The Oncogene MYCN Modulates Glycolytic and Invasive Genes to Enhance Cell Viability and Migration in Human Retinoblastoma

Role of MYCN in retinoblastoma: A review of current literature

Chromosomal abnormalities that involve the MYCN gene are rare; however, it is one of the most commonly mutated genes in retinoblastoma (RB) after the RB1 gene. MYCN is amplified in approximately 1-9 % of all RB tumors. It plays a role in RB oncogenesis via many mechanisms, including synergism with RB1 deletion, positive feedback with MDM2, upregulation of cell cycle regulating genes, upregulation of miRNA, and upregulation of glucose metabolism. MYCN amplifications are not mutually exclusive and can occur even in the presence of RB1 gene mutations. Clinically, RB1+/+MYCNA tumors present as sporadic, unilateral, advanced tumors in very young children and tend to follow an aggressive course. Magnetic resonance imaging features include peripheral tumor location, placoid configuration, retinal folding, tumor-associated hemorrhage, and anterior chamber enhancement. Genetic testing for MYCNA is especially recommended in patients with unilateral RB where genetic blood testing and tumor tissue show a lack of RB1 mutation. MYCN-targeted therapies are evolving and hold promise for the future.

Aurora Kinase A Is Overexpressed in Human Retinoblastoma and Correlates with Histopathologic High-Risk Factors: Implications for Targeted Therapy

Retinoblastoma (RB) is an intraocular malignancy initiated by loss of RB1 function and/or dysregulation of MYCN oncogene. RB is primarily treated with chemotherapy; however, systemic toxicity and long-term adverse effects remain a significant challenge necessitating the identification of specific molecular targets. Aurora kinase A (AURKA), a critical cell cycle regulator, contributes to cancer pathogenesis, especially in RB1-deficient and MYCN-dysregulated tumors. The current immunohistochemistry study in patient specimens (n = 67) indicated that AURKA is overexpressed in RB, and this elevated expression correlates with one or more histopathologic high-risk factors, such as tumor involvement of the optic nerve, choroid, sclera, and/or anterior segment. More specifically, AURKA is ubiquitously expressed in most advanced-stage RB tumors that show a suboptimal response to chemotherapy. shRNA-mediated depletion/pharmacologic inhibition studies in cell lines, patient-derived cells, in vivo xenografts, and enucleated patient specimens confirmed that RB cells are highly sensitive to a lack of functional AURKA. In addition, AURKA and N-myc proto-oncogene protein (MYCN) associate with each other to regulate their levels in RB cells. Overall, these results demonstrate a previously unknown up-regulation of AURKA in RB, facilitated by its crosstalk with MYCN. The elevated levels of this kinase may indicate unfavorable prognosis in tumors refractory to chemotherapy. This study provides a rationale and confirms that therapeutic targeting of elevated AURKA in RB could be a potential treatment approach.

Retinoblastoma: An update on genetic origin, classification, conventional to next-generation treatment strategies

The most prevalent paediatric vision-threatening medical condition, retinoblastoma (RB), has been a global concern for a long time. Several conventional therapies, such as systemic chemotherapy and focal therapy, have been used for curative purposes; however, the search for tumour eradication with the least impact on surrounding tissues is still ongoing. This review focuses on the genetic origin, classification, conventional treatment modalities, and their combination with nano-scale delivery systems for active tumour targeting. In addition, the review also delves into ongoing clinical trials and patents, as well as emerging therapies such as gene therapy and immunotherapy for the treatment of RB. Understanding the role of genetics in the development of RB has refined its treatment strategy according to the genetic type. New approaches such as nanostructured drug delivery systems, galenic preparations, nutlin-3a, histone deacetylase inhibitors, N-MYC inhibitors, pentoxifylline, immunotherapy, gene therapy, etc. discussed in this review, have the potential to circumvent the limitations of conventional therapies and improve treatment outcomes for RB. In summary, this review highlights the importance and need for novel approaches as alternative therapies that would ultimately displace the shortcomings associated with conventional therapies and reduce the enucleation rate, thereby preserving global vision in the affected paediatric population.

Molecular Biological Research on the Pathogenic Mechanism of Retinoblastoma

Retinoblastoma (RB) is the most common intraocular malignant tumor in children, primarily attributed to the bi-allelic loss of the RB1 gene in the developing retina. Despite significant progress in understanding the basic pathogenesis of RB, comprehensively unravelling the intricate network of genetics and epigenetics underlying RB tumorigenesis remains a major challenge. Conventional clinical treatment options are limited, and despite the continuous identification of genetic loci associated with cancer pathogenesis, the development of targeted therapies lags behind. This review focuses on the reported genomic and epigenomic alterations in retinoblastoma, summarizing potential therapeutic targets for RB and providing insights for research into targeted therapies.

Identification of dysregulation of sphingolipids in retinoblastoma using liquid chromatography-mass spectrometry

Retinoblastoma (RB) is a rare ocular cancer seen in children that counts for approximately 3% of all childhood cancers. It is found that mutation in RB1, a tumour Suppressor Gene on chromosome 13 as the cause of malignancy. Retinoblastoma protein is the target for ceramide to cause apoptosis. We studied lipidomics of two RB cell lines, one aggressive cell line (NCC-RbC-51) derived from a metastatic site and one non aggressive cell line (WERI-Rb1) in comparison with a control cell line (MIO-M1). Lipid profiles of all the cell lines were studied using high resolution mass spectrometer coupled to high performance liquid chromatography. Data acquired from all the three cell lines in positive mode were analyzed to identify differentially expressed metabolites. Several phospholipids and lysophospholipids were found to be dysregulated. We observed upregulation of hexosyl ceramides, and down regulation of dihydroceramides and higher order sphingoglycolipids hinting at a hindered sphingolipid biosynthesis. The results obtained from liquid chromatography-mass spectrometry are validated by using qPCR and it was observed that genes involved in ceramide biosynthesis pathway are getting down regulated.

Lipid Metabolic Reprogramming in Embryonal Neoplasms with MYCN Amplification

Tumor cells reprogram their metabolism, including glucose, glutamine, nucleotide, lipid, and amino acids to meet their enhanced energy demands, redox balance, and requirement of biosynthetic substrates for uncontrolled cell proliferation. Altered lipid metabolism in cancer provides lipids for rapid membrane biogenesis, generates the energy required for unrestricted cell proliferation, and some of the lipids act as signaling pathway mediators. In this review, we focus on the role of lipid metabolism in embryonal neoplasms with MYCN dysregulation. We specifically review lipid metabolic reactions in neuroblastoma, retinoblastoma, medulloblastoma, Wilms tumor, and rhabdomyosarcoma and the possibility of targeting lipid metabolism. Additionally, the regulation of lipid metabolism by the MYCN oncogene is discussed.

PRMT5 promotes retinoblastoma development

Epigenetic mechanism, including DNA methylation and histone modifications, contributes to alterations in the expression patterns of genes regulating malignant phenotype of cancer cells. However, the epigenetic modulation of vascular endothelial growth factor-A (VEGFA) in retinoblastoma (RB) has not been clearly established. We aimed to examine the epigenetic regulation of VEGFA by protein arginine methyltransferase 5 (PRMT5) in RB. Using the GEO database, we identified VEGFA as a pathogenic gene in RB. Silencing of VEGFA in SO-RB50 and Y79 cells inhibited cell proliferation, angiogenesis, and migration, promoted apoptosis, and suppressed tumor growth in mice. Mechanistically, PRMT5 promoted H3K4me3 modification of the VEGFA promoter, thereby activating VEGFA expression. VEGFA could regulate the expression of MMP1, MMP2, and MMP9. Further silencing of VEGFA in RB cells overexpressing PRMT5 constrained the expression of MMP1, MMP2 and MMP9, and suppressed the growth of tumors in mice. In conclusion, this study clarifies that the depletion of PRMT5 reduces H3K4me3-mediated VEGFA transcription and retards the carcinogenesis of RB by suppressing the expression of MMPs.

Proteomics of Aqueous Humor as a Source of Disease Biomarkers in Retinoblastoma

Aqueous humor (AH) can be easily and safely used to evaluate disease-specific biomarkers in ocular disease. The aim of this study was to identify specific proteins biomarkers in the AH of retinoblastoma (RB) patients at various stages of the disease. We analyzed the proteome of 53 AH samples using high-resolution mass spectrometry. We grouped the samples according to active vitreous seeding (Group 1), active aqueous seeding (Group 2), naive RB (group 3), inactive RB (group 4), and congenital cataracts as the control (Group 5). We found a total of 889 proteins in all samples. Comparative parametric analyses among the different groups revealed three additional proteins expressed in the RB groups that were not expressed in the control group. These were histone H2B type 2-E (HISTH2B2E), InaD-like protein (PATJ), and ubiquitin conjugating enzyme E2 V1 (UBE2V1). Upon processing the data of our study with the OpenTarget Tool software, we found that glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and CD44 were more highly expressed in the RB groups. Our results provide a proteome database regarding AH related to RB disease that may be used as a source of biomarkers. Further prospective studies should validate our finding in a large cohort of RB patients.

Characterizing DNA methylation signatures of retinoblastoma using aqueous humor liquid biopsy

Retinoblastoma (RB) is a cancer that forms in the developing retina of babies and toddlers. The goal of therapy is to cure the tumor, save the eye and maximize vision. However, it is difficult to predict which eyes are likely to respond to therapy. Predictive molecular biomarkers are needed to guide prognosis and optimize treatment decisions. Direct tumor biopsy is not an option for this cancer; however, the aqueous humor (AH) is an alternate source of tumor-derived cell-free DNA (cfDNA). Here we show that DNA methylation profiling of the AH is a valid method to identify the methylation status of RB tumors. We identify 294 genes directly regulated by methylation that are implicated in p53 tumor suppressor (RB1, p53, p21, and p16) and oncogenic (E2F) pathways. Finally, we use AH to characterize molecular subtypes that can potentially be used to predict the likelihood of treatment success for retinoblastoma patients.

MYCN induces cell-specific tumorigenic growth in RB1-proficient human retinal organoid and chicken retina models of retinoblastoma

Retinoblastoma is a rare, intraocular paediatric cancer that originates in the neural retina and is most frequently caused by bi-allelic loss of RB1 gene function. Other oncogenic mutations, such as amplification and increased expression of the MYCN gene, have been found even with proficient RB1 function. In this study, we investigated whether MYCN over-expression can drive carcinogenesis independently of RB1 loss-of-function mutations. The aim was to elucidate the events that result in carcinogenesis and identify the cancer cell-of-origin. We used the chicken retina, a well-established model for studying retinal neurogenesis, and established human embryonic stem cell-derived retinal organoids as model systems. We over-expressed MYCN by electroporation of piggyBac genome-integrating expression vectors. We found that over-expression of MYCN induced tumorigenic growth with high frequency in RB1-proficient chicken retinas and human organoids. In both systems, the tumorigenic cells expressed markers for undifferentiated cone photoreceptor/horizontal cell progenitors. The over-expression resulted in metastatic retinoblastoma within 7–9 weeks in chicken. Cells expressing MYCN could be grown in vitro and, when orthotopically injected, formed tumours that infiltrated the sclera and optic nerve and expressed markers for cone progenitors. Investigation of the tumour cell phenotype determined that the potential for neoplastic growth was embryonic stage-dependent and featured a cell-specific resistance to apoptosis in the cone/horizontal cell lineage, but not in ganglion or amacrine cells. We conclude that MYCN over-expression is sufficient to drive tumorigenesis and that a cell-specific resistance to apoptosis in the cone/horizontal cell lineage mediates the cancer phenotype.