Abstract 709: Enhancing prostate cancer treatment: Synergistic effects of mechano-thermal focused ultrasound and radiation therapy
Authors: Chatterjee Soumya , Singh Saurabh , Barry Stephen , Guha Chandan 
Published: March 2024

Current treatments for prostate cancer primarily rely on radiation and hormone deprivation therapy, yet they often lack effective immunotherapeutic effects. Furthermore, long-term hormone ablation has side effects, such as, impotency and osteoporosis. Addressing this gap, we introduce an innovative dual-frequency focused ultrasound (FUS) platform for non-ablative focal therapy, which induces protein unfolding, ER stress, and increases heat-shock protein expression along with translocation of endoplasmic reticular chaperone proteins (e.g., calreticulin) on the tumor cell surface, thereby sensitizing them for phagocytosis by dendritic cells for efficient antigen presentation and cross priming. We hypothesized that FUS-mediated acoustic immune priming can be combined with ablative therapies, such as, hormone ablation and/or radiation therapy (RT) for induction of tumor-specific adaptive immune response and better tumor control than monotherapy in murine prostate cancer models. Utilizing murine prostate cancer cell lines, MyC-CaP and RM1, we explored the cellular responses to androgen deprivation, observing distinct sensitivities. Twenty-four hours after FUS treatment tumor cells experienced mechano-thermal stress response with 15-fold increase in Hspa1a expression. Transmission Electron Microscopy studies showed formation of myelin figures, nuclear membrane deformation, and lipid droplet formation. In vivo, the combination of FUS (220w/cm2 intensity for 3 sec at focal point) and RT (8-10 Gy daily x two fractions) markedly delayed tumor growth and achieved complete cure in 14-17% of animals. Through multicolor flow cytometry, we detected significant alterations in the immune microenvironment, including increased CD8+ T cell infiltration and reduced tumor-associated macrophages in the tumor bed. However, we also observed a compensatory rise in pro-tumor immune cells such as PMN-MDSCs and Tregs with significant suppression of eosinophils (p&lt;0.05). Interestingly, there was suppression of splenic PMN-MDSCs, Mo-MDSCs, and tumor draining lymph node macrophages, suggesting systemic immune modulation in peripheral lymphoid organs of FUS+RT-treated tumor-bearing animals. Our findings reveal that the combination therapy of FUS and RT improves tumor control in murine prostate cancer and significantly modulates the systemic and tumor immune microenvironment. This approach offers new avenues for immunotherapy, potentially transforming the treatment landscape for prostate cancer, typically resistant to conventional immunotherapeutic strategies.

Citation Format: Soumya Chatterjee, Saurabh Singh, Stephen Barry, Chandan Guha. Enhancing prostate cancer treatment: Synergistic effects of mechano-thermal focused ultrasound and radiation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 709.