Interleukin 32 (IL-32) contains a typical α-helix bundle structure that resembles focal adhesion targeting region of focal adhesion kinase-1

The γ-secretase inhibitor PF-03084014 combined with fludarabine antagonizes migration, invasion and angiogenesis in NOTCH1-mutated CLL cells

Targeting Notch signaling has emerged as a promising therapeutic strategy for chronic lymphocytic leukemia (CLL), especially for the poor prognostic subgroup of NOTCH1-mutated patients. Here, we report that the γ-secretase inhibitor PF-03084014 inhibits the constitutive Notch activation and induces selective apoptosis in CLL cells carrying NOTCH1 mutations. Combination of PF-03084014 with fludarabine has a synergistic antileukemic effect in primary NOTCH1-mutated CLL cells, even in the presence of the protective stroma. At transcriptional level, PF-03084014 plus fludarabine treatment induces the upregulation of the proapoptotic gene HRK and the downmodulation of MMP9, IL32 and RAC2 genes that are related to invasion and chemotaxis. PF-03084014 also overcomes fludarabine-mediated activation of nuclear factor-κB signaling. Moreover, this combination impairs angiogenesis and CXCL12-induced responses in NOTCH1-mutated CLL cells, in particular those related to tumoral migration and invasion. Importantly, all these collaborative effects are specific for NOTCH1 mutation and do not occur in unmutated cases. In conclusion, we provide evidence that Notch is a therapeutic target in CLL cases with NOTCH1-activating mutations, supporting the use of Notch pathway inhibitors in combination with chemotherapy as a promising approach for the treatment of these high-risk CLL patients.

M-CSF inhibits anti-HIV-1 activity of IL-32, but they enhance M2-like phenotypes of macrophages

M-CSF promotes the differentiation and survival of macrophages, and preferentially induces anti-inflammatory M2, rather than proinflammatory M1 macrophages. Recently, another cytokine, IL-32, was also shown to promote macrophage differentiation. In this article, we provide the first evidence, to our knowledge, that M-CSF has both additive and inhibitory effects on the macrophage-related activities of IL-32. When added to M-CSF-derived macrophages, M-CSF and IL-32 promoted macrophage survival, which was further enhanced by their combination. However, they had different effects on HIV-1 replication; that is, it was stimulated by M-CSF and inhibited by IL-32. Interestingly, the anti-HIV-1 activity of IL-32 was counteracted by M-CSF. Such inhibitory effect of M-CSF was not observed with IL-32-induced M1-like features including high cytokine/chemokine production and strong expression of the costimulatory molecule CD80. However, IL-32-treated macrophages unexpectedly showed also M2-like features including increased phagocytic activity, and high expression of CD14 and the scavenger receptor CD163, and the expression of CD14 and CD163 was further upregulated by cotreatment with M-CSF. The findings of this study regarding the unique functional interplay between M-CSF and IL-32 increase our understanding of the mechanisms that regulate the survival and M1/M2 ratio of macrophages, as well as HIV-1 replication in macrophages.

Interleukin-32 increases human gastric cancer cell invasion associated with tumor progression and metastasis

PURPOSE

The proinflammatory cytokine interleukin-32 (IL-32) is a novel tumor marker highly expressed in various human carcinomas, including gastric cancer. However, its effects on prognosis of patients with gastric cancer and cancer metastasis are virtually unknown at present. The main aim of this study was to explore the clinical significance of IL-32 in gastric cancer and further elucidate the molecular mechanisms underlying IL-32-mediated migration and invasion.

EXPERIMENTAL DESIGN

Gastric cancer cells with ectopic expression or silencing of IL-32 were examined to identify downstream molecules and establish their effects on cell motility, invasion, and lung metastasis in vivo.

RESULTS

IL-32 was significantly upregulated in gastric cancer and positively correlated with aggressiveness of cancer and poor prognosis. Ectopic expression of IL-32 induced elongated morphology and increased cell migration and invasion via induction of IL-8, VEGF, matrix metalloproteinase 2 (MMP2), and MMP9 expression via phosphor-AKT/phospho-glycogen synthase kinase 3β/active β-catenin as well as hypoxia-inducible factor 1α (HIF-1α) signaling pathways. Conversely, depletion of IL-32 in gastric cancer cells reversed these effects and decreased lung colonization in vivo. Examination of gene expression datasets in oncomine and staining of gastric cancer specimens demonstrated the clinical significance of IL-32 and its downstream molecules by providing information on their coexpression patterns.

CONCLUSIONS

IL-32 contributes to gastric cancer progression by increasing the metastatic potential resulting from AKT, β-catenin, and HIF-1α activation. Our results clearly suggest that IL-32 is an important mediator for gastric cancer metastasis and independent prognostic predictor of gastric cancer.

Interaction network mapping among IL-32 isoforms

IL-32 has been studied for its pleiotropic effects ranging from host immune responses to cell differentiation. Although several IL-32 isoforms have been characterized for their effects on cells, the roles of the others remain unclear. We previously reported that IL-32δ interacted with IL-32β and inhibited IL-32β-mediated IL-10 production. Thus, we performed comprehensive analyses to reveal more interactions between IL-32 isoforms in this study. We screened the interactions of 81 combinations of nine IL-32 isoforms by using a yeast two-hybrid assay, which identified 13 heterodimeric interactions. We verified these results by using reciprocal immunoprecipitation assays and reconfirmed 10 interactions, and presented the interaction network map between IL-32 isoforms. Our data suggest that IL-32 may have diverse intracellular effects through the interactions with its different isoforms.

IL-32 promotes angiogenesis

IL-32 is a multifaceted cytokine with a role in infections, autoimmune diseases, and cancer, and it exerts diverse functions, including aggravation of inflammation and inhibition of virus propagation. We previously identified IL-32 as a critical regulator of endothelial cell (EC) functions, and we now reveal that IL-32 also possesses angiogenic properties. The hyperproliferative ECs of human pulmonary arterial hypertension and glioblastoma multiforme exhibited a markedly increased abundance of IL-32, and, significantly, the cytokine colocalized with integrin αVβ3. Vascular endothelial growth factor (VEGF) receptor blockade, which resulted in EC hyperproliferation, increased IL-32 three-fold. Small interfering RNA-mediated silencing of IL-32 negated the 58% proliferation of ECs that occurred within 24 h in scrambled-transfected controls. Reduction of IL-32 neither affected apoptosis (insignificant changes in Bak-1, Bcl-2, Bcl-xL, lactate dehydrogenase, annexin V, and propidium iodide) nor VEGF or TGF-β levels, but siIL-32-transfected adult and neonatal ECs produced up to 61% less NO, IL-8, and matrix metalloproteinase-9, and up to 3-fold more activin A and endostatin. In coculture-based angiogenesis assays, IL-32γ dose-dependently increased tube formation up to 3-fold; an αVβ3 inhibitor prevented this activity and reduced IL-32γ-induced IL-8 by 85%. In matrigel plugs loaded with IL-32γ, VEGF, or vehicle and injected into live mice, we observed the anticipated VEGF-induced increase in neocapillarization (8-fold versus vehicle), but unexpectedly, IL-32γ was equally angiogenic. A second signal such as IFN-γ was required to render cells responsive to exogenous IL-32γ; importantly, this was confirmed using a completely synthetic preparation of IL-32γ. In summary, we add angiogenic properties that are mediated by integrin αVβ3 but VEGF-independent to the portfolio of IL-32, implicating a role for this versatile cytokine in pulmonary arterial hypertension and neoplastic diseases.

Inhibition of IL-32 and TSLP production through the attenuation of caspase-1 activation in an animal model of allergic rhinitis by Naju Jjok (Polygonum tinctorium)

In this study, we investigated the effects of Naju Jjok (Polygonum tinctorium Lour., NJJ) on interleukin (IL)-32 and thymic stromal lymphopoietin (TSLP) levels associated with allergic rhinitis (AR). Using female BALB/c mice, we created an animal model of ovalbumin (OVA)-induced AR. Prior to the callenge with OVA, the mice were administered, either nasally or orally with NJJ. In addition, we also used the eosinophilic cells line, Eol-1, stimulated with granulocyte‑macrophage colony-stimulation factor (GM-CSF). The mRNA and protein levels of inflammatory cytokines and markers [interleukin (IL)-32, IL-4, macrophage-inflammatory protein-2 (MIP-2), intercellular adhesion molecule-1 (ICAM-1), and cyclooxygenase-2 (COX-2)] were measured by RT-PCR and western blot analysis, respectively and serum levels were measured by ELISA. The increased levels of IL-32 in the mice with AR and in the stimulated eosinophilic cell line, Eol-1, were significantly reduced by NJJ. TSLP levels were also decreased following the oral administration of NJJ. Mice orally administered NJJ showed markedly alleviated clinical symptoms, such as a reduced number of nasal rubs, decreased spleen weight, decreased serum immunoglobulin E (IgE) levels and decreased serum histamine levels. The oral administration of NJJ significantly decreased the IL-4 levels, while increasing the interferon-γ levels in the spleen. The increased number of eosinophils and mast cells infiltrating the nasal mucosal tissue of the mice with AR were decreased following the oral administration of NJJ. NJJ effectively attenuated caspase-1 activity in the mice with AR and in the stimulated Eol-1 cells. The oral administration of NJJ significantly reduced the levels of inflammatory markers, such as MIP-2, ICAM-1 and COX-2. Furthermore, the intranasal administration of NJJ significantly reduced the early phase response to allergen exposure, such as nasal rubs, IgE production and histamine release, as well as the late phase responses, such as the expression of inflammatory markers. In conclusion, these data demonstrate that NJJ may play a regulatory role in nasal inflammation.

Interleukin-32δ interacts with IL-32β and inhibits IL-32β-mediated IL-10 production

There is growing evidence for multifunctional properties of IL-32. We previously demonstrated that IL-32β upregulates IL-10 production through the association with PKCδ. In this study, we examined the effects of other IL-32 isoforms on IL-10 production. We found that IL-32δ decreased IL-10 production and investigated the inhibitory mechanism of IL-32δ. We showed that IL-32δ suppressed IL-32β binding to PKCδ by interacting with IL-32β. The inhibitory effect of IL-32δ on IL-32β association with PKCδ was further verified by immuno-fluorescence staining. The co-localization of IL-32β and PKCδ around the nuclear membrane was disrupted by IL-32δ. Our data therefore indicate that IL-32δ plays an inhibitory role against IL-32β function, which also suggests that IL-32 may be regulated by its own isoform.

IL-32-PAR2 axis is an innate immunity sensor providing alternative signaling for LPS-TRIF axis

Interleukin (IL)-32 is known to exert adujvant effects on innate immune response, however, receptors and downstream signaling pathways remain to be clarified. Here we found that IL-32γ upregulated serine protease activity of proteinase-3 (PR3), in turn triggering protease-activated receptor 2 (PAR2) signaling. Interestingly, silencing of PR3 or PAR2 using siRNA markedly diminished IL-32γ-induced TNFα and IFN-β mRNA expression. IL-32γ-PAR2 axis utilized TRIF and Ras-Raf-1 pathways. On stimulation with lipopolysaccharide (LPS), differential activation of protein kinase C isoforms modulated the balance between LPS-TLR4-TRIF and IL-32-PAR2-TRIF axes, because LPS was a strong inducer of IL-32γ. IL-32-PAR2-TRIF axis might serve not only as an extracellular sensor of bacterial and autologous proteases, but also as a modulator of innate and adaptive immunity during infection.

Novel insights into the biology of interleukin-32

Interleukin (IL)-32 is known as a proinflammatory cytokine that is likely involved in several diseases, including infections, chronic inflammation, and cancer. Since the first report in 2005, IL-32 has been the subject of numerous studies to unravel the biological function of this molecule. For example, silencing of endogenous IL-32 in primary or cell lines of human origin consistently suppressed responses to Toll-like receptors. The protein folding structure of the six isoforms of IL-32 does not resemble that of any classical cytokine and as of this writing, a specific IL-32 receptor has not been identified. Instead, we propose a mechanism by which exposure to extracellular IL-32 or overexpression of the molecule results in binding to intracellular partners that influences functions such as gene expression, cell death, or survival. As such, this review offers insights into the role of IL-32 in several diseases, host defense, inflammation, immune function, and cancer. Finally, possibilities to target IL-32 in several diseases are proposed.

Role of interleukin-32 in chronic rhinosinusitis

PURPOSE OF REVIEW

IL-32 is a recently described proinflammatory cytokine and has been reported to be involved in inflammatory diseases. The purpose of this review is to discuss the role of IL-32 in chronic rhinosinusitis (CRS).

RECENT FINDINGS

Two groups have recently reported data regarding the expression of IL-32 in CRS. IL-32 was induced by IFN-γ, TNF-α, dsRNA, and incubation with Th1 cells in primary nasal epithelial cells. IL-32 may be elevated in epithelial cells from patients with CRS without nasal polyps. IL-32 was significantly elevated in whole sinonasal tissue samples of nasal polyps compared with control tissue. IL-32 mRNA expression positively correlated with mRNA for CD3 and macrophage mannose receptor in nasal polyp tissue. Immunohistochemical studies demonstrated localization of IL-32 in epithelium, CD3(+) and CD68(+) cells, suggesting that epithelial cells, T cells, and macrophages are the major IL-32-producing cells in CRS. Activation of these cell types may trigger IL-32-related inflammation in CRS.

SUMMARY

Elevated levels of IL-32 may play a role in the pathogenesis of CRS through its role as a proinflammatory cytokine and as an endogenous enhancer of pathogen-dependent cytokine production.

Interleukin (IL)-32β-mediated CCAAT/enhancer-binding protein α (C/EBPα) phosphorylation by protein kinase Cδ (PKCδ) abrogates the inhibitory effect of C/EBPα on IL-10 production

We previously reported that IL-32β promotes IL-10 production in myeloid cells. However, the underlying mechanism remains elusive. In this study, we demonstrated that IL-32β abrogated the inhibitory effect of CCAAT/enhancer-binding protein α (C/EBPα) on IL-10 expression in U937 cells. We observed that the phosphorylation of C/EBPα Ser-21 was inhibited by a PKCδ-specific inhibitor, rottlerin, or IL-32β knockdown by siRNA and that IL-32β shifted to the membrane from the cytosol upon phorbol 12-myristate 13-acetate treatment. We revealed that IL-32β suppressed the binding of C/EBPα to IL-10 promoter by using ChIP assay. These data suggest that PKCδ and IL-32β may modulate the effect of C/EBPα on IL-10 expression. We next demonstrated by immunoprecipitation that IL-32β interacted with PKCδ and C/EBPα, thereby mediating C/EBPα Ser-21 phosphorylation by PKCδ. We showed that IL-32β suppressed the inhibitory effect of C/EBPα on IL-10 promoter activity. However, the IL-10 promoter activity was reduced to the basal level by rottlerin treatment. When C/EBPα serine 21 was mutated to glycine (S21G), the inhibitory effect of C/EBPα S21G on IL-10 promoter activity was not modulated by IL-32β. Taken together, our results show that IL-32β-mediated C/EBPα Ser-21 phosphorylation by PKCδ suppressed C/EBPα binding to IL-10 promoter, which promoted IL-10 production in U937 cells.

Interleukin-32 expression is associated with a poorer prognosis in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) represent the sixth most common malignancy diagnosed worldwide. Patient's survival is low due the high frequency of tumor recurrence. Inflammation promotes carcinogenesis as well as the formation of metastasis. Indeed, proinflammatory mediators are known to stimulate the expression of specific transcription factors such as Snai1 and to increase the ability of tumor cells to migrate into distant organs. The atypical interleukin-32 (IL32) was mainly described to exacerbate inflammatory responses in rheumatoid arthritis and inflammatory bowel diseases. IL32 is expressed in various cancers but its role in HNSCC physiology is still unexplored. Here, we analyzed the expression of IL32 and its implication on HNSCC aggressiveness. We showed that patients with tumor expressing high amounts of IL32 exhibit decreased disease-free periods (20.5 mo vs. 41 mo, P = 0.0041) and overall survival (P = 0.0359) in comparison with individuals with weak IL32 tumor expression. This overexpression was negatively correlated with gender (P = 0.0292) and p53 expression (P = 0.0307). In addition, in vitro data linked IL32 expression to metastasis formation since IL32 inhibition decreased Snai1 expression and tumor cell migration in a Boyden chamber assay. Our data provide new insight into the role of IL32 in HNSCC aggressiveness.

Intracellular interaction of interleukin (IL)-32α with protein kinase Cε (PKCε ) and STAT3 protein augments IL-6 production in THP-1 promonocytic cells

IL-32α is known as a proinflammatory cytokine. However, several evidences implying its action in cells have been recently reported. In this study, we present for the first time that IL-32α plays an intracellular mediatory role in IL-6 production using constitutive expression systems for IL-32α in THP-1 cells. We show that phorbol 12-myristate 13-acetate (PMA)-induced increase in IL-6 production by IL-32α-expressing cells was higher than that by empty vector-expressing cells and that this increase occurred in a time- and dose-dependent manner. Treatment with MAPK inhibitors did not diminish this effect of IL-32α, and NF-κB signaling activity was similar in the two cell lines. Because the augmenting effect of IL-32α was dependent on the PKC activator PMA, we tested various PKC inhibitors. The pan-PKC inhibitor Gö6850 and the PKCε inhibitor Ro-31-8220 abrogated the augmenting effect of IL-32α on IL-6 production, whereas the classical PKC inhibitor Gö6976 and the PKCδ inhibitor rottlerin did not. In addition, IL-32α was co-immunoprecipitated with PMA-activated PKCε, and this interaction was totally inhibited by the PKCε inhibitor Ro-31-8220. PMA-induced enhancement of STAT3 phosphorylation was observed only in IL-32α-expressing cells, and this enhancement was inhibited by Ro-31-8220, but not by Gö6976. We demonstrate that IL-32α mediated STAT3 phosphorylation by forming a trimeric complex with PKCε and enhanced STAT3 localization onto the IL-6 promoter and thereby increased IL-6 expression. Thus, our data indicate that the intracellular interaction of IL-32α with PKCε and STAT3 promotes STAT3 binding to the IL-6 promoter by enforcing STAT3 phosphorylation, which results in increased production of IL-6.

Interleukin-32: a predominantly intracellular proinflammatory mediator that controls cell activation and cell death

In this review, we will discuss the current knowledge on IL-32 and provide new insights regarding the biological function of IL-32. IL-32 is seen as a cytokine that can induce a range of proinflammatory mediators and contribute to autoimmune diseases, such as rheumatoid arthritis, however present knowledge demonstrates that IL-32 is not a classical cytokine. We present the history of this cytokine, the role of IL-32 in several diseases and discuss a possible novel role of intracellular IL-32 in cell homeostasis. Taken into account the observed biological functions of IL-32, it may belong to a class of cytokines, like IL-1α, IL-33, and IL-37, with both intracellular and extracellular functions.