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Tumor-Associated Macrophages/Microglia in Glioblastoma Oncolytic Virotherapy: A Double-Edged Sword
Sarah E Blitz1, Ari D Kappel1,2, Florian A Gessler3
1Harvard Medical School, Boston, MA 02115, USA.
Abstract:
Oncolytic virotherapy is a rapidly progressing field that uses oncolytic viruses (OVs) to selectively infect malignant cells and cause an antitumor response through direct oncolysis and stimulation of the immune system. Despite demonstrated pre-clinical efficacy of OVs in many cancer types and some favorable clinical results in glioblastoma (GBM) trials, durable increases in overall survival have remained elusive. Recent evidence has emerged that tumor-associated macrophage/microglia (TAM) involvement is likely an important factor contributing to OV treatment failure. It is prudent to note that the relationship between TAMs and OV therapy failures is complex. Canonically activated TAMs (i.e., M1) drive an antitumor response while also inhibiting OV replication and spread. Meanwhile, M2 activated TAMs facilitate an immunosuppressive microenvironment thereby indirectly promoting tumor growth. In this focused review, we discuss the complicated interplay between TAMs and OV therapies in GBM. We review past studies that aimed to maximize effectiveness through immune system modulation-both immunostimulatory and immunosuppressant-and suggest future directions to maximize OV efficacy.
Insights
Oncolytic virus (OV) therapy shows promise for glioblastoma but faces challenges. Tumor-associated macrophages (TAMs) complicate treatment, with M1 TAMs inhibiting virus spread and M2 TAMs promoting tumor growth, impacting OV efficacy.
Area of Science:
- Oncology
- Immunology
- Virology
Background:
- Oncolytic virotherapy (OV) uses viruses to target cancer cells, stimulating antitumor immune responses.
- While effective pre-clinically and in some glioblastoma (GBM) trials, OVs have not consistently improved overall survival.
- Tumor-associated macrophages/microglia (TAMs) are increasingly recognized as critical factors in OV treatment outcomes.
Purpose of the Study:
- To review the complex role of TAMs in OV therapy for GBM.
- To analyze how TAM polarization (M1 vs. M2) influences OV efficacy and treatment failure.
- To explore immune modulation strategies and suggest future research directions for enhancing OV effectiveness.
Main Methods:
- Literature review of studies on OV therapy in GBM.
- Analysis of research investigating TAMs' interaction with OV treatments.
- Examination of immune modulation strategies (immuno-stimulatory and immuno-suppressive) in OV therapy.
Main Results:
- TAMs present a complex interaction with OV therapy, impacting treatment success.
- M1 TAMs can inhibit OV replication and spread, while M2 TAMs create an immunosuppressive environment that supports tumor growth.
- Past studies modulating the immune system have yielded mixed results, highlighting the need for nuanced approaches.
Conclusions:
- Understanding the dual role of TAMs is crucial for overcoming OV treatment limitations in GBM.
- Targeting TAMs or modulating their activity may be key to improving OV efficacy.
- Future research should focus on strategies that optimize the interplay between OVs and the tumor immune microenvironment, particularly TAMs, to achieve durable antitumor responses.
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