MYBL2 Expression Research Articles

MYBL2 Supports DNA Double Strand Break Repair in Hematopoietic Stem Cells.

Myelodysplastic syndromes (MDS) are a heterogeneous group of diseases characterized by blood cytopenias that occur as a result of somatic mutations in hematopoietic stem cells (HSC). MDS leads to ineffective hematopoiesis, and as many as 30% of patients progress to acute myeloid leukemia (AML). The mechanisms by which mutations accumulate in HSC during aging remain poorly understood. Here we identify a novel role for MYBL2 in DNA double-strand break (DSB) repair in HSC. In patients with MDS, low MYBL2 levels associated with and preceded transcriptional deregulation of DNA repair genes. Stem/progenitor cells from these patients display dysfunctional DSB repair kinetics after exposure to ionizing radiation (IR). Haploinsufficiency of Mybl2 in mice also led to a defect in the repair of DSBs induced by IR in HSC and was characterized by unsustained phosphorylation of the ATM substrate KAP1 and telomere fragility. Our study identifies MYBL2 as a crucial regulator of DSB repair and identifies MYBL2 expression levels as a potential biomarker to predict cellular response to genotoxic treatments in MDS and to identify patients with defects in DNA repair. Such patients with worse prognosis may require a different therapeutic regimen to prevent progression to AML.Significance: These findings suggest MYBL2 levels may be used as a biological biomarker to determine the DNA repair capacity of hematopoietic stem cells from patients with MDS and as a clinical biomarker to inform decisions regarding patient selection for treatments that target DNA repair.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/20/5767/F1.large.jpg Cancer Res; 78(20); 5767-79. ©2018 AACR.

Demethylzeylasteral inhibits glioma growth by regulating the miR-30e-5p/MYBL2 axis

Glioma is the most common and malignant form of primary brain tumour, and is characterised by high proliferation and extensive invasion and neurological destruction. Demethylzeylasteral (T-96), which is extracted from Tripterygium wilfordii, is considered to have immunosuppressive, anti-inflammatory and anti-angiogenic effects. Here, the anti-tumour effect of T-96 on glioma was evaluated. Our results demonstrated that T-96 significantly inhibited glioma cell growth and induced cell cycle arrest in G1 phase but did not induce apoptosis. Cell invasion and migration were dramatically suppressed after treatment with T-96. Almost all genes related to cell cycle and DNA replication were downregulated after treatment with T-96. Our results showed that miR-30e-5p was noticeably upregulated after T-96 treatment, and MYBL2, which is involved in cell cycle progression and is a target gene of miR-30e-5p, was significantly reduced in synchrony. Overexpression of MYBL2 partially rescued the T-96-induced inhibition of cell growth and proliferation. Moreover, a miR-30e-5p antagomir significantly reduced the upregulation of miR-30e-5p expression induced by T-96, leading to recovery of MYBL2 expression, and partially rescued the T-96-induced inhibition of cell growth and proliferation. More important, T-96 effectively upregulated miR-30e-5p expression and downregulated MYBL2 expression, thus inhibiting LN-229 cell tumour growth in a mouse model. These results indicated that T-96 might inhibit glioma cell growth by regulating the miR-30e-5p/MYBL2 axis. Our study demonstrated that T-96 might act as a promising agent for malignant glioma therapy.

High MYBL2 expression and transcription regulatory activity is associated with poor overall survival in patients with hepatocellular carcinoma

PurposeIn this study, we aimed to assess the association between MYBL2 expression/transcription regulatory activity (TRA) and overall survival (OS) in patients with primary hepatocellular carcinoma (HCC) and to explore the factors related to B-Myb TRA. Materials and methodsBioinformatic analysis was performed based on data from the cancer genome atlas-liver hepatocellular carcinoma (TCGA-LIHC) and the human protein atlas (HPA). ResultsThe death group in TCGA-LIHC had significantly higher MYBL2 RNA and exon expression than the censor group. The high MYBL2 RNA and exon expression groups had significantly worse OS (P<0.01). Univariate and multivariate analysis confirmed that high MYBL2 expression was an independent prognostic factor of unfavourable OS (HR=1.591, 95%CI: 1.119–2.262, P=0.01). One hundred and fourteen out of 188 primary HCC cases in TCGA-LIHC had elevated transcription of B-Myb's downstream genes. High B-Myb TRA was associated with poor OS (P=0.013). Elevated expression of MYBL2, LIN9, LIN52 and FOXM1 were related to the higher TRA of B-Myb in HCC. ConclusionHigh MYBL2 expression/TRA are associated with inferior OS in patients with primary HCC. Increased expression of MYBL2, LIN9, LIN52 and FOXM1 are related to higher TRA of B-Myb in HCC.

MicroRNA-30a suppresses non-small-cell lung cancer by targeting Myb-related protein B.

Non-small-cell lung cancer (NSCLC) is one of the leading causes of cancer mortality worldwide. A growing body of evidence indicates that microRNA (miR) have important and diverse roles in the proliferation, apoptosis and metastasis of human cancer cells. In the present study, the molecular regulation mechanism of miR-30a and its potential target, Myb-related protein B (MYBL2) was investigated in NSCLC. Reverse transcription-quantitative polymerase chain reaction results showed that miR-30a was significantly downregulated in NSCLC tissues compared with adjacent normal tissues (P<0.05). MYBL2 has a putative miR-30a target site in its 3'untranslated region according to previous data, prediction databases and TargetScan software. In the present study, a negative correlation was demonstrated between miR-30a and MYBL2 expression in NSCLC. Direct interaction between miR-30a and MYBL2 was also confirmed via a dual-luciferase reporter assay. miR-30a overexpression inhibited the growth of A549 and H460 cells via MTT and bromodeoxyuridine incorporation assays, whereas miR-30a downregulation promoted cell proliferation. In addition, miR-30a overexpression not only increased cell apoptosis and induced cell cycle arrest in A549 and H460 cell lines, but also attenuated tumor growth, and mRNA and protein expression levels of MYBL2. The present findings suggest that miR-30a may suppress NSCLC by targeting MYBL2.

Clinicopathologic features and prognostic implications of MYBL2 protein expression in pancreatic ductal adenocarcinoma

MYBL2 (B-MYB), a member of the MYB family of transcription factor genes, regulates the expression of genes in the process of tumorigenesis. Many studies have shown that MYBL2 is high expresssion in several human malignancies including pancreatic ductal adenocarcinoma (PDAC). However, its role in PDAC is still unclear. The present study is designed to investigate MYBL2 expression levels and prognostic significance in PDAC patients. We assessed MYBL2 expression level by immunohistochemistry in tumor tissues from 93 PDAC patients undergoing curative resection. The association of MYBL2 expression with clinicopathological parameters was evaluated by Pearson’s chi-square (χ2) test, Fisher’s exact test, and Spearman’s rank. Kaplan-Meier survival analysis and Cox proportional hazards models were used to estimate the effect of MYBL2 expression on survival. The expression of MYBL2 was significantly higher in PDAC cells compared with adjacent non-cancerous tissues (P=0.000). The overexpression of MYBL2 in the tumor tissues was significantly correlated with a higher T classification (p=0.002), peri-neural invasion (PNI) (p=0.013) and vital status (p=0.045). Kaplan-Meier analysis indicated that high MYBL2 expression was significantly associated with shorter overall survival times in PDAC patients. Moreover, univariate and multivariate analysis confirmed MYBL2 expression (P=0.010), histological grade (P=0.001) as independent prognostic factors in PDAC. These results suggested that overexpression of MYBL2 might serve as a novel prognostic biomarker in PDAC patients.

MYBL2 is a Potential Prognostic Marker that Promotes Cell Proliferation in Gallbladder Cancer

Background: Gallbladder cancer (GBC) is an aggressive and highly lethal biliary tract malignancy, with extremely poor prognosis. In the present study, we analyzed the potential involvement of MYBL2, a member of the Myb transcription factor family, in the carcinogenesis of human GBC. Methods: MYBL2 expression levels were measured in GBC and cholecystitis tissue specimens using quantitative real-time PCR (qRT-PCR) and immunohistochemical (IHC) assays. The effects of MYBL2 on cell proliferation and DNA synthesis were evaluated using Cell Counting Kit-8 assay (CCK-8), colony formation, and 5-ethynyl-2'-deoxyuridine (EdU) retention assay, flow cytometry analysis, western blot, and a xenograft model of GBC cells in nude mice. Results: MYBL2 expression was increased in GBC tissues and associated with histological differentiation, tumour invasion, clinical stage and unfavourable overall survival in GBC patients. The downregulation of MYBL2 expression resulted in the inhibition of GBC cell proliferation, and DNA replication in vitro, and the growth of xenografted tumours in nude mice. Conversely, MYBL2 overexpression resulted in the opposite effects. Conclusions: MYBL2 overexpression promotes GBC cell proliferation through the regulation of the cell cycle at the S and G2/M phase transitions. Thus, MYBL2 could serve as a potential prognostic and therapeutic biomarker in GBC patients.

MYBD employed by HY5 increases anthocyanin accumulation via repression of MYBL2 in Arabidopsis.

Photomorphogenesis is an essential program in plant development. This process is effected by the balanced cooperation of many factors under light and dark conditions. In a previous study, we showed that MYB hypocotyl elongation-related (MYBH) is involved in cell elongation. To expand our understanding of MYBH function, we performed a yeast two-hybrid assay and identified an MYB-like Domain transcription factor (MYBD). In this study, we investigated the function of MYBD, which is an MYBH homolog involved in anthocyanin accumulation. MYBD expression increased in response to light or cytokinin, and MYBD enhanced anthocyanin biosynthesis via repression of MYBL2, which encodes a transcription factor that has a negative effect on this process. In addition, MYBD binding in vivo to the MYBL2 promoter and the lower level of histone H3K9 acetylation at the upstream region of MYBL2 in MYBD over-expressing plants in comparison with wild-type plants imply that MYBD represses MYBL2 expression via an epigenetic mechanism. HY5 directly binds to the MYBD promoter, which indicates that MYBD acts on HY5-downstream in light- or cytokinin-triggered signaling pathways, leading to anthocyanin accumulation. Our results suggest that, although MYBD and MYBH are homologs, they act in opposite ways during plant photomorphogenesis, and these functions should be examined in further studies.

Study of the S427G polymorphism and of MYBL2 variants in patients with acute myeloid leukemia

Dysregulation of MYBL2 has been associated to tumorigenesis and the S427G polymorphism could induce partial inactivation of MYBL2, associating it with cancer risk. It has previously been shown that MYBL2 was over-expressed in some acute myeloid leukemias (AML), portending poor prognosis. However, to date no studies have investigated the S427G or other genetic variants of MYBL2 in AML. This study analyzed the S427G in 197 AML patients and 179 controls and screened the MYBL2 sequence in patients. In contrast to other studies in solid tumors, the S427G was not associated with the incidence of AML. This study detected four unannotated genetic alterations, of which the Q67X could be involved in MYBL2 dysfunction. Eight polymorphisms were identified, among which the rs73116571, located in a splicing region, was associated with higher incidence in AML and weaker MYBL2 expression, suggesting pre-disposition to AML. Additional functional studies should be performed to verify these genetic variations as possible targets in AML.

Adverse prognostic value of MYBL2 overexpression and association with microRNA-30 family in acute myeloid leukemia patients

The MYBL2 gene encodes a transcription factor implicated in cell proliferation and maturation whose amplification or overexpression has been associated with different human malignancies, suggesting that it could be implicated in tumorigenesis. We analyzed MYBL2 expression and its prognostic value in 291 patients with de novo acute myeloid leukemia (AML) and we also evaluated its association with microRNAs 29 and 30 families. MYBL2 expression in AML patients was increased relative to CD34+ cells. Moreover, MYBL2 overexpression was associated with lower expression of miR-30a (P=0.024), miR-30b (P=0.021) and miR-30c (P=0.009). Multivariate analysis showed that MYBL2 expression was an independent factor for disease-free survival (HR 3.0, 95% CI 1.5-6.0, P=0.002) and cumulative incidence of relapse (HR 2.6, 95% CI 1.2-5.6, P=0.015) in patients with an intermediate-risk karyotype. In conclusion, our data showed that MYBL2 expression analysis could be useful to define subgroups of patients with poor prognosis.

MYBL2 is a sub-haploinsufficient tumor suppressor gene in myeloid malignancy.

A common deleted region (CDR) in both myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN) affects the long arm of chromosome 20 and has been predicted to harbor a tumor suppressor gene. Here we show that MYBL2, a gene within the 20q CDR, is expressed at sharply reduced levels in CD34+ cells from most MDS cases (65%; n = 26), whether or not they harbor 20q abnormalities. In a murine competitive reconstitution model, Mybl2 knockdown by RNAi to 20-30% of normal levels in multipotent hematopoietic progenitors resulted in clonal dominance of these 'sub-haploinsufficient' cells, which was reflected in all blood cell lineages. By 6 months post-transplantation, the reconstituted mice had developed a clonal myeloproliferative/myelodysplastic disorder originating from the cells with aberrantly reduced Mybl2 expression. We conclude that downregulation of MYBL2 activity below levels predicted by classical haploinsufficiency underlies the clonal expansion of hematopoietic progenitors in a large fraction of human myeloid malignancies. DOI:http://dx.doi.org/10.7554/eLife.00825.001.

Mybl2 expression is under genetic control and contributes to determine a hepatocellular carcinoma susceptible phenotype

MYBL2 is implicated in human malignancies and over expressed in hepatocellular carcinoma (HCC). We investigated Mybl2 role in the acquisition of susceptibility to HCC and tumor progression. MYBL2 mRNA and protein levels were evaluated by quantitative RT-PCR and immunoblotting, respectively. MYBL2 expression in HCC cell lines was controlled through MYBL2 cDNA or anti-MYBL2 siRNA transfection. Gene expression profile of cells transfected with MYBL2 was analyzed by microarray. Low induction of Mybl2 and its target Clusterin mRNAs, in low-grade dysplastic nodules (DN), progressively increased in fast growing high-grade DN and HCC of F344 rats, susceptible to hepatocarcinogenesis, whereas no/lower increases occurred in slow growing lesions of resistant BN rats. Highest Mybl2 protein activation, prevalently nuclear, occurred in F344 than BN lesions. Highest Mybl2, Clusterin, Cdc2, and Cyclin B1 expression occurred in fast progressing DN and HCC of E2f1 transgenics, compared to c-Myc transgenics, and anti-Mybl2 siRNA had highest anti-proliferative and apoptogenic effects in cell lines from HCC of E2f1 transgenics. MYBL2 transfected HepG2 and Huh7 cells exhibited increased cell proliferation and G1-S and G2-M cell cycle phases. The opposite occurred when MYBL2 was silenced by specific siRNA. MYBL2 transfection in Huh7 cells led to upregulation of genes involved in signal transduction, cell proliferation, cell motility, and downregulation of oncosuppressor and apoptogenic genes. mybl2 expression and activation are under genetic control. Mybl2 upregulation induces fast growth and progression of premalignant and malignant liver, through cell cycle deregulation and activation of genes and pathways related to tumor progression.

MYBL2 is a new regulator of flavonoid biosynthesis in Arabidopsis thaliana

In Arabidopsis thaliana, several MYB and basic helix-loop-helix (BHLH) proteins form ternary complexes with TTG1 (WD-Repeats) and regulate the transcription of genes involved in anthocyanin and proanthocyanidin (PA) biosynthesis. Similar MYB-BHLH-WDR (MBW) complexes control epidermal patterning and cell fates. A family of small MYB proteins (R3-MYB) has been shown to play an important role in the regulation of epidermal cell fates, acting as inhibitors of the MBW complexes. However, so far none of these small MYB proteins have been demonstrated to regulate flavonoid biosynthesis. The genetic and molecular analyses presented here demonstrated that Arabidopsis MYBL2, which encodes a R3-MYB-related protein, is involved in the regulation of flavonoid biosynthesis. The loss of MYBL2 activity in the seedlings of two independent T-DNA insertion mutants led to a dramatic increase in the accumulation of anthocyanin. In addition, overexpression of MYBL2 in seeds inhibited the biosynthesis of PAs. These changes in flavonoid content correlate well with the increased level of mRNA of several structural and regulatory anthocyanin biosynthesis genes. Interestingly, transient expression analyses in A. thaliana cells suggested that MYBL2 interacts with MBW complexes in planta and directly modulates the expression of flavonoid target genes. These results are fully consistent with the molecular interaction of MYBL2 with BHLH proteins observed in yeast. Finally, MYBL2 expression studies, including its inhibition by light-induced stress, allowed us to hypothesise a physiological role for MYBL2. Taken together, these results bring new insights into the transcriptional regulation of flavonoid biosynthesis and provide new clues and tools for further investigation of its developmental and environmental regulation.

Activation of B‐Myb by E2F1 in hepatocellular carcinoma

Deregulation of E2F1 transcriptional activity is observed in a variety of cancers, including hepatocellular carcinoma (HCC). The aim of the present study is to identify transcriptional target genes of E2F1 in HCC. We determined expression levels for E2F1 and ten candidate genes thought to be targets of E2F1 in primary HCCs using a real-time quantitative reverse transcription-PCR assay. Following small interfering RNA (siRNA)-mediated knockdown of E2F1 in HCC cell lines, we quantified mRNA levels of the candidate E2F1 target genes. E2F1 was significantly over-expressed in 41 primary HCCs as compared to non-tumorous liver tissues. Among the candidates, MYBL2, whose product is the transcriptional factor B-Myb, which is involved in controlling cell-cycle progression and apoptosis, was significantly over-expressed in primary HCCs. Additionally, expression levels of MYBL2 correlated with those of E2F1. Knockdown of E2F1 resulted in a decrease in expression of MYBL2. A copy-number gain for MYBL2 was observed in 36 of 66 primary HCCs, suggesting that MYBL2 expression is up-regulated by amplification in addition to being regulated by E2F1. Moreover, siRNA-mediated knockdown of MYBL2 led to reduced expression of CDC2 (which encodes CDC2), cyclin A2 (CCNA2), and topoisomerase II alpha (TOP2A), implicating these genes in the cell cycle and suggesting that they may be downstream targets of B-Myb. MYBL2 is a probable transcriptional target of E2F1 in HCC and may therefore be a useful biomarker for diagnosis and an attractive target for molecular therapies useful to treat HCC.