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

Abstract

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.

Immune modulation resulting from MR-guided high intensity focused ultrasound in a model of murine breast cancer

“…For thermal ablation, continuous wave insonation was applied at 3.1 MPa peak negative pressure (PNP), whereas for mechanical ablation a 16.9 MPa PNP was applied and the duty cycle was www.nature.com/scientificreports/ minimized such that any temperature increase was less than 2 °C. The resulting studies provide a starting point for the comparison of regimes; however, in the future, comparisons to the histotripsy protocols used in [56][57][58][59] must also be made directly with the dedicated lower frequency equipment required for those studies. A disadvantage of such equipment (limiting a comparative study of thermal and mechanical mechanisms) is the larger insonified volume (relative to mouse tumors) and the incompatibility with MR guidance.…”

Boiling histotripsy and in-situ CD40 stimulation improve the checkpoint blockade therapy of poorly immunogenic tumors

“…The objective of this study was to understand the ability of HT40 to reprogram the immunologically cold melanoma tumor such that it becomes more receptive to ICI therapy. HT has been utilized to debulk tumor tissue, release damage associated molecular patterns (DAMPs), and improve immune sensitization in various tumor models 24 , 27 , 36 , 56 . We and others have also shown that local αCD40 therapy activates APCs and improves the functional status of TILs in melanoma 21 , 57 , 58 .…”

“…Boiling HT is a non-invasive mechanical homogenization technology that rapidly generates tumor antigen depots with sharp boundaries in solid cancers. Since HT achieves heating to 100 ºC by using millisecond-long pulses with lower pulse repetition frequency (PRF) 34 , it avoids denaturation of tumor antigens in the focal regions 36 . Thus, its combination with αCD40 can hypothetically improve tumor immune environment, and immunotherapeutic response.…”

“…However, boiling HT achieves instantaneous, predictable and controllable homogenization and heating of focal regions to 100 ºC by using millisecond-long pulses with lower pulse repetition frequency (PRF) 34 . Boiling HT occurs for milliseconds, so it induces little or no damage to nearby structures due to minimal heat diffusion, while also achieving rapid accumulation of tumor-associated and neo-antigens in targeted tumor regions, enhancing immune cell infiltration by chemotaxis 35 , 36 . The activation of infiltrated antigen-presenting cells (APCs) and their subsequent migration to lymphoid tissues improve tumor antigen presentation to naïve T cells, thus causing antigen-specific tumor destruction 24 , 37 , 38 .…”

Investigation of the Potential Immunological Effects of Boiling Histotripsy for Cancer Treatment

“…Shear stresses produced around an oscillating boiling vapor bubble and emissions of shockwaves and jetting resulting from a cavitation cluster can contribute to forming a BH lesion. [11,13] In contrast to HIFU thermal ablation, since BH treatment is not greatly affected by heat perfusion via blood flow, BH can produce a sharper transition zone between untreated and treated regions with a transition distance of less than a cell length. During HIFU thermal ablation exposure, for example, normal healthy tissue surrounding the HIFU focus can be thermally ablated due to thermal diffusion effect.…”