(PA-281) LILRB4 Drives Daratumumab Resistance in Multiple Myeloma via STAT3/PIM1 Activation and Lipid Metabolic Reprogramming of the Immune Microenvironment

Multiple myeloma (MM), characterized by malignant proliferation of plasma cells, remains an incurable hematologic malignancy despite therapeutic advancements. The introduction of anti-CD38 mABs like daratumumab (Dara) has significantly improved clinical outcomes. However, drug resistance and relapse remain major clinical challenges, with the underlying mechanisms being not fully understood. Exploring resistance mechanisms and identifying sensitization strategies are critical priorities in current research.

Methods:

Single-cell RNA sequencing (ScRNA-seq) was performed on CD138⁺ tumor cells from Dara-resistant MM patients. Lentiviral transduction generated isogenic MM cell lines with leukocyte immunoglobulin-like receptor B4 (LILRB4) overexpression (OE) or CRISPR/Cas9-mediated knockout (KO).

Results:

ScRNA-seq data derived from Dara resistant patients to revealed a significantly elevated expression of LILRB4 in the residual resistant tumor cells. However, Flow cytometry analysis indicated that alterations in LILRB4 expression did not significantly affect the expression of CD38. This finding suggests that LILRB4 mediates resistance is independent of target antigen regulation. Subsequent Transcriptomics demonstrated that LILRB4 upregulates the STAT3/ proviral integration site for PIM1 pathway at the transcriptional level. High PIM1 expression not only promotes the proliferation of MM cells but also enhances the resistance of tumor cells to natural killer (NK) cell-mediated cytotoxicity by suppressing pro-apoptotic signals. In clinical cohorts, patients with high PIM1 expression exhibited significantly shorter overall survive. Mechanistically, gene set enrichment analysis (GSEA) indicated that LILRB4 OE activates the cholesterol synthesis pathway. Moreover, we observed that LILRB4 significantly regulates intracellular protein acetylation. These findings indicate that LILRB4 might modulate lipid metabolism to exert an impact on acetyl-CoA supply. Consequently, this activates the STAT3 pathway and upregulates the expression of downstream PIM1. Further investigations have demonstrated that LILRB4 is capable of reshaping the immune microenvironment through the regulation of tumor cell lipid metabolism. Specifically, overexpression of LILRB4 in MM cells leads to an increase in lipid secretion. This, in turn, suppresses the activity and cytokine release of NK cells within the microenvironment. This immunosuppressive effect synergizes with the upregulation of PIM1 to establish a dual "metabolic-immune" resistance barrier. PIM1 directly promotes tumor survival, while abnormal lipid metabolism impairs the function of immune cells, indirectly reducing Dara Antibody-dependent cellular cytotoxicity (ADCC).

Conclusions:

Our findings show LILRB4 is a master regulator of Dara resistance via STAT3/PIM-mediated proliferation and lipid-driven NK cell dysfunction. Co-targeting this axis with PIM inhibitors and lipid metabolism modulators may overcome resistance, guiding precision immunotherapy in MM.