Poster Presentation 37th Lorne Cancer Conference 2025

Single-cell ligand-receptor analysis reveals dormant myeloma cell control pathways in the skeleton (#130)

Alexander Corr 1 , Ryan Chai 1 2 , Weng Hua Khoo 1 2 , Betty Gration 1 3 , James T Smith 1 , Holly Ahel 4 , John Moore 2 3 , Georgia McCaughan 2 3 4 , Tri G Phan 2 4 , Peter I Croucher 1 2
  1. Bone Biology Group, Cancer Plasticity and Dormancy Program, Garvan Institute of Medical Research, Sydney, NSW, Australia
  2. School of Clinical Medicine, Faculty of Medicine and Health, UNSW, Sydney, NSW, Australia
  3. Department of Haematology, St Vincent's Hospital, Sydney, NSW, Australia
  4. Intravital Microscopy Group, Precision Immunology, Garvan Institute of Medical Research, Sydney, NSW, Australia

Background: Multiple myeloma is a haematological cancer characterised by clonal proliferation of malignant plasma cells in the skeleton. Despite therapeutic advances, myeloma remains incurable and patients inevitably relapse. One source of relapse is survival and reactivation of dormant myeloma cells in specialised niches on the endosteal bone surface1. However, mechanisms controlling dormancy in this site remain poorly defined. We hypothesised that single-cell RNA sequencing of dormant myeloma cells and their microenvironment would uncover cell types and molecular pathways controlling dormancy in bone.

Methods: Using the 5TGM1 myeloma mouse model, dormant and reactivated myeloma cells were isolated and single-cell sequenced. In parallel, we sequenced cells isolated from the bone microenvironment comprising endosteal and marrow compartments of mouse femora. Using these datasets, we implemented a ligand-receptor analysis to predict microenvironment crosstalk with dormant myeloma cells.

Single-cell sequencing was also performed on bone marrow aspirate and trephine bone core biopsies from myeloma patients. Myeloma cells were explored for the presence of cells in dormancy, whereas microenvironment cells were leveraged to predict components of the dormant cell niche using ligand-receptor analysis.

Results: Analysis of 5TGM1 myeloma cells defined 1088 genes differentially expressed by dormant cells. Ligand-receptor analysis with 133,942 bone microenvironment cells identified endosteal Cxcl12high-Leprhigh mesenchymal stromal cells (MSCs) as most enriched for dormant cell interaction genes (p value: 7.6x10-9). The top-ranking predicted interaction was MSC-derived Gas6 binding to the receptor Axl on dormant myeloma cells. In a previous study, inhibiting GAS6-AXL in vivo was found to release myeloma cells from dormancy and increase tumour burden2.

Interrogating patient biopsy datasets revealed a putative dormant myeloma cell population enriched for gene markers of mouse dormant myeloma cells (2.3x10-10). This population comprised a 30-fold greater proportion of trephine samples compared to aspirates, indicating bone surface localisation. Ligand-receptor analysis with 83,582 bone microenvironment cells identified CXCL12high-LEPRhigh MSCs and SPP1high-BGLAPhigh preosteoblasts as most enriched for dormant cell interaction genes (4.9x10-25, 5.1x10-29).

Conclusion: Together, these data identified MSCs as regulators of dormant myeloma cells on the endosteal surface and uncovered molecular candidates to prevent patient relapse.

  1. Lawson, M. A., McDonald, M. M., Kovacic, N., Hua Khoo, W., Terry, R. L., Down, J., Kaplan, W., Paton-Hough, J., Fellows, C., Pettitt, J. A., Neil Dear, T., Van Valckenborgh, E., Baldock, P. A., Rogers, M. J., Eaton, C. L., Vanderkerken, K., Pettit, A. R., Quinn, J. M., Zannettino, A. C., Phan, T. G., … Croucher, P. I. (2015). Osteoclasts control reactivation of dormant myeloma cells by remodelling the endosteal niche. Nature communications, 6, 8983. https://doi.org/10.1038/ncomms9983
  2. Khoo, W. H., Ledergor, G., Weiner, A., Roden, D. L., Terry, R. L., McDonald, M. M., Chai, R. C., De Veirman, K., Owen, K. L., Opperman, K. S., Vandyke, K., Clark, J. R., Seckinger, A., Kovacic, N., Nguyen, A., Mohanty, S. T., Pettitt, J. A., Xiao, Y., Corr, A. P., Seeliger, C., … Croucher, P. I. (2019). A niche-dependent myeloid transcriptome signature defines dormant myeloma cells. Blood, 134(1), 30–43. https://doi.org/10.1182/blood.2018880930