Mechanical high-intensity focused ultrasound creates unique tumor debris enhancing dendritic cell-induced T cell activation

Abstract

IntroductionIn situ tumor ablation releases a unique repertoire of antigens from a heterogeneous population of tumor cells. High-intensity focused ultrasound (HIFU) is a completely noninvasive ablation therapy that can be used to ablate tumors either by heating (thermal (T)-HIFU) or by mechanical disruption (mechanical (M)-HIFU). How different HIFU ablation techniques compare with respect to their antigen release profile, their activation of responder T cells, and their ability to synergize with immune stimuli remains to be elucidated.Methods and resultsHere, we compare the immunomodulatory effects of T-HIFU and M-HIFU ablation with or without the TLR9 agonist CpG in the ovalbumin-expressing lymphoma model EG7. M-HIFU ablation alone, but much less so T-HIFU, significantly increased dendritic cell (DC) activation in draining lymph nodes (LNs). Administration of CpG following T- or M-HIFU ablation increased DC activation in draining LNs to a similar extend. Interestingly, ex vivo co-cultures of draining LN suspensions from HIFU plus CpG treated mice with CD8+ OT-I T cells demonstrate that LN cells from M-HIFU treated mice most potently induced OT-I proliferation. To delineate the mechanism for the enhanced anti-tumor immune response induced by M-HIFU, we characterized the RNA, DNA and protein content of tumor debris generated by both HIFU methods. M-HIFU induced a uniquely altered RNA, DNA and protein profile, all showing clear signs of fragmentation, whereas T-HIFU did not. Moreover, western blot analysis showed decreased levels of the immunosuppressive cytokines IL-10 and TGF-β in M-HIFU generated tumor debris compared to untreated tumor tissue or T-HIFU.ConclusionCollectively, these results imply that M-HIFU induces a unique context of the ablated tumor material, enhancing DC-mediated T cell responses when combined with CpG.

Ultrasound-augmented cancer immunotherapy

“…18 In particular, considerable evidence has verified that M-HIFU can enhance systemic antitumor immunity and be a potential solution for treating advanced tumors and distant recurrence. [19][20][21][22] M-HIFU mechanically disrupts the tumor microenvironment (TME), which repolarizes tumor-associated macrophages (TAMs), enhances T-cell infiltration, and increases the accumulation of dendritic cells (DCs) in tumor. 20 Moreover, ultrasoundtargeted microbubble destruction (UTMD) has also emerged as a promising cancer immunotherapy treatment modality.…”

“…In the latest study, Adema's group 22 demonstrated that in situ mechanical tumor destruction by M-HIFU was capable of releasing unique tumor antigens and facilitating DC-induced T cell activation, resulting in enhanced antitumor immunity. They compared the immunomodulatory effects of T-HIFU and M-HIFU in an EG7 lymphoma expressing ovalbumin.…”

Risk factors for unresectable pancreatic cancer following high‐intensity focused ultrasound treatment

“…At the same time, the hyperthermia produced by the action of HIFU increases blood flow and vascular permeability, disrupt the stromal architecture, thus improving anti‐tumor effects 8 . HIFU also uses the cavitation and mechanical effect of ultrasound to increase vascular permeability, promote drugs penetration, 9 induce subcellular fragmentation, and trigger activation of cytotoxic T cells in other types of tumors 10–12 …”

Focused ultrasound ablation of melanoma with boiling histotripsy yields abscopal tumor control and antigen-dependent dendritic cell activation

“…Moreover, CD86 and PD-L1 expression on DCs increased 48 hr post-BH treatment in TDLNs of mice with EG.7-OVA lymphoma. When a toll-like receptor (TLR) agonist (cytidyl guanosyl [CpG]) was combined with BH, CD80, CD86, and PD-L1 expression increased compared to sham and compared to CpG − controls ( 19 ). In murine renal cell carcinoma, BH increases CD8 + T-cell infiltration ( 9 ).…”

“…While multiple forms of histotripsy exist [8], the current study is centered on so-called "boiling histotripsy" (BH), wherein high pressure, millisecond long, FUS pulses are deployed. BH beneficially modulates immune landscape [9][10][11][12][13][14][15][16] and cooperates with immunological checkpoint inhibitors to control tumor growth [13][14][15][16]. Of particular note, BH has been reported to modulate dendritic cell activation and migration [11,12,16], repolarize tumor-associate macrophages [13,15], and enhance T cell representation in tumors [11,[13][14][15][16].…”