Inhibition of Walker-256 Tumor Growth by Combining Microbubble-Enhanced Ultrasound and Endostar.

OBJECTIVES: This research is to investigate the anti-tumor effects by combining anti-vascular effect of microbubble enhanced ultrasound (MEUS) mechanical destruction and anti-angiogenic effect of Endostar. METHODS: Rats bearing Walker-256 tumor were randomly divided into 4 groups treated by Endostar + MEUS combination, Endostar, MEUS or Sham ultrasound (US), respectively. MEUS was induced by Sonazoid microbubble and a focused therapeutic US device. Contrast-enhanced ultrasound (CEUS) was used to assess tumor perfusion before and after treatment. Microvessel density (MVD) was evaluated with immunohistochemical staining of CD31, CD34, and VEGFA. TUNEL assay was used to determine the apoptosis rate of tumor cells. RESULTS: Endostar + MEUS combined group induced the most reduced blood perfusion and most retarded tumor growth compared with other 3 groups. Decreased MVD was shown in Endostar + MEUS, Endostar and MEUS group, but the lowest MVD value was presented in the combined treatment group. Significant increase was observed in the combined therapy group and MEUS group. CONCLUSIONS: This study showed an improved anti-vascular and anti-angiogenic effect achieved by combining Endostar and MEUS, and may provide a new method potential for anti-tumor therapy.

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.

Effect of Microbubble-Enhanced Ultrasound on Radiofrequency Ablation of Rabbit Liver.

Microbubble-enhanced ultrasound (MEUS) can non-invasively disrupt and block liver blood perfusion. It may potentially overcome the heat sink effect during a thermal ablation and consequently enhance radiofrequency ablation (RFA) of the liver. We propose a new strategy combining RFA with MEUS. For ultrasound treatment, an 831-kHz air-backed focused transducer directed 400-cycle bursts at 4.3 MPa to the liver at a 9-Hz rate. The treatment was nucleated by a lipids microbubble forming MEUS. Eighteen surgically exposed rabbit livers were treated using MEUS combined with RFA; the other 32 livers were treated using MEUS (n = 14) or RFA (n = 18) alone and served as the controls. Contrast ultrasound imaging confirmed that MEUS treatment significantly reduced liver blood perfusion by cutting contrast peak intensities in half (44.7%-54.1%) without severe liver function damage. The ablated liver volume treated using MEUS combined with RFA was 2.8 times greater than that treated using RFA alone. In conclusion, RFA of the liver can be safely and greatly enhanced by combination with MEUS pre-treatment.