Title: Targeting subclonal diversity and co-operation in paediatric glioblastoma and diffuse intrinsic pontine glioma
Funder: Cancer Research UK

Abstract: Background Widespread intratumoral heterogeneity in human cancer has become a prevalent theme in high-throughput sequence analysis of tumour specimens, with critically important implications for the success of therapeutic targeting. Less attention has been given to the functional consequences of this subclonal diversity and the interactions between distinct tumour subpopulations. We have utilised paediatric glioblastoma (pGBM) and diffuse intrinsic pontine glioma (DIPG) as cancer types with a relatively low mutational burden, yet a high degree of heterogeneity, and developed a methodology to isolate genotypically and phenotypically distinct subclonal compartments with stem-like properties for mechanistic studies. We have evidence that subclonal diversity is selected for, both temporally and spatially, due to co-operative interactions between these subpopulations which enhance tumorigenic phenotypes en masse. Understanding how these subclones interact will be a key requirement in order to maximise patient benefit from existing treatment options as well as developing therapeutic novel approaches aimed at disrupting these interactions. Aims We will refine our understanding of the cell-autonomous and non-autonomous interactions between tumour subclones and with the tumour microenvironment. We will model co-operation in vitro and in vivo and identify novel interventions aimed at disrupting advantageous clonal interactions. Methods The temperospatial subclonal architecture of pGBM and DIPG will be mapped through multi-region and longitudinal sampling strategies linked to deep molecular characterisation, using analytical approaches aimed at inferring subclonal architecture and reconstructing tumour phylogenies. These samples will be subjected to our techniques for the isolation of subclonal stem-like populations. Co-operation will be modelled using co-culture and conditioned media experiments in vitro, analysed via differential labelling on high-content imaging platforms. Reconstruction of tumour heterogeneity will be mathematically modelled and tested in vitro and orthotopically in vivo. The influence of the developing brain microenvironment will be tested ex vivo using brain slice assays and in vivo using heterotopic implantation. High-throughput screening assays aimed at disrupting positive subclonal interactions will be validated in vitro and in vivo, and the influence of the selective pressures exerted by targeted therapies evaluated on advanced sampling from patients enrolled in stratified clinical trials. How the results of this research will be used Although intratumoral heterogeneity may be severely limiting the effectiveness of existing treatments, understanding and disrupting co-operative interclonal communication provides a novel avenue for future therapeutic development. We anticipate devising functionally-based strategies uniquely aimed at these processes which may be rapidly incorporated intro clinical trials for children with these otherwise incurable tumours.


Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS
Health categories: CANCER AND NEOPLASMS