OBJECTIVES: Acute myeloid leukemia (AML) is a heterogeneous and highly recurrent hematological malignancy. Studies have shown an association between microRNAs and drive genes in AMLs. However, the regulatory roles of miRNAs in AML and how they act on downstream targets and the signaling pathway has been little studied.
METHODS: As to understand the mechanism of mRNA-miRNA interaction in the blood malignancy from a large scale of transcriptomic sequencing studies, we applied a comprehensive miRNA-mRNA association, co-expression gene network and ingenuity pathway analysis using TCGA AML datasets.
RESULTS: Our results showed that his-mir-335 was a critical regulatory of homeobox A gene family. PBX3, KAT6A, MEIS1, and COMMD3-BMI1 were predicted as top transcription regulators in the regulatory network of the HOXA family. The most significantly enriched functions were cell growth, proliferation, and survival in the mRNA-miRNA network.
CONCLUSION: Our work revealed that regulation of the HOXA gene family and its regulation played an important role in the development of AML.

As the second most common malignant bone tumor in children and adolescents, Ewing sarcoma is initiated and exacerbated by a chimeric oncoprotein, most commonly, EWS-FLI1. In this study, we apply epigenomic analysis to characterize the transcription dysregulation in this cancer, focusing on the investigation of super-enhancer and its associated transcriptional regulatory mechanisms. We demonstrate that super-enhancer-associated transcripts are significantly enriched in EWS-FLI1 target genes, contribute to the aberrant transcriptional network of the disease, and mediate the exceptional sensitivity of Ewing sarcoma to transcriptional inhibition. Through integrative analysis, we identify MEIS1 as a super-enhancer-driven oncogene, which co-operates with EWS-FLI1 in transcriptional regulation, and plays a key pro-survival role in Ewing sarcoma. Moreover, APCDD1, another super-enhancer-associated gene, acting as a downstream target of both MEIS1 and EWS-FLI1, is also characterized as a novel tumor-promoting factor in this malignancy. These data delineate super-enhancer-mediated transcriptional deregulation in Ewing sarcoma, and uncover numerous candidate oncogenes which can be exploited for further understanding of the molecular pathogenesis for this disease.

Endothelin receptor type A (EDNRA) is known as a mediator of cell proliferation and survival. Aberrant regulation of EDNRA has been shown to play a role in tumor growth and metastasis. Using a global gene expression screen, we found that expression of Ednra was upregulated in murine leukemia inducing cells co-expressing Hoxa9 and Meis1 compared to cells only expressing Hoxa9. The aim of this study was to explore the role of Ednra in leukemogenesis further. In a murine bone marrow transplantation model, mice transplanted with cells overexpressing Ednra and Hoxa9 succumbed to leukemia significantly earlier than mice transplanted with cells overexpressing Hoxa9 only. Furthermore, overexpression of Ednra led to increased proliferation and resistance to apoptosis of bone marrow cells in vitro. We could also show that Meis1 binds to the Ednra promoter region, suggesting a regulatory role for Meis1 in Ednra expression. Taken together, our results suggest a role for Ednra in Hoxa9/Meis1-driven leukemogenesis.

Aberrant expression of HOXA9 is a prominent feature of acute leukemia driven by diverse oncogenes. Here we show that HOXA9 overexpression in myeloid and B progenitor cells leads to significant enhancer reorganizations with prominent emergence of leukemia-specific de novo enhancers. Alterations in the enhancer landscape lead to activation of an ectopic embryonic gene program. We show that HOXA9 functions as a pioneer factor at de novo enhancers and recruits CEBPα and the MLL3/MLL4 complex. Genetic deletion of MLL3/MLL4 blocks histone H3K4 methylation at de novo enhancers and inhibits HOXA9/MEIS1-mediated leukemogenesis in vivo. These results suggest that therapeutic targeting of HOXA9-dependent enhancer reorganization can be an effective therapeutic strategy in acute leukemia with HOXA9 overexpression.

NPM1 is the most frequently mutated gene in cytogenetically normal acute myeloid leukemia (AML). In AML cells, NPM1 mutations result in abnormal cytoplasmic localization of the mutant protein (NPM1c); however, it is unknown whether NPM1c is required to maintain the leukemic state. Here, we show that loss of NPM1c from the cytoplasm, either through nuclear relocalization or targeted degradation, results in immediate downregulation of homeobox (HOX) genes followed by differentiation. Finally, we show that XPO1 inhibition relocalizes NPM1c to the nucleus, promotes differentiation of AML cells, and prolongs survival of Npm1-mutated leukemic mice. We describe an exquisite dependency of NPM1-mutant AML cells on NPM1c, providing the rationale for the use of nuclear export inhibitors in AML with mutated NPM1.

BACKGROUND: It has been shown that the expression of potassium channel tetramerization domain containing 12 (KCTD12) as a regulator of GABAB receptor signaling is reversely associated with gastrointestinal stromal tumors. In present study we examined the probable role of KCTD12 in regulation of several signaling pathways and chromatin remodelers in esophageal squamous cell carcinoma (ESCC).
METHODS: KCTD12 ectopic expression was done in KYSE30 cell line. Comparative quantitative real time PCR was used to assess the expression of stem cell factors and several factors belonging to the WNT/NOTCH and chromatin remodeling in transfected cells in comparison with non-transfected cells.
RESULTS: We observed that the KCTD12 significantly down regulated expression of NANOG, SOX2, SALL4, KLF4, MAML1, PYGO2, BMI1, BRG1, MSI1, MEIS1, EGFR, DIDO1, ABCC4, ABCG2, and CRIPTO1 in transfected cells in comparison with non-transfected cells. Migration assay showed a significant decrease in cell movement in ectopic expressed cells in comparison with non-transfected cells (p = 0.02). Moreover, KCTD12 significantly decreased the 5FU resistance in transfected cells (p = 0.01).
CONCLUSIONS: KCTD12 may exert its inhibitory role in ESCC through the suppression of WNT /NOTCH, stem cell factors, and chromatin remodelers and can be introduced as an efficient therapeutic marker.

A series of novel pyrimidylaminoquinoline derivatives 8(a-i) and 9(a-i) containing amino side chain, and the bisaminoquinoline analogs 3(b-e) have been designed and synthesized by structural modifications on a lead DOT1L inhibitor, 3a. All the compounds have been evaluated for their DOT1L inhibitory activities. The results showed that most of the compounds have strong anti DOT1L activities. Compounds 3e, 8h and 9e are the most potential ones from each category with the IC

The 11q23 of the mixed lineage leukemia 1 (

CD8+ T-lymphocytes infiltration is a favorable prognostic marker in ovarian cancer. Recently we identified MEIS1 as a gene overexpressed in early stage ovarian tumors enriched for CD8+ T-cells. Here, we report the molecular mechanism of the homeodomain transcription factor MEIS1 in lymphocyte recruitment. We validated that MEIS1 expression is a positive predictor of CD8+ T cells in early stage ovarian cancer. We showed that MEIS1 induces the expression of CCL18, CCL4, CXCL7, CCL5, CXCL1, and IL8 chemokines in cancer cells followed by their secretion in the culture medium ultimately triggering CD8+ T-lymphocyte recruitment in vitro. Knock down of MEIS1 expression by siRNA resulted in downregulation of these chemokines. We verified that MEIS1 binds to the promoters of chemokine genes, both in vitro and in vivo. We also showed that the expression levels of MEIS1 correlated tightly with the mRNA levels of chemokines CCL4 and CCL18 in early stage ovarian cancer patient samples and served as a positive prognostic marker, as shown by Kaplan-Meyer survival analysis. In conclusion, we propose that MEIS1 plays a pivotal role in the regulatory circuitry governing T-cell chemo-attraction during the early stages of ovarian cancer.

Purpose Dysregulated microRNAs are implicated in the pathogenesis and aggressiveness of acute myeloid leukemia (AML). We describe the effect of the hematopoietic stem-cell self-renewal regulating miR-193b on progression and prognosis of AML. Methods We profiled miR-193b-5p/3p expression in cytogenetically and clinically characterized de novo pediatric AML (n = 161) via quantitative real-time polymerase chain reaction and validated our findings in an independent cohort of 187 adult patients. We investigated the tumor suppressive function of miR-193b in human AML blasts, patient-derived xenografts, and miR-193b knockout mice in vitro and in vivo. Results miR-193b exerted important, endogenous, tumor-suppressive functions on the hematopoietic system. miR-193b-3p was downregulated in several cytogenetically defined subgroups of pediatric and adult AML, and low expression served as an independent indicator for poor prognosis in pediatric AML (risk ratio ± standard error, -0.56 ± 0.23; P = .016). miR-193b-3p expression improved the prognostic value of the European LeukemiaNet risk-group stratification or a 17-gene leukemic stemness score. In knockout mice, loss of miR-193b cooperated with Hoxa9/Meis1 during leukemogenesis, whereas restoring miR-193b expression impaired leukemic engraftment. Similarly, expression of miR-193b in AML blasts from patients diminished leukemic growth in vitro and in mouse xenografts. Mechanistically, miR-193b induced apoptosis and a G1/S-phase block in various human AML subgroups by targeting multiple factors of the KIT-RAS-RAF-MEK-ERK (MAPK) signaling cascade and the downstream cell cycle regulator CCND1. Conclusion The tumor-suppressive function is independent of patient age or genetics; therefore, restoring miR-193b would assure high antileukemic efficacy by blocking the entire MAPK signaling cascade while preventing the emergence of resistance mechanisms.

OBJECTIVE: MLL gene is involved in more than 80 known genetic fusions in acute leukemia. To study the relevance of MLL partner gene and selected gene's expression, in this work, we have studied a cohort of 20 MLL-rearranged acute myeloid leukemia (AML).
METHODS: Twenty MLL-rearranged AML patients along with a control cohort of 138 AML patients are included in this work. By RT-PCR and sequencing, MLL genetic fusion was characterized, and relative gene expression quantification was carried out for EVI1, MEIS1, MLL-3', RUNX1, SETBP1, HOXA5, and FLT3 genes. Risk stratification and association of MLL genetic partner and gene expression to overall survival, in the context of received therapy, were performed.
RESULTS: MLLr cohort showed to have an OS more similar to intermediate-risk AML. Type of MLL genetic partner showed to be relevant in allo-HSCT response; having MLLT1 and MLLT3, a better benefit from it. Expression of MLL-3' region, EVI1 and FLT3, showed association with OS in patients undergoing allo-HSCT.
CONCLUSION: We show that the MLL genetic partner could have implications in allo-HSCT response, and we propose three genes whose expression could be useful for the prognosis of this leukemia in patients undergoing allo-HSCT: 3' region of MLL, EVI1, and FLT3.

In the present work we aimed to identify targetable signaling networks in human MLL-AF9 leukemias. We show that MLL-AF9 cells critically depend on FLT3-ligand induced pathways as well as on BRD3/4 for their survival. We evaluated the in vitro and in vivo efficacy of the BRD3/4 inhibitor I-BET151 in various human MLL-AF9 (primary) models and patient samples and analyzed the transcriptome changes following treatment. To further understand the mode of action of BRD3/4 inhibition, we performed ChIP-seq experiments on the MLL-AF9 complex in THP1 cells and compared it to RNA-seq data of I-BET151 treated cells. While we could confirm a consistent and specific downregulation of key-oncogenic drivers such as MYC and BCL2, we found that the majority of I-BET151-responsive genes were not direct MLL-AF9 targets. In fact, MLL-AF9 specific targets such as the HOXA cluster, MEIS1 and other cell cycle regulators such as CDK6 were not affected by I-BET151 treatment. Furthermore, we also highlight how MLL-AF9 transformed cells are dependent on the function of non-mutated hematopoietic transcription factors and tyrosine kinases such as the FLT3-TAK1/NF-kB pathway, again impacting on BCL2 but not on the HOXA cluster. We conclude that BRD3/4 and the FLT3-TAK1/NF-kB pathways collectively control a set of targets that are critically important for the survival of human MLL-AF9 cells.

Micro-ribonucleic acid-155 (miR-155) is one of the first described oncogenic miRNAs. Although multiple direct targets of miR-155 have been identified, it is not clear how it contributes to the pathogenesis of acute myeloid leukemia. We found miR-155 to be a direct target of Meis1 in murine Hoxa9/Meis1 induced acute myeloid leukemia. The additional overexpression of miR-155 accelerated the formation of acute myeloid leukemia in Hoxa9 as well as in Hoxa9/Meis1 cells

Eleven-nineteen leukemia (ENL) is a chromatin reader present in complexes stimulating transcriptional elongation. It is fused to mixed-lineage leukemia (MLL) in leukemia, and missense mutations have been identified in Wilms tumor and acute myeloid leukemia. Here we demonstrate that ENL overcomes polycomb silencing through recruitment of PAF1 via the conserved YEATS domain, which recognizes acetylated histone H3. PAF1 was responsible for antirepressive activities of ENL in vitro, and it determined the transforming potential of MLL-ENL. MLL-ENL target loci showed supraphysiological PAF1 binding, hyperubiquitination of histone H2B and hypomodification with H2AUb, resulting in accelerated transcription rates. YEATS mutations induced a gain of function, transforming primary hematopoietic cells in vitro and in transplantation assays through aberrant transcription and H2B ubiquitination of

Protein Arginine Methyltransferases (PRMTs) are crucial players in diverse biological processes, and dysregulation of PRMTs has been linked to various human diseases, especially cancer. Therefore, small molecules targeting PRMTs have profound impact for both academic functional studies and clinical disease treatment. Here, we report the discovery of N

Acute myeloid leukemia (AML) is a disease associated with epigenetic dysregulation. 11q23 translocations involving the H3K4 methyltransferase MLL1 (KMT2A) generate oncogenic fusion proteins with deregulated transcriptional potential. The polymerase-associated factor complex (PAFc) is an epigenetic co-activator complex that makes direct contact with MLL fusion proteins and is involved in AML, however, its functions are not well understood. Here, we explored the transcriptional targets regulated by the PAFc that facilitate leukemia by performing RNA-sequencing after conditional loss of the PAFc subunit Cdc73. We found Cdc73 promotes expression of an early hematopoietic progenitor gene program that prevents differentiation. Among the target genes, we confirmed the protein arginine methyltransferase Prmt5 is a direct target that is positively regulated by a transcriptional unit that includes the PAFc, MLL1, HOXA9 and STAT5 in leukemic cells. We observed reduced PRMT5-mediated H4R3me2s following excision of Cdc73 placing this histone modification downstream of the PAFc and revealing a novel mechanism between the PAFc and Prmt5. Knockdown or pharmacologic inhibition of Prmt5 causes a G1 arrest and reduced proliferation resulting in extended leukemic disease latency in vivo. Overall, we demonstrate the PAFc regulates Prmt5 to facilitate leukemic progression and is a potential therapeutic target for AMLs.

BACKGROUND: Cytogenetic aberrations and gene mutations have long been regarded as independent prognostic markers in AML, both of which can lead to misexpression of some key genes related to hematopoiesis. It is believed that the expression level of the key genes is associated with the treatment outcome of AML.
METHODS: In this study, we analyzed the clinical features and molecular aberrations of 560 newly diagnosed non-M3 AML patients, including mutational status of CEBPA, NPM1, FLT3, C-KIT, NRAS, WT1, DNMT3A, MLL-PTD and IDH1/2, as well as expression levels of MECOM, ERG, GATA2, WT1, BAALC, MEIS1 and SPI1.
RESULTS: Certain gene expression levels were associated with the cytogenetic aberration of the disease, especially for MECOM, MEIS1 and BAALC. FLT3, C-KIT and NRAS mutations contained conversed expression profile regarding MEIS1, WT1, GATA2 and BAALC expression, respectively. FLT3, DNMT3A, NPM1 and biallelic CEBPA represented the mutations associated with the prognosis of AML in our group. Higher MECOM and MEIS1 gene expression levels showed a significant impact on complete remission (CR) rate, disease free survival (DFS) and overall survival (OS) both in univariate and multivariate analysis, respectively; and an additive effect could be observed. By systematically integrating gene mutational status results and gene expression profile, we could establish a more refined system to precisely subdivide AML patients into distinct prognostic groups.
CONCLUSIONS: Gene expression abnormalities contained important biological and clinical informations, and could be integrated into current AML stratification system.

BACKGROUND: In chronic lymphocytic leukemia (CLL), epigenomic and genomic studies have expanded the existing knowledge about the disease biology and led to the identification of potential biomarkers relevant for implementation of personalized medicine. In this study, an attempt has been made to examine and integrate the global DNA methylation changes with gene expression profile and their impact on clinical outcome in early stage CLL patients.
RESULTS: The integration of DNA methylation profile (
CONCLUSIONS: The DNA methylation changes associated with mRNA expression of

Gastric cancer (GC) is one of the most incident malignancies in the world. Although lots of featured genes and microRNAs (miRNAs) have been identified to be associated with gastric carcinogenesis, underlying regulatory mechanisms still remain unclear. In order to explore the dysfunctional mechanisms of GC, we developed a novel approach to identify carcinogenesis relevant regulatory relationships, which is characterized by quantifying the difference of regulatory relationships between stages. Firstly, we applied the strategy of differential coexpression analysis (DCEA) to transcriptomic datasets including paired mRNA and miRNA of gastric samples to identify a set of genes/miRNAs related to gastric cancer progression. Based on these genes/miRNAs, we constructed conditional combinatorial gene regulatory networks (cGRNs) involving both transcription factors (TFs) and miRNAs. Enrichment of known cancer genes/miRNAs and predicted prognostic genes/miRNAs was observed in each cGRN. Then we designed a quantitative method to measure differential regulation level of every regulatory relationship between normal and cancer, and the known cancer genes/miRNAs proved to be ranked significantly higher. Meanwhile, we defined differentially regulated link (DRL) by combining differential regulation, differential expression and the regulation contribution of the regulator to the target. By integrating survival analysis and DRL identification, three master regulators TCF7L1, TCF4, and MEIS1 were identified and testable hypotheses of dysfunctional mechanisms underlying gastric carcinogenesis related to them were generated. The fine-tuning effects of miRNAs were also observed. We propose that this differential regulation network analysis framework is feasible to gain insights into dysregulated mechanisms underlying tumorigenesis and other phenotypic changes.

Homeobox (HOX) transcription factors and NOTCH signaling pathway are critical regulators of stem cell functions, cell fate in development and homeostasis of gastrointestinal tissues. In the present study, we analyzed cross talk between NOTCH pathway and HOX genes through assessment of probable correlation betweenMAML1 and MEIS1 as the main transcription factor of NOTCH pathway and enhancer of HOX transcriptional machinery, respectively in esophageal squamous cell carcinoma (ESCC) patients. Fifty one ESCC cases were enrolled to assess the levels of Meis1 and Maml1 mRNA expression using real-time polymerase chain reaction (PCR). Only 3 out of 51 (5.9%) cases had MEIS1/MAML1 under expression and 2/51 (3.9%) cases had MEIS1/MAML1over expression. Nine out of 51 samples (17.6%) have shown MEIS1 under expression and MAML1 over expression. There was a significant correlation between MAML1and MEIS1mRNA expressions (p ≤ 0.05). There were significant correlations between MEIS1 under/MAML1 over expressed cases and tumor location (p = 0.05), tumor depth of invasion (p = 0.011), and sex (p = 0.04). Our results showed that MEIS1 may have a negative role in regulation of MAML1expression during the ESCC progression.

Interaction of HOXA9/MEIS1/PBX3 is responsible for hematopoietic system transformation in MLL-rearranged (MLL-r) leukemia. Of these genes, HOXA9 has been shown to be critical for leukemia cell survival, while MEIS1 has been identified as an essential regulator for leukemia stem cell (LSC) maintenance. Although significantly high expression of PBX3 was observed in clinical acute myeloid leukemia (AML) samples, the individual role of PBX3 in leukemia development is still largely unknown. In this study, we explored the specific role of PBX3 and its associated regulatory network in leukemia progression. By analyzing the clinical database, we found that the high expression of PBX3 is significantly correlated with a poor prognosis in AML patients. ChIP-Seq/qPCR analysis in MLL-r mouse models revealed aberrant epigenetic modifications with increased H3K79me2, and decreased H3K9me3 and H3K27me3 levels in LSCs, which may account for the high expression levels of Pbx3. To further examine the role of Pbx3 in AML maintenance and progression, we used the CRISPR/Cas9 system to delete Pbx3 in leukemic cells in the MLL-AF9 induced AML mouse model. We found that Pbx3 deletion significantly prolonged the survival of leukemic mice and decreased the leukemia burden by decreasing the capacity of LSCs and promoting LSC apoptosis. In conclusion, we found that PBX3 is epigenetically aberrant in the LSCs of MLL-r AML and is essential for leukemia development. Significantly, the differential expression of PBX3 in normal and malignant hematopoietic cells suggests PBX3 as a potential prognostic marker and therapeutic target for MLL-r leukemia.

The transcription factor Meis1 drives myeloid leukemogenesis in the context of Hox gene overexpression but is currently considered undruggable. We therefore investigated whether myeloid progenitor cells transformed by Hoxa9 and Meis1 become addicted to targetable signaling pathways. A comprehensive (phospho)proteomic analysis revealed that Meis1 increased Syk protein expression and activity. Syk upregulation occurs through a Meis1-dependent feedback loop. By dissecting this loop, we show that Syk is a direct target of miR-146a, whose expression is indirectly regulated by Meis1 through the transcription factor PU.1. In the context of Hoxa9 overexpression, Syk signaling induces Meis1, recapitulating several leukemogenic features of Hoxa9/Meis1-driven leukemia. Finally, Syk inhibition disrupts the identified regulatory loop, prolonging survival of mice with Hoxa9/Meis1-driven leukemia.

BACKGROUND: Myeloid ecotropic viral integration site 1 (MEIS1) protein plays a synergistic causative role in acute myeloid leukemia (AML). However, MEIS1 has also shown to be a potential tumor suppressor in some other cancers, such as non-small-cell lung cancer (NSCLC) and prostate cancer. Although multiple roles of MEIS1 in cancer development and progression have been identified, there is an urgent demand to discover more functions of this molecule for further therapeutic design.
METHODS: MEIS1 was overexpressed via adenovirus vector in clear cell renal cell carcinoma (ccRCC) cells. Western blot and real-time qPCR (quantitative Polymerase Chain Reaction) was performed to examine the protein and mRNA levels of MEIS1. Cell proliferation, survival, in vitro migration and invasion were tested by MTT, colony formation, soft-agar, transwell (in vitro invasion/migration) assays, and tumor in vivo growthwas measured on nude mice model. In addition, flow-cytometry analysis was used to detect cell cycle arrest or non-apoptotic cell death of ccRCC cells induced by MEIS1.
RESULTS: MEIS1 exhibits a decreased expression in ccRCC cell lines than that in non-tumor cell lines. MEIS1 overexpression inhibits ccRCC cells proliferation and induces G1/S arrest concomitant with marked reduction of G1/S transition regulators, Cyclin D1 and Cyclin A. Moreover, MEIS1-1 overexpression also induces non-apoptotic cell death of ccRCC cells via decreasing the levels of pro-survival regulators Survivin and BCL-2. Transwell migration assay (TMA) shows that MEIS1 attenuates in vitro invasion and migration of ccRCC cells with down-regulated epithelial-mesenchymal transition (EMT) process. Further, in nude mice model, MEIS1 inhibits the in vivo growth of Caki-1 cells.
CONCLUSIONS: By investigating the role of MEIS1 in ccRCC cells' survival, proliferation, anchorage-independent growth, cell cycle progress, apoptosis and metastasis, in the present work, we propose that MEIS1 may play an important role in clear cell renal cell carcinoma (ccRCC) development.

Although the outcome of patients with acute myeloid leukemia (AML) has improved by optimized chemotherapy regimens and bone marrow transplantation, leukemia relapse remains one of the most challenging problems during therapy. Sustained existence of AML blasts is a fundamental determinant for the development of leukemia and resistance to therapy. Recent evidences suggest that Meis1 is tightly associated with the self-renewal capacity of normal hematopoietic stem cells. Meis1 was also found to be essential for the development of mixed lineage leukemia (MLL)-rearranged leukemia. Whether Meis1 functions independently of MLL abnormality in the context of leukemia is unclear. Herein, we identified a distinct expression pattern of Meis1 in patients with newly diagnosed AML without MLL abnormality. High levels of Meis1 expression were found in 64 of 95 (67.4%) AML patients; whereas, 31 of 95 (32.6%) patients showed dramatically lower levels of Meis1, compared with the median level of Meis1 in healthy donors. The whole cohort and subgroup analyses further demonstrated that high Meis1 expression levels were associated with a resistance to conventional chemotherapy, compared with the group with low Meis1 levels (P = 0.014 and P = 0.029, respectively). In vitro knockdown experiments highlighted a role of Meis1 in regulating maintenance and survival of human AML cells. These results implicate that Meis1 functions as an important regulator during the progression of human AML and could be a prognostic factor independent of MLL abnormality.

MicroRNA-155 (miR-155) is an oncogenic miRNA upregulated in various tumor types and leukemias and has been suggested as a potential drug target. Based on our previous work detecting high miR-155 levels in response to Meis1 overexpression in a murine Hox leukemia model, we show here the relationship among HOXA9, MEIS1, and miR-155 levels in MLL-translocated acute myeloid leukemia (AML) patients. Using mouse bone marrow cells transformed by MLL-fusion genes expressing graduated levels of Meis1, we show a positive correlation between miR-155 and Meis1. However, using a miR-155-knockout mouse model, we show that the absence and the depletion of miR-155 have no effect on leukemia formation or progression. We also show for the first time that miR-155 levels are correlated with MLL translocations, but that miR-155 expression is dispensable for the formation of AML and has no effect on leukemia progression.

HOXA9, MEIS1 and FLT3 are genes frequently upregulated in human acute myeloid leukemia. Hoxa9 and Meis1 also cooperate to induce aggressive AML with high Flt3 expression in mice, suggesting an important role for Flt3 in Hoxa9/Meis1-induced leukemogenesis. To define the role of Flt3 in AML with high Hoxa9/Meis1, we treated mice with Hoxa9/Meis1-induced AML with the Flt3 inhibitor AC220, used an Flt3-ligand (FL-/-) knockout model, and investigated whether overexpression of Flt3 could induce leukemia together with overexpression of Hoxa9. Flt3 inhibition by AC220 did not delay AML development in mice transplanted with bone marrow cells overexpressing Hoxa9 and Meis1. In addition, Hoxa9/Meis1 cells induced AML in FL-/- mice as rapid as in wild-type mice. However, FL-/- mice had reduced organ infiltration compared with wild-type mice, suggesting some Flt3-dependent effect on leukemic invasiveness. Interestingly, leukemic Hoxa9/Meis1 cells from sick mice expressed high levels of Flt3 regardless of presence of its ligand, showing that Flt3 is a passive marker on these cells. In line with this, combined engineered overexpression of Flt3 and Hoxa9 did not accelerate the progression to AML. We conclude that the Hoxa9- and Meis1-associated upregulation of Flt3 is not a requirement for leukemic progression induced by Hoxa9 and Meis1.

SOX1, as a tumor suppressor, play anti-tumorigenecity role in different cells and its expression is inhibited in a variety of cancers. The aim of this study was to evaluate SOX1 expression and its correlation with cancer stem cell (CSC) markers in ESCC. Using real time PCR, the relative comparative expression of SOX1 in 40 ESCC samples was assessed compared to related margin normal tissues, and its correlation with CSC markers including SALL4, SOX2, and MEIS1 was analyzed statistically. The results revealed significant under-expression of SOX1 in ESCC in significant correlation with different indices of poor prognosis including depth of tumor invasion (P=0.02), Stage of tumor cell progression (P=0.05), and number of involved lymph node metastasis (P=0.05). Furthermore, the under-expression of SOX1 was associated significantly with SALL4 overexpression. This study was the first to evaluate SOX1 underexpression and its association with poor prognosis in ESCC. Since correlation of SOX1 and SALL4 was detected in advanced stages of ESCC progression, as well as high invasive and aggressive tumor tissues, it may be extrapolated that SOX1 expression may have critical role in inhibition of ESCC invasiveness and aggressiveness especially in advanced stages of the disease.

Homeobox (HOX) proteins and the receptor tyrosine kinase FLT3 are frequently highly expressed and mutated in acute myeloid leukemia (AML). Aberrant HOX expression is found in nearly all AMLs that harbor a mutation in the Nucleophosmin (NPM1) gene, and FLT3 is concomitantly mutated in approximately 60% of these cases. Little is known about how mutant NPM1 (NPM1
SIGNIFICANCE: MLL1 and DOT1L are chromatin regulators that control HOX, MEIS1, and FLT3 expression and are therapeutic targets in NPM1

Homeobox genes are known to be key factors in leukemogenesis. Although the TALE family homeodomain factor Meis1 has been linked to malignancy, a role for MEIS2 is less clear. Here, we demonstrate that MEIS2 is expressed at high levels in patients with AML1-ETO-positive acute myeloid leukemia and that growth of AML1-ETO-positive leukemia depends on MEIS2 expression. In mice, MEIS2 collaborates with AML1-ETO to induce acute myeloid leukemia. MEIS2 binds strongly to the Runt domain of AML1-ETO, indicating a direct interaction between these transcription factors. High expression of MEIS2 impairs repressive DNA binding of AML1-ETO, inducing increased expression of genes such as the druggable proto-oncogene YES1. Collectively, these data describe a pivotal role for MEIS2 in AML1-ETO-induced leukemia.