P-081: A novel circulating miRNA involved in T cell senescence of multiple myeloma patients

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<h3>Background</h3> Many circulating miRNAs were reported as biomarkers of multiple myeloma (MM),but the functions of these circulating miRNAs are not clarified recently. The aim of this work is to identify novel biomarkers of circulating miRNAs in diagnosis and prognosis for MM and reveal their function in the pathogenesis of MM. <h3>Methods</h3> MiRNAs profiling in serum(n=15) and MM cells(CD138+, n=10) were analyzed by RNA-sequencing of MM patients. The common dysregulated miRNAs(P<0.05) were identified via Veen Diagram analysis in serum and MM cells between MM patients and healthy donors, then validated by RT-PCR. ROC analysis and Kaplan-Meier(K-M) analysis were performed to evaluate the differently expressed circulating miRNAs in diagnosis and prognosis in MM patients, respectively. Exosomes of serum were isolated and characterized by dynamic light scattering, transmission microscopy, and western blot analysis. <h3>Results</h3> There were stable and specific miRNA expression profiles in serum and tumor cells of MM patients. The miRNA profiling of MM serum showed that there were 74 differential circulating miRNAs(P<0.05), among which 56 miRNAs(75.7%) were down-regulated and 18 miRNAs were up-regulated(24.3%). MiRNA profiling of MM cells showed that there were 376 miRNAs differentially expressed(P<0.05), of which 87(23.1%) were down-regulated and 289(76.9%) were up-regulated. Veen analysis found 36 common dysregulated miRNAs both in serum and tumor cells of MM. There were 22.3% of differential miRNAs located on chromosome 1 and 17. Five circulating miRNAs(miR-27b-3p, miR-145-3p, miR-628-3p, miR-342-5p and miR-30e-3p) were further confirmed differentially expressed in MM patients(n=201) by RT-PCR. K-M analysis showed that MM patients with low level of miR-27b, miR-145, and miR-628 had shortened PFS and OS. Strikingly, comparing to the decreased level of miR-27b in MM patients serum, miR-27b was enriched in the exosome of serum. MM patients with low level of serum miR-27b displayed lower CD3+T cells and CD3+CD4+T cells in peripheral blood. Our further study found increased proportation of senescent T cells in MM patients with low level of serum miR-27b, especially in CD8+T cells. In order to confirm T cell senescent phenotype, PBMCs were co-cultured with MM patients serum exosomes which mimic the in vivo situation. Flow cytometry analysis showed the CD28 expression was notably decreased on the CD3+ T cells in the co-culture group. In addition, RT-PCR and flow cytometry analysis showed that overexpression of miR-27b significantly down-regulated the level of CD28 in jurkat cells, a T cell line. These findings suggested an immune suppressive microenvironment in MM patients with lower level of serum miR-27b. <h3>Conclusion</h3> Circulating miRNA works as a usful biomarker in diagnosis and prognosis of MM. Strigently, serum miR-27b is a novel circulating miRNA involved in T cell senescence of multiple myeloma patients which indicated the poor outcome of patients with MM.