Hypoxic tumor microenvironment in advanced retinoblastoma

The Traces of Dysregulated lncRNAs-Associated ceRNA Axes in Retinoblastoma: A Systematic Scope Review

PURPOSE

Long non-coding RNAs are an essential component of competing endogenous RNA regulatory axes and play their role by sponging microRNAs and interfering with the regulation of gene expression. Because of the broadness of competing endogenous RNA interaction networks, they may help investigate treatment targets in complicated disorders.

METHODS

This study performed a systematic scoping review to assess verified loops of competing endogenous RNAs in retinoblastoma, emphasizing the competing endogenous RNAs axis related to long non-coding RNAs. We used a six-stage approach framework and the PRISMA guidelines. A systematic search of seven databases was done to locate suitable papers published before February 2022. Two reviewers worked independently to screen articles and collect data.

RESULTS

Out of 363 records, fifty-one articles met the inclusion criteria, and sixty-three axes were identified in desired articles. The majority of the research reported several long non-coding RNAs that were experimentally verified to act as competing endogenous RNAs in retinoblastoma: XIST/NEAT1/MALAT1/SNHG16/KCNQ1OT1, respectively. At the same time, around half of the studies investigated unique long non-coding RNAs.

CONCLUSIONS

Understanding the many features of this regulatory system may aid in elucidating the unknown etiology of Retinoblastoma and providing novel molecular targets for therapeutic and clinical applications.

Deciphering metabolic heterogeneity in retinoblastoma unravels the role of monocarboxylate transporter 1 in tumor progression

BACKGROUND

Tumors exhibit metabolic heterogeneity, influencing cancer progression. However, understanding metabolic diversity in retinoblastoma (RB), the primary intraocular malignancy in children, remains limited.

METHODS

The metabolic landscape of RB was constructed based on single-cell transcriptomic sequencing from 11 RB and 5 retina samples. Various analyses were conducted, including assessing overall metabolic activity, metabolic heterogeneity, and the correlation between hypoxia and metabolic pathways. Additionally, the expression pattern of the monocarboxylate transporter (MCT) family in different cell clusters was examined. Validation assays of MCT1 expression and function in RB cell lines were performed. The therapeutic potential of targeting MCT1 was evaluated using an orthotopic xenograft model. A cohort of 47 RB patients was analyzed to evaluate the relationship between MCT1 expression and tumor invasion.

RESULTS

Distinct metabolic patterns in RB cells, notably increased glycolysis, were identified. This metabolic heterogeneity correlated closely with hypoxia. MCT1 emerged as the primary monocarboxylate transporter in RB cells. Disrupting MCT1 altered cell viability and energy metabolism. In vivo studies using the MCT1 inhibitor AZD3965 effectively suppressed RB tumor growth. Additionally, a correlation between MCT1 expression and optic nerve invasion in RB samples suggested prognostic implications.

CONCLUSIONS

This study enhances our understanding of RB metabolic characteristics at the single-cell level, highlighting the significance of MCT1 in RB pathogenesis. Targeting MCT1 holds promise as a therapeutic strategy for combating RB, with potential prognostic implications.

Therapeutic Strategies for RB1-Deficient Cancers: Intersecting Gene Regulation and Targeted Therapy

The retinoblastoma (RB) transcriptional corepressor 1 (RB1) is a critical tumor suppressor gene, governing diverse cellular processes implicated in cancer biology. Dysregulation or deletion in RB1 contributes to the development and progression of various cancers, making it a prime target for therapeutic intervention. RB1's canonical function in cell cycle control and DNA repair mechanisms underscores its significance in restraining aberrant cell growth and maintaining genomic stability. Understanding the complex interplay between RB1 and cellular pathways is beneficial to fully elucidate its tumor-suppressive role across different cancer types and for therapeutic development. As a result, investigating vulnerabilities arising from RB1 deletion-associated mechanisms offers promising avenues for targeted therapy. Recently, several findings highlighted multiple methods as a promising strategy for combating tumor growth driven by RB1 loss, offering potential clinical benefits in various cancer types. This review summarizes the multifaceted role of RB1 in cancer biology and its implications for targeted therapy.

MDM2 promotes cancer cell survival through regulating the expression of HIF-1α and pVHL in retinoblastoma

Hypoxia is an important tumor feature and hypoxia-inducible factor 1 (HIF-1) is a master regulator of cell response to hypoxia. Mouse double minute 2 homolog (MDM2) promotes cancer cell survival in retinoblastoma (RB), with the underlying mechanism remaining elusive. In this study, we investigated the role of MDM2 and its relation to HIF-1α in RB. Expression analysis on primary human RB samples showed that MDM2 expression was positively correlated with that of HIF-1α while negatively correlated with von Hippel-Lindau protein (pVHL), the regulator of HIF-1α. In agreement, RB cells with MDM2 overexpression showed increased expression of HIF-1α and decreased expression of pVHL, while cells with MDM2 siRNA knockdown or MDM2-specific inhibitor showed the opposite effect under hypoxia. Further immuno-precipitation analysis revealed that MDM2 could directly interact with pVHL and promotes its ubiquitination and degradation, which consequently led to the increase of HIF-1α. Inhibition of MDM2 and/or HIF-1α with specific inhibitors induced RB cell death and decreased the stem cell properties of primary RB cells. Taken together, our study has shown that MDM2 promotes RB survival through regulating the expression of pVHL and HIF-1α, and targeting MDM2 and/or HIF-1α represents a potential effective approach for RB treatment.

RB1 loss triggers dependence on ESRRG in retinoblastoma

Retinoblastoma (Rb) is a deadly childhood eye cancer that is classically initiated by inactivation of the RB1 tumor suppressor. Clinical management continues to rely on nonspecific chemotherapeutic agents that are associated with treatment resistance and toxicity. Here, we analyzed 103 whole exomes, 20 whole transcriptomes, 5 single-cell transcriptomes, and 4 whole genomes from primary Rb tumors to identify previously unknown Rb dependencies. Several recurrent genomic aberrations implicate estrogen-related receptor gamma (ESRRG) in Rb pathogenesis. RB1 directly interacts with and inhibits ESRRG, and RB1 loss uncouples ESRRG from negative regulation. ESRRG regulates genes involved in retinogenesis and oxygen metabolism in Rb cells. ESRRG is preferentially expressed in hypoxic Rb cells in vivo. Depletion or inhibition of ESRRG causes marked Rb cell death, which is exacerbated in hypoxia. These findings reveal a previously unidentified dependency of Rb cells on ESRRG, and they implicate ESRRG as a potential therapeutic vulnerability in Rb.

Retinoblastoma Is Characterized by a Cold, CD8+ Cell Poor, PD-L1- Microenvironment, Which Turns Into Hot, CD8+ Cell Rich, PD-L1+ After Chemotherapy

Purpose

To investigate the impact of chemotherapy (CHT) on human retinoblastoma (RB) tumor microenvironment (TME).

Cases and Methods

Ninety-four RBs were studied, including 44 primary RBs treated by upfront surgery (Group 1) and 50 primary RBs enucleated after CHT (CHT), either intra-arterial (IAC; Group 2, 33 cases) or systemic (S-CHT; Group 3, 17 cases). Conventional and multiplexed immunohistochemistry were performed to make quantitative comparisons among the three groups, for the following parameters: tumor-infiltrating inflammatory cells (TI-ICs); programmed cell death protein 1 (PD-1) positive TI-ICs; Ki67 proliferation index; gliosis; PD-1 ligand (PD-L1) protein expression; vessel number. We also correlated these TME factors with the presence of histological high-risk factors (HHRF+) and RB anaplasia grade (AG).

Results

After CHT, a decrease in both RB burden and Ki67 positivity was observed. In parallel, most subsets of TI-ICs, PD-1+ TI-ICs, gliosis, and PD-L1 protein expression significantly increased (P < 0.001, P = 0.02, P < 0.001, respectively). Vessel number did not significantly vary. Age, HHRFs+ and AG were significantly different between primary and chemoreduced RBs (P < 0.001, P = 0.006, P = 0.001, respectively) and were correlated with most TME factors.

Conclusions

CHT modulates host antitumor immunity by reorienting the RB TME from anergic into an active, CD8+, PD-L1+ hot state. Furthermore, some clinicopathological characteristics of RB correlate with several factors of TME. Our study adds data in favor of the possibility of a new therapeutic scenario in human RB.

AS1411-functionalized delivery nanosystems for targeted cancer therapy

Nucleolin (NCL) is a multifunctional nucleolar phosphoprotein harboring critical roles in cells such as cell proliferation, survival, and growth. The dysregulation and overexpression of NCL are related to various pathologic and oncological indications. These characteristics of NCL make it an ideal target for the treatment of various cancers. AS1411 is a synthetic quadruplex-forming nuclease-resistant DNA oligonucleotide aptamer which shows a considerably high affinity for NCL, therefore, being capable of inducing growth inhibition in a variety of tumor cells. The high affinity and specificity of AS1411 towards NCL make it a suitable targeting tool, which can be used for the functionalization of therapeutic payloaddelivery nanosystems to selectively target tumor cells. This review explores the advances in NCL-targeting cancer therapy through AS1411-functionalized delivery nanosystems for the selective delivery of a broad spectrum of therapeutic agents.

A decision process for drug discovery in retinoblastoma

Intraocular retinoblastoma treatment has changed radically over the last decade, leading to a notable improvement in ocular survival. However, eyes that relapse remain difficult to treat, as few alternative active drugs are available. More challenging is the scenario of central nervous system (CNS) metastasis, in which almost no advancements have been made. Both clinical scenarios represent an urgent need for new drugs. Using an integrated multidisciplinary approach, we developed a decision process for prioritizing drug selection for local (intravitreal [IVi], intrathecal/intraventricular [IT/IVt]), systemic, or intra-arterial chemotherapy (IAC) treatment by means of high-throughput pharmacological screening of primary cells from two patients with intraocular tumor and CNS metastasis and a thorough database search to identify clinical and biopharmaceutical data. This process identified 169 compounds to be cytotoxic; only 8 are FDA-approved, lack serious toxicities and available for IVi administration. Four of these agents could also be delivered by IT/IVt. Twelve FDA-approved drugs were identified for systemic delivery as they are able to cross the blood-brain barrier and lack serious adverse events; four drugs are of oral usage and six compounds that lack vesicant or neurotoxicity could be delivered by IAC. We also identified promising compounds in preliminary phases of drug development including inhibitors of survivin, antiapoptotic Bcl-2 family proteins, methyltransferase, and kinesin proteins. This systematic approach may be applied more broadly to prioritize drugs to be repurposed or to identify novel hits for use in retinoblastoma treatment.

lncRNA KCNQ1OT1 promotes the proliferation, migration and invasion of retinoblastoma cells by upregulating HIF-1α via sponging miR-153-3p

It is reported that lncRNA KCNQ1 opposite strand/antisense transcript 1 (KCNQ1OT1) is oncogenic in many cancers. This work aimed at probing into its expression and biological functions in retinoblastoma (RB) as well as its regulatory effects on miR-153-3p and hypoxia-inducible factor-1α (HIF-1α). In our study, RB samples in pair were collected, and quantitative real-time PCR (qRT-PCR) was employed for examining the expression levels of KCNQ1OT1, miR-153-3p and HIF-1α. KCNQ1OT1 short hairpin RNAs were transfected into SO-Rb50 and HXO-RB44 cell to inhibit the expression of KCNQ1OT1. The proliferative activity, colony formation ability and apoptosis were examined through cell counting kit-8 assay, colony formation assays, Transwell assay and flow cytometry, respectively. qRT-PCR and western blot analysis were used for analyzing the changes of miR-153-3p and HIF-1α induced by KCNQ1OT1. The regulatory relationships between miR-153-3p and KCNQ1OT1, miR-153-3p and HIF-1α were examined by dual luciferase reporter gene assay and RNA-binding protein immunoprecipitation assay. The results of our study showed that KCNQ1OT1 expression was markedly enhanced in RB tissue samples, and KCNQ1OT1 knockdown had an inhibitory effect on the proliferation, migration, invasion and viability of RB cells. There were two validated binding sties between KCNQ1OT1 and miR-153-3p, and KCNQ1OT1 negatively regulated the expression of miR-153-3p in RB cells. HIF-1α was a target gene of miR-153-3p, and could be positively regulated by KCNQ1OT1. In conclusion, our study indicates that KCNQ1OT1 can increase the malignancy of RB cells via regulating miR-153-3p/HIF-1α axis.

LncRNA TMPO-AS1 up-regulates the expression of HIF-1α and promotes the malignant phenotypes of retinoblastoma cells via sponging miR-199a-5p

BACKGROUND

Long non-coding RNA (lncRNA) TMPO antisense RNA 1 (TMPO-AS1) is reported to be oncogenic in prostate cancer and lung cancer. This study aims to investigate the expression and biological function of it in retinoblastoma (RB), and explore its regulatory role for miR-199a-5p and hypoxia-inducible factor-1α (HIF-1α).

METHODS

Paired RB samples were collected, and the expression levels of TMPO-AS1, miR-199a-5p and HIF-1α were examined by quantitative real-time polymerase chain reaction (qRT-PCR); TMPO-AS1 overexpressing plasmids and TMPO-AS1 shRNA were transfected into HXO-RB44 and SO-Rb50 cell lines respectively, and then proliferation, migration and invasion of RB cells were detected by CCK-8 assay and Transwell method. qRT-PCR and western blot were used to analyze the regulatory function of TMPO-AS1 on miR-199a-5p and HIF-1α; luciferase reporter gene assay was used to determine the regulatory relationship between miR-199a-5p and TMPO-AS1.

RESULTS

TMPO-AS1 was significantly up-regulated in cancerous tissues of RB samples (relatively expression: 2.97 vs 3.93, p < 0.001), negatively correlated with miR-199a-5p (r=-0.4813, p < 0.01). There was one binding site on TMPO-AS1 for miR-199a-5p. After transfection of TMPO-AS1 shRNAs into RB cells, the proliferation, migration and invasion of cancer cells was significantly inhibited, while TMPO-AS1 had opposite effects; TMPO-AS1 was also demonstrated to regulate the expression of HIF-1α on both mRNA and protein levels via negatively regulating miR-199a-5p.

CONCLUSION

TMPO-AS1 is abnormally up-regulated in RB tissues, and it can modulate the proliferation and migration of RB cells. It has the potential to be the "ceRNA" to regulate HIF-1α expression by sponging miR-199a-5p.

Non-Coding RNAs in Retinoblastoma

Retinoblastoma (Rb) is the most common ocular pediatric malignancy that arises from the retina and is caused by a mutation of the two alleles of the tumor suppressor gene, RB1. Although early detection provides the opportunity of controlling the primary tumor with effective therapies, metastatic activity is fatal. Non-coding RNAs (ncRNAs) have emerged as important modifiers of a plethora of biological mechanisms including those involved in cancer. They are classified into short and long ncRNAs according to their length. Deregulation of all these molecules has also been shown to play a critical role in Rb pathogenesis and progression. It is believed that ncRNAs can provide new insights into novel regulatory mechanisms associated with clinical pathological characteristics, facilitating the development of therapeutic alternatives for the treatment of Rb. In this review, we describe a variety of ncRNAs, which capable of regulating the most likely candidate genes involved in the tumorigenesis of Rb, could prove useful in analyzing different aspects of this cancer.

Tumour expressions of hypoxic markers predict the response to neo-adjuvant chemotherapy in children with inoperable rhabdomyosarcoma

Objective: The study was to assess whether tumour expressions of hypoxia-inducible factor (HIF)-1α, glucose transporter (GLUT)-1, carbonic anhydrase (CA) IX and vascular endothelial growth factor (VEGF) predict response to neo-adjuvant chemotherapy (naCHT) in children with inoperable rhabdomyosarcoma (RMS). Methods: Immunohistochemical expressions of hypoxia markers were determined semi-quantitatively in tumour tissue microarray of 46 patients with embryonal RMS (RME) and 20 with alveolar (RMA), treated with CWS protocols (1992-2013). Results: In paediatric RME, response to naCHT was influenced significantly by tumour expression of CA IX and GLUT-1. Patients with RMA with low expressions of analysed markers responded well to naCHT, while all poor-responders expressed highly hypoxia markers. Only 5.88% of RMA and 11.11% of RME tumours did not express any of the proteins. In both RME and RMA subgroups, most poor-responders demonstrated simultaneous high expression of ≥3 markers, while most patients expressing ≤2 markers responded well to naCHT. In the whole cohort, co-expression of ≥3 markers, was the only independent factor predicting poor-response to chemotherapy (odds ratio 14.706; 95% CI 1.72-125.75; p = 0.014). Conclusions: Immunohistochemical expression pattern of four endogenous markers of hypoxia, in tumour tissue at diagnosis, emerges as a promising tool to predict response to naCHT in children with inoperable RMS.

Characterization of etoposide- and cisplatin-chemoresistant retinoblastoma cell lines

Retinoblastoma (RB) is the most common malignant intraocular tumor in early childhood. Imminent chemotherapy resistance diminishes the clinical-therapeutic options and emphasizes the necessity for new therapeutic approaches. The present study aimed at characterizing and comparing etoposide and cisplatin-resistant human RB cell lines with regard to changes in proliferation and apoptosis levels, anchorage independent growth behavior in vitro as well as tumor formation capacity in vivo. The proliferation rates were significantly increased in the etoposide-resistant RB cell lines Y-79, WERI-Rb1 and RB-355 reflecting significantly higher growth kinetics compared to the parental controls. In line with these findings in in vivo chicken chorioallantoic (CAM) assays, etoposide-resistant cell lines generated significantly increased numbers of tumors with higher tumor weights compared to their parental counterparts. In contrast to etoposide, the cisplatin-resistant RB cell lines Y-79, WERI-Rb1 and RB-355 displayed significantly increased apoptosis rates and reduced proliferation rates resulting in significantly decreased growth kinetics. Tumor formation capacity of cisplatin-resistant cell lines did not significantly change, and in comparison with parental controls cisplatin-resistant Y-79 cells displayed significantly reduced tumor weight. Soft agarose assays indicated that anchorage-independent growth of all chemotherapy-resistant cell lines analyzed was significantly decreased. Summarizing, one can state that etoposide-resistant RB cells behave more aggressively than the tumor cells of origin and potentially represent a risk factor for local relapse, while cisplatin-resistant cells show a significantly decreased tumorigenic potential.

MicroRNA-320 regulates autophagy in retinoblastoma by targeting hypoxia inducible factor-1α

Retinoblastoma (RB) is the most common malignancy in children. Due to refractory mechanisms of chemoresistance and the toxicity of chemotherapies, novel therapies for RB treatment are urgently required. MicroRNA-320 (miR-320) is believed to be associated with the tumorigenesis of RB, although the mechanism remains unclear. Considering the hypoxic intratumoral region, the roles of miR-320 and hypoxia inducible factor-1α (HIF-1α) in the regulation of autophagy were investigated in 30 human RB samples and WERI-RB1 cells. The results demonstrated that HIF-1α was the downstream target of miR-320, and decreased miRNA-320 or HIF-1α lead to the inhibition of autophagy in WERI-RB1 cells. Compared with WERI-RB1 cells that were not transfected, silenced HIF-1α caused a 1.41-fold increase (P<0.01) in p62, a 2.71-fold decrease of Beclin1, and inhibited miRNA-320. Silenced HIF-1α also resulted in 7.29- and 7.43-fold increases in phosphorylated-mechanistic target of rapamycin (mTOR) and mTOR, respectively. In conclusion, the present results suggest that miRNA-320 may regulate the development of autophagy by targeting HIF-1α and autophagy-related proteins in RB under hypoxic conditions.

Hypoxia inhibits growth, proliferation, and increases response to chemotherapy in retinoblastoma cells

Retinoblastoma is a malignant tumor of the retina and the most frequent intraocular cancer in children. Low oxygen tension (hypoxia) is a common phenomenon in advanced retinoblastomas, but its biological effect on retinoblastoma growth is not clearly understood. Here we studied how hypoxia altered retinoblastoma gene expression and modulated growth and response to chemotherapy. The hypoxic marker lysyl oxidase (LOX) was expressed in 8 of 12 human retinoblastomas analyzed by immunohistochemistry, suggesting that a hypoxic microenvironment is present in up to two thirds of the cases. WERI Rb1 and Y79 retinoblastoma lines were exposed to 1% or 5% pO₂, cobalt chloride (CoCl₂), or to normoxia (21% pO₂) for up to 8 days. Both 1% and 5% pO₂ inhibited growth of both lines by more than 50%. Proliferation was reduced by 25-50% when retinoblastoma cells were exposed to 1% vs 21% pO₂, as determined by Ki67 assay. Surprisingly, Melphalan, Carboplatin, and Etoposide produced greater reduction in growth and survival of hypoxic cells than normoxic ones. Gene expression profile analysis of both lines, exposed for 48 h to 1%, 5%, or 21% pO₂, showed that glycolysis and glucose transport were the most up-regulated pathways, whereas oxidative phosphorylation was the most down-regulated pathway in hypoxia as compared to normoxia. These data support a role for hypoxia in suppressing growth, proliferation, and enhancing response of retinoblastoma cells to chemotherapy, possibly by impairing energy production through activation of glycolysis and inhibition of mitochondrial respiration. Targeting glucose metabolism or enhancing delivery of chemotherapeutic agents to hypoxic regions may improve treatment of advanced retinoblastomas.

Overexpression of pyruvate dehydrogenase kinase 1 in retinoblastoma: A potential therapeutic opportunity for targeting vitreous seeds and hypoxic regions

Pyruvate dehydrogenase kinase 1 (PDK1), a key enzyme implicated in metabolic reprogramming of tumors, is induced in several tumors including glioblastoma, breast cancer and melanoma. However, the role played by PDK1 is not studied in retinoblastoma (RB). In this study, we have evaluated the expression of PDK1 in RB clinical samples, and studied its inhibition as a strategy to decrease cell growth and migration. We show that PDK1 is specifically overexpressed in RB patient samples especially in vitreous seeds and hypoxic regions and cell lines compared to control retina using immunohistochemistry and real-time PCR. Our results further demonstrate that inhibition of PDK1 using small molecule inhibitors dichloroacetic acid (DCA) and dichloroacetophenone (DAP) resulted in reduced cell growth and increased apoptosis. We also confirm that combination treatment of DCA with chemotherapeutic agent carboplatin further enhanced the therapeutic efficacy compared to single drug treatment. In addition, we observed changes in glucose uptake, lactate and reactive oxygen species (ROS) levels as well as decreased cell migration in response to PDK1 inhibition. Additionally, we show that DCA treatment led to inhibition of PI3K/Akt pathway and reduction in PDK1 protein levels. Overall, our data suggest that targeting PDK1 could be a novel therapeutic strategy for RB.

A Study of Gene Expression of Survivin, its Antiapoptotic Variants, and Targeting Survivin In Vitro for Therapy in Retinoblastoma

Apoptosis is a natural process regulated by apoptotic and antiapoptotic molecules. We investigated mRNA expression of survivin and its splice variants, along with B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X (Bax), in a cohort of 20 retinoblastoma (RB) tumors by real-time polymerase chain reaction. We hypothesized a correlation between the Bcl-2/Bax and survivin splice variants and also that expression of these would be associated with clinicopathologic features of tumors. The Bcl-2 expression was significantly higher (P<0.001) in RB, and Bcl-2/Bax ratio was remarkably higher in poorly differentiated tumors. A statistically significant higher expression of Survivin-WT (wild type) compared with its variant Survivin-2β (P<0.05) was observed. Bcl-2 did not exhibit positive correlation with any of the survivin variants except Survivin-2β, whereas Bax exhibited significant (P<0.05) correlation with the variants. Thus, it could be suggested that a superior player out of a likely interaction between the variants and Bcl-2/Bax uses its activity for the progression of RB. Silencing of Survivin-WT in the Y79 cell line was studied by siRNA technology and cell-permeable dominant negative survivin (SurR9-C84A). siRNA showed higher proapoptotic effects and increased caspase 3/7 activity in Y79 cells. Effective internalization of SurR9-C84A in Y79 cells induced cytotoxic effects. Thus, the current study confirms survivin as a promising target for therapy.

Targeting HSP90/Survivin using a cell permeable structure based peptido-mimetic shepherdin in retinoblastoma

BACKGROUND

Retinoblastoma (RB) is a childhood retinal malignancy. Effective therapeutic strategies are still being investigated in RB disease management. Here, the anti-cancer effect of shepherdin, a peptido-mimetic inhibiting heat shock protein (HSP90)-Survivin interaction has been analyzed.

METHODS

We analyzed HSP (HSP70/90) and Survivin protein expressions by immunohistochemistry (29 archival tumors), qRT-PCR, FACS and Western analysis (10 un-fixed RB tumors). We also analyzed cellular cytotoxicity and anti-proliferative effect in peptide treated RB cells (Y79, Weri Rb1) and MIO-M1 cells.

RESULTS

Heterogeneous expressions of HSP70/90 and Survivin with a significant association between HSP70 and HSP90 (r(2) = 0.59, p = 0.001) was observed. In RB cells, anti-tumor effects were detected with 0.42 μg/ml of shepherdin at 4 h s of serum starvation. Decreased Survivin, Bcl2, MMP-2 activity with increased Bax, Bim, and Caspase-9 protein expressions were noticed. No significant changes were observed in shepherdin treated non-neoplastic MIO-M1, nor in scramble-peptide treated RB cells.

CONCLUSION

The presence of HSPs (HSP70/90) and Survivin reveals multiple cellular mechanisms adopted by RB cells during cancer progression. Serum starvation induced HSP90 whose interactions with Survivin were specifically inhibited by shepherdin. The associated molecular shuffling has been reported. These findings strongly implicate the potential of targeting HSP90-Survivin interaction as an adjuvant therapy in RB management.

Targeting Survivin Enhances Chemosensitivity in Retinoblastoma Cells and Orthotopic Tumors

Treatments for retinoblastoma (Rb) vary depending on the size and location of the intraocular lesions and include chemotherapy and radiation therapy. We examined whether agents used to treat Rb induce a pro-survival phenotype associated with increased expression of survivin, a member of the inhibitor of apoptosis family of proteins. We document that exposure to carboplatin, topotecan or radiation resulted in elevated expression of survivin in two human Rb cell lines but not in normal retinal pigmented epithelial (RPE) cells. Cellular levels of survivin were attenuated in Rb cells exposed to an imidazolium-based survivin suppressant, Sepantronium bromide (YM155). Protein expression patterns of survivin in RPE cells were not altered following treatment protocols involving exposure to YM155. Including YM155 with chemotherapy or radiation increased levels of apoptosis in Rb cells but not in RPE cells. Intraocular luciferase expressing Rb tumors were generated from the Rb cell lines and used to evaluate the effects of carboplatin and YM155 on in-vivo survivin expression and tumor growth. Carboplatin induced expression of survivin while carboplatin combined with YM155 reduced survivin expression in tumor bearing eyes. The combination protocol was also most effective in reducing the rate of tumor regrowth. These results indicate that targeted inhibition of the anti-apoptotic protein survivin provides a therapeutic advantage for Rb cells and tumors treated with chemotherapy.

Targeting Cancer Cells Using LNA-Modified Aptamer-siRNA Chimeras

Aptamers are chimerized with drug or antisense oligos or nanoparticles to generate targeted therapeutics for cancer. Aptamer chimerized siRNA rescues nonspecific delivery and, thereby, enhances the availability of siRNA to target cells. EpCAM RNA aptamer (EpApt or Ep) has potential for siRNA chimerization due to its secondary structure. Stathmin and survivin proteins are reported to aid oncogenicity in retinoblastoma (RB), breast cancer and other cancers. Thus, chimerization of EpCAM Apt with siRNA against survivin and stathmin, respectively, was performed by incorporating Locked Nucleic Acid (LNA) modification. The LNA-modified chimeric aptamers were stable until 96 h and got internalized into RB, WERI-Rb1 and breast cancer, MDAMB453 cell lines. The constructs were studied using the recombinant dicer enzyme for the siRNA generation. Quantitative polymerase chain reaction and immunofluorescence by microscopic analysis of chimeras in vitro exhibited silencing of stathmin and survivin in the RB and breast cancer model. The chimeric constructs showed significant inhibition of cell proliferation of breast cancer cells. Thus, LNA-modified aptamer-based siRNA delivery aids in cell targeting and necessitates further studies in animal models.

Chimeric nucleolin aptamer with survivin DNAzyme for cancer cell targeted delivery

A chimeric aptamer-DNAzyme conjugate was generated for the first time using a nucleolin aptamer (NCL-APT) and survivin Dz (Sur_Dz) and exhibited the targeted killing of cancer cells. This proof of concept of using an aptamer for the delivery of DNAzyme can be applied to other cancer types to target survivin in cancer cells in a specific manner.

Hypoxia-induced miR-181b enhances angiogenesis of retinoblastoma cells by targeting PDCD10 and GATA6

Previous findings showed that miR-181b is upregulated under hypoxic conditions in retinoblastoma cells. Since hypoxia is a common feature of retinoblastoma that affects tumor progression as well as tumor therapy, in the present study, we investigated the regulatory mechanism of miR-181b under hypoxic conditions, and examined the role of miR-181b in retinoblastoma responses to hypoxia (chemoresistance and angiogenesis) and possible downstream genes. The level of hypoxia-inducible factor-1α (HIF-1α) and miR-181b was detected to examine the link between them. Tube formation and cell cytotoxicity assays were used to clarify the effects of miR-181b on hypoxic responses of retinoblastoma cells. Bioinformatics analysis was performed to predict potential targets of miR-181b and western blotting was used to verify these targets. The results showed a significantly increased expression of HIF-1α in hypoxia-treated retinoblastoma cells. Downregulation of HIF-1α using a small-interfering RNA (siRNA) knockdown technology did not decrease the expression of miR-181b. Through gain- and loss-of-function studies, miR-181b was demonstrated to significantly stimulate the ability of capillary tube formation of endothelial cells. Programmed cell death-10 (PDCD10) and GATA binding protein 6 (GATA6) were identified as the target genes of miR‑181b. To the best of our knowledge, results of the present study provide the first evidence that miR-181b was upregulated by hypoxia in retinoblastoma in an HIF-1α-independent manner. miR-181b increased tumor angiogenesis of retinoblastoma cells. Additionally, miR-181b exerts its angiogenic function, at least in part, by inhibiting PDCD10 and GATA6. Thus, it is a new potentially useful therapeutic target for retinoblastoma.

Hypermethylation of adenomatosis polyposis coli-2 and its tumor suppressor role in retinoblastoma

PURPOSE

Retinoblastoma (RB) is a progressive eye cancer of infancy and childhood. Hypermethylation, epigenetic silencing of genes is one of the key events in tumorigenesis. The purpose of this study is to investigate hypermethylation of adenomatosis polyposis coli homologue, APC-2 and possible interaction of APC-2 with Wnt signaling β-catenin protein in Retinoblastoma.

METHODOLOGY

Primary RB tumor samples and cell line were used for the study. DNA isolation, bisulfite conversion, methylation specific PCR and DNA sequencing analysis of PCR products were performed to identify CpG islands and methylation in primary RB tumor samples (n = 30). Chemical demethylation and retrieval of APC-2 expression was studied using 5-Azacytidine (5'-AZC). Flow cytometry, immunofluorescence, western blot were performed for APC-2 expression analysis in demethylated Y79 cells. Co-localization study was conducted to understand the interaction between APC-2 and β-catenin.

RESULTS

APC-2 gene was methylated and down regulated in primary RB tumors. We observed that 70% of RB tumors (21/30) showed positivity with APC-2 methylation. The RB Y79 cells after treatment with demethylating agent 5'-AZC retrieved APC-2 expression, which was confirmed by immunofluorescence and Western blot. Flow cytometry showed APC-2 expression of 29.22% in 5'-AZC treated cells. Co-localization study showed interaction of APC-2 and RB upregulated β-catenin in Y79 cells.

CONCLUSION

We report that APC-2 gene is hypermethylated in both RB tumor samples and Y79 cells. Reduced APC-2 lead to increased Wnt signaling pathway protein, β-catenin suggesting tumor suppressive role of APC-2 gene.

Inhibition of hypoxia inducible factor 1α by siRNA-induced apoptosis in human retinoblastoma cells

Hypoxia, which activates the hypoxia inducible factor 1α (HIF-1α), is an essential feature of retinoblastoma (RB) and contributes to poor prognosis and resistance to conventional therapy. In this study, the effect of HIF-1α knockdown by small interfering RNA (siRNA) on cell proliferation, apoptosis, and apoptotic pathways of human Y-79 RB cells was first investigated. Exposure to hypoxia induced the increased expression of HIF-1α both in mRNA and protein levels. Then, knockdown of HIF-1α by siRNAHIF-1α resulted in inhibition of cell proliferation and induced cell apoptosis in human Y-79 RB cells under both normoxic and hypoxic conditions, with hypoxic conditions being more sensitive. Furthermore, knockdown of HIF-1α could enhance hypoxia-induced slight increase of Bax/Bcl-2 ratio and activate caspase-9 and caspase-3. These results together indicated that suppression of HIF-1α expression may be a promising strategy for the treatment of human RB in the future.

Molecular Insights on Post-chemotherapy Retinoblastoma by Microarray Gene Expression Analysis

PURPOSE

Management of Retinoblastoma (RB), a pediatric ocular cancer is limited by drug-resistance and drug-dosage related side effects during chemotherapy. Molecular de-regulation in post-chemotherapy RB tumors was investigated.

MATERIALS AND METHODS

cDNA microarray analysis of two post-chemotherapy and one pre-chemotherapy RB tumor tissues was performed, followed by Principle Component Analysis, Gene ontology, Pathway Enrichment analysis and Biological Analysis Network (BAN) modeling. The drug modulation role of two significantly up-regulated genes (p≤0.05) - Ect2 (Epithelial-cell-transforming-sequence-2), and PRAME (preferentially-expressed-Antigen-in-Melanoma) was assessed by qRT-PCR, immunohistochemistry and cell viability assays.

RESULTS

Differential up-regulation of 1672 genes and down-regulation of 2538 genes was observed in RB tissues (relative to normal adult retina), while 1419 genes were commonly de-regulated between pre-chemotherapy and post- chemotherapy RB. Twenty one key gene ontology categories, pathways, biomarkers and phenotype groups harboring 250 differentially expressed genes were dys-regulated (EZH2, NCoR1, MYBL2, RB1, STAMN1, SYK, JAK1/2, STAT1/2, PLK2/4, BIRC5, LAMN1, Ect2, PRAME and ABCC4). Differential molecular expressions of PRAME and Ect2 in RB tumors with and without chemotherapy were analyzed. There was neither up- regulation of MRP1, nor any significant shift in chemotherapeutic IC50, in PRAME over-expressed versus non-transfected RB cells.

CONCLUSION

Cell cycle regulatory genes were dys-regulated post-chemotherapy. Ect2 gene was expressed in response to chemotherapy-induced stress. PRAME does not contribute to drug resistance in RB, yet its nuclear localization and BAN information, points to its possible regulatory role in RB.