Annexin A8 regulates Wnt signaling to maintain the phenotypic plasticity of retinal pigment epithelial cells

Cone-rod homeobox transcriptionally activates TCF7 to promote the proliferation of retinal pigment epithelial and retinoblastoma cells in vitro

AIM

To investigate the proliferation regulatory effect of cone-rod homeobox (CRX) in retinal pigment epithelium (RPE) and retinoblastoma (RB) cells to explore the potential application and side effect (oncogenic potential) of CRX-based gene therapy in RPE-based retinopathies.

METHODS

Adult human retinal pigment epithelial (ARPE)-19 and human retinal pigment epithelial (RPE)-1 cells and Y79 RB cell were used in the study. Genetic manipulation was performed by lentivirus-based technology. The cell proliferation was determined by a CellTiter-Glo Reagent. The mRNA and protein levels were determined by quantitative real-time polymerase chain reaction (qPCR) and Western blot assay. The transcriptional activity of the promoter was determined by luciferase reporter gene assay. The bindings between CRX and transcription factor 7 (TCF7) promoter as well as TCF7 and the promoters of TCF7 target genes were examined by chromatin immunoprecipitation (ChIP) assay. The transcription of the TCF7 was determined by a modified nuclear run-on assay.

RESULTS

CRX overexpression and knockdown significantly increased (n=3, P<0.05 in all the cells) and decreased (n=3, P<0.01 in all the cells) the proliferation of RPE and RB cells. CRX overexpression and knockdown significantly increased and deceased the mRNA levels of Wnt signaling target genes [including MYC proto-oncogene (MYC), JUN, FOS like 1 (FOSL1), CCND1, cyclin D2 (CCND2), cyclin D3 (CCND3), cellular communication network factor 4 (CCN4), peroxisome proliferator activated receptor delta (PPARD), and matrix metallopeptidase 7 (MMP7)] and the luciferase activity driven by the Wnt signaling transcription factor (TCF7). TCF7 overexpression and knockdown significantly increased and decreased the proliferation of RPE and RB cells and depletion of TCF7 significantly abolished the stimulatory effect of CRX on the proliferation of RPE and RB cells. CRX overexpression and knockdown significantly increased and decreased the mRNA level of TCF7 and the promoter of TCF7 was significantly immunoprecipitated by CRX antibody.

CONCLUSION

CRX transcriptionally activates TCF7 to promote the proliferation of RPE and RB cells in vitro. CRX is a potential target for RPE-based regenerative medicine. The potential risk of this strategy, tumorigenic potential, should be considered.

Interference with ANXA8 inhibits the malignant progression of ovarian cancer by suppressing the activation of the Wnt/β-catenin signaling pathway via UCHL5

Ovarian cancer (OC), which threatens women's lives, is a common tumor of the female reproductive system. Annexin A8 (ANXA8) is highly expressed in OC. However, the mechanism of ANXA8 in OC remains unclear. This study investigated the potential mechanisms of ANXA8 in OC. The expression of ANXA8 in OC cells was determined by qRT-PCR and western blotting. ANXA8 interference plasmid was constructed. Moreover, CCK-8, EDU staining, TUNEL staining, western blotting, wound healing, and transwell assays were used to detect cell proliferation, apoptosis, migration, and invasion, respectively. Next, the relationship between ANXA8 and ubiquitin C-terminal hydrolase L5 (UCHL5) was verified through Co-IP. Finally, western blotting was used to detect the expression of Wnt/β-catenin signaling-related proteins. Additionally, we further interfered ANXA8 in nude mice with OC, and detected the expression of ANXA8, UCHL5 and the signaling pathway-related proteins by immunohistochemistry and western blotting. Our results suggested that ANXA8 expression was significantly increased in OC cells. ANXA8 interference significantly attenuated the proliferative, invasive, and migratory capabilities and promoted the apoptotic ability of OC cells. Moreover, the expression of UCHL5 in OC was significantly increased. ANXA8 bound to UCHL5 in OC cells. Knockdown of ANXA8 attenuated OC cell malignant progression by downregulating the expression of UCHL5. Furthermore, ANXA8 affected the expression of Wnt/β-catenin signaling pathway-related proteins in OC cells via UCHL5. Collectively, ANXA8 interference suppressed the activation of Wnt/β-catenin signaling pathway via UCHL5 to inhibit cell proliferation, invasion, migration and induce cell apoptosis in OC, thus presenting a potential therapeutic strategy for OC treatment.

AnnexinA6: a potential therapeutic target gene for extracellular matrix mineralization

The mineralization of the extracellular matrix (ECM) is an essential and crucial process for physiological bone formation and pathological calcification. The abnormal function of ECM mineralization contributes to the worldwide risk of developing mineralization-related diseases; for instance, vascular calcification is attributed to the hyperfunction of ECM mineralization, while osteoporosis is due to hypofunction. AnnexinA6 (AnxA6), a Ca2+-dependent phospholipid-binding protein, has been extensively reported as an essential target in mineralization-related diseases such as osteoporosis, osteoarthritis, atherosclerosis, osteosarcoma, and calcific aortic valve disease. To date, AnxA6, as the largest member of the Annexin family, has attracted much attention due to its significant contribution to matrix vesicles (MVs) production and release, MVs-ECM interaction, cytoplasmic Ca2+ influx, and maturation of hydroxyapatite, making it an essential target in ECM mineralization. In this review, we outlined the recent advancements in the role of AnxA6 in mineralization-related diseases and the potential mechanisms of AnxA6 under normal and mineralization-related pathological conditions. AnxA6 could promote ECM mineralization for bone regeneration in the manner described previously. Therefore, AnxA6 may be a potential osteogenic target for ECM mineralization.

Annexins as potential targets in ocular diseases

Annexins (AnxAs) are Ca2+/phospholipid-binding proteins extensively studied and generally involved in several diseases. Although evidence exists regarding the distribuition of AnxAs in the visual system, their exact roles and the exact cell types of the eye where these proteins are expressed are not well-understood. AnxAs have pro-resolving roles in infectious, autoimmune, degenerative, fibrotic and angiogenic conditions, making them an important target in ocular tissue homeostasis. This review summarizes the current knowledge on the distribution and function of AnxA1-8 isoforms under normal and pathological conditions in the visual system, as well as perspectives for ophthalmologic treatments, including the potential use of the AnxA1 recombinant and/or its mimetic peptide Ac2-26.

Annexins and cardiovascular diseases: Beyond membrane trafficking and repair

Cardiovascular diseases (CVD) remain the leading cause of mortality worldwide. The main cause underlying CVD is associated with the pathological remodeling of the vascular wall, involving several cell types, including endothelial cells, vascular smooth muscle cells, and leukocytes. Vascular remodeling is often related with the development of atherosclerotic plaques leading to narrowing of the arteries and reduced blood flow. Atherosclerosis is known to be triggered by high blood cholesterol levels, which in the presence of a dysfunctional endothelium, results in the retention of lipoproteins in the artery wall, leading to an immune-inflammatory response. Continued hypercholesterolemia and inflammation aggravate the progression of atherosclerotic plaque over time, which is often complicated by thrombus development, leading to the possibility of CV events such as myocardial infarction or stroke. Annexins are a family of proteins with high structural homology that bind phospholipids in a calcium-dependent manner. These proteins are involved in several biological functions, from cell structural organization to growth regulation and vesicle trafficking. In vitro gain- or loss-of-function experiments have demonstrated the implication of annexins with a wide variety of cellular processes independent of calcium signaling such as immune-inflammatory response, cell proliferation, migration, differentiation, apoptosis, and membrane repair. In the last years, the use of mice deficient for different annexins has provided insight into additional functions of these proteins in vivo, and their involvement in different pathologies. This review will focus in the role of annexins in CVD, highlighting the mechanisms involved and the potential therapeutic effects of these proteins.

Gene expression of intracortical bone demonstrates loading-induced increases in Wnt1 and Ngf and inhibition of bone remodeling processes

Osteocytes are the primary mechanosensitive cells in bone. However, their location in mineralized matrix has limited the in vivo study of osteocytic genes induced by mechanical loading. Laser Capture Microdissection (LCM) allows isolation of intracortical bone (Intra-CB), enriched for osteocytes, from bone tissue for gene expression analysis. We used microarray to analyze gene expression from mouse tibial Intra-CB dissected using LCM 4 h after a single loading bout or after 5 days of loading. Osteocyte enrichment was supported by greater expression of Sost, Dmp1, Dkk1, and Mepe in Intra-CB regions vs. Mixed regions containing periosteum and muscle (fold-change (FC) = 3.4, 2.2, 5.1, 3.0, respectively). Over 150 differentially expressed genes (DEGs) due to loading (loaded vs. contralateral control) in Intra-CB were found on Day 1 and Day 5, but only 10 genes were differentially expressed on both days, including Ngf (Day 1 FC = 13.5, Day 5 FC = 11.1) and Wnt1 (Day 1 FC = 1.5, Day 5 FC = 5.1). The expression of Ngf and Wnt1 within Intra-CB was confirmed by in situ hybridization, and a significant increase in number of Wnt1 mRNA molecules occurred on day 1. We also found changes in extracellular matrix remodeling with Timp1 (FC = 3.1) increased on day 1 and MMP13 (FC = 0.3) decreased on day 5. Supporting this result, IHC for osteocytic MMP13 demonstrated a marginal decrease due to loading on day 5. Gene Ontology (GO) biological processes for loading DEGs indicated regulation of vasculature, neuronal and immune processes while cell-type specific gene lists suggested regulation of osteoclast, osteoblast, and endothelial related genes. In summary, microarray analysis of microdissected Intra-CB revealed differential regulation of Ngf, Wnt1, and MMP13 due to loading in osteocytes.

Identification of Diagnostic Biomarkers and Their Correlation with Immune Infiltration in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a progressive neurodegenerative disease of the central retina, with no suitable biomarkers for early diagnosis and treatment. This study aimed to find potential diagnostic biomarker candidates for AMD and investigate their immune-related roles in this pathology. Weight gene correlation analysis was first performed based on data from the Gene Expression Omnibus database and 20 hub genes were identified. The functional enrichment analyses showed that the innate immune response, inflammatory response, and complement activation were key pathways associated with AMD. Complement C1s (C1S), adrenomedullin (ADM), and immediate early response 5 like (IER5L) were identified as the crucial genes with favorable diagnostic values for AMD by using LASSO analysis and multiple logistic regression. Furthermore, a 3-gene model was constructed and proved to be of good diagnostic and predictive performance for AMD (AUC = 0.785, 0.840, and 0.810 in training, test, and validation set, respectively). Finally, CIBERSORT was used to evaluate the infiltration of immune cells in AMD tissues. The results showed that the NK cells, CD4 memory T cell activation, and macrophage polarization may be involved in the AMD process. C1S, ADM, and IER5L were correlated with the infiltration of the above immune cells. In conclusion, our study suggests that C1S, ADM, and IER5L are promising diagnostic biomarker candidates for AMD and may regulate the infiltration of immune cells in the occurrence and progression of AMD.

Emerging Cancer Epigenetic Mechanisms Regulated by All-Trans Retinoic Acid

All-trans retinoic acid (RA), which is the dietary bioactive derivative obtained from animal (retinol) and plant sources (beta-carotene), is a physiological lipid signal of both embryonic and postembryonic development. During pregnancy, either RA deficiency or an excessive RA intake is teratogenic. Too low or too high RA affects not only prenatal, but also postnatal, developmental processes such as myelopoiesis and mammary gland morphogenesis. In this review, we mostly focus on emerging RA-regulated epigenetic mechanisms involving RA receptor alpha (RARA) and Annexin A8 (ANXA8), which is a member of the Annexin family, as well as ANXA8 regulatory microRNAs (miRNAs). The first cancer showing ANXA8 upregulation was reported in acute promyelocytic leukemia (APL), which induces the differentiation arrest of promyelocytes due to defective RA signaling caused by RARA fusion genes as the PML-RARA gene. Over the years, ANXA8 has also been found to be upregulated in other cancers, even in the absence of RARA fusion genes. Mechanistic studies on human mammary cells and mammary glands of mice showed that ANXA8 upregulation is caused by genetic mutations affecting RARA functions. Although not all of the underlying mechanisms of ANXA8 upregulation have been elucidated, the interdependence of RA-RARA and ANXA8 seems to play a relevant role in some normal and tumorigenic settings.

High expression and potential synergy of human epididymis protein 4 and Annexin A8 promote progression and predict poor prognosis in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most common cause of gynecological cancer-related deaths. Aberrant expression of human epididymis protein 4 (HE4) and Annexin A8 (ANXA8) plays crucial roles in some malignancies; however, their functions in EOC remain unclear. In this study, we utilized immunohistochemistry, real-time PCR, western blotting, immunofluorescence labeling, and gene interaction and enrichment pathway analyses to explore the roles of HE4 and ANXA8 in EOC. They were highly expressed in EOC tissues, which significantly correlated with higher tumor burden, advanced FIGO stages, poor differentiation, presence of > 1 cm residual tumor, and tumor recurrence. The expression patterns of HE4 and ANXA8 were similar, and Spearman's correlation analysis showed that they were positively correlated (r=0.671, P < 0.001). Large sample database analyses also showed significant positive correlation between their mRNA expression (R=0.304, 0.321, and 0.304 in TCGA, CCLE and GTEx, respectively, all P < 0.001). Kaplan-Meier survival analysis demonstrated that advanced FIGO stages, lymph node metastasis, residual tumor size > 1 cm, and high HE4 and ANXA8 expression were significantly associated with poor overall survival (all P < 0.05). Moreover, multivariate Cox analysis showed that advanced FIGO stages and HE4 expression were independent factors for poor survival (P < 0.001, 0.012, respectively). Interaction network analysis of genes associated with ANXA8, expressed in response to HE4, revealed that these genes participated in TP53 expression, autophagy regulation, and the PID FOXO pathway. In conclusion, the potential synergy between HE4 and ANXA8 may exacerbate the disease condition. Thus, targeting HE4 and ANXA8 could be a novel therapeutic strategy for ovarian cancer.