Poster Presentation NSW State Cancer Conference 2023

MicroRNA to MicroRNA interactions: miR-21 regulation of miR17~92a cluster in Head & Neck Squamous Cell Carcinoma (#146)

Sarah Stapleton 1 , Meredith Hill 1 2 , Deborah Marsh 3 4 , Nham Tran 1 2
  1. School of Biomedical Engineering, Faculty of Engineering and Information Technology, University of Technology Sydney, Sydney, NSW, Australia
  2. Centre for Health Technologies, University of Technology Sydney, Sydney, NSW, Australia
  3. Translational Oncology Group, School of Life Sciences, Faculty of Science, University of Technology Sydney, Sydney, NSW, Australia
  4. Northern Clinical School, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, Australia

Introduction: MicroRNAs (miRNAs or miRs) control messenger RNA (mRNA) at the post-transcriptional level and have an important role in cancer development. Several studies have demonstrated that miRNAs are capable of regulating other miRNAs, known as a miR-miR interactions. To explore this relatively new idea, we investigated the role of miR-21, a major oncomiR, in initiating miR:miR interactions in head and neck cancer cells. Towards this end, miR-21 was overexpressed and knocked-down. Cells were then sequenced to understand how the expression of miRNAs were altered. This analysis, highlighted that the miR-17-92a cluster is a target of miR-21 regulation. This cluster is highly dysregulated in various cancers, but it is not fully understood how the cluster itself is regulated.

Objective: To investigate the regulatory relationship between miR-21 and the miR-17~92a cluster and the mechanism by which miR-21 regulates the cluster. 

Methods and Results: Head and neck cell lines were used as an in vitro cell model to confirm the relationship between miR-21 and the six members of the miR-17~92a cluster. Cells were transfected with miR-21 mimic and antisense and relative fold change of target miRNAs were evaluated using qPCR. Direct regulation of the cluster by miR-21 was then assessed with a luciferase reporter system. To determine if other miRNAs may be regulated by miR-21, a CRISPR knock-out of miR-21 was generated. MicroRNA seq analysis indicated that the miR-21 deletion affected the levels of other miRNAs.

Conclusions: It is proposed that a negative regulatory relationship exists between miR-21 and the miR-17~92a cluster and that miR-21 regulates the cluster by direct binding to the MIR17HG. Furthermore, deletion of miR-21 suggested that other miRNAs may be under the same regulatory control. Our study has provided new information regarding miR:miR interactions in cancer cells and we believe this is an underlying mechanism for controlling miRNA expression.