Poster Presentation 32nd Lorne Cancer 2020

­MicroRNA-based therapeutics for the treatment of high-risk neuroblastoma (#180)

Holly Holliday 1 2 , Eoin Dodson 1 2 , Iva Nikolic 3 4 , Niantao Deng 1 2 , Kaylene Simpson 3 4 , Alvin Kamili 5 6 , Madeleine Whatley 5 , Jessica Yang 1 , David Croucher 1 2 , Joshua McCarroll 5 , Glenn Marshall 7 , Jamie Fletcher 5 , Alex Swarbrick 1 2
  1. Garvan Institute, Darlinghurst, NSW, Australia
  2. St Vincent's Clinical School, Faculty of Medicine, UNSW
  3. Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia
  4. Victorian Centre for Functional Genomics, Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  5. Children's Cancer Institute, Lowy Cancer Research Centre, UNSW, Sydney, NSW, Australia
  6. School of Women’s and Children’s Health, UNSW , Sydney, NSW, Australia
  7. Sydney Children’s Hospital and Children’s Cancer Institute, Sydney, NSW, Australia

Neuroblastoma is a cancer of the developing sympathetic nervous system and is the most common extra-cranial cancer affecting children. High-risk patients are currently treated with intensive multi-layered chemotherapy which is not always curative and leaves surviving patients with life-long side effects, underscoring an urgent need for safer treatments. miRNA-based drugs represent an exciting new class of cancer therapeutic. However, our understanding of miRNA function in neuroblastoma is fragmented, restricting our ability to capitalise on their therapeutic potential. 

Through extensive functional genomics screening, we have identified several miRNAs that can kill neuroblastoma cell lines, but not normal cells, either alone (miR-552-3p and miR-101-3p) or in combination with low doses (IC30) of chemotherapy (miR-99b-5p, miR-380-3p, and miR-485-3p). These miRNAs are putative novel tumour suppressors in neuroblastoma as they undergo copy number loss in a subset of patients, and low expression predicts poor clinical outcome.

Selected candidate miRNAs are currently being tested in a patient derived xenograft (PDX) model of high-risk disease, either as a single agent, or with topotecan chemotherapy. In a proof-of-principal experiment, miR-99b-5p mimics conjugated to star-POEGMA nanoparticles were delivered via intratumoral injection and miRNA uptake, gene expression, and histology were assessed following one week. 

Encouragingly, miR-99b-5p could be effectively delivered (40-fold increase) to PDX tumours. RNA-Seq analysis of miR-99b-5p-treated tumours revealed downregulation of key neuroblastoma dependency genes MYCN, PHOX2B, HAND1/2, GATA3, ISL1 and EZH2. Importantly, many of these genes encode core regulatory lineage-defining transcription factors in neuroblastoma (1,2), which are considered to be ‘undruggable’. Additionally, miRNA treatment resulted in upregulation of neuronal differentiation genes, suggesting that miR-99b-5p can differentiate the tumour cells, or kill off undifferentiated tumour cells.

Ongoing work includes longer experiments to access tumour growth and survival outcome. If successful, we predict that restoring the function of tumour suppressive miRNAs represents an attractive new therapeutic strategy for the treatment of neuroblastoma patients.