Immune Profile of Mobilized PBSC Predicts Outcomes and t-MN in MM Post-ASCT

Overview

This study evaluated the immune composition of mobilized peripheral blood stem cells (PBSC) in multiple myeloma (MM) patients undergoing autologous stem cell transplantation (ASCT). It identified immune abnormalities in PBSC that correlate with early MM relapse and the development of therapy-related myeloid neoplasms (t-MN), which are linked to poor survival.

Background

Autologous stem cell transplantation combined with maintenance therapy remains a cornerstone treatment for multiple myeloma, improving outcomes but not curing the disease. Relapse and therapy-related myeloid neoplasms (t-MN), occurring in 2–4% of patients, significantly contribute to post-ASCT mortality. The immunosuppressive tumor microenvironment and immune senescence are implicated in treatment resistance and disease progression. Understanding the immune profile of mobilized PBSC may help predict long-term outcomes and risk of t-MN.

Data Highlights

Patients with active MM undergoing ASCT had cryopreserved PBSC analyzed using mass cytometry with 37 lymphoid and myeloid markers. Samples were processed under cGMP conditions and analyzed for immune cell subsets and exhaustion markers. Data normalization and clustering were performed using advanced bioinformatics tools (PhenoGraph, UMAP) to identify immune signatures associated with relapse and t-MN development.

Key Findings

• Mobilized PBSC from MM patients who later relapsed or developed t-MN showed immune abnormalities characterized by reduced immune effector cells (cytotoxic T-cells and NK cells).
• Expansion of immunosuppressive populations such as regulatory T-cells (Tregs) and myeloid-derived suppressor cells (MDSCs) was observed in PBSC linked to poor outcomes.
• Increased expression of exhaustion markers on T-cells in PBSC correlated with early MM relapse and t-MN risk.
• TP53-mutated therapy-related myeloid neoplasms exhibited a highly immunosuppressed milieu, consistent with the PBSC immune profile findings.
• Immune profiling of PBSC prior to ASCT may identify high-risk patients for relapse and t-MN, enabling tailored therapeutic strategies.

Clinical Implications

Immune profiling of mobilized PBSC can serve as a predictive biomarker for MM relapse and t-MN development post-ASCT, facilitating risk stratification. Early identification of patients with immunosuppressive PBSC profiles may guide closer monitoring and consideration of immunomodulatory interventions to improve long-term outcomes. This approach supports personalized treatment planning in MM transplantation protocols.

Conclusion

The immune composition of mobilized PBSC is a critical determinant of post-ASCT outcomes in multiple myeloma, with immunosuppressive features predicting relapse and therapy-related myeloid neoplasms. Integrating immune profiling into clinical practice may enhance prognostication and inform therapeutic decisions.

References

1. Mayo Clinic 2003-2020 -- Immune profile of mobilized PBSC in MM patients