Knockdown of NRMT enhances sensitivity of retinoblastoma cells to cisplatin through upregulation of the CENPA/Myc/Bcl2 axis

Chemotherapy resistance of tumor cells causes failure in anti-tumor therapies. Recently, N-terminal regulator of chromatin condensation 1 methyltransferase (NRMT) is abnormally expressed in different cancers. Hence, we speculate that NRMT may pay a crucial role in the development of chemosensitivity in retinoblastoma. We characterized the upregulation of NRMT in the developed cisplatin (CDDP)-resistant retinoblastoma cell line relative to parental cells. Loss-of-function experiments demonstrated that NRMT silencing enhanced chemosensitivity of retinoblastoma cells to CDDP. Next, NRMT was identified to enrich histone-H3 lysine 4 trimethylation in the promoter of centromere protein A (CENPA) by chromatin immunoprecipitation assay. Rescue experiments suggested that CENPA reduced chemosensitivity by increasing the viability and proliferation and reducing apoptosis of CDDP-resistant retinoblastoma cells, which was reversed by NRMT. Subsequently, CENPA was witnessed to induce the transcription of Myc and to elevate the expression of B cell lymphoma-2. At last, in vivo experiments confirmed the promotive effect of NRMT knockdown on chemosensitivity of retinoblastoma cells to CDDP in tumor-bearing mice. Taken together, NRMT is an inhibitor of chemosensitivity in retinoblastoma. Those findings shed new light on NRMT-targeted therapies for retinoblastoma.

Anti-Proliferative Effect of Hydroethanolic Leaf Extract of Citrullus colocynthis (L) on Retinoblastoma Cell Line

Introduction: Citrullus colocynthis has many pharmacological, biological, and therapeutic properties making it a very important medicinal plant. The cucurbitacin produced/derived from the plant play an important role in anticancer activities. The retinoblastoma Y-79 cell lines are studied in attachment culture. A proper study of these cells can pave the way for control of its proliferative property. Cell viability was assayed using a modified colorimetric technique that is based on the ability of the live cells to convert MTT, a tetrazolium compound into purple formazan crystals. There was an effect on the proliferation and gene expressions of the retinoblastoma Y-79 cell line. Bioactive extracts of these plants are being majorly used as a potential chemopreventive element as an alternative approach for cancer progression management. Materials and Methods: Human retinoblastoma cell line (Y-79)cell line was purchased from the National Centre for Cell Sciences (NCCS), Pune, India. Cell viability was assayed using a modified colorimetric technique that is based on the ability of live cells to convert MTT. Results: The experimental study showed antiproliferative effects against the retinoblastoma Y-79 cells. The experimental study showed the effect on cell viability, Bcl2 mRNA expression and BclxL mRNA expression in Y-79 cells. Conclusion: The hydroethanolic leaf extract obtained from the Citrullus colocynthis exhibited an antiproliferative effect on the retinoblastoma Y-79 cell line by affecting the expression of the Bcl2 mRNA and BclxL mRNA and hindering the cell viability.

Single-cell transcriptome profiling reveals intratumoural heterogeneity and malignant progression in retinoblastoma

Retinoblastoma is a childhood retinal tumour that is the most common primary malignant intraocular tumour. However, it has been challenging to identify the cell types associated with genetic complexity. Here, we performed single-cell RNA sequencing on 14,739 cells from two retinoblastoma samples to delineate the heterogeneity and the underlying mechanism of retinoblastoma progression. Using a multiresolution network-based analysis, we identified two major cell types in human retinoblastoma. Cell trajectory analysis yielded a total of 5 cell states organized into two main branches, and the cell cycle-associated cone precursors were the cells of origin of retinoblastoma that were required for initiating the differentiation and malignancy process of retinoblastoma. Tumour cells differentiation reprogramming trajectory analysis revealed that cell-type components of multiple tumour-related pathways and predominantly expressed UBE2C were associated with an activation state in the malignant progression of the tumour, providing a potential novel “switch gene” marker during early critical stages in human retinoblastoma development. Thus, our findings improve our current understanding of the mechanism of retinoblastoma progression and are potentially valuable in providing novel prognostic markers for retinoblastoma.

Poly ADP Ribose Polymerase Inhibitor Olaparib Targeting Microhomology End Joining in Retinoblastoma Protein Defective Cancer: Analysis of the Retinoblastoma Cell-Killing Effects by Olaparib after Inducing Double-Strand Breaks

Retinoblastoma is the most common intraocular cancer in childhood. Loss of function in both copies of the RB1 gene is the causal mutation of retinoblastoma. Current treatment for retinoblastoma includes the use of chemotherapeutic agents, such as the DNA damaging agent etoposide, which is a topoisomerase II poison that mainly generates DNA double-strand breaks (DSBs) and genome instability. Unfaithful repairing of DSBs could lead to secondary cancers and serious side effects. Previously, we found that RB knocked-down mammalian cells depend on a highly mutagenic pathway, the micro-homology mediated end joining (MMEJ) pathway, to repair DSBs. Poly ADP ribose polymerase 1 (PARP1) is a major protein in promoting the MMEJ pathway. In this study, we explored the effects of olaparib, a PARP inhibitor, in killing retinoblastoma cells. Retinoblastoma cell line Y79 and primary retinoblastoma cells expressed the cone-rod homeobox protein (CRX), a photoreceptor-specific marker. No detectable RB expression was found in these cells. The co-treatment of olaparib and etoposide led to enhanced cell death in both the Y79 cells and the primary retinoblastoma cells. Our results demonstrated the killing effects in retinoblastoma cells by PARP inhibitor olaparib after inducing DNA double-strand breaks. The use of olaparib in combination with etoposide could improve the cell-killing effects. Thus, lower dosages of etoposide can be used to treat retinoblastoma, which would potentially lead to a lower level of DSBs and a relatively more stable genome.

HELZ2 Promotes K63-Linked Polyubiquitination of c-Myc to Induce Retinoblastoma Tumorigenesis

Retinoblastoma is a rare ocular tumor in children that originates in the retina. Several core transcriptional regulators maintain the expansion of retinoblastoma tumors, including c-Myc. Here, we demonstrated that Helicase with zinc finger domain 2 (HELZ2) promoted retinoblastoma tumorigenesis by targeting c-Myc. HELZ2-deficient inhibited retinoblastoma cell proliferation, whereas overexpression of HELZ2 promoted retinoblastoma cell proliferation. In addition, high levels of HELZ2 promoted xenograft retinoblastoma tumorigenesis and inhibited animal survival. Mechanistically, HELZ2 interacted with c-Myc and promoted its K63-linked polyubiquitination. We indicated that HELZ2 promoted the interaction between E3 ubiquitin ligase HUWE1 and c-Myc, and HELZ2-mediated K63-linked polyubiquitination and activation of c-Myc were dependent on HUWE1. Taken together, HELZ2 plays a critical role in the regulation of retinoblastoma tumorigenesis by enhancing the activity of c-Myc.

The Synergistic Cytotoxic and Apoptotic Effect of Resveratrol and Naringenin on Y79 Retinoblastoma Cell Line

Background: Resveratrol is a phenolic natural product which is found in red grapes also in Japanese knotweed root (Polygonum cuspidatum). Naringenin is one of the flavonoid compounds found in landing grape and other citrus fruits. Both agents exert antioxidant and anti-inflammatory properties. Objective: In this study, we investigated the effect of Resveratrol and Naringenin in an in vitro model of retinoblastoma of the eye. Method: XTT and trypan blue assays used to evaluate the anti-proliferative/cytotixic effect of resveratrol and naringenin in Y79 cells. By the aid of AnnexinV/PI flow cytometry the kind of cell death investigated. To asses important gene expression level at mRNA level involve in apoptosis, Real-time PCR utilized. Results: Naringenin and resveratrol significantly decreased proliferation and stimulated cell death (mostly apoptosis) in Y79 cells at 50 and 100 (μg/ml) after 24 and 48 hours. More cytotoxic effect observed after 48 hours. Furthermore expression level of Bax and Bcl2 mRNAs altered significantly in all samples treated with 50 (μg/ml) of naringenin, resveratrol, or simultaneously with both. P21 mRNAs expression altered in all mentioned samples except those treated with 50 (μg/ml) of resveratrol. Results: Naringenin and resveratrol significantly decreased proliferation and stimulated cell death (mostly apoptosis) in Y79 cells at 50 and 100 (μg/ml) after 24 and 48 hours. More cytotoxic effect observed after 48 hours. Furthermore expression level of Bax and Bcl2 mRNAs altered significantly in all samples treated with 50 (μg/ml) of naringenin, resveratrol, or simultaneously with both. P21 mRNAs expression altered in all mentioned samples except those treated with 50 (μg/ml) of resveratrol. Conclusion: Based on the results, it can be concluded that resveratrol and naringenin can decrease cell viability in retinoblastoma cells in an in vitro dose/time-dependent manner. Albeit more studies needed to shed the light on the mechanism of action, our data reveals a potential synergistic cytotoxic effect of naringenin and resveratrol on Y79 cells in 48 hours.