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Published on: February 16, 2015
Gamma Irradiation Triggers Immune Escape in Glioma-Propagating Cells
Nicola Hoppmann1, Nora Heinig2, Ute Distler3
1Department of Neurology, Research Center Translational Neurosciences (FTN), Rhine-Main Neuroscience Network (rmn2), University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
Abstract:
Glioblastoma multiforme is the most common and devastating form of brain tumor for which only palliative radio- and chemotherapy exists. Although some clinical studies on vaccination approaches have shown promising efficacy due to their potential to generate long-term immune surveillance against cancer cells, the evasion mechanisms preventing therapy response are largely uncharacterized. Here, we studied the response of glioblastoma-propagating cells (GPCs) to clinically relevant doses of γ radiation. GPCs were treated with 2.5 Gy of γ radiation in seven consecutive cellular passages to select for GPCs with increased colony-forming properties and intrinsic or radiation-induced resistance (rsGPCs). Quantitative proteomic analysis of the cellular signaling platforms of the detergent-resistant membranes (lipid rafts) in GPCs vs. rsGPCs revealed a downregulation of the MHC class I antigen-processing and -presentation machinery. Importantly, the radio-selected GPCs showed reduced susceptibility towards cytotoxic CD8+ T-cell-mediated killing. While previous studies suggested that high-dose irradiation results in enhanced antigen presentation, we demonstrated that clinically relevant sub-lethal fractionated irradiation results in reduced expression of components of the MHC class I antigen-processing and -presentation pathway leading to immune escape.
Insights
Sub-lethal radiation therapy for glioblastoma may help cancer cells evade immune detection. This study shows radiation-resistant glioblastoma-propagating cells downregulate immune-evading pathways, reducing CD8+ T-cell killing.
Area of Science:
- Oncology
- Immunology
- Radiation Oncology
Background:
- Glioblastoma multiforme is an aggressive brain tumor with limited treatment options.
- Current treatments like radiotherapy and chemotherapy offer palliative care.
- Cancer vaccines show promise for long-term immune surveillance, but evasion mechanisms remain unclear.
Purpose of the Study:
- To investigate the immune evasion mechanisms of glioblastoma-propagating cells (GPCs) under clinically relevant radiation doses.
- To understand how fractionated, sub-lethal irradiation affects GPC resistance and immune presentation.
Main Methods:
- Glioblastoma-propagating cells (GPCs) were subjected to fractionated gamma radiation (2.5 Gy) over multiple passages.
- Quantitative proteomic analysis was performed on lipid rafts of radiation-sensitive (GPCs) and radiation-resistant (rsGPCs) cells.
- Susceptibility of rsGPCs to CD8+ T-cell-mediated killing was assessed.
Main Results:
- Radiation-selected GPCs (rsGPCs) exhibited increased colony-forming ability and resistance.
- rsGPCs showed a downregulation of MHC class I antigen-processing and presentation machinery.
- rsGPCs demonstrated reduced susceptibility to cytotoxic CD8+ T-cell killing.
Conclusions:
- Clinically relevant, sub-lethal fractionated irradiation can induce immune escape in glioblastoma.
- Downregulation of MHC class I pathways in radio-resistant GPCs contributes to immune evasion.
- This finding contrasts with high-dose irradiation effects and highlights a critical mechanism for glioblastoma treatment failure.
