Inhibitory effects of subcutaneous tumors in nude mice mediated by low-frequency ultrasound and microbubbles

A transducer positioning method for transcranial focused ultrasound treatment of brain tumors

Purpose

As a non-invasive method for brain diseases, transcranial focused ultrasound (tFUS) offers higher spatial precision and regulation depth. Due to the altered path and intensity of sonication penetrating the skull, the focus and intensity in the skull are difficult to determine, making the use of ultrasound therapy for cancer treatment experimental and not widely available. The deficiency can be effectively addressed by numerical simulation methods, which enable the optimization of sonication modulation parameters and the determination of precise transducer positioning.

Methods

A 3D skull model was established using binarized brain CT images. The selection of the transducer matrix was performed using the radius positioning (RP) method after identifying the intracranial target region. Simulations were performed, encompassing acoustic pressure (AP), acoustic field, and temperature field, in order to provide compelling evidence of the safety of tFUS in sonication-induced thermal effects.

Results

It was found that the angle of sonication path to the coronal plane obtained at all precision and frequency models did not exceed 10° and 15° to the transverse plane. The results of thermal effects illustrated that the peak temperatures of tFUS were 43.73°C, which did not reach the point of tissue degeneration. Once positioned, tFUS effectively delivers a Full Width at Half Maximum (FWHM) stimulation that targets tumors with diameters of up to 3.72 mm in a one-off. The original precision model showed an attenuation of 24.47 ± 6.13 mm in length and 2.40 ± 1.42 mm in width for the FWHM of sonication after penetrating the skull.

Conclusion

The vector angles of the sonication path in each direction were determined based on the transducer positioning results. It has been suggested that when time is limited for precise transducer positioning, fixing the transducer on the horizontal surface of the target region can also yield positive results for stimulation. This framework used a new transducer localization method to offer a reliable basis for further research and offered new methods for the use of tFUS in brain tumor-related research.

Low-frequency ultrasound irradiation increases paclitaxel-induced sarcoma cells apoptosis and facilitates the transmembrane delivery of drugs

Sarcoma is a malignant tumor derived from interstitial tissues and requires comprehensive treatment including chemotherapy. Paclitaxel (PTX) is an active agent against sarcoma, but its effect is not sufficiently acceptable and needs to be improved. Low-frequency ultrasound (LFU) has been documented to improve the efficacy of drugs by inducing reversible changes in membrane permeability; however, the effects of the combined use of LFU and PTX for sarcoma tumors remain unclear and warrant further investigation. We investigated the effects of 30 kHz LFU treatment combined with PTX on sarcoma cells A-204 and HT-1080 by analyzing in vitro apoptosis and cell growth inhibition rates, and determined their antitumor effects by examining tumor weights with or without LFU in the S180 sarcoma xenograft model. Drug concentrations in the subcutaneous tumors were measured using high performance liquid chromatography (HPLC). LFU combined with PTX significantly induced cell apoptosis, and blocked the cell cycle of sarcoma cells in G2/M phase, and furthermore, inhibited the activation of JAK2/STAT3 signaling pathway. Meanwhile, LFU combined with PTX inhibited the expression of PD-L1 in vitro, suggesting the potential of enhanced antitumor immunity by this treatment. LFU combined with PTX significantly inhibited the growth of S180 tumors transplanted subcutaneously in Institute of Cancer Research (ICR) mice, and its enhanced effect may be associated with increased local concentrations of PTX in tumor tissues in vivo, with no significant adverse subsequences on body weight observed. We conclude that the combination of LFU and PTX has synergistic antitumor effects and is a candidate for subcutaneous treatment of sarcoma by further increasing the intracellular concentration of PTX.

Can ultrasound irradiation be a therapeutic option for prostate cancer?

BACKGROUND

Focal therapies for prostate cancer (PC) can reduce adverse events and do not lead to androgen-independent progression. Ultrasound could be used for cancer treatments if the repetition frequency is fitted to the purpose. We investigated the possible therapeutic effect of ultrasound irradiation on PC cells.

MATERIALS AND METHODS

We irradiated two PC cell lines, androgen-dependent LNCaP and -independent PC-3 with ultrasound (3.0 W/cm² , 3 MHz, irradiation time rate: 20%) for 2 minutes for 1 day or 3 consecutive days at a repetition frequency of 1, 10, or 100 Hz in vitro. Cell proliferation and apoptosis were determined after irradiation.

RESULTS

Cell proliferation of PC-3 was significantly inhibited after 1 day (P < .0001) and 3 days (P < .0001) of 10 Hz ultrasound irradiation, and that of LNCaP after 1 day (P < .0001) and 3 days (P < .0001) of irradiation. LNCaP was more sensitive to ultrasound at both lower and higher cell density but PC-3 was only sensitive at a lower cell density (P < .01). Irradiation with 10 Hz ultrasound-induced significantly more PC-3 apoptotic cells than control (1 day, P = .0137; 3 days, P = .0386) rather than irradiation with 1 Hz. Apoptosis via caspase-3 was induced at 10 Hz in 1-day (P < .05) irradiation in both cell lines.

CONCLUSIONS

Ultrasound irradiation with even 1 day of 10 Hz significantly inhibited cell proliferation in both LNCaP and PC-3, especially by the remarkable induction of apoptosis in vitro. Our study indicated that ultrasound irradiation can be a therapeutic option for PC and further studies in vivo will be undertaken.

Ultrasound cavitation enhanced chemotherapy: In vivo research and clinical application

IMPACT STATEMENT

The novelty of this research is that we used ultrasound cavitation to enhance the effects of chemotherapy in the subcutaneous and orthotopic hepatic carcinomas in nude mice. Case reports of the effects of the targeting ultrasound cavitation and chemotherapy on malignant tumors in clinical patients were also examined. We found that low-frequency ultrasound cavitation combined with chemotherapy is effective in the inhibition of tumor growth to some extent.

Advances in low-frequency ultrasound combined with microbubbles in targeted tumor therapy

The development of low-frequency ultrasound imaging technology and the improvement of ultrasound contrast agent production technology mean that they play an increasingly important role in tumor therapy. The interaction between ultrasound and microbubbles and their biological effects can transfer and release microbubbles carrying genes and drugs to target tissues, mediate the apoptosis of tumor cells, and block the embolization of tumor microvasculature. With the optimization of ultrasound parameters, the development of targeted microbubbles, and the emergence of various composite probes with both diagnostic and therapeutic functions, low-frequency ultrasound combined with microbubble contrast agents will bring new hope for clinical tumor treatment.

Clinical study of ultrasound and microbubbles for enhancing chemotherapeutic sensitivity of malignant tumors in digestive system

Objective

To explore the safety of ultrasound and microbubbles for enhancing the chemotherapeutic sensitivity of malignant tumors in the digestive system in a clinical trial, as well as its efficacy.

Methods

From October 2014 to June 2016, twelve patients volunteered to participate in this study. Eleven patients had hepatic metastases from tumors of the digestive system, and one patient had pancreatic carcinoma. According to the mechanical index (MI) in the ultrasound field, patients were classified into four groups with MIs of 0.4, 0.6, 0.8 and 1.0. Within half an hour after chemotherapy, patients underwent ultrasound scanning with ultrasound microbubbles (SonoVue) to enhance the efficacy of chemotherapy. All adverse reactions were recorded and were classified in 4 grades according to the Common Terminology Criteria for Adverse Events version 4.03 (CTCAE V4.03). Tumor responses were evaluated by the Response Evaluation Criteria in Solid Tumors version 1.1 criteria. All the patients were followed up until progression.

Results

All the adverse reactions recorded were level 1 or level 2. No local pain occurred in any of the patients. Among all the adverse reactions, fever might be related to the treatment with ultrasound combined with microbubbles. Six patients had stable disease (SD), and one patient had a partial response (PR) after the first cycle of treatment. At the end of follow-up, tumor progression was restricted to the original sites, and no new lesions had appeared.

Conclusions

Our preliminary data showed the potential role of a combined treatment with ultrasound and microbubbles in enhancing the chemotherapeutic sensitivity of malignant tumors of the digestive system. This technique is safe when the MI is no greater than 1.0.

Spiral computed tomography evaluation of rabbit VX2 hepatic tumors treated with 20 kHz ultrasound and microbubbles

The aim of the present study was to explore the therapeutic effect of 20 kHz ultrasound (US) and microbubbles (MBs) on rabbit VX2 liver tumors by spiral computed tomography (CT) scanning. A total of 16 New Zealand rabbits with hepatic VX2 tumors were divided into four groups: Control, MB, low-frequency US and US + MB. The treatment effect was evaluated by spiral CT scanning prior to, during and following treatment (at 0 weeks and the end of 1 and 2 weeks). The tumor growth rate was recorded. The specimens of VX2 tumors were collected for histological examination and transmission electron microscopy (TEM). No significant differences were observed between tumor areas measured by CT and pathology after 2-week treatment (P>0.05). The mean tumor growth rates in the control, MB, US and US + MB groups after 2 weeks of treatment were 385±21, 353±12, 302±14 and 154±9%, respectively (P<0.05, US + MB vs. the other three groups). Hematoxylin and eosin staining in the US + MB group revealed coagulation necrosis, interstitial hemorrhage and intravascular thrombosis. In the control, MB and US groups, tumor cells exhibited clear nuclear hyperchromatism. TEM of US + MB revealed vascular endothelial cell wall rupture, widened endothelial cell gaps, interstitial erythrocyte leakage and microvascular thrombosis, while intact vascular endothelial cells and normal erythrocytes in the tumor vessels were observed in the control, MB and US groups. A combination of 20 kHz US and MBs may effectively inhibit rabbit VX2 tumors. Spiral CT scanning is an ideal method to evaluate the US treatment on rabbit tumors.

Low-frequency ultrasound-mediated microvessel disruption combined with docetaxel to treat prostate carcinoma xenografts in nude mice: A novel type of chemoembolization

The aim of the present study was to investigate whether low-frequency ultrasound (US)-mediated microvessel disruption combined with docetaxel (DTX) can be used as a novel type of chemoembolization. Mice were assigned to four groups: i) The USMB group, treated with low-frequency US combined with microbubbles (USMB); ii) the DTX group, treated with DTX; iii) the USMB + DTX group, treated with combined therapy; and iv) the control group, which was untreated. Immediately after the first treatment, the average peak intensity (API) on contrast-enhanced US was calculated, and tumors were excised for hematoxylin and eosin (HE) staining. At 2 weeks post-treatment, the tumor volumes and wet weights were calculated, and tumors were excised for immunohistochemistry to calculate apoptotic index (AI), proliferative index (PI) and microvessel density (MVD) values. Immediately after the first treatment, in the DTX and control groups, the tumors demonstrated abundant perfusion enhancement, while in the USMB + DTX and USMB groups, blood perfusion of the tumors was interrupted. Compared with that of the control group, the API was significantly lower in the USMB + DTX USMB groups (all P<0.001). HE staining showed that tumor microvasculature was disrupted into flaky hematomas and severely dilated microvessels in the USMB + DTX and USMB groups. In the DTX and control groups, there was no distinct evidence of the disruption and dilation of blood microvessels. At the end of the treatment, the mean tumor inhibition ratio was 73.33, 46.67 and 33.33% for the USMB + DTX, DTX and USMB groups, respectively. The USMB + DTX group had the highest AI, and the lowest PI and MVD compared with the other groups, although the difference between the USMB + DTX and DTX groups with regard to PI and MVD was not significant (USMB + DTX vs. DTX group, P=0.345 and P=0.059, respectively). In conclusion, as a novel type of chemoembolization, USMB combined with DTX is more effective than USMB or DTX alone in inhibiting tumor growth via the enhancement of apoptosis, and the suppression of proliferation and angiogenesis.

Low-frequency and low-intensity ultrasound-mediated microvessel disruption enhance the effects of radiofrequency ablation on prostate cancer xenografts in nude mice

The aim of the present study was to examine the impact of low-frequency, low-intensity ultrasound (US)-stimulated microbubbles (USMB) on radiofrequency ablation (RFA) in the treatment of nude mice with human prostate cancer xenografts. The tumor‑bearing nude mice were divided into three groups: The USMB+RFA group was treated with USMB immediately followed by RFA, the RFA group was treated with RFA alone, and the control group remained untreated. The animals underwent enhanced US to calculate the tumor volumes, ablation volumes and ablation rates. Subsequently, the tumors were excised for hematoxylin and eosin staining, to identify necrosis in the tumors following the treatments, and immunohistochemical staining, to analyze the apoptotic index (AI), proliferative index (PI) and microvessel density (MVD) at 1, 4 and 7 days post-treatment. Each group contained five mice at each time‑point. Necrosis was apparent in the center of the tumors in the treatment groups. Ablation lesion volumes of the USMB+RFA group were larger than those in the RFA group at 1 and 4 days post‑treatment (P=0.002 and P=0.022, respectively), and the ablation rates of the USMB+RFA group were significantly higher, compared with the RFA group at the three time‑points (all P<0.001). There were fewer apoptotic cells and more proliferative cells in the RFA group, compared with the control group 1,4 and 7 days post‑treatment (all P<0.05). The AI of the USMB+RFA group was higher than that of the control group and lower than that of the RFA group 1 day post-treatment (P=0.034 and P=0.016, respectively). The PI of the USMB+RFA group was lower than that of the control group and higher than that of the RFA group 4 and 7 days post-treatment (all P<0.05). No significant differences were observed in MVD among the three groups throughout the experiment. In conclusion, exposure to USMB prior to RFA produced larger volumes of ablation, compared with treatment with RFA alone, and increased AI and reduced PI in the residual carcinoma cells induced by RFA.

The effects of percutaneous ethanol injection followed by 20-kHz ultrasound and microbubbles on rabbit hepatic tumors

OBJECTIVE

Low-frequency ultrasound (US) in combination with microbubbles (MBs) is able to inhibit the growth of VX2 rabbit liver tumors. In this study, we investigated the feasibility of using percutaneous ethanol injection (PEI) followed by low-frequency ultrasound and microbubbles (USMB) to inhibit VX2 tumor growth.

METHODS

Eighteen New Zealand rabbits with hepatic VX2 tumors were divided into three groups: PEI, low-frequency ultrasound and MBs followed by PEI (USMB + PEI), and PEI followed by USMB (PEI + USMB). PEI was performed by ultrasound-guided injection of 95% anhydrous alcohol into internal liver tumors in rabbits twice a week for 2 weeks. The US parameters were 20 kHz, 2 W/cm(2), 40% duty cycle, 5 min, and once every other day for 2 weeks. Magnetic resonance imaging (MRI) was used to observe tumors before and after treatment, to examine changes in the tumors, and to measure the diameters of the tumors. All animals were followed up for 180 days after tumor implantation. Autopsy was performed at the end of the scheduled follow-up or immediately after death. Anatomically observed metastatic sites included the liver, lung, abdomen, and pelvic cavity. The survival time of all rabbits was recorded.

RESULTS

After 4 weeks of treatment, on MRI, the tumor diameters in the PEI, USMB + PEI, and PEI + USMB groups were 8.33 ± 1.83, 19 ± 2.61, and 4.5 ± 1.22 mm, respectively. There was a significant difference in tumor size indicated by MRI in the three groups. Tumor size was smaller in the PEI + USMB group than in the PEI and USMB + PEI groups, with t = 4.54, p = 0.0062, and t = 16.38, p < .0001, respectively. The PEI + USMB group showed the fewest metastasis sites (χ(2) = 11.7333, p = 0.0194) and the longest survival period (χ(2) = 7.448, p = 0.0241).

CONCLUSION

Percutaneous ethanol injection followed by low-frequency ultrasound and microbubbles can be effective in inhibiting rabbit liver tumors and prolonging survival time.

Treatment of hepatic carcinoma by low-frequency ultrasound and microbubbles: A case report

In vitro and in vivo studies have identified that low-frequency ultrasound (US) and microbubbles (MBs) mediate tumor inhibitory effects. However, the application of US in the clinical setting remains unclear. The aim of the present study was to investigate the clinically therapeutic effect of 20 kHz US in combination with MBs for the treatment of hepatic carcinoma. A 71-year-old male with a hepatic malignant tumor was admitted to Nantong University Affiliated Nantong Tumor Hospital (Nantong, China). The patient was subsequently sonicated with 20 kHz US and MBs over a period of five days. The low-frequency US parameters were set at 20 kHz, 2 W/cm², duty cycle 40% (on 2 sec, off 3 sec) for a duration of 5 min each day for a total of five days. Computed tomography (CT), contrast-enhanced US (CEUS) and carbohydrate antigen 19-9 (CA19-9) tests were performed to evaluate the therapeutic effects. Although the tumor size increased marginally on CT from 5.4 to 5.6 cm after US treatment, the intensity and enhanced-areas on the CT scans and CEUS decreased. The abdominal lymph node decreased in size, from 2.2 to 1.9 cm, and CA19-9 levels decreased from the pretreatment value of 2,007 to 734 U/ml. Therapy with low-frequency US combined with MBs may exhibit an antivasculature effect and may be used as a palliative treatment for patients with unresectable hepatic malignant tumors.