(PA-323) LILRB4 Protects Multiple Myeloma Cells from Ferroptosis to Promote MM Progression

Multiple myeloma (MM) is the second most common hematologic malignancy. Although multiple targets on MM cells are discovered and applied in clinical treatment, relapse is almost inevitable in MM patients. In our previous study, a high-risk cell cluster was found from MM patients with overall survival less than 2 years by single-cell RNA sequencing (scRNA seq). In this specific cluster, LILRB4 a novel biomarker for high-risk myeloma patients, was highly expressed, indicating the critical role of LILRB4 in myelomagenesis and drug resistance. However, the mechanisms of LILRB4 in MM development has not been fully understood. Here, we investigated the role of LILRB4 in tumorigenesis and MM cell proliferation.  

Methods: in results

Results:

Methods and Results

Our clinical data revealed that MM patients with elevated LILRB4 expression had poor prognosis and reduced overall survival, underscoring its potential role in disease progression and drug resistance. In vitro experiment showed that LILRB4-overexpressing (LILRB4-OE) MM cells enhanced the cell colony-forming ability, promoted cell proliferation but not affected cell apoptosis. We used LILRB4-OE MM cells to establish myeloma xenograft model and results showed that mice injected with LILRB4-OE MM cells exhibited accelerated tumor growth and reduced survival compared to those receiving LILRB4-negative cells. Transcriptomic profiling of LILRB4-OE MM cells revealed activation of the NF-κB signaling pathway, consistent with our findings and previous literature. Notably, RNA-seq data also indicated activation of the STAT3 pathway and upregulation of its downstream effector PIM1, suggesting that LILRB4 may drive MM proliferation via the STAT3/PIM1 axis. Importantly, treatment with the PIM inhibitor AZD1208 abrogated the proliferative advantage conferred by LILRB4 overexpression. Interestingly, Gene Ontology (GO) enrichment analysis further revealed that cholesterol and sterol metabolic processes were significantly enriched in LILRB4-OE MM cells, indicating altered lipid homeostasis. Ferroptosis is highly related to lipid metabolism and driven by the lethal lipid peroxidation. Recently, more and more evidence proved that inducing ferroptosis improved the effectiveness of immunotherapy, which may be a potential therapeutic strategy for relapsed patients. Given the established link between lipid metabolism and ferroptosis, we investigated the sensitivity of MM cells to ferroptotic cell death. Treatment with RSL3, a ferroptosis inducer targeting GPX4, resulted in significantly increased cell death in LILRB4-knockout (LILRB4-KO) MM cells, which can be reversed by ferroptosis inhibitor, suggesting that LILRB4 plays a protective role against ferroptosis.

Conclusions:

In conclusion, LILRB4 is highly associated with poor prognosis of MM patients and has the ability of tumorigenesis. LILRB4 promotes MM cell proliferation through STAT3/PIM1 signaling pathway and protects MM cells from ferroptosis, which plays critical roles in MM pathogenesis.