Introduction/Aim: The leading causes of death from glioblastoma (GBM) is tumour invasion by the highly infiltrative, actively ‘proliferating’ tumour cells as well as post-treatment tumour recurrence arising from the chemoresistant/radioresistant tumour cells residing in the ‘non-proliferating’ tumour subfraction. Our aim is to establish a profiling method that will simultaneously characterise the gene expression of both tumour subfractions to determine differences that could help resolve intra-tumoural heterogeneity, a major obstacle in GBM therapy.
Methods: In vitro GBM cells and tumour cells derived from an orthotopic model were bisected into ‘proliferating’ and ‘non-proliferating’ subfractions sorted based on the incorporation of the proliferation marker 5-ethynyl-2’-deoxyuridine into actively replicating cells. The tumour subfractions were subsequently analysed for a number of transcripts. Additionally, clones of different tumourigenic capacity derived from the parental tumour were similarly analysed following orthotopic implantation.
Results: While we did not find any significant difference in the gene profiles between the two cellular subsets in vitro, we demonstrate ~2-6 fold increase in transcripts of cancer and neuronal stem cell markers and genes involved in tumour cell migration/invasion and ~2-fold decrease in transcripts of markers of hypoxia and their target genes in the proliferating tumour cells of the orthotopic GBM model when compared to their non-proliferating counterparts. When clones of different tumourigenicity were compared, the level of differential expression correlated directly to the tumourigenic potential of each tumour.
Conclusion: This study establishes a novel profiling approach that allows for differential studies to dissect intra-tumoural heterogeneity based on proliferative capacity, providing a platform for elucidating the unique biology of individual tumours, with consequences for treatment design.