The impact of MEIS1 TALE homeodomain transcription factor knockdown on glioma stem cell growth

Myeloid ecotropic virus insertion site 1 (MEIS1) is a HOX co-factor necessary for organ development and normal hematopoiesis. Recently, MEIS1 has been linked to the development and progression of various cancers. However, its role in gliomagenesis particularly on glioma stem cells (GSCs) remains unclear. Here, we demonstrate that MEIS1 is highly upregulated in GSCs compared to normal, and glioma cells and to its differentiated counterparts. Inhibition of MEIS1 expression by shRNA significantly reduced GSC growth in both in vitro and in vivo experiments. On the other hand, integrated transcriptomics analyses of glioma datasets revealed that MEIS1 expression is correlated to cell cycle-related genes. Clinical data analysis revealed that MEIS1 expression is elevated in high-grade gliomas, and patients with high MEIS1 levels have poorer overall survival outcomes. The findings suggest that MEIS1 is a prognostic biomarker for glioma patients and a possible target for developing novel therapeutic strategies against GBM.

Novel circularRNA circ-0047078 promotes pancreatic ductal adenocarcinoma progression through mircoRNA miR-11181- Chemokine (C-X-C motif) Ligand 12/Melanoma Cell Adhesion Molecule/Regulator of G-protein signaling 16 pathway

BACKGROUND

Circular RNAs (circRNAs), new members of the noncoding RNA family, have been reported to participate in various pathological conditions, especially cancer. Pancreatic ductal adenocarcinoma (PDAC), as one of the most aggressive human solid tumors, is still with a low surgical cure rate. Exploring the role of circRNAs in PDAC is meaningful, and may offer a new therapeutic approach for PDAC.

METHODS AND RESULTS

Competing endogenous RNA (ceRNA) microarray revealed that circ-0047078 was highly expressed in pancreatic ductal adenocarcinoma (PDAC) tissues compared with adjacent normal tissues, and the differential expression was further confirmed by PCR in both tissues and cell lines. Cell functional assays including cell counting kit-8 (CCK-8) assay, transwell invasion assay, flow cytometry and caspase activity assay demonstrated that circ-0047078 was positively correlated with the proliferation and invasion but negatively correlated with the apoptosis of CFPAC-1 cells. Circ-0047078 knockdown led to miR-11181, CXCL12 and MCAM downregulation and RGS16 upregulation, and the effect of circ-0047078 knockdown on CFPAC-1 cell behavior change can be reversed by miR-11181 mimic. Moreover, clinicopathological analysis indicated that circ-0047078 expression level was positively correlated with lymphatic metastasis and perineural invasion. In addition, knockdown of Chemokine (C-X-C motif) Ligand 12 (CXCL12) alone decreased proliferation, invasion, but increased apoptosis of CFPAC-1 cells, and raised the activity of caspase-3, caspase-8 and caspase-9 activity. Knockdown of Melanoma Cell Adhesion Molecule (MCAM) alone decreased invasion and increased apoptosis of CFPAC-1 cells, and both caspase-3 and caspase-9 activity increased, but no obvious change observed on caspase-8, and also no significant effect on CFPAC-1 cells proliferation. Knockdown of Regulator of G-protein signaling 16 (RGS16) alone increased invasion of CFPAC-1 cells, but had no significant effect on proliferation and apoptosis, of course, no obvious change on the activity of caspase-3, caspase-8 and caspase-9 had been observed.

CONCLUSIONS

In conclusion, circ-0047078 plays a role in promoting PDAC via miR-11181 and then via CXCL12, MCAM and RGS16. Circ-0047078 may serve as a promising novel therapeutic target for PDAC patients.

Oncogenic and tumor suppressor function of MEIS and associated factors

MEIS proteins are historically associated with tumorigenesis, metastasis, and invasion in cancer. MEIS and associated PBX-HOX proteins may act as tumor suppressors or oncogenes in different cellular settings. Their expressions tend to be misregulated in various cancers. Bioinformatic analyses have suggested their upregulation in leukemia/lymphoma, thymoma, pancreas, glioma, and glioblastoma, and downregulation in cervical, uterine, rectum, and colon cancers. However, every cancer type includes, at least, a subtype with high MEIS expression. In addition, studies have highlighted that MEIS proteins and associated factors may function as diagnostic or therapeutic biomarkers for various diseases. Herein, MEIS proteins and associated factors in tumorigenesis are discussed with recent discoveries in addition to how they could be modulated by noncoding RNAs or newly developed small-molecule MEIS inhibitors.

The emerging role of MEIS1 in cell proliferation and differentiation

Cell proliferation and differentiation are the foundation of reproduction and growth. Mistakes in these processes may affect cell survival, or cause cell cycle dysregulation, such as tumorigenesis, birth defects and degenerative diseases, or cell death. Myeloid ecotropic viral integration site 1 (MEIS1) was initially discovered in leukemic mice. Recent research identified MEIS1 as an important transcription factor that regulates cell proliferation and differentiation during cell fate commitment. MEIS1 has a pro-proliferative effect in leukemia cells; however, its overexpression in cardiomyocytes restrains neonatal and adult cardiomyocyte proliferation. In addition, MEIS1 has carcinogenic or tumor suppressive effects in different neoplasms. Thus, this uncertainty suggests that MEIS1 has a unique function in cell proliferation and differentiation. In this review, we summarize the primary findings of MEIS1 in regulating cell proliferation and differentiation. Correlations between MEIS1 and cell fate specification might suggest MEIS1 as a therapeutic target for diseases.

CD146 (Cluster of Differentiation 146)

CD146 (cluster of differentiation 146) is an adhesion molecule that is expressed by different cells constituting vessels, particularly endothelial cells. The last 30 years of research in this field have shown that CD146 plays a key role in the control of several vessel functions. Three forms of CD146 have been described, including 2 transmembrane isoforms and a soluble protein that is detectable in the plasma. These CD146 forms mediate pleiotropic functions through homophilic and heterophilic interactions with proteins present on surrounding partners. Several studies used neutralizing antibodies, siRNA, or genetically modified mice to demonstrate the involvement of CD146 in the regulation of angiogenesis, vascular permeability, and leukocyte transmigration. In this review, we will focus on the current knowledge of the roles of CD146 in vascular homeostasis and diseases associated with endothelial dysfunction.

Super-enhancer-associated MEIS1 promotes transcriptional dysregulation in Ewing sarcoma in co-operation with EWS-FLI1

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.

MEIS transcription factors in development and disease

MEIS transcription factors are key regulators of embryonic development and cancer. Research on MEIS genes in the embryo and in stem cell systems has revealed novel and surprising mechanisms by which these proteins control gene expression. This Primer summarizes recent findings about MEIS protein activity and regulation in development, and discusses new insights into the role of MEIS genes in disease, focusing on the pathogenesis of solid cancers.