Mutations in the RB1 locus leading to a loss of functional Rb protein cause intraocular tumors, which uniquely affect children worldwide. These tumors demonstrate rapid proliferation, which has recently been shown to be associated with an altered metabolic signature. We found that retinoblastoma tumors and in-vitro models lack Hexokinase 1 (HK1) and exhibit elevated fatty acid oxidation. We show that ectopic expression of RB1 induces HK1 protein in Rb null cells, and both RB1 and HK1 can mediate a metabolic switch from OXPHOS to glycolysis with increased pyruvate levels, reduced ATP production and reduced mitochondrial mass. Further, cells lacking Rb or HK1 can flexibly utilize glutamine and fatty acids to enhance oxidative phosphorylation-dependent ATP generation, as revealed by metabolic and biochemical assays. Thus, loss of Rb and HK1 in retinoblastoma reprograms tumor metabolic circuits to enhance the glucose-independent TCA (tricarboxylic acid) cycle and the intermediate NAD+/NADH ratios, with a subsequent increase in fatty-acid derived L-carnitine to enhance mitochondrial OXPHOS for ATP production instead of glycolysis dependence. We also demonstrate that modulation of the Rb-regulated transcription factor E2F2 does not result in any of these metabolic perturbations. In conclusion, we demonstrate RB1 or HK1 as critical regulators of the cellular bioenergetic profile and identify the altered tumor metabolism as a potential therapeutic target for cancers lacking functional Rb protein.

Advanced retinoblastoma (Rb) tumors display high metastatic spread to distant tissues, causing a potent threat to vision and life. Through transcriptomic profiling, we discovered key upregulated genes that belonged to the epithelial–mesenchymal transition (EMT) and chemotherapy resistance pathways in advanced Rb tumors. Through in vitro models, we further showed that Rb null tumor cells under prolonged chemo drug exposure, acquires a metastasis-like phenotype through the EMT program mediated by ZEB1 and SNAI2 and these cells further acquires chemotherapeutic resistance through cathepsin-L- and MDR1-mediated drug efflux mechanisms. Using a miRNA microarray, we identified miR-181a-5p as being significantly reduced in advanced Rb tumors, which was associated with an altered EMT and drug-resistance genes. We showed that enhancing miR-181a-5p levels in Rb null chemo-resistant sublines reduced the ZEB1 and SNAI2 levels and halted the mesenchymal transition switch, further reducing the drug resistance. We thus identified miR-181a-5p as a therapeutically exploitable target for EMT-triggered drug-resistant cancers that halted their invasion and migration and sensitized them to low-dose chemotherapy drugs.

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.

Retinoblastoma (Rb) is a pediatric intraocular malignancy that is proposed to originate from maturing cone cell precursors in the developing retina. The molecular mechanisms underlying the biological and clinical behaviors are important to understand in order to improve the management of advanced-stage tumors. While the genetic causes of Rb are known, an integrated understanding of the gene expression and metabolic processes in tumors of human eyes is deficient. By integrating transcriptomic profiling from tumor tissues and metabolomics from tumorous eye vitreous humor samples (with healthy, age-matched pediatric retinae and vitreous samples as controls), we uncover unique functional associations between genes and metabolites. We found distinct gene expression patterns between clinically advanced and non-advanced Rb. Global metabolomic analysis of the vitreous humor of the same Rb eyes revealed distinctly altered metabolites, indicating how tumor metabolism has diverged from healthy pediatric retina. Several key enzymes that are related to cellular energy production, such as hexokinase 1, were found to be reduced in a manner corresponding to altered metabolites; notably, a reduction in pyruvate levels. Similarly, E2F2 was the most significantly elevated E2F family member in our cohort that is part of the cell cycle regulatory circuit. Ectopic expression of the wild-type RB1 gene in the Rb-null Y79 and WERI-Rb1 cells rescued hexokinase 1 expression, while E2F2 levels were repressed. In an additional set of Rb tumor samples and pediatric healthy controls, we further validated differences in the expression of HK1 and E2F2. Through an integrated omics analysis of the transcriptomics and metabolomics of Rb, we uncovered a significantly altered tumor-specific metabolic circuit that reduces its dependence on glycolytic pathways and is governed by Rb1 and HK1.

Age‐related macular degeneration (AMD), a leading cause of vision loss affecting retinal pigment epithelial (RPE) cells, remains largely unexplained by current genome‐wide association studies (GWAS) risk variants. Our research on Cryba1 , encoding βA3/A1‐crystallin protein, reveals its crucial role in RPE cell function via a novel epigenetic mechanism, also evident in human atrophic AMD samples. Loss of Cryba1 in mouse RPE cells triggers epigenetic changes by reducing histone deacetylase 3 (HDAC3) activity through two mechanisms. First, Cryba1 depletion reduces inositol polyphosphate multikinase (IPMK) expression, which potentially reduces inositol hexakisphosphate (InsP6) generation since IPMK's kinase activity is essential for producing InsP4 and InsP5 as precursors to InsP6. Since InsP4, InsP5, or InsP6 is crucial for HDAC3's interaction with the corepressor's DAD domains, reduced IPMK expression in Cryba1 ‐depleted cells likely diminishes the HDAC3‐DAD interaction, leading to a reduction in HDAC3's activity. Second, reduced βA3/A1 protein in Cryba1 ‐deficient cells impairs HDAC3's interaction with casein kinase 2 (CK2), resulting in decreased HDAC3 phosphorylation. Collectively, this increases H3K27 acetylation at the RET promoter region, likely enhancing the transcription of RET, a receptor tyrosine kinase critical for cell survival. Although RET is transcriptionally increased, Cryba1 loss disrupts its protein maturation, causing immature RET protein accumulation. This triggers age‐dependent endoplasmic reticulum (ER) stress, potentially contributing to the pathogenesis of AMD. Interestingly, although Cryba1 is not identified as an AMD‐linked variant in current GWAS, its loss may be linked to AMD mechanisms. These findings underscore the potential of gene‐agnostic and epigenetic therapeutic strategies for treating AMD.

Host defense peptides represent an important component of innate immunity. In this work, we report the anticancer properties of a panel of hyper-charged wholly cationic antimicrobial dodecapeptides (CAPs) containing multiple canonical forms of lysine and arginine residues. These CAPs displayed excellent bactericidal activities against a broad range of pathogenic bacteria by dissipating the cytoplasmic membrane potential. Specifically, we identified two CAPs, named HC3 and HC5, that effectively killed a significant number of retinoblastoma (WERI-Rb1) cells (p ≤ 0.01). These two CAPs caused the shrinkage of WERI-Rb1 tumor spheroids (p ≤ 0.01), induced intrinsic apoptosis in WERI-Rb1 cells via activation of caspase 9 and caspase 3, cleaved the PARP protein, and triggered off the phosphorylation of p53 and γH2A.X. Combining HC3 or HC5 with the standard chemotherapeutic drug topotecan showed synergistic anti-cancer activities. Overall, these results suggest that HC3 and HC5 can be exploited as potential therapeutic agents in retinoblastoma as monotherapy or as adjunctive therapy to enhance the effectiveness of currently used treatment modalities.