Myeloma Genomics and Microenvironment and immune profiling

Category: Myeloma Genomics and Microenvironment and immune profiling

CD69+ Bone Marrow-Resident CD8+ T Cells Exhibit Functional Exhaustion and Impaired Anti-Tumor Activity in Multiple Myeloma

(PA-219) CD69+ Bone Marrow-Resident CD8+ T Cells Exhibit Functional Exhaustion and Impaired Anti-Tumor Activity in Multiple Myeloma

Friday, September 19, 2025

Yoon Seok Choi, MD, PhD (he/him/his)

Professor
Korea University College of Medicine

Introduction: Multiple myeloma (MM) is characterized by dysfunctional immune microenvironments in the bone marrow (BM), where tumor-induced T cell exhaustion hinders effective immune surveillance. CD69, a canonical marker of tissue-resident memory T cells (TRM), is constitutively expressed on resident CD8⁺ T cells in various tissues. However, the immunological characteristics and clinical significance of CD69⁺CD8⁺ T cells in the MM bone marrow remain poorly understood.

Methods:   Paired BM and peripheral blood samples were collected from 39 newly diagnosed MM patients. Flow cytometry was used to assess surface and intracellular markers, including exhaustion and cytotoxicity markers. CD69⁺ and CD69^- memory CD8⁺ T cells were sorted from BM and subjected to RNA sequencing and gene set enrichment analysis (GSEA). Functional status was evaluated via intracellular cytokine staining after direct ex vivo stimulation. Antigen-specific CD8⁺ T cells recognizing NY-ESO-1 or HM1.24 were identified using MHC-multimer technique. Correlations with tumor burden (BM plasma cell % and serum β2-microglobulin) were also analyzed.

Results:   BM-resident CD69⁺CD8⁺ T cells were more abundant than their peripheral counterparts and displayed TRM-like transcriptomic profiles, including upregulation of CD69, PDCD1, EOMES, and TOX, and downregulation of S1PR1, GZMB, and GNLY. These cells co-expressed multiple exhaustion markers (PD-1, TIGIT, Lag-3) and showed higher frequencies of terminally exhausted Eomes^hi T-bet^lo phenotypes. Myeloma antigen-specific CD8⁺ T cells were enriched in the CD69⁺ subset and expressed higher levels of PD-1 and TIGIT. The frequency of PD-1⁺ or PD-1⁺TIGIT⁺ among CD69⁺CD8⁺ T cells significantly correlated with BM plasma cell percentage and serum β2-microglobulin level. Functionally, CD69⁺ cells exhibited diminished expression of granzyme B, perforin, TNF-α, and IFN-γ. Notably, co-blockade of PD-1 and TIGIT—but not either alone—restored cytokine production in CD69⁺CD8⁺ T cells ex vivo.

Conclusions:   CD69⁺CD8⁺ T cells in the MM bone marrow represent a distinct tissue-resident and tumor antigen-reactive subset with features of advanced exhaustion and functional impairment. Their phenotype correlates with disease burden, and their function can be partially restored via PD-1/TIGIT dual blockade. These findings support the clinical utility of CD69⁺CD8⁺ T cells as a biomarker for anti-myeloma immune activity and potential therapeutic targets in T cell-based immunotherapy.