Cytochrome P450 Directed Prodrug Activation Therapy in Research of Cancer Enzymology

Cancer enzymology is a promising filiation of bio-medical sciences. In thepast decades, enzymes, such as GST(glutathione S-transferase) , PKC(protein kinase C) , Topo(DNAtopoisomerases), TK(tyrosine kinase), CD (bacterial cytosine deaminase), CPG2(carboxypeptidase G2) ,and PNP (purine nucleoside phosphorylase), have been known to bear close relations to cancer. Theirspecific expression and influence on the process of tumor initiation, promotion and progressionattract scientists to apply them as a biochemical marker of certain malignant tumor, a predictor ofresponse in cancer chemotherapy; to apply them to drug design, tumor prevention and as adjuvant toradiotherapy or surgery.

A versatile platform for single-molecule enzymology of restriction endonuclease

Enzymes are the major players for many biological processes.Fundamental studies of the enzymatic activity at the single-molecule level provides important information that is otherwise inaccessible at the ensemble level.Yet,these single-molecule experiments are technically di±cult and generally require complicated experimental design.Here,we develop a Holliday junction(HJ)-based platform to study the activity of restriction endonucleases at the single-molecule level using single-molecule FRET(sm-FRET).We show that the intrinsic dynamics of HJ can be used as the reporter for both the enzyme-binding and the substrate-release events.Thanks to the multiple-arms structure of HJ,the fluorophore-labeled arms can be different from the surface anchoring arm and the substrate arm.Therefore,it is possible to independently change the substrate arm to study different enzymes with similar functions.Such a design is extremely useful for the systematic study of enzymes from the same family or enzymes bearing different pathologic mutations.Moreover,this method can be easily extended to study other types of DNA-binding enzymes without too much modi fication of the design.We anticipate it can find broad applications in single-molecule enzymology.

Philippine retinoblastoma initiative multi-eye center study 2010-2020

AIM:To provide a comprehensive and more representative national data on the disease,especially on treatment options and outcomes,and to determine access of retinoblastoma patients from Luzon,Visayas and Mindanao to eye care,and determine if access is associated with delay in consultation,staging and outcomes.METHODS:Cohort study of retinoblastoma patients seen in eleven institutions located in the three major areas of the Philippines namely Luzon,Vizayas and Mindanao from 2010-2020.RESULTS:Totally 636 patients,involving 821 eyes,were included.Majority(57%)were from Luzon and were seen in institutions in Luzon(72%).Annually,58±10 new cases were seen with 71%having unilateral disease.Median delay of consultation remained long at 9(3,17)mo,longest in patients with unilateral disease(P<0.02)and those from the Visayas(P<0.003).Based on the International Retinoblastoma Staging System,only 35%of patients had Stage 1 while 47%already had extraocular disease.Enucleation was the most common treatment received by 484 patients while intravenous chemotherapy was received by 469.There were 250(39%)patients alive,195(31%)dead,85(13%)abandoned,17(3%)refused and 89(14%)with no data.CONCLUSION:This study presents the largest cohort of retinoblastoma patients in the Philippines in terms of patients’and participating institutions’number and geographical location and type of institution(private and public).It also presents more comprehensive data on the treatments used and outcomes(survival,globe salvage,and vision retention rates).Delay in consultation was still long among patients leading to advanced disease stage and lower survival rate.Despite increasing capacity to diagnose and manage retinoblastoma in the country,the delay of consultation remains long primarily due to accessibility issues to eye care institutions especially in the Visayas and financial concerns.The delay was still significant that overall survival rate remain low.

Prox1 Suppresses Proliferation and Drug Resistance of Retinoblastoma Cells via Targeting Notch1

Objective Retinoblastoma(RB)is a prevalent type of eye cancer in youngsters.Prospero homeobox 1(Prox1)is a homeobox transcriptional repressor and downstream target of the proneural gene that is relevant in lymphatic,hepatocyte,pancreatic,heart,lens,retinal,and cancer cells.The goal of this study was to investigate the role of Prox1 in RB cell proliferation and drug resistance,as well as to explore the underlying Notch1 mechanism.Methods Human RB cell lines(SO-RB50 and Y79)and a primary human retinal microvascular endothelial cell line(ACBRI-181)were used in this study.The expression of Prox1 and Notch1 mRNA and protein in RB cells was detected using quantitative real time-polymerase chain reaction(RT-qPCR)and Western blotting.Cell proliferation was assessed after Prox1 overexpression using the Cell Counting Kit-8 and the MTS assay.Drug-resistant cell lines(SO-RB50/vincristine)were generated and treated with Prox1 to investigate the role of Prox1 in drug resistance.We employed pcDNA-Notch1 to overexpress Notch1 to confirm the role of Notch1 in the protective function of Prox1.Finally,a xenograft model was constructed to assess the effect of Prox1 on RB in vivo.Results Prox1 was significantly downregulated in RB cells.Overexpression of Prox1 effectively decreased RB cell growth while increasing the sensitivity of drug-resistant cells to vincristine.Notch1 was involved in Prox1’s regulatory effects.Notch1 was identified as a target gene of Prox1,which was found to be upregulated in RB cells and repressed by increased Prox1 expression.When pcDNA-Notch1 was transfected,the effect of Prox1 overexpression on RB was removed.Furthermore,by downregulating Notch1,Prox1 overexpression slowed tumor development and increased vincristine sensitivity in vivo.Conclusion These data show that Prox1 decreased RB cell proliferation and drug resistance by targeting Notch1,implying that Prox1 could be a potential therapeutic target for RB.

Decoding Retinoblastoma: Differential Gene Expression

Background: Retinoblastoma, the most common intraocular pediatric cancer, presents complexities in its genetic landscape that necessitate a deeper understanding for improved therapeutic interventions. This study leverages computational tools to dissect the differential gene expression profiles in retinoblastoma. Methods: Employing an in silico approach, we analyzed gene expression data from public repositories by applying rigorous statistical models, including limma and de seq 2, for identifying differentially expressed genes DEGs. Our findings were validated through cross-referencing with independent datasets and existing literature. We further employed functional annotation and pathway analysis to elucidate the biological significance of these DEGs. Results: Our computational analysis confirmed the dysregulation of key retinoblastoma-associated genes. In comparison to normal retinal tissue, RB1 exhibited a 2.5-fold increase in expression (adjusted p Conclusions: Our analysis reinforces the critical genetic alterations known in retinoblastoma and unveils new avenues for research into the disease’s molecular basis. The discovery of chemoresistance markers and immune-related genes opens potential pathways for personalized treatment strategies. The study’s outcomes emphasize the power of in silico analyses in unraveling complex cancer genomics.

Retinoblastoma: The Situation in Burkina Faso over Ten Years

Context: In Burkina Faso, there is only one retinoblastoma treatment center located in the capital. Nowadays, the treatment of retinoblastoma has benefited from the contribution of scientific progress. Objective: The aim was to take stock of the situation of retinoblastoma in the pediatric oncology department from January 1, 2010 to December 31, 2019. Materials and Methods: This was a descriptive cross-sectional study with retrospective data collection over a 10-year period, based on records of patients admitted to pediatric oncology department of CHU-YO. Data were analysed using CS Pro version 7.2 software. Categorical variables were compared using Pearsons Chi-square test at the 5% significance level. Overall survival was estimated using the Kaplan-Meier method. Operational definitions were used for lost to follow-up, consultation and diagnosis delays. Results: We collected a total of 204 cases in 10 years, i.e. an annual average of 20.4 cases/year. The mean age at diagnosis was 37.5 months for unilateral cases and 26.4 months for bilateral cases. Male predominance was noted, with a sex ratio of 1.31. The majority of patients came from disadvantaged backgrounds (72% farming fathers and 91% housewives). Clinically, leukocoria and exophthalmos were the main presenting features. The average time to consultation was long (8.73 months) and unilateral localization was predominantly unilateral at 77%. In terms of treatment, 102 patients were eligible for curative treatment and 80 for palliative treatment. The prognosis was poor, with 41% death and numerous cases of lost to follow-up (18%). Overall survival was estimated at 32%. The factor associated with the lethality of retiniblastoma was the extension of the tumor to other organs. Conclusion: Recognition of the early clinical signs of retinoblastoma can anticipate the occurrence of this cancer. Health professionals should be encouraged to perform the Buckner test every time they come into contact with children aged 0 to 5, and the public should be encouraged to examine their childrens eyes.

Cone-rod homeobox transcriptionally activates TCF7 to promote the proliferation of retinal pigment epithelial and retinoblastoma cells in vitro

AIM:To investigate the proliferation regulatory effect of cone-rod homeobox(CRX)in retinal pigment epithelium(RPE)and retinoblastoma(RB)cells to explore the potential application and side effect(oncogenic potential)of CRXbased gene therapy in RPE-based retinopathies.METHODS:Adult human retinal pigment epithelial(ARPE)-19 and human retinal pigment epithelial(RPE)-1 cells and Y79 RB cell were used in the study.Genetic manipulation was performed by lentivirus-based technology.The cell proliferation was determined by a CellTiter-Glo Reagent.The mRNA and protein levels were determined by quantitative real-time polymerase chain reaction(qPCR)and Western blot assay.The transcriptional activity of the promoter was determined by luciferase reporter gene assay.The bindings between CRX and transcription factor 7(TCF7)promoter as well as TCF7 and the promoters of TCF7 target genes were examined by chromatin immunoprecipitation(ChIP)assay.The transcription of the TCF7 was determined by a modified nuclear run-on assay.RESULTS:CRX overexpression and knockdown significantly increased(n=3,P<0.05 in all the cells)and decreased(n=3,P<0.01 in all the cells)the proliferation of RPE and RB cells.CRX overexpression and knockdown significantly increased and deceased the mRNA levels of Wnt signaling target genes[including MYC proto-oncogene(MYC),JUN,FOS like 1(FOSL1),CCND1,cyclin D2(CCND2),cyclin D3(CCND3),cellular communication network factor 4(CCN4),peroxisome proliferator activated receptor delta(PPARD),and matrix metallopeptidase 7(MMP7)]and the luciferase activity driven by the Wnt signaling transcription factor(TCF7).TCF7 overexpression and knockdown significantly increased and decreased the proliferation of RPE and RB cells and depletion of TCF7 significantly abolished the stimulatory effect of CRX on the proliferation of RPE and RB cells.CRX overexpression and knockdown significantly increased and decreased the mRNA level of TCF7 and the promoter of TCF7 was significantly immunoprecipitated by CRX antibody.CONCLUSION:CRX transcriptionally activates TCF7 to promote the proliferation of RPE and RB cells in vitro.CRX is a potential target for RPE-based regenerative medicine.The potential risk of this strategy,tumorigenic potential,should be considered.

Retinoblastoma binding protein 4 up-regulation is correlated with hepatic metastasis and poor prognosis in colon cancer patients

Background: Retinoblastoma binding protein 4 (RBBP4) plays an essential role in the development of multiple cancers. However, its relationship with prognosis in colon cancer and colon cancer hepatic metastasis has not been elucidated. The aim of this study was to explore the relationship between RBBP4 expression and prognosis of colon cancer patients and to evaluate RBBP4 as a new prognostic marker in these patients. Methods: Eighty colon cancer patients underwent surgical resection of the colon were enrolled. Among them, forty colon cancer patients suffered with hepatic metastasis. The colon cancer tissues, para-colon cancer tissues, and hepatic metastatic cancer tissues were collected from the pathological department for further analysis. The expression of RBBP4 proteins was examined by immunohistochemistry and correlated with clinicopathological parameters. The Cancer Genome Atlas (TCGA) database was used to validate the expression and explore its relationship with clinical characteristics. Results: RBBP4 was up-regulated in the colon cancer tissues compared with the para-colon cancer tissues. The analysis of TCGA database verified the upregulation of RBBP4 in the colon cancer tissues and RBBP4 overexpression was correlated with nerve invasion and poor outcomes of chemotherapy. Moreover, the positive rate of RBBP4 expression in 40 colon cancer patients with hepatic metastasis was higher in the hepatic metastatic cancer tissues (39/40, 97.5%) than in the colon cancer tissues (26/40, 65.0%). Our clinicopathological analysis showed that RBBP4 expression was significantly correlated with vascular invasion, hepatic metastasis, and lymph node involvement (all P < 0.05). Additionally, the survival analysis demonstrated that RBBP4 over-expression was correlated with poor prognosis. Conclusions: RBBP4 was upregulated in the colon cancer. RBBP4 may be a novel predictor for poor prognosis of colon cancer and colon cancer hepatic metastasis.

Retinoblastoma: concerning its initiation and treatment

·Retinoblastoma (RB) is the most common intraocular cancer of infancy and childhood. This cancer is initiated by mutation on , the tumor suppressor gene that is responsible for the regulation of both cell cycle and gnome stability in retinal cells. Patients with a constitutional mutation on can be inherited. RB occurs approximately 1 in every 15 000-20 000 live births. The worldwide mortality for this cancer is about 5%-11%. However, this rate rises to about 40%-70% in developing countries due to a delay in diagnosis. A wide variety of options are available for the treatment, but often a combination of therapies is adopted to optimize individualized care. ·

5-Aza-2'-deoxycytidine inhibits retinoblastoma cell by reactivating epigenetically silenced RASSF1A gene

AIM: To investigate the effect of 5-Aza-2’-deoxycytidine(5-Aza-CdR),a DNA methyltransferase(DNMT) inhibitor,on the growth and survival of the Chinese retinoblastoma(RB) cell line HXO-RB44. ·METHODS: The DNA methylation status of the Ras association domain family(RASSF1A) promoter in the presence of 5-Aza-CdR at different concentrations was analyzed by methylation-specific polymerase chain reaction(MSP). RASSF1A mRNA and protein levels were measured by semiquantitative RT-PCR and immunohistochemistry staining,respectively,when cells were treated with 5.0μmol/L of 5-Aza-CdR. The effect of 5.0μmol/L 5-Aza-CdR on the proliferation and viability of HXO-RB44 cells was examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay and flow cytometry. ·RESULTS: 5-Aza-CdR efficiently induced cell cycle arrest at G0 /G1 and apoptotic death in HXO-RB44 cells. MSP analysis showed that unmethylated RASSF1A DNA increased and methylated RASSF1A decreased in a dose-dependent manner in a range of 0.5-5.0μmol/L 5-Aza-CdR. Accordingly,RASSF1A expression was reactivated at both mRNA and protein levels. Incubation time of 5-Aza-CdR treatment also functioned as a factor for the demethylation status of RASSF1A promoter DNA,with a plateau on day four. 5-Aza-CdR at 5.0μmol/L completely demethylated the RASSF1A promoter in HXORB44 cells on day four,and as a result,RASSF1A expression increased significantly from day 4 to day 7.·CONCLUSION: 5-Aza-CdR inhibits the growth of the HXO-RB44 RB cell line and induces apoptosis by demethylating the RASSF1A gene.

Update on pathology of retinoblastoma

Retinoblastoma is caused by mutational inactivation of both alleles of the RB1 gene, which maps to chromosome 13 q14 and encodes retinoblastoma protein that acts as a tumor suppressor. Histopathological high-risk features of retinoblastoma are predictive of metastasis or local recurrence. The focus of this update is to emphasize the recent advances in pathology, various molecular key pathways and genome wide approaches for newer potential therapeutic future targets associated with retinoblastoma tumor biology. This review article highlights the new biomarkers expressed by the retinoblastoma tumor for the better survival of patients.

Extraocular retinoblastoma in Indian children:clinical,imaging and histopathological features

AIMTo study eyes with extraocular dissemination (EORB), with the following aims: first to establish the mean lag period and to understand various reasons for delayed presentation, second to study their imaging profiles and third to analyze histopathological features of eyes enucleated after neoadjuvant chemotherapy.

Suppressive effect of microRNA-143 in retinoblastoma

AIM： To investigate micro RNA-143 expression and effect on suppression of retinoblastoma（RB） cells. METHODS： The expression of micro RNA-143 was investigated and compared in normal human retina tissue samples and in RB cell lines of Y79 and Weri1. The micro RNA-143 mimics were transfected into the RB cell lines separately, and its effect on RB cell lines was detected using reverse-transcription quantitative polymerase chain reaction and Western blotting methods. RESULTS： The micro RNA-143 expression was significantly suppressed in RB cell lines. Overexpression of micro RNA-143 significantly lowered cell viability and invasion of the RB cell lines, and increased the number of apoptotic cells. Meanwhile, the Bax expression was up-regulated and much higher in the micro RNA-143 mimics transfected group than that in the negative control and the micro RNA-143 inhibitor groups. CONCLUSION： Micro RNA-143 exhibits suppressive effects in RB. The current study provides the perspective of a potential therapeutic treatment for RB.

Pro-apoptotic and anti-proliferative effects of Physalis angulata leaf extract on retinoblastoma cells

AIM: To investigate the effect of Physalis angulata leaf extract on apoptotic and proliferation of retinoblastoma cells. Despite several previous studies evidencing the anticancer potential of Physalis angulata;however, certain study that proves its benefits in retinoblastoma cancer cells has been limited.METHODS: This study utilizes an in-vitro experimental study by applying Y79 human retinoblastoma cell line culture obtained from the American Type Culture Collection(ATCC;10801 University Boulevard Manassas, VA 20110, USA). The cell was divided into 4 groups. Group I was the control group without the administration of Physalis angulata leaf extract. Whereas, group II, II and IV are engaged with 25, 50, and 100 μg/mL of Physalis angulata leaf extract respectively. After a 24 h incubation, an examination with microtetrazolium(MTT) cell proliferation assay and Annexin V apoptosis detection was conducted. Statistical analysis was performed with the Tukey test.RESULTS: Physalis angulata leaf extract improved apoptosis and significantly reduced the number of living cells in retinoblastoma cells, along with the increase in the given dose. Based on the Tukey test, a significant difference was found in the treatment group at 50 μg/mL(P=0.025) and 100 μg/mL(P=0.001) in the measurement of apoptosis. Proliferation measurements also indicated a significant decrease in the number of living cells in the 50μg/m L treatment group(P=0.004), and in the 100 μg/mL treatment group(P=0.000). Meanwhile, a dose of 25 μg/mL indicated insignificant difference in the two measurements. Improved apoptosis and decreased number of living cells occured at a dose of 100 μg/mL. Decreased number of living cells(in the measurement of proliferation) was due to the inhibited proliferation or improved apoptosis.CONCLUSION: Physalis angulata leaf extract improve apoptosis in retinoblastoma cell culture, requiring further research to inhibit proliferation.

Epidemiology and Rb 1 gene of retinoblastoma

Retinoblastoma (Rb) is the most common eye cancer in children and it can be inherited. Rb is quite rare and originators from the neural retina with a significant genetic component in etiology, which occurs in approximately 1 in every 20 0000 births. In children with the heritable genetic form of Rb, there is a mutation on chromosome 13, called the retinoblastoma 1 (Rb1) gene. Early diagnosis and intervention is critical to the successful treatment of the Rb. The Rb1 gene is the first cloned tumor suppressor gene. As a negative regulator of the cell cycle, Rb1 gene could maintain a balance between cell growth and development through binding to transcription factors and regulating the expression of genes involved in cell proliferation and differentiation. Thus, it is involved in cell cycle, cell senescence, growth arrest, apoptosis and differentiation. We summarized the recent advances on the epidemiology and Rb1 gene of Rb in this review.

Use of intra-arterial chemotherapy for retinoblastoma:results of a survey

·AIM: To obtain baseline knowledge about the current use of intra-arterial chemotherapy(SSOAIC) in centers worldwide.·METHODS: A survey including questions about the use of SSOAIC was emailed to retinoblastoma experts.·RESULTS:Seventy-nine(response rate 69.9%) doctors from 63 centers in 35 countries responded. Thirty-one centers from 19 countries use SSOAIC. Twelve performed more than 50 procedures. Melphalan is the most commonly used drug but 15 centers use more than one drug. First line therapy for advanced unilateral disease is the most common use of SSOAIC(74.2%). Centers with larger experience(】50 applications) were less likely using melphalan alone(P =0.06) and significantly more likely using SSOAIC in more situations such as second line in preference to radiotherapy P =0.05. Nineteen(61.2%)stated that SSOAIC improved their results and 21(77.8%)reported less toxicity compared to other treatments.Three centers reported that SSOAIC did not improve their results. There were regional variations in the use of SSOAIC which is used more frequently as secondary treatment in Europe compared to the USA and Japan.Ten centers identified cost is the major limiting factor for SSOAIC.· CONCLUSION: SSOAIC is used in an increasing number of centers worldwide with regional variations.Centers with more experience in SSOAIC use it in more situations including other drugs than melphalan. The majority of the centers using this technique reportedimproved results and few complications.

MiR-200c suppresses the migration of retinoblastoma cells by reversing epithelial mesenchymal transition

AIM： To analyze the relationship between clinical features and epithelial mesenchymal transition （EMT） in retinoblastoma （RB）, further to investigate whether miR-200c regulates the EMT and migration of RB cells. METHODS： Expression of EMT-related markers and tumor- related factors were detected by immuno-histochemistry analysis in RB tissue from 29 cases. Correlations between their expression and clinical characteristics were analyzed. The regulation effects of miR-200c on EMT-related markers, tumor-related factors were observed in mRNA level and protein level by real-time polymerase chain reaction （PCR） and Western blot, respectively, in Y79 and Weri-rbl cells. Its effects on migration force of these RB cell lines were also detected with Transwell test. RESULTS： Lower expression of E-cadherin was present in the cases with malignant prognosis. MiR-200c promoted the expression of E-cadherin and decreased the expression of Vimentin and N-cadherin in Y79 and Weri-rbl cells. Migration force of RB cells could be inhibited by miR-200c. CONCLUSION： EMT might be associated with bad prognosis in RB. MiR-200c suppresses the migration of retinoblastomatous cells by reverse EMT.

Effect on proliferation and apoptosis of retinoblastoma cell by RNA inhibiting high mobility group protein box-1 expression

AIM： To investigate the effect of high mobility group protein box-1 （HMGB1） siRNA on proliferation and apoptosis of retinoblastoma （Rb） cells.METHODS： The expression of HMGB1 in Rb cells were detected by real-time polymerase chain reaction （RT-PCR） and Western blot. Chemically synthesized HMGB1 siRNA was transfected into Y79 cells. The inhibitory rate was also examined by RT-PCR and Western blot. After HMGB1 siRNA transfection, the cell proliferation was analyzed by MTT, and cell apoptosis was detected by Caspase-3 active detection kit. Cell cycle distribution and apoptosis were detected by flow cytometry. RESULTS： The expression of HMGB1 significantly elevated in Rb cells （P〈0.01）. After transfected by siRNA, the HMGB1 protein level of Y79 cells was significantly reduced （P〈0.01）. After siRNA interference HMGB1, the proportion of proliferating cells reduced, and the proportion of quiescent cells increased （P〈0.05）. In addition, apoptosis rate of Y79 cells increased from 2.03% to 9.10% after interfering with HMGB1 siRNA （P〈0.05）.CONCLUSION： Specific HMGB1 siRNA can inhibit the expression of HMGB1. The effect may be attributed to inhibit the proliferation and promote cell apoptosis.

Expression of multidrug-resistance associated proteins in human retinoblastoma treated by primary enucleation

AIM： To reveal the expression of multidrug-resistance associated proteins： glutathione-S-transferase π（GSTπ）, P-glycoprotein（P-gp） and vault protein lung resistance protein（LRP） in retinoblastoma（RB） without any conservative treatment before primary enucleation and to correlate this expression with histopathological tumor features. METHODS： A total of 42 specimens of RB undergone primary enucleation were selected for the research. Sections from the formalin-fixed, paraffin-embedded specimens were stained with HE and immunohistochemistry to detect the expression of GSTπ, P-gp and LRP.RESULTS： GSTπ was expressed in 39/42（92.86%） RBs and in 9/9（100%） well-differentiated RBs. P-gp/GSTπ was found in 30（71.42%） of 42 RBs. Totally 9（21.43%） tumors were well differentiated and 33（78.57%） were poorly differentiated. Totally 15（35.71%） eyes had optic nerve（ON） tumor invasion, 36（85.71%） had choroidal tumor invasion, and 14（33.33%） had simultaneous choroidal and ON invasion. There was no statistically significant relationship between P-gp, GSTπ, LRP positivity and the degree of ocular layer tumor invasion and ON tumor invasion（P〉0.05）. CONCLUSION： RB intrinsically expresses GSTπ, P-gp and LRP. GSTπ expression is positive in 100% welldifferentiation ones, so in which way it is correlated with differentiation. But the other two proteins expressions are not related to tumor differentiation and to the degree of tumor invasion. GSTπ may be a new target of chemotherapy in RB.

Effect of miR-513a-5p on Etoposide-stimulating B7-H1 Expression in Retinoblastoma Cells

This study investigated the effect of etoposide,an anticancer chemotherapy drug,on B7-H1 expression in retinoblastoma(Rb) cells and the role of miR-513a-5p in the process.Rb cells were divided into control and etoposide groups.In the etoposide group,cells were treated with etoposide at different concentrations(2.5,5,10,20 and 40 μg/mL) for 24 h.Those given no treatment of etopside served as controls.Reverse transcription polymerase chain reaction(RT-PCR),fluorescence quantitative PCR and flow cytometry were performed to measure the mRNA and protein expression of B7-H1 in Rb cells.The mRNA expression of miR-513a-5p in Rb cells before and after etoposide treatment was also detected by fluorescence quantitative PCR.The miR-513a-5p mimics and the miR-513a-5p inhibitor were transfected into Rb cells separately,and fluorescence quantitative PCR and flow cytometry were used to detect the effect of the miR-513a-5p mimics or inhibitor on B7-H1 expression.TargetScan5.2 was employed to predict the miR-513a-5p binding sites in the 3’-untranslated region of B7-H1 mRNA.Luciferase reporter plasmids carrying this site were prepared and transfected into Rb cells and luciferase activity analyzed.The results showed that etoposide stimulated the mRNA and protein expression of B7-H1 in Rb cells,which reached a maximal level after treatment with 5 μg/mL etoposide(P<0.05).However,miR-513a-5p expression was decreased in Rb cells after etoposide treatment.When the miR-513a-5p inhibitor was added,B7-H1 expression was increased with the concentration of the miR-513a-5p inhibitor(P<0.05).Moreover,B7-H1 expression was decreased gradually with the concentration of the miR-513a-5p mimics increased(P<0.01).Additionally,the miR-513a-5p mimics were found to inhibit the luciferase activity.It was concluded that etoposide can promote B7-H1 expression in Rb cells,which may be associated with chemoresistance.The promoting effect of etoposide on B7-H1 expression can be reversed by miR-513a-5p mimics.MiR-513a-5p inhibits the mRNA and protein expression of B7-H1 via binding to the 3’-UTR of B7-H1 mRNA.