A review of research into the uses of low level ultrasound in cancer therapy

The use of low power ultrasound in therapeutic medicine is a developing field and this review will concentrate on the applications of this technology in cancer therapy. The effects of low power ultrasound have been evaluated in terms of the biological changes induced in the structure and function of tissue. The main fields of study have been in sonodynamic therapy, improving chemotherapy, gene therapy and apoptosis therapy. The range of ultrasonic power levels that can be effectively employed in therapy appears to be narrow and this may have hindered past research in the applications in cancer treatment.

A microbubble agent improves the therapeutic efficiency of high intensity focused ultrasound: a rabbit kidney study

Eighty kidneys (40 left and 40 right kidneys) of New Zealand rabbits were ablated using high intensity focused ultrasound (HIFU), (14,300 W/cm(2), 1.0 MHz). Kidneys were randomly divided into two groups. HIFU was performed in the manner of linear scan in both groups. Prior to HIFU, normal saline solution and isovolumetric microbubble agent were administrated intravenously in groups I and II, respectively. HIFU was finished in all left kidneys and in 26/40 right ones. The therapeutic efficiency was reflected using necrosis rate (cubic centimeters per second), which was the tissue volume of coagulative necrosis per 1 s HIFU exposure. In both groups, predetermined volumes were damaged without harming overlying tissues. Necrosis rates were increased in group II both in left (0.0089+/-0.0107 vs. 0.0493+/-0.0777, P=0.0323) and in right (0.0039+/-0.0055 vs. 0.0162+/-0.0168, P=0.0248) kidneys. Pathological examinations confirmed that there were no intact tissue focuses within exposed regions in either group. These findings suggested that the microbubble agent improved the therapeutic efficiency of HIFU. Hemorrhage and hyperemia were also detected on the margin of the ablated tissues (both in cortex and medulla) in both groups.

Potentiation of cytotoxicity of adriamycin on human ovarian carcinoma cell line 3AO by low-level ultrasound

The aim of this study was to determine whether the ultrasound, with a dosage that did not lead to acute and delayed inhibition, could potentiate the cytotoxicity of adriamycin to human ovarian carcinoma cell line 3AO in vitro. Drug sensitivity was analyzed by clonogenic assay, cells were treated by adriamycin singly in group ADM (control), adriamycin prior to ultrasound exposure in group ADM + US, and ultrasound irradiation prior to adriamycin administration in group US + ADM. The intracellular drug accumulation in each group was determined by fluorometry. The results were: (1) the values of IC50 were 0.0083, <0.001 and 0.0065 microg/ml in group ADM, ADM + US and US + ADM respectively; the clone surviving rate in group ADM + US and in group US + ADM were decreased (P < 0.001, P < 0.01), compared with control; the surviving rate in group ADM + US was lower than that in group US + ADM (P < 0.01). (2) The intracellular drug accumulations in group ADM + US were promoted (P < 0.01) and not increased significantly in group US + ADM (P > 0.05). These suggested that the low-level ultrasound could enhance the cytotoxicity of adriamycin to human ovarian carcinoma cells and promoted intracellular drug contents played the leading role.

Adverse events of extracorporeal ultrasound-guided high intensity focused ultrasound therapy

BACKGROUND

High-intensity focused ultrasound (HIFU) is considered to be an alternative to surgery. Extracorporeal ultrasound-guided HIFU (USgFU) has been clinically used to treat solid tumors. Preliminary trials in a small sample of a Western population suggested that this modality was safe. Most trials are performed in China thereby providing comprehensive data for understanding the safety profile. The aim of this study was to evaluate adverse events of USgFU therapy.

METHODS AND FINDINGS

Clinical data were searched in 2 Chinese databases. Adverse events of USgFU were summarized and compared with those of magnetic resonance-guided HIFU (MRgFU; for uterine, bone or breast tumor) and transrectal ultrasound-guided HIFU (for prostate cancer or benign prostate hyperplasia). USgFU treatment was performed using 7 types of device. Side effects were evaluated in 13262 cases. There were fewer adverse events in benign lesions than in malignant lesions (11.81% vs. 21.65%, p<0.0001). Rates of adverse events greatly varied between the disease types (0-280%, p<0.0001) and between the applied HIFU devices in both malignant (10.58-44.38%, p<0.0001) and benign lesions (1.67-17.57%, p<0.0001). Chronological analysis did not demonstrate a decrease in the rate of adverse events. Based upon evaluable adverse events, incidences in USgFU were consistent with those in MRgFU or transrectal HIFU. Some side effects frequently occurred following transrectal HIFU were not reported in USgFU. Several events including intrahepatic metastasis, intraoperative high fever, and occlusions of the superior mesenteric artery should be of particular concern because they have not been previously noted. The types of adverse events suggested that they were ultrasonic lesions.

CONCLUSION

The frequency of adverse events depended on the location of the lesion and the type of HIFU device; however, side effects of USgFU were not yet understood. USgFU did not decrease the incidence of adverse events compared with MRgFU.

Hyperecho as the indicator of tissue necrosis during microbubble-assisted high intensity focused ultrasound: sensitivity, specificity and predictive value

The purpose of this study was to determine the sensitivity, specificity and predictive values of hyperecho in grayscale ultrasonic images as the indicator of tissue necrosis in microbubble-assisted high-intensity focused ultrasound (HIFU) exposure in vivo. Livers and kidneys of the rabbit were exposed to HIFU (control group) or microbubble-assisted HIFU (experimental group); a continuous line of ablation, viz. linear scan, was performed to destruct tissues. Tissue responses were evaluated macroscopically and microscopically 24 h after HIFU. The cases of positive (hyperecho occurred and tissue necrotized), false positive (tissue was unaffected although hyperecho appeared), negative (echo was not changed and tissue was intact) and false negative (tissue was destructed despite the lack of hyperecho) were counted, and then the sensitivity, specificity and positive and negative predictive values of hyperecho were calculated. The sensitivity, specificity, positive predictive value and negative predictive value were 49.25% vs. 79.63% (p < 0.001), 45.45% vs. 30.00%, 84.62% vs. 86.00% and 12.82% vs. 21.43% for liver and 76.06% vs. 81.25%, 26.53% vs. 41.67%, 60.00% vs. 82.28% (p = 0.002) and 43.33% vs. 40.00% for kidney, in control and experimental groups, respectively. Rates varied between tissue types in control group. These findings indicated that the use of microbubble during HIFU improved the sensitivity in liver and the positive predictive value in kidney. The specificity and negative predictive value were poor. Hyperecho could only be used as the indicator of tissue necrosis in some tissue types.

Microbubbles assist goat liver ablation by high intensity focused ultrasound

High intensity focused ultrasound (HIFU) has been introduced to treat cancers. However, this therapy is a time-consuming procedure; destructing a deeper volume is also difficult as ultrasonic energy attenuates exponentially with increasing depth in tissues. The aim of the present study was to investigate the effects of introducing microbubbles on liver HIFU ablation. Seventeen goats were divided into groups A (n=8) and B (n=9). The livers in both groups were ablated using HIFU (1.0 MHz, 22,593 W/cm2) performed in the manner of a clinical regime using a clinical device. A microbubble agent was bolus-injected intravenously before HIFU exposure in group B. All animals in group A and seven goats in group B were euthanased to evaluate the ablation efficiency 24 h after HIFU. The necrosis rate (mm3/s), which was the volume of necrosis tissue per second of HIFU exposure, was used to judge the ablation efficiency. Pathological examinations were performed to determine whether there were residual intact tissues within the exposed volume. The other two goats in group B were used to determine the delayed pathological changes 7 days after ultrasonic ablation. The necrosis rate (mm3/s) was increased in group B (14.4647+/-4.1960 versus 33.5302+/-12.4484, P=0.0059). Pathological examinations confirmed that there were no residual unaffected tissue focuses within the exposed volume. Two remarkable changes occurred in the other two goats in group B 7 days after HIFU: there were ghost-cell islands at the periphery of the ablated tissues, and surrounding adjacent tissues outside the reactive zone necrotized. These findings showed that microbubbles could be used to assist liver HIFU ablation.

The use of a micro-bubble agent to enhance rabbit liver destruction using high intensity focused ultrasound

Liver tissues in New Zealand rabbits were ablated using high intensity focused ultrasound (HIFU, 14300 W/cm(2), 1.0 MHz). The animals were intravenously administered 0.2 ml of micro-bubble agent in the experimental (n=20) group and an isovolumetric normal saline solution in the control (n=27) group before HIFU treatment which was performed as a linear scan. In both groups, the preselected tissue volumes were destroyed without harming the overlying tissues. Necrosis rate (NR, cm(3)/s) was used to reflect the ablation efficiency, which was the tissue volume of occurring coagulative necrosis per 1s HIFU exposure. NR was improved in the experimental group (0.0570+/-0.0433 vs 0.0120+/-0.0122, P=0.0002). Pathological studies confirmed that there were no residual intact targets within the exposed volume. These findings suggested that the introduction of the micro-bubble agent enhanced HIFU liver destruction.

Ultrasound: a chemotherapy sensitizer

Chemotherapy plays a very important role in cancer treatment. However, there are still some barriers in the successful use of such therapies, mainly because of the adverse side effects of the anticancer agents and due to the development of chemoresistance. This paper focuses on the use of ultrasound to enhance chemotherapy and to overcome drug resistance. The action of many anticancer agents can be improved with the use of ultrasonic exposure either in vitro or in vivo. Drug resistance can be circumvented using ultrasound alone. Furthermore, the reversal attributable to chemoresistance modifiers, such as verapamil and PSC 833, is augmented by ultrasound. Ultrasound-mediated chemosensitization is usually achieved via increasing intracellular drug accumulation, although other mechanisms are also involved. Ultrasound also can play a role in targeted chemotherapy, releasing anticancer chemicals directly and efficiently into the lesions. However, this promising modality has not been clinically adopted so far and the reasons are discussed.

Anticancer potency of cytotoxic drugs after exposure to high-intensity focused ultrasound in the presence of microbubbles and hematoporphyrin

Chemotherapy is undertaken perioperatively to improve the efficacy of high-intensity focused ultrasound (HIFU) for solid tumors. HIFU at a sufficient intensity for tissue ablation has recently been applied for drug delivery; ultrasonic cavitation plays an important part in HIFU and drug delivery. Hematoporphyrin and microbubbles are adjuncts because they aid cavitation. The effect of HIFU (1.0 MHz; 12,999 W/cm(2) in continuous waves), in the presence of hematoporphyrin and/or microbubbles, on the anticancer potency of 5-fluorouracil, cisplatin, paclitaxel, mitomycin C or adriamycin, was investigated. Insonated adriamycin resulted in a lower death rate of human cancer cells HO-8910 (45.85 ± 2.65% vs 34.84 ± 1.21%, p < 0.05), which was exacerbated when employing hematoporphyrin (34.84 ± 1.21% vs 23.09 ± 7.82%, p < 0.05) or hematoporphyrin combined with microbubbles (34.84 ± 1.21% vs. 8.79 ± 3.69%, p < 0.05); the therapeutic activity was not affected when adding microbubbles alone. High-performance liquid chromatography detected a smaller peak area after subjecting adriamycin to HIFU with the use of hematoporphyrin alone or combined with microbubbles. The other drugs were not affected. Hematoporphyrin, microbubbles and adriamycin increased the throughput of hydroxyl radicals resulting from cavitation as determined by iodine and methylene blue assays. These data suggested that the anticancer activity of a drug may be decreased by HIFU exposure (particularly in the presence of hematoporphyrin and microbubbles). Cavitation produced reactive species that attacked drug molecules, thereby decreasing their antitumor potency; this process was enhanced if the drug itself generated free radicals under insonation.

Circumvention of cisplatin resistance in ovarian cancer by combination of cyclosporin A and low-intensity ultrasound

Cisplatin resistance is a challenge in the treatment of ovarian cancer. The aim of this study was to explore if ultrasound can overcome chemoresistance and enhance chemosensitization due to cyclosporin A. Ultrasound and/or cyclosporin A were employed to overcome cisplatin resistance in human ovarian cancer cell line COC1/DDP. Mechanisms were explored from the perspective of: DNA damage, intracellular platinum level, detoxification, and genes related to drug efflux and DNA repair. In vivo therapeutic efficacy was validated in a short-term model (subrenal cell-clot transplantation) in mice and the survival benefit was investigated in an orthotopic cancer model in mice using HO-8910PM cells. The findings were: (i) ultrasound enhanced the effect of cisplatin leading to a lower cell-survival rate (IC50 decreased from 3.19 to 0.35 μg/ml); (ii) ultrasound enhanced cisplatin via direct (increasing the intercellular level of active platinum) and indirect (decreasing the glutathione level, and expression of LRP and ERCC1 genes) mechanisms that intensified cisplatin-induced DNA damage, thus enhancing cell apoptosis and necrosis; (iii) cisplatin followed by ultrasound led to small tumor sizes in the short-term model without exacerbation of the systemic toxicity, and prolonged the survival times in the orthotopic model; and (iv) ultrasound synergized the sensitization due to cyclosporin A in vitro and in vivo. These data demonstrated that ultrasound combined with cyclosporin A overcame cisplatin resistance in ovarian cancer.

Treatment of transplanted adriamycin-resistant ovarian cancers in mice by combination of adriamycin and ultrasound exposure

Ovarian cancer models were established in cyclophosphamide immunosuppressed mice by subrenal capsular cell fibrin clot transplantation. SKOV3 cancers were treated by adriamycin alone, or adriamycin combined with ultrasound exposure. SKOV3/ADR cancers were treated with adriamycin, as well as verapamil and insonation were administrated alone or concurrently. The results were: (1) Insonation alone could not suppress growth of tumours. (2) In SKOV3 cancers, ultrasound exposure potentiated the efficiency of adriamycin. (3) In SKOV3/ADR cancers, insonation reversed adriamycin resistance, but verapamil was not effective and no synergism existed between it and ultrasound. These findings revealed that ultrasound exposure enhanced the efficiency of adriamycin to both chemosensitive and chemoresistant ovarian cancers in vivo. Mechanisms were discussed.

Microbubbles improve the ablation efficiency of extracorporeal high intensity focused ultrasound against kidney tissues

OBJECTIVE

The necrosis rate is low when ablating kidney tissues with extracorporeal high intensity focused ultrasound (HIFU), and this drawback has been limiting the application of ultrasonic therapy. The aim of the present study was to determine whether microbubbles increased the ablation efficiency in vivo.

METHODS

Goat kidneys were exposed to HIFU (control group) or microbubble-assisted HIFU (experimental group). Microbubbles were intravenously injected before focused ultrasound exposure. The linear scan was employed and tissue ablation was performed in manner of a clinical regime. The necrosis rate was determined 24 h after HIFU. Pathological examinations were performed to confirm tissue necrosis and to determine whether there were unaffected tissues within the exposed volume.

RESULTS

The necrosis rate was increased in experimental group (4.17 +/- 1.33 vs. 9.32 +/- 2.27 mm(3)/s, P = 0.0007). Ablated tissues formed a hemorrhagic volume on gross examinations, and the boundary between treated and untreated areas was sharp. There was no intact tissue within the exposed volume. Hemorrhage frequently occurred in insonated parenchymas. Destructed ghost cells just inside the demarcation were full of vacuoles, when introducing microbubbles. In control group, the volumes of ablated tissues varied drastically between animals despite a same treatment template.

CONCLUSION

Microbubbles increased the ablation efficiency of HIFU against kidney tissues. A preoperative regime might poorly predict the therapeutic outcome.

The effect of free radical scavenger and antioxidant on the increase in intracellular adriamycin accumulation induced by ultrasound

Ultrasound could potentiate cytotoxicity of adriamycin on cancer cell line as a result of increased intracellular accumulation ascribed to cavitation. In order to determine which free radical led to increase of drug content, effects of the free radical scavenger and antioxidant on increased intracellular adriamycin accumulation by ultrasound were investigated. The intracellular drug content of adriamycin was lower in the group where histidine was administrated before ultrasound exposure and in the group where mannitol was added after sonication. Drug accumulation was also decreased in groups in which vitamin C administrated either before or after ultrasonic exposure. These results suggested that hydroxyl radical play the leading role in synergism between ultrasound and adriamycin.

Ultrasound as a cancer chemotherapy sensitizer: the gap between laboratory and bedside

INTRODUCTION

The use of ultrasound to sensitize chemotherapy has been explored, a large amount of encouraging preclinical data has been reported, and an increase in drug influx is considered the main mechanism, leading scientists to believe that ultrasonic chemotherapy will change clinical practice.

AREAS COVERED

Here we first outline the clinical efficacy of ultrasonic chemotherapy using data from controlled trials of high-intensity focused ultrasound (HIFU)-chemotherapy, and then discuss the gap between laboratory and bedside. Data from clinical trials showed that focused ultrasound enhanced anticancer drugs in only 35.0% (7/20) of trials. Preclinical trials indicate that ultrasound augments the action of drugs via multiple pathways. The effect of a transient increase in the intracellular drug level due to ultrasound can be counteracted by certain cellular factors, causing a lack of chemosensitization. The experimental method used can lead to biases in preclinical trials.

EXPERT OPINION

Chemotherapy should not be recommended in HIFU treatments at present. The use of HIFU-chemotherapy in digestive-tract cancers can provide feedback for preclinical and translational researches in ultrasonic chemotherapy. The clinical relevance of preclinical trials should be improved; the drug-ultrasound interactions, sequence effects, predictiveness of in vivo models, and adjuncts of ultrasonic sensitization should be particularly considered.

Reversal of adriamycin resistance in ovarian carcinoma cell line by combination of verapamil and low-level ultrasound

In order to determine whether ultrasound, alone or combined with verapamil, could reverse resistance in adriamycin resistant human ovarian carcinoma cell line SKOV(3)/ADR in vitro, cells were subjected to a variable concentration of adriamycin. Verapamil, ultrasound exposure and both of the two were used concurrently or sequentially. Survival rates were decreased in groups in which acoustic irradiation was exerted, or verapamil pretreated and both of which applied. Intracellular adriamycin levels were high where cytotoxicity was enhanced. These results revealed that ultrasound reverse drug resistance in ovarian carcinoma cells, and synergism also existed between verapamil and acoustic exposure if administrated sequentially. These effects were ascribed to increase of intracellular adriamycin accumulation.

Ultrasound increases DNA damage attributable to cisplatin in cisplatin-resistant human ovarian cancer cells

OBJECTIVE

An increased capacity for DNA repair plays a very important role in cisplatin (DDP) resistance in ovarian cancers. Ultrasound is a potential chemotherapy sensitizer. The aim of this study was to determine whether ultrasound in conjunction with chemotherapy increases DNA damage in chemoresistant human ovarian cancer cells.

METHODS

Ultrasound and/or cyclosporin A were used to overcome chemoresistance in a DDP-resistant human ovarian cancer cell line, COC1/DDP. DNA damage was quantified by comet assay, a form of single-cell gel electrophoresis in which the length of the comet tail reflects the level of DNA damage.

RESULTS

Neither ultrasound nor cyclosporin A alone led to detectable DNA breakage. The use of ultrasound increased DNA breakage due to DDP, while the use of cyclosporin A did not. The addition of ultrasound and cyclosporin A in conjunction with DDP resulted in a 2.55 times increase in the length of comet tail compared with using DDP alone, while their combined use resulted in a 1.73 times increase compared with the combination of just DDP and insonation.

CONCLUSIONS

Insonation increases DNA breakage attributable to DDP in chemoresistant human ovarian cancer cells, and might sensitize cyclosporin A.

Biological effects of ultrasound exposure on adriamycin-resistant and cisplatin-resistant human ovarian carcinoma cell lines in vitro

Human ovarian cancer cell lines, SKOV3 and its adriamycin-resistant substrain SKOV3/ADR and COC1 and its cisplatin-resistant substrain COC1/DDP, were subjected to acoustic exposure. The critical levels (LC), which resulted in no immediate cell killing, were determined in four cell lines, respectively. LC were the same in four cell lines. After being insonated by LC, cell proliferation and clone forming of SKOV3/ADR were suppressed but those of SKOV3 were not affected (1); cell reproduction of COC1 was triggered but that of COC1/DDP was not influenced (2); flow cytometry detected sub-G1 peaks in SKOV3/ADR and COC1/DDP (3). These findings suggested that there were differences in the responses to ultrasound exposure between chemosensitive and chemoresistant human ovarian cancer cells.

The use of models in "target" theory to evaluate the survival curves of human ovarian carcinoma cell line exposure to adriamycin combined with ultrasound

The models of "target" theory in radiation biology were used to evaluate the survival curves of human ovarian carcinoma cell line after exposure to adriamycin combined with ultrasound. 3AO cells were exposed to adriamycin in group ADR, to adriamycin after ultrasound exposure in group US+ADR, and to adriamycin prior to insonation in group ADR+US. The cell survival was determined by a clonogenic assay. The dose-response curves were fitted to two models, (1) single-hit, single-target model, (2) single-hit, multi-target model. The single-hit, multi-target model could fit the survival curve in group ADR, but it could only describe the survivals in groups US+ADR and ADR+US while the concentration of adriamycin was less than 0.05 mug/ml. These suggested that the single-hit, multi-target model could be conditionally used to describe the survival while cells were exposed to the combination of adriamycin and acoustic exposure. The models also were tools to understand the potentiation attributable to insonation.

Mechanisms of reversal of adriamycin resistance in human ovarian carcinoma cell line by ultrasound

The aim of this study was to investigate the reversal of adriamycin resistance in human ovarian cancer cells by ultrasound exposure from perspectives of apoptosis and mdr1 gene. Apoptosis was determined by flow cytometry and mdr1 level by reverse transcription-polymerase chain reaction (RT-PCR). Apoptosis indexes were improved in groups in which ultrasound exposures were applied. RT-PCR did not support that insonation-decreased mdr1 level. These findings suggested that the ultrasound-enhanced therapeutic efficacy was not mediated via modulating gene expression, and ultrasound maybe lowered thresholds for apoptosis and oncosis in chemoresistant ovarian cancer cells.

Ultrastructure alterations in adriamycin-resistant and cisplatin-resistant human ovarian cancer cell lines exposed to nonlethal ultrasound

Human ovarian cancer cell lines, SKOV3 and its adriamycin-resistant substrain SKOV3/ADR and COC1 and its cisplatin-resistant substrain COC1/DDP, were exposed to nonlethal ultrasound. Ultrastructures in sham-insonated and insonated cells were inspected by transmission electron microscopy, and cytochrome C in cytosol was determined by enzyme-linked immunosorbent assay. Ultrasound exposure led to no significant changes in SKOV3/ADR cells, but tumid mitochondria occurred in SKOV3 cells. Mitochondria changes were also detected in some exposed COC1 and COC1/DDP cells. Apoptotic bodies could be detected in either control or insonated COC1/DDP cells. A few exposed COC1/DDP cells became reticular. Cytochrome C in cytosol in exposed SKOV3/ADR cells was increased but that in exposed COC1/DDP cells was decreased. These findings revealed that the bioeffect of ultrasound on chemosensitive cells was not identical to that of chemoresistant ones, and ultrasound was a potential approach for treatment of drug-resistant ovarian cancers.

Ultrasonic therapy for gynecologic tumors

Clinical and potential applications of ultrasonic therapy for gynecologic tumors are overviewed in this minireview. As a noninvasive technique, extracorporeal high-intensity focused ultrasound was clinically used to treat uterine myomas. High-intensity focused ultrasound treats leiomyomas via shrinkage of tumor size, reduction of blood supply, and suppression of cell proliferation, resulting in a relief of symptoms and improvement of quality of life. Preclinical trials have confirmed that ultrasound enhanced a cytotoxic agent against cancers of ovary and cervix; insonation overcomes doxorubicin (adriamycin) and cisplatin resistance in ovarian cancers, suggesting a modality for refractory lesions; ultrasonic hyperthermia induces high temperature increase in deeper cancer tissues thus being a potential modality for treatment of cervical cancers. Transvaginal ultrasonic therapy can be applied for a lesion near the cervix. In summary, ultrasonic therapy is a promising treatment modality for gynecologic tumors, and might change clinical practices.

Extracorporeal ultrasound-guided high intensity focused ultrasound: implications from the present clinical trials

Extracorporeal ultrasound-guided high intensity focused ultrasound (HIFU) has been clinically used for 15 years, and over 36000 cases have been reported. However, there yet lacked a consensus in the clinical values, suggesting the necessity of checking clinical findings. Clinical trials were searched and data reevaluated. HIFU was hardly performed alone; almost all present anticancer means have been applied during an HIFU treatment, and a specific regimen varied between trials; there were heterogeneity and disagreement between trials. The complexity made it difficult to distinguish the effect of HIFU. Based upon evaluable data, the efficacy of HIFU was similar to that of radio frequency, chemoembolization, chemotherapy, radiotherapy, or hormone therapy; a combined therapy did not improve the efficacy. The survival rate of HIFU plus radiotherapy was lower than that of radical surgery in liver cancers. Adverse events had no downtrend in the past years. HIFU was not a standardized procedure where the intensity and insonation mode were modified constantly throughout a treatment, limiting an evaluation from the perspective of ultrasonics. These implied that HIFU should be applied as an alternative at most occasions. The present clinical trials had defects making against the understating of HIFU.

Nanosecond electric pulses deprive zinc ions of carboxypeptidase G2

Nanosecond electric pulses (nsEP, 10kV/cm with a pulse duration of 8, 16 or 24ns) inhibited the activity of carboxypeptidase G2 (CPG2), a zinc-dependent homodimer; the relative activity was <20% when the total exposure time was >120s. No alterations were detected in electrophoresis, chromatography, mass spectroscopy and circular dichroism, thus demonstrating intactness of the apoenzyme. Inductively coupled plasma-mass spectrometry indicated that zinc levels were 3.30μg/mg protein in control CPG2, and decreased to 0.40, 0.12 or 0.38μg/mg protein after 240s of 8-, 16- or 24-ns pulses, respectively. In CPG2 exposed to 240s of 8-, 16- and 24-ns pulses, the reloading of zinc with redialysis recovered the activity to 94.7±3.4%, 84.0±5.2% and 81.7±7.0%, respectively (p=0.0853, 0.0741, 0.0668). These data demonstrated that nsEP inhibited CPG2 via removal of zinc, and that nsEP can be used to modulate CPG2.

Intracellular Pharmacokinetics of Activated Drugs in a Prodrug-Enzyme-Ultrasound System: Evaluations on ZD2767P+CPG2+US

Intracellular pharmacokinetics (PK) of activated drugs is a window to understanding the pharmacodynamics of prodrug-enzyme-ultrasound therapy. Herein PK of ZD2767D (i.e., activated drug) in the ZD2767P+CPG2+US system on A549, A549/DDP, SKOV3, and SKOV3/DDP cells were evaluated (A549/DDP and SKOV3/DDP were cisplatin-resistant sublines). The noncompartment model under extravascular input mode was deemed appropriate for evaluating drug level vs time curves; Cmax, AUClast, MRTlast, Vz, and Cl can reflect the PK feature, but t1/2, AUCinf, and MRTinf were irrational; higher accumulation and slower elimination characterized the PK mechanism of ZD2767P+CPG2+US; enhanced permeability and retention effect can be assessed with Cmax, AUClast, MRTlast, and tlast; ultrasound equivalently modulated Cmax and AUClast in sensitive and resistant cells. The experimental design and dose proportionality were discussed.