Radiation-Induced Modulation of Costimulatory and Coinhibitory T-Cell Signaling Molecules on Human Prostate Carcinoma Cells Promotes Productive Antitumor Immune Interactions

Abstract

We sought to determine if single-dose external beam radiation therapy (EBRT) could modulate the expression signature of T-cell costimulatory and coinhibitory molecules in human prostate cancer (PCa) cell lines in vitro. We investigated the functional impact of irradiated PCa cells with a modulated costimulatory profile on responder T-cell activity. We used three PCa cell lines (DU145, PC3, and LNCaP) and two epithelial cell lines from noncancerous prostate and lung tissue. After 72 hours of EBRT, surface expression of four immunostimulatory molecules (CD70, CD275/ICOSL, CD134L/OX40L, and CD137L/41BBL) and two immunosuppressive markers (CTLA-4/CD152 and PD-L1/CD274) were evaluated by flow cytometry. We evaluated the impact of several radiation doses and the longevity of modulated expression. We examined the functional impact of radiation-induced modulation of cancer cells by cytotoxic T cells (CTL) cytotoxicity and ELISPOT assay for interferon-gamma (IFN-γ) production. Last, we evaluated whether IFN-γ-induced PD-L1 expression could be reversed by EBRT. After 10 Gy EBRT, expression of OX40L and 41BBL increased in all three PCa cell lines; expression of CD70 and ICOSL increased in PC3 cells. Conversely, a decrease in PD-L1 expression in DU145 and PC3 cells was detectable up to 144 hours after EBRT. No PD-L1 was detected in LNCaP. Epithelial cells from normal prostate were not modulated by radiation. CTL cytolytic activity and IFN-γ production were enhanced by interaction with irradiated PCa cells. Finally, EBRT failed to prevent IFN-γ-induced upregulation of PD-L1. We demonstrate that a single dose of EBRT increased surface expression of costimulatory molecules and decreased the expression of coinhibitory molecules in human PCa cell lines. Changes in irradiated tumor cells led to functional enhancement of T-cell activity, despite EBRT failing to reduce IFN-γ-induced expression of PD-L1. These data suggest that combining radiotherapy with T-cell stimulating immunotherapy may be an attractive strategy for cancer treatment.

Immunotherapy and stereotactic ablative radiotherapy (ISABR): a curative approach?

“…In an attempt to find a potential therapeutic window for the addition of immunotherapeutic treatments, we analysed changes in tumour phenotypes at several time points following SABR. Whereas increased expression of immunostimulatory markers, including OX-40 ligand and 41BB ligand, was evident 72 hours after SABR, decreased expression of PD-L1 (programmed cell death 1 ligand 1), an inhibitor of T-cell expansion and function 28 , for example, was detect up to 144 hours after SABR 20 .…”

“…SABR involves treatment of tumours with radiation doses that often exceed 5 Gy per fraction with an exceedingly high level of conformality and sharp dose fall-off to spare the surrounding organs at risk. Investigators in many previous studies have focused on the effects of conventional fractionation regimens on the immune system; however, preliminary data suggest that radiation-induced immune responses might be dose-dependent 20,21 . In fact, using radiation doses in the ‘ablative’ range can not only effectively destroy tumour cells directly, but might also encourage these SABR-killed cells to function as a vaccine in situ 22,23 .…”

Changes of systemic immune response after stereotactic ablative radiotherapy (SABR) - first results of a prospective study in early lung cancer patients

“…Animal studies conducted by Huang et al 26 and Filatenkov et al 27 indicated that radiotherapy damages the immunosuppressive tumor microenvironment and subsequently leads to the recruitment of immune cells such as antigen -presenting cells, T cells, and NK cells, which are crucial in antitumor reactions. 28 Bernstein et al 29 have shown that a single dose of 5 Gy, 10 Gy, or 15 Gy increases the expression of costimulatory molecules and Dosimetric parameters of healthy tissues and selected immune factors The exposure of healthy tissue to X -rays was small (TABLE 1). None of the variables: the SABR schedule, dosimetric parameters such as lung volume exposed to ≥20 Gy (V20 Gy, 20-Gy isodose volume of the lungs), mean lung dose (MLD), esophagus mean dose, as well as other radiotherapy parameters correlated with the immune system parameters, serum CRP levels, or WBC count and ANC.…”

Key mechanisms involved in ionizing radiation-induced systemic effects. A current review

“…135 The modulation by radiation of immune checkpoints, namely co-stimulatory and inhibitory molecules on T cells, is under current intensive examination to pave the way for multimodal treatments consisting of radiochemotherapy plus immune therapy. 240,241 The immunological effects of RT are mostly described in patients with melanoma. 242 Non-redundant immune mechanisms get activated in cancer by combining RT with checkpoint inhibitors.…”