Inhibitor of Apoptosis Proteins Determines Glioblastoma Stem-Like Cell Fate in an Oxygen-Dependent Manner

Abstract

In glioblastomas, apoptosis inhibitor proteins (IAPs) are involved in apoptotic and nonapoptotic processes. We previously showed that IAP inhibition induced a loss of stemness and glioblastoma stem cells differentiation by activating nuclear factor‐κB under normoxic conditions. Hypoxia has been shown to modulate drug efficacy. Here, we investigated how IAPs participate in glioblastoma stem‐like cell maintenance and fate under hypoxia. We showed that in a hypoxic environment, IAPs inhibition by GDC‐0152, a small‐molecule IAPs inhibitor, triggered stem‐like cell apoptosis and decreased proliferation in four human glioblastoma cell lines. We set up a three‐dimensional glioblastoma spheroid model in which time‐of‐flight secondary ion mass spectrometry analyses revealed a decrease in oxygen levels between the periphery and core. We observed low proliferative and apoptotic cells located close to the hypoxic core of the spheres and glial fibrillary acidic protein+ cells at their periphery. These oxygen‐dependent GDC‐0152 antitumoral effects have been confirmed on human glioblastoma explants. Notably, serine–threonine kinase activation analysis revealed that under hypoxic conditions, IAP inhibition activated ataxia telangiectasia and Rad3‐related protein signaling. Our findings provide new insights into the dual mechanism of action of IAP inhibitors that depends on oxygen level and are relevant to their therapeutic application in tumors. Stem Cells 2019;37:731–742

Practical Review on Preclinical Human 3D Glioblastoma Models: Advances and Challenges for Clinical Translation

“…Moreover, after orthotopic xenograft, this model recapitulates, at each in vivo passage, the hierarchical cell organization and heterogeneity of the parental tumor [ 75 ]. As for the spheroid model, the growth of the tumorospheres is standardized, and a gradient of proliferation, oxygen, nutrients, and pH can be identified [ 76 ].…”

“…As GBM relapses are known to be associated with GBM CSLCs, tumorospheres are essential to study stemness properties like clonogenicity, proliferation, differentiation, and migration. For example, we used this model to study CSLCs organization and differentiation according to hypoxia and drug response [ 76 ]. As CSLCs are resistant to conventional therapies, this model is useful for new drug testing [ 11 , 76 , 77 , 78 ].…”

The Organoid Era Permits the Development of New Applications to Study Glioblastoma

“…These cells can differentiate in neural cells (neurons, astrocytes or oligodendrocytes) with a similar proportion to the parental tumor [54]. Importantly, tumorspheres present an hypoxic core and a highly proliferating periphery [55,56]. Despite the relevant insights that this model has probed on stemness properties and drug resistance [55,57], tumorspheres are highly unstable and, after few passages, a clonal expansion of a specific cell population can be observed [58].…”

“…Importantly, tumorspheres present an hypoxic core and a highly proliferating periphery [55,56]. Despite the relevant insights that this model has probed on stemness properties and drug resistance [55,57], tumorspheres are highly unstable and, after few passages, a clonal expansion of a specific cell population can be observed [58]. Moreover, cells growing in Matrigel™ and EGF/FGF2 containing media may be influenced by these exogenous factors.…”

EB1-dependent long survival of glioblastoma-grafted mice with the oral tubulin-binder BAL101553 is associated with inhibition of tumor angiogenesis

“…GBM tissue samples from a GBM patient were collected after surgery and placed in Dulbecco's modified Eagle's medium (DMEM) supplemented with 0.5% fetal calf serum (FCS), 1% penicillin-streptomycin and 1% sodium pyruvate (Gibco-Invitrogen, Cergy Pontoise) [44]. Tissues were cut into 500 μm pieces in defined serum-free stem cell medium [16] and plated on 12-well plates precoated with poly-(L)-lysine (10 μg/mL; Sigma).…”