Low intensity ultrasound-induced apoptosis in human gastric carcinoma cells

Landscape of Cellular Bioeffects Triggered by Ultrasound-Induced Sonoporation

Sonoporation is the process of transient pore formation in the cell membrane triggered by ultrasound (US). Numerous studies have provided us with firm evidence that sonoporation may assist cancer treatment through effective drug and gene delivery. However, there is a massive gap in the body of literature on the issue of understanding the complexity of biophysical and biochemical sonoporation-induced cellular effects. This study provides a detailed explanation of the US-triggered bioeffects, in particular, cell compartments and the internal environment of the cell, as well as the further consequences on cell reproduction and growth. Moreover, a detailed biophysical insight into US-provoked pore formation is presented. This study is expected to review the knowledge of cellular effects initiated by US-induced sonoporation and summarize the attempts at clinical implementation.

Mechanistic Insights and Therapeutic Delivery through Micro/Nanobubble-Assisted Ultrasound

Ultrasound with low frequency (20–100 kHz) assisted drug delivery has been widely investigated as a non-invasive method to enhance the permeability and retention effect of drugs. The functional micro/nanobubble loaded with drugs could provide an unprecedented opportunity for targeted delivery. Then, ultrasound with higher intensity would locally burst bubbles and release agents, thus avoiding side effects associated with systemic administration. Furthermore, ultrasound-mediated destruction of micro/nanobubbles can effectively increase the permeability of vascular membranes and cell membranes, thereby not only increasing the distribution concentration of drugs in the interstitial space of target tissues but also promoting the penetration of drugs through cell membranes into the cytoplasm. These advancements have transformed ultrasound from a purely diagnostic utility into a promising theragnostic tool. In this review, we first discuss the structure and generation of micro/nanobubbles. Second, ultrasound parameters and mechanisms of therapeutic delivery are discussed. Third, potential biomedical applications of micro/nanobubble-assisted ultrasound are summarized. Finally, we discuss the challenges and future directions of ultrasound combined with micro/nanobubbles.

A lesson from earthquake engineering for selectively damaging cancer cell structures

The progressive falling of barriers among disciplines is opening unforeseen scenarios in diagnosis and treatment of cancer diseases. By sharing models and mature knowledge in physics, engineering, computer sciences and molecular biology, synergistic efforts have in fact contributed in the last years to re-think still unsolved problems, shedding light on key roles of mechanobiology in tumors and envisaging new effective strategies for a precise medicine. The use of ultrasounds for altering cancer cells' program is one of the most attracting grounds to be explored in oncophysics, although how to administer mechanical energy to impair selected cell structures and functions simultaneously overcoming the critical trade-off between the impact of the cure and the patient risk still remains an open issue. Within this framework, by starting from the theoretical possibility of selectively attacking malignant cells by exploiting the stiffness discrepancies between tumor and healthy single cells, first proposed by Fraldi et al. (2015), we here investigate the in-frequency response of an overall spherical close-packing of geometrically equal polyhedral cells to gain insights into how mechanical resonance and vibration-induced failure phenomena can be oriented to destroy specific target units when both the cell populations coexist, as it happens for in vivo cases. Inspired by the dynamic action of earthquakes - which fracture only selected elements among adjacent ones in the same structure or damage individual constructions in contiguous buildings - we study the harmonic response of hierarchically architectured cell agglomerates, inhabited by both tumor and healthy cells that interact mutually throughout the extra-cellular matrix and whose cytoskeleton is modeled as a nonlinear soft-tensegrity structure. Numerical Finite Element results show that, at frequencies compatible with low intensity therapeutic ultrasounds, mechanical resonance and possible fatigue cycles of the pre-stressed actin filaments and microtubules can be selectively induced in cancer cells as a function of the global volume fraction of the cell species, paving the way for future engineered treatment protocols.

Exosomes Derived From Low-Intensity Pulsed Ultrasound-Treated Dendritic Cells Suppress Tumor Necrosis Factor-Induced Endothelial Inflammation

OBJECTIVES

Endothelial cell inflammation plays an important role in atherosclerosis. Low-intensity pulsed ultrasonography (LIPUS) exerts an anti-inflammatory function on endothelial cells, whereas the underlying mechanism has not been fully elucidated.

METHODS

Bone marrow dendritic cells (BMDCs) derived from bone barrow cells were treated with LIPUS, and exosomes secreted into the supernatant were purified. The isolated exosomes were incubated with human umbilical vein endothelial cells (HUVECs) to investigate their effect on tumor necrosis factor (TNF)-α-induced endothelial inflammation. Ultrastructure was analyzed by transmission electron microscopy. Messenger RNA levels were determined by quantitative reverse transcription polymerase chain reaction, and protein levels were analyzed by western blot.

RESULTS

The isolated exosomes presented a typical exosomal size of 30 to 100 nm in diameter and expressed exosome positive markers (Alix, CD63, and TSG101) but not the exosome negative marker (Calnexin). Exosomes derived from LIPUS-treated BMDCs were rich in miR-16 and miR-21, which could be engulfed by HUVECs. Pretreatment with exosomes impeded TNFα-induced HUVEC activation and downregulated TNFα-stimulated expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1, thus preventing TNFα-induced activation of the nuclear factor-κB signaling pathway.

CONCLUSION

Exosomes derived from LIPUS-treated BMDC inhibit TNFα-induced endothelial inflammation by inhibiting the nuclear factor-κB signaling pathway.

Nanoparticle-assisted ultrasound: A special focus on sonodynamic therapy against cancer

At present, ultrasound radiation is broadly employed in medicine for both diagnostic and therapeutic purposes at various frequencies and intensities. In this review article, we focus on therapeutically-active nanoparticles (NPs) when stimulated by ultrasound. We first introduce the different ultrasound-based therapies with special attention to the techniques involved in the oncological field, then we summarize the different NPs used, ranging from soft materials, like liposomes or micro/nano-bubbles, to metal and metal oxide NPs. We therefore focus on the sonodynamic therapy and on the possible working mechanisms under debate of NPs-assisted sonodynamic treatments. We support the idea that various, complex and synergistics physical-chemical processes take place during acoustic cavitation and NP activation. Different mechanisms are therefore responsible for the final cancer cell death and strongly depends not only on the type and structure of NPs or nanocarriers, but also on the way they interact with the ultrasonic pressure waves. We conclude with a brief overview of the clinical applications of the various ultrasound therapies and the related use of NPs-assisted ultrasound in clinics, showing that this very innovative and promising approach is however still at its infancy in the clinical cancer treatment.

Low-intensity pulsed ultrasound suppresses proliferation and promotes apoptosis via p38 MAPK signaling in rat visceral preadipocytes

Low-intensity pulsed ultrasound (LIPUS) has been used widely in clinical therapy for bone fracture and soft tissue injury. However, whether LIPUS regulates primary preadipocyte function and adipogenesis remains unknown. In this study, we investigated the potential role of LIPUS in regulating visceral preadipocyte function. Resuspended rat visceral preadipocytes were treated with LIPUS (0.5 MHz, 109.44 mW/cm²) for 1 min and then cultured for an additional 48 hours. Cell proliferation was examined using the CCK-8 assay, and the early apoptosis rate was determined by flow cytometry. In addition, we evaluated the related signaling pathway via examination of proliferating cell nuclear antigen (PCNA), peroxisome proliferator-activated receptor gamma (PPARγ), Bcl2, Bax, cleaved caspase 3 (C-C3), and mitogen-activated protein kinase (MAPK) member protein levels using western blot or quantitative real-time PCR (qRT-PCR). LIPUS inhibited preadipocyte proliferation and induced cell apoptosis. The protein expression of proliferation markers decreased, while expression of the apoptosis-related modulators increased following LIPUS treatment. LIPUS treatment decreased extracellular signal-regulated kinase (ERK) phosphorylation and increased p38 MAPK phosphorylation. Inhibition of p38 MAPK rescued the LIPUS-induced proliferation inhibition and apoptosis induction. Thus, treatment of rat visceral preadipocytes with 0.5 MHz LIPUS suppresses proliferation and promotes apoptosis via activation of p38 MAPK signaling.

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.

Caveolin-1 Mediates Low-Intensity Ultrasound-Induced Apoptosis via Downregulation of Signal Transducer and Activator of Transcription 3 Phosphorylation in Laryngeal Carcinoma Cells

Low-intensity ultrasound therapy has been found to be a potential tool in the management of malignant tumors in recent years. However, the molecular mechanism underlying low-intensity ultrasound-induced apoptosis is still not clear. In this study, we investigated the effects of low-intensity ultrasound-induced apoptosis in HEp-2 cells. We found that low-intensity ultrasound significantly induced apoptosis, and the expression level of caveolin-1 (Cav-1) was dramatically increased after ultrasound treatment of HEp-2 cells. After inhibiting the expression level of Cav-1 using siRNA transfection, we found that the cellular apoptosis induced by low-intensity ultrasound was significantly suppressed. In addition, inhibition of Cav-1 expression promoted phosphorylation of signal transducer and activator of transcription 3 (STAT3), suggesting that the STAT3 signaling pathway was involved in low-intensity ultrasound-induced apoptosis via Cav-1 regulation. Our results indicate that Cav-1/STAT3 signaling pathway may mediate low-intensity ultrasound-induced apoptosis, and this technology could potentially be used clinically for the treatment of cancers.

CO2 bubbling-based 'Nanobomb' System for Targetedly Suppressing Panc-1 Pancreatic Tumor via Low Intensity Ultrasound-activated Inertial Cavitation

Noninvasive and targeted physical treatment is still desirable especially for those cancerous patients. Herein, we develop a new physical treatment protocol by employing CO₂ bubbling-based 'nanobomb' system consisting of low-intensity ultrasound (1.0 W/cm²) and a well-constructed pH/temperature dual-responsive CO₂ release system. Depending on the temperature elevation caused by exogenous low-intensity therapeutic ultrasound irradiation and the low pH caused by the endogenous acidic-environment around/within tumor, dual-responsive CO₂ release system can quickly release CO₂ bubbles, and afterwards, the generated CO₂ bubbles waves will timely explode before dissolution due to triggering by therapeutic ultrasound waves. Related bio-effects (e.g., cavitation, mechanical, shock waves, etc) caused by CO₂ bubbles' explosion effectively induce instant necrosis of panc-1 cells and blood vessel destruction within panc-1 tumor, and consequently inhibit the growth of panc-1 solid tumor, simultaneously minimizing the side effects to normal organs. This new physiotherapy employing CO₂ bubbling-based 'nanobomb' system promises significant potentials in targetedly suppressing tumors, especially for those highly deadly cancers.

Characterization of Dynamic Behaviour of MCF7 and MCF10A Cells in Ultrasonic Field Using Modal and Harmonic Analyses

Treatment options specifically targeting tumour cells are urgently needed in order to reduce the side effects accompanied by chemo- or radiotherapy. Differences in subcellular structure between tumour and normal cells determine their specific elasticity. These structural differences can be utilised by low-frequency ultrasound in order to specifically induce cytotoxicity of tumour cells. For further evaluation, we combined in silico FEM (finite element method) analyses and in vitro assays to bolster the significance of low-frequency ultrasound for tumour treatment. FEM simulations were able to calculate the first resonance frequency of MCF7 breast tumour cells at 21 kHz in contrast to 34 kHz for the MCF10A normal breast cells, which was due to the higher elasticity and larger size of MCF7 cells. For experimental validation of the in silico-determined resonance frequencies, equipment for ultrasonic irradiation with distinct frequencies was constructed. Differences for both cell lines in their response to low-frequent ultrasonic treatment were corroborated in 2D and in 3D cell culture assays. Treatment with ~ 24.5 kHz induced the death of MCF7 cells and MDA-MB-231 metastases cells possessing a similar elasticity; frequencies of > 29 kHz resulted in cytotoxicity of MCF10A. Fractionated treatments by ultrasonic irradiation of suspension myeloid HL60 cells resulted in a significant decrease of viable cells, mostly significant after threefold irradiation in intervals of 3 h. Most importantly in regard to a clinical application, combined ultrasonic treatment and chemotherapy with paclitaxel showed a significantly increased killing of MCF7 cells compared to both monotherapies. In summary, we were able to determine for the first time for different tumour cell lines a specific frequency of low-intensity ultrasound for induction of cell ablation. The cytotoxic effect of ultrasonic irradiation could be increased by either fractionated treatment or in combination with chemotherapy. Thus, our results will open new perspectives in tumour treatment.

Low-intensity ultrasound enhances the anticancer activity of cetuximab in human head and neck cancer cells

The potential clinical use of ultrasound in inducing cell apoptosis and enhancing the effects of anticancer drugs in the treatment of cancers has previously been investigated. In this study, the combined effects of low-intensity ultrasound (LIU) and cetuximab, an anti-epidermal growth factor receptor (EGFR) antibody, on cell killing and induction of apoptosis in HSC-3 and HSC-4 head and neck cancer cells, and its mechanisms were investigated. Experiments were divided into 4 groups: non-treated (CNTRL), cetuximab-treated (CETU), ultrasound-treated (UST) and the combination of cetuximab and US-treated (COMB). Cell viability was assessed by trypan blue staining assay and induction of apoptosis was detected by fluorescein isothiocyanate (FITC)-Annexin V and propidium iodide (PI) staining assay at 24 h after cetuximab and/or US treatment. To elucidate the effect of cetuximab and US on EGFR signaling and apoptosis in head and neck cancer cells after the treatments, the expression of EGFR, phospho-EGFR, and the activation of caspase-3 were evaluated with western blotting. More cell killing features were evident in the COMB group in HSC-3 and HSC-4 cells compared with the other groups. No differences in EGFR expression among the CETU, UST and COMB groups was observed, while the expression of phospho-EGFR in the CETU group was downregulated compared with that in the CNTRL group. Phospho-EGFR expression was much more downregulated in the COMB group compared with that in the other groups. In addition, the activation of caspase-3 in the UST group was upregulated compared with that in the CNTRL group. Caspase-3 activation was much more upregulated in the COMB group than that in the other groups. These data indicated that LIU was able to enhance the anticancer effect of cetuximab in HSC-3 and HSC-4 head and neck cancer cells.

Bioeffects of low-intensity ultrasound in vitro: apoptosis, protein profile alteration, and potential molecular mechanism

OBJECTIVE

The purpose of this study was to evaluate the potential molecular mechanism of low-intensity ultrasound-induced apoptosis by analyzing protein profile alteration in response to ultrasound exposure.

METHODS

Human hepatocarcinoma SMMC-7721 cells were used in this study. Cell viability was measured by a trypan blue dye exclusion test. Morphologic changes were examined by light microscopy. Apoptosis was assessed by phosphatidylserine externalization and DNA fragmentation. The pattern of the mitochondrial membrane potential decrease was determined by flow cytometry. Protein profile alteration was analyzed by comparative proteomics based on 2-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RESULTS

Low-intensity ultrasound (3.0 W/cm(2), 1 minute, cells incubated for 6 hours after ultrasound exposure) induced early apoptosis (mean +/- SD, 26.5% +/- 6.2%) significantly (P < .05) with minimal lysis in human hepatocarcinoma cells in vitro. On a molecular level, several proteins, eg, cellular tumor antigen protein 53, BH3-interacting domain death agonist, apoptosis regulator Bcl-2, and heme oxygenase 1 were identified as responding to ultrasound irradiation, suggesting that mitochondrial dysfunction and oxidative stresses were involved in ultrasound-induced apoptosis. It was also assumed that mitofilin-regulated crista remodeling may be a potential channel of mitochondrial membrane permeabilization pore formation involved in low-intensity ultrasound-induced apoptosis.

CONCLUSIONS

This study suggests that 2 potential molecular signaling pathways are involved in ultrasound-induced apoptosis. It is a first step toward low-intensity ultrasound-induced apoptotic cancer therapy via understanding its relevant molecular signaling and key proteins.

Apoptosis and Microvessel Density in Gastric Cancer: Correlation with Tumor Stage and Prognosis

Gastric cancer remains one of the most common human malignancies with a poor prognosis. Apoptosis is known to be a programmed cell death and its inhibition is involved in the unregulated cellular growth that leads to neoplasms. Microvessel density (MVD) has been investigated as a promoting factor for angiogenesis with conflicting results about its relation to survival. The aim of our study was to search a correlation between these factors and some clinicopathological features and prognosis. Identification of apoptotic cells was performed applying the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling technique and recorded as apoptotic index (A.I.), whereas monoclonal antibodies were used for the study of MVD. A significant correlation was found between low and high A.I. and the subgroup of patients in Stages I and II (P < 0.02); 20 per cent of patients with a low A.I. showed an overall survival longer than 5 years versus 44 per cent of patients with an high A.I. (P = 0.041). High MVD was significantly related to the T stage ( P = 0.036) and to a poorer 5-year overall survival (P < 0.05). Further studies are required to confirm the role of apoptosis and MVD in the development and progression of gastric cancer.

siRNA-mediated gene silencing in the salivary gland using in vivo microbubble-enhanced sonoporation

OBJECTIVES

siRNA-induced gene silencing in the salivary gland using microbubble-enhanced sonoporation was used to develop an in vivo gene knockdown technique.

METHODS

siRNA targeting rat glyceraldehyde-3-phosphate dehydrogenas (GAPDH) was mixed with echo-enhanced microbubbles and reverse-injected into rat parotid glands using transdermal ultrasound. To compare direct and transdermal ultrasound efficiencies, an incision was made on the lateral neck to expose the parotid glands for direct application. The efficiency of gene suppression was determined using quantitative reverse transcription-polymerase chain reaction 24-72 h after siRNA delivery. Cytotoxicity was assessed using histological analysis.

RESULTS

Expression of rat GAPDH in the parotid glands was silenced 48 h after siRNA was delivered by ultrasound (frequency: 1 MHz; intensity: 2 W cm(-2); exposure time: 2 min). High-intensity ultrasound induced tissue damage and apoptotic change. Echo-enhanced microbubbles significantly improved siRNA-induced gene silencing by 10-50%. Compared with transdermal application, direct-exposure ultrasound was only slightly effective, and no significant difference in gene expression was observed.

CONCLUSION

The results indicate that microbubble-enhanced sonoporation can yield in vivo siRNA gene silencing in the rat parotid gland. This technique could be applied to provide gene knockdown organs for functional genomic analyses and to develop siRNA-based gene therapy.

Expression of Livin, Smac/DIABLO and PTEN and their relationships with human gastric adenocarcinoma

AIM: To investigate the regulating role and significance of protein Livin, mitochondrial apoptosis-promoting protein Smac/DIABLO and PTEN in carcinogenesis and progression mechanism.

METHODS: Real-time RT PCR was used to examine the expression of Livin mRNA and Smac/DIABLO mRNA in 75 gastric carcinoma specimens, 20 normal gastric tissues and 20 adjacent tissues. The expression and location of Livin, Smac/DIABLO and PTEN were detected using Western blot combined with immunohistochemistry (SP).

RESULTS: The expression of Livin mRNA was significantly up-regulated in gastric carcinoma specimens (6.374 ± 4.759), however, no expression was found in normal or adjacent tissues. There was a significance in expression between low differentiated carcinoma group and lymph node metastases group (χ² = 9.60, 5.51, P < 0.01 or 0.05). The expression of Livin mRNA had no correlation with tumor size, invasion of nerve or TNM stage. The expression of Smac/DIABLO mRNA was lower in gastric cancer tissues than in normal gastric tissues and adjacent tissues, but there was no significant difference (0.731 ± 0.420 vs 1.104 ± 0.276, 1.061 ± 0.737, all P > 0.05). The expression of Smac/DIABLO mRNA in gastric cancer tissues had no correlation with clinical pathological factors of gastric carcinoma. The expression of Smac/DIABLO held significant difference from intestinal-type gastric carcinoma to diffuse-type gastric carcinoma (χ² = 5.06, P < 0.05). The expression of PTEN was not determined in gastric carcinoma tissues and normal tissues.

CONCLUSION: There is a diversity of expression of Livin, Smac/DIABLO and PTEN in different stages and pathological types of gastric carcinoma. Real-time RT PCR and the expression of Livin and Smac/DIABLO could be beneficial to diagnosis of gastric carcinogenesis, severity of differentiation, and chemotherapy sensitivity.