Research And Grants

Targeting post-translational protein modification to halt Diffuse Intrinsic Pontine Glioma tumorgenicity

Diffuse intrinsic pontine gliomas (DIPG) are a devastating childhood brain cancer which are universally fatal. Currently DIPG remain incurable as no therapy has been developed that can target underlying processes involved in the pathogenesis of this disease. While key driver mutation have been identified (such as histone mutations), to date they have eluded effective therapeutic targeting. Citrullination, the conversion of arginine to citrulline, is an irreversible protein post-translational modification that changes the biochemical and functional properties of proteins. Protein citrullination occurs solely through the activation of the peptidylarginine deiminase (PAD) family of enzymes. At the heart of this proposal lies the novel concept that PAD activity is a pivotal event in and driving factor for DIPG tumorigenesis. Our hypothesis and supporting preliminary data introduce a paradigm shift away from the role of genetic mutations, offering alternative and tractable therapeutic strategies. Here, we now seek to highlight the role of, and include the irreversible protein post-translational modification of, citrullination as a causative event in DIPG, thus creating a new lens through which to view the oncogenesis and potential treatment of this disease.

Epigenetic dysregulation is recognised as a driver of DIPG pathogenesis, with the majority of patients exhibiting the main responsible histone mutation (H3K27M). While >80% of DIPG have this key genomic driver, the precise mechanism by which this leads to DIPG development remains undefined. Histones are a major target for citrullination and citrullination also occurs on non-nuclear proteins, many of which have potential functions in DIPG development. We have shown that pharmacological inhibition of PAD activity restores histone methylation, causing DIPG cell death through reactive oxygen species (ROS) activation of the unfolded protein response (UPR), with H3K27M DIPG particularly susceptible. We have developed and synthesised a novel blood brain permeable inhibitor of PAD activity that, when compared to the available tool compounds, demonstrates enhanced cytotoxicity against DIPG cultures. In addition to fully characterising the global changes within DIPG initiated through PAD inhibition, we aim to progress preliminary drug efficacy studies into our in vivo patient derived xenograft (PDX) models as a proof of principle towards a Phase I/II clinical trial, providing the necessary research pipeline towards an effective treatment for DIPG.

We aim to tease out the key and early events that drive pathogenesis in this disease, providing novel insights into new targets for therapeutic advantage, developing a platform of research to challenge and change the understanding of disease progression. The research proposed here will for the first time establish the role of citrullination in DIPG. We are taking the innovative step of using a combined multidisciplinary research team, from basic research scientists with a wealth of drug chemistry and cell biology knowledge, to lead clinicians on the forefront of DIPG treatment, a collaborative effort with a breadth of expertise that has the potential to facilitate breakthrough outcomes. By performing strategic studies focused on mechanistic outcomes, using advanced analyses encompassing innovative workflows and methodologies, our multifaceted approach will identify the global processes involved in DIPG development at both the transcriptional and post-translational level. The combination of our in vitro and in vivo studies on the efficacy of PAD inhibition within the setting of DIPG will provide a much-needed therapeutic option for the disease, positioning a lead compound for direct translation into the clinical setting. Through employing our detailed, comprehensive, and erstwhile underutilised analytical proteomics and metabolomics approaches within the setting of DIPG, we will greatly contribute to the overall understanding of the pathogenic processes involved in the disease, adding to the current scarcity of such information in the field. Hence, we have a clearly formulated plan to translate the knowledge and predictive insights gained from this research proposal, offering comprehensive advances that will categorically inform and influence ongoing DIPG therapeutic regimens.