Harnessing macrophages in thermal and non-thermal ablative therapies for urologic cancers – Potential for immunotherapy

Ionizing radiation and photodynamic therapy lead to multimodal tumor cell death, synergistic cytotoxicity and immune cell invasion in human bladder cancer organoids

BACKGROUND

Photodynamic therapy (PDT) and radiotherapy using ionizing radiation (IR) are promising options for organ-preserving treatment of bladder cancer (BCa). A combination therapy (IR+PDT) could be beneficial for BCa treatment.

PURPOSE

For PDT, we used the near-infrared photosensitizer tetrahydroporphyrin-tetratosylate (THPTS) showing high therapeutic efficacy. Treatment responses were analyzed in BCa organoids.

METHODS

Organoids consisting of BCa cells lines, bladder fibroblasts and muscle cells were treated with IR (9 Gy) and/or PDT using THPTS (25, 50 μM; 20 J/cm2). Cytotoxicity was determined by microscopy, cell-based assays and histology. The cell death mode was analyzed by applying specific inhibitors followed by immunofluorescence or qPCR analyses of cell death markers. A matrix-based co-culture model was used to study T cell migration into the environment of treated organoids.

RESULTS

PDT and/or IR resulted in concentration-dependent reduction of metabolic activity, organoid diameter and integrity. Higher cytotoxicity of IR+PDT vs. monotherapies was observed after 72 h. Non-malignant organoids showed no cytotoxic effects. While apoptosis, necroptosis and ferroptosis were clearly involved in cell death of T-24 cells, cytotoxicity in RT-112 cells was probably provoked by apoptosis, ferroptosis and pyroptosis. IR+PDT resulted in significant migration of Jurkat cells into ECM-embedded organoids within 3 days after treatment.

CONCLUSION

Treatment with IR+PDT showed tumor-selective cytotoxicity with additive or synergistic effects in BCa organoids. Thereby, IR+PDT led to multimodal cell death depending on the cellular context. Migration of T cells into the organoid environment illustrates the immunogenic potential of IR+PDT. Therefore, it might be a promising approach for organ-preserving BCa treatment.

Boiling Histotripsy-induced Partial Mechanical Ablation Modulates Tumour Microenvironment by Promoting Immunogenic Cell Death of Cancers

Boiling histotripsy is a promising non-invasive High-Intensity Focused Ultrasound (HIFU) technique that employs HIFU mechanical effects to fractionate solid tumours without causing any significant thermal damage. It has been suggested that boiling histotripsy may induce a strong immune response due to the absence of denatured antigenic protein at the HIFU focus. The underlying immunological mechanisms of this technique are, however, poorly understood. In this study, we demonstrated the feasibility of using boiling histotripsy to mechanically fractionate human breast adenocarcinoma cells (MDA-MB-231) and the potential immunological effects induced by boiling histotripsy, for the first time. Our results showed that mechanical stresses produced by boiling histotripsy promote immunogenic cell death of cancer cells via TNF-induced necrosis signaling pathway. This immunogenic cell death significantly increases secretions of damage-associated molecular patterns (CRT, HSP70, HMGB-1), pro-inflammatory cytokines (IFN-γ, IL-1α, IL-1β, IL-18) and chemokines (IL-8) which are related to M1 macrophage activation. Furthermore, the levels of these signaling proteins increase with the degree of mechanical damage induced by boiling histotripsy. Together, the results presented can suggest that boiling histotripsy could be a potential therapeutic approach for not only mechanically destroying solid tumours (e.g., breast cancer) but also promoting immunogenic cell death via TNF-induced necrosis to trigger antitumour immunity.