Reprogramming the immunosuppressive tumor microenvironment results in successful clearance of tumors resistant to radiation therapy and anti-PD-1/PD-L1.

Despite breakthroughs in immune checkpoint inhibitors (ICI), the majority of tumors, including those poorly infiltrated by CD8+ T cells or heavily infiltrated by immunosuppressive immune effector cells, are unlikely to result in clinically meaningful tumor responses. Radiation therapy (RT) has been combined with ICI to potentially overcome this resistance and improve response rates but reported clinical trial results have thus far been disappointing. Novel approaches are required to overcome this resistance and reprogram the immunosuppressive tumor microenvironment (TME) and address this major unmet clinical need.

The CD40 agonist HERA-CD40L results in enhanced activation of antigen presenting cells, promoting an anti-tumor effect alone and in combination with radiotherapy.

Introduction: The ability to modulate and enhance the anti-tumor immune responses is critical in developing novel therapies in cancer. The Tumor Necrosis Factor (TNF) Receptor Super Family (TNFRSF) are potentially excellent targets for modulation which result in specific anti-tumor immune responses. CD40 is a member of the TNFRSF and several clinical therapies are under development.

Low CD8 T Cell Counts Predict Benefit from Hypoxia-Modifying Therapy in Muscle-Invasive Bladder Cancer.

Background: As hypoxia can drive an immunosuppressive tumour microenvironment and inhibit CD8+ T cells, we investigated if patients with low tumour CD8+ T cells benefitted from hypoxia-modifying therapy.

Methods: BCON was a phase III trial that randomised patients with muscle-invasive bladder cancer (MIBC) to radiotherapy alone or with hypoxia-modifying carbogen plus nicotinamide (CON). Tissue microarrays of diagnostic biopsies from 116 BCON patients were stained using multiplex immunohistochemistry (IHC) with the markers CD8, CD4, FOXP3, CD68 and PD-L1, plus DAPI.

Radiotherapy transiently reduces the sensitivity of cancer cells to lymphocyte cytotoxicity.

The impact of radiotherapy on the interaction between immune cells and cancer cells is important not least because radiotherapy can be used alongside immunotherapy as a cancer treatment. Unexpectedly, we found that X-ray irradiation of cancer cells induced significant resistance to natural killer (NK) cell killing. This was true across a wide variety of cancer-cell types as well as for antibody-dependent cellular cytotoxicity.

The effect of hypoxia on PD-L1 expression in bladder cancer.

Introduction: Recent data has demonstrated that hypoxia drives an immunosuppressive tumour microenvironment (TME) via various mechanisms including hypoxia inducible factor (HIF)-dependent upregulation of programmed death ligand 1 (PD-L1). Both hypoxia and an immunosuppressive TME are targetable independent negative prognostic factors for bladder cancer. Therefore we sought to investigate whether hypoxia is associated with upregulation of PD-L1 in the disease.

Investigating Radiotherapy Response in a Novel Syngeneic Model of Prostate Cancer.

The prostate cancer (PCa) field lacks clinically relevant, syngeneic mouse models which retain the tumour microenvironment observed in PCa patients. This study establishes a cell line from prostate tumour tissue derived from the mouse, termed DVL3 which when subcutaneously implanted in immunocompetent C57BL/6 mice, forms tumours with distinct glandular morphology, strong cytokeratin 8 and androgen receptor expression, recapitulating high-risk localised human PCa. Compared to the commonly used TRAMP C1 model, generated with SV40 large T-antigen, DVL3 tumours are immunologically cold, with a lower proportion of CD8+ T-cells, and high proportion of immunosuppressive myeloid derived suppressor cells (MDSCs), thus resembling high-risk PCa.

Responses to ionizing radiation mediated by inflammatory mechanisms.

Since the early years of the twentieth century, the biological consequences of exposure to ionizing radiation have been attributed solely to mutational DNA damage or cell death induced in irradiated cells at the time of exposure. However, numerous observations have been at variance with this dogma. In the 1950s, attention was drawn to abscopal effects in areas of the body not directly irradiated.

The influence of p53 functions on radiation-induced inflammatory bystander-type signaling in murine bone marrow.

Radiation-induced bystander and abscopal effects, in which DNA damage is produced by inter-cellular communication, indicate mechanisms of generating damage in addition to those observed in directly irradiated cells. In this article, we show that the bone marrow of irradiated p53(+/+) mice, but not p53(-/-) mice, produces the inflammatory pro-apoptotic cytokines FasL and TNF-α able to induce p53-independent apoptosis in vitro in nonirradiated p53(-/-) bone marrow cells. Using a congenic sex-mismatch bone marrow transplantation protocol to generate chimeric mice, p53(-/-) hemopoietic cells functioning in a p53(+/+) bone marrow stromal microenvironment exhibited greater cell killing after irradiation than p53(-/-) hemopoietic cells in a p53(-/-) microenvironment.

Radiation-induced bone marrow apoptosis, inflammatory bystander-type signaling and tissue cytotoxicity.

Purpose: A study of irradiated (0.25-2 Gy) murine bone marrow has investigated the relationships between apoptotic responses of cells exposed in vivo and in vitro and between in vivo apoptosis and tissue cytotoxicity.

Materials And Methods: The time course of reduction in bone marrow cellularity in vivo was determined by femoral cell counts and apoptosis measurements obtained using three commonly used assays.

The in vivo expression of radiation-induced chromosomal instability has an inflammatory mechanism.

Ionizing radiation is unequivocally leukemogenic and carcinogenic, and this is generally attributed to DNA damage arising as a consequence of deposition of energy in the cell nucleus at the time of exposure. However, nontargeted effects, in which DNA damage is produced in nonirradiated cells as a consequence of cell signaling processes, indicate additional mechanisms. Radiation-induced chromosomal instability, a nontargeted effect with the potential to produce pathological consequences, is characterized by an increased rate of chromosome aberrations many generations after the initial insult.

Long-lived inflammatory signaling in irradiated bone marrow is genome dependent.

Ionizing radiation is carcinogenic, but genotype is a key determinant of susceptibility. Mutational DNA damage is generally attributed to cause disease, but irradiation also affects multicellular interactions as a result of poorly understood bystander effects that may influence carcinogenic susceptibility. In this study, we show that the bone marrow of irradiated mice will retain the ability to kill hemopoietic clonogenic stem cells and to induce chromosomal instability for up to 3 months after irradiation.