Effect of shRNA mediated down-regulation of Annexin A2 on biological behavior of human lung adencarcinoma cells A549

Açaí (Euterpe oleracea Mart.) Seed Oil Exerts a Cytotoxic Role over Colorectal Cancer Cells: Insights of Annexin A2 Regulation and Molecular Modeling

Açaí, Euterpe oleracea Mart., is a native plant from the Amazonian and is rich in several phytochemicals with anti-tumor activities. The aim was to analyze the effects of açaí seed oil on colorectal adenocarcinoma (ADC) cells. In vitro analyses were performed on CACO-2, HCT-116, and HT-29 cell lines. The strains were treated with açaí seed oil for 24, 48, and 72 h, and cell viability, death, and morphology were analyzed. Molecular docking was performed to evaluate the interaction between the major compounds in açaí seed oil and Annexin A2. The viability assay showed the cytotoxic effect of the oil in colorectal adenocarcinoma cells. Acai seed oil induced increased apoptosis in CACO-2 and HCT-116 cells and interfered with the cell cycle. Western blotting showed an increased expression of LC3-B, suggestive of autophagy, and Annexin A2, an apoptosis regulatory protein. Molecular docking confirmed the interaction of major fatty acids with Annexin A2, suggesting a role of açaí seed oil in modulating Annexin A2 expression in these cancer cell lines. Our results suggest the anti-tumor potential of açaí seed oil in colorectal adenocarcinoma cells and contribute to the development of an active drug from a known natural product.

Advances in cancer treatment: a new therapeutic target, Annexin A2

Annexin A2 (ANXA2) is a calcium regulated phospholipid-binding protein. It is expressed in some tumor cells, endothelial cells, macrophages, and mononuclear cells, affecting cell survival and mediating interactions between intercellular and extracellular microenvironment. Aberrant expression of ANXA2 can be used as a potential predictive factor, diagnostic biomarker and therapeutic target in cancer therapy. Investigators used various technologies to target ANXA2 in a preclinical model of human cancers and demonstrated encouraging results. In this review article, we discuss the diagnosis and prognosis latent capacity of ANXA2 in progressive cancers, focus on the exploration of restorative interventions targeting ANXA2 in cancer treatment. Further, we comment on a promising candidate therapy that is conceivable for clinical translation.

Inhibitory effects of ceramide kinase on Rac1 activation, lamellipodium formation, cell migration, and metastasis of A549 lung cancer cells

Ceramide kinase (CerK) phosphorylates ceramide to ceramide-1-phosphate (C1P), a bioactive sphingolipid. Since the mechanisms responsible for regulating the proliferation and migration/metastasis of cancer cells by the CerK/C1P pathway remain unclear, we conducted the present study. The knockdown of CerK in A549 lung and MCF-7 breast cancer cells (shCerK cells) increased the formation of lamellipodia, which are membrane protrusions coupled with cell migration. Mouse embryonic fibroblasts prepared from CerK-null mice also showed an enhanced formation of lamellipodia. The overexpression of CerK inhibited lamellipodium formation in A549 cells. The knockdown of CerK increased the number of cells having lamellipodia with Rac1 and the levels of active Rac1-GTP form, whereas the overexpression of CerK decreased them. CerK was located in lamellipodia after the epidermal growth factor treatment, indicating that CerK functioned there to inhibit Rac1. The migration of A549 cells was negatively regulated by CerK. An intravenous injection of A549-shCerK cells into nude mice resulted in markedly stronger metastatic responses in the lungs than an injection of control cells. The in vitro growth of A549 cells and in vivo expansion after the injection into mouse flanks were not affected by the CerK knockdown. These results suggest that the activation of CerK/C1P pathway has inhibitory roles on lamellipodium formation, migration, and metastasis of A549 lung cancer cells.

Annexin A2 upregulation protects human retinal endothelial cells from oxygen-glucose deprivation injury by activating autophagy

Retinal neovascularization is a common pathological change in multiple diseases of the eyes and the upregulation of annexin A2 (A2) under a hypoxic and ischemic microenvironment has been demonstrated to be a key factor in the pathological process. However, the underlying mechanism by which A2 regulates retinal neovascularization remains unclear. In the present study, oxygen-glucose deprivation (OGD) was used to mimic the hypoxic and ischemic microenvironment, to observe the role of A2 in retinal neovascularization regulation by focusing on autophagy. The results showed that OGD treatment significantly increased the mRNA and protein levels of A2 in human retinal endothelial cells (HRECs), which was dependent on activation of hypoxia inducible factor (HIF)-1α signaling. The OGD-induced activation of autophagy was attenuated when A2 was silenced, but increased when A2 was overexpressed, suggesting that A2 upregulation contributed to OGD-induced cell autophagy activation. Furthermore, knockdown of A2 decreased cell viability and promoted cell apoptosis under OGD conditions. Overexpression of A2 increased cell viability and reduced cell apoptosis under OGD conditions, and inhibiting autophagy using an inhibitor, reversed these changes, suggesting that upregulation of A2 by OGD serves a cytoprotective role by inducing cell autophagy in HRECs. Taken together, the results of the present study suggested that promoting retinal endothelial cell survival by autophagy activation via the HIF-1α signaling pathway in a hypoxic and ischemic microenvironment may underlie the mechanism by which A2 regulates retinal neovascularization. The present study is the first study to demonstrate the novel role of A2 during retinal neovascularization under pathological conditions, to the best of our knowledge. Therefore, A2 may serve as a potential therapeutic target for treating neovascularization-associated conditions of the eye.

Interaction of HE4 and ANXA2 exists in various malignant cells-HE4-ANXA2-MMP2 protein complex promotes cell migration

Background

The interaction between human epididymis protein 4 (HE4) and annexin A2 (Annexin A2) has been found in ovarian cancer. However, it is dimness whether the interaction exists in other malignant tumors.

Methods

Real-time PCR, western blotting and immunocytochemistry were used to detect mRNA and proteins expression. Co-immunoprecipitation and double-labeling immunofluorescence were used to detect the interaction among HE4, ANXA2 and MMP2. MTS assay was used to test cell proliferation. Adhesion test was used to test cell adhesion. Flow cytometry was applied to examine cell cycle. The scratch test and Transwell assay was performed to detect the migration and invasion of various malignant cell lines.

Results

Here we show that the overexpression of HE4 and ANXA2 in various malignant cells is a common phenomenon. HE4 and ANXA2 are co-localized in the cytoplasm and membrane of various tumor cells. ES-2 cells which had both high expression of HE4 and ANXA2 were much stronger in proliferation, adhesion, invasion, and migration than other tumor cells. HE4–ANXA2–MMP2 could form a triple protein complex. HE4 could mediate the expression of MMP2 via ANXA2 to promote cell migration progress.

Conclusions

The interaction of HE4 and ANXA2 exists in various types of cancer cells. HE4 and ANXA2 can promote the proliferation, adhesion, invasion, and migration of cancer cells. HE4–ANXA2–MMP2 form a protein complex and ANXA2 plays the role of “bridge”. They performed together to promote cell migration.

Two tales of Annexin A2 knock-down: One of compensatory effects by antisense RNA and another of a highly active hairpin ribozyme

Besides altering its own expression during cell transformation, Annexin A2 is upregulated during the progression of many cancer types and also plays key roles during viral infection and multiplication. Consequently, there has been great interest in Annexin A2 as a potential drug target. The successful design of efficient in vivo delivery systems constitutes an obstacle in full exploitation of antisense and RNA-cleaving technologies for the knock-down of specific targets. Efficiency is dependent on the method of delivery and accessibility of the target. Here, hairpin ribozymes and an antisense RNA against rat annexin A2 mRNA were tested for their efficiencies in a T7-driven coupled transcription/translation system. The most efficient ribozyme and antisense RNA were subsequently inserted into a retroviral vector under the control of a tRNA promoter, in a cassette inserted between retroviral Long Terminal Repeats for stable insertion into host DNA. The Phoenix package system based on defective retroviruses was used for virus-mediated gene transfer into PC12 cells. Cells infected with the ribozyme-containing particles died shortly after infection. However, the same ribozyme showed a very high catalytic effect in vitro in cell lysates, explained by its loose hinge helix 2 region. This principle can be transferred to other ribozymes, such as those designed to cleave the guide RNA in the CRISPR/Cas9 technology, as well as to target specific viral RNAs. Interestingly, efficient down-regulation of the expression of Annexin A2 by the antisense RNA resulted in up-regulation of Annexin A7 as a compensatory effect after several cell passages. Indeed, compensatory effects have previously been observed during gene knock-out, but not during knock-down of protein expression. This highlights the problems in interpreting the phenotypic effects of knocking down the expression of a protein. In addition, these data are highly relevant when considering the effects of the CRISPR/Cas9 approach.

ANXA2 Silencing Inhibits Proliferation, Invasion, and Migration in Gastric Cancer Cells

Annexin A2 (ANXA2) has been well known to associate with the progress of malignant tumor. However, the biological behavior of ANXA2 in gastric cancer (GC) remains unclear. We made a hypothesis in transcriptome level from TCGA datasets. Then, we used immunohistochemical staining to quantify the expression level of ANXA2 protein in GC tissues compared with adjacent tissues. Quantitative real-time PCR and western blot were used for analyzing ANXA2 expression in human GC (SGC-7901, MKN-45, BGC-823, and AGS) cell lines. We investigated the effect of a lentivirus-mediated knock-down of ANXA2 on the proliferation, invasion and migration of gastric cancer AGS cells. Cell proliferation was examined by MTT and colony formation tests. Cell apoptosis and cycle were measured by flow cytometry. Migration and invasion were detected by transwell assay. We found that high expression of ANXA2 can increase the mobility of cancer cells from TCGA datasets. ANXA2 was upregulated in GC tissues compared with adjacent tissues. AGS cell line displayed significantly higher expression of ANXA2 among the four GC cell lines. In addition, ANXA2 silencing led to a weakened ability of proliferation, invasion, and migration in GC cells; targeting of ANXA2 may be a potential therapeutic strategy for GC patients.

Annexin A2-mediated cancer progression and therapeutic resistance in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a head and neck cancer with poor clinical outcomes and insufficient treatments in Southeast Asian populations. Although concurrent chemoradiotherapy has improved recovery rates of patients, poor overall survival and low efficacy are still critical problems. To improve the therapeutic efficacy, we focused on a tumor-associated protein called Annexin A2 (ANXA2). This review summarizes the mechanisms by which ANXA2 promotes cancer progression (e.g., proliferation, migration, the epithelial-mesenchymal transition, invasion, and cancer stem cell formation) and therapeutic resistance (e.g., radiotherapy, chemotherapy, and immunotherapy). These mechanisms gave us a deeper understanding of the molecular aspects of cancer progression, and further provided us with a great opportunity to overcome therapeutic resistance of NPC and other cancers with high ANXA2 expression by developing this prospective ANXA2-targeted therapy.

Tyr23 phosphorylation of Anxa2 enhances STAT3 activation and promotes proliferation and invasion of breast cancer cells

PURPOSE

Overexpression of Annexin A2 (Anxa2) is positively correlated with breast cancer progression, drug resistance, and poor prognosis of patients with breast cancer. Tyr23 Phosphorylation by Src-family tyrosine kinase is an important post-translational modification of Anxa2. This modification regulates the subcellular localization and functions of Anxa2 and has significant effects on cell proliferation, migration, and invasion. This study aims at revealing the association of Anxa2-Tyr23 phosphorylation in Anxa2-mediated acceleration of breast cancer progression and their elaborate molecular mechanisms.

METHODS

Cell biological function experiments were performed to determine the effects of Anxa2-Tyr23 Phosphorylation on breast cancer cell proliferation and invasion in vitro and metastasis in vivo. The interaction of Tyr23 phosphorylated Anxa2 and STAT3 was verified by co-immunoprecipitation assay. Related mRNA and protein expression levels of cyclin D1 and MMP2/9 and phosphorylation level of STAT3 were detected.

RESULTS

Anxa2-Tyr23 phosphorylation is necessary for proliferation, invasion, and metastasis of breast cancer cells in vitro and in vivo. Tyr23 phosphorylated Anxa2 binds and enhances the sensitivity of STAT3 activation in response to IL-6, thereby increasing the protein and mRNA expression levels of cyclin D1 and MMP2/9 which are STAT3 key target genes and serve pivotal regulatory functions in cell proliferation and invasion, respectively.

CONCLUSION

Our findings further confirmed the regulatory role of Anxa2 and revealed the direct relationship between Anxa2-Tyr23 phosphorylation and activation of STAT3. Moreover, this study provides novel insights into the function of Anxa2-Tyr23 phosphorylation in signal transduction for further understanding of the mechanism through which Anxa2 promotes the progression of breast cancer.

Running-Induced Systemic Cathepsin B Secretion Is Associated with Memory Function

Peripheral processes that mediate beneficial effects of exercise on the brain remain sparsely explored. Here, we show that a muscle secretory factor, cathepsin B (CTSB) protein, is important for the cognitive and neurogenic benefits of running. Proteomic analysis revealed elevated levels of CTSB in conditioned medium derived from skeletal muscle cell cultures treated with AMP-kinase agonist AICAR. Consistently, running increased CTSB levels in mouse gastrocnemius muscle and plasma. Furthermore, recombinant CTSB application enhanced expression of brain-derived neurotrophic factor (BDNF) and doublecortin (DCX) in adult hippocampal progenitor cells through a mechanism dependent on the multifunctional protein P11. In vivo, in CTSB knockout (KO) mice, running did not enhance adult hippocampal neurogenesis and spatial memory function. Interestingly, in Rhesus monkeys and humans, treadmill exercise elevated CTSB in plasma. In humans, changes in CTSB levels correlated with fitness and hippocampus-dependent memory function. Our findings suggest CTSB as a mediator of effects of exercise on cognition.

Annexin A2 Coordinates STAT3 to Regulate the Invasion and Migration of Colorectal Cancer Cells In Vitro

The present study aimed to reveal the expression of STAT3 and Anxa 2 in CRC specimens and to investigate the effects of STAT3 and Anxa 2 signaling on the proliferation, invasion, and migration in CRC Caco-2 cells. Results demonstrated that both Anxa 2 and STAT3 were highly expressed in CRC specimens in both mRNA and protein levels, with or without phosphorylation (Tyrosine 23 in Anxa 2 and Tyrosine 705 in STAT3). And the upregulated Anxa 2 promoted the phosphorylation of STAT3 (Tyrosine 705) in CRC Caco-2 cells. The upregulated Anxa 2 promoted the proliferation, migration, and invasion of Caco-2 cells in vitro. Moreover, the STAT3 knockdown also repressed the proliferation, migration, and invasion of Caco-2 cells. In conclusion, the overexpressed Annexin A2 regulated the proliferation, invasion, and migration in CRC cells in an association with STAT3.

Annexin A2 silencing enhances apoptosis of human umbilical vein endothelial cells in vitro

OBJECTIVE

To study the effects of inhibited Annexin A2 (ANXA2) on human umbilical vein endothelial cells (HUVECs) in vitro.

METHODS

Short hairpin RNA (shRNA) targeting ANXA2 was designed and cloned into double marked lentivirial vector GV248 for RNAi to generate the recombinant expression plasmids, which were stably transfected into HUVECs. The protein and mRNA expression levels of ANXA2 were analyzed by western blotting and real-time polymerase chain reaction, respectively. Cell proliferation (cell counting kit-8 assay), apoptosis (flow cytometry analysis), the expression (western blotting) and the activity of caspases (enzyme-linked immunosorbent assay) were used to assess the effects of silencing ANXA2 on HUVECs in vitro.

RESULTS

The plasmids to express ANXA2-specific shRNA were constructed and were infected into HUVEC resulting in the stably transfected experimental (ANXA2-shRNA), control (control-shRNA) and mock (no plasmid) cell lines, which were verified with western blot and real-time PCR. HUVEC/ANXA2-shRNA showed an inhibition rate 91.89% of ANXA2 expression compared to the mock HUVEC. ANXA2 silencing cell strain obviously presented a lower cell proliferation activity compared to the control and mock HUVECs, with an inhibition rate 82.35% on day 7 in vitro. FACS analysis indicated that the HUVEC/ANXA2-shRNA cells undergoing apoptosis increased by 102.61% compared to the mock HUVECs (P < 0.01). Moreover, the activity levels of caspase-3, caspase-8 and caspase-9 in HUVEC/ANXA2-shRNA cells were increased and the activated cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9 were upregulated evidently compared with that of the control and mock HUVECs by 56.29%, 89.59% and 144.58% (P < 0.01).

CONCLUSIONS

shRNA-mediated silencing of ANXA2 could not only be able to suppress HUVECs proliferation but to upregulate the enzyme activity of caspases, which bring to an increase of cell apoptosis. This work suggested that ANXA2 may represent a useful target of future molecular therapies.

Association of annexin A2 with cancer development (Review)

Annexin A2 (ANXA2) is a well-known calcium-dependent phospholipid binding protein widely distributed in the nucleus, cytoplasm and extracellular surface of various eukaryotic cells. It has been recognized as a pleiotropic protein affecting a wide range of molecular and cellular processes. Dysregulation and abnormal expression of ANXA2 are linked to a large number of prevalent diseases, including autoimmune and neurodegenerative disease, antiphospholipid syndrome, inflammation, diabetes mellitus and a series of cancers. Accumulating data suggest that ANXA2 is aberrantly expressed in a wide spectrum of cancers, and exerts profound effects on tumor cell adhesion, proliferation, apoptosis, invasion and metastasis as well as tumor neovascularization via different modes of action. However, despite significant research, our knowledge of the mechanism by which ANXA2 participates in cancer development remains fragmented. The present review systematically summarizes the effects of ANXA2 on tumor progression, in an attempt to gain an improved understanding of the underlying mechanisms and to provide a potential effective target for cancer therapy.

Impaired osteoblast differentiation in annexin A2- and -A5-deficient cells

Annexins are a class of calcium-binding proteins with diverse functions in the regulation of lipid rafts, inflammation, fibrinolysis, transcriptional programming and ion transport. Within bone, they are well-characterized as components of mineralizing matrix vesicles, although little else is known as to their function during osteogenesis. We employed shRNA to generate annexin A2 (AnxA2)- or annexin A5 (AnxA5)-knockdown pre-osteoblasts, and determined whether proliferation or osteogenic differentiation was altered in knockdown cells, compared to pSiren (Si) controls. We report that DNA content, a marker of proliferation, was significantly reduced in both AnxA2 and AnxA5 knockdown cells. Alkaline phosphatase expression and activity were also suppressed in AnxA2- or AnxA5-knockdown after 14 days of culture. The pattern of osteogenic gene expression was altered in knockdown cells, with Col1a1 expressed more rapidly in knock-down cells, compared to pSiren. In contrast, Runx2, Ibsp, and Bglap all revealed decreased expression after 14 days of culture. In both AnxA2- and AnxA5-knockdown, interleukin-induced STAT6 signaling was markedly attenuated compared to pSiren controls. These data suggest that AnxA2 and AnxA5 can influence bone formation via regulation of osteoprogenitor proliferation, differentiation, and responsiveness to cytokines in addition to their well-studied function in matrix vesicles.

Cathepsin B: multiple roles in cancer

Proteases, including intracellular proteases, play roles at many different stages of malignant progression. Our focus here is cathepsin B, a lysosomal cysteine cathepsin. High levels of cathepsin B are found in a wide variety of human cancers, levels that often induce secretion and association of cathepsin B with the tumor cell membrane. In experimental models, such as transgenic models of murine pancreatic and mammary carcinomas, causal roles for cathepsin B have been demonstrated in initiation, growth/tumor cell proliferation, angiogenesis, invasion, and metastasis. Tumor growth in transgenic models is promoted by cathepsin B in tumor-associated cells, for example, tumor-associated macrophages, as well as in tumor cells. In transgenic models, the absence of cathepsin B has been associated with enhanced apoptosis, yet cathepsin B also has been shown to contribute to apoptosis. Cathepsin B is part of a proteolytic pathway identified in xenograft models of human glioma; targeting only cathepsin B in these tumors is less effective than targeting cathepsin B in combination with other proteases or protease receptors. Understanding the mechanisms responsible for increased expression of cathepsin B in tumors and association of cathepsin B with tumor cell membranes is needed to determine whether targeting cathepsin B could be of therapeutic benefit.

Significance of expression of PKCα, Annexin A2 and S100A10 proteins in gastric cancer

AIM: To investigate the clinical significance of expression of protein kinase C (PKC), Annexin A2 and S100A10 proteins in gastric cancer and provide valuable data for finding diagnosis related proteins in gastric cancer.

METHODS: The expression of PKCα, Annexin A2 and S100A10 proteins was detected by Western blot in normal gastric mucosa and gastric cancer tissues. Moreover, their expression was analyzed by immunohistochemistry in a tissue array containing normal gastric mucosa and gastric cancer tissues. The clinicopathologic significance of their expression was evaluated.

RESULTS: Western blot analysis showed that the expression of PKCα, Annexin A2 and S100A10 proteins was significantly higher in gastric cancer tissue than in normal gastric mucosa tissue (P < 0.01 for all). Immunohistochemistry analysis showed that the positive expression rates of PKCα, Annexin A2 and S100A10 proteins were significantly lower in normal gastric mucosa tissue than in gastric cancer tissue [8.82% (3/34) vs 76.54% (62/81), 5.88% (2/34) vs 79.01% (64/81), 2.94% (1/34) vs 59.26% (48/81); P < 0.01 for all].

CONCLUSION: The expression of PKCα, Annexin A2 and S100A10 proteins is up-regulated in gastric cancer tissue compared with normal gastric mucosa tissue and may be related with the occurrence and differentiation degree of gastric cancer.

Annexin A2: its molecular regulation and cellular expression in cancer development

Annexin A2 (ANXA2) orchestrates multiple biologic processes and clinical associations, especially in cancer progression. The structure of ANXA2 affects its cellular localization and function. However, posttranslational modification and protease-mediated N-terminal cleavage also play critical roles in regulating ANXA2. ANXA2 expression levels vary among different types of cancers. With some cancers, ANXA2 can be used for the detection and diagnosis of cancer and for monitoring cancer progression. ANXA2 is also required for drug-resistance. This review discusses the feasibility of ANXA2 which is active in cancer development and can be a therapeutic target in cancer management.

Annexin A2 silencing induces G2 arrest of non-small cell lung cancer cells through p53-dependent and -independent mechanisms

Annexin A2 (ANXA2) overexpression is required for cancer cell proliferation; however, the molecular mechanisms underlying ANXA2-mediated regulation of the cell cycle are still unknown. ANXA2 is highly expressed in non-small cell lung cancer (NSCLC) and is positively correlated with a poor prognosis. NSCLC A549 cells lacking ANXA2 exhibited defects in tumor growth in vivo and in cell proliferation in vitro without cytotoxicity. ANXA2 knockdown induced cell cycle arrest at G(2) phase. Unexpectedly, ANXA2 silencing increased the expression of p53 and its downstream genes, which resulted in p53-dependent and -independent G(2) arrest. Aberrant JNK inactivation, which was observed in ANXA2-deficient cells, inhibited cell proliferation following G(2) arrest. A lack of ANXA2 caused a loss of JNK-regulated c-Jun expression, resulting in an increase in p53 transcription. These results demonstrate a novel role for ANXA2 in NSCLC cell proliferation by facilitating the cell cycle partly through the regulation of p53 via JNK/c-Jun.