Conservation of the genomic structure and receptor-mediated signaling between human and rat IL-24

Regulation of IL-24/IL-20R2 complex formation using photocaged tyrosines and UV light

Human interleukin 24 (IL-24) is a multifunctional cytokine that represents an important target for autoimmune diseases and cancer. Since the biological functions of IL-24 depend on interactions with membrane receptors, on-demand regulation of the affinity between IL-24 and its cognate partners offers exciting possibilities in basic research and may have applications in therapy. As a proof-of-concept, we developed a strategy based on recombinant soluble protein variants and genetic code expansion technology to photocontrol the binding between IL-24 and one of its receptors, IL-20R2. Screening of non-canonical ortho-nitrobenzyl-tyrosine (NBY) residues introduced at several positions in both partners was done by a combination of biophysical and cell signaling assays. We identified one position for installing NBY, tyrosine70 of IL-20R2, which results in clear impairment of heterocomplex assembly in the dark. Irradiation with 365-nm light leads to decaging and reconstitutes the native tyrosine of the receptor that can then associate with IL-24. Photocaged IL-20R2 may be useful for the spatiotemporal control of the JAK/STAT phosphorylation cascade.

Insights into the Mechanisms of Action of MDA-7/IL-24: A Ubiquitous Cancer-Suppressing Protein

Melanoma differentiation associated gene-7/interleukin-24 (MDA-7/IL-24), a secreted protein of the IL-10 family, was first identified more than two decades ago as a novel gene differentially expressed in terminally differentiating human metastatic melanoma cells. MDA-7/IL-24 functions as a potent tumor suppressor exerting a diverse array of functions including the inhibition of tumor growth, invasion, angiogenesis, and metastasis, and induction of potent "bystander" antitumor activity and synergy with conventional cancer therapeutics. MDA-7/IL-24 induces cancer-specific cell death through apoptosis or toxic autophagy, which was initially established in vitro and in preclinical animal models in vivo and later in a Phase I clinical trial in patients with advanced cancers. This review summarizes the history and our current understanding of the molecular/biological mechanisms of MDA-7/IL-24 action rendering it a potent cancer suppressor.

Role of IL-24 in NK cell activation and its clinical implication in systemic lupus erythematosus

OBJECTIVES

Interleukin (IL)-24 has been considered as an inflammatory cytokine in autoimmune diseases. However, conflicting data exist and its biological function remains controversial. Additionally, little is known about its functional impact on natural killer (NK) cells. The aim of this study was to investigate the role of IL-24 in NK cell activation and its clinical implication in systemic lupus erythematosus (SLE).

METHODS

Serum cohort consisting of 299 SLE patients, 214 RA patients, and 159 healthy controls (HCs) and plasma cohort consisting of 70 SLE patients, 82 RA patients, and 123 HCs were included in evaluating IL-24 concentrations. Impact of IL-24 on NK cell activation was assessed in two NK cell subsets, i.e., CD56^dimCD16⁺ and CD56^brightCD16^- NK cells. Human NK-92 cell line was applied to evaluate functional potential of IL-24 on NK cell migration and invasion.

RESULTS

Serum and plasma levels of IL-24 were comparable between patients with SLE or RA and HCs. While recombinant human (rh) IL-2 consistently induced an increased expression of CD69 on both CD56^dimCD16⁺ and CD56^brightCD16^- cells derived from both healthy subjects and patients with SLE, IL-24 alone was insufficient to activate the CD56^dim and CD56^bright NK cells. Similarly, while the migratory NK-92 cell numbers were significantly increased with rhIL-2 stimulation, IL-24 alone was unable to enhance NK-92 cell migratory and invasive capacity.

CONCLUSION

Our data indicate that there were no significant differences in serum and plasma concentrations of IL-24 between SLE patients and healthy controls. Recombinant IL-24 has no effect on NK cell activation and migration. Key points • This is the first study to investigate functional potential of IL-24 on NK cell activation. • Recombinant IL-24 lacks functional capacity on NK cell activation in either CD56^dimCD16⁺ or CD56^brightCD16^- NK cell subsets derived from both healthy subjects and patients with SLE. • No significant differences in serum and plasma levels of IL-24 between SLE patients and healthy controls.

A Broad Blockade of Signaling from the IL-20 Family of Cytokines Potently Attenuates Collagen-Induced Arthritis

Two heterodimeric receptors consisting of either IL-20R1 or IL-22R1 in complex with a common β receptor subunit IL-20R2 are shared by three of the IL-20 family of cytokines: IL-19, IL-20, and IL-24. These proinflammatory cytokines have been implicated in the pathogenesis of some autoimmune diseases, including rheumatoid arthritis (RA), psoriasis, and atopic dermatitis. Although mAbs against IL-19 and IL-20 have each been shown to modulate disease severity of collagen-induced arthritis in animal models, and anti-IL-20 therapeutic Ab has exhibited some efficacy in the treatment of RA in clinical trials, benefits for a complete blockade of these functionally redundant cytokines remain to be explored. In this report, we show that recombinant human soluble IL-20R2-Fc fusion protein binds to IL-19, IL-20, and IL-24 with similar high affinity and blocks their signaling in vitro. In DBA/1 mouse collagen-induced arthritis model, recombinant human IL-20R2-Fc exhibits comparable efficacy as TNF blocker etanercept in the treatment of established arthritis, whereas the combined use of both biologics manifests little synergistic therapeutic effects. In situ ligand-receptor functional binding analysis shows that a large amount of immune infiltrates expressing high levels of TNFR and IL-20 subfamily cytokines congregate within the inflamed disease tissues. Colocalization experiments reveal that signals from IL-20R2 and TNF transduction pathways seem to converge in macrophages and function in tandem in orchestrating the pathogenesis of RA. Elucidation of this interaction provides a better understanding of cytokine cross-talk in RA and a rationale for more effective biologic therapies that target IL-20R2 instead of individual cytokines from IL-20 family.

Alternative splicing directs two IL-20R2 isoforms and is responsible for the incomplete gene knockout via the exon I ablation

Two heterodimeric receptors consisting of interleukin (IL)-20R2 are shared by three of the IL-20 family of cytokines, IL-19, IL-20 and IL-24. Along with IL-22, these cytokines are downstream effectors of IL-23 and have been implicated in keratinocyte functions and the pathogenesis of psoriasis. Surprisingly, whereas knocking out either the IL-23 or IL-22 gene abolished imiquimod-induced psoriatic phenotypes in mice, similar attempt for IL-20R2 had little effect. Here, we report that the apparent disparity may result from a new IL-20R2 isoform encoded by an alternatively spliced transcript which survived the previous attempt for IL-20R2 gene knockout via the exon I deletion.

The Role of Biological and Small Molecule Therapy in the Management of Psoriatic Arthritis

The therapy of psoriatic arthritis (PsA) has blossomed in the past decade. Inhibition of tumor necrosis factor (TNF) has been at the fore of this approach and has paved the way for the investigation of many other potential pro-inflammatory and signaling pathways. Most of the initial studies of TNF inhibitors in PsA have been conducted in specific populations, largely focusing on those with established, peripheral joint disease. That said, in excess of 10 years’ worth of real world clinical experience has led to increased confidence in the wider use of these agents. We are now faced with an exciting time of discovery of many new molecules; these not only include new, large protein biological agents, but also smaller synthetic chemical molecules, many of which can be administered orally. Those currently under development are discussed within this article. Whilst there is scarce data about their real world efficacy and safety profile, it is evident that the therapeutic armamentarium for treating PsA will greatly increase in the foreseeable future and this is anticipated to improve patient outcomes.

Preliminary clinical activity of a topical JAK1/2 inhibitor in the treatment of psoriasis

BACKGROUND

Janus-associated kinases (JAKs) are involved in signal transduction from a variety of cytokines implicated in the pathogenesis of psoriasis, including interleukin (IL)-12, IL-23, and interferon-γ. INCB018424, a small molecule inhibitor of JAK1 and JAK2, inhibits cytokine-induced JAK/signal transducers and activators of transcription signaling and the resultant production of inflammatory proteins (eg, IL-17).

OBJECTIVE

We sought to demonstrate proof of concept in patients with stable plaque psoriasis.

METHODS

Patients were dosed with vehicle, 0.5% or 1.0% INCB018424 phosphate cream once a day or 1.5% twice a day for 28 days. Additional groups included two active comparators (calcipotriene 0.005% cream or betamethasone dipropionate 0.05% cream).

RESULTS

Both the 1% and the 1.5% cream improved lesion thickness, erythema, and scaling and reduced lesion area compared with placebo. A composite lesion score decreased by greater than 50% with the efficacious doses of INCB018424 compared with 32% for vehicle controls. Topical application of INCB018424 was well tolerated with few mild adverse events noted. Mean plasma concentrations of INCB018424 after topical application of 0.5% to 1.5% cream were in the low nanomolar range, representing a fraction (<1%) of the half maximal inhibitory concentration (IC(50)) in whole blood for inhibition of cytokine-stimulated signal transducers and activators of transcription-3 phosphorylation.

LIMITATIONS

This study was limited by the relatively short study duration and small sample size.

CONCLUSION

Topical INCB018424 is safe, is well tolerated, and exhibits clinical activity in the topical treatment of psoriasis.

Enhanced apoptosis-inducing function of MDA-7/IL-24 RGD mutant via the increased adhesion to tumor cells

Melanoma differentiation-associated gene-7 (mda-7)/interleukin-24 (IL-24) has shown potent tumor cell apoptosis inducing capacity in multiple cancers. However, the apoptosis induction capacity of mda-7/IL-24 was low and directly correlated with the adhesion to tumor cells.Cell adhesion molecule integrin α(v)β(3) expressed on the surface of several types of solid tumor cells, and they bind to arginine-glycine-aspartic acid (RGD) which enhanced the adhesion to tumor cells. This rout was exploited to construct a tumor-targeting gene RGD-IL-24 which can express RGD-MDA-7/IL-24 protein that includes the cell adhesive sequence (164)Arg-(165)Gly-(166)Asp (A Glycine residue was inserted into the recombinant MDA-7/IL-24 between Arg164 and Asp165 to form a RGD motif). We successfully got the MDA-7/IL-24 mutant by overlapping polymerase chain reaction (PCR) and evaluated its therapeutic efficacy for tumor cell lines MCF-7, HeLa, HepG2, and normal human lung fibroblast (NHLF) line. And we found that the expression of pCDNA3.1/RGD-IL-24 was same to the expression of pCDNA3.1/IL-24. The RGD-IL-24 enhanced the apoptosis-inducing function in tumor cells, but not in normal cells. In tumor cell lines, the apoptosis-inducing activities of RGD-IL-24 was significantly higher than IL-24 detecting by MTT assay, Annexin V, and Hoechst 33258 analysis. Further, pCDNA3.1/RGD-IL-24 showed a significant increase in the ratio of pro-apoptotic (bax) to anti-apoptotic (bcl-2) proteins in tumor cell lines, but not in NHLF cell line. Together, these results suggest that RGD-IL-24 can enhance the apoptosis of tumor cells and may provide a promising drug in tumor therapy.

Myeloid cells migrate in response to IL-24

IL-24 (melanoma differentiation associated gene 7 product) is a member of the IL-10 cytokine family that has been reported to possess anti-tumor activity. IL-24 is produced by immune tissues and its expression can be induced in human peripheral blood mononuclear cells by pathogen-associated molecules. While immune cells are known to produce IL-24, the response of immune cells to IL-24 is unclear. Using recombinant human IL-24, we demonstrated that IL-24 induces human monocyte and neutrophil migration, in vitro. An in vivo chemotaxis model showed that IL-24 attracted CD11b positive myeloid cells. To further characterize the chemotactic IL-24 response and type(s) of receptor(s) utilized by IL-24, we treated monocytes with signaling pathway inhibitors. IL-24-induced migration was reduced by pertussis toxin treatment, thus implicating G-protein coupled receptors in this process. Additionally, MEK and JAK inhibitors markedly decreased monocyte migration toward IL-24. These results suggest that IL-24 activates several signaling cascades in immune cells eliciting migration of myeloid cells, which may contribute to the known anti-cancer effects of IL-24.

IL-24 transgenic mice: in vivo evidence of overlapping functions for IL-20, IL-22, and IL-24 in the epidermis

IL-20 and IL-24 share two different heterodimeric receptors consisting of either IL-20R1 or IL-22R1 and a common IL-20R2 subunit, whereas IL-22 signals through IL-22R1/IL-10R2. However, until now, only IL-20 and IL-22 have been proven to play important roles in vivo in the epidermis where all four receptor subunits are expressed. In this study, we show that IL-24 transgenic mice manifest many similar phenotypes to that of IL-20 and IL-22, including neonatal lethality, epidermal hyperplasia, and abnormality in keratinocyte differentiation. These results support a largely redundant role in epidermal functions for IL-20, IL-22, and IL-24, which seem to be IL-22R1 dependent. Moreover, we show that IL-24 transgenic mice exhibit infiltrating macrophages in the dermis with concomitant increases in MCP-1 production from both keratinocytes in the epidermis and immune infiltrates in the adjacent dermal layer below. Furthermore, we demonstrate that the homodimeric IL-20R2 soluble receptor is a potent blocker for IL-24 and can be used to further dissect the crosstalk among the IL-20 family of cytokines in normal development as well as in autoimmune diseases.

Interleukin-24 selectively induces growth suppression and apoptosis in human gastric cancer cells transfected with a single tetracycline-regulatable plasmid

AIM: To estimate the tumor-suppressive activity of interleukin-24 (IL-24) in gastric cancer cells in vitro and the regulation of tetracycline in a single plasmid pCEP4-tetR-IL-24.

METHODS: A single plasmid pCEP4-tetR-IL-24 was constructed which contained the TetR and TetO. The cells were transfected with pCEP4-tetR-IL-24 using lipofectamine 2000. The expression of IL-24 was detected by Western blotting. The suppression of cellular growth was determined by MTT assay and trypan blue rejection. The induction of apoptosis was analyzed by Annexin Ⅴ staining.

RESULTS: IL-24 protein was induced to express in gastric cancer cells (MGC803 and BGC823) and normal cells (GES-1) after transfection with pCEP4-tetR-IL-24. In the MGC803 and BGC823 cells, cellular growth was inhibited more efficiently (P < 0.01, 0.001-0.006), and the percentage of apoptosis cells was higher after doxycline induction (23.5%/25.6%→33.8%/36.7%, P < 0.01). However, there were no differences observed in GES-1 cells among the groups (P > 0.05).

CONCLUSION: The plasmid-mediated tranfection of IL-24 selectively induces the suppression of cell growth and apoptosis in gastric cancer cells. Tetracycline can regulate the expression of IL-24 in gastric cancer cells and normal epithelial cells.

IL-24 inhibits the growth of hepatoma cells in vivo

The interleukin (IL)-24/melanoma differentiation associated gene-7 (mda-7) is a member of the IL-10 cytokine family. Introduction of the IL-24 gene into a variety of cancer cells suppresses their growth. It has not been shown, however, whether IL-24 can suppress the growth of hepatoma cells. The purpose of this study was to determine whether the mouse (m)IL-24 gene would suppress hepatoma cells in vivo after being delivered via intramuscular electroporation. After mice were given a subcutaneous dorsal injection of ML-1 hepatoma cells, the mIL-24 gene was delivered and suppressed tumor growth. On day 140, 60% of the mIL-24-treated mice (n=10) and 0% (n=10) of the untreated control mice had survived. We also generated a mouse-hepatoma model by injecting ML-1 cells into the spleen, which resulted in tumor metastasis in the liver. Intramuscular electroporation of mIL-24 also inhibited hepatoma-cell growth in the liver. On day 50, 90% of the experimental mice (n=10) and 40% (n=10) of the control mice had survived. Liver tumors in surviving experimental mice were 50% smaller than those in control mice. IL-24 also inhibited tumor vascularization. These results suggest that IL-24 has potential therapeutic value for hepatoma

Interleukin-24 and its receptors

Interleukin 24 (IL-24) is a new member of the IL-10 family of cytokines and it signals through two heterodimeric receptors: IL-20R1/IL-20R2 and IL-22R1/IL-20R2. Upon binding to its receptors, IL-24 induces rapid activation of Stat-1 and Stat-3 transcription factors, which appear to play a role in cell survival and proliferation. Under physiological conditions, the major sources of IL-24 are the activated monocytes and T helper 2 cells, whereas the major IL-24 target tissues, based on the receptor expression pattern, are non-haematopoietic in origin, and include skin, lung and reproductive tissues. Structurally and functionally, IL-24 is highly conserved across species. This review highlights our current knowledge of IL-24 as a cytokine, with much less emphasis placed on the non-receptor-mediated functions (a subject of several reviews) focused on in much of the earlier literature on IL-24. The potential roles of IL-24 as part of a complex cytokine network in wound healing, psoriasis and cancer are discussed.