CD4 Cytotoxic T Cells Promote Antitumor Immunity in Multiple Myeloma

• Published in: Blood 2024-11, Vol.144, p.668-668
• Main Authors: Kim, Sojeong, Kwak, Jeong-Eun, Koh, June-Young, Kook, Hye Won, Kim, Yu Ri, Kim, Soo Jeong, Kim, Jin Seok, Cheong, June-Won, Lee, Min Goo, Lee, Hoyoung, Shin, Eui-Cheol, Kim, Kihyun, Chung, Haerim, Choi, Il-Kyu, Lee, Jeong Seok, Cho, Hyunsoo
• Format: Article
• Language: English
• ISSN: 0006-4971
• DOI: 10.1182/blood-2024-199396

Background: Recent advancements in single-cell RNA sequencing have enhanced our understanding of the immunological dysfunctions during multiple myeloma (MM) progression from monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM). Immunotherapies employing T cells have demonstrated promise in treating MM. However, a better understanding of effector T cells is necessary due to their limited response durability. While most forms of cancer immunotherapy have primarily focused on CD8+ cytotoxic T lymphocytes (CTLs), CD4+ T cells are emerging as important contributors to antitumor responses beyond their traditional roles as helpers or regulators. However, the specific subset of CD4+ T cells contributing to beneficial outcomes in MM remains unclear, and it is unknown whether CD4+ T cells mediate direct antitumor effector functions against myeloma cells. Aims: This study aims to characterize CD4+ CTLs in MM by investigating their phenotypic and functional properties, assessing their impact on patient outcomes, and identifying their mechanisms and therapeutic potential. Methods: We performed scRNA-seq and TCR-seq on CD4+ T cells sorted from bone marrow (BM) aspirates of 29 individuals across different stages of myeloma, including healthy donors (n=5) and patients with MGUS (n=4), SMM (n=4), and MM (n=16). We validated the identified subsets and further characterize their immunophenotype by multicolor flow cytometry, while cytotoxicity assays and blocking experiments evaluated their cytotoxic capabilities. Results: Droplet-based scRNA-seq and paired scTCR-seq were performed to infer the functional states of BM CD4+ T cells, and a total of 105,398 CD4+ T cells were obtained from 29 individuals using the 10X Genomic platform. By unsupervised clustering, we identified 14 distinct BM CD4+ T cell subsets: naive (CCR7+TCF7+FAS-HNRNPLL-), early activated (early.act, CCR7+TCF7+FAS-NR4A1+), central memory (CM, CCR7+FAS+), follicular helper T (Tfh, CXCR5+BCL6+), Th2 (GATA3+CCR4+), Th17 (RORC+CCR6+), Th1 (TBX21+CXCR3+IFNG+), two subsets of regulatory T cells (Treg, FOXP3+CTLA4+), resting Tregs (rTreg, CCR7+) and activated Treg (aTreg, HLA-DRA+TNFRSF9+), IFN-stimulated genes-enriched (ISGshi, OAS3+IRF7+), and activated and proliferating (act.proli, MKI67+CD38+). Of note, we identified two distinct states of BM CD4+ T subsets that highly express cytolytic effector molecules: cells expressing GZMB and cells expressing GZMK. The GZMB-expressing subset ex