by hematopoietic stem cells (HSCs) progressively impairs their homeostasis in the bone marrow through an unidentified mechanism. We show that Rb proteins, which are major enforcers of quiescence, maintain HSC homeostasis by positively regulating thrombopoietin (Tpo)-mediated Jak2 signaling. Rb family protein inactivation triggers the progressive E2f-mediated transactivation of Socs3, a potent inhibitor of Jak2 signaling, in cycling HSCs. Aberrant activation of Socs3 impairs Tpo signaling and leads to impaired HSC homeostasis. Therefore, Rb proteins act as a central hub of quiescence and homeostasis by coordinating the regulation of both cell cycle and Jak2 signaling in HSCs.

Study of polymorphisms in the TP53 and RB1 genes in children with retinoblastoma in northern Mexico.

PURPOSE: To determine the frequency and association of polymorphisms in the TP53 and RB1 genes with clinical characteristics in a group of children with retinoblastoma (RB) in northern Mexico. METHODS: A prospective, longitudinal, and analytical study of 11 patients diagnosed with RB was conducted. Endpoint PCR and high-resolution real-time PCR were performed. Chi-square and Student t tests were used to evaluate associations between variables. Allelic frequencies, as well as genotypic and Hardy-Weinberg equilibriums, were evaluated using Guo and Thompson's method. RESULTS: We found a statistically significant difference between the polymorphism RB1-GG/rs9568036 and tumor chemoresistance (p<0.05). The allelic variants RB1-AA and AG/rs9568036 were determined to be associated with tumor chemosensitivity (p<0.05). A statistically significant relation between the polymorphism RB1-GG/rs9568036 and males (p = 0.0386), rate ratio (RR) = 2.0 (95% confidence interval [CI] = 0.76-5.32), as well as between the allelic variants RB1-AA and AG/rs9568036 and females (p = 0.0027), RR = 8.0 (95% CI = 1.28-50.04), was observed. We also observed a statistically significant association between the rs1042522 polymorphism in the TP53 gene and unilateral presentation of the disease. CONCLUSIONS: The rs9568036 polymorphism in the RB1 gene and the allelic variants can be associated with type of response to medical therapy and associated with male sex, while the allelic variant rs1042522 polymorphism in the TP53 gene is associated with the unilateral presentation of the disease in a group of Mexican children with RB.

Expression Analysis of Genes Involved in the RB/E2F Pathway in Astrocytic Tumors.

Astrocytic gliomas, which are derived from glial cells, are considered the most common primary neoplasias of the central nervous system (CNS) and are histologically classified as low grade (I and II) or high grade (III and IV). Recent studies have shown that astrocytoma formation is the result of the deregulation of several pathways, including the RB/E2F pathway, which is commonly deregulated in various human cancers via genetic or epigenetic mechanisms. On the basis of the assumption that the study of the mechanisms controlling the INK4/ARF locus can help elucidate the molecular pathogenesis of astrocytic tumors, identify diagnostic and prognostic markers, and help select appropriate clinical treatments, the present study aimed to evaluate and compare methylation patterns using bisulfite sequencing PCR and evaluate the gene expression profile using real-time PCR in the genes CDKN2A, CDKN2B, CDC6, Bmi-1, CCND1, and RB1 in astrocytic tumors. Our results indicate that all the evaluated genes are not methylated independent of the tumor grade. However, the real-time PCR results indicate that these genes undergo progressive deregulation as a function of the tumor grade. In addition, the genes CDKN2A, CDKN2B, and RB1 were underexpressed, whereas CDC6, Bmi-1, and CCND1 were overexpressed; the increase in gene expression was significantly associated with decreased patient survival. Therefore, we propose that the evaluation of the expression levels of the genes involved in the RB/E2F pathway can be used in the monitoring of patients with astrocytomas in clinical practice and for the prognostic indication of disease progression.

Uncommon RB1 somatic mutations in a unilateral retinoblastoma patient.

Retinoblastoma (RB) is the most common primary intraocular malignancy in children. Somatic inactivation of both alleles of the RB1 tumor suppressor gene in a developing retina is a crucial event in the initiation of tumorigenesis in most cases of isolated unilateral retinoblastoma. We analyzed the DNA from tumor tissue and peripheral blood of a unilateral retinoblastoma patient to determine the RB1 mutation status and to provide an accurate genetic counseling. A comprehensive approach, based on our previous experience, was used to identify the causative RB1 mutations. Screening for RB1 mutations was performed by PCR direct sequencing, multiplex ligation-dependent probe amplification (MLPA) and Real Time-PCR analyses. Three different mutations were identified in the tumor DNA, which were absent in blood DNA. The somatic origin of these mutations was vital to rule out the heritable condition in this patient.

Association between human papillomavirus and Epstein - Barr virus DNA and gene promoter methylation of RB1 and CDH1 in the cervical lesions: a transversal study.

BACKGROUND: Human papillomavirus (HPV) inactivates the retinoblastoma 1 (RB1) gene by promoter methylation and reduces cellular E-cadherin expression by overexpression of DNA methyltransferase 1 (DNMT1). The Epstein-Barr virus (EBV) is an oncogenic virus that may be related to cervical carcinogenesis. In gastric cancer, it has been demonstrated that E-cadherin gene (CDH1) hypermethylation is associated with DNMT1 overexpression by EBV infection. Our aim was to analyze the gene promoter methylation frequency of RB1 and CDH1 and verify the association between that methylation frequency and HPV and EBV infection in cervical lesions. METHODS: Sixty-five samples were obtained from cervical specimens: 15 normal cervices, 17 low-grade squamous intraepithelial lesions (LSIL), 15 high-grade squamous intraepithelial lesions (HSIL), and 18 cervical cancers. HPV and EBV DNA testing was performed by PCR, and the methylation status was verified by MSP. RESULTS: HPV frequency was associated with cervical cancer cases (p = 0.005) but not EBV frequency (p = 0.732). Viral co-infection showed a statistically significant correlation with cancer (p = 0.027). No viral infection was detected in 33.3% (5/15) of controls. RB1 methylated status was associated with cancer (p = 0.009) and HPV infection (p = 0.042). CDH1 methylation was not associated with cancer (p = 0.181). Controls and LSIL samples did not show simultaneous methylation, while both genes were methylated in 27.8% (5/18) of cancer samples. In the presence of EBV, CDH1 methylation was present in 27.8% (5/18) of cancer samples. Only cancer cases presented RB1 promoter methylation in the presence of HPV and EBV (33.3%). CONCLUSIONS: The methylation status of both genes increased with disease progression. With EBV, RB1 methylation was a tumor-associated event because only the cancer group presented methylated RB1 with HPV infection. HPV infection was shown to be significantly correlated with cancer conditions. The global methylation frequency was higher when HPV was present, showing its epigenetic role in cervical carcinogenesis. Nevertheless, EBV seems to be a cofactor and needs to be further investigated. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1159157579149317 .

Uncommon RB1 somatic mutations in a unilateral retinoblastoma patient

Retinoblastoma (RB) is the most common primary intraocular malignancy in children. Somatic inactivation of both alleles of the RB1 tumor suppressor gene in a developing retina is a crucial event in the initiation of tumorigenesis in most cases of isolated unilateral retinoblastoma. We analyzed the DNA from tumor tissue and peripheral blood of a unilateral retinoblastoma patient to determine the RB1 mutation status and to provide an accurate genetic counseling. A comprehensive approach, based on our previous experience, was used to identify the causative RB1 mutations. Screening for RB1 mutations was performed by PCR direct sequencing, multiplex ligation-dependent probe amplification (MLPA) and Real Time-PCR analyses. Three different mutations were identified in the tumor DNA, which were absent in blood DNA. The somatic origin of these mutations was vital to rule out the heritable condition in this patient.

El retinoblastoma (RB) es el cáncer ocular más común de la niñez. La inactivación somática de ambos alelos del gen supresor de tumores RB1 en la retina en desarrollo es un evento crucial en la iniciación de la tumorigénesis en la mayoría de los casos de retinoblastoma unilateral. Nosotros analizamos el ADN de tumor y de sangre periférica de un paciente con retinoblastoma unilateral para identificar las mutaciones y así proveer un asesoramiento genético a la familia. Para ello utilizamos un protocolo basado en nuestra previa experiencia para identificar todas las mutaciones en el gen RB1 que causaron el RB. El rastreo de mutaciones se realizó por medio de los siguientes análisis: PCR-secuenciación, amplificación multiplex de sondas ligadas (MLPA) y PCR-Tiempo Real. Se encontraron tres mutaciones diferentes en el ADN del tumor, las cuales estaban ausentes en el ADN de la sangre. El origen somático de estas mutaciones es importante para indicar que la enfermedad no es hereditaria.

Gene expression of the p16(INK4a)-Rb and p19(Arf)-p53-p21(Cip/Waf1) signaling pathways in the regulation of hematopoietic stem cell aging by ginsenoside Rg1.

The elucidation of the molecular mechanisms underlying the effects of traditional Chinese medicines in clinical practice is a key step toward their worldwide application, and this topic is currently a subject of intense research interest. Rg1, a component of ginsenoside, has recently been shown to perform several pharmacological functions; however, the underlying mechanisms of these effects remain unclear. In the present study, we investigated whether Rg1 has an anti-senescence effect on hematopoietic stem cells (HSCs) and the possible molecular mechanisms driving any effects. The results showed that Rg1 could effectively delay tert-butyl hydroperoxide (t-BHP)-induced senescence and inhibit gene expression in the p16(INK4a)-Rb and p19(Arf)-p53-p21(Cip/Waf1) signaling pathways in HSCs. Our study suggested that these two signaling pathways might be potential targets for elucidating the molecular mechanisms of the Rg1 anti-senescence effect.

Increased incidence and disparity of diagnosis of retinoblastoma patients in Guatemala.

Analysis of 327 consecutive cases at a pediatric referral hospital of Guatemala reveals that retinoblastoma accounts for 9.4% of all cancers and the estimated incidence is 7.0 cases/million children, higher than the United States or Europe. The number of familial cases is low, and there is a striking disparity in indigenous children due to late diagnosis, advanced disease, rapid progression and elevated mortality. Nine germline mutations in 18 patients were found; two known and five new mutations. Hypermethylation of RB1 was identified in 13% of the tumors. An early diagnosis program could identify cases at an earlier age and improve outcome of retinoblastoma in this diverse population.

HOXB7 mRNA is overexpressed in pancreatic ductal adenocarcinomas and its knockdown induces cell cycle arrest and apoptosis.

BACKGROUND: Human homeobox genes encode nuclear proteins that act as transcription factors involved in the control of differentiation and proliferation. Currently, the role of these genes in development and tumor progression has been extensively studied. Recently, increased expression of HOXB7 homeobox gene (HOXB7) in pancreatic ductal adenocarcinomas (PDAC) was shown to correlate with an invasive phenotype, lymph node metastasis and worse survival outcomes, but no influence on cell proliferation or viability was detected. In the present study, the effects arising from the knockdown of HOXB7 in PDAC cell lines was investigated. METHODS: Real time quantitative PCR (qRT-PCR) (Taqman) was employed to assess HOXB7 mRNA expression in 29 PDAC, 6 metastatic tissues, 24 peritumoral tissues and two PDAC cell lines. siRNA was used to knockdown HOXB7 mRNA in the cell lines and its consequences on apoptosis rate and cell proliferation were measured by flow cytometry and MTT assay respectively. RESULTS: Overexpression of HOXB7 mRNA was observed in the tumoral tissues and in the cell lines MIA PaCa-2 and Capan-1. HOXB7 knockdown elicited (1) an increase in the expression of the pro-apoptotic proteins BAX and BAD in both cell lines; (2) a decrease in the expression of the anti-apoptotic protein BCL-2 and in cyclin D1 and an increase in the number of apoptotic cells in the MIA PaCa-2 cell line; (3) accumulation of cell in sub-G1 phase in both cell lines; (4) the modulation of several biological processes, especially in MIA PaCa-2, such as proteasomal ubiquitin-dependent catabolic process and cell cycle. CONCLUSION: The present study confirms the overexpression of HOXB7 mRNA expression in PDAC and demonstrates that decreasing its protein level by siRNA could significantly increase apoptosis and modulate several biological processes. HOXB7 might be a promising target for future therapies.

The metastatic behavior of osteosarcoma by gene expression and cytogenetic analyses.

Osteosarcoma is a malignant bone tumor with high metastatic potential. Metastasis at diagnosis is the most significant prognostic factor in predicting the clinical outcome of osteosarcoma. We compared the gene expression of metastases that were present at the time of initial diagnosis to those developed later in the course of the disease. We used quantitative real-time polymerase chain reaction to evaluate the gene expression of MDM2, CXCR4, RANKL, RB1, and OSTERIX in 98 samples of osteosarcoma taken from 47 patients (74 metastases and 24 primary tumors) and 30 nonmalignant lung tissues surrounding osteosarcoma metastases. In addition, we investigated the copy number changes of RB1 and MDM2 genes in 12 primary cultures of pulmonary metastases of osteosarcoma, using interphase fluorescence in situ hybridization. Metastases from metastatic patients at diagnosis were characterized by low expression of RB1 and RANKL (P = .0009 and P = .0109, respectively) and overexpression of CXCR4 and MDM2 (P = .0389 and P = .0325, respectively). The loss of RANKL and gain of CXCR4 could also be detected in the primary tumors of metastatic patients at diagnosis (P = .0121 and P = .0264, respectively). Thus, some early genetic events such as the loss of RANKL and the gain of CXCR4 expressions probably facilitate the metastatic progression concomitant with the primary tumor establishment, supporting the role of the CXCR4 receptor in directing osteosarcoma metastases to the lung. On the other hand, late events such as the loss of RB1 and gain of MDM2, crucial regulators of cell cycle, appear to be related to the final mechanisms contributing to the metastatic establishment of osteosarcoma.

Screening of RB1 alterations in Brazilian patients with retinoblastoma and relatives with retinoma: phenotypic and genotypic associations.

PURPOSE: To identify constitutional alterations of the retinoblastoma 1 gene (RB1) in two cohorts of Brazilian patients with retinoblastoma and to analyze genotype-phenotype associations. METHODS: Molecular screening was carried out by direct sequencing of the 27 RB1 exons and flanking regions in blood DNA of 71 patients with retinoblastoma and 4 relatives with retinoma, and with multiplex ligation-dependent probe amplification (MLPA) in 21 patients. The presumed impact of nucleotide substitutions on the structure of the retinoblastoma protein (pRB) was predicted by Polymorphism Phenotyping-2 (PolyPhen-2). Kaplan-Meier and log-rank test were used for estimating 60-month survival rates. RESULTS: One hundred two nucleotide substitutions were detected, 92 substitutions in 59 patients with retinoblastoma and 10 substitutions in 4 individuals with retinoma. Eight substitutions were novel. The majority of substitutions were intronic (86.2%). More than one substitution was present in 37.3% of patients. Twenty-one duplications and 11 deletions were found in 12 patients; some of which with both types of alterations. Duplications/deletions were found in four patients lacking constitutional alterations when analyzed by sequencing, and in eight patients carrying one or more polymorphic intronic substitutions. The global 60-month survival rate in patients was 91.8% (Confidence Interval95% = 85.0 - 99.1). Significant, lower survival rates were found in extraocular presentation (81.0%) versus intraocular tumors (P = 0.014), first enucleation after 1 month following diagnosis (80.9%) versus earlier first enucleation (P = 0.020), and relapse (100.0%) versus absence of relapse (P = 0.0005). CONCLUSIONS: Fifteen substitutions (4 intronic and 11 exonic) were identified as probably or likely pathogenic. Four of these 11 exonic substitutions were novel. Survival rates, however, were not affected by presence of these probably or likely pathogenic alterations, most of which not found in patients with retinoblastoma from other Latin American countries. These differences might be related to the different ethnic composition of the Latin American cohorts. Portuguese Abstract.

Spectrum of RB1 mutations in argentine patients: 20-years experience in the molecular diagnosis of retinoblastoma.

BACKGROUND: Retinoblastoma is a hereditary cancer of childhood caused by mutations in the RB1 tumor suppressor gene. An early diagnosis is critical for survival and eye preservation, thus identification of RB1 mutations is important for unequivocal diagnosis of hereditary retinoblastoma and risk assessment in relatives. METHODS: We studied 144 families for 20 years, performing methodological changes to improve detection of mutation. Segregation analysis of polymorphisms, MLPA, FISH and cytogenetic assays were used for detection of "at risk haplotypes" and large deletions. Small mutations were identified by heteroduplex/DNA sequencing. RESULTS: At risk haplotypes were identified in 11 familial and 26 sporadic cases, being useful for detection of asymptomatic carriers, risk exclusion from relatives and uncovering RB1 recombinations. Ten large deletions (eight whole gene deletions) were identified in six bilateral/familial and four unilateral retinoblastoma cases. Small mutations were identified in 29 cases (four unilateral retinoblastoma patients), being the majority nonsense/frameshift mutations. Genotype-phenotype correlations confirm that the retinoblastoma presentation is related to the type of mutation, but some exceptions may occur and it is crucial to be considered for genetic counseling. Three families included second cousins with retinoblastoma carrying different haplotypes, which suggest independent mutation events. CONCLUSION: This study enabled us to obtain information about molecular and genetic features of patients with retinoblastoma in Argentina and correlate them to their phenotype.

Gamma-tocotrienol modulation of senescence-associated gene expression prevents cellular aging in human diploid fibroblasts.

OBJECTIVE: Human diploid fibroblasts undergo a limited number of cellular divisions in culture and progressively reach a state of irreversible growth arrest, a process termed cellular aging. The beneficial effects of vitamin E in aging have been established, but studies to determine the mechanisms of these effects are ongoing. This study determined the molecular mechanism of γ-tocotrienol, a vitamin E homolog, in the prevention of cellular aging in human diploid fibroblasts using the expression of senescence-associated genes. METHODS: Primary cultures of young, pre-senescent, and senescent fibroblast cells were incubated with γ-tocotrienol for 24 h. The expression levels of ELN, COL1A1, MMP1, CCND1, RB1, and IL6 genes were determined using the quantitative real-time polymerase chain reaction. Cell cycle profiles were determined using a FACSCalibur Flow Cytometer. RESULTS: The cell cycle was arrested in the G(0)/G(1) phase, and the percentage of cells in S phase decreased with senescence. CCND1, RB1, MMP1, and IL6 were upregulated in senescent fibroblasts. A similar upregulation was not observed in young cells. Incubation with γ-tocotrienol decreased CCND1 and RB1 expression in senescent fibroblasts, decreased cell populations in the G(0)/G(1) phase and increased cell populations in the G(2)/M phase. γ-Tocotrienol treatment also upregulated ELN and COL1A1 and downregulated MMP1 and IL6 expression in young and senescent fibroblasts. CONCLUSION: γ-Tocotrienol prevented cellular aging in human diploid fibroblasts, which was indicated by the modulation of the cell cycle profile and senescence-associated gene expression.