Expression Significance And Potential Biological Function Of MYBL2 In Diffuse Large B-Cell Lymphoma

Background:In China,lymphoma is one of the top ten malignant tumors with tumor-related mortality,of which Diffuse Large B Cell Lymphoma(DLBCL)has accounted for more than one-third.Although most patients with DLBCL benefit from standard first-line chemotherapy,one-third of patients will come across relapse or drug resistance.Therefore,extensive exploration of the molecular mechanism that may have participated the occurrence and development of DLBCL can provide new ideas for the diagnosis and treatment of it.MYBL2(Myeloblastosis Proto-oncogene Like 2)belongs to the transcription factor of Myb gene family,which is involved in the regulation of cell cycle,cell survival and cell differentiation.In recent years,studies related to MYBL2 have been found in a variety of solid tumors such as lung cancer,colorectal cancer,breast cancer,hepatocellular carcinoma,prostate cancer and ovarian cancer.However,there are few studies on the relationship between MYBL2 and malignant tumors of the lymphoid hematopoietic system.What’s more,no public reports have been discovered about the expression pattern of MYBL2 in DLBCL.This study amid not only to explore the expression of MYBL2 in DLBCL and analyze its significance,but also further explore the potential biological function of MYBL2 in DLBCL.Materials and Methods1.128 wax-embedded DLBCL tissue specimens and 28 lymph node reactive hyperplasia specimens between August 1,2016 and December 31,2019 were collected,and relevant clinical parameters of DLBCL patients were sorted.The 156 tissue samples were provided by the pathology department of the First Affiliated Hospital of Guangxi University of Chinese Medicine,the First Affiliated Hospital of Guangxi Medical University,and the Peoples Hospital of Guangxi Zhuang Autonomous Region.Immunohistochemistry(IHC)was used to detect the expression of MYBL2 in DLBCL.The relationship between MYBL2 and relevant clinical parameters of DLBCL patients was studied,and then the correlation between MYBL2 and related prognostic indicators Ki67,P53,CD30,C-myc,and Bcl-2 was also analyzed.2.Exploration of MYBL2 m RNA expression pattern in DLBCL tissues and the analysis of relationship between MYBL2 and clinical parameters based on the public database(1)The extraction of the MYBL2 m RNA expression data in DLBCL and control tissues in the database,and the analysis of the expression pattern of MYBL2 m RNA in DLBCL.(2)The extraction of the expression of MYBL2 in DLBCL and the clinical parameters of patients in the TCGA database,and the analysis of the differences of MYBL2 expression between the clinical parameter groups of patients.(3)The extraction of the C-myc m RNA expression data in DLBCL and control tissues in the database,and the correlation analysis of MYBL2 and C-myc m RNA expression.3.Exploration of the biological function mechanism of MYBL2 in DLBCL.(1)With the Bioconductor Limma software package,the gene datasets of the public gene database(including a total of 96 DLBCL tissue samples and 71non-tumor lymphoid tissue samples)was analyzed.The differentially expressed genes(DEGS)that are up-regulated or down-regulated in DLBCL and co-expression genes that are positively or negatively correlated with MYBL2 expression in DLBCL were obtained.MYBL2 was searched in the Cistrome Data Browser and the predicted target genes of MYBL2 were obtained.The intersection of DEGS,co-expressed gene and target gene collection was taken to obtain target genes sets of MYBL2 in DLBCL.GO function enrichment and KEGG pathway enrichment analysis were performed on the obtained gene sets.MYBK2 and genes appearing in the first two pathways of KEGG that are ordered according to the number of enriched genes and P<0.05 were analyzed by Protein-Protein Interaction(PPI).(2)The top hub genes were determined by the degree algorithm on Cyto Hubba,and the correlation between MYBL2 and hub genes were analyzed.Ch IP-seq data of was MYBL2 and hub genes was searched on Cistrome Data Browser further verified the relationship between MYBL2 and its target genes.Result1.MYBL2 protein expression in DLBCL and its relationship with clinical parameters(1)The positive rate of MYBL2 in the samples of 128 DLBCL tissues was71.1%(91/128),and in the samples of 28 lymph node reactive hyperplasia specimens was 32.1%(9/28).The positive expression rate of MYBL2 in DLBCL was significantly higher than that of control anti-lymph node hyperplasia tissue.Statistical analysis showed that there was a significant difference between the two groups(P<0.05).Moreover,MYBL2 has a higher positive rate in non-GCB DLBCL than GCB.(2)The expression of MYBL2 protein and C-myc protein was positively correlated and the difference was statistically significant(rs=0.198,P=0.037<0.05).2.MYBL2 m RNA expression in DLBCL and its relationship with clinical parameters.(1)The violin map of the gene datasets showed that the m RNA expression level of MYBL2 in DLBCL was significantly higher than that in non-tumor lymphoid tissues.The forest map showed that the Standard Mean Difference(SMD)of MYBL2 m RNA was 1.67(95%CI: 1.27-2.08),suggesting that MYBL2 was significantly up-regulated in DLBCL.The area under the curve(AUC)value of the Receiver Operating Characteristic(ROC)curve of a single gene dataset is greater than 0.7(p<0.05)and AUC of the Summary Receiver Operating Characteristic(SROC)curve = 0.96(95%CI: 0.94-0.98),indicating that MYBL2 has a strong ability in distinguish DLBCL from non-tumor lymphoid tissues.(2)There was no significant difference between the expression of MYBL2 m RNA in the TCGA database and the age,race,nationality,clinical stage,and tumor size of DLBCL patients(P>0.05).(3)Correlation analysis showed a positive correlation between MYBL2 and C-myc m RNA expression.3.The potential biological functions of MYBL2 in DLBCL(1)MYBL2 and its up-regulated target genes in DLBCL were enriched in cell cycle,Oocyte meiosis,Human T-cell leukemia virus 1 infection and other pathways.MYBL2 and its down-regulated target genes were enriched in Cytokine-cytokine receptor interaction,Viral protein interaction with cytokine and cytokine receptor,Endocytosis and other pathways.(2)The expression levels of MYBL2 and PLK1 in the gene datasets was positively correlated.There was a binding site for MYBL2 in the promoter region of PLK1.ConclusionsMYBL2 may act as a tumor-promoting factor that participatd and involved in the biological process of DLBCL by targeting PLK1 in the cell cycle pathway.