Protein kinase C alpha-CARMA3 signaling axis links Ras to NF-kappa B for lysophosphatidic acid-induced urokinase plasminogen activator expression in ovarian cancer cells

BCL10 correlates with bad prognosis and immune infiltration of tumor microenvironment in hepatocellular carcinoma

It has been reported that B-cell CLL-lymphoma 10 (BCL10) serves as an oncogene in cervical cancer. However, the roles of BCL10 in hepatocellular carcinoma (HCC), especially involved in immune infiltration remain not clear. This study aims to explore the relationship between BCL10 and the prognosis and clinical significance, and immune infiltration in HCC. The expression of BCL10 was analyzed between HCC samples and non-tumor samples in the multiple datasets. In addition, the prognostic values of BCL10 and its methylation in HCC were also investigated. The clinical significance of BCL10 has also been explored. Furthermore, the correlation between BCL10 and immune infiltration in HCC microenvironment was assessed. Finally, the biological behaviors of BCL10 in HCC were verified by cell function experiments. It was found that the expression levels of BCL10 were increased in HCC patients in multiple datasets. Moreover, the increased BCL10 and its reduced methylation were associated with the poor survival. BCL10 was significantly associated with immune infiltration. When BCL10 was knocked down in HCC cells, their proliferation ability was significantly inhibited, their migration was significantly decreased, their apoptosis was significantly increased, and AKT signaling pathway was inhibited. In conclusion, BCL10 is a potential prognostic and diagnostic biomarker related to immune infiltration in HCC microenvironment.

Protein Kinase C (PKC) Isozymes as Diagnostic and Prognostic Biomarkers and Therapeutic Targets for Cancer

Protein kinase C (PKC) is a large family of calcium- and phospholipid-dependent serine/threonine kinases that consists of at least 11 isozymes. Based on their structural characteristics and mode of activation, the PKC family is classified into three subfamilies: conventional or classic (cPKCs; α, βI, βII, and γ), novel or non-classic (nPKCs; δ, ε, η, and θ), and atypical (aPKCs; ζ, ι, and λ) (PKCλ is the mouse homolog of PKCι) PKC isozymes. PKC isozymes play important roles in proliferation, differentiation, survival, migration, invasion, apoptosis, and anticancer drug resistance in cancer cells. Several studies have shown a positive relationship between PKC isozymes and poor disease-free survival, poor survival following anticancer drug treatment, and increased recurrence. Furthermore, a higher level of PKC activation has been reported in cancer tissues compared to that in normal tissues. These data suggest that PKC isozymes represent potential diagnostic and prognostic biomarkers and therapeutic targets for cancer. This review summarizes the current knowledge and discusses the potential of PKC isozymes as biomarkers in the diagnosis, prognosis, and treatment of cancers.

Combining precision oncology and immunotherapy by targeting the MALT1 protease

An innovative strategy for cancer therapy is to combine the inhibition of cancer cell-intrinsic oncogenic signaling with cancer cell-extrinsic immunological activation of the tumor microenvironment (TME). In general, such approaches will focus on two or more distinct molecular targets in the malignant cells and in cells of the surrounding TME. In contrast, the protease Mucosa-associated lymphoid tissue protein 1 (MALT1) represents a candidate to enable such a dual approach by engaging only a single target. Originally identified and now in clinical trials as a lymphoma drug target based on its role in the survival and proliferation of malignant lymphomas addicted to chronic B cell receptor signaling, MALT1 proteolytic activity has recently gained additional attention through reports describing its tumor-promoting roles in several types of non-hematological solid cancer, such as breast cancer and glioblastoma. Besides cancer cells, regulatory T (Treg) cells in the TME are particularly dependent on MALT1 to sustain their immune-suppressive functions, and MALT1 inhibition can selectively reprogram tumor-infiltrating Treg cells into Foxp3-expressing proinflammatory antitumor effector cells. Thereby, MALT1 inhibition induces local inflammation in the TME and synergizes with anti-PD-1 checkpoint blockade to induce antitumor immunity and facilitate tumor control or rejection. This new concept of boosting tumor immunotherapy in solid cancer by MALT1 precision targeting in the TME has now entered clinical evaluation. The dual effects of MALT1 inhibitors on cancer cells and immune cells therefore offer a unique opportunity for combining precision oncology and immunotherapy to simultaneously impair cancer cell growth and neutralize immunosuppression in the TME. Further, MALT1 targeting may provide a proof of concept that modulation of Treg cell function in the TME represents a feasible strategy to augment the efficacy of cancer immunotherapy. Here, we review the role of MALT1 protease in physiological and oncogenic signaling, summarize the landscape of tumor indications for which MALT1 is emerging as a therapeutic target, and consider strategies to increase the chances for safe and successful use of MALT1 inhibitors in cancer therapy.

The Gab2-MALT1 axis regulates thromboinflammation and deep vein thrombosis

Deep vein thrombosis (DVT) is the third most common cause of cardiovascular mortality. Several studies suggest that DVT occurs at the intersection of dysregulated inflammation and coagulation upon activation of inflammasome and secretion of interleukin 1β (IL-1β) in restricted venous flow conditions. Our recent studies showed a signaling adapter protein, Gab2 (Grb2-associated binder 2), plays a crucial role in propagating inflammatory signaling triggered by IL-1β and other inflammatory mediators in endothelial cells. The present study shows that Gab2 facilitates the assembly of the CBM (CARMA3 [CARD recruited membrane-associated guanylate kinase protein 3]-BCL-10 [B-cell lymphoma 10]-MALT1 [mucosa-associated lymphoid tissue lymphoma translocation protein 1]) signalosome, which mediates the activation of Rho and NF-κB in endothelial cells. Gene silencing of Gab2 or MALT1, the effector signaling molecule in the CBM signalosome, or pharmacological inhibition of MALT1 with a specific inhibitor, mepazine, significantly reduced IL-1β-induced Rho-dependent exocytosis of P-selectin and von Willebrand factor (VWF) and the subsequent adhesion of neutrophils to endothelial cells. MALT1 inhibition also reduced IL-1β-induced NF-κB-dependent expression of tissue factor and vascular cell adhesion molecule 1. Consistent with the in vitro data, Gab2 deficiency or pharmacological inhibition of MALT1 suppressed the accumulation of monocytes and neutrophils at the injury site and attenuated venous thrombosis induced by the inferior vena cava ligation-induced stenosis or stasis in mice. Overall, our data reveal a previously unrecognized role of the Gab2-MALT1 axis in thromboinflammation. Targeting the Gab2-MALT1 axis with MALT1 inhibitors may become an effective strategy to treat DVT by suppressing thromboinflammation without inducing bleeding complications.

CARD14 Signalling Ensures Cell Survival and Cancer Associated Gene Expression in Prostate Cancer Cells

Prostate cancer (PCa) is one of the most common cancer types in men and represents an increasing global problem due to the modern Western lifestyle. The signalling adapter protein CARD14 is specifically expressed in epithelial cells, where it has been shown to mediate NF-κB signalling, but a role for CARD14 in carcinoma has not yet been described. By analysing existing cancer databases, we found that CARD14 overexpression strongly correlates with aggressive PCa in human patients. Moreover, we showed that CARD14 is overexpressed in the LNCaP PCa cell line and that knockdown of CARD14 severely reduces LNCaP cell survival. Similarly, knockdown of BCL10 and MALT1, which are known to form a signalling complex with CARD14, also induced LNCaP cell death. MALT1 is a paracaspase that mediates downstream signalling by acting as a scaffold, as well as a protease. Recent studies have already indicated a role for the scaffold function of MALT1 in PCa cell growth. Here, we also demonstrated constitutive MALT1 proteolytic activity in several PCa cell lines, leading to cleavage of A20 and CYLD. Inhibition of MALT1 protease activity did not affect PCa cell survival nor activation of NF-κB and JNK signalling, but reduced expression of cancer-associated genes, including the cytokine IL-6. Taken together, our results revealed a novel role for CARD14-induced signalling in regulating PCa cell survival and gene expression. The epithelial cell type-specific expression of CARD14 may offer novel opportunities for more specific therapeutic targeting approaches in PCa.

MALT1 is a Targetable Driver of Epithelial-to-Mesenchymal Transition in Claudin-low, Triple-Negative Breast Cancer

MALT1 is the effector protein of the CARMA/Bcl10/MALT1 (CBM) signalosome, a multi-protein complex that drives pro-inflammatory signaling pathways downstream of a diverse set of receptors. While CBM activity is best known for its role in immune cells, emerging evidence suggests that it plays a key role in the pathogenesis of solid tumors, where it can be activated by selected G protein-coupled receptors (GPCRs). Here, we demonstrated that overexpression of GPCRs implicated in breast cancer pathogenesis, specifically the receptors for Angiotensin II and thrombin (AT1R and PAR1), drove a strong epithelial-to-mesenchymal transition (EMT) program in breast cancer cells that is characteristic of claudin-low, triple-negative breast cancer (TNBC). In concert, MALT1 was activated in these cells and contributed to the dramatic EMT phenotypic changes through regulation of master EMT transcription factors including Snail and ZEB1. Importantly, blocking MALT1 signaling, through either siRNA-mediated depletion of MALT1 protein or pharmacologic inhibition of its activity, was effective at partially reversing the molecular and phenotypic indicators of EMT. Treatment of mice with mepazine, a pharmacologic MALT1 inhibitor, reduced growth of PAR1+, MDA-MB-231 xenografts and had an even more dramatic effect in reducing the burden of metastatic disease. These findings highlight MALT1 as an attractive therapeutic target for claudin-low TNBCs harboring overexpression of one or more selected GPCRs. Implications: This study nominates a GPCR/MALT1 signaling axis as a pathway that can be pharmaceutically targeted to abrogate EMT and metastatic progression in TNBC, an aggressive form of breast cancer that currently lacks targeted therapies.

CARD10 cleavage by MALT1 restricts lung carcinoma growth in vivo

CARD-CC complexes involving BCL10 and MALT1 are major cellular signaling hubs. They govern NF-κB activation through their scaffolding properties as well as MALT1 paracaspase function, which cleaves substrates involved in NF-κB regulation. In human lymphocytes, gain-of-function defects in this pathway lead to lymphoproliferative disorders. CARD10, the prototypical CARD-CC protein in non-hematopoietic cells, is overexpressed in several cancers and has been associated with poor prognosis. However, regulation of CARD10 remains poorly understood. Here, we identified CARD10 as the first MALT1 substrate in non-hematopoietic cells and showed that CARD10 cleavage by MALT1 at R587 dampens its capacity to activate NF-κB. Preventing CARD10 cleavage in the lung tumor A549 cell line increased basal levels of IL-6 and extracellular matrix components in vitro, and led to increased tumor growth in a mouse xenograft model, suggesting that CARD10 cleavage by MALT1 might be a built-in mechanism controlling tumorigenicity.

The Role of Calcium Signaling in Regulation of Epithelial-Mesenchymal Transition

Despite substantial advances in the field of cancer therapeutics, metastasis is a significant challenge for a favorable clinical outcome. Epithelial to mesenchymal transition (EMT) is a process of acquiring increased motility, invasiveness, and therapeutic resistance by cancer cells for their sustained growth and survival. A plethora of intrinsic mechanisms and extrinsic microenvironmental factors drive the process of cancer metastasis. Calcium (Ca2+) signaling plays a critical role in dictating the adaptive metastatic cell behavior comprising of cell migration, invasion, angiogenesis, and intravasation. By modulating EMT, Ca2+ signaling can regulate the complexity and dynamics of events leading to metastasis. This review summarizes the role of Ca2+ signal remodeling in the regulation of EMT and metastasis in cancer.

CARD10 promotes the progression of renal cell carcinoma by regulating the NF‑κB signaling pathway

Previous studies have demonstrated that the expression of CARD10 is closely associated with the occurrence of tumors, and its role is mainly to promote tumor progression by activating the transcription factor NF-κB. However, the signaling pathway in renal cancer remains unclear. The objective of the present study was to investigate the ability of caspase recruitment domain 10 (CARD10) to regulate the NF-κB signaling pathway and promote the progression of renal cell carcinoma (RCC). Expression of CARD10 in ACHN, 786-O and HK-2 cells was evaluated via western blot analysis, as was the epidermal growth factor (EGF)-induced activation of NF-κB signaling pathway-related proteins in cells. The expression of CARD10 was inhibited by CARD10 short hairpin RNA transfection. Cell cycle analysis and MTT assays were used to evaluate cell proliferation. Cell apoptosis was analyzed via flow cytometry. The invasion of renal cell lines was detected via Transwell cell migration and invasion assays in vitro. The results showed that CARD10 expression was significantly higher in RCC cells than in normal renal tubular epithelial cells. CARD10 silencing inhibited the proliferation, invasion and migration of RCC cells. EGF stimulation upregulated the activation of the NF-κB pathway in RCC cells. Inhibition of CARD10 expression inhibited NF-κB activation in RCC cells. Taken together, these data suggested that CARD10 promotes the progression of renal cell carcinoma by regulating the NF-κB signaling pathway. Thus, this indicated that CARD10 may be a novel therapeutic target in RCC.

MALT1 is a critical mediator of PAR1-driven NF-κB activation and metastasis in multiple tumor types

Protease-activated receptor 1 (PAR1), a thrombin-responsive G protein-coupled receptor (GPCR), is implicated in promoting metastasis in multiple tumor types, including both sarcomas and carcinomas, but the molecular mechanisms responsible remain largely unknown. We previously discovered that PAR1 stimulation in endothelial cells leads to activation of NF-κB, mediated by a protein complex comprised of CARMA3, Bcl10, and the MALT1 effector protein (CBM complex). Given the strong association between NF-κB and metastasis, we hypothesized that this CBM complex could play a critical role in the PAR1-driven metastatic progression of specific solid tumors. In support of our hypothesis, we demonstrate that PAR1 stimulation results in NF-κB activation in both osteosarcoma and breast cancer, which is suppressed by siRNA-mediated MALT1 knockdown, suggesting that an intact CBM complex is required for the response in both tumor cell types. We identify several metastasis-associated genes that are upregulated in a MALT1-dependent manner after PAR1 stimulation in cancer cells, including those encoding the matrix remodeling protein, MMP9, and the cytokines, IL-1β and IL-8. Further, exogenous expression of PAR1 in MCF7 breast cancer cells confers highly invasive and metastatic behavior which can be blocked by CRISPR/Cas9-mediated MALT1 knockout. Importantly, we find that PAR1 stimulation induces MALT1 protease activity in both osteosarcoma and breast cancer cells, an activity that is mechanistically linked to NF-κB activation and potentially other responses associated with aggressive phenotype. Several small molecule MALT1 protease inhibitors have recently been described that could therefore represent promising new therapeutics for the prevention and/or treatment of PAR1-driven tumor metastasis.

Lysophosphatidic acid induces interleukin-6 and CXCL15 secretion from MLO-Y4 cells through activation of the LPA1 receptor and PKCθ signaling pathway

Lysophosphatidic acid (LPA) is a multifunctional phospholipid. Osteocytes are the most abundant cells in bone and can orchestrate bone formation and resorption, in part by producing cytokines that regulate osteoblast and osteoclast differentiation and activity. Interleukin (IL)-6 and IL-8 are two important cytokines that have potent effects on bone fracture healing. Previous studies suggest that platelet-derived LPA may influence fracture healing by inducing osteocyte dendrite outgrowth. However, the biological mechanism through which LPA induces cytokine production in osteocytes is poorly understood. In this study, we report that LPA markedly enhanced IL-6 and CXCL15 (mouse homologue of human IL-8) production in MLO-Y4 cells and that this enhancement was suppressed by the LPA_1/3-selective antagonist Ki16425, the G_i/o protein inhibitor PTX or the protein kinase C (PKC) inhibitor sotrastaurin. We also observed that of all the PKC isoform targets of sotrastaurin, only PKCθ was activated by LPA in MLO-Y4 cells and that this activation was blocked by sotrastaurin, Ki16425 or PTX. Taken together, the results of the present study demonstrate that LPA may be a potent inducer of IL-6 and CXCL15 production in MLO-Y4 cells and that this induction is associated with the activation of LPA₁, G_i/o protein and the PKCθ pathway. These findings may help us better understand the mechanism of fracture healing and contribute to the treatment of bone damage.

Role of autotaxin in cancer stem cells

Stem cells are a rare subpopulation defined by the potential to self-renew and differentiate into specific cell types. A population of stem-like cells has been reported to possess the ability of self-renewal, invasion, metastasis, and engraftment of distant tissues. This unique cell subpopulation has been designated as cancer stem cells (CSC). CSC were first identified in leukemia, and the contributions of CSC to cancer progression have been reported in many different types of cancers. The cancer stem cell hypothesis attempts to explain tumor cell heterogeneity based on the existence of stem cell-like cells within solid tumors. The elimination of CSC is challenging for most human cancer types due to their heightened genetic instability and increased drug resistance. To combat these inherent abilities of CSC, multi-pronged strategies aimed at multiple aspects of CSC biology are increasingly being recognized as essential for a cure. One of the most challenging aspects of cancer biology is overcoming the chemotherapeutic resistance in CSC. Here, we provide an overview of autotaxin (ATX), lysophosphatidic acid (LPA), and their signaling pathways in CSC. Increasing evidence supports the role of ATX and LPA in cancer progression, metastasis, and therapeutic resistance. Several studies have demonstrated the ATX-LPA axis signaling in different cancers. This lipid mediator regulatory system is a novel potential therapeutic target in CSC. In this review, we summarize the evidence linking ATX-LPA signaling to CSC and its impact on cancer progression and metastasis. We also provide evidence for the efficacy of cancer therapy involving the pharmacological inhibition of this signaling pathway.

BCL10 in cell survival after DNA damage

The complex defense mechanism of the DNA damage response (DDR) developed by cells during long-term evolution is an important mechanism for maintaining the stability of the genome. Defects in the DDR pathway can lead to the occurrence of various diseases, including tumor development. Most cancer treatments cause DNA damage and apoptosis. However, cancer cells have the natural ability to repair this damage and inhibit apoptosis, ultimately leading to the development of drug resistance. Therefore, investigating the mechanism of DNA damage may contribute markedly to the future treatment of cancer. The CARMA-BCL10-MALT1 (CBM) complex formed by B cell lymphoma/leukemia 10 (BCL10) regulates apoptosis by activating NF-κB signaling. BCL10 is involved in the formation of complexes that antagonize apoptosis and contribute to cell survival after DNA damage, with cytoplasmic BCL10 entering the nucleus to promote DNA damage repair, including histone ubiquitination and the recruitment of homologous recombination (HR) repair factors. This article reviews the role of BCL10 in cell survival following DNA damage.

Differential Regulation of Gene Expression in Lung Cancer Cells by Diacyglycerol-Lactones and a Phorbol Ester Via Selective Activation of Protein Kinase C Isozymes

Despite our extensive knowledge on the biology of protein kinase C (PKC) and its involvement in disease, limited success has been attained in the generation of PKC isozyme-specific modulators acting via the C1 domain, the binding site for the lipid second messenger diacylglycerol (DAG) and the phorbol ester tumor promoters. Synthetic efforts had recently led to the identification of AJH-836, a DAG-lactone with preferential affinity for novel isozymes (nPKCs) relative to classical PKCs (cPKCs). Here, we compared the ability of AJH-836 and a prototypical phorbol ester (phorbol 12-myristate 13-acetate, PMA) to induce changes in gene expression in a lung cancer model. Gene profiling analysis using RNA-Seq revealed that PMA caused major changes in gene expression, whereas AJH-836 only induced a small subset of genes, thus providing a strong indication for a major involvement of cPKCs in their control of gene expression. MMP1, MMP9, and MMP10 were among the genes most prominently induced by PMA, an effect impaired by RNAi silencing of PKCα, but not PKCδ or PKCε. Comprehensive gene signature analysis and bioinformatics efforts, including functional enrichment and transcription factor binding site analyses of dysregulated genes, identified major differences in pathway activation and transcriptional networks between PMA and DAG-lactones. In addition to providing solid evidence for the differential involvement of individual PKC isozymes in the control of gene expression, our studies emphasize the importance of generating targeted C1 domain ligands capable of differentially regulating PKC isozyme-specific function in cellular models.

CARMA3: Scaffold Protein Involved in NF-κB Signaling

Scaffold proteins are defined as pivotal molecules that connect upstream receptors to specific effector molecules. Caspase recruitment domain protein 10 (CARD10) gene encodes a scaffold protein CARMA3, belongs to the family of CARD and membrane-associated guanylate kinase-like protein (CARMA). During the past decade, investigating the function of CARMA3 has revealed that it forms a complex with BCL10 and MALT1 to mediate different receptors-dependent signaling, including GPCR and EGFR, leading to activation of the transcription factor NF-κB. More recently, CARMA3 and its partners are also reported to be involved in antiviral innate immune response and DNA damage response. In this review, we summarize the biology of CARMA3 in multiple receptor-induced NF-κB signaling. Especially, we focus on discussing the function of CARMA3 in regulating NF-κB activation and antiviral IFN signaling in the context of recent progress in the field.

CARMA3 Is a Critical Mediator of G Protein-Coupled Receptor and Receptor Tyrosine Kinase-Driven Solid Tumor Pathogenesis

The CARMA–Bcl10–MALT1 (CBM) signalosome is an intracellular protein complex composed of a CARMA scaffolding protein, the Bcl10 linker protein, and the MALT1 protease. This complex was first recognized because the genes encoding its components are targeted by mutation and chromosomal translocation in lymphoid malignancy. We now know that the CBM signalosome plays a critical role in normal lymphocyte function by mediating antigen receptor-dependent activation of the pro-inflammatory, pro-survival NF-κB transcription factor, and that deregulation of this signaling complex promotes B-cell lymphomagenesis. More recently, we and others have demonstrated that a CBM signalosome also operates in cells outside of the immune system, including in several solid tumors. While CARMA1 (also referred to as CARD11) is expressed primarily within lymphoid tissues, the related scaffolding protein, CARMA3 (CARD10), is more widely expressed and participates in a CARMA3-containing CBM complex in a variety of cell types. The CARMA3-containing CBM complex operates downstream of specific G protein-coupled receptors (GPCRs) and/or growth factor receptor tyrosine kinases (RTKs). Since inappropriate expression and activation of GPCRs and/or RTKs underlies the pathogenesis of several solid tumors, there is now great interest in elucidating the contribution of CARMA3-mediated cellular signaling in these malignancies. Here, we summarize the key discoveries leading to our current understanding of the role of CARMA3 in solid tumor biology and highlight the current gaps in our knowledge.

The critical role and potential target of the autotaxin/lysophosphatidate axis in pancreatic cancer

Autotaxin, an ecto-lysophospholipase D encoded by the human ENNP2 gene, is expressed in multiple tissues, and participates in numerous critical physiologic and pathologic processes including inflammation, pain, obesity, embryo development, and cancer via the generation of the bioactive lipid lysophosphatidate. Overwhelming evidences indicate that the autotaxin/lysophosphatidate signaling axis serves key roles in the numerous processes central to tumorigenesis and progression, including proliferation, survival, migration, invasion, metastasis, cancer stem cell, tumor microenvironment, and treatment resistance by interacting with a series of at least six G-protein-coupled receptors (LPAR1-6). This review provides an overview of the autotaxin/lysophosphatidate axis and collates current knowledge regarding its specific role in pancreatic cancer. With a deeper understanding of the critical role of the autotaxin/lysophosphatidate axis in pancreatic cancer, targeting autotaxin or lysophosphatidate receptor may be a potential and promising strategy for cancer therapy.

5-(Bis(3-(2-hydroxyethyl)-1H-indol-2-yl)methyl)-2-hydroxybenzoic acid (BHIMHA): showing a strategy of designing drug to block lung metastasis of tumors

Early metastasis is still the most recalcitrant factor in the treatment of lung cancer patients. By analyzing the structures and comparing the docking scores of the known pharmacophores, the authors of this paper designed 5-(bis(3-(2-hydroxyethyl)-1H-indol-2-yl)methyl)-2-hydroxybenzoic acid (BHIMHA) as a promising lead compound to develop metastasis inhibitors. In vitro 5, 10, and 20 µM of BHIMHA concentration dependently inhibited the migration and invasion of A549 cells. In vivo 0.4, 2.0, and 8.9 µmol/kg of BHIMHA dose dependently inhibited the metastasis of LLC (Lewis Lung Carcinoma) toward lung. In vivo, 2 µmol/kg of BHIMHA showed additional actions of slowing the growth of the primary tumor of C57BL/6 mice and S180 mice as well as inhibiting xylene-induced ear edema of the mice. Therefore, BHIMHA simultaneously blocked tumor metastasis toward lung, slowed the primary tumor growth, and limited the inflammation. These pharmacological actions were correlated with the inhibition of PKCα and NF-κB expression.

The paracaspase MALT1: biological function and potential for therapeutic inhibition

The paracaspase MALT1 has a central role in the activation of lymphocytes and other immune cells including myeloid cells, mast cells and NK cells. MALT1 activity is required not only for the immune response, but also for the development of natural Treg cells that keep the immune response in check. Exaggerated MALT1 activity has been associated with the development of lymphoid malignancies, and recently developed MALT1 inhibitors show promising anti-tumor effects in xenograft models of diffuse large B cell lymphoma. In this review, we provide an overview of the present understanding of MALT1's function, and discuss possibilities for its therapeutic targeting based on recently developed inhibitors and animal models.

Targeting MALT1 Proteolytic Activity in Immunity, Inflammation and Disease: Good or Bad?

MALT1 is a signaling protein that plays a key role in immunity, inflammation, and lymphoid malignancies. For a long time MALT1 was believed to function as a scaffold protein, providing an assembly platform for other signaling proteins. This view changed dramatically when MALT1 was also found to have proteolytic activity and a capacity to fine-tune immune responses. Preclinical studies have fostered the belief that MALT1 is a promising therapeutic target in autoimmunity and B cell lymphomas. However, recent studies have shown that mice expressing catalytically-inactive MALT1 develop multi-organ inflammation and autoimmunity, and thus have tempered this initial enthusiasm. We discuss recent findings, highlighting the urgent need for a better mechanistic and functional understanding of MALT1 in host defense and disease.

CARMA3 regulates the invasion, migration, and apoptosis of non-small cell lung cancer cells by activating NF-кB and suppressing the P38 MAPK signaling pathway

In our previous study, CARMA3 overexpression in lung cancer cells promoted cell proliferation and invasion; however, the mechanism underlying the role of CARMA3 in cancer cell invasion remained unclear. In the present study, knockdown of CARMA3 in A549 and H1299 cells suppressed cell invasion and migration, and downregulated matrix metalloprotease 9 expression at the protein and mRNA levels, as shown by Western blotting and real-time PCR. CARMA3 knockdown increased cell apoptosis, as shown by flow cytometry, increased the mRNA and protein expression levels of Bax and Caspase3, and downregulated Bcl-2 in A549 and H1299 cells. Phosphorylated P38 levels increased and NF-кB activation decreased following knockdown of CARMA3. SB203580, a P38 MAPK inhibitor, activated NF-кB, increased cell migration, and inhibited cell apoptosis after knockdown of CARMA3 compared to knockdown of CARMA3 without SB203580. These findings indicate that CARMA3 may suppress the activation of the P38 MAPK signaling pathway to regulate invasion, migration and apoptosis of lung cancer cells by activating NF-кB (P65) in the nucleus.

Lysophosphatidic acid signaling in ovarian cancer

Lysophosphatidic acid (LPA) is a bioactive phospholipid that is involved in signal transduction between cells. Plasma and ascites levels of LPA are increased in ovarian cancer patients even in the early stages and thus LPA is considered as a potential diagnostic marker for this disease. This review presents the current knowledge regarding LPA signaling in epithelial ovarian cancer. LPA stimulates proliferation, migration and invasion of ovarian cancer cells through regulation of vascular endothelial growth factor, matrix metalloproteinases, urokinase plasminogen activator, interleukin-6, interleukin-8, CXC motif chemokine ligand 12/CXC receptor 4, COX2, cyclin D1, Hippo-Yap and growth-regulated oncogene α concentrations. In this article, all of these targets and signal pathways involved in LPA influence are described.

Analysis of epidermal growth factor-induced NF-κB signaling

The nuclear factor kappaB (NF-κB) is a family of transcription factors that control cell survival, cell proliferation, cell differentiation, inflammatory responses, and innate and adaptive immune responses. Its activation is tightly regulated, and incorrect regulation of NF-κB has been linked to a variety of pathological diseases, including cancer initiation and progression. NF-κB is often constitutively activated in cancer cells to promote cell survival, proliferation, migration, and/or epithelial-to-mesenchymal transition (EMT). Although the mechanism of constitutive NF-κB activation in cancer cells is not fully understood, it has been shown that mutation or aberrant expression of epidermal growth factor receptor (EGFR) contributes to this, and the NF-κB activation, in turn, contributes to cell proliferation, survival, metastasis, and drug resistance in various cancers. Recent study from our lab indicates that CARMA3, similar to the function of CARMA1 in mediating antigen receptor-mediated NF-κB activation, plays an essential role in mediating EGFR-induced NF-κB activation. However, the mechanism on how EGFR induces NF-κB activation is not clearly understood. In this chapter, we describe the methods required to test and characterize the role of a potential signaling component in EGFR-induced NF-κB activation.

Protein kinase C and cancer: what we know and what we do not

Since their discovery in the late 1970s, protein kinase C (PKC) isozymes represent one of the most extensively studied signaling kinases. PKCs signal through multiple pathways and control the expression of genes relevant for cell cycle progression, tumorigenesis and metastatic dissemination. Despite the vast amount of information concerning the mechanisms that control PKC activation and function in cellular models, the relevance of individual PKC isozymes in the progression of human cancer is still a matter of controversy. Although the expression of PKC isozymes is altered in multiple cancer types, the causal relationship between such changes and the initiation and progression of the disease remains poorly defined. Animal models developed in the last years helped to better understand the involvement of individual PKCs in various cancer types and in the context of specific oncogenic alterations. Unraveling the enormous complexity in the mechanisms by which PKC isozymes have an impact on tumorigenesis and metastasis is key for reassessing their potential as pharmacological targets for cancer treatment.

MicroRNA-146a alleviates chronic skin inflammation in atopic dermatitis through suppression of innate immune responses in keratinocytes

BACKGROUND

Chronic skin inflammation in atopic dermatitis (AD) is associated with elevated expression of proinflammatory genes and activation of innate immune responses in keratinocytes. microRNAs (miRNAs) are short, single-stranded RNA molecules that silence genes via the degradation of target mRNAs or inhibition of translation.

OBJECTIVE

The aim of this study was to investigate the role of miR-146a in skin inflammation in AD.

METHODS

RNA and protein expression was analyzed using miRNA and mRNA arrays, RT-quantitative PCR, Western blotting, and immunonohistochemistry. Transfection of miR-146a precursors and inhibitors into human primary keratinocytes, luciferase assays, and MC903-dependent mouse model of AD were used to study miR-146a function.

RESULTS

We show that miR-146a expression is increased in keratinocytes and chronic lesional skin of patients with AD. miR-146a inhibited the expression of numerous proinflammatory factors, including IFN-γ-inducible and AD-associated genes CCL5, CCL8, and ubiquitin D (UBD) in human primary keratinocytes stimulated with IFN-γ, TNF-α, or IL-1β. In a mouse model of AD, miR-146a-deficient mice developed stronger inflammation characterized by increased accumulation of infiltrating cells in the dermis, elevated expression of IFN-γ, CCL5, CCL8, and UBD in the skin, and IFN-γ, IL-1β, and UBD in draining lymph nodes. Both tissue culture and in vivo experiments in mice demonstrated that miR-146a-mediated suppression in allergic skin inflammation partially occurs through direct targeting of upstream nuclear factor kappa B signal transducers caspase recruitment domain-containing protein 10 and IL-1 receptor-associated kinase 1. In addition, human CCL5 was determined as a novel, direct target of miR-146a.

CONCLUSION

Our data demonstrate that miR-146a controls nuclear factor kappa B-dependent inflammatory responses in keratinocytes and chronic skin inflammation in AD.

CARMA3 is upregulated in human pancreatic carcinoma, and its depletion inhibits tumor proliferation, migration, and invasion

Elevated CARMA3 expression has been reported to be involved in tumor progression of several cancer types. In the present study, we examined the expression pattern of CARMA3 protein and its biological roles in human pancreatic carcinoma. Using immunohistochemistry, we checked CARMA3 protein expression in 95 pancreatic ductal carcinoma specimens. We found that CARMA3 was overexpressed in 34 of 95 (35.8 %) specimens. A significant association was observed between CARMA3 overexpression with histological grade (p=0.0099) and nodal status (p=0.0126). To further explore its biological roles, we knocked down CARMA3 expression in CAPAN2 cell line using small interfering RNA (siRNA). MTT growth assay, wound healing assay, and Transwell assay showed that CARMA3 depletion inhibited cell proliferation, migration, and invasion. We also showed that CARMA3 depletion inhibited EGF-induced nuclear factor-kappaB (NF-κB) activation and its target genes' expression. The effect of CARMA3 depletion on NF-κB signaling was significantly reduced in Bcl10-depleted cells. In conclusion, CARMA3 is overexpressed in pancreatic cancer and regulates malignant cell growth, invasion, and NF-κB signaling, which was dependent on its association with Bcl10.

Overexpression of CARMA3 is associated with advanced tumor stage, cell cycle progression, and cisplatin resistance in human epithelial ovarian cancer

CARD recruited membrane associated protein 3 (CARMA3) overexpression has been found in several human cancers. However, its expression pattern and biological roles in human ovarian cancers are not clear. In this study, we examined the expression pattern of CARMA3 in 101 ovarian cancer specimens. We found that 52 (51.5 %) showed CARMA3 overexpression. CARMA3 overexpression positively correlated with tumor histology and advanced FIGO stage. CARMA3 depletion in ovarian cancer cell lines A2780 and HO8910 inhibited ovarian cancer cell proliferation and blocked cell cycle progression. CARMA3 depletion also sensitized ovarian cancer cells to cisplatin-induced cytotoxicity. In addition, Western blot showed that CARMA3 depletion downregulated cyclin D1, cyclin E, and Bcl-2 levels. In conclusion, our data provides evidence that CARMA3 is overexpressed in ovarian cancers and associated with advanced stage. CARMA3 regulates the ovarian cancer cell proliferation, cell cycle progression, and chemoresistance.

Protein Kinase C (PKC) Isozymes and Cancer

Protein kinase C (PKC) is a family of phospholipid-dependent serine/threonine kinases, which can be further classified into three PKC isozymes subfamilies: conventional or classic, novel or nonclassic, and atypical. PKC isozymes are known to be involved in cell proliferation, survival, invasion, migration, apoptosis, angiogenesis, and drug resistance. Because of their key roles in cell signaling, PKC isozymes also have the potential to be promising therapeutic targets for several diseases, such as cardiovascular diseases, immune and inflammatory diseases, neurological diseases, metabolic disorders, and multiple types of cancer. This review primarily focuses on the activation, mechanism, and function of PKC isozymes during cancer development and progression.

Clinical significance and biological roles of CARMA3 in human bladder carcinoma

Caspase recruitment domain and membrane-associated guanylate kinase-like domain protein 3 (CARMA3) was reported as an oncoprotein overexpressed in several cancers. The expression pattern of CARMA3 and its clinical significance in human bladder cancer have not been well characterized. In the present study, CARMA3 expression was analyzed in 90 archived bladder cancer specimens using immunohistochemistry, and the correlation between CARMA3 expression and clinicopathological parameters was evaluated. We found that CARMA3 was overexpressed in 35 of 90 (38.8%) bladder cancer specimens. Significant association was observed between CARMA3 overexpression with tumor status (p = 0.081) and tumor grade (p = 0.027). To further explore the biological functions of CARMA3 in bladder cancer, we depleted CARMA3 in T24 and 5637 cell lines using small interfering RNA (siRNA). Using cell counting kit-8 (CCK8) assay and colony formation assay, we were able to show that CARMA3 depletion inhibited cell proliferation and colony number. Further study demonstrated that CARMA3 depletion decreased an expression of nuclear factor kappa B (NF-κB) targets cyclin D1 and Bcl-2 expression, as well as IκB phosphorylation. Luciferase reporter assay showed that CARMA3 depletion could downregulate NF-κB reporter activity. In conclusion, CARMA3 is overexpressed in bladder cancer and regulates malignant cell growth and NF-κB signaling, which makes CARMA3 a candidate therapeutic target for bladder cancer.

MyD88 and its divergent toll in carcinogenesis

Toll-like and interleukin-1 (IL-1) family receptors recognize microbial or endogenous ligands and inflammatory mediators, respectively, and with the exception of Toll-like receptor 3 (TLR3), signal via the adaptor molecule myeloid differentiation factor 88 (MyD88). MyD88 is involved in oncogene-induced cell intrinsic inflammation and in cancer-associated extrinsic inflammation, and as such MyD88 contributes to skin, liver, pancreatic, and colon carcinogenesis, as well as sarcomagenesis. MyD88 is also protective, for example in oncogenic virus carcinogenesis or, acting downstream of IL-18R to strengthen mucosal repair, in azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colon carcinogenesis. Here, we discuss the mechanisms of the divergent effects of MyD88 and the balance of its protumor role in cancer-enhancing inflammation and immunity and its antitumor role in tissue homeostasis, repair, and immunity against the tumor or oncogenic pathogens.

CARMA3 is overexpressed in human glioma and promotes cell invasion through MMP9 regulation in A172 cell line

Caspase recruitment domain-containing membrane-associated guanylate kinase protein 10 or CARMA3 (CARD10) is a recently characterized oncoprotein involved in the progression of several human malignancies. The present study aims to investigate the expression pattern and biological roles of CARMA3 protein in human glioma. CARMA3 expression was analyzed in 97 glioma specimens using immunohistochemistry. We observed negative staining in normal astrocytes and positive staining of CARMA3 in 25 out of 97 (25.8%) glioma samples. Overexpression of CARMA3 correlated with tumor grade (p < 0.001). Small interfering RNA knockdown was performed in A172 cell line with relatively high CARMA3 expression. Using colony formation assay and Matrigel invasion assay, we showed that CARMA3 depletion in A172 cell line inhibited cell proliferation and cell invasion. In addition, mRNA and protein levels of matrix metallopeptidase 9 (MMP9) were downregulated, indicating CARMA3 might regulate invasion through MMP9. In conclusion, CARMA3 serves as an oncoprotein in human glioma by regulating cell invasion, possibly through MMP9 regulation.

Evaluating the expression of CARMA3 as a prognostic tumor marker in renal cell carcinoma

Increased expression of CARMA3 has been reported to be involved in tumorigenesis and tumor progression of several cancer types. The aim of our study is to investigate the prognostic role of CARMA3 expression in patients with renal cell carcinoma (RCC). Real-time quantitative PCR was performed to detect CARMA3 mRNA expression level in 31 paired samples of RCC and adjacent noncancerous renal tissues. Subsequently, extensive immunohistochemistry was performed to detect CARMA3 protein expression in 114 RCC cases. Clinicopathological data for these patients were evaluated. The prognostic significance was assessed using the Kaplan-Meier survival estimates and log-rank tests. CARMA3 mRNA expression was significantly higher in RCC tissues compared with adjacent noncancerous renal tissues (3.525 ± 1.233 vs. 1.512 ± 0.784, P < 0.001). In addition, high CARMA3 expression in RCC tissues was significantly associated with tumor size (P = 0.026), histological differentiation (P = 0.039), tumor stage (P = 0.006), and the presence of metastasis (P < 0.001). Moreover, Kaplan-Meier analysis showed that patients with high CARMA3 expression also had a significantly poorer prognosis than those with low CARMA3 expression (log-rank test, P < 0.001). Furthermore, multivariate analysis illustrated that CARMA3 overexpression might be an independent prognostic indicator for the survival of patients with RCC. In conclusion, this work shows that CARMA3 may serve as a novel and prognostic marker for RCC and play a role during the development and progression of the disease.

Lysophosphatidic acid (LPA) signalling in cell migration and cancer invasion: a focussed review and analysis of LPA receptor gene expression on the basis of more than 1700 cancer microarrays

Lysophosphatidic acid (LPA) is a ubiquitously present signalling molecule involved in diverse cellular processes such as cell migration, proliferation and differentiation. LPA acts as an autocrine and/or paracrine signalling molecule via different G-protein-coupled LPA receptors (LPARs) that trigger a broad range of intracellular signalling cascades, especially the RHOA pathway. Mounting evidence suggests a crucial role of the LPA/LPAR-axis in cancer cell metastasis and promising studies are underway to investigate the therapeutic potential of LPAR-antagonists. This review summarises current knowledge on how LPA promotes cytoskeletal remodelling to enhance the migratory and invasive properties of cells, which may ultimately contribute to cancer metastasis. Furthermore, we provide comprehensive transcriptome analyses of published microarrays of more than 350 normal tissues and more than 1700 malignant tissues to define the expression signatures of LPARs and the LPA-generating enzymes autotaxin (ATX) and lipase member 1 (LIPI). These analyses demonstrate that ATX is highly expressed in a variety of carcinomas and sarcomas, whereas LIPI is almost exclusively overexpressed in highly aggressive Ewing's sarcomas, which underscores the potential contribution of LPA in metastatic disease. In addition, these analyses show that different cancer entities display distinct expression signatures of LPARs that distinguish them from one another. Finally, we discuss current approaches to specifically target the LPA/LPAR circuits in experimental cancer therapy.

CARMA3 overexpression accelerates cell proliferation and inhibits paclitaxel-induced apoptosis through NF-κB regulation in breast cancer cells

CARMA3 was recently reported to be overexpressed in several cancers and associated with malignant behavior of cancer cells. However, the expression pattern and biological roles of CARMA3 in breast cancer have not been reported. In the present study, we found that CARMA3 was overexpressed in 41.9 % of breast cancer specimens. Significant association was observed between CARMA3 overexpression and TNM stage (p = 0.0223), tumor size (p = 0.0227), and ErbB-2 status (p = 0.0049). Furthermore, knockdown of CARMA3 expression in MDA-MB-435 cells with high endogenous expression decreased cell proliferation and sensitized cell to paclitaxel-induced apoptosis, while overexpression of CARMA3 in MDA-MB-231 cell line promoted cell proliferation and inhibited apoptosis. Further analysis showed that CARMA3 depletion downregulated, and its overexpression upregulated cyclin D1, Bcl-2, and p-IκB levels. In conclusion, our study demonstrated that CARMA3 is overexpressed in breast cancers. CARMA3 facilitates proliferation and inhibits apoptosis through nuclear factor-kappaB signaling.

Ca2+/calmodulin-dependent kinase II contributes to inhibitor of nuclear factor-kappa B kinase complex activation in Helicobacter pylori infection

Helicobacter pylori, a class I carcinogen, induces a proinflammatory response by activating the transcription factor nuclear factor-kappa B (NF-κB) in gastric epithelial cells. This inflammatory condition could lead to chronic gastritis, which is epidemiologically and biologically linked to the development of gastric cancer. So far, there exists no clear knowledge on how H. pylori induces the NF-κB-mediated inflammatory response. In our study, we investigated the role of Ca(2+) /calmodulin-dependent kinase II (CAMKII), calmodulin, protein kinases C (PKCs) and the CARMA3-Bcl10-MALT1 (CBM) complex in conjunction with H. pylori-induced activation of NF-κB via the inhibitor of nuclear factor-kappa B kinase (IKK) complex. We use specific inhibitors and/or RNA interference to assess the contribution of these components. Our results show that CAMKII and calmodulin contribute to IKK complex activation and thus to the induction of NF-κB in response to H. pylori infection, but not in response to TNF-α. Thus, our findings are specific for H. pylori infected cells. Neither the PKCs α, δ, θ, nor the CBM complex itself is involved in the activation of NF-κB by H. pylori. The contribution of CAMKII and calmodulin, but not PKCs/CBM to the induction of an inflammatory response by H. pylori infection augment the understanding of the molecular mechanism involved and provide potential new disease markers for the diagnosis of gastric inflammatory diseases including gastric cancer.

Induction of brain microvascular endothelial cell urokinase expression by Cryptococcus neoformans facilitates blood-brain barrier invasion

The invasive ability of the blood-borne fungal pathogen Cryptococcus neoformans can be enhanced through interactions with host plasma components, such as plasminogen. Previously we showed by in vitro studies that plasminogen coats the surface of C. neoformans and is converted to the active serine protease, plasmin, by host plasminogen activators. Viable, but not formaldehyde- or sodium azide-killed, cryptococcal strains undergo brain microvascular endothelial cell-dependent plasminogen-to-plasmin activation, which results in enhanced, plasmin-dependent cryptococcal invasion of primary bovine brain microvascular endothelial cells and fungal ability to degrade plasmin substrates. In the present work, brain microvascular endothelial cells cultured with viable, but not killed, cryptococcal strains led to significant increases in both urokinase mRNA transcription and cell-associated urokinase protein expression. Soluble urokinase was also detected in conditioned medium from brain microvascular endothelial cells cultured with viable, but not killed, C. neoformans. Exposure of plasminogen pre-coated viable C. neoformans to conditioned medium from strain-matched brain microvascular endothelial cell-fungal co-cultures resulted in plasminogen-to-plasmin activation and plasmin-dependent cryptococcal invasion. siRNA-mediated silencing of urokinase gene expression or the use of specific inhibitors of urokinase activity abrogated both plasminogen-to-plasmin activation on C. neoformans and cryptococcal-brain microvascular endothelial cell invasion. Our results suggest that pathogen exploitation of the host urokinase-plasmin(ogen) system may contribute to C. neoformans virulence during invasive cryptococcosis.

Interleukin enhancer-binding factor 3 promotes breast tumor progression by regulating sustained urokinase-type plasminogen activator expression

Sustained urokinase-type plasminogen activator (uPA) expression is detected in aggressive breast tumors. Although uPA can be transiently upregulated by diverse extracellular stimuli, sustained, but not transiently upregulated uPA expression contributes to breast cancer invasion/metastasis. Unfortunately, how sustained uPA expression is achieved in invasive/metastatic breast cancer cells is unknown. Here, we show that sustained and transiently upregulated uPA expression are regulated by distinct mechanisms. Using a collection of transcription factor-targeted small-interfering RNAs, we discovered that interleukin enhancer-binding factor 3 (ILF3) is required for sustained uPA expression. Two discrete mechanisms mediate ILF3 action. The first is that ILF3 activates uPA transcription by binding to the CTGTT sequence in the nucleotides -1004∼-1000 of the uPA promoter; the second is that ILF3 inhibits the processing of uPA mRNA-targeting primary microRNAs (pri-miRNAs). Knockdown of ILF3 led to significant reduction in in vitro cell growth/migration/invasion and in vivo breast tumor development. Importantly, immunohistochemistry (IHC) showed that nuclear ILF3, but not cytoplasmic ILF3 staining correlates with elevated uPA level and higher grades of human breast tumor specimens. Nuclear localization of ILF3 highlights the role of ILF3 in sustained uPA expression as a transcription activator and pri-miRNA processing blocker. In conclusion, this study shows that ILF3 promotes breast tumorigenicity by regulating sustained uPA expression.

CARMA3 is overexpressed in colon cancer and regulates NF-κB activity and cyclin D1 expression

CARMA3 was recently reported to be overexpressed in cancers and associated with the malignant behavior of cancer cells. However, the expression of CARMA3 and its biological roles in colon cancer have not been reported. In the present study, we analyzed the expression pattern of CARMA3 in colon cancer tissues and found that CARMA3 was overexpressed in 30.8% of colon cancer specimens. There was a significant association between CARMA3 overexpression and TNM stage (p=0.0383), lymph node metastasis (p=0.0091) and Ki67 proliferation index (p=0.0035). Furthermore, knockdown of CARMA3 expression in HT29 and HCT116 cells with high endogenous expression decreased cell proliferation and cell cycle progression while overexpression of CARMA3 in LoVo cell line promoted cell proliferation and facilitated cell cycle transition. Further analysis showed that CARMA3 knockdown downregulated and its overexpression upregulated cyclin D1 expression and phospho-Rb levels. In addition, we found that CARMA3 depletion inhibited p-IκB levels and NF-κB activity and its overexpression increased p-IκB expression and NF-κB activity. NF-κB inhibitor BAY 11-7082 reversed the role of CARMA3 on cyclin D1 upregulation. In conclusion, our study found that CARMA3 is overexpressed in colon cancers and contributes to malignant cell growth by facilitating cell cycle progression through NF-κB mediated upregulation of cyclin D1.

Overexpression of CARMA3 in non-small-cell lung cancer is linked for tumor progression

We aimed to investigate the clinical significance of the expression of novel scaffold protein CARMA3 in non-small-cell lung cancer (NSCLC) and the biological function of CARMA3 in NSCLC cell lines. We observed moderate to high CARMA3 staining in 68.8% of 141 NSCLC specimens compared to corresponding normal tissues. The overexpression of CARMA3 was significantly correlated with TNM stage (P = 0.022) and tumor status (P = 0.013). CARMA3 upregulation also correlated with a shorter survival rate of patients of nodal status N0 (P = 0.042)as well as the expression of epidermal growth factor receptor (EGFR) (P = 0.009). In EGFR mutation positive cases, CARMA3 expression was much higher (87.5%) compared to non-mutation cases (66.1%). In addition, we observed that knockdown of CARMA3 inhibits tumor cell proliferation and invasion, and induces cell cycle arrest at the boundary between the G1 and S phase. We further demonstrated a direct link between CARMA3 and NF-κB activation. The change of biological behavior in CARMA3 knockdown cells may be NF-κB-related. Our findings demonstrated, for the first time, that CARMA3 was overexpressed in NSCLC and correlated with lung cancer progression, EGFR expression, and EGFR mutation. CARMA3 could serve as a potential companion drug target, along with NF-kB and EGFR in EGFR-mutant lung cancers.

MALT1 protease: a new therapeutic target in B lymphoma and beyond?

The identification of mucosa-associated lymphoid tissue lymphoma translocation 1 (MALT1) as a gene that is perturbed in the B-cell neoplasm MALT lymphoma, already more than a decade ago, was the starting point for an intense area of research. The fascination with MALT1 was fueled further by the observation that it contains a domain homologous to the catalytic domain of caspases and thus, potentially, could function as a protease. Discoveries since then initially revealed that MALT1 is a key adaptor molecule in antigen receptor signaling to the transcription factor NF-κB, which is crucial for lymphocyte function. However, recent discoveries show that this function of MALT1 is not restricted to lymphocytes, witnessed by the ever-increasing list of receptors from cells within and outside of the immune system that require MALT1 for NF-κB activation. Yet, a role for MALT1 protease activity was shown only recently in immune signaling, and its importance was then further strengthened by the dependency of NF-κB-addicted B-cell lymphomas on this proteolytic activity. Therapeutic targeting of MALT1 protease activity might, therefore, become a useful approach for the treatment of these lymphomas and, additionally, an effective strategy for treating other neoplastic and inflammatory disorders associated with deregulated NF-κB signaling.

From MALT lymphoma to the CBM signalosome: three decades of discovery

The advent of molecular cytogenetics has led to the elucidation of genetic abnormalities that cause various congenital and oncological disorders. In B cell lymphoma, for example, a number of chromosomal translocations have been identified in and associated with the etiology of specific subtypes of lymphoma. Several recurrent chromosomal translocations have been identified in extranodal marginal zone B cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). Cloning and characterization of the products of three mutually exclusive translocation breakpoints found in MALT lymphoma led to the discovery of a novel NF-κB-activating complex comprising the CARMA, Bcl10, and MALT1 proteins. This "CBM signalosome" acts downstream of the antigen receptors in lymphocytes as well as a number of non-lymphoid cell-surface receptors involved in a variety of biological processes. CBM signalosome activity is important for normal cellular functions and is perturbed in neoplastic and inflammatory disorders, making it a viable target for novel therapeutic design.

CARMA3 is crucial for EGFR-Induced activation of NF-κB and tumor progression

EGF activates NF-κB, and constitutively activated NF-κB contributes to EGFR mutation-associated tumorigenesis, but it remains unclear precisely how EGFR signaling leads to NF-κB activation. Here we report that CARMA3, a caspase recruitment domain (CARD)-containing scaffold molecule, is required for EGF-induced NF-κB activation. CARMA3 deficiency impaired the activation of the IKK complex following EGF stimulation, resulting in a defect of EGF-induced IκBα phosphorylation and NF-κB activation. We found that CARMA3 and Bcl10 contributed to several characteristics of EGFR-associated malignancy, including proliferation, survival, migration, and invasion. Most importantly, CARMA3 contributed to tumor growth in vivo. Our findings elucidate a crucial link between EGFR-proximal signaling components and the downstream IKK complex, and they suggest a new therapeutic target for treatment of EGFR-driven cancers.

The NF-κB pathway mediates lysophosphatidic acid (LPA)-induced VEGF signaling and cell invasion in epithelial ovarian cancer (EOC)

OBJECTIVES

Our previous report has implicated the involvement of VEGF-VEGFR-2 h signaling in LPA-induced EOC invasion. However, the mechanism by which LPA regulates VEGF and VEGFR-2 expression remains to be elucidated. In the present study, we systematically examined the signal transduction pathways activated by LPA and further evaluated whether LPA's effect on VEGF-VEGFR-2 signaling and EOC invasion was mediated by the activation of NF-κB pathway.

METHODS

Using a signal transduction PathwayFinder PCR array, we examined the expression change of 86 key genes representing 18 signal transduction pathways in DOV13 and SKOV3 cells upon LPA (20 μM) treatment. We also used quantitative PCR, Western blotting and ELISA to evaluate the effect of NF-κB pathway inhibition on VEGF(121), VEGF(165) and VEGFR-2 mRNA and protein expression/secretion with or without the presence of LPA (20 μM) in SKOV3. Cell invasion under various treatment conditions was assessed by Matrigel invasion assay and MMP-2 secretion was detected by gelatin zymography.

RESULTS

Our results showed that in both DOV13 and SKOV3, several of the NF-κB pathway components, such as TNF, are consistently activated by LPA stimulation. In addition, treatment with an NF-κB pathway activation inhibitor, at 10 μM, significantly decreased LPA-induced VEGF(121), VEGF(165) and VEGFR-2 mRNA expression and VEGF secretion, as well as LPA-induced SKOV3 invasion (p<0.05). When combined with an EGFR inhibitor, NF-κB pathway inhibition exhibited a significantly stronger effect than used alone (p<0.05) on reducing LPA-induced VEGF secretion and cell invasion. Additionally, NF-κB inhibition also decreased LPA-induced MMP-2 secretion and MMP-1 expression (p<0.05).

CONCLUSIONS

These results suggest that the NF-κB pathway plays an important role in LPA-induced VEGF signaling and EOC invasion and targeting this pathway may reveal potential therapeutic options for metastatic EOC.

NF-κB signaling pathways regulated by CARMA family of scaffold proteins

The NF-κB family of transcription factors plays a crucial role in cell activation, survival and proliferation. Its aberrant activity results in cancer, immunodeficiency or autoimmune disorders. Over the past two decades, tremendous progress has been made in our understanding of the signals that regulate NF-κB activation, especially how scaffold proteins link different receptors to the NF-κB-activating complex, the IκB kinase complex. The growing number of these scaffolds underscores the complexity of the signaling networks in different cell types. In this review, we discuss the role of scaffold molecules in signaling cascades induced by stimulation of antigen receptors, G-protein-coupled receptors and C-type Lectin receptors, resulting in NF-κB activation. Especially, we focus on the family of Caspase recruitment domain (CARD)-containing proteins known as CARMA and their function in activation of NF-κB, as well as the link of these scaffolds to the development of various neoplastic diseases through regulation of NF-κB.

CARMA3: A novel scaffold protein in regulation of NF-κB activation and diseases

CARD recruited membrane associated protein 3 (CARMA3) is a novel scaffold protein. It belongs to the CARMA protein family, and is known to activate nuclear factor (NF)-κB. However, it is still unknown which receptor functions upstream of CARMA3 to trigger NF-κB activation. Recently, several studies have demonstrated that CARMA3 serves as an indispensable adaptor protein in NF-κB signaling under some G protein-coupled receptors (GPCRs), such as lysophosphatidic acid (LPA) receptor and angiotensin (Ang) II receptor. Mechanistically, CARMA3 recruits its essential downstream molecules Bcl10 and MALT1 to form the CBM (CARMA3-Bcl10-MALT1) signalosome whereby it triggers NF-κB activation. GPCRs and NF-κB play pivotal roles in the regulation of various cellular functions, therefore, aberrant regulation of the GPCR/NF-κB signaling axis leads to the development of many types of diseases, such as cancer and atherogenesis. Recently, the GPCR/CARMA3/NF-κB signaling axis has been confirmed in these specific diseases and it plays crucial roles in the pathogenesis of disease progression. In ovarian cancer cell lines, knockdown of CARMA3 abolishes LPA receptor-induced NF-κB activation, and reduces LPA-induced ovarian cancer invasion. In vascular smooth cells, downregulation of CARMA3 substantially impairs Ang-II-receptor-induced NF-κB activation, and in vivo studies have confirmed that Bcl10-deficient mice are protected from developing Ang-II-receptor-induced atherosclerosis and aortic aneurysms. In this review, we summarize the biology of CARMA3, describe the role of the GPCR/CARMA3/NF-κB signaling axis in ovarian cancer and atherogenesis, and speculate about the potential roles of this signaling axis in other types of cancer and diseases. With a significant increase in the identification of LPA- and Ang-II-like ligands, such as endothelin-1, which also activates NF-κB via CARMA3 and contributes to the development of many diseases, CARMA3 is emerging as a novel therapeutic target for various types of cancer and other diseases.