Low Intensity Focused Ultrasound (LOFU)-mediated Acoustic Immune Priming and Ablative Radiation Therapy for in situ Tumor Vaccines

Abstract

Focal ablative therapies have been primarily used for local tumor ablation. However, they often fail to impact systemic disease. Here we propose the use of low intensity focused ultrasound (LOFU), a noninvasive, nontoxic, conformal therapy, to deliver acoustic stress to the tumor for immune priming. We demonstrate that LOFU significantly induces expression and cell surface localization of heat shock proteins in murine breast (4T1) and prostate adenocarcinoma (TPSA23) cancer cell lines. In vivo LOFU followed by ablative radiation therapy (RT) results in primary tumor cure, upregulation of a cytotoxic immune response and induction of immunological memory by inhibiting secondary tumor growth upon re-challenge with tumor cells. We, therefore, describe a regimen of a combination therapy with noninvasive, acoustic immune priming and ablative radiation therapy to generate an in situ tumor vaccine, induce CD8+ T cells against tumor-associated antigens and provide a viable oncologic treatment option for solid tumors.

Focused Ultrasound for Immunomodulation of the Tumor Microenvironment

“…Shorter treatment times of 2 min can also induce necrosis and antitumor immune responses mediated by CD8 + cells when 3-4 W/cm 2 ultrasound is combined with microbubbles (115). Finally, another recent study used shorter ultrasound treatment times of 1.5 s per spot to heat prostate tumors to 45˚C prior to radiotherapy to develop a T cell driven-in situ tumor vaccine (121). Although some preclinical and clinical studies can be found studying the antitumor effect of ultrasound-induced hyperthermia, more studies are needed to determine treatment parameters that will produce a specific immune response and whether these effects are superior to thermal ablation in certain cases.…”

Externally-Controlled Systems for Immunotherapy: From Bench to Bedside

“…Focused ultrasounds (FUs) can be also used as inductor for externally control of gene expression, penetrating with a depth of centimeters into tissues. Therapeutic FUs-controlled by Magnetic Resonance Imaging (MRI) have been applied into clinics for vasodilation, neuromodulation, heat-ablation of tumors and as an adjuvant therapy for drug, gene delivery (124) and tumor vaccination in situ (125). Low-energy focused ultrasounds (LO-FUs, with normal intensities of 0.1-2 W/cm 2 and frequencies of 0.5-3 MHz) generate rapid oscillating pressures that lead to non-invasive hyperthermia.…”

“…Low-energy focused ultrasounds (LO-FUs, with normal intensities of 0.1-2 W/cm 2 and frequencies of 0.5-3 MHz) generate rapid oscillating pressures that lead to non-invasive hyperthermia. In response, mechanical and thermal stresses are manifested transiently without killing the cells and several genes are upregulated such as heat-shock proteins that translocate from cytoplasm to cell surface (125). Based on this response, the use of heat-shock protein's (HSP) promoters have been used for local control gene expression in several models (126) but not for immunotherapy.…”

“…Moreover, HSP are translocated to membranes after LO-FUs exposition in cancer cells. This HSP complexes can activate natural killer cells, being interpreted as danger signals for DC activation and cross-presented for generated immunity (125). Whereas, this response is very desirable for tumor treatment for the generation of immune priming and activation of the TME, should be further studied in primary T cells, in order to analyze the worst scenario of a non-desirable immunogenicity against CAR-T cells that can compromise the persistence of the therapy.…”

Using nanoparticles forin situvaccination against cancer: mechanisms and immunotherapy benefits

“…For instance, low intensity FUS (LOFU; peak negative pressures from $2 to 5 MPa) modulates the expression and cellular distribution of HSPs family protein (e.g., HSP 60,70,and 90). This was shown to enhance radiotherapy outcomes of breast and prostate murine cancers [148]. In contrast, ablative FUS rapidly debulks tumor to release tumor antigens.…”