LILRB4 represents a promising target for immunotherapy by dual targeting tumor cells and myeloid-derived suppressive cells in multiple myeloma

Multiple myeloma (MM) remains an incurable hematological malignancy. Despite tremendous advances in the treatment, about 10% of patients still have very poor outcomes with median overall survival less than 24 months. Our study aimed to underscore the critical mechanisms pertaining to the rapid disease progression and provide novel therapeutic selection for these ultra-high-risk patients. We utilized single-cell transcriptomic sequencing to dissect the characteristic bone marrow niche of patients with survival of less than two years (EM24). Notably, an enrichment of LILRB4high pre-matured plasma-cell cluster was observed in the patients in EM24 compared to patients with durable remission. This cluster exhibited aggressive proliferation and drug-resistance phenotype. High-level LILRB4 promoted MM clonogenicity and progression. Clinically, high expression of LILRB4 was correlated with poor prognosis in both newly diagnosed MM patients and relapsed/refractory MM patients. The ATAC-seq analysis identified that high chromosomal accessibility caused the elevation of LILRB4 on MM cells. CRISPR-Cas9 deletion of LILRB4 alleviated the growth of MM cells, inhibited the immunosuppressive function of MDSCs, and further rescued T cell dysfunction in MM microenvironment. The more infiltration of myeloid-derived suppressive cells (MDSCs) was observed in EM24 patients as well. Therefore, we innovatively generated a TCR-based chimeric antigen receptor (CAR) T cell, LILRB4-STAR-T. Cytotoxicity experiment demonstrated that LILRB4-STAR-T cells efficaciously eliminated tumor cells and impeded MDSCs function. In conclusion, our study elucidates that LILRB4 is an ideal biomarker and promising immunotherapy target for high-risk MM. LILRB4-STAR-T cell immunotherapy is promising against tumor cells and immunosuppressive tumor microenvironment in MM.