Chitinase-3-like protein 1 (CHI3L1) is a secreted glycoprotein that mediates inflammation, macrophage polarization, apoptosis, and carcinogenesis. The expression of CHI3L1 is strongly upregulated by various inflammatory and immunological diseases, including several cancers, Alzheimer’s disease, and atherosclerosis. Several studies have shown that CHI3L1 can be considered as a marker of disease diagnosis, prognosis, disease activity, and severity. In addition, the proinflammatory action of CHI3L1 may be mediated via responses to various proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interferon-γ. Therefore, CHI3L1 may contribute to a vast array of inflammatory diseases. However, its pathophysiological and pharmacological roles in the development of inflammatory diseases remain unclear. In this article, we review recent findings regarding the roles of CHI3L1 in the development of inflammatory diseases and suggest therapeutic approaches that target CHI3L1.

Chitinase 3‐like 1 (Chi3L1) is associated with various biological processes, such as inflammation, tissue repair, proliferation, cell survival, invasion, and extracellular matrix remodeling. Recent studies indicated that Chi3L1 is critical for cancer development and metastasis. In this study, we demonstrate that Chi3L1 serum and tissue levels were significantly increased in lung cancer patients compared with controls. We previously developed an anti‐Chi3L1‐humanized antibody, and here, we investigate its antitumor and antimetastatic effect. The anti‐Chi3L1 antibody attenuated tumor growth and metastasis both in vitro and in vivo in a lung cancer mouse model. These inhibitory effects are associated with signal transducer and activator of transcription 6 (STAT6)‐dependent M2 polarization inhibition. Proteomics analysis revealed that plasminogen (PLG) interacts with Chi3L1 and affects M2 polarization. Chi3L1 plays a critical role in lung cancer progression, and the anti‐Chi3L1 antibody could be a new anticancer therapy.

In oriental medicine, bee venom has long been used as a therapeutic agent against inflammatory diseases. Several studies have reported that isolated and purified bee venom components are effective in treating dementia, arthritis, inflammation, bacterial infections, and cancer. In previous studies, we reported that bee venom inhibits cell growth and induces apoptotic cell death in lung cancer cells. In the present study, we assessed whether bee venom affects autophagy and thereby induces apoptosis. Bee venom treatment increased the levels of autophagy-related proteins (Atg5, Beclin-1, and LC3-II) and the accumulation of LC3 puncta. We found that bee venom could induce autophagy by inhibiting the mTOR signaling pathway. In addition, we found that hydroxychloroquine (HCQ)- or si-ATG5-induced autophagy inhibition further demoted bee venom-induced apoptosis. Bee venom-induced autophagy promotes apoptosis in lung cancer cells and may become a new approach to cancer treatment.

Our previous big data analyses reported a strong association between CHI3L1 expression and lung tumor development. In this present study, we investigated whether a CHI3L1-inhibiting natural compound, ebractenoid F, inhibits lung cancer cell growth and migration and induces apoptosis. Ebractenoid F concentration-dependently (0, 17, 35, 70 µM) and significantly inhibited the proliferation and migration of A549 and H460 lung cancer cells and induced apoptosis. In the mechanism study, we found that ebractenoid F bound to CHI3L1 and suppressed CHI3L1-associated AKT signaling. Combined treatment with an AKT inhibitor, LY294002, and ebractenoid F synergistically decreased the expression of CHI3L1. Moreover, the combination treatment further inhibited the growth and migration of lung cancer cells and further induced apoptosis, as well as the expression levels of apoptosis-related proteins. Thus, our data demonstrate that ebractenoid F may serve as a potential anti-lung cancer compound targeting CHI3L1-associated AKT signaling.

EMBO Press is an editorially independent publishing platform for the development of EMBO scientific publications.

Background and Purpose: Chitinase‐3‐like 1 (CHI3L1) causes skin inflammation in the progression of atopic dermatitis. We investigated if anti‐CHI3L1 antibody could prevent the development of atopic dermatitis and its mechanisms of action.Experimental Approach: The effect of CHI3L1 antibody on phthalic anhydride‐induced atopic dermatitis animal model and in vitro reconstructed human skin (RHS) model were investigated. Expression and release of atopic dermatitis‐related cytokines were determined using an enzyme‐linked immunosorbent assay, and RT‐qPCR, STAT3 and CXCL8 signalling were measured by western blotting.Key Results: Anti‐CHI3L1 antibody suppressed phthalic anhydride‐induced epidermal thickening, clinical score, IgE level and infiltration of inflammatory cells, and reduced phthalic anhydride‐induced inflammatory cytokines concentration. In addition, CHI3L1 antibody treatment inhibited the expression of STAT3 activity in phthalic anhydride‐treated skin. It was also confirmed that CHI3L1 antibody treatment alleviated atopic dermatitis‐related inflammation in the RHS model. The inhibitory effects of CHI3L1 antibody was similar or more effective compared with that of the IL‐4 antibody. We further found that CHI3L1 is associated with CXCL8 by protein‐association network analysis. siRNA of CHI3L1 blocked the mRNA levels of CHI3L1, IL‐1β, IL‐4, CXCL8, TSLP, and the expression of CHI3L1 and p‐STAT, and the level of CXCL8, whereas recombinant level of CXCL8 was elevated. Moreover, siRNA of STAT3 reduced the mRNA level of these cytokines. CHI3L1 and p‐STAT3 expression correlated with the reduced CXCL8 level in the RHS in vitro model.Conclusion and Implications: Our data demonstrated that CHI3L1 antibody could be a promising effective therapeutic drug for atopic dermatitis.