Exploring LAG-3 Expression in Multiple Myeloma Patients Following Autologous Stem Cell Transplant
Authors: Fabienne Lucas , Pennell Michael , Benson Don M. , Efebera Yvonne , Chaudhry Maria , Woyach Jennifer A. , Guan Xiangnan , Suohui Zhang , Burd Christin E , Rosko Ashley E. 
Published: October 2019

Abstract
Background: Multiple Myeloma (MM) is associated with T-cell dysfunction. MM-related T-cell deficiencies are reported as both quantitative and qualitative defects with variable functional abnormalities. The clinical significance of these T-cell abnormalities in MM is not fully characterized. Furthermore, the impact of Autologous Stem Cell Transplant (ASCT) on T-cell subsets and immune checkpoint molecules, including PD-L1, PD-1, BLIMP-1, CTLA-4/CD28, TIM-3, and LAG-3, is being explored. Here we examined these features along with other mRNA markers of cellular senescence, immunosenescence, and exhaustion in MM patients pre- and post-ASCT. These studies aimed to improve understanding of the immunologic changes in MM and relationship to disease progression. Evaluating T-cell immune reconstitution post-transplant is invaluable for future therapies to identify targets or stimulate T-cell response to mitigate relapse.
Methods: 100 MM patients were prospectively enrolled in a longitudinal study prior to ASCT for analysis of clinical and biologic factors related to clinical outcomes and event free survival (EFS) post-transplant. Paired peripheral blood T-cells (PBTL) were analyzed (n=31) before ASCT and 90 days post-ASCT. PBTL mRNA targets were anayzed using a custom Nanostring platform (OSU_Senescence) evaluating markers of cellular senescence, immunosenescence, and exhaustion. T-cell populations and subsets were further characterized by flow cytometry pre- and post-ASCT in 20 representative trial patients and 10 age- and sex-matched controls. Serum samples were analyzed for soluble ligands using Luminix MAGPIX multiplex analysis.
Results: Increased PBTL LAG-3 mRNA expression at 90 days post-ASCT was significantly associated with EFS, HR 5.44 (95%CI 1.92-15.46, p=0.001, adjusted p* controlling for false discovery rate=0.038). When adjusted for age, a similar relationship of increased PBTL LAG-3 mRNA expression and EFS was found, HR 5.66 (95%CI 1.83-17.47, p=0.003, p*=0.056). No relationship was observed between other mRNA markers of immunosenesence or exhaustion and EFS. Flow cytometric analysis of post-transplant PBTLs revealed an inverted CD4:CD8 ratio, reduced CD28 expression on CD8+ T-cells, and increased levels of CD4+ T-regulatory cells. LAG-3 expression was significantly increased in CD4+ T-cells post-ASCT, predominately in the CD4 naïve and central memory subsets. Soluble LAG-3 (sLAG3) serum concentrations were similar pre- and post-ASCT, and in comparison to controls.
Conclusions: We found increased expression of Lymphocyte-Activation Gene, LAG-3 (CD223), on CD4+T-cells post-ASCT. PBTL LAG-3 mRNA expression 90 days post-ASCT was associated with EFS and may serve as an early indicator of adverse outcomes. LAG-3 is expressed on activated T-cells and modulates T-cell expansion and function. Future studies targeting the LAG-3 pathway are warranted to restore T-cell dysfunction and augment immunity in MM.
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Disclosures
No relevant conflicts of interest to declare.