AUTHOR=Bhavsar Swapnil Parashram , Olsen Lotte , Løkke Cecilie , Koster Jan , Flægstad Trond , Einvik Christer 

TITLE=Hsa-miR-323a-3p functions as a tumor suppressor and targets STAT3 in neuroblastoma cells

JOURNAL=Frontiers in Pediatrics

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/pediatrics/articles/10.3389/fped.2023.1098999

DOI=10.3389/fped.2023.1098999

ISSN=2296-2360

ABSTRACT=<sec><title>Background</title><p>Studies conducted in the last decades have revealed a role for the non-coding microRNAs (miRNAs) in cancer development and progression. Several miRNAs within the chromosome region 14q32, a region commonly deleted in cancers, are associated with poor clinical outcome in the childhood cancer neuroblastoma. We have previously identified <italic>miR-323a-3p</italic> from this region to be downregulated in chemotherapy treated neuroblastoma cells compared to pre-treatment cells from the same patients. Furthermore, in neuroblastoma tumors, this miRNA is downregulated in advanced stage 4 disease compared to stage 1–2. In this study, we attempt to delineate the unknown functional roles of <italic>miR-323a-3p</italic> in neuroblastoma.</p></sec><sec><title>Methods</title><p>Synthetic miRNA mimics were used to overexpress <italic>miR-323a-3p</italic> in neuroblastoma cell lines. To investigate the functional roles of <italic>miR-323a-3p,</italic> cell viability assay, flow cytometry, reverse transcription-quantitative polymerase chain reaction, luciferase reporter assay and western blot were conducted on the neuroblastoma cell lines Kelly, SH-SY5Y and SK-N-BE(2)-C.</p></sec><sec><title>Results</title><p>Ectopic expression of <italic>miR-323a-3p</italic> resulted in marked reduction of cell viability in Kelly, SH-SY5Y and SK-N-BE(2)-C by causing G1-cell cycle arrest in Kelly and SH-SY5Y and apoptosis in all the cell lines tested. Furthermore, mRNA and protein levels of signal transducer and activator of transcription 3 (<italic>STAT3</italic>) were reduced upon <italic>miR-323a-3p</italic> overexpression. A direct binding of the <italic>miR-323a-3p</italic> to the 3′UTR of <italic>STAT3</italic> was experimentally validated by luciferase reporter assay, where <italic>miR-323a-3p</italic> reduced luminescent signal from full length <italic>STAT3</italic> 3′UTR luciferase reporter, but not from a reporter with mutation in the predicted seed sequence.</p></sec><sec><title>Conclusions</title><p><italic>miR-323a-3p</italic> inhibits growth of neuroblastoma cell lines through G1-cell cycle arrest and apoptosis, and the well-known oncogene <italic>STAT3</italic> is a direct target of this miRNA.</p></sec>