Stem cell-associated heterogeneity in Glioblastoma results from intrinsic tumor plasticity shaped by the microenvironment

Abstract

The identity and unique capacity of cancer stem cells (CSC) to drive tumor growth and resistance have been challenged in brain tumors. Here we report that cells expressing CSC-associated cell membrane markers in Glioblastoma (GBM) do not represent a clonal entity defined by distinct functional properties and transcriptomic profiles, but rather a plastic state that most cancer cells can adopt. We show that phenotypic heterogeneity arises from non-hierarchical, reversible state transitions, instructed by the microenvironment and is predictable by mathematical modeling. Although functional stem cell properties were similar in vitro, accelerated reconstitution of heterogeneity provides a growth advantage in vivo, suggesting that tumorigenic potential is linked to intrinsic plasticity rather than CSC multipotency. The capacity of any given cancer cell to reconstitute tumor heterogeneity cautions against therapies targeting CSC-associated membrane epitopes. Instead inherent cancer cell plasticity emerges as a novel relevant target for treatment.

TAT-Cx43266-283impairs metabolic plasticity in glioma stem cells in vitro and in vivo

“…Concomitantly, in the same glioma model used in this study, TAT-Cx43266-283 induces the loss of the stemness phenotype of the implanted GSCs, as evidenced by decreased expression of Sox-2 and nestin in these cells 7 days post-implantation, and impairs glioma growth 30 days post-implantation, leading to decreased tumorigenicity and increased survival 6 . Given our in vitro, ex vivo and in vivo results and the fundamental role played by HK-2 11,12 and GLUT-3 13 in glioma formation and development, TAT-Cx43266-283 might impair in vivo glioma growth through both the loss of the stemness phenotype 6 and the abrogation of metabolic plasticity, two phenomena that are highly dynamic and tightly linked 5,[13][14][15][16] .…”

“…Recent reports show that drug resistance to standard therapies, such as bevacizumab, relies on the ability of cancer cells to switch their metabolism from OXPHOS to glycolysis 8 . Therefore, it is noteworthy that, despite the well-characterized ability of cancer stem cells to adapt to new metabolic requirements 10,13,14 , GSCs treated with TAT-Cx43266-283 did not show enhanced glycolysis to compensate for the decreased mitochondrial activity ( Fig. 2g vs 2i).…”

“…The plasticity of the metabolic phenotype of cancer stem cells is crucial in the ever-changing tumour microenvironment 8,11,13,14 . In order to characterize the ability of the GSCs used in this study to adapt their metabolism to shifts in nutrient availability, we used time-lapse microscopy to analyse their survival in media with different nutrient contents.…”

“…A subset of cells within these tumours, termed glioma stem cells (GSCs), display highly tumorigenic capacity and resistance to conventional therapies, and are therefore considered responsible for recurrence 2,3 . The GSC phenotype is dynamic and can be acquired by non-GSCs upon challenging conditions, suggesting that inherent cancer cell plasticity is a relevant target for treatment 13,14 . These challenging conditions, which include hypoxia, an acidic environment or metabolic stress, promote the enrichment of the highly tumorigenic GSC population 13,15,16 .…”

A molecularly distinct subset of glioblastoma requires serum‐containing media to establish sustainable bona fide glioblastoma stem cell cultures

“…However, the hierarchical CSC model has been challenged by the hypothesis that the phenotypic tumor cell heterogeneity would be produced by plastic, niche‐driven cancer cells (Batlle & Clevers, ; Meacham & Morrison, ). In GBM, this was recently supported through experimental analyses and mathematical modeling, which showed that patient‐derived GBM cell cultures contained multiple subpopulations that were stem cell‐like, tumorigenic, and reversibly adaptable to environmental cues (Dirkse et al, ). An extensive single‐cell RNA sequencing‐based analysis of GBM tumors corroborated the plasticity model, where four main cell states were identified to drive GBM growth and transitions between states dictated by the specific genetic alterations and microenvironment in each tumor (Neftel et al, ).…”