T Cell Transcriptional Profiling and Immunophenotyping Uncover LAG3 as a Potential Significant Target of Immune Modulation in Multiple Myeloma

ABSTRACT Autologous Stem Cell Transplant (ASCT) is the standard of care for patients with multiple myeloma (MM). The clinical significance of peripheral blood T-lymphocyte (PBTL) immunologic changes associated with ASCT is poorly understood. Here we evaluated T-cell transcriptional mRNA profiles and immunophenotypes to correlate immunologic senescence, exhaustion, and anergy with clinical endpoints in a cohort of MM patients undergoing ASCT. ASCT induced global transcriptional T-cell changes and altered molecular levels of markers of T-cell subtypes, T-cell activation and exhaustion. These included reduced CD4:CD8 ratio, skewing towards the Th-1 subset, reduced expression of co-stimulatory receptors CD27 and CD28, heightened T-cell activation, and increased expression of immune modulatory molecules LAG3 and PD1. Multicolor flow cytometry experiments confirmed altered circulating CD4 and CD8 subsets and skewing towards differentiated effector cells. Moreover, ASCT promoted an exhausted immunophenotype in CD3+CD4+ subsets and a senescent immunophenotype in CD3+CD8+ subsets. Subset-specific altered expression was also seen for surface molecules with immune modulatory function. ASCT affected soluble levels of molecules with immunomodulatory function by increasing plasma HVEM and TIM3. High molecular LAG3 level was associated with inferior EFS post-ASCT (HR=5.44, CI 1.92-15.46, p=0.001, adjusted p (controlling for false discovery rate) =0.038). Using a comprehensive evaluation of PBTL on a molecular and phenotypic level, we have identified that ASCT induces global T-cell alterations with CD4 and CD8 subset-specific changes. Moreover, LAG3 emerged as an early biomarker of adverse events post-ASCT. These findings will support the development of treatment strategies targeting immune defects in MM to augment or restore T-cell responses.