Modulation of infiltrating CD206-positive macrophages restricts progression of pulmonary lymphangioleiomyomatosis (LAM).

RATIONALE Lymphangioleiomyomatosis (LAM) is a low-grade neoplasm caused by the proliferation of tuberous sclerosis complex (TSC)1 or TSC2-deficient LAM cells, resulting in progressive cystic lung disease. The currently approved treatment for LAM delays disease progression but the disease recurs if treatment is discontinued. Therefore, new therapeutic targets and/or strategies are necessary for a cure. Immunosuppressive M2-like macrophages are involved in the progression of various cancers, but their role in the pathophysiology of LAM and as a putative therapeutic target is unknown. METHODS To identify the different immune cells populations involved in LAM, we generated a single-cell transcriptomic map of pulmonary LAM. Interactions between macrophages and LAM cells were studied using the Visium spatial transcriptomic platform and immunofluorescence staining on human pulmonary LAM specimens. Direct co-culture models were used to characterize the influence of TSC2-deficient cells on macrophage differentiation. The efficacy of targeting M2-like macrophages was assessed in preclinical mouse models of TSC2-deficient subcutaneous tumors treated with RP-182, a synthetic peptide which reprograms macrophages towards an anti-tumor M1-like phenotype. RESULTS Single-cell RNA-seq analysis revealed that the majority of macrophages in pulmonary LAM display immunosuppressive markers, including CD206/MRC1 and CD163. Spatial transcriptomic and immunofluorescence analyses showed that M2 macrophages are in close proximity to LAM cells and that LAM cells which are in close proximity to macrophages highly express macrophage homing factor chemokine ligand CXCL12. In vitro, co-culture of human and mouse macrophages with TSC2-deficient cells resulted in the upregulation of M2 markers expressed macrophages. Targeting M2 macrophages via treatment with the CD206 modulator RP-182 impaired the growth of TSC2-deficient tumors in vivo. CONCLUSION LAM cells recruit and polarize macrophages towards an M2 phenotype. M2-like CD206high macrophages may represent a potential therapeutic target in LAM.