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

Ultrasound-excited temozolomide sonosensitization induces necroptosis in glioblastoma

Temozolomide (TMZ) has been determined to be the chemotherapeutic drug with efficacy for glioblastoma (GBM). Thus, potentiating the therapeutic effect of TMZ can undoubtedly yield twice the result with half the effort. In this study, we found for the first time that TMZ can produce reactive oxygen species (ROS) under the influence of ultrasound (US). This property allows TMZ-US therapy to have better efficacy in the treatment of GBM. Given that the increasing use of US in central nervous system (CNS) diseases and the importance of TMZ for GBM therapy, our results will facilitate the development of TMZ-associated glioblastoma therapies. Moreover, we found that chemotherapeutic drugs might have the ability to generate ROS under the excitation of US. On a larger scale, our findings may be applicable to a wide range of known drugs.

Current status and future perspective of sonodynamic therapy for cancer

There is a tremendous need for prevention and effective treatment of cancer due to the associated morbidity and mortality. In this study, we introduce sonodynamic therapy (SDT), which is expected to be a new cancer treatment modality. SDT is a promising option for minimally invasive treatment of solid tumors and comprises three different components: sonosensitizers, ultrasound, and molecular oxygen. These components are harmless individually, but in combination they generate cytotoxic reactive oxygen species (ROS). We will explore the molecular mechanism by which SDT kills cancer cells, the class of sonosensitizers, drug delivery methods, and in vitro and in vivo studies. At the same time, we will highlight clinical applications for cancer treatment. The progress of SDT research suggests that it has the potential to become an advanced field of cancer treatment in clinical application. In this article, we will focus on the mechanism of action of SDT and its application to cancer treatment, and explain key factors to aid in developing strategies for future SDT development.

Strategy of differentiation therapy: effect of dual-frequency ultrasound on the induction of liver cancer stem-like cells on a HA-based multilayer film system

Cancer stem cells (CSCs) and normal stem cells share the ability to self-renew and drive tumor formation, recurrence, and distant metastasis and are resistant to chemotherapeutic drugs. One potential therapeutic approach for targeting CSCs is to induce CSCs to differentiate into normal cancer cells to eliminate self-renewal and enhance drug sensitivity. We developed a hyaluronic acid (HA)-based multilayer film system for selecting CSC-like hepatocellular carcinoma (HCC) cell colonies. Herein, we assess the differentiation therapy of HCC CSCs using dual-frequency low-intensity ultrasound (LIUS). HA-based multilayer films of poly (allylamine hydrochloride), (PAH/HA)6, were used to isolate CSC colonies. Colony formation, maintenance, and CSC marker expression were identified. The colony-formation rate was investigated, and putative CSC markers for CD44/CD133 expression after 7 days of culture were upregulated on (PAH/HA)6 multilayer films. Dual-frequency LIUS was used to induce CSC colony differentiation, and the phenotype variation, CSC marker expression, gene expression, drug-resistance ability, and invasion ability of CSC colonies with/without LIUS stimulation were compared. The numbers of colonies and CD44/CD133 double-positive cells and the expression levels of stem cell-related genes and proteins associated with stemness all decreased due to differentiation after LIUS exposure. Furthermore, a significant reduction in CSC drug resistance and invasion ability was observed. These results indicate that dual-frequency LIUS induces CSC differentiation and reduces drug resistance and invasion ability. Differentiation of CSCs provides an alternative therapeutic strategy to reverse CSC stemness and force their loss of self-renewal ability. CSC-targeted therapy holds great promise as an effective therapeutic approach for the treatment of human tumors.

Antitumorigenic Effect of Hsp90 Inhibitor SNX-2112 on Tongue Squamous Cell Carcinoma is Enhanced by Low-Intensity Ultrasound

Purpose

The novel Hsp90 inhibitor SNX-2112 showed broad antitumor activity. However, it was still necessary to optimize the therapeutic dosage of SNX-2112 applied on tumors to obtain effective therapy with minimal dose to reduce toxicity. We investigated the role of low-intensity US in promoting antitumorigenic effect of low doses of SNX-2112 on tongue squamous cell carcinoma.

Methods

Cell viability was measured using CCK-8 assay or staining with Calcein AM/PI. Relative cumulative levels of SNX-2112 in cells were detected using high-performance liquid chromatography. The production of ROS was analyzed using fluorescence microscope and flow cytometer. Cellular apoptosis was detected using flow cytometer. The expression levels of proteins of the ERS-associated apoptosis signaling pathway were detected using Western blotting analysis. The efficacy and biosafety of SNX-2112 were also investigated in a mouse xenograft model.

Results

Low-intensity US combined with SNX-2112 exhibited significant antitumor effect, increased the absorption of SNX-2112 by cells even with a low dose, enhanced ROS generation and apoptosis. The combination regimen also inhibited the protein expression of Hsp90 and triggered apoptosis through endoplasmic reticulum stress (ERS) by enhancing PERK, CHOP and Bax protein levels, while downregulating the level of Bcl-2. Additionally, N-acetyl-L-cysteine (NAC), ROS scavenger, was able to reverse these results. Low-intensity US combined with SNX-2112 significantly inhibited tumor growth, prolonged survival of mice, decreased proliferation and promoted apoptosis with no visible damage or abnormalities in major organs in the mouse xenograft model with tongue squamous cell carcinoma.

Conclusion

The antitumor effects of SNX-2112 were enhanced by low-intensity US. The most probable mechanism was that US sonoporation induced more SNX-2112 delivery to the cells and enhanced ROS production, triggering the ERS-associated apoptosis signaling pathway. Therefore, low-intensity US may increase the efficiency of conventional chemotherapy and reduce the dosage of SNX-2112 required and its side effects.

Ultrasound Enhances ZD2767P-Carboxypeptidase G2 against Chemoresistant Ovarian Cancer Cells by Altering the Intracellular Pharmacokinetics of ZD2767D

Prodrug-carboxypeptidase G2 (e.g., ZD2767P+CPG2) can realize a targeted treatment where the specific advantage is a lack of CPG2 analogues in humans, but it is limited by low efficacy. Here ultrasound was employed to enhance ZD2767P+CPG2 (i.e., ZD2767P+CPG2+US) against chemoresistant human ovarian cancer cells. The release dynamics of ZD2767D (activated drug) by CPG2 were investigated. The in vitro efficacy was explored in SKOV3 and SKOV3/DDP (cisplatin-resistant subline) cells; spectrophotometry was established to quantify ZD2767P and ZD2767D, and then intracellular pharmacokinetics were evaluated. The in vivo efficacy was validated in both subcutaneous and orthotopic tumors. With insonation, the ZD2767D concentration was increased during an early period. Insonation synergized ZD2767P+CPG2 to enhance cell death and apoptosis, and efficacies in SKOV3 and SKOV3/DDP cells were similar. Intracellular pharmacokinetics of ZD2767D were nonproportional, and insonation increased the peak level, area under the level vs time curve, and mean residence time. In subcutaneous xenografts, ZD2767P+CPG2 and ZD2767P+CPG2+US resulted in volume-inhibitory rates of 20.4% and 26.5% in SKOV3 tumors and 36.8% and 81.6% in SKOV3/DDP tumors, respectively. In the orthotopic tumor model, the survival time in group ZD2767P+CPG2 or ZD2767P+CPG2+US was prolonged compared with group control, in SKOV3 (33.0 ± 3.5 or 39.2 ± 1.8 vs 25.0 ± 1.6 days, p < 0.0001) and SKOV3/DDP (16.2 ± 4.8 or 22.3 ± 7.3 vs 8.7 ± 3.9 days, p = 0.0015) tumors. These data indicated that ZD2767P+CPG2+US was effective against resistant ovarian cancer cells.

Low‑intensity ultrasound enhances the chemosensitivity of hepatocellular carcinoma cells to cisplatin via altering the miR‑34a/c‑Met axis

Recently, the use of low-intensity ultrasound (LIUS) combined with chemotherapeutic agents is widely used in clinical practice, mainly for the treatment of cancer; however, the mechanisms as to how LIUS enhances the antitumor effects of these agents are not fully understood. The aim of the present study was to explore the synergistic antitumor effects and mechanisms of cisplatin (DDP) combined with LIUS (LIUS-DDP) in hepatocellular carcinoma (HCC). We reported that LIUS effectively enhanced Huh7 and HCCLM3 cell sensitivity to a low concentration of DDP. Reverse transcription-quantitative polymerase chain reaction analysis revealed that LIUS could increase the expression of microRNA-34a (miR-34a) in HCC cells following DDP treatment. In addition, LIUS-DDP significantly increased intracellular reactive oxygen species (ROS) levels in vitro, and the upregulation of miR-34a induced by LIUS-DDP was reversed by the ROS scavenger N-acetylcysteine, suggesting that LIUS upregulates the expression of miR-34a via production of ROS. In addition, knockdown of miR-34a in HCC cells significantly suppressed the synergistic effects of LIUS-DDP treatment. Conversely, overexpression of miR-34a enhanced these synergistic effects. The results of a dual-luciferase assay indicated that c-Met, a well-known oncogene, was a target of miR-34a. We also determined that LIUS-DDP treatment inhibited the expression of c-Met, possibly due to increased ROS production, which upregulated miR-34a expression. Furthermore, overexpression of c-Met reversed the synergistic effects of LIUS-DDP treatment. Our findings suggest that LIUS could enhance the chemosensitivity of HCC cells to DDP by altering the miR-34a/c-Met axis. Therefore, DDP combined with LIUS may be a potential therapeutic application for the clinical treatment of patients with HCC.

Combinations of genotoxic tests for the evaluation of group 1 IARC carcinogens

Many of the known human carcinogens are potent genotoxins that are efficiently detected as carcinogens in human populations but certain types of compounds such as immunosuppressants, sex hormones, etc. act via non-genotoxic mechanism. The absence of genotoxicity and the diversity of modes of action of non-genotoxic carcinogens make predicting their carcinogenic potential extremely challenging. There is evidence that combinations of different short-term tests provide a better and efficient prediction of human genotoxic and non-genotoxic carcinogens. The purpose of this study is to summarize the in vivo and in vitro comet assay (CMT) results of group 1 carcinogens selected from the International Agency for Research on Cancer and to discuss the utility of the comet assay along with other genotoxic assays such as Ames, in vivo micronucleus (MN), and in vivo chromosomal aberration (CA) test. Of the 62 agents for which valid genotoxic data were available, 38 of 61 (62.3%) were Ames test positive, 42 of 60 (70%) were in vivo MN test positive and 36 of 45 (80%) were positive for the in vivo CA test. Higher sensitivity was seen in in vivo CMT (90%) and in vitro CMT (86.9%) assay. Combination of two tests has greater sensitivity than individual tests: in vivo MN + in vivo CA (88.6%); in vivo MN + in vivo CMT (92.5%); and in vivo MN + in vitro CMT (95.6%). Combinations of in vivo or in vitro CMT with other tests provided better sensitivity. In vivo CMT in combination with in vivo CA provided the highest sensitivity (96.7%).

Suppression of human 8-oxoguanine DNA glycosylase (OGG1) augments ultrasound-induced apoptosis in cervical cancer cells

PURPOSE

Human 8-oxoguanine DNA glycosylase (OGG1) is a major base excision repair enzyme, and it was reported to suppress the activation of intrinsic apoptotic signaling pathway in response to oxidative stress. In this study, our aim was to investigate the effects of OGG1 downregulation on ultrasound-induced apoptosis in cervical cancer cells.

METHODS

OGG1 expression was silenced by shRNA in the cervical cancer SW756 and CaSki cells. Cell viability was evaluated by MTT assay after OGG1 knockdown following ultrasound treatment. Ultrasound-induced apoptosis was measured by Annexin V-FITC/propidium iodide. Intracellular reactive oxygen species (ROS) production and Ca(2+) concentration were detected using a fluorescent probe, 2',7'-dichlorofluorescin diacetate (DCFH-DA) and a green fluorescent dye fluo-4AM, respectively. Western blotting was used to analyze the expression of Bcl-2, Bax, cleaved caspase-3, and nuclear factor-κB p65 (NF-κB p65).

RESULTS

The results indicated that OGG1 knockdown did not suppress cell proliferation, but significantly augmented ultrasound-induced inhibitory effects on the cell viability, and increased ultrasound-induced early apoptosis and late apoptosis and necrosis in the SW756 and CaSki cells when exposure to ultrasound (1MHz) at 1.5W/cm(2) for 30 and 60s. OGG1 knockdown significantly increased intracellular ROS production and Ca(2+) concentration after incubation of 6, 24, and 48h post-ultrasound treatment. The downregulation of Bcl-2 protein and the upregulation of Bax, cleaved caspase-3, and NF-κB p65 protein levels were observed in the shRNA-OGG1 cells and mock-shRNA cells, but no significant change of these protein levels was found between of them.

CONCLUSIONS

These results indicate that downregulation of OGG1 expression can augment ultrasound-induced apoptosis in cervical cancer cells, which suggests that OGG1 suppression might provide a new insight for ultrasound-induced therapeutic effects on cervical cancer treatment.

Enhancement of anti-tumor effects of 5-fluorouracil on hepatocellular carcinoma by low-intensity ultrasound

Background

Hepatocellular carcinoma (HCC) accounts for 75 % of liver cancers and is the second most lethal cancer, associated with its multiple etiologies, poor prognosis and resistance to chemotherapy drugs. Chemotherapy treatment on HCC suffers low efficacy of drug uptake and can produce a range of side effects. Here we report an investigation on the effect of a combined treatment on human hepatocellular carcinoma BEL-7402 cells using low-intensity ultrasound (US) and 5-fluorouracil (5-FU).

Methods

The uptake of 5-FU was measured by the high-performance liquid chromatography (HPLC). DNA damage was detected by the comet assay. MTT assay was used to examine cell viability. Intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (Δψm) were respectively detected by the fluorescent probes DCFH-DA or JC-1. Endogenous apoptosis-associated proteins were analyzed by the western blot and immunohistochemistry. Histopathological changes were evaluated by the hematoxylin and eosin (H&E) staining. Cell apoptosis was evaluated by the TUNEL and flow cytometry assays. Cell proliferation was measured using the immunohistochemical staining of PCNA.

Results

Our results showed that low-intensity US (1.1 MHz, 1.0 W/cm², 10 % duty cycle) significantly enhanced the uptake of 5-FU, 5-FU-mediated DNA damage and reactive oxygen species (ROS) generation. The increased ROS production up-regulated the p53 protein level, which led to the up-regulation of Bax and down-regulation of Bcl-2. The enhancement of ROS generation and the activation of the apoptosis-associated proteins further triggered the collapse of mitochondrial membrane potential, released cytochrome c from mitochondria into cytosol and activated the mitochondria-caspase pathway, and cell apoptosis. Such enhanced effects could be partially blocked by the ROS scavenger N-acetylcysteine (NAC). Overall, low-intensity US combined with 5-FU led to an effective inhibition of tumor growth and prolonged overall survival of BEL-7402 HCC-bearing nude mice by more than 15 % compared with 5-FU treatment alone.

Conclusions

Our results showed that low-intensity ultrasound combined with 5-FU produced much enhanced synergistic anti-tumor effects via enhanced ROS production in treating HCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0349-4) contains supplementary material, which is available to authorized users.

Ultrasound-induced new cellular mechanism involved in drug resistance

The acoustic effects in a biological milieu offer several scenarios for the reversal of multidrug resistance. In this study, we have observed higher sensitivity of doxorubicin-resistant uterine sarcoma MES-SA/DX5 cells to ultrasound exposure compared to its parent counterpart MES-SA cells; however, the results showed that the acoustic irradiation was genotoxic and could promote neotic division in exposed cells that was more pronounced in the resistant variant. The neotic progeny, imaged microscopically 24 hr post sonication, could contribute in modulating the final cell survival when an apoptotic dose of doxorubicin was combined with ultrasound applied either simultaneously or sequentially in dual-treatment protocols. Depending on the time and order of application of ultrasound and doxorubicin in combination treatments, there was either desensitization of the parent cells or sensitization of the resistant cells to doxorubicin action.

Synergistic effects of ultrasound-activated microbubbles and doxorubicin on short-term survival of mouse mammary tumor cells

The primary focus of this paper is to quantify the therapeutic synergism when combining ultrasound, ultrasound contrast agents (UCAs) and doxorubicin for breast cancer treatment using an in vitro experimental configuration with mouse mammary tumor (4T1) cells. The 4T1 cells were grown in 96 well plates and allowed to grow to 90% confluency. A 1-MHz focused (f/3) single-element transducer was used to expose the microbubbles (MBs) (Definity) with ultrasound near the surface of the cells. After the ultrasound exposure, different doses of doxorubicin were added and incubated for 24 hours at 37 degrees C, 100% humidity and 5% CO2. The efficacies of the drug only and ultrasound-activated MBs combined with drug therapies to kill cells were then quantified by analyzing the cell viability after 24 hours of treatment using the MTT Cell Proliferation Assay. The combined therapy resulted in 60 +/- 5.9% of cell viability compared to 82 +/- 4.5% when only doxorubicin was used. The cell viability was 72 +/- 5.8% when only ultrasound-activated MBs were used with a similar acoustic pressure condition. No significant increase in cell death was observed for higher concentrations of doxorubicin whereas higher peak negative pressure of the ultrasound wave resulted in increased cell death.

Acquisition of chemoresistance in gliomas is associated with increased mitochondrial coupling and decreased ROS production

Temozolomide (TMZ) is an alkylating agent used for treating gliomas. Chemoresistance is a severe limitation to TMZ therapy; there is a critical need to understand the underlying mechanisms that determine tumor response to TMZ. We recently reported that chemoresistance to TMZ is related to a remodeling of the entire electron transport chain, with significant increases in the activity of complexes II/III and cytochrome c oxidase (CcO). Moreover, pharmacologic and genetic manipulation of CcO reverses chemoresistance. Therefore, to test the hypothesis that TMZ-resistance arises from tighter mitochondrial coupling and decreased production of reactive oxygen species (ROS), we have assessed mitochondrial function in TMZ-sensitive and -resistant glioma cells, and in TMZ-resistant glioblastoma multiform (GBM) xenograft lines (xenolines). Maximum ADP-stimulated (state 3) rates of mitochondrial oxygen consumption were greater in TMZ-resistant cells and xenolines, and basal respiration (state 2), proton leak (state 4), and mitochondrial ROS production were significantly lower in TMZ-resistant cells. Furthermore, TMZ-resistant cells consumed less glucose and produced less lactic acid. Chemoresistant cells were insensitive to the oxidative stress induced by TMZ and hydrogen peroxide challenges, but treatment with the oxidant L-buthionine-S,R-sulfoximine increased TMZ-dependent ROS generation and reversed chemoresistance. Importantly, treatment with the antioxidant N-acetyl-cysteine inhibited TMZ-dependent ROS generation in chemosensitive cells, preventing TMZ toxicity. Finally, we found that mitochondrial DNA-depleted cells (ρ°) were resistant to TMZ and had lower intracellular ROS levels after TMZ exposure compared with parental cells. Repopulation of ρ° cells with mitochondria restored ROS production and sensitivity to TMZ. Taken together, our results indicate that chemoresistance to TMZ is linked to tighter mitochondrial coupling and low ROS production, and suggest a novel mitochondrial ROS-dependent mechanism underlying TMZ-chemoresistance in glioma. Thus, perturbation of mitochondrial functions and changes in redox status might constitute a novel strategy for sensitizing glioma cells to therapeutic approaches.

Investigating the enhancement of cisplatin cytotoxicity on 5637 cells by combination with mogoltacin

Transitional cell carcinomas (TCCs), which account for 90% of bladder cancers, arise from the transitional epithelium of bladder. Cisplatin is a chemotherapeutic drug used to treat bladder cancer, but intrinsic and acquired resistance to cisplatin limit its effectiveness. The aim of this study was to determine the ability of mogoltacin, a sesquiterpene-coumarin from Ferula badrakema, to enhance cytotoxic effects of cisplatin on 5637 cells, using MTT assay, comet method, DAPI staining and efflux assay. In order to analyse mogoltacin combinatorial effects, 5637 cells were cultured in the presence of various combined concentrations of mogoltacin and cisplatin. The results of MTT assay revealed that combination of 1 μg/mL cisplatin+32 μg/mL mogoltacin, increased the cytotoxicity of cisplatin by 45.3%. Investigating the mechanism of this action by comet assay indicated that mogoltacin increases the apoptotic effects of cisplatin on 5637 cells via DNA lesion by 44%. Furthermore, studying nuclear morphological changes revealed that the combination of mogoltacin+cisplatin significantly (P<0.001) increases the number of apoptotic cells. Results of efflux assay indicated that mogoltacin did not have any significant effect on the activity of MDR transporters, therefore, this sesquiterpene-coumarin increases the effects of cisplatin possibly by interacting with other drug transporters.