CCRL2 promotes antitumor T-cell immunity via amplifying TLR4-mediated immunostimulatory macrophage activation

Menée à l'aide de modèles murins de mélanome, cette étude met en évidence un mécanisme par lequel le récepteur CCRL2 favorise la réponse antitumorale des lymphocytes T via l'amplification de l'activation des macrophages immunostimulateurs induite par le récepteur TLR4

Résumé en anglais

Macrophages play a key role in shaping tumor immunity. CCRL2 was originally cloned from LPS-stimulated macrophages; however, whether CCRL2 influences tumor immunity by regulating macrophage function remains unknown. In this study, we identify CCRL2 as a predictive indicator of robust antitumor immunity in human cancers and report the predominant expression of CCLR2 in TAM with immunostimulatory phenotypes. We also reveal the functional role of CCRL2 in potentiating antitumor immunity. Specifically, CCRL2 that is primarily induced by TLR4 agonists in turn interacts with TLR4 to facilitate its retainment in cell surface, thereby amplifying membrane TLR4-mediated downstream inflammatory signaling, finally leading to optimal activation of immunostimulatory macrophages and subsequent antitumor CD8+ T-cell responses.Macrophages are the key regulator of T-cell responses depending on their activation state. C-C motif chemokine receptor-like 2 (CCRL2), a nonsignaling atypical receptor originally cloned from LPS-activated macrophages, has recently been shown to regulate immune responses under several inflammatory conditions. However, whether CCRL2 influences macrophage function and regulates tumor immunity remains unknown. Here, we found that tumoral CCRL2 expression is a predictive indicator of robust antitumor T-cell responses in human cancers. CCRL2 is selectively expressed in tumor-associated macrophages (TAM) with immunostimulatory phenotype in humans and mice. Conditioned media from tumor cells could induce CCRL2 expression in macrophages primarily via TLR4, which is negated by immunosuppressive factors. Ccrl2−/− mice exhibit accelerated melanoma growth and impaired antitumor immunity characterized by significant reductions in immunostimulatory macrophages and T-cell responses in tumor. Depletion of CD8+ T cells or macrophages eliminates the difference in tumor growth between WT and Ccrl2−/− mice. Moreover, CCRL2 deficiency impairs immunogenic activation of macrophages, resulting in attenuated antitumor T-cell responses and aggravated tumor growth in a coinjection tumor model. Mechanically, CCRL2 interacts with TLR4 on the cell surface to retain membrane TLR4 expression and further enhance its downstream Myd88-NF-κB inflammatory signaling in macrophages. Similarly, Tlr4−/− mice exhibit reduced CCRL2 expression in TAM and accelerated melanoma growth. Collectively, our study reveals a functional role of CCRL2 in activating immunostimulatory macrophages, thereby potentiating antitumor T-cell response and tumor rejection, and suggests CCLR2 as a potential biomarker candidate and therapeutic target for cancer immunotherapy.All study data are included in the article and/or SI Appendix.