Cure Alveolar Soft Part Sarcoma International (iCureASPS)

Radiotherapy and immunotherapy: a beneficial liaison?


Abstract
Investigations into the interaction between radiotherapy and the host immune system have uncovered new mechanisms that can potentially be exploited to improve the efficacy of radiotherapy. Radiation promotes the release of danger signals and chemokines that recruit inflammatory cells into the tumour microenvironment, including antigen-presenting cells that activate cytotoxic T-cell function. By contrast, radiation can attract immunosuppressive cells into the tumour microenvironment. In rare circumstances, the antitumour effect of radiotherapy has been observed outside of the radiation field, known as the abscopal effect. This phenomenon is proposed to have an immune origin and indicates that local radiotherapy elicits systemic effects. Herein, we highlight data that provide new mechanistic explanations for the success or failure of radiotherapy, and postulate how the combination of immune-modulation and radiation could tip the balance of the host immune response to promote cure. We use the concept of radiation- induced tumour equilibrium (RITE) as a starting point to discuss the mechanistic influence of immune-checkpoint therapies on radiotherapy efficacy.



https://www.ncbi.nlm.nih.gov/m/pubmed/2 ... 01/related

Radiation-Induced Equilibrium Is a Balance between Tumor Cell Proliferation and T Cell–Mediated Killing


Abstract

Local failures following radiation therapy are multifactorial, and the contributions of the tumor and the host are complex. Current models of tumor equilibrium suggest that a balance exists between cell birth and cell death due to insufficient angiogenesis, immune effects, or intrinsic cellular factors. We investigated whether host immune responses contribute to radiation-induced tumor equilibrium in animal models. We report an essential role for immune cells and their cytokines in suppressing tumor cell regrowth in two experimental animal model systems. Depletion of T cells or neutralization of IFN-γ reversed radiation-induced equilibrium, leading to tumor regrowth. We also demonstrate that PD-L1 blockade augments T cell responses, leading to rejection of tumors in radiation-induced equilibrium. We identify an active interplay between tumor cells and immune cells that occurs in radiation-induced tumor equilibrium and suggest a potential role for disruption of the PD-L1/PD-1 axis in increasing local tumor control.



http://www.jimmunol.org/content/190/11/5874