Enhancement Effect of Microbubble-Enhanced Ultrasound in Microwave Ablation in Rabbit VX2 Liver Tumors

Tumor perfusion enhancement by microbubbles ultrasonic cavitation reduces tumor glycolysis metabolism and alleviate tumor acidosis

The tumor microenvironment is increasingly acknowledged as a critical contributor to cancer progression, mediating genetic and epigenetic alterations. Beyond diverse cellular interactions from the microenvironment, physicochemical factors such as tumor acidosis also significantly affect cancer dynamics. Recent research has highlighted that tumor acidosis facilitates invasion, immune escape, metastasis, and resistance to therapies. Thus, noninvasive measurement of tumor acidity and the development of targeted interventions represent promising strategies in oncology. Techniques like contrast-enhanced ultrasound (CEUS) can effectively assess blood perfusion, while ultrasound-stimulated microbubble cavitation (USMC) has proven to enhance tumor blood perfusion. We therefore aimed to determine whether CEUS assesses tumor acidity and whether USMC treatment can modulate tumor acidity. Firstly, we tracked CEUS perfusion parameters in MCF7 tumor models and compared them with in vivo tumor pH recorded by pH microsensors. We found that the peak intensity and area under curve of tumor contrast-enhanced ultrasound correlated well with tumor pH. We further conducted USMC treatment on MCF7 tumor-bearing mice, tracked changes of tumor blood perfusion and tumor pH in different perfusion regions before and after the USMC treatment to assess its impact on tumor acidity and optimize therapeutic ultrasound pressure. We discovered that USMC with 1.0 Mpa significantly improved tumor blood perfusion and tumor pH. Furthermore, tumor vascular pathology and PGI2 assays indicated that improved tumor perfusion was mainly due to vasodilation rather than angiogenesis. More importantly, analysis of glycolysis-related metabolites and enzymes demonstrated USMC treatment can reduce tumor acidity by reducing tumor glycolysis. These findings support that CEUS may serve as a potential biomarker to assess tumor acidity and USMC is a promising therapeutic modality for reducing tumor acidosis.

Advances of ultrasound in tumor immunotherapy

Immunotherapy has become a revolutionary method for treating tumors, offering new hope to cancer patients worldwide. Immunotherapy strategies such as checkpoint inhibitors, chimeric antigen receptor T-cell (CAR-T) therapy, and cancer vaccines have shown significant potential in clinical trials. Despite the promising results, there are still limitations that impede the overall effectiveness of immunotherapy; the response to immunotherapy is uneven, the response rate of patients is still low, and systemic immune toxicity accompanied with tumor cell immune evasion is common. Ultrasound technology has evolved rapidly in recent years and has become a significant player in tumor immunotherapy. The introductions of high intensity focused ultrasound and ultrasound-stimulated microbubbles have opened doors for new therapeutic strategies in the fight against tumor. This paper explores the revolutionary advancements of ultrasound combined with immunotherapy in this particular field.

Enhancement of Tumor Perfusion and Antiangiogenic Therapy in Murine Models of Clear Cell Renal Cell Carcinoma Using Ultrasound-Stimulated Microbubbles

OBJECTIVE

To explore the effect of ultrasound-stimulated microbubble cavitation (USMC) on enhancing antiangiogenic therapy in clear cell renal cell carcinoma.

MATERIALS AND METHODS

We explored the effects of USMC with different mechanical indices (MIs) on tumor perfusion, 36 786-O tumor-bearing nude mice were randomly assigned into four groups: (i) control group, (ii) USMC0.25 group (MI = 0.25), (iii) USMC1.4 group (MI = 1.4) (iv) US1.4 group (MI = 1.4). Tumor perfusion was assessed by contrast-enhanced ultrasound (CEUS) before the USMC treatment and 30 min, 4h and 6h after the USMC treatment, respectively. Then we evaluated vascular normalization(VN) induced by low-MI (0.25) USMC treatment, 12 tumor-bearing nude mice were randomly divided into two groups: (i) control group (ii) USMC0.25 group. USMC treatment was performed, and tumor microvascular imaging and blood perfusion were analyzed by MicroFlow imaging (MFI) and CEUS 30 min after each treatment. In combination therapy, a total of 144 tumor-bearing nude mice were randomly assigned to six groups (n = 24): (i) control group, (ii) USMC1.4 group, (iii) USMC0.25 group, (iv) bevacizumab(BEV) group, (v) USMC1.4 +BEV group, (vi) USMC0.25 +BEV group. BEV was injected on the 6th, 10th, 14th, and 18th d after the tumors were inoculated, while USMC treatment was performed 24 h before and after every BEV administration. We examined the effects of the combination therapy through a series of experiments.

RESULTS

Tumor blood perfusion enhanced by USMC with low MI (0.25)could last for more than 6h, inducing tumor VN and promoting drug delivery. Compared with other groups, USMC0.25+BEV combination therapy had the strongest inhibition on tumor growth, led to the longest survival time of the mice.

CONCLUSION

The optimized USMC is a promising therapeutic approach that can be combined with antiangiogenic therapy to combat tumor progression.

Synergistic enhancement of cell death by triple combination therapy of docetaxel, ultrasound and microbubbles, and radiotherapy on PC3 a prostate cancer cell line

The application of ultrasound and microbubbles (USMB) has been shown to enhance both chemotherapy and radiotherapy. This study investigated the potential of triple combination therapy comprised of USMB, docetaxel (Taxotere: TXT) chemotherapy and XRT to enhance treatment efficacy. Prostate cancer (PC3) cells in suspension were treated with various combinations of USMB, chemotherapy and radiotherapy. Cells were treated with ultrasound and microbubbles (500 kHz pulse center frequency, 580 kPa peak negative pressure, 10 μs pulse duration, 60 s insonation time and 2% Definity microbubbles (v/v)), XRT (2 Gy), and Taxotere (TXT) at concentrations ranging from 0.001 to 0.1 nM for 5- and 120-minutes duration. Following treatment, cell viability was assessed using a clonogenic assay. Therapeutic efficiency of the combined treatments depended on chemotherapy and microbubble exposure conditions. Under the exposure conditions of the study, the triple combination therapy synergistically enhanced clonogenic cell death compared to single and double combination therapy. Cell viability of ∼2% was achieved with the triple combination therapy corresponding to ∼29, ∼37, and ∼38 folds decrease compared to XRT (57%), USMB (74%) and TXT (76%) alone conditions, respectively. In addition, the triple combination therapy decreased cell viability by ∼29, ∼19- and ∼11 folds compared to TXT_2hr + USMB (58%), TXT_2hr + XRT (37%), and USMB + XRT (22%), respectively. The in vivo PC3 tumours showed that USMB significantly enhanced cell death through detection of apoptosis (TUNEL) with both TXT and TXT + XRT. The study demonstrated that the triple combination therapy can significantly enhance cell death in prostate cancer cells both in vitro and in vivo under relatively low chemotherapy and ionizing radiation doses.

Extended Focal Ablation of Localized Prostate Cancer With High-Frequency Irreversible Electroporation: A Nonrandomized Controlled Trial

IMPORTANCE

Focal therapy of prostate cancer must balance the oncologic outcome and functional outcome. High-frequency irreversible electroporation (H-FIRE) can destroy cancer cells while selectively preserving surrounding nerves and blood vessels, but no clinical trials have been conducted, to our knowledge.

OBJECTIVE

To evaluate the efficacy and safety of H-FIRE in the treatment of localized prostate cancer (PCa).

DESIGN, SETTING, AND PARTICIPANTS

This was a single-group, objective performance criteria, nonrandomized controlled trial. Recruitment began on May 2, 2018, and ended March 27, 2019. The follow-up duration was 6 months. This was a multicenter trial conducted at 4 tertiary teaching hospitals in China. Patients with low or intermediate risk of biochemical recurrence of localized and locally advanced PCa were eligible. Key inclusion criteria were serum prostate-specific antigen (PSA) level less than 20 ng/mL, clinical stage of T2c or less, and Gleason score of 7 or less. Data were analyzed from January 20 to February 20, 2021.

INTERVENTION

H-FIRE ablation of all lesions identified with biopsy.

MAIN OUTCOMES AND MEASURES

The primary end point was 6-month clinically significant PCa (csPCa), which was defined as any biopsy core with Gleason score of greater than or equal to 7, or Gleason score of 6 plus maximum cancer core length of greater than 3 mm or an increase from the original cancer burden. Secondary outcomes were calculated in patients who actually received H-FIRE treatment.

RESULTS

A total of 117 patients (median [IQR] age, 67 [62-73] years) were recruited from 4 centers, and 109 patients (27 [24.8%] low risk and 82 [75.2%] intermediate risk) actually received H-FIRE. Median (IQR) PSA level was 9.0 (6.0-12.7) ng/mL. Among the 100 patients who underwent biopsy at 6 months, the 6-month csPCa rate was 6.0% (95% CI, 2.2%-12.6%; P < .001; 1 in the treatment zone and 5 outside the treatment zone). Superiority criteria vs the historical control of 20% was achieved. PCa was detected in 14 patients, with a Gleason score of 7 in 2 patients and 6 in the remaining 12 patients. At 6 months, median (IQR) PSA level was 1.08 (0.4-3.2) ng/mL, median (IQR) International Prostate Symptom Score was 4.5 (2.0-9.5), and median (IQR) International Index of Erectile Function 5 score was 2.0 (0.5-12.5). Superiority vs the 20% historical control was also met in the subgroup analysis that only included the 57 patients with Gleason score of 7 at baseline (3.5% 6-month csPCa; 95% CI, 0.4%-12.1%).

CONCLUSIONS AND RELEVANCE

The rate of 6-month csPCa with H-FIRE ablation was lower than the historical control using other energy platforms.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03838432.

Ultrasound and Nanomedicine for Cancer-Targeted Drug Delivery: Screening, Cellular Mechanisms and Therapeutic Opportunities

Cancer is a disease characterized by abnormal cell growth. According to a report published by the World Health Organization (WHO), cancer is the second leading cause of death globally, responsible for an estimated 9.6 million deaths in 2018. It should be noted that ultrasound is already widely used as a diagnostic procedure for detecting tumorigenesis. In addition, ultrasound energy can also be utilized effectively for treating cancer. By filling the interior of lipospheres with gas molecules, these particles can serve both as contrast agents for ultrasonic imaging and as delivery systems for drugs such as microbubbles and nanobubbles. Therefore, this review aims to describe the nanoparticle-assisted drug delivery system and how it can enhance image analysis and biomedicine. The formation characteristics of nanoparticles indicate that they will accumulate at the tumor site upon ultrasonic imaging, in accordance with their modification characteristics. As a result of changing the accumulation of materials, it is possible to examine the results by comparing images of other tumor cell lines. It is also possible to investigate ultrasound images for evidence of cellular effects. In combination with a precision ultrasound imaging system, drug-carrying lipospheres can precisely track tumor tissue and deliver drugs to tumor cells to enhance the ability of this nanocomposite to treat cancer.

Enhanced HIFU Theranostics with Dual-Frequency-Ring Focused Ultrasound and Activatable Perfluoropentane-Loaded Polymer Nanoparticles

High-intensity focused ultrasound (HIFU) has been widely used in tumor ablation in clinical settings. Meanwhile, there is great potential to increase the therapeutic efficiency of temporary cavitation due to enhanced thermal effects and combined mechanical effects from nonlinear vibration and collapse of the microbubbles. In this study, dual-frequency (1.1 and 5 MHz) HIFU was used to produce acoustic droplet vaporization (ADV) microbubbles from activatable perfluoropentane-loaded polymer nanoparticles (PFP@Polymer NPs), which increased the therapeutic outcome of the HIFU and helped realize tumor theranostics with ultrasound contrast imaging. Combined with PFP@Polymer NPs, dual-frequency HIFU changed the shape of the damage lesion and reduced the acoustic intensity threshold of thermal damage significantly, from 216.86 to 62.38 W/cm². It produced a nearly 20 °C temperature increase in half the irradiation time and exhibited a higher tumor inhibition rate (84.5% ± 3.4%) at a low acoustic intensity (1.1 MHz: 23.77 W/cm²; 5 MHz: 0.35 W/cm²) in vitro than the single-frequency HIFU (60.2% ± 11.9%). Moreover, compared with the traditional PFP@BSA NDs, PFP@Polymer NPs showed higher anti-tumor efficacy (81.13% vs. 69.34%; * p < 0.05) and better contrast-enhanced ultrasound (CEUS) imaging ability (gray value of 57.53 vs. 30.67; **** p < 0.0001), probably benefitting from its uniform and stable structure. It showed potential as a highly efficient tumor theranostics approach based on dual-frequency HIFU and activatable PFP@Polymer NPs.

Value of 18F-FDG PET/MRI in the early evaluation of treatment response following radiofrequency ablation of liver cancer in a rabbit model

PURPOSE

To test the hypothesis that ¹⁸F-fluorodeoxyglucose positron emission tomography and MRI (18F-FDG PET/MRI) can detect early residual tumor following radiofrequency ablation (RFA) of liver cancer using a VX2 tumor model.

METHODS

Twenty-four rabbits with VX2 liver tumors were randomly divided into three groups (n = 8/group): group 1 without RFA treatment, group 2 with complete ablation, and group 3 with partial ablation. ¹⁸F-FDG PET/MRI scan was obtained in three animal groups within 2 hours post-RFA. The maximum standardized uptake value (SUVmax) of non-treated liver tumor, benign peri-ablational enhancement (BPE), residual tumor, ablated tumor, adjacent liver parenchyma, and mean SUV of normal liver were measured, respectively. The ratios of SUVmax for these targets to mean SUV of normal liver (TNR) were calculated and statistically compared.

RESULTS

The mean TNR of non-treated liver tumors in group 1 was significantly greater than that of adjacent liver parenchyma (8.68 ± 0.71 vs 1.89 ± 0.26, p < 0.001). In group 2, the mean TNR of BPE was significantly greater than that of adjacent liver parenchyma (2.85 ± 0.20 vs 1.86 ± 0.25, p < 0.001). In group 3, the mean TNR of residual tumor was significantly greater than that of BPE (8.64 ± 0.59 vs 2.78 ± 0.23, p < 0.001), which was significantly greater than that of completely ablated tumor (2.78 ± 0.23 vs 0.50 ± 0.06, p < 0.001).

CONCLUSION

¹⁸F-FDG PET/MRI may serve as a promising imaging tool for early detection of viable residual tumors due to incomplete tumor ablation.

Tumor perfusion enhancement by ultrasound stimulated microbubbles potentiates PD-L1 blockade of MC38 colon cancer in mice

Cancer immunotherapy holds tremendous promise as a strategy for eradicating solid tumors, and its therapeutic effect highly relies on sufficient CD8⁺ T cells infiltration. Here, we demonstrate that ultrasound stimulated microbubble cavitation (USMC) promotes tumor perfusion, thereby increasing CD8⁺ T cells infiltration and anti-PD-L1 antibody delivery, then further enhancing the PD-L1 blockade of MC38 colon cancer in mice. Firstly, we optimized the mechanic index (MI) of ultrasound, and found that USMC with MI of 0.4 (equal to peak negative pressure of 0.8 MPa) significantly improved the peak intensity and area under curve of tumor contrast-enhanced ultrasound. Also, flow cytometry exhibited higher percentage of infiltrating CD8⁺ T cells in the USMC (MI = 0.4)-treated tumors than that of the control. We further explored the combination therapy of optimized USMC with anti-PD-L1 antibody. The combination therapy enhanced tumor perfusion and even led to the tumor vascular normalization. More importantly, flow cytometry showed that the combination not only increased the percentage and absolute number of tumor infiltrating CD8⁺ T cells, but also promoted the expression of Ki67 as well as the secretions of IFN γ and granzyme B, therefore, the combination therapy achieved greater tumor growth inhibition and longer survival than that of the monotherapies. These suggest that USMC is a promising therapeutic modality for combining immune checkpoint blockade against solid tumors.

Remotely Activated Nanoparticles for Anticancer Therapy

Cancer has nowadays become one of the leading causes of death worldwide. Conventional anticancer approaches are associated with different limitations. Therefore, innovative methodologies are being investigated, and several researchers propose the use of remotely activated nanoparticles to trigger cancer cell death. The idea is to conjugate two different components, i.e., an external physical input and nanoparticles. Both are given in a harmless dose that once combined together act synergistically to therapeutically treat the cell or tissue of interest, thus also limiting the negative outcomes for the surrounding tissues. Tuning both the properties of the nanomaterial and the involved triggering stimulus, it is possible furthermore to achieve not only a therapeutic effect, but also a powerful platform for imaging at the same time, obtaining a nano-theranostic application. In the present review, we highlight the role of nanoparticles as therapeutic or theranostic tools, thus excluding the cases where a molecular drug is activated. We thus present many examples where the highly cytotoxic power only derives from the active interaction between different physical inputs and nanoparticles. We perform a special focus on mechanical waves responding nanoparticles, in which remotely activated nanoparticles directly become therapeutic agents without the need of the administration of chemotherapeutics or sonosensitizing drugs.