Sononeoperfusion: a new therapeutic effect to enhance tumour blood perfusion using diagnostic ultrasound and microbubbles.

BACKGROUND: Hypoperfusion or resultant hypoxia in solid tumours is a main reason for therapeutic resistance. Augmenting the blood perfusion of hypovascular tumours might improve both hypoxia and drug delivery. Cavitation is known to result in microstreaming and sonoporation and to enhance drug diffusion into tumours. Here, we report the ability to enhance both tumour blood perfusion and doxorubicin (Dox) delivery using a new sononeoperfusion effect causing a cavitation effect on tumour perfusion in subcutaneous Walker-256 tumours of rats using ultrasound stimulated microbubble (USMB). METHODS: To induce the sononeoperfusion effect, USMB treatment was performed with a modified diagnostic ultrasound (DUS) system and SonoVue® microbubbles. The therapeutic pulse was operated with a peak negative pressure of 0.26 to 0.32 MPa and a pulse repetition frequency (PRF) of 50 Hz to 2 kHz. Contrast-enhanced ultrasound (CEUS) was used for tumour perfusion assessment. RESULTS: The USMB treatment of 0.26 MPa and 1 kHz could significantly enhance tumour perfusion with a 20.29% increase in the CEUS peak intensity and a 21.42% increment in the perfusion area for more than 4 hours (P < 0.05). The treatment also increased Dox delivery to tumours by approximately 3.12-fold more than that of the control (P < 0.05). Furthermore, ELISAs showed that vasodilators and inflammatory factors increased 4 hours after treatment (P < 0.05), suggesting that the inflammatory response plays an important role in the sononeoperfusion effect. CONCLUSION: The USMB-induced sononeoperfusion effect could significantly enhance the blood perfusion of Walker-256 tumours and promote drug delivery. It might be a novel physical method for overcoming the therapeutic resistance of hypoperfused or hypoxic tumours.

Mechanical destruction using a minimally invasive Ultrasound Needle induces anti-tumor immune responses and synergizes with the anti-PD-L1 blockade.

Immune checkpoint inhibitors (ICIs) have been widely used in treating various tumors; however, the objective response rate of ICIs is less than 40%. In this study, we attempted to induce anti-tumor immune responses using an improved ultrasonic horn device, Ultrasound Needle (UN). We tested its synergistic anti-tumor efficacy with an anti-PD-L1 antibody in a mouse tumor model. Under different parameters, UN treatment selectively induced mechanical destruction and thermal ablation effects on tumor tissues. The mechanical destruction effect of UN treatment increased the infiltration of CD8+ T cells in tumors and relieved the immunosuppressive tumor microenvironment. It also induced systemic anti-tumor immune responses and enhanced the therapeutic efficacy of the anti-PD-L1 antibody in both local and abscopal tumors. The mechanical destruction effect of UN treatment resulted in the release of damage-associated molecular patterns and promoted dendritic cells (DCs)-based antigen presentation. Depletion of DCs or CD8+ T cells eliminated the anti-tumor immune responses induced by UN treatment and weakened the synergistic anti-tumor efficacy with anti-PD-L1 antibody. Therefore, minimally invasive UN may provide a new therapeutic modality for ultrasound-assisted immunotherapy.

Ultrasound-Targeted Microbubble Destruction Alleviates Immunosuppression Induced by CD71+ Erythroid Progenitor Cells and Promotes PDL-1 Blockade Immunotherapy in the Lewis Lung Cancer Model.

The CD71+ erythroid progenitor cells (CECs) exhibit distinctive immunosuppressive properties and regulate antitumor immunity to enable tumor growth. We presented a novel and non-invasive approach to improving immunity by targeting the splenic CECs via sonoporation generated by ultrasound-targeted microbubble destruction (UTMD). The systematic immunity enhanced by the reduction of PDL-1-expressing CECs also benefits the PDL-1 blockade therapy. In the Lewis lung cancer (LLC) model, the study group was treated by UTMD for 10 min at the splenic area with or without anti-mouse PDL-1 intraperitoneal injection. The frequency of splenic CEC, lymphocyte, and cytokine production was analyzed by flow cytometry. Serum interleukin-2 (IL-2) was tested by ELISA. Tumor volume was evaluated by two-dimensional ultrasound. The UTMD treatment consisted of ultrasound sonication and Sonazoid™ microbubble injection through the caudal vein. The mechanic index (MI) of ultrasound was set between 0.98 and 1.03. The results showed a significant reduction of splenic CECs and increased frequency of CD8+ T cells treated by UTMD treatment in the late-stage tumor. Tumor growth could be inhibited by UTMD combined with PDL-1 blockade therapy. The frequencies of interferon-γ (IFN-γ) producing CD8+ and CD4+ T cells were significantly increased after being treated by the combination of UTMD and PDL-1 blockade, while the reactive oxygen species (ROS) production and the fraction of the TGF-ß-producing CD11b+ cells were significantly decreased. These preliminary findings suggest that UTMD enhances immune response and facilitates PDL-1 blockade therapy by targeting immunosuppressive CECs in the spleen. Our study provides new aspects and possibilities for treating cancer-related infection and tumor control in oncology.

Ultrasound-Targeted Microbubble Destruction Accelerates Angiogenesis and Ameliorates Left Ventricular Dysfunction after Myocardial Infarction in Mice.

Failure of coronary recanalization within 12 h or no flow in the myocardium after percutaneous coronary intervention is associated with high mortality from myocardial infarction, and insufficient angiogenesis in the border zone results in the expansion of infarct area. In this study, we examined the effects of ultrasound-targeted microbubble destruction (UTMD) on angiogenesis and left ventricular dysfunction in a mouse model of myocardial infarction. Fifty-four mice with MI were treated with no UTMD, ultrasound (US) alone or UTMD four times (days 1, 3, 5 and 7), and another 18 mice underwent sham operation and therapy. Therapeutic US was generated with a linear transducer connected to a commercial diagnostic US system (VINNO70). UTMD was performed with the VINNO70 at a peak negative pressure of 0.8 MPa and lipid microbubbles. Transthoracic echocardiography was performed on the first and seventh days. The results indicated that UTMD decreased the infarct size ratio from 78.1 ± 5.3% (untreated) to 43.3 ± 6.4%, accelerated angiogenesis and ameliorated left ventricular dysfunction. The ejection fraction increased from 25.05 ± 8.52% (untreated) to 42.83 ± 9.44% (UTMD). Compared with that in other groups, expression of vascular endothelial growth factor and endothelial nitric oxide synthase and release of nitric oxide were significantly upregulated after UTMD treatment, indicating angiogenesis. Therefore, UTMD is a potential physical approach in the treatment of myocardial infarction.

Effect of diagnostic ultrasound and microbubble-enhanced chemotherapy on metastasis of rabbit VX2 tumor.

PURPOSE: Ultrasound-targeted microbubble destruction (UTMD) has been widely applied to enhance chemotherapy of tumors, yet few studies have focused on the metastatic potential induced by UTMD. This study aimed to explore the metastasis of VX2 tumors after treatment with UTMD and chemotherapy. METHODS: Forty-four New Zealand rabbits bearing subcutaneous VX2 tumors were enrolled for the treatment of UTMD with chemotherapy. For UTMD, the tumors were insonated using two pulsing protocols of diagnostic ultrasound (DUS, VINNO and ECARE) with a mechanical index (MI) of 0.29-0.33, tone burst of 8.0 cycles, and frequencies of 3-4 MHz. A total dose of 2 ml SonoVue® was injected intermittently during 10-min UTMD exposure. The combination therapy was treated using doxorubicin (DOX, 2 mg/kg) and DUS, while the tumors treated using DOX only served as the control. Tumor size was measured using the tumor volume formula. Survival time was observed until animal death or the end of the study (120 days). Specific organs (lung, liver, kidney, and brain) were removed for metastatic evaluation. RESULTS: There were no statistical differences in overall metastasis classification and individual organ metastases among all groups (P > 0.05). The tumor growth rate only showed inhibition on the 5th day (P < 0.01). The survival time did not demonstrate any significant difference between UTMD and chemotherapy only (P > 0.05). CONCLUSIONS: UTMD using long-pulse DUS with commercial microbubbles did not pose a risk of metastasis enhancement in DOX chemotherapy.