Human Retinoblastoma Tissues Research Articles

Effects of long non-coding RNA MALAT1-targeting miR-570-3p and miR-34a on the invasion, proliferation, and apoptosis of human retinoblastoma cells

Purpose: To investigate the expression of lncRNA MALAT1-targeting miR-570-3p and miR-34a and its effects on the invasion, proliferation, and apoptosis of human retinoblastoma cells.
 Methods: MiR-34a, miR-570-3p, and IncRNA MALAT1 in a human normal retinal vascular endothelial cell line (ACBRI-181), human retinoblastoma cell line (SO-Rb50), human normal retinal tissue and human retinoblastoma tissue were determined. Luciferase assay was used to verify the targeting relationship between LncRNA MALAT1 and miR-570-3p and miR-34a. while cell invasion, cell apoptosis and cell proliferation were assessed by Transwell assay, flow cytometry, and tumor pellet-forming assay, respectively.
 Results: LncRNA MALAT1 in SO-Rb50 cell line and human retinoblastoma tissue line were significantly up-regulated, while the expression levels of miR-34a and miR-570-3p were significantly down-regulated (p < 0.05). Luciferase assay results showed that lncRNA MALAT1 targeted miR-570-3p and miR-34a. The invasion and proliferation of SO-Rb50 cells in the miR-570-3p inhibitor and miR-34a inhibitor groups were significantly increased, while the apoptosis of SO-Rb50 cells was significantly decreased (p < 0.05). However, the invasion and proliferation of SO-Rb50 cells in sh-MALAT1 group were significantly decreased, while apoptosis significantly increased. However, compared with sh-MALAT1 group alone, the invasion and proliferation of SO-Rb50 cells in co-transfected sh-MALAT1+miR-570-3p inhibitor + miR-34a inhibitor group w significantly increased, but apoptosis significantly decreased (p < 0.05).
 Conclusion: LncRNA MALAT1 negatively regulates miR-570-3p and miR-34a to promote the invasion and proliferation of human retinoblastoma SO-Rb50 cells and inhibit apoptosis. These findings may be of significance in developing suitable therapies for human retinoblastoma

GSDME Increases Chemotherapeutic Drug Sensitivity by Inducing Pyroptosis in Retinoblastoma Cells

Chemotherapy is an important part of retinoblastoma (RB) treatment. However, the development of drug resistance increases the likelihood of treatment failure. Therefore, increasing the sensitivity of chemotherapeutic drugs is very important. Recent research has explored the relationship between the expression level of gasdermin E (GSDME) and drug sensitivity in RB. Our study found that GSDME expression was significantly reduced in human RB tissues and cell lines. Downregulation of GSDME expression reduced the sensitivity of cells to chemotherapeutic drugs. Decitabine treatment and transfection with GSDME-overexpressing lentivirus (LV-GSDME) upregulated GSDME expression in Y79 and WERI-RB-1 cell lines. The half maximal inhibitory concentrations (IC50) for carboplatin-induced cell death were significantly reduced. Low-dose carboplatin could achieve the IC50, and no significant difference was found in the production of prodeath-activating proteins, but the mode of cell death changed from apoptosis to pyroptosis. Increased GSDME expression can reduce the required dose of chemotherapeutic drugs. After inhibition of caspase-3 activation, the IC50 of carboplatin-induced cell death was significantly increased in cells with high GSDME expression, and the method of cell death switched from pyroptosis to apoptosis, which increased the concentration of chemotherapeutic drugs. Furthermore, the sensitivity of cells to carboplatin was reduced. The in vivo xenograft tumor model further confirmed that GSDME upregulation could promote carboplatin-induced tumor cell death. Therefore, the sensitivity of cells to chemotherapeutic drugs can be predicted by detecting the GSDME expression level, and we used pyroptosis induction as a new method for promoting tumor death.

Kruppel-like factor 2 acts as a tumor suppressor in human retinoblastoma

Krüppel-like factor 2 (KLF2) belongs to the KLF family of zinc-finger transcription factors and mediates the occurrence and progression of various cancers. However, little is known about its expression pattern and biological role in retinoblastoma (RB). In the present study, we showed that KLF2 was markedly downregulated in human RB tissue compared with retina. KLF2 overexpression significantly inhibited RB cell proliferation and decreased proliferating cell nuclear antigen (PCNA) expression. Subsequently, we confirmed that KLF2 arrested cells at the G1-S phase transition, accompanied by the upregulation of p21 and downregulation of CyclinD1, as well as the activation of mitochondria-mediated apoptosis in RB cells. In addition, KLF2 overexpression contributed to suppressing RB cell migration and invasion by downregulating matrix metallopeptidase 9 (MMP9). On the contrary, KLF2 downregulation promoted RB cells proliferation, migration and invasion. Notably, the KLF2 expression pattern was opposite to that of C-X-C chemokine receptor 4 (CXCR4) in the two RB cell lines, KLF2 overexpression significantly decreased CXCR4 expression, silencing KLF2 had the opposite effect. Furthermore, dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays confirmed that KLF2 directly bound to the CXCR4 promoter and negatively regulated its expression in RB cells. Collectively, our results suggested that KLF2 function as a tumor suppressor in RB and may represent a potential therapeutic target for RB.

TRIB3 promotes proliferation, migration, and invasion of retinoblastoma cells by activating the AKT/mTOR signaling pathway.

Tribbles pseudokinase 3 (TRIB3) is a member of the tribbles-related family, which has been determined in various cancers, including renal cell carcinoma, acute promyelocytic leukemia, colorectal cancer, endometrial cancer, and glioma. However, its role in retinoblastoma (RB) has not yet been explored. The expression level of TRIB3 was detected in RB tissues and cell lines using qRT-PCR. The effects of TRIB3 on cell proliferation and invasion capacities were analyzed with MTT, crystal violet, and transwell assays. Western blot and rescue assays were conducted to explore the underlying mechanism. This study found that TRIB3 was upregulated in human RB tissues compared to adjacent normal tissues both at the mRNA and protein levels. Overexpression of TRIB3 significantly promoted cell proliferation and invasion of RB cells, while TRIB3 knockdown inhibited these processes. Moreover, the mechanism deciphering experiments showed that TRIB3 overexpression can increase AKT and mTOR phosphorylation. Conversely, TRIB3 knockdown decreased the phosphorylation of AKT and mTOR. Additionally, MK2206, a potent AKT inhibitor, blocked the promotive effects of TRIB3 in RB cells. This study demonstrated that TRIB3 acts as an oncogene and plays a crucial role in the proliferation and invasion of RB cells via regulating the AKT/mTOR signaling pathway. Therefore, TRIB3 may serve as a potential target in the diagnosis and/or treatment of RB.

Long Noncoding RNA TRPM2-AS Promotes the Growth, Migration, and Invasion of Retinoblastoma via miR-497/WEE1 Axis.

Long noncoding RNAs (lncRNAs) exhibit vital roles in many types of cancer, including retinoblastoma (RB), the most common primary intraocular malignancy tumor of infancy. A novel lncRNA TRPM2-AS has been demonstrated to be related to multiple cancers; however, its role in RB remains unclear. Here, we aimed to investigate the function of TRPM2-AS in RB. In this study, TRPM2-AS expression in 35 human RB tissues and RB cell lines was detected by real-time PCR. And, the relationship between its expression and clinicopathological characteristics of RB patients was analyzed. RB cells’ proliferation, migration, invasion, apoptosis, and cell cycle were explored after silencing TRPM2-AS. The mechanism of TRPM2-AS in RB was focused on miR-497/WEE1 axis. Additionally, the role and mechanism of TRPM2-AS were confirmed in a xenograft mouse model. We found TRPM2-AS expression was enhanced in RB tissues and cells. And, higher TRPM2-AS expression was related to advanced clinical stage and optic nerve invasion in patients. Downregulation of TRPM2-AS significantly inhibited proliferation, migration, and invasion, elevated apoptosis, attenuated G2/M phase arrest in RB cells, and suppressed tumor growth in vivo. TRPM2-AS acted as a ceRNA for miR-497 to positively regulate WEE1 expression. miR-497 inhibitor or WEE1 overexpression dramatically reversed the effects of TRPM2-AS downregulating on the malignant phenotypes of RB cells. Therefore, TRPM2-AS is an oncogenic lncRNA in RB, and it functions largely through the miR-497/WEE1 pathway. Despite the limited sample size, this study indicates that TRPM2-AS may be a candidate target in RB therapies.

Aurora Kinase B Expression, Its Regulation and Therapeutic Targeting in Human Retinoblastoma.

PurposeAurora kinase B (AURKB) plays a pivotal role in the regulation of mitosis and is gaining prominence as a therapeutic target in cancers; however, the role of AURKB in retinoblastoma (RB) has not been studied. The purpose of this study was to determine if AURKB plays a role in RB, how its expression is regulated, and whether it could be specifically targeted.MethodsThe protein expression of AURKB was determined using immunohistochemistry in human RB patient specimens and immunoblotting in cell lines. Pharmacological inhibition and shRNA-mediated knockdown were used to understand the role of AURKB in cell viability, apoptosis, and cell cycle distribution. Cell viability in response to AURKB inhibition was also assessed in enucleated RB specimens. Immunoblotting was employed to determine the protein levels of phospho-histone H3, p53, p21, and MYCN. Chromatin immunoprecipitation–qPCR was performed to verify the binding of MYCN on the promoter region of AURKB.ResultsThe expression of AURKB was found to be markedly elevated in human RB tissues, and the overexpression significantly correlated with optic nerve and anterior chamber invasion. Targeting AURKB with small-molecule inhibitors and shRNAs resulted in reduced cell survival and increased apoptosis and cell cycle arrest at the G2/M phase. More importantly, primary RB specimens showed decreased cell viability in response to pharmacological AURKB inhibition. Additional studies have demonstrated that the MYCN oncogene regulates the expression of AURKB in RB.ConclusionsAURKB is overexpressed in RB, and targeting it could serve as a novel therapeutic strategy to restrict tumor cell growth.

Long non-coding RNA CASC9 promotes the progression of retinoblastoma via interacting with miR-145-5p

ABSTRACT Abnormal expression of long non-coding RNA cancer susceptibility candidate 9 (CASC9) has been found to play vital roles in many human tumors. However, the role and the regulatory mechanism of CASC9 have not yet been demonstrated in retinoblastoma (RB). Hence, we performed this study to explore the function and mechanism of CASC9 in RB. CASC9 expression was firstly detected in human RB tissues and cells. The influence of CASC9 on the malignant phenotypes of RB cells, including cell proliferation, invasion, epithelial–mesenchymal transition (EMT) and apoptosis, was analyzed by overexpressing or silencing CASC9. The association between CASC9, miR-145-5p and E2F transcription factor 3 (E2F3) was determined by dual-luciferase reporter assay and RNA immunoprecipitation. We found that CASC9 expression was elevated in RB tissues and cells. Overexpression of CASC9 significantly facilitated the proliferation, invasion and EMT of RB cells. On the contrary, knockdown of CASC9 inhibited the proliferation, invasion and EMT, while enhanced the apoptosis of RB cells. CASC9 acted as a competing endogenous RNA (ceRNA) for miR-145-5p to regulate E2F3. Additionally, miR-145-5p inhibitor and E2F3 overexpression both partly reversed the malignant phenotypes of RB cells affected by CASC9 knockdown. However, miR-145-5p overexpression further strengthened these features induced by CASC9 downregulation. These findings suggested that CASC9 contributed to RB development by regulating E2F3 via sponging miR-145-5p. CASC9 might be a possible therapeutic target for RB.

CD24 blunts the sensitivity of retinoblastoma to vincristine by modulating autophagy.

Retinoblastoma (RB) is the most common childhood malignant intraocular tumor. The clinical efficacy of vincristine (VCR) in the treatment of RB is severely limited by drug resistance. Here, we found that CD24, a GPI‐anchored protein, was overexpressed in human RB tissues and RB cell lines, and was associated with the sensitivity of RB cells in response to VCR therapy. We demonstrated that CD24 plays a critical role in impairing RB sensitivity to VCR via regulating autophagy. Mechanistically, CD24 recruits PTEN to the lipid raft domain and regulates the PTEN/AKT/mTORC1 pathway to activate autophagy. Lipid raft localization was essential for CD24 recruitment function. Collectively, our findings revealed a novel role of CD24 in regulating RB sensitivity to VCR and showed that CD24 is a potential target for improving chemotherapeutic sensitivity and RB patient outcomes.

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.

Tumor Suppressor miR-184 Enhances Chemosensitivity by Directly Inhibiting SLC7A5 in Retinoblastoma.

The expression patterns and functional roles of miRNAs in retinoblastoma (RB) are poorly understood, especially those involved in chemoresistance. Here, we validated the expression pattern of 20 potential RB-suppressive miRNAs and confirmed that miR-184 is the most significantly decreased miRNA in human RB tissues, as well as chemoresistant cell line. Bioinformatic and molecular analyses revealed that SLC7A5 has three binding sites of miR-184 and significantly increased in RB tissues. miR-184 negatively correlated with SLC7A5 expression in RB tissues and mainly target position 2494-2513 of the SLC7A5 3′UTR to inhibit its expression. Furthermore, enforced expression of miR-184 reversed the oncogenic roles of SLC7A5 on proliferation, migration, and invasion of RB cells. In addition, miR-184 also enhances chemosensitivity of RB cells via inducing apoptosis and G2/M cell cycle arrest. Molecular studies revealed that miR-184-decreased phosphorylation status of known DNA damage repair sensors of the ATR/ATM pathways and induced persistent formation of γH2AX foci depend on targeting SLC7A5, leading to persistent DNA damage. Thus, targeting the miR-184/SLC7A5 pathway will provide new opportunities for drug development to reverse chemotherapeutic resistance in RB.

Identification of stemness in primary retinoblastoma cells by analysis of stem-cell phenotypes and tumorigenicity with culture and xenograft models

Retinoblastoma (RB) is a primary intraocular malignancy in childhood, and may develop relapse and metastatic disease. This study was to identify the stem-cell properties of primary retinoblastoma cells critical to tumorigenesis and metastasis. Primary cells were isolated from fresh human RB tissues after enucleation, and cultured in serum-free or serum-enriched conditions, with two RB cell-lines Weri-RB1 and Y79 for comparison. Proliferation of primary RB cells were well-maintained in serum-free condition of DMEM/F12 medium, and formed stem-cell like spheroids. The immaturity of cultured primary RB cells was demonstrated by tendency of highly expressed stem-cell markers (CD133, Nestin and OCT4) and suppressed mature retinal-cell markers (GFAP, MAP2 and Recoverin). CD133, a neural stem-cell marker being exclusively studied in RB, was found positive in small patches of cells in archival human RB by immunohistochemistry. Meanwhile, at initial isolation, insignificant CD133+ cells were detected by flow-cytometry, and substantial increase of positivity was observed after several days cultivated in serum-free condition. Cultured primary RB cells were engrafted in subretinal region of BALB/c nude mice for assessment of tumorigenicity. Strong tumorigenic activity and extensive progression of the xenograft retinoblastoma was induced by primary cells as compared with the two cell-lines. Again, immunohistochemistry confirmed that the stem-cell markers were emphasized in the xenograft tumor in mice.Our findings demonstrated that in comparison to the well-established RB cell-lines, cultured primary RB cells possess stem-cell like properties with highly expressed stem-cell markers, self-regenerative growth in culture, and strong in vivo oncogenic potentiality.

MicroRNA‑485 inhibits the malignant behaviors of retinoblastoma by directly targeting Wnt3a.

Deregulation of microRNAs (miRNAs) has been widely reported in retinoblastoma (RB), and the aberrantly expressed miRNAs may serve as crucial epigenetic regulators in the occurrence and development of RB. Therefore, the identification of dysregulated miRNAs in RB may be useful for the development of effective targets for the therapy patients with this disease. miRNA (miR)‑485‑5p (miR‑485) is deregulated in multiple human cancer types and serves crucial roles in their progression and development. However, the expression pattern of miR‑485 and its role in RB have not been well investigated. In the present study, expression levels of miR‑485 in RB tissues and cell lines were measured using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). The effects of miR‑485 overexpression on RB cell proliferation, apoptosis, migration and invasion were examined using Cell Counting Kit‑8 assay, flow cytometric analysis and in vitro migration and invasion assays, respectively. Xenograft tumor formation assay was utilized to determine the influence of miR‑485 on RB tumor growth in vivo. The mechanism responsible for the tumor‑suppressing roles of miR‑485 in RB progression was determined through a series of experiments, including bioinformatics prediction, luciferase reporter assay, RT‑qPCR, western blot analysis and rescue experiments. Herein, a marked downregulation of miR‑485 expression in human RB tissues and cell lines was observed. miR‑485 overexpression suppressed RB cell proliferation, induced cell apoptosis, attenuated cell migration and cell invasion in vitro, and restrained the growth of RB cells in vivo. Additionally, Wnt3a was revealed to be a direct target gene of miR‑485 in RB cells. Wnt3a was upregulated in human RB tissues, and its upregulation was inversely associated with miR‑485. Furthermore, the tumor suppressive roles of Wnt3a silencing were similar to those of miR‑485 overexpression in RB cells. In addition, restoration of Wnt3a expression partially reversed the tumor suppressor action of miR‑485 in RB cells. However, miR‑485 upregulation directly targeted Wnt3a to inhibit activation of the Wnt/β‑catenin signaling pathway in RB cells both in vitro and in vivo. Notably, these results demonstrated that the tumor‑suppressive roles of miR‑485 were at least partially mediated by Wnt3a in RB cells. Therefore, miR‑485 is a potential therapeutic target for treating patients with RB.

MiR-140-5p suppresses retinoblastoma cell growth via inhibiting c-Met/AKT/mTOR pathway.

MiR-140-5p is low expression and acts as a tumor suppressor in various types of human cancers. However, the potential role of miR-140-5p in retinoblastoma (RB) remains unknown. In the present study, we performed the miRNA microarray analysis to investigate whether miRNAs expression are associated with RB tumorigenesis in RB tissues. We found that a large set of miRNAs were ectopic expressions and miR-140-5p is most significantly down-regulated in human RB tissues compared with normal retinas. In addition, low miR-140-5p expression is associated with clinicopathological features (differentiation, invasion, T classification, N classification, cTNM stage, and largest tumor base) and poor survival in RB patients. Furthermore, our results showed that overexpression of miR-140-5p suppresses proliferation and induces apoptosis and cell cycle arrest in RB cell. Meanwhile, we confirmed that c-Met is the functional target of miR-140-5p in RB cell, and miR-140-5p expression is negatively correlated with c-Met in RB tissues. We also found that inhibition of c-Met also suppresses proliferation and induces apoptosis and cell cycle arrest in RB cell. Interestingly, c-Met can rescue the suppressive effects of miR-140-5p on RB cell growth and cell cycle arrest. More importantly, our findings indicated that miR-140-5p may inhibit cell growth via blocking c-Met/AKT/mTOR signaling pathway. Collectively, these results suggested that miR-140-5p might be a potential biomarker and target in the diagnosis and treatment of RB.

Long noncoding RNA NEAT1 promotes the growth of human retinoblastoma cells via regulation of miR-204/CXCR4 axis.

Retinoblastoma (RB) is an aggressive eye cancer of infancy and childhood with high mortality. Studies have shown that long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) is closely related to the progression of multiple cancers. However, its role in RB remains unknown. This study aimed to investigate the role and underlying mechanism of NEAT1 in RB. We first detected the expression of NEAT1 in human RB tissues and cell lines. The effects of NEAT1 on the proliferation, migration, and apoptosis of RB cells were analyzed by loss-of-function. The underlying mechanism of NEAT1 in RB was mainly focused on the microRNA 204/C-X-C chemokine receptor type 4 (miR-204/CXCR4) axis. In addition, the role and mechanism of NEAT1 in RB were further evaluated in a mouse xenograft tumor model. We found NEAT1 and CXCR4 expression levels were elevated, whereas miR-204 expression was decreased in RB tissues and cells. Downregulation of NEAT1 significantly decreased the proliferation and migration but promoted the apoptosis of RB cells. NEAT1 functioned as a competing endogenous RNA for miR-204 to regulate CXCR4 expression. Knockdown of NEAT1 suppressed the tumor volume, tumor weight, and CXCR4 expression, whereas increased miR-204 expression in mice. In conclusion, NEAT1 promotes the development of RB via miR-204/CXCR4 axis, which provides a new target for the treatment of RB disease.

LncRNA XIST promotes the epithelial to mesenchymal transition of retinoblastoma via sponging miR-101

Accumulating evidence demonstrated that abnormal expression of long non-coding RNAs (lncRNAs) was closely associated with cancer development including retinoblastoma (RB). LncRNA X inactive specific transcript (XIST) has been found to function as an oncogene or a tumor suppressor in several cancers. However, the role and underlying mechanism of XIST in RB have not been clarified. The expression of XIST, microRNA (miR)− 101, zinc finger E-box binding homeobox (ZEB) 1, and ZEB2 was detected in human RB tissues and cell lines. The effects of XIST on the proliferation, migration, invasion, epithelial to mesenchymal transition (EMT), and apoptosis of RB cells were evaluated after downregulation of XIST. Furthermore, the mechanism of XIST was mainly focused on miR-101/ZEB1 or ZEB2 signaling. We found the expression of XIST, ZEB1 and ZEB2 was increased, whereas miR-101 was reduced in RB tissues and cells. Knockdown of XIST significantly suppressed the proliferation, migration, invasion and EMT, but promoted the apoptosis and caspase-3 activity. Moreover, we found that XIST functioned as a competing endogenous RNA (ceRNA) for miR-101 to regulate the de-repression of its endogenous targets ZEB1 and ZEB2. In conclusion, these findings suggest that XIST may facilitate the progression of RB through acting as a ceRNA for miR-101 to mediate the expression of ZEB1 and ZEB2. This may provide novel therapeutic options for RB.

Etoposide Upregulates Survival Favoring Sphingosine-1-Phosphate in Etoposide-Resistant Retinoblastoma Cells.

Improved knowledge of retinoblastoma chemotherapy resistance is needed to raise treatment efficiency. The objective of this study was to test whether etoposide alters glucosyl-ceramide, ceramide, sphingosine, and sphingosine-1-phosphate (sphingosine-1-P) levels in parental retinoblastoma cells (WERI Rb1) or their etoposide-resistant subclones (WERI EtoR). WERI Rb1 and WERI EtoR were incubated with 400ng/ml etoposide for 24h. Levels of glucosyl-ceramides, ceramides, sphingosine, sphingosine-1-P were detected by Q-TOF mass spectrometry. Statistical analysis was done by ANOVA followed by Tukey post-hoc test (p<0.05). The mRNA expression of sphingolipid pathways enzymes in WERI Rb1, WERI EtoR and four human retinoblastoma tissue samples was analyzed by quantitative real-time PCR. Pathways enzymes mRNA expression confirmed similarities of human sphingolipid metabolism in both cell lines and tissue samples, but different relative expression. Significant up-regulation of sphingosine was seen in both cell lines (p<0.001). Only sphingosine-1-P up-regulation was significantly increased in WERI EtoR (p<0.01), but not in WERI Rb1 (p>0.2). Both cell lines upregulate pro-apoptotic sphingosine after etoposide incubation, but only WERI EtoR produces additional survival favorable sphingosine-1-P. These data may suggest a role of sphingosine-1-P in retinoblastoma chemotherapy resistance, although this seems not to be the only resistance mechanism.

MicroRNA-497 overexpression decreases proliferation, migration and invasion of human retinoblastoma cells via targeting vascular endothelial growth factor A.

The expression level and roles of microRNA-497 (miR-497) have been frequently reported in previous studies on cancer. However, its expression, function and associated molecular mechanisms in retinoblastoma remain unknown. In the present study, miR-497 expression levels in human retinoblastoma tissues, normal retinal tissues and retinoblastoma cell lines were determined using reverse transcription-quantitative polymerase chain reaction. In addition, a Cell Counting Kit-8 assay, cell migration assay, cell invasion assay, western blot analysis and Dual-Luciferase reporter assay were used to explore the expression, functions and molecular mechanisms of miR-497 in human retinoblastoma. It was demonstrated that miR-497 was significantly downregulated in retinoblastoma tissues and cell lines compared with normal retinal tissues. Ectopic expression of miR-497 decreased the proliferation, migration and invasion of retinoblastoma cells. Furthermore, VEGFA was verified as a potential direct target of miR-497 in vitro. Taken together, the results indicate that miR-497 functions as a tumor suppressor in the carcinogenesis and progression of retinoblastoma via targeting VEGFA. miR-497 should be investigated as a potential therapeutic target for the treatment of retinoblastoma.

Retinoblastoma cells activate the AKT pathway and are vulnerable to the PI3K/mTOR inhibitor NVP-BEZ235.

Retinoblastoma is a pediatric cancer of the retina most often caused by inactivation of the retinoblastoma (RB1) tumor suppressor gene. We previously showed that Rb1 loss cooperates with either co-activating the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, or co-deleting Pten, to initiate retinoblastoma tumors in mice. The objectives of this study were to determine if the AKT pathway is activated in human retinoblastomas and the extent that anti-PI3K therapy induces apoptosis in retinoblastoma cells, alone or in combination with the DNA damaging drugs carboplatin and topotecan. Serial sections from human retinoblastoma tissue microarrays containing 27 tumors were stained with antibodies specific to p-AKT, Ki-67, forkhead box O1 (p-FOXO1), and ribosomal protein S6 (p-S6) using immunohistochemistry and each tumor sample scored for intensity. Human retinoblastoma tumors displayed significant correlation between p-AKT intensity with highly proliferative tumors (p = 0.008) that were also highly positive for p-FOXO1 (p = 0.002). Treatment with BEZ235, a dual PI3K/mTOR inhibitor, reduced phosphorylation levels of the AKT targets p-FOXO and p-S6 and effectively induced apoptosis the Y79 and Weri-1 human retinoblastoma cell lines and in vivo in our retinoblastoma mouse model. Long-term treatment with BEZ235 in vivo using our retinoblastoma-bearing mice induced apoptosis but did not significantly extend the lifespan of the mice. We then co-administered BEZ235 with topotecan and carboplatin chemotherapeutics in vivo, which more effectively induced apoptosis of retinoblastoma, but not normal retinal cells than either treatment alone. Our study has increased the variety of potentially effective targeted treatments that can be considered for human retinoblastoma.

Loukoumasomes Are Distinct Subcellular Structures from Rods and Rings and Are Structurally Associated with MAP2 and the Nuclear Envelope in Retinal Cells.

“Rods and rings” (RR) and loukoumasomes are similarly shaped, subcellular macromolecular structures with as yet unknown function. RR, so named because of their shape, are formed in response to inhibition in the GTP or CTP synthetic pathways and are highly enriched in the two key enzymes of the nucleotide synthetic pathway. Loukoumasomes also occur as linear and toroidal bodies and were initially inferred to be the same as RR, largely due to their shared shape and size and the fact that it was unclear if they shared the same subcomponents. In human retinoblastoma tissue and cells we have observed toroidal, perinuclear, macromolecular structures of similar size and antigenicity to those previously reported in neurons (neuronal-loukoumasomes). To further characterize the subcomponents of the retinal-loukoumasomes, confocal analysis following immunocytochemical staining for alpha-tubulin, beta-III tubulin and detyrosinated tubulin was performed. These studies indicate that retinal-loukoumasomes are enriched for beta-III tubulin and other tubulins associated with microtubules. Immunofluorescence together with the in situ proximity ligation assay (PLA), confirmed that beta-III tubulin colocalized with detyrosinated tubulin within loukoumasomes. Our results indicate that these tissues contain only loukoumasomes because these macromolecular structures are immunoreactive with an anti-tubulin antibody but are not recognized by the prototype anti-RR/inosine monophosphate dehydrogenase (IMPDH) antibody (It2006). To further compare the RR and retinal-loukoumasomes, retinoblastoma cells were exposed to the IMPDH-inhibitor ribavirin, a drug known to induce the formation of RR. In contrast to RR, the production of retinal-loukoumasomes was unaffected. Coimmunostaining of Y79 cells for beta-III tubulin and IMPDH indicate that these cells, when treated with ribavirin, can contain both retinal-loukoumasomes and RR and that these structures are antigenically distinct. Subcellular fractionation studies indicate that ribavirin increased the RR subcomponent, IMPDH, in the nuclear fraction of Y79 cells from 21.3 ± 5.8% (0 mM ribavirin) to 122.8 ± 7.9% (1 mM ribavirin) while the subcellular localization of the retinal-loukoumasome subcomponent tubulin went unaltered. Further characterization of retinal-loukoumasomes in retinoblastoma cells reveals that they are intimately associated with lamin folds within the nuclear envelope. Using immunofluorescence and the in situ PLA in this cell type, we have observed colocalization of beta-III tubulin with MAP2. As MAP2 is a microtubule-associated protein implicated in microtubule crosslinking, this supports a role for microtubule crosslinkers in the formation of retinal-loukoumasomes. Together, these results suggest that loukoumasomes and RR are distinct subcellular macromolecular structures, formed by different cellular processes and that there are other loukoumasome-like structures within retinal tissues and cells.

Heart Failure: From Protein to Phenotype37MicroRNA-494 reduces ATF3 expression and promotes heart failure in cardiac hypertrophic remodeling in vivo38A novel recessive plakophilin-2 gene mutation causes severe arrhythmogenic dilated cardiomyopathy and sudden cardiac death at young age39Investigation of titin expression in explanted hearts with familial dilated cardiomyopathy and TTN truncating variants

Heart Failure: From Protein to Phenotype37MicroRNA-494 reduces ATF3 expression and promotes heart failure in cardiac hypertrophic remodeling in vivo38A novel recessive plakophilin-2 gene mutation causes severe arrhythmogenic dilated cardiomyopathy and sudden cardiac death at young age39Investigation of titin expression in explanted hearts with familial dilated cardiomyopathy and TTN truncating variants