Search

ABIN-1, also called TNIP1, is an ubiquitin-binding protein that serves an important role in suppressing RIPK1-independent apoptosis, necroptosis, and NF-κB activation. However, the involvement of ABIN-1 in the regulation of RIPK1-dependent apoptosis (RDA) is unknown. In this study, we found that poly(I:C) + TAK1 inhibitor 5Z-7-oxozeaenol (P5) concurrently induces RDA and necroptosis in Abin-1−/−, but not in Abin-1+/+ mouse embryonic fibroblasts (MEFs). Upon P5 stimulation, cells initially die by necroptosis and subsequently by RDA. Furthermore, we explored the therapeutic effect of ABIN-1 deficiency in necroptosis-based cancer therapy in colorectal cancer (CRC). We found that poly(I:C) + 5Z-7-oxozeaenol + IDN-6556 (P5I) yields a robust pro-necroptosis response, and ABIN-1 deficiency additionally enhances this P5I-induced necroptosis. Moreover, phase I/II cIAP inhibitor birinapant with clinical caspase inhibitor IDN-6556 (BI) alone and 5-fluorouracil with IDN-6556 (FI) alone are sufficient to induce necroptotic cell death in CRC cells by promoting auto-secretion of tumor necrosis factor (TNF); ABIN-1 deficiency amplifies the BI- or FI-induced necroptosis. Two independent xenograft experiments using HT-29 or COLO205 cells show that both BI and P5I remarkably inhibit tumor growth via necroptosis activation. For poly(I:C)-induced cell death, the sensitizing effect of ABIN-1 deficiency on cell death may be attributed to increased expression of TLR3. In TNF-induced necroptosis, ABIN-1 deficiency increases TNF-induced RIPK1 polyubiquitination by reducing the recruitment of ubiquitin-editing enzyme A20 to the TNFR1 signaling complex and induces more TNF secretion in CRC cells upon pro-necroptosis stimulation. With this combined data, ABIN-1 deficiency promotes greater sensitization of CRC cells to necroptosis.

Esophageal squamous cell carcinoma (ESCC) is one of the most lethal cancers worldwide and evolves often to lung metastasis. P53R175H (homologous to Trp53R172H in mice) is a common hot spot mutation. How metastasis is regulated by p53R175H in ESCC remains to be investigated. To investigate p53R175H-mediated molecular mechanisms, we used a carcinogen-induced approach in Trp53R172H/− mice to model ESCC. In the primary Trp53R172H/− tumor cell lines, we depleted Trp53R172H (shTrp53) and observed a marked reduction in cell invasion in vitro and lung metastasis burden in a tail-vein injection model in comparing isogenic cells (shCtrl). Furthermore, we performed bulk RNA-seq to compare gene expression profiles of metastatic and primary shCtrl and shTrp53 cells. We identified the YAP-BIRC5 axis as a potential mediator of Trp53R172H-mediated metastasis. We demonstrate that expression of Survivin, an antiapoptotic protein encoded by BIRC5, increases in the presence of Trp53R172H. Furthermore, depletion of Survivin specifically decreases Trp53R172H-driven lung metastasis. Mechanistically, Trp53R172H but not wild-type Trp53, binds with YAP in ESCC cells, suggesting their cooperation to induce Survivin expression. Furthermore, Survivin high expression level is associated with increased metastasis in several GI cancers. Taken together, this study unravels new insights into how mutant p53 mediates metastasis.

Ubiquitylation of the TNFR1 signalling complex (TNF-RSC) controls the activation of RIPK1, a kinase critically involved in mediating multiple TNFα-activated deleterious events. However, the molecular mechanism that coordinates different types of ubiquitylation modification to regulate the activation of RIPK1 kinase remains unclear. Here, we show that ABIN-1/NAF-1, a ubiquitin-binding protein, is recruited rapidly into TNF-RSC in a manner dependent on the Met1-ubiquitylating complex LUBAC to regulate the recruitment of A20 to control Lys63 deubiquitylation of RIPK1. ABIN-1 deficiency reduces the recruitment of A20 and licenses cells to die through necroptosis by promoting Lys63 ubiquitylation and activation of RIPK1 with TNFα stimulation under conditions that would otherwise exclusively activate apoptosis in wild-type cells. Inhibition of RIPK1 kinase and RIPK3 deficiency block the embryonic lethality of Abin-1 –/– mice. We propose that ABIN-1 provides a critical link between Met1 ubiquitylation mediated by the LUBAC complex and Lys63 deubiquitylation by phospho-A20 to modulate the activation of RIPK1.

Bone is one of the most preferred sites of metastasis in lung cancer. Currently, bisphosphonates and denosumab are major agents for controlling tumor-associated skeletal-related events (SREs). However, both bisphosphonates and denosumab significantly increase the risk for jaw osteonecrosis. Statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors and the most frequently prescribed cholesterol-lowering agents, have been reported to inhibit tumor progression and induce autophagy in cancer cells. However, the effects of statin and role of autophagy by statin on bone metastasis are unknown. In this study, we report that fluvastatin effectively prevented lung adenocarcinoma bone metastasis in a nude mouse model. We further reveal that fluvastatin-induced anti-bone metastatic property was largely dependent on its ability to induce autophagy in lung adenocarcinoma cells. Atg5 or Atg7 deletion, or 3-methyadenine (3-MA) or Bafilomycin A1 (Baf A1) treatment prevented the fluvastatin-induced suppression of bone metastasis. Furthermore, we reveal that fluvastatin stimulation increased the nuclear p53 expression, and fluvastatin-induced autophagy and anti-bone metastatic activity were mostly dependent on p53., Highlights • Fluvastatin effectively prevents lung adenocarcinoma bone metastasis in a nude mouse model. • Fluvastatin-induced anti-bone metastatic property was largely dependent on its ability to induce autophagy. • Fluvastatin-induced autophagy and anti-bone metastatic activity are mediated by p53. Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are most frequently prescribed cholesterol-lowering agent with minimal side effects. In this study, we present a novel function of statins in suppressing lung adenocarcinoma bone metastasis, and this function is dependent on statin-induced autophagy. Currently, there is no cure for bone metastasis, and the current treatment options using anti-bone metastatic agents have negative side effects. For example, bisphosphonates or denosumab treatments reduce tumor-associated skeletal-related events, but simultaneously increase the risk of the osteonecrosis in the jaw. As a possible therapeutic treatment option, fluvastatin is promising to cancer patients with a high risk of bone metastasis.

Summary The nuclear factor-κB (NF-κB) family of transcription factors play an essential role for the regulation of inflammatory responses, immune function and malignant transformation. Aberrant activity of this signalling pathway may lead to inflammation, autoimmune diseases and oncogenesis. Over the last two decades great progress has been made in the understanding of NF-κB activation and how the response is counteracted for maintaining tissue homeostasis. Therapeutic targeting of this pathway has largely remained ineffective due to the widespread role of this vital pathway and the lack of specificity of the therapies currently available. Besides regulatory proteins and microRNAs, long non-coding RNA (lncRNA) is emerging as another critical layer of the intricate modulatory architecture for the control of the NF-κB signalling circuit. In this paper we focus on recent progress concerning lncRNA-mediated modulation of the NF-κB pathway, and evaluate the potential therapeutic uses and challenges of using lncRNAs that regulate NF-κB activity.

Metastasis contributes to the vast majority of cancer-related mortality. Regulatory mechanisms of the multistep invasion-metastasis cascade are being unraveled. TP53 is the most frequently mutated gene across human cancers. Accumulating evidence has shown that mutations of TP53 not only lead to loss of function or dominant negative effects, but also promotes a gain of function. Specifically, gain of function mutant p53 promotes cancer cell motility, invasion, and metastasis. Here, we summarize the mechanisms and functions of mutant p53 that foster metastasis in different types of cancers. We also discuss the prognostic value of mutant p53 and current status of therapeutic strategies targeting mutant p53. Future studies will shed light on discovering novel mechanisms of mutant p53-driven cancer metastasis and developing innovative therapeutics to improve clinical outcomes in patients harboring p53 mutations.

Necroptosis is a caspase-independent form of regulated cell death executed by the receptor-interacting protein kinase 1 (RIP1), RIP3, and mixed lineage kinase domain-like protein (MLKL). Recently, necroptosis-based cancer therapy has been proposed to be a novel strategy for antitumor treatment. However, a big controversy exists on whether this type of therapy is feasible or just a conceptual model. Proponents believe that because necroptosis and apoptosis use distinct molecular pathways, triggering necroptosis could be an alternative way to eradicate apoptosis-resistant cancer cells. This hypothesis has been preliminarily validated by recent studies. However, some skeptics doubt this strategy because of the intrinsic or acquired defects of necroptotic machinery observed in many cancer cells. Moreover, two other concerns are whether or not necroptosis inducers are selective in killing cancer cells without disturbing the normal cells and whether it will lead to inflammatory diseases. In this review, we summarize current studies surrounding this controversy on necroptosis-based antitumor research and discuss the advantages, potential issues, and countermeasures of this novel therapy.

MicroRNAs (miRNAs) are endogenous 22 nt non-coding RNAs that target mRNAs for cleavage or translational repression. Numerous miRNAs regulate programmed cell death including apoptosis, autophagy and necroptosis. We summarize how miRNAs regulate apoptotic, autophagic and necroptotic pathways and cancer progression. We also discuss how miRNAs link different types of cell death.

Five-fluorouracil (5-FU) is a widely used chemotherapeutic agent for digestive system tumors; however, continuous use of 5-FU may cause severe side effects, including myelosuppression and immunosuppression. Our previous study revealed that calcineurin B subunit (CnB), an innovative genetic engineering antitumor protein, possesses tumor-suppressive effects with low toxicity. CnB can bind to and activate integrin αM on macrophages, subsequently promoting the expression, and secretion of TNF-related apoptosis-inducing ligand, a specific proapoptotic cytokine. In the present study, whether the combined use of CnB and 5-FU can reverse the myelosuppression, and immunosuppressive effects of 5-FU by reactivating the immune system thus increasing antitumor efficacy, was investigated. It was demonstrated that combined treatment of 5-FU and CnB led to increased tumor-suppressive effects, as indicated by reduced tumor volume and weight when compared with 5-FU or CnB treatment alone in a hepatoma xenograph model. In addition, it was demonstrated that combined treatment inhibited the proliferation of hepatoma cells. Notably, the addition of CnB to 5-FU-based therapy completely reversed the immunosuppressive effect of 5-FU. The spleen index and total number of white blood cells in the combination group were higher compared with that of the 5-FU alone group. Furthermore, pathological examinations indicated that CnB attenuated 5-FU-induced organ damage. Based on these findings, it is proposed that CnB may serve as a novel and promising drug candidate for the improvement of 5-FU-based chemotherapy.

MALAT1 is a conserved long noncoding RNA whose expression correlates with many human cancers. However, its significance in immunity remains largely unknown. Here, we observe that MALAT1 is upregulated in lipopolysaccharide (LPS)-activated macrophages. Knockdown of MALAT1 increases LPS-induced expression of TNFα and IL-6. Mechanistically, MALAT1 was found to interact with NF-κB in the nucleus, thus inhibiting its DNA binding activity and consequently decreasing the production of inflammatory cytokines. Additionally, abnormal expression of MALAT1 was found to be NF-κB-dependent. These findings suggest that MALAT1 may function as an autonegative feedback regulator of NF-κB to help fine-tune innate immune responses.

Previous studies have shown that excess calcineurin subunit B (CnB) associates with mitochondria. Here, CnB overexpression increased CN activity in cells and enhanced TNF-alpha-induced cell death independent of CN activity. Overexpression of CnB increased intracellular Ca2+ concentration, enhanced caspase-3 activity, reduced Bcl-2 expression, and decreased mitochondrial membrane potential, with no change of caspase-8 or p53. CnB bound to isolated mitochondria in a Ca(2+)-dependent manner, and stimulated cytochrome c release from the mitochondria. Altogether, these results demonstrate that CnB is capable of promoting TNF-alpha-induced apoptosis, possibly through effects on mitochondrial functions.

We showed previously that calcineurin B subunit (CnB) protein activates innate immune cells including macrophages, monocytes and dendritic cells and acts as an adjuvant of a model antigen (ovalbumin) and a recombinant pneumolysin antigen, but the detailed mechanism is not clear and whether it can serve as an adjuvant of a commercial HBV vaccine is unknown. Here, we report that CnB promotes inflammatory cytokines production, splenocytes proliferation and NK lytic activity, and that CnB-induced inflammatory cytokines (IFN-γ, IL-6, TNF-α) production is dependent on integrin αM. Animal experiments demonstrate that CnB markedly increases the total anti-HBs antibodies in a dose and time dependent manner. Furthermore, CnB increases both anti-HBs IgM and anti-HBs IgG titers and changes the balance of IgG2a and IgG1. Combined use of CnB and CpG induces more cytokines production in splenocytes, as well as more anti-HBs antibodies production in vivo. These results reveal a probable mechanism of CnB-induced inflammatory cytokines production and further demonstrate that CnB is a novel and effective adjuvant of Engerix-B ® HBV vaccine.

Protective immunity involves a dynamic balance between humoral and cellular immune responses. In the present work we demonstrated that recombinant human calcineurin subunit B (rhCnB) stimulated the expression of the surface molecules CD83, CD80, CD86, CD40, and HLA-DR. It also promoted secretion of inflammatory cytokines IL-6, TNF-α, and IL-1β by human PBMC-derived dendritic cells. In in vivo experiments, splenocytes from BALB/c mice immunized with pneumolysin plus rhCnB contained a higher percentage of CD3 + CD4 + T lymphocytes, produced more antigen-specific splenocyte proliferation activity, and had higher anti-pneumolysin immunoglobulin G (IgG) titers. Transcript levels of cytokines such as IL-4, IL-10, and IFN-γ in the splenocytes were also upregulated when in vitro stimulated with pneumolysin. Thus, rhCnB promoted a mixed Th1/Th2 type immune response when given together with the specific antigen PN. RhCnB could have potential as a prophylactic vaccine adjuvant.

Calcineurin (CN) is a Ca2+/calmodulin-dependent phosphatase, which consists of a catalytic A-subunit (CnA) and a regulatory B-subunit (CnB). Endogenous CnA and CnB have a strong corelationship in cancer cell lines. Through the introduction of CnB and its mutants in cells, we show that CnB does not increase the expression of CnA but protects it from degradation. CnB M118 is necessary for tight binding to CnA. Point mutations of CnB M118 also do not increase the expression of CnA but protect it from degradation. Furthermore, CnB M118K fails to enhance the activities of NF-AT and p53 induced by CnA in HeLa-s cells. Mutations in CnB M118 may prove to be a valuable marker in the diagnostics of some important illnesses such as Alzheimer’s disease.

Metastasis is a crucial hallmark of cancer progression, which involves numerous factors including the degradation of the extracellular matrix (ECM), the epithelial-to-mesenchymal transition (EMT), tumor angiogenesis, the development of an inflammatory tumor microenvironment, and defects in programmed cell death. Programmed cell death, such as apoptosis, autophagy, and necroptosis, plays crucial roles in metastatic processes. Malignant tumor cells must overcome these various forms of cell death to metastasize. This review summarizes the recent advances in the understanding of the mechanisms by which key regulators of apoptosis, autophagy, and necroptosis participate in cancer metastasis and discusses the crosstalk between apoptosis, autophagy, and necroptosis involved in the regulation of cancer metastasis.

Calcineurin (CN), a unique protein phosphatase, plays an important role in immune regulation. In this study we used CN as a target enzyme to investigate the immunosuppressive properties of a series of natural compounds from Garcinia mangostana L., and discovered an active compound, isogarcinol. Enzymatic assays showed that isogarcinol inhibited CN in a dose-dependent manner. At concentrations resulting in relatively low cytotoxicity isogarcinol significantly inhibited proliferation of murine spleen T-lymphocytes induced by concanavalin A (ConA) and the mixed lymphocyte reaction (MLR). In addition, it performed much better in acute toxicity tests and via oral administration in mice than cyclosporin A (CsA), with few adverse reactions and low toxicity in experimental animals. Oral administration of isogarcinol in mice resulted in a dose-dependent decrease in delayed type hypersensitivity (DTH) and prolonged graft survival in allogeneic skin transplantation. These findings suggest that isogarcinol could serve as a new oral immunomodulatory drug for preventing transplant rejection, and for long-term medication in autoimmune diseases.

We showed previously that the calcineurin B subunit (CnB) plays an important role in activation of peritoneal macrophage, but the underlying mechanism remained unknown. To examine whether there is a CnB receptor on peritoneal macrophages, we performed the radioligand binding assay of receptors. The receptor saturation binding curve demonstrated high-affinity and specific binding; the maximum binding was 1090 fmol/105 cells, and the Kd was 70.59 pM. Then, we used a CnB affinity resin to trap potential receptors from highly purified peritoneal macrophage membranes. Mass spectrometry analysis showed that the binding protein was mouse integrin αM. We next performed a competition binding experiment to confirm the binding of CnB to integrin αM. This showed that FITC-CnB bound specifically to peritoneal macrophages and that binding was blocked by the addition of integrin αM Ab. We observed that CnB could induce TRAIL gene expression in peritoneal macrophages in vitro and in vivo. Integrin αM Ab blocking, RNA interference, and ligand competition experiments demonstrated that CnB-induced TRAIL expression is dependent on integrin αM. Furthermore, the tumoricidal activity of CnB-activated peritoneal macrophages is partially dependent on TRAIL. In addition, CnB treatment significantly prolongs the survival of mice bearing H22 ascites tumors, which has a positive correlation with the induction level of TRAIL. These results reveal a novel function of the CnB in innate immunity and cancer surveillance. They also point to a new signaling pathway leading to induction of TRAIL and suggest a possible application of CnB in cancer therapy.

We showed previously that calcineurin B subunit (CnB) could inhibit S180 solid tumor growth in mice and prolong the survival of mice bearing H22 ascites tumors, but the underlying antitumor mechanism remained unclear. Here, we report that the calcineurin B subunit binds to CD11b on RAW264.7 macrophages and induces TRAIL expression and NF-κB activation in a dose and time dependent manner, and that CnB-induced TRAIL expression and NF-κB activation are both dependent on this CD11b. Furthermore, CnB-induced TRAIL expression is mediated by NF-κB. These findings reveal a novel signaling pathway (CnB-CD11b-NF-κB-TRAIL) regulating TRAIL expression and may help to understand the roles of the calcineurin B subunit in the regulation of innate immunity.

Calcineurin is the only Ca2+/calmodulin-dependent serine/threonine protein phosphatase. The roles of the cytosolic calcineurin have been well researched; however, the roles of the serum calcineurin remain unknown. Here, we report that the recombinant human calcineurin B subunit (CnB) can bind to rabbit platelets and show an antiplatelet aggregation activity. Furthermore, CnB exerts an anticoagulant effect by prolonging the activated partial thromboplastin time and thrombin time and reducing the plasma fibrinogen concentration in a dose-dependent manner. We further reveal that the functional domain associated with the anticoagulant activity of CnB is located in the C-terminus. Hemolysis test and intravenous stimulation study show that the recombinant CnB does not cause obvious hemolysis and is safe for intravenous injection. These results reveal a new function of calcineurin B subunit. They also give an explanation for the roles of calcineurin B subunit in serum and point to a possible implication in antithrombotic therapy. © 2011 IUBMB IUBMB Life, 63(11): 1037–1044, 2011

Safe and potent adjuvants are required to establish effective vaccines. In the present work, we show that calcineurin subunit B promotes the secretion of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin-12p70 (IL-12 p70), IL-6 and the chemokine IL-8. It also up-regulates transcript levels of chemokines in bone marrow-derived dendritic cells. In an animal model, C57BL/6 mice were divided into four groups, immunized with ovalbumin (OVA), OVA mixed with calcineurin subunit B (CnB), CnB and PBS, respectively. The splenocytes from mice immunized with OVA in combination with CnB produced higher levels of IFN-γ and CTL when in vitro stimulated with OVA protein. Subcutaneous (s.c.) immunization of C57BL/6 mice with OVA plus CnB conferred greater protection against tumor-forming E.G7-OVA cells than did injection of OVA alone, and the survival rate of mice immunized intraperitoneally was higher than that of mice immunized s.c. Thus, CnB exerts potent adjuvant effects that polarize responses toward T(h)1 and elicit anti-tumor and anti-infection immunity. CnB could be of use as a prophylactic adjuvant as it is a human-derived safe agent and has immune-modulating effects that promote the control of cancer and infectious diseases.

Macrophages are involved in tumor growth and progression. They infiltrate into tumors and cause inflammation, which creates a microenvironment favoring tumor growth and metastasis. However, certain stimuli may induce macrophages to act as tumor terminators. Here we report that the calcineurin B subunit (CnB) synergizes with IFN-γ to make macrophages highly cytotoxic to cancer cells. Furthermore, CnB and IFN-γ act synergistically to polarize mouse tumor-associated macrophages, as well as human monocyte-derived macrophages to an M1-like phenotype. This synergy is mediated by the crosstalk between CnB-engaged integrin αM-p38 MAPK signaling and IFN-γ-initiated p38/PKC-δ/Jak2 signaling. Interestingly, the signal transducer and activator of transcription 1 (STAT1) is a key factor that orchestrates the synergy of CnB and IFN-γ, and the phosphorylation status at Ser727 and Tyr701 of STAT1 is directly regulated by CnB and IFN-γ.