Myeloma Genomics and Microenvironment and immune profiling

Category: Myeloma Genomics and Microenvironment and immune profiling

NAMPT in Myeloma-Associated Macrophages Drives Drug Resistance through Mitochondrial Metabolic Reprogramming and Immune Evasion via the SIRT1/STAT3/SPP1 Axis

(PA-278) NAMPT in Myeloma-Associated Macrophages Drives Drug Resistance through Mitochondrial Metabolic Reprogramming and Immune Evasion via the SIRT1/STAT3/SPP1 Axis

Thursday, September 18, 2025

Shunnan Yao

MD
Bone Marrow Transplantation Center, The First Affiliated Hospital, School of Medicine, Zhejiang University

Introduction: The immunosuppressive microenvironment remains a major challenge in multiple myeloma (MM) treatment. As key participants, the role of myeloma-associated macrophages (mMΦs) is still unclear. Nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD+ salvage pathway, is overexpressed in various cancers and immune cells. Through sc-RNA seq analysis, we identified a subset of macrophages with high NAMPT expression associated with MM progression and contributed to drug resistance and immune evasion. This study further investigated the regulatory role of NAMPT in mMΦs.

Methods: n/a

Results: NAMPT knockdown (KD) or inhibition with FK866 reprogrammed mMΦs toward an M1-like phenotype, characterized by decreased M2 markers (CD163, CD206) and increased M1 markers (CD80, CD86) and pro-inflammatory cytokines (IL-1β, IL-6). In co-culture experiments, NAMPT-deficient mMΦs significantly enhanced bortezomib (Bor)-induced apoptosis of H929 and JJN3 cells compared to controls. Intratumoral injection of NAMPT-KD or FK866-inhibited mMΦs attenuated tumor growth and restored Bor sensitivity in xenograft NCG mice. Supplement of NAMPT catalytic product NMN reversed these effects in vitro and in vivo, confirming the essential role of NAMPT in macrophage-mediated drug resistance. Mechanistically, NAMPT maintained mitochondrial homeostasis by preserving NAD+ pools and redox balance (NAD+/NADH ratio). NAMPT depletion triggered mitochondrial dysfunction, evidenced by (1) reduced ATP production and oxygen consumption rate (OCR); (2) collapsed membrane potential measured by JC-1 staining; and (3) abnormal mitochondrial morphology, such as lost and whorled cristae by TEM. Beyond cell-intrinsic effects, NAMPT^-himMΦs suppressed T cell function. NAMPT-deficient mMΦs reinvigorated CD8+ T cell function, boosting IFN-γ and granzyme B expression while reducing exhaustion markers (TIM-3, LAG-3). Transcriptomics and functional validation identified SPP1 as NAMPT downstream target of NAMPT. SPP1-deficient mMΦs similarly enhanced T cell cytotoxicity, but these effects were insensitive to NMN supplementation. Further mechanistic studies revealed that NAMPT sustains SIRT1 activity through NAD+ maintenance. Using Co-IP and ChIP assays, we demonstrated that SIRT1-mediated deacetylation enhanced STAT3 binding to the SPP1 promoter, driving its transcriptional activation. This NAMPT-NAD+-SIRT1-STAT3-SPP1 axis ultimately enabled mMΦs to suppress T cells and promote MM progression.

Conclusions: Our study identified NAMPT^-himMΦs as key drivers of multiple myeloma progression, orchestrating both drug resistance and immune evasion. Targeting NAMPT reprogrammed macrophages toward a M1-like phenotype, enhanced bortezomib sensitivity by disrupting mitochondrial homeostasis, and restored CD8+ T cell function through the NAD+-SIRT1-STAT3-SPP1 axis.