Targeting Endothelial Connexin37 Reduces Angiogenesis and Decreases Tumor Growth

Construction and validation of a prognostic model of angiogenesis-related genes in multiple myeloma

BACKGROUND

Angiogenesis is associated with tumour growth, infiltration, and metastasis. This study aimed to detect the mechanisms of angiogenesis-related genes (ARGs) in multiple myeloma (MM) and to construct a new prognostic model.

METHODS

MM research foundation (MMRF)-CoMMpass cohort, GSE47552, GSE57317, and ARGs were sourced from public databases. Differentially expressed genes (DEGs) in the tumour and control cohorts in GSE47552 were determined through differential expression analysis and were enriched with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Weighted gene coexpression network analysis (WGCNA) was applied to derive modules linked to the ARG scores and obtain module genes in GSE47552. Differentially expressed ARGs (DE-ARGs) were selected for subsequent analyses by overlapping DEGs and module genes. Furthermore, prognostic genes were selected using univariate Cox and least absolute shrinkage and selection operator (LASSO) regression analyses. Depending on the prognostic genes, a risk model was constructed, and risk scores were determined. Moreover, MM samples from MMRF-CoMMpass were sorted into high- and low-risk teams on account of the median risk score. Additionally, correlations among clinical characteristics, gene set variation analysis (GSVA), gene set enrichment analysis (GSEA), immune analysis, immunotherapy predictions and the mRNA‒miRNA‒lncRNA network were carried out.

RESULTS

A total of 898 DEGs, 211 module genes, 24 DE-ARGs and three prognostic genes (AKAP12, C11orf80 and EMP1) were selected for this study. Enrichment analysis revealed that the DEGs were related to 86 GO terms, such as 'cytoplasmic translation', and 41 KEGG pathways, such as 'small cell lung cancer'. A prognostic gene-based risk model was created in MMRF-CoMMpass and confirmed with the GSE57317 dataset. Moreover, a nomogram was established on the basis of independent prognostic factors that have proven to be good predictors. In addition, the immune cell infiltration results suggested that memory B cells were enriched in the high-risk group and that immature B cells were enriched in the low-risk group. Finally, the mRNA‒miRNA‒lncRNA network demonstrated that hsa-miR-508-5p was tightly associated with EMP1 and AKAP12. RT‒qPCR was used to validate the expression of the genes associated with prognosis.

CONCLUSION

A new prognostic model of MM associated with ARGs was created and validated, providing a new perspective for exploring the connection between ARGs and MM.

DNMT1-mediated NR3C1 DNA methylation enables transcription activation of connexin40 and augments angiogenesis during colorectal cancer progression

Colorectal cancer (CRC) continues to be a major contributor to cancer-related mortality. Connexin 40 (CX40) is one of the major gap junction proteins with the capacity in regulating cell-to-cell communication and angiogenesis. This study investigates its role in angiogenesis in CRC and explores the regulatory mechanism. Aberrant high CX40 expression was detected in tumor tissues, which was associated with a poor prognosis in CRC patients. Elevated CX40 expression was detected in CRC cell lines as well. Conditioned medium of SW620 and HT29 cell lines was used to induce angiogenesis of human umbilical vein endothelial cells (HUVECs). CX40 knockdown in CRC cells reduced angiogenesis and mobility of HUVECs and blocked CRC cell proliferation, mobility, and survival. Following bioinformatics predictions, we validated by chromatin immunoprecipitation and luciferase assays that nuclear receptor subfamily 3 group C member 1 (NR3C1), which was poorly expressed in CRC samples, suppressed CX40 transcription. The poor NR3C1 expression was attributive to DNA hypermethylation induced by DNA methyltransferase 1 (DNMT1). Restoration of NR3C1 suppressed the pro-angiogenic effect, proliferation and survival, and tumorigenic activity of CRC cells, which were, however, rescued by CX40 upregulation. Collectively, this study demonstrates that transcription activation of CX40 upon DNMT1-mediated NR3C1 DNA methylation potentiates angiogenesis in CRC.

The roles of connexins and gap junctions in the progression of cancer

Gap junctions (GJs), which are composed of connexins (Cxs), provide channels for direct information exchange between cells. Cx expression has a strong spatial specificity; however, its influence on cell behavior and information exchange between cells cannot be ignored. A variety of factors in organisms can modulate Cxs and subsequently trigger a series of responses that have important effects on cellular behavior. The expression and function of Cxs and the number and function of GJs are in dynamic change. Cxs have been characterized as tumor suppressors in the past, but recent studies have highlighted the critical roles of Cxs and GJs in cancer pathogenesis. The complex mechanism underlying Cx and GJ involvement in cancer development is a major obstacle to the evolution of therapy targeting Cxs. In this paper, we review the post-translational modifications of Cxs, the interactions of Cxs with several chaperone proteins, and the effects of Cxs and GJs on cancer. Video Abstract.

Connexin37 Regulates Cell Cycle in the Vasculature

Control of vascular cell growth responses is critical for development and maintenance of a healthy vasculature. Connexins - the proteins comprising gap junction channels - are key regulators of cell growth in diseases such as cancer, but their involvement in controlling cell growth in the vasculature is less well appreciated. Connexin37 (Cx37) is one of four connexin isotypes expressed in the vessel wall. Its primary role in blood vessels relies on its unique ability to transduce flow-sensitive signals into changes in cell cycle status of endothelial (and perhaps, mural) cells. Here, we review available evidence for Cx37's role in the regulation of vascular growth, vessel organization, and vascular tone in healthy and diseased vasculature. We propose a novel mechanism whereby Cx37 accomplishes this with a phosphorylation-dependent transition between closed (growth-suppressive) and multiple open (growth-permissive) channel conformations that result from interactions of the C-terminus with cell-cycle regulators to limit or support cell cycle progression. Lastly, we discuss Cx37 and its downstream signaling as a novel potential target in the treatment of cardiovascular disease, and we address outstanding research questions that still challenge the development of such therapies.

Connexins and angiogenesis: Functional aspects, pathogenesis, and emerging therapies (Review)

Connexins (Cxs) play key roles in cellular communication. By facilitating metabolite exchange or interfering with distinct signaling pathways, Cxs affect cell homeostasis, proliferation, and differentiation. Variations in the activity and expression of Cxs have been linked to numerous clinical conditions including carcinomas, cardiac disorders, and wound healing. Recent discoveries on the association between Cxs and angiogenesis have sparked interest in Cx-mediated angiogenesis due to its essential functions in tissue formation, wound repair, tumor growth, and metastasis. It is now widely recognized that understanding the association between Cxs and angiogenesis may aid in the development of new targeted therapies for angiogenic diseases. The aim of the present review was to provide a comprehensive overview of Cxs and Cx-mediated angiogenesis, with a focus on therapeutic implications.