E-Poster Presentation 34th Lorne Cancer Conference 2022

Ion channels as novel therapeutic targets in diffuse midline glioma (#339)

Abbie Francis 1 2 , Stephen Dymock 1 2 , Jan Fromm 2 3 , Anya Jones 1 2 , Sara Rezaeiravesh 1 2 , Zi Ying Ng 2 , Emily Fletcher 1 2 , Terrance Johns 1 2
  1. University of Western Australia, Crawley, WA, Australia
  2. Telethon Kids Institute, Nedlands, WESTERN AUSTRALIA, Australia
  3. Murdoch University, Murdoch, WA, Australia

Background

Diffuse midline glioma (DMG) is a rare form of paediatric brain cancer that remains universally fatal despite decades of research. DMG is minimally responsive to chemo- and radiotherapies and tumours rapidly develop resistance to targeted therapies. Ion channels are known to play a role in cell proliferation, survival, and plasticity, and correlate with treatment resistance and disease severity of other cancers. Therefore, we hypothesise that ion channels could be mediating treatment resistance in DMG and represent novel therapeutic targets.

 

Aim

Characterise the expression of ion channels in DMG and investigate their potential as drug targets.

 

Methods

mRNA expression of 184 ion channel genes was measured in three patient derived DMG cell lines using qPCR arrays. Key gene targets were validated using independent qPCRs in five DMG cell lines. Protein expression of candidate genes was evaluated using western blotting and immunofluorescence. DMG cell proliferation was measured 7 days after treatment with ion channel targeting drugs.

 

Results

DMG cells expressed 91% (84/92) of voltage gated and 83% (76/92) of ligand gated ion channel genes (defined as mean Ct<35), and mRNA expression positively correlated with RNA sequencing data from DMG patient tissue (p<0.0001, Pearson’s correlation). Voltage-gated calcium channels and ligand-gated chloride channels were identified as key families and had strong expression in mRNA and protein validation studies. Furthermore, these genes were upregulated following irradiation, suggesting they are responsive to standard therapies. Lastly, DMG cell proliferation was greatly reduced following treatment with drugs targeting these ion channels at clinically relevant concentrations. For example, one drug that targets voltage-gated calcium channels had an IC50 on DMG cells of ~4 μM.

 

Significance and Clinical Relevance 

Ion channels are expressed in DMG and represent novel therapeutic targets. Relevant drugs are already clinically approved to treat other neurological conditions, which speeds clinical translation. Future studies will investigate leading drug candidates in paediatric mouse and zebrafish models.