Objective To investigate the cellular characteristics in the development of retinal tumors induced by MY-CN overexpression,and to find the key proteins that play an important role in this process.Methods T-MYCN Y1 and Y2 cells cultured in vitro for 1 year and 2 years were selected for the experiment.The WERI-RB-1 cell line obtained from Shanghai Cell Bank of Chinese Academy of Sciences was taken as the mature retinoblastoma(RB)control(WERI-Rb-1 group).Untreated normal human retinal tissues were used as the control group.Cells were inoculated into a 24-well plate at a density of 1 × 104 cells per well,and the cell morphology was observed under a microscope and images were collected.Cell count was performed on the 4th,8th and 12th day after inoculation.Immunofluorescence staining was employed to de-tect the expression of the proliferation marker Ki67 and cone cell marker L/M opsin in each group.Quantitative real time polymerase chain reaction(qRT-PCR)was utilized to assess the expression of MYCN,CCNB1,CDK1,SYK,and RXRγ in cells across all groups.Proteomics analysis was performed to detect variations in protein expression profiles across groups and to identify key regulatory genes.Subsequently,cell growth and proliferation were evaluated after OTX2 knockdown by lentiviruses.Results The growth curve showed that there were(59.17±4.01)× 104 cells in the T-MYCN Y1 group,(85.14±4.54)× 104 cells in the T-MYCN Y2 group and(100.73±1.99)× 104 cells in the WERI-Rb-1 group on the 12th day of in-vitro culture(all P＜0.05).Compared with those in the control group,the positive cell rates of Ki67 and L/M opsin increased in T-MYCN Y1,T-MYCN Y2 and WERI-Rb-1 groups(all P＜0.001).The relative expression levels of MYCN mR-NAs in T-MYCN Y1,T-MYCN Y2 and WERI-Rb-1 groups were significantly higher than those in the control group(all P＜0.001).The relative expression levels of CCNB1 and CDK1 mRNAs also increased significantly in the three groups,com-pared with those in the control group(all P＜0.01).There was no significant difference in the relative expression of SYK mRNAs between T-MYCN Y1 and control groups(P＞0.05).The relative expression level of RXRγ mRNAs was significantly higher in the T-MYCN Y1 group than that in the control group(P＜0.05).The relative expression levels of SYK and RXRγmRNAs in T-MYCN Y2 and WERI-Rb-1 groups were significantly increased,compared with those in the control group(all P＜0.05).GO enrichment analysis showed that these differentially-expressed proteins were enriched into protein complex assembly and mitochondria pathways.KEGG enrichment analysis revealed that the enriched pathways of these differential-ly-expressed proteins included carbon metabolism,metabolic pathway and fatty acid degradation.Both proteomics and Western blot analyses indicated that OTX2 expression levels were the highest in the WERI-Rb-1 group,second highest in the T-MYCN Y2 group,and the lowest in the T-MYCN Y1 group(all P＜0.01).According to qRT-PCR,the expression levels of OTX2 mRNAs in T-MYCN Y1,T-MYCN Y2 and WRI-Rb-1 cells with OTX2 knockdown were lower than those in empty vec-tor controls(all P＜0.05).The growth curve of cells showed that after knocking down OTX2 in the three groups of cells,both cell growth and proliferation ability decreased significantly(all P＜0.001).Conclusion During the development of retinal tumors induced by MYCN overexpression,cells gradually exhibit characteristics similar to WERI-Rb-1 cells,which are a typical RB cell line.OTX2 plays an important role in MYCN amplification or the growth and proliferation of highly ex-pressed RB.Targeting OTX2 may become a new research direction for the treatment of RB.

Objective To investigate the cellular characteristics in the development of retinal tumors induced by MY-CN overexpression,and to find the key proteins that play an important role in this process.Methods T-MYCN Y1 and Y2 cells cultured in vitro for 1 year and 2 years were selected for the experiment.The WERI-RB-1 cell line obtained from Shanghai Cell Bank of Chinese Academy of Sciences was taken as the mature retinoblastoma(RB)control(WERI-Rb-1 group).Untreated normal human retinal tissues were used as the control group.Cells were inoculated into a 24-well plate at a density of 1 × 104 cells per well,and the cell morphology was observed under a microscope and images were collected.Cell count was performed on the 4th,8th and 12th day after inoculation.Immunofluorescence staining was employed to de-tect the expression of the proliferation marker Ki67 and cone cell marker L/M opsin in each group.Quantitative real time polymerase chain reaction(qRT-PCR)was utilized to assess the expression of MYCN,CCNB1,CDK1,SYK,and RXRγ in cells across all groups.Proteomics analysis was performed to detect variations in protein expression profiles across groups and to identify key regulatory genes.Subsequently,cell growth and proliferation were evaluated after OTX2 knockdown by lentiviruses.Results The growth curve showed that there were(59.17±4.01)× 104 cells in the T-MYCN Y1 group,(85.14±4.54)× 104 cells in the T-MYCN Y2 group and(100.73±1.99)× 104 cells in the WERI-Rb-1 group on the 12th day of in-vitro culture(all P＜0.05).Compared with those in the control group,the positive cell rates of Ki67 and L/M opsin increased in T-MYCN Y1,T-MYCN Y2 and WERI-Rb-1 groups(all P＜0.001).The relative expression levels of MYCN mR-NAs in T-MYCN Y1,T-MYCN Y2 and WERI-Rb-1 groups were significantly higher than those in the control group(all P＜0.001).The relative expression levels of CCNB1 and CDK1 mRNAs also increased significantly in the three groups,com-pared with those in the control group(all P＜0.01).There was no significant difference in the relative expression of SYK mRNAs between T-MYCN Y1 and control groups(P＞0.05).The relative expression level of RXRγ mRNAs was significantly higher in the T-MYCN Y1 group than that in the control group(P＜0.05).The relative expression levels of SYK and RXRγmRNAs in T-MYCN Y2 and WERI-Rb-1 groups were significantly increased,compared with those in the control group(all P＜0.05).GO enrichment analysis showed that these differentially-expressed proteins were enriched into protein complex assembly and mitochondria pathways.KEGG enrichment analysis revealed that the enriched pathways of these differential-ly-expressed proteins included carbon metabolism,metabolic pathway and fatty acid degradation.Both proteomics and Western blot analyses indicated that OTX2 expression levels were the highest in the WERI-Rb-1 group,second highest in the T-MYCN Y2 group,and the lowest in the T-MYCN Y1 group(all P＜0.01).According to qRT-PCR,the expression levels of OTX2 mRNAs in T-MYCN Y1,T-MYCN Y2 and WRI-Rb-1 cells with OTX2 knockdown were lower than those in empty vec-tor controls(all P＜0.05).The growth curve of cells showed that after knocking down OTX2 in the three groups of cells,both cell growth and proliferation ability decreased significantly(all P＜0.001).Conclusion During the development of retinal tumors induced by MYCN overexpression,cells gradually exhibit characteristics similar to WERI-Rb-1 cells,which are a typical RB cell line.OTX2 plays an important role in MYCN amplification or the growth and proliferation of highly ex-pressed RB.Targeting OTX2 may become a new research direction for the treatment of RB.