Akt2 is required for macrophage chemotaxis

Breast cancer-derived exosomal miR-105-5p facilitates the transformation of NFs into CAFs through LATS2-NF-κB signaling

Studies of cell-to-cell activities in the tumor microenvironment (TME) have identified multiple potential targets for oncotherapy. The interplay between tumor cells and neighboring cancer-associated fibroblasts (CAFs) persists in all stages of tumor progression. In this study, we reveal that exosomes from breast cancer cells can be endocytosed into fibroblasts and transform normal fibroblasts (NFs) into CAFs and that the ability of exosomes from highly metastatic breast cancer cells is greater than that of those from poorly metastatic breast cancer cells. Further investigation reveals that exosomes from highly metastatic breast cancer cells contain much more miR-105-5p than those from poorly metastatic breast cells do and that exosomal miR-105-5p facilitates the transformation of NFs to CAFs. A detailed study reveals that RBMY1A1-dependent sorting of miR-105-5p into fibroblasts and subsequent internalization of miR-105-5p promote the transformation of NFs to CAFs by downregulating LATS2 expression and activating NF-κB signaling, which concurrently facilitates the EMT of breast cancer cells. Thus, our results indicate that exosomal miR-105-5p may be a potential target for novel therapeutic strategies to prevent the coevolution of breast cancer cells and CAFs.

Integrins and integrin-driven secretory pathways as multi-dimensional regulators of tumor-associated macrophage recruitment and reprogramming in tumor microenvironment

Integrins, a group of transmembrane receptors, play a crucial role in mediating the interactions between cells and extracellular matrix (ECM) proteins. The intracellular signaling initiated by these cell-matrix interactions in leukocytes mediates many essential cellular processes such as survival, migration, metabolism, and other immunological functions. Macrophages, as phagocytes, participate in both proinflammatory and anti-inflammatory processes, including progression. Numerous reports have shown that the integrin-regulated secretome, comprising cytokines, chemokines, growth factors, proteases, and other bioactive molecules, is a crucial modulator of macrophage functions in tumors, significantly influencing macrophage programming and reprogramming within the tumor microenvironment (TME) in addition to driving their step-by-step entry process into tumor tissue spaces. Importantly, studies have demonstrated a pivotal role for integrin receptor-mediated secretome and associated signaling pathways in functional reprogramming from anti-tumorigenic to pro-tumorigenic phenotype in tumor-associated macrophages (TAMs). In this comprehensive review, we have provided an in-depth analysis of the latest findings of various key pathways, mediators, and signaling cascades associated with integrin-driven polarization of macrophages in tumors. This manuscript will provide an updated understanding of the modulation of inflammatory monocytes/ macrophages and TAMs by integrin-driven secretory pathways in various functions such as migration, differentiation, and their role in tumor progression, angiogenesis, and metastasis.

AKT kinases as therapeutic targets

AKT, or protein kinase B, is a central node of the PI3K signaling pathway that is pivotal for a range of normal cellular physiologies that also underlie several pathological conditions, including inflammatory and autoimmune diseases, overgrowth syndromes, and neoplastic transformation. These pathologies, notably cancer, arise if either the activity of AKT or its positive or negative upstream or downstream regulators or effectors goes unchecked, superimposed on by its intersection with a slew of other pathways. Targeting the PI3K/AKT pathway is, therefore, a prudent countermeasure. AKT inhibitors have been tested in many clinical trials, primarily in combination with other drugs. While some have recently garnered attention for their favorable profile, concern over resistance and off-target effects have continued to hinder their widespread adoption in the clinic, mandating a discussion on alternative modes of targeting. In this review, we discuss isoform-centric targeting that may be more effective and less toxic than traditional pan-AKT inhibitors and its significance for disease prevention and treatment, including immunotherapy. We also touch on the emerging mutant- or allele-selective covalent allosteric AKT inhibitors (CAAIs), as well as indirect, novel AKT-targeting approaches, and end with a briefing on the ongoing quest for more reliable biomarkers predicting sensitivity and response to AKT inhibitors, and their current state of affairs.

POSTN Secretion by Extracellular Matrix Cancer-Associated Fibroblasts (eCAFs) Correlates with Poor ICB Response via Macrophage Chemotaxis Activation of Akt Signaling Pathway in Gastric Cancer

Immune checkpoint blockade (ICB) therapy has revolutionized cancer treatment, but its clinical benefit is limited in advanced gastric cancer (GC). Cancer-associated fibroblasts (CAFs) have been reported to be associated with ICB resistance, but the underlying mechanism has not been fully elucidated. Our previous single-cell RNA-seq analysis of GC revealed that POSTN+FAP+ extracellular matrix CAFs (eCAFs) communicate with macrophages. Here, we evaluated the correlation between eCAFs and ICB response in TCGA-STAD and real-world cohorts. Immune infiltration analysis and correlation analysis were performed to assess the relationship between eCAFs and macrophages. We first confirmed a negative correlation between the abundance of eCAFs and the overall response rate (ORR) to anti-PD-1 treatment in TCGA-STAD and real-world GC cohorts. Overexpression of POSTN in CAFs enhanced macrophage chemotaxis, while POSTN interference showed the opposite effect in vitro and in vivo. Furthermore, the cell density of POSTN+ CAFs was positively correlated with the infiltration level of CD163+ macrophages in GC patient tissues. The results demonstrated that POSTN secreted by CAFs enhances macrophage chemotaxis by activating the Akt signaling pathway in macrophages. Additionally, we found that POSTN+FAP+ eCAFs may exist in multiple solid tumors and are associated with ICB resistance. eCAFs promote macrophage chemotaxis through the secretion of POSTN, thereby leading to ICB resistance. High expression of POSTN is likely to predict a poor response to ICB. POSTN downregulation may be considered as a candidate therapeutic strategy to improve ICB efficacy.

Hsa_circRNA_103124 upregulation in Crohn's disease promoted macrophage M1 polarization to maintain an inflammatory microenvironment via activation of the AKT2 and TLR4/NF-κB pathways

An accumulating body of research indicates that circular RNAs participate in the pathogenesis of Crohn's disease (CD). Hsa_circRNA_103124, which was upregulated in the peripheral blood mononuclear cells of patients with CD, was reported to inhibit autophagy in our previous studies. However, how hsa_circRNA_103124 participates in CD progression remains unclear. In this study, TLR4 was found to be upregulated in THP1 cells overexpressing hsa_circRNA_103124. Bioinformatic analysis indicated that overexpressed hsa_circRNA_103124 was associated with the PI3K/AKT signaling pathway and TLR4-associated innate immunity in inflammatory bowel disease. Therefore, we inferred a possible role for hsa_circRNA_103124 in macrophage polarization. Hsa_circRNA_103124, AKT2 and TLR4 were significantly upregulated in the PBMCs of patients with CD. Further analysis revealed a positive correlation between hsa_circRNA_103124 and AKT2 (r = 0.8029, p < 0.0001), TLR4 (r = 0.2529, p = 0.0089) and the Crohn's disease activity index (r = 0.4535, p < 0.0001) in patients with CD. Notably, hsa_circRNA_103124 promoted macrophage M1 polarization with increased expression of CD80 and CD86, while it inhibited macrophage M2 polarization with decreased expression of CD206 and CD163. Hsa_circRNA_103124 promoted an inflammatory microenvironment by activating the AKT2 and TLR4/NF-κB signaling pathways in M1 polarized THP1 cells. Nevertheless, hsa-miR-650 reversed the role of hsa_circRNA_103124 in M1 polarization. Hsa_circRNA_103124 promoted the formation of neutrophil extracellular traps and reduced the expression of ZO-1. In summary, the results of this study indicated that hsa_circRNA_103124 promoted macrophage M1 polarization to maintain an inflammatory microenvironment via activation of the TLR4/NF-κB pathway in a hsa-miR-650/AKT2 dependent manner. Hsa_circRNA_103124 could serve as a potential biomarker and a novel therapeutic target in CD progression.

Macrophages in the Inflammatory Phase following Myocardial Infarction: Role of Exogenous Ubiquitin

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. One of the most common implications of CVD is myocardial infarction (MI). Following MI, the repair of the infarcted heart occurs through three distinct, yet overlapping phases of inflammation, proliferation, and maturation. Macrophages are essential to the resolution of the inflammatory phase due to their role in phagocytosis and efferocytosis. However, excessive and long-term macrophage accumulation at the area of injury and dysregulated function can induce adverse cardiac remodeling post-MI. Ubiquitin (UB) is a highly evolutionarily conserved small protein and is a normal constituent of plasma. Levels of UB are increased in the plasma during a variety of pathological conditions, including ischemic heart disease. Treatment of mice with UB associates with decreased inflammatory response and improved heart function following ischemia/reperfusion injury. This review summarizes the role of macrophages in the infarct healing process of the heart post-MI, and discusses the role of exogenous UB in myocardial remodeling post-MI and in the modulation of macrophage phenotype and function.

Hyptis obtusiflora C. Presl ex Benth Methanolic Extract Exhibits Anti-Inflammatory and Anti-Gastritis Activities via Suppressing AKT/NF-κB Pathway

Inflammation is an indispensable part of the human body's self-defense mechanism against external stimuli. The interactions between Toll-like receptors and microbial components trigger the innate immune system via NF-κB signaling, which regulates the overall cell signaling including inflammatory responses and immune modulations. The anti-inflammatory effects of Hyptis obtusiflora C. Presl ex Benth, which has been used as a home remedy for gastrointestinal disorders and skin disease in rural areas of Latin America, have not yet been studied. Here, we investigate the medicinal properties of Hyptis obtusiflora C. Presl ex Benth methanol extract (Ho-ME) for inflammatory response suppression. Nitric oxide secretion in RAW264.7 cells triggered by TLR2, 3, or 4 agonists was reduced by Ho-ME. Reduction of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, and interleukin (IL)-1b mRNA expression was observed. Decreased transcriptional activity in TRIF- and MyD88-overexpressing HEK293T cells was detected with a luciferase assay. Additionally, serially downregulated phosphorylation of kinase in the NF-κB pathway by Ho-ME was discovered in lipopolysaccharide-treated RAW264.7 cells. Together with the overexpression of its constructs, AKT was identified as a target protein of Ho-ME, and its binding domains were reaffirmed. Moreover, Ho-ME exerted gastroprotective effects in an acute gastritis mouse model generated by the administration of HCl and EtOH. In conclusion, Ho-ME downregulates inflammation via AKT targeting in the NF-κB pathway, and the combined results support Hyptis obtusiflora as a new candidate anti-inflammatory drug.

Ranitidine as an adjuvant regulates macrophage polarization and activates CTLs through the PI3K-Akt2 signaling pathway

Adjuvants are an indispensable component of vaccines, but there are few adjuvants for human vaccines. H2 receptor blockers, inhibiting gastric acid secretion, have immune enhancement effects. Ranitidine (RAN) is a water-soluble H2 receptor blocker, and whether it has an immune-enhancing effect is still unknown. In this study, flow cytometry, western blotting, and immunofluorescence methods were used to analyze whether RAN could activate macrophage polarization to the M1 phenotype in vivo and in vitro. Here, we found that the M1 inflammatory cytokine levels and surface markers in RAW264.7 cells were upregulated by NF-κB activation, possibly through the PI3K-Akt2 signaling pathway, after RAN treatment. Endocytic function was also enhanced by feedback regulation of Akt2/GSK3β/Dynmin1 signaling. Furthermore, to evaluate the adjuvant function of RAN, we used OVA plus RAN as a vaccine to inhibit the growth of B16-OVA tumors in mice. We also found that in the RAN adjuvant group, macrophage polarization to M1, Th1 cell differentiation, and cytotoxic T lymphocyte (CTL) activation were significantly upregulated. The tumor growth of mice was inhibited, and the survival rate of mice was significantly improved. This study provides new evidence for the mechanism by which RAN activates the immune response and is expected to provide a new strategy for the research and development of tumor vaccine adjuvants.

AKT2 reduces IFNβ1 production to modulate antiviral responses and systemic lupus erythematosus

Interferon regulatory factor 3 (IRF3)-induced type I interferon (I-IFN) production plays key roles in both antiviral and autoimmune responses. IRF3 phosphorylation, dimerization, and nuclear localization are needed for its activation and function, but the precise regulatory mechanisms remain to be explored. Here, we show that the serine/threonine kinase AKT2 interacts with IRF3 and phosphorylates it on Thr207, thereby attenuating IRF3 nuclear translocation in a 14-3-3ε-dependent manner and reducing I-IFN production. We further find that AKT2 expression is downregulated in viral-infected macrophages or in monocytes and tissue samples from systemic lupus erythematosus (SLE) patients and mouse models. Akt2-deficient mice exhibit increased I-IFN induction and reduced mortality in response to viral infection, but aggravated severity of SLE. Overexpression of AKT2 kinase-inactive or IRF3-T207A mutants in zebrafish supports that AKT2 negatively regulates I-IFN production and antiviral response in a kinase-dependent manner. This negative role of AKT2 in IRF3-induced I-IFN production suggests that AKT2 may be therapeutically targeted to differentially regulate antiviral infection and SLE.

AKT Isoforms in the Immune Response in Cancer

AKT is a protein kinase that exists in three isoforms: AKT1, AKT2, and AKT3. Though similar in structure, these isoforms display different effects. AKT is activated downstream of PI3K, and together, this signaling pathway helps regulate cellular processes including cell growth, proliferation, metabolism, survival, and apoptosis. Disruption in these pathways has been associated with disorders including cardiovascular diseases, developmental disorders, inflammatory responses, autoimmune diseases, neurologic disorders, type 2 diabetes, and several cancers. In cancer, deregulation in the PI3K/AKT pathway can be manifested as tumorigenesis, pathological angiogenesis, and metastasis. Increased activity has been correlated with tumor progression and resistance to cancer treatments. Recent studies have suggested that inhibition of the PI3K/AKT pathway plays a significant role in the development, expansion, and proliferation of cells of the immune system. Additionally, AKT has been found to play an important role in differentiating regulatory T cells, activating B cells, and augmenting tumor immunosurveillance. This emphasizes AKT as a potential target for inhibition in cancer therapy. This chapter reviews AKT structure and regulation, its different isoforms, its role in immune cells, and its modulation in oncotherapy.

The immunomodulatory effects of endocrine therapy in breast cancer

Endocrine therapies with SERMs (selective estrogen receptor modulators) or SERDs (selective estrogen receptor downregulators) are standard therapies for patients with estrogen receptor (ER)-positive breast cancer. Multiple small molecule inhibitors targeting the PI3K-AKT-mTOR pathway or CDK4/6 have been developed to be used in combination with anti-estrogen drugs to overcome endocrine resistance. In addition to their direct antitumor effects, accumulating evidence has revealed the tumor immune microenvironment (TIM)-modulating effects of these therapeutic strategies, which have not been properly acknowledged previously. The immune microenvironment of breast tumors plays a crucial role in tumor development, metastasis and treatment response to endocrine therapy and immunotherapy. Therefore, in our current work, we comprehensively review the immunomodulatory effect of endocrine therapy and discuss its potential applications in combination with immune checkpoint inhibitors in breast cancer treatment.

Anti-Inflammatory Activity of Extracts and Pure Compounds Derived from Plants via Modulation of Signaling Pathways, Especially PI3K/AKT in Macrophages

The plant kingdom is a source of important therapeutic agents. Therefore, in this review, we focus on natural compounds that exhibit efficient anti-inflammatory activity via modulation signaling transduction pathways in macrophage cells. Both extracts and pure chemicals from different species and parts of plants such as leaves, roots, flowers, barks, rhizomes, and seeds rich in secondary metabolites from various groups such as terpenes or polyphenols were included. Selected extracts and phytochemicals control macrophages biology via modulation signaling molecules including NF-κB, MAPKs, AP-1, STAT1, STAT6, IRF-4, IRF-5, PPARγ, KLF4 and especially PI3K/AKT. Macrophages are important immune effector cells that take part in antigen presentation, phagocytosis, and immunomodulation. The M1 and M2 phenotypes are related to the production of pro- and anti-inflammatory agents, respectively. The successful resolution of inflammation mediated by M2, or failed resolution mediated by M1, may lead to tissue repair or chronic inflammation. Chronic inflammation is strictly related to several disorders. Thus, compounds of plant origin targeting inflammatory response may constitute promising therapeutic strategies.

Mechanobiology of Macrophages: How Physical Factors Coregulate Macrophage Plasticity and Phagocytosis

In addition to their early-recognized functions in host defense and the clearance of apoptotic cell debris, macrophages play vital roles in tissue development, homeostasis, and repair. If misregulated, they steer the progression of many inflammatory diseases. Much progress has been made in understanding the mechanisms underlying macrophage signaling, transcriptomics, and proteomics, under physiological and pathological conditions. Yet, the detailed mechanisms that tune circulating monocytes/macrophages and tissue-resident macrophage polarization, differentiation, specification, and their functional plasticity remain elusive. We review how physical factors affect macrophage phenotype and function, including how they hunt for particles and pathogens, as well as the implications for phagocytosis, autophagy, and polarization from proinflammatory to prohealing phenotype. We further discuss how this knowledge can be harnessed in regenerative medicine and for the design of new drugs and immune-modulatory drug delivery systems, biomaterials, and tissue scaffolds.

AKT2 deficiency impairs formation of the BCR signalosome

BACKGROUND

AKT2 is one of the key molecules that involves in the insulin-induced signaling and the development of cancer. In B cells, the function of AKT2 is unclear.

METHODS

In this study, we used AKT2 knockout mice model to study the role of AKT2 in BCR signaling and B cell differentiation.

RESULTS

AKT2 promotes the early activation of B cells by enhancing the BCR signaling and actin remodeling. B cells from AKT2 KO mice exhibited defective spreading and BCR clustering upon stimulation in vitro. Disruption of Btk-mediated signaling caused the impaired differentiation of germinal center B cells, and the serum levels of both sepecific IgM and IgG were decreased in the immunized AKT2 KO mice. In addition, the actin remodeling was affected due to the decreased level of the activation of WASP, the actin polymerization regulator, in AKT2 KO mice as well. As a crucial regulator of both BCR signaling and actin remodeling during early activation of B cells, the phosphorylation of CD19 was decreased in the AKT2 absent B cells, while the transcription level was normal.

CONCLUSIONS

AKT2 involves in the humoral responses, and promotes the BCR signaling and actin remodeling to enhance the activation of B cells via regulating CD19 phosphorylation. Video Abstract.

The role of C1QBP in CSF-1-dependent PKCζ activation and macrophage migration

Macrophages view as double agents in tumor progression. Trafficking of macrophages to the proximity of tumors is mediated by colony-stimulating factor-1 (CSF-1), a growth factor. In this study, we investigated the role of complement1q-binding protein (C1QBP)/ atypical protein kinase C ζ (PKCζ) in CSF-1-induced macrophage migration. Disruption of C1QBP expression impaired chemotaxis and adhesion of macrophage. Phosphorylation of PKCζ is an essential component in macrophage chemotaxis signaling pathway. C1QBP could interact with PKCζ in macrophage. C1QBP knockdown inhibited CSF-1 induced phosphorylation of PKCζ and integrin-β1. However, C1QBP knockdown didn't affect the phosphorylation of PKCζ induced by MCP-1. Furthermore, CSF-1 from RCC cell condition medium promoted macrophage chemotaxis and adhesion. Taken together, our results demonstrated that C1QBP plays an essential role in CSF-1 induced migration of macrophages.

Akt Signaling Pathway in Macrophage Activation and M1/M2 Polarization

Macrophages become activated initiating innate immune responses. Depending on the signals, macrophages obtain an array of activation phenotypes, described by the broad terms of M1 or M2 phenotype. The PI3K/Akt/mTOR pathway mediates signals from multiple receptors including insulin receptors, pathogen-associated molecular pattern receptors, cytokine receptors, adipokine receptors, and hormones. As a result, the Akt pathway converges inflammatory and metabolic signals to regulate macrophage responses modulating their activation phenotype. Akt is a family of three serine-threonine kinases, Akt1, Akt2, and Akt3. Generation of mice lacking individual Akt, PI3K, or mTOR isoforms and utilization of RNA interference technology have revealed that Akt signaling pathway components have distinct and isoform-specific roles in macrophage biology and inflammatory disease regulation, by controlling inflammatory cytokines, miRNAs, and functions including phagocytosis, autophagy, and cell metabolism. Herein, we review the current knowledge on the role of the Akt signaling pathway in macrophages, focusing on M1/M2 polarization and highlighting Akt isoform-specific functions.

PKB/Akt-dependent regulation of inflammation in cancer

Chronic inflammation is a major cause of human cancer. Clinical cancer therapies against inflammatory risk factors are strategically determined. To rationally guide a novel drug development, an improved mechanistic understanding on the pathological connection between inflammation and carcinogenesis is essential. PI3K-PKB signaling axis has been extensively studied and shown to be one of the key oncogenic drivers in most types of cancer. Pharmacological inhibition of the components along this signaling axis is of great interest for developing novel therapies. Interestingly, emerging studies have shown a close association between PKB activation and inflammatory activity in the vicinity of the tumor, and either blockade of PKB or attenuation of para-tumoral inflammation reveals a mutual-interactive pattern through pathway crosstalk. In this review, we intend to discuss recent advances of PKB-regulated chronic inflammation and its potential impacts on tumor development.

MiR-204 inhibits human NSCLC metastasis through suppression of NUAK1

BACKGROUND

Lung cancer is a leading cause of cancer-related mortality worldwide and non-small-cell lung carcinoma (NSCLC) is responsible for almost 80% of lung cancer-related deaths. Identifying novel molecules that can repress the invasiveness and metastasis of lung cancer will facilitate the development of new antilung cancer strategies. The aim of this study is to determine the roles of NUAK1 (a downstream of Akt) and miR-204 in the invasiveness and metastasis of NSCLC and to reveal the correlation between NUAK1 and miR-204.

METHODS

The expression of NUAK1 in primary human NSCLC tissues was evaluated by immunohistochemistry. Real-time PCR was employed to measure the expression level of miR-204. The effect of NUAK1 and miR204 on the prognosis of NSCLC patients was evaluated by log-rank test. The siRNA transfection was used to manipulate the expression levels of NUAK1 and miR204 in cancer cells. Chemotaxis assay, Scratch assay, and Matrigel invasion assay were performed to evaluate the migration and invasion of cells. Cellular F-actin measurement was used to measure F-actin polymerisation in lung cancer cells. Western blot was used to detect the expression levels of corresponding proteins. The Luciferase assay and RNA immunoprecipitation were used to confirm the actual binding site of miR-204 to 3'UTR of NUAK1.

RESULTS

Increased expression of NUAK1 is correlated with the invasiveness and metastasis of human NSCLC. Knockdown of NUAK1 inhibited cell migration and invasion. In addition, this study showed that NUAK1 influenced mTOR phosphorylation and induced the phosphorylation of p70S6K1 and eukaryotic initiation factor 4E-binding protein1 (4E-BP1), two downstream targets of mTOR in NSCLC cells. At the same time, decreased expression of miR-204 promoted NSCLC progression and, contrarily, manipulated upregulation of miR-204-inhibited cell migration and invasion. There is clinical relevance between miR-204 downregulation and NUAK1 upregulation in human NSCLC. Furthermore, we found that miR-204 inhibited NSCLC tumour invasion by directly targeting and downregulating NUAK1 expression. Finally, our data suggested that the downregulation of miR-204 was due to hypermethylation of its promoter region.

CONCLUSIONS

Our results indicate that NUAK1 is excessively expressed in NSCLC and plays important roles in NSCLC invasion. The miR-204 acts as a tumour suppressor by inhibiting NUAK1 expression in NSCLC. Both NUAK1 and miR-204 may serve as potential targets of NSCLC therapy.

Hematopoietic Akt2 deficiency attenuates the progression of atherosclerosis

Atherosclerosis is the major cause of death and disability in diabetic and obese subjects with insulin resistance. Akt2, a phosphoinositide-dependent serine-threonine protein kinase, is highly express in insulin-responsive tissues; however, its role during the progression of atherosclerosis remains unknown. Thus, we aimed to investigate the contribution of Akt2 during the progression of atherosclerosis. We found that germ-line Akt2-deficient mice develop similar atherosclerotic plaques as wild-type mice despite higher plasma lipids and glucose levels. It is noteworthy that transplantation of bone marrow cells isolated from Akt2(-/-) mice to Ldlr(-/-) mice results in marked reduction of the progression of atherosclerosis compared with Ldlr(-/-) mice transplanted with wild-type bone marrow cells. In vitro studies indicate that Akt2 is required for macrophage migration in response to proatherogenic cytokines (monocyte chemotactic protein-1 and macrophage colony-stimulating factor). Moreover, Akt2(-/-) macrophages accumulate less cholesterol and have an alternative activated or M2-type phenotype when stimulated with proinflammatory cytokines. Together, these results provide evidence that macrophage Akt2 regulates migration, the inflammatory response and cholesterol metabolism and suggest that targeting Akt2 in macrophages might be beneficial for treating atherosclerosis.

Macrophage deficiency of Akt2 reduces atherosclerosis in Ldlr null mice

Macrophages play crucial roles in the formation of atherosclerotic lesions. Akt, a serine/threonine protein kinase B, is vital for cell proliferation, migration, and survival. Macrophages express three Akt isoforms, Akt1, Akt2, and Akt3, but the roles of Akt1 and Akt2 in atherosclerosis in vivo remain unclear. To dissect the impact of macrophage Akt1 and Akt2 on early atherosclerosis, we generated mice with hematopoietic deficiency of Akt1 or Akt2. After 8 weeks on Western diet, Ldlr^−/− mice reconstituted with Akt1^−/− fetal liver cells (Akt1^−/−→Ldlr^−/−) had similar atherosclerotic lesion areas compared with control mice transplanted with WT cells (WT→Ldlr^−/−). In contrast, Akt2^−/−→Ldlr^−/− mice had dramatically reduced atherosclerotic lesions compared with WT→Ldlr^−/− mice of both genders. Similarly, in the setting of advanced atherosclerotic lesions, Akt2^−/−→Ldlr^−/− mice had smaller aortic lesions compared with WT→Ldlr^−/− and Akt1^−/−→Ldlr^−/− mice. Importantly, Akt2^−/−→Ldlr^−/− mice had reduced numbers of proinflammatory blood monocytes expressing Ly-6C^hi and chemokine C-C motif receptor 2. Peritoneal macrophages isolated from Akt2^−/− mice were skewed toward an M2 phenotype and showed decreased expression of proinflammatory genes and reduced cell migration. Our data demonstrate that loss of Akt2 suppresses the ability of macrophages to undergo M1 polarization reducing both early and advanced atherosclerosis.

CSF-1 receptor signaling in myeloid cells

The CSF-1 receptor (CSF-1R) is activated by the homodimeric growth factors colony-stimulating factor-1 (CSF-1) and interleukin-34 (IL-34). It plays important roles in development and in innate immunity by regulating the development of most tissue macrophages and osteoclasts, of Langerhans cells of the skin, of Paneth cells of the small intestine, and of brain microglia. It also regulates the differentiation of neural progenitor cells and controls functions of oocytes and trophoblastic cells in the female reproductive tract. Owing to this broad tissue expression pattern, it plays a central role in neoplastic, inflammatory, and neurological diseases. In this review we summarize the evolution, structure, and regulation of expression of the CSF-1R gene. We discuss the structures of CSF-1, IL-34, and the CSF-1R and the mechanism of ligand binding to and activation of the receptor. We further describe the pathways regulating macrophage survival, proliferation, differentiation, and chemotaxis downstream from the CSF-1R.

Nir1 promotes invasion of breast cancer cells by binding to chemokine (C-C motif) ligand 18 through the PI3K/Akt/GSK3β/Snail signalling pathway

Chemokine (C-C motif) ligand 18 (CCL18), which is derived from tumour-associated macrophages (TAMs), plays a critical role in promoting breast cancer metastasis via its receptor, PYK2 N-terminal domain interacting receptor 1 (Nir1). However, the molecular mechanism by which Nir1 promotes breast cancer metastasis by binding to CCL18 remains elusive. In this study, Nir1 expression was associated with lymph node and distant metastasis in patients with invasive ductal carcinoma. For the first time, we report that Nir1 binding to CCL18 promotes the phosphorylation of Akt, LIN-11, Isl1 and MEC-3 protein domain kinase (LIMK), and cofilin, which is a critical step in cofilin recycling and actin polymerisation. Interestingly, Nir1 binding to CCL18 can enhance cell mesenchymal properties and induce epithelial-mesenchymal transition (EMT). Mechanistically, Nir1 binding to CCL18 stabilises Snail via the Akt/GSK3β signalling pathway. In support of these observations, Nir1 binding to CCL18 promoted lung metastasis and LY294002 could inhibit it in vivo. In summary, our in vitro and in vivo results indicate that Nir1 binding to CCL18 plays an important role in breast cancer invasion/metastasis. This study identified both Nir1 and CCL18 as potential anti-invasion targets for therapeutic intervention in breast cancer.

Gab2 expression in glioma and its implications for tumor invasion

Gliomas are characterized by high invasiveness and poor prognosis. Better understanding of the mechanism of invasion in glioma cells is essential to the design of effective therapy. Recently Grb2-associated binder 2 (Gab2), a member of the DOS/Gab family of scaffolding adapters, has been reported to play important roles in the development and progression of human cancers. However, it is not known whether Gab2 has any role in the migration and invasion of gliomas. This study attempts to investigate the association between Gab2 expression and progression of gliomas and the molecular mechanism of Gab2 in the glioma cell invasion. Methods. The expression of Gab2 in pairs of matched glioma tissues and their normal brain tissues was detected by Western blot. Immunohistochemistry was applied to evaluate the expression of Gab2 in 163 cases of histologically diagnosed gliomas. The invasive character of Gab2 decreased glioma cells and control glioma cells were investigated in vitro and in vivo in SCID mice brain. Results. Gab2 is found to be high expressed in gliomas and a subset of cancer cell lines. Statistical analysis suggested that the up-regulation of Gab2 correlated with the WHO grade of gliomas (p < 0.01) and that patients with high Gab2 expression levels exhibited shorter survival time (p < 0.01). In an animal experiment, knockdown of Gab2 through siRNA inhibited invasive ability of glioma cells into the brain of SCID mice. In cell research, reduction of Gab2 by siRNA inhibits the migration and invasion of glioma cells by mediating cytoskeleton rearrangement and MMPs expression. Additionally, IGF-1-induced pAkt and pmTOR phosphorylation was suppressed by the knockdown of Gab2. Conclusion. Gab2 may be a useful prognostic marker for gliomas and a novel therapeutic target for glioma invasion intervention.

PTTG1 promotes migration and invasion of human non-small cell lung cancer cells and is modulated by miR-186

Deeper mechanistic understanding of non-small cell lung cancer (NSCLC), a leading cause of total cancer-related deaths, may facilitate the establishment of more effective therapeutic strategies. In this study, pituitary tumor transforming gene (PTTG1) expression was associated with lymph node and distant metastasis in patients with NSCLC and was correlated with patient survival. Reduction of PTTG1 by small interfering RNA (siRNA) inhibits the migration and invasion of NSCLC cells by mediating matrix metalloproteinases expression. To the best of our knowledge, this study is the first to report that PTTG1 promotes epidermal growth factor (EGF) induced the phosphorylation of LIN-11, Isl1 and MEC-3 protein domain kinase and cofilin, a critical step in cofilin recycling and actin polymerization. Additionally, EGF-induced Akt phosphorylation was suppressed through knockdown of PTTG1. Interestingly, miR-186 can modulate PTTG1 protein expression. As observed from the animal experiment in this study, knockdown of PTTG1 through siRNA and overexpression of miR-186 inhibited invasive activity of NSCLC cells toward the SCID mice lung. In summary, our in vitro and in vivo results indicate that PTTG1 modulated by miR-186 has an important function in NSCLC invasion/metastasis. This study identified both PTTG1 and miR-186 as potential anti-invasion targets for therapeutic intervention in NSCLC.

ARK5 promotes glioma cell invasion, and its elevated expression is correlated with poor clinical outcome

Poor prognosis of malignant gliomas is primarily attributed to their highly invasive nature. Despite the identification of new biomarkers and molecular targets for the improvement of the diagnosis, prognosis and treatment of glioma, the overall prognosis of the disease remains poor. This study is the first to show the significant upregulation of ARK5 paraffin-embedded archival glioma biopsies compared with those in adjacent non-cancerous brain tissues. Statistical analysis suggests that the upregulation of ARK5 correlates with the World Health Organization grade of glioma (P<0.001) and that patients with a high ARK5 level exhibit shorter survival time (P<0.01). In addition, ARK5 can promote glioma cell invasion by regulating cytoskeleton rearrangement and matrix metalloproteinase activation. ARK5 knockdown was found to reduce brain invasion in a glioma xenograft mouse model. Our results strongly suggest that ARK5 represents a novel and valuable biomarker to aid in the prediction of patient prognosis and is a potential therapeutic target against glioma.

Chemotaxis: movement, direction, control

This review focuses on basic principles of motility in different cell types, formation of the specific cell structures that enable directed migration, and how external signals are transduced into cells and coupled to the motile machinery. Feedback mechanisms and their potential role in maintenance of internal chemotactic gradients and persistence of directed migration are highlighted.

Adiponectin-AdipoR1/2-APPL1 signaling axis suppresses human foam cell formation: differential ability of AdipoR1 and AdipoR2 to regulate inflammatory cytokine responses

OBJECTIVE

Adiponectin is an adipokine that exerts anti-inflammatory and anti-atherogenic effects during macrophage transformation into foam cells. To further understand the signaling pathways of adiponectin involved in macrophage foam cell transformation, we investigated the roles of two adiponectin receptors (AdipoR1 and AdipoR2) and their downstream adaptor protein, phosphotyrosine interaction, PH domain and leucine zipper containing 1 (APPL1) in mediating adiponectin action on foam cell transformation.

METHODS AND RESULTS

Transfections were performed to overexpress or knockdown AdipoR1 or AdipoR2 genes in human THP-1 monocytes. Lentiviral-shRNAs were also used to knockdown APPL1 gene in these cells. Foam cell transformation was induced via exposure to oxidized low-density lipoprotein (oxLDL). Our results showed that both AdipoR1 and AdipoR2 were critical for transducing the adiponectin signal that suppresses lipid accumulation and inhibits transformation from macrophage to foam cell. However, AdipoR1 and AdipoR2 were found to have differential effects in diminishing proinflammatory responses. While AdipoR1 was required by adiponectin to suppress tumor necrosis factor alpha (TNFα) and monocyte chemotactic protein 1 (MCP-1) gene expression, AdipoR2 served as the dominant receptor for adiponectin suppression of scavenger receptor A type 1 (SR-AI) and upregulation of interleukin-1 receptor antagonist (IL-1Ra). Knockdown of APPL1 significantly abrogated the ability of adiponectin to inhibit lipid accumulation, SR-AI and nuclear factor-κB (NF-κB) gene expression, and Akt phosphorylation in macrophage foam cells.

CONCLUSIONS

In current studies, we have demonstrated that adiponectin's abilty to suppress macrophage lipid accumulation and foam cell formation is mediated through AdipoR1 and AdipoR2 and the APPL1 docking protein. However, AdipoR1 and AdipoR2 exhibited a differential ability to regulate inflammatory cytokines and SR-A1. These novel data support the idea that the adiponectin-AdipoR1/2-APPL1 axis may serve as a potential therapeutic target for preventing macrophage foam cell formation and atherosclerosis.

The role of PI3K/protein kinase B (PKB/c-akt) in migration and homing of hematopoietic stem and progenitor cells

PURPOSE OF REVIEW

Hematopoietic stem cell (HSC) transplantation is the most powerful treatment modality for a variety of hematological disorders. Successful hematopoietic recovery after transplantation depends on optimal homing of HSCs to the bone marrow and subsequent lodging in the HSC niche. The molecular mechanisms underlying bone marrow homing are, thus far, incompletely understood. This review focuses on recent studies that extended our understanding of how the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB/c-akt) signaling module can regulate migration and homing of HSCs.

RECENT FINDINGS

In addition to regulation of HSC maintenance and lineage development, it has recently become apparent that the PI3K/PKB signaling module plays a critical role in regulation of migration and adhesion of hematopoietic stem and progenitor cells. Activation of this signaling pathway enhances firm adhesion, reduces migration and inhibits bone marrow homing, whereas inhibition of PKB conversely induces bone marrow homing.

SUMMARY

These findings clearly implicate the PI3K/PKB signaling module in playing a critical role in regulation of bone marrow homing, suggesting that pharmacological modulation of this signaling molecule prior to transplantation may provide a clinical means of improving engraftment levels and accelerating hematopoietic recovery.

Myocardial injury after ischemia-reperfusion in mice deficient in Akt2 is associated with increased cardiac macrophage density

Akt2 protein kinase has been shown to promote cell migration and actin polymerization in several cell types, including macrophages. Because migrating macrophages constitute an important inflammatory response after myocardial ischemia, we determined cardiac macrophage expression after ischemia-reperfusion (I/R) injury and cryo-injury in mice lacking Akt2 (Akt2-KO). At 7 days post-I/R, Akt2-KO cardiac tissues showed an increase in immunohistochemical staining for macrophage markers (Galectin 3 and F4/80) compared with wild-type (WT) mice, indicating macrophage density was increased in the injured Akt2-KO myocardium. This change was time dependent because macrophage density was similar between WT and Akt2-KO myocardium at 3 days post-I/R, but by 7 and 14 days post-I/R, macrophage density was significantly increased in Akt2-KO myocardium. Concomitantly, infarct size was larger and cardiac function was reduced in Akt2-KO mice subjected to I/R. However, when cryo-infarction produced similar infarct sizes in the anterior wall in both WT and Akt2-KO mice, macrophage density remained higher in Akt2-KO mouse myocardium, suggesting Akt2 regulates myocardial macrophage density independent of infarct size. Consistently, bone marrow from Akt2-KO mice enhanced myocardial macrophage density in both C57/B6 WT and Akt2-KO recipient mice. Finally, reciprocal ex-vivo coculturing of macrophages and cardiac myocytes showed that activated Akt2-KO peritoneal macrophages had reduced mobility and adhesion when compared with WT littermate controls. Thus, although Akt-2 KO mice did not affect the initial inflammation response after injury and Akt2 deficiency has been shown to impair cell migration or motility in macrophages, our data suggested a novel mechanism in which increasing retention of Akt2-KO macrophages resulted in increasing cardiac Akt2-KO macrophage density in the myocardial space.

Regulation of tyrosine phosphorylation in macrophage phagocytosis and chemotaxis

Macrophages display a large variety of surface receptors that are critical for their normal cellular functions in host defense, including finding sites of infection (chemotaxis) and removing foreign particles (phagocytosis). However, inappropriate regulation of these processes can lead to human diseases. Many of these receptors utilize tyrosine phosphorylation cascades to initiate and terminate signals leading to cell migration and clearance of infection. Actin remodeling dominates these processes and many regulators have been identified. This review focuses on how tyrosine kinases and phosphatases regulate actin dynamics leading to macrophage chemotaxis and phagocytosis.

4-Methyl-3-nitro-benzoic acid, a migration inhibitor, prevents breast cancer metastasis in SCID mice

Metastasis remains a formidable problem in malignant tumors. In this study, MTT assay revealed that 4-methyl-3-nitro-benzoic acid (MNBA) had no effect on cell viability and did not interfere with cell cycle in any breast cancer cell lines tested. However, treatment with MNBA on breast cancer cells can inhibit EGF-induced migration and chemotaxis in vitro. In vivo assay demonstrated that MNBA and Paclitaxel synergistically inhibited tumor growth and metastasis in breast cancer SCID mice xenografts. These results suggest that MNBA is a potent inhibitor cancer cell chemotaxis and may be developed into a novel anti-metastasis drug.

LIM kinases are attractive targets with many macromolecular partners and only a few small molecule regulators

The LIM kinases 1 and 2 (LIMK1 and LIMK2) are dual specificity (serine/threonine and tyrosine) kinases. Although they show significant structural similarity, LIMK1 and LIMK2 show different expression, subcellular localization, and functions. They are involved in many cellular functions, such as migration, cycle, and neuronal differentiation and also have a role in pathological processes, such as cancer cell invasion and metastatis, as well as in neurodevelopmental disorders (namely, the William's syndrome). LIM kinases have a relevant number of known partners that are able to induce or limit the ability of LIMK1 and LIMK2 to phosphorylate and inactivate their major substrate, cofilin. On the contrary, only a limited number of small molecules that interact with the two proteins to modulate their kinase activity have been identified. In this review, the most important partners of LIM kinases and their modulating activity toward LIMKs are described. The small compounds identified as LIMK1 and LIMK2 modulators are also reported, as well as their role as possible therapeutic agents for LIMK-induced diseases.

Eukaryotic chemotaxis: a network of signaling pathways controls motility, directional sensing, and polarity

Chemotaxis, the directed migration of cells in chemical gradients, is a vital process in normal physiology and in the pathogenesis of many diseases. Chemotactic cells display motility, directional sensing, and polarity. Motility refers to the random extension of pseudopodia, which may be driven by spontaneous actin waves that propagate through the cytoskeleton. Directional sensing is mediated by a system that detects temporal and spatial stimuli and biases motility toward the gradient. Polarity gives cells morphologically and functionally distinct leading and lagging edges by relocating proteins or their activities selectively to the poles. By exploiting the genetic advantages of Dictyostelium, investigators are working out the complex network of interactions between the proteins that have been implicated in the chemotactic processes of motility, directional sensing, and polarity.

Migration Stimulating Factor (MSF) promotes fibroblast migration by inhibiting AKT

The protein kinase AKT is activated strongly by many motogenic growth factors, yet has recently been shown capable of inhibiting migration in several cell types. Here we report that treatment with Migration Stimulating Factor (MSF), a truncated form of fibronectin that promotes the migration of many cell types, inhibits AKT activity in human fibroblasts and endothelial cells. In fibroblasts, treatment with either MSF or the AKT inhibitor, Akti-1/2, stimulated migration into 3D collagen gels to a similar extent and the effects of Akti-1/2 on migration could be blocked by the expression of an inhibitor-resistant mutant, AKT1 W80A. These data indicate that MSF promotes fibroblast migration, at least in part, by inhibiting the activity of AKT.

Nuclear factor kappaB-activated monocytes contribute to pancreatic cancer progression through the production of Shh

Recently, it was reported that Hh signaling is activated in tumor stromal cells but not in tumor cells themselves and that stromal cells may play a role in the proliferation of cancer cells. This suggests the possibility that stromal cells have an important role in the proliferation of tumor cells that may be mediated through Hh signaling. In this report, we present for the first time that inflammation-stimulated monocytes produce Shh through activation of the NF-kappaB signaling pathway, and that the Shh produced promotes the proliferation of pancreatic cancer cells in a paracrine manner through Hh signaling.

Glucocorticoids and thiazolidinediones interfere with adipocyte-mediated macrophage chemotaxis and recruitment

The link between intra-abdominal adiposity and type II diabetes has been known for decades, and adipose tissue macrophage (ATM)-associated inflammation has recently been linked to insulin resistance. However, the mechanisms associated with ATM recruitment remain ill defined. Herein, we describe in vitro chemotaxis studies, in which adipocyte conditioned medium was used to stimulate macrophage migration. We demonstrate that tumor necrosis factor alpha and free fatty acids, key inflammatory stimuli involved in obesity-associated autocrine/paracrine inflammatory signaling, stimulate adipocyte expression and secretion of macrophage chemoattractants. Pharmacological studies showed that peroxisome proliferator-activated receptor gamma agonists and glucocorticoids potently inhibit adipocyte- induced recruitment of macrophages. This latter effect was mediated by the glucocorticoid receptor, which led to decreased chemokine secretion and expression. In vivo results were quite comparable; treatment of high fat diet-fed mice with dexamethasone prevented ATM accumulation in epididymal fat. This decrease in ATM was most pronounced for the proinflammatory F4/80(+), CD11b(+), CD11c(+) M-1-like ATM subset. Overall, our results elucidate a beneficial function of peroxisome proliferator-activated receptor gamma activation and glucocorticoid receptor/glucocorticoids in adipose tissue and indicate that pharmacologic prevention of ATM accumulation could be beneficial.