Exosome Mirnas Profiling in Serum and Prognostic Evaluation in Patients with Multiple Myeloma

Objective: Multiple Myeloma (MM) is a hematological malignancy characterized by the clonal expansion of malignant proliferation of plasma cells in the bone marrow. Moreover, the proliferation of MM cells is highly dependent on the BM microenvironment. MicroRNA (MiRNAs) are short, noncoding RNAs that regulate gene expression at the posttranscriptional level. MiRNAs carried by exosomes play pivotal roles in the crosstalk and signal transferring between malignant cells and non-malignant cells, which are involved in the pathogenesis of MM. Here, we investigated the exosome miRNA profiling in peripheral blood serum of MM patients and compared it with healthy donors. Bioinformatics analysis was utilized to clarify the molecular pathways associated with exosome miRNAs via their target genes. Furthermore, a prognostic model based on the top 20 hub genes was constructed in MM.

Methods and materials: The serum samples including 19 newly diagnosed MM patients and 9 healthy donors were analyzed. Exosome in serum was isolated and miRNA profiling was investigated. Differential expression of miRNAs in exosomes was calculated between MM patients and HDs using the edgeR package. STRING and CytoHubba were applied to identify the hub miRNAs and core mRNAs. The exosomal miRNA-mRNA regulatory network was constructed. Functional enrichment of the core target genes was implemented using Metascape. The ESTIMATE immune scores were used to analyze the infiltration levels of immune cells in MM patients with GSE136324. The proportion of 22 tumor-infiltration immune cells in each MM patient was calculated using the CIBERSORT score. Multivariate Cox analysis of hub mRNAs was utilized to construct a novel prognostic model based on the top 20 hub genes.

Results: In the present study, we found 353 differentially expressed exo-miRNAs between MM patients and healthy donors, and 9564 target mRNAs by 353 exo-miRNAs were predicted. GO and KEGG analysis of target mRNAs showed that they were involved in biological processes including proteasome-mediated ubiquitin-dependent protein degradation process. The exosomal miRNA-mRNA regulatory network was constructed and six hub miRNAs were identified. Target genes of these six hub miRNAs and the differential expressed genes (DEG) in Zhan Myeloma were intersected, and 513 DEGs targeted by hub miRNAs were identified. The protein-protein interaction (PPI) network was established in the STRING database. According to module analysis, the top 3 three modules were identified in the PPI network including mRNA splicing, cellular response to stress, and deubiquitination. Moreover, a module related to cytokine-related signaling pathways was enriched as well. Further analysis suggests that Interleukin 6 Signal Transducer (IL6ST), Tyrosine Kinase 2 (TYK2), and Adenosine Deaminase (ADAR) exhibited high correlations with immune scores in MM and were significantly associated with infiltration of CD4 T cell subtypes including follicular helper T cells and CD4 naïve T cells. Taken together, these findings suggested that IL6ST, TYK2, and ADAR might play pivotal roles in tumor immune escape. In addition, the top 20 hub genes were selected from the PPI network. Multivariate Cox regression analysis showed that the 20 hub genes-based signature could be utilized to construct a prognostic model.

Conclusions: In conclusion, our study successfully depicted the exo-miRNA expression profiles in serum exosomes of MM patients and constructed the miRNA-mRNA regulatory network. A novel prognostic model based on 20 hub genes is constructed that facilitates the risk stratification of MM patients with distinct outcomes.

No relevant conflicts of interest to declare.