(PA-239) Onco-miR-148a Expression and Its Function in Multiple Myeloma

Thursday, September 18, 2025

Asumi Kojima, Clinical Laboratory Technologist

Trainee
Graduate School of Health Sciences, Gunma University

Introduction: MicroRNAs (miRNAs) are a class of short non-coding RNAs that are 19 to 25 nucleotides in length. They play a critical role in the post-transcriptional regulation of gene expression by promoting mRNA degradation and suppressing translation of target mRNAs. Abnormal expressions of miRNAs have been reported in a variety of cancers. Our laboratory has previously studied tumor suppressor miRNAs that are downregulated in multiple myeloma (MM). In this study, we examined the expression and function of oncogenic miRNAs that are upregulated in MM.

Methods:   Small RNA sequencing was used to analyze miRNA expression in 10 consenting MM, 5 MGUS, and 3 controls. We measured selected miRNAs’ expression in CD138-positive plasma cells obtained from 105 MM, 69 MGUS, and 14 controls by RT-qPCR and evaluated changes in cell proliferation upon transfection of the inhibitor or the mimic of the miRNAs in MM cell lines. Altered expression of the miRNAs by transfection of either their inhibitor or mimic was confirmed by RT-qPCR. The mRNA and protein expression levels of target genes were evaluated in MM cell lines transfected with miRNA inhibitor or mimic.

Results:   Among the top 10 differentially expressed miRNAs identified by small RNA sequencing in the comparison of MM and control groups, we selected miR-148a, which was found to be significantly overexpressed in the MM group compared to the control group (p=0.000391). RT-qPCR confirmed that expression levels of both miR-148a-5p and miR-148a-3p were found to be significantly higher in the MM. In vitro, cell proliferation was found to be inhibited by the transfection of a miR-148a-3p inhibitor and promoted by the transfection of its mimic in KMS28BM and KMS27, but not in KMS11 and KMS26. The transfection of the miR-148a-5p inhibitor or mimic did not result in any alterations in cell proliferation. The expression levels of the genes selected as potential targets of the by in silico prediction and the significantly decreased expression in the MM group compared to that in the control group by RNA sequencing and related to tumor suppression were measured using RT-qPCR. A correlation analysis revealed a negative association between the expression of miR-148a-3p and four specific genes (SH2B3, PREX1, PTEN, and CCDC6) in MM cell lines. No substantial alterations in the expression levels of target genes' mRNA and proteins were observed in cell lines that had been transfected with a miR-148a-3p inhibitor or a miR-148a-3p mimic. However, a downward trend in CCDC6 expression was noted in the presence of a miR-148a-3p mimic.

Conclusions:   The expression levels of both miR-148a-3p and miR-148a-5p have been observed to be elevated in MM. The findings of this study suggest that high expression of miR-148a-3p in patients with MM may promote cell proliferation and a tumor suppressor gene CCDC6 is regarded as one of the target genes.