Cold Atmospheric Plasma Attenuates Breast Cancer Cell Growth Through Regulation of Cell Microenvironment Effectors

Comprehensive studies on the biological activities of human metastatic (MDA-MB-231) and non-metastatic (MCF-7) breast cancer cell lines, directly or combinedly treated using non-thermal plasma-based approaches

Progressive incidence and a pessimistic survival rate of breast cancer in women worldwide remains one of the most concerning topics. Progressing research indicates a potentially high effectiveness of use cold atmospheric plasma (CAP) systems. The undoubted advantage seems its simplicity in combination with other anti-cancer modalities. Following observed trend of studies, one inventory CAP system was applied to directly treat human breast cancer cell lines and culturing in two different Plasma Activated Media (PAM) for combined utilization. Proposed CAP treatments on MCF-10 A, MCF-7, and MDA-MB-231 cell lines were studied in terms of impact on cell viability by MTT assay. Disturbances in cell motility following direct and combined CAP application were assessed by scratch test. Finally, the induction of apoptosis and necrosis was verified with annexin V and propidium iodide staining. Reactive species generated during CAP treatment were determined based on optical emission spectrometry analysis along with colorimetric methods to qualitatively assess the NO2-, NO3-, H2O2, and total ROS with free radicals concentration. The most effective approach for CAP utilization was combined treatment, leading to significant disruption in cell viability, motility and mostly apoptosis induction in breast cancer cell lines. Determined CAP dose allows for mild outcome, showing insignificant harm for the non-cancerous MCF-10 A cell line, while the highly aggressive MDA-MB-231 cell line shows the highest sensitivity on proposed CAP treatment. Direct CAP treatment seems to drive the cells into the sensitive state in which the effectiveness of PAM is boosted. Observed anti-cancer response of CAP treatment was mostly triggered by RNS (mostly NO2- ions) and ROS along with free radicals (such as H2O2, OH•, O2-•, 1O2, HO2•). The combined application of one CAP source represent a promising alternative in the development of new and effective modalities for breast cancer treatment.

Non-thermal plasma (NTP) treatment of Trigonella foenum-graecum L. seeds stimulates the sprout growth and the production of nutraceutical compounds

The possibility to stimulate the production of some nutraceutical properties of fenugreek (Trigonella foenum-graecum L.) sprouts by non-thermal plasma (NTP) processing of the seeds in different conditions was studied. The non-thermal plasma used in this work was a surface dielectric barrier discharge. Two types of processing were performed: direct NTP treatment and NTP with a cover treatment, to simulate the processing of packaged seeds. For all treatments, the effect of pre-soaking of the seeds was studied as well. The analyses of the seeds after processing indicated an increase of the hydrophilicity of their surface for NTP direct treatment as resulted from the water contact angle measurements, which could be due to the strong etching evidenced by scanning electron microscopy imaging. A significant (p < 0.05) increase of the seedling growth, by up to 50%, was found especially for the pre-soaked seeds. These results were correlated with the increase of chlorophyll pigments concentrations, with higher concentrations in the case of NTP direct treatment than for the NTP with cover treatments. Direct NTP treatment for 30 s of dry seeds led to the highest increase of the flavonoid concentration of about three times compared to that obtained for untreated seeds. For the polyphenols and antioxidant activity, NTP with cover treatments proved to be better, with a significant increase, especially for 90 s treatment of the pre-soaked seeds. All the results indicate the possibility of tuning the nutraceutical properties of fenugreek sprouts by NTP treatment.

Current Status and Future Trends of Cold Atmospheric Plasma as an Oncotherapy

Cold atmospheric plasma (CAP), a redox modulation tool, is capable of inhibiting a wide spectrum of cancers and has thus been proposed as an emerging onco-therapy. However, with incremental successes consecutively reported on the anticancer efficacy of CAP, no consensus has been made on the types of tumours sensitive to CAP due to the different intrinsic characteristics of the cells and the heterogeneous design of CAP devices and their parameter configurations. These factors have substantially hindered the clinical use of CAP as an oncotherapy. It is thus imperative to clarify the tumour types responsive to CAP, the experimental models available for CAP-associated investigations, CAP administration strategies and the mechanisms by which CAP exerts its anticancer effects with the aim of identifying important yet less studied areas to accelerate the process of translating CAP into clinical use and fostering the field of plasma oncology.

The Regulatory Mechanism of Cold Plasma in Relation to Cell Activity and Its Application in Biomedical and Animal Husbandry Practices

As an innovative technology in biological applications, cold plasma is widely used in oral treatment, tissue regeneration, wound healing, and cancer therapy, etc., because of the adjustable composition and temperature which allow the plasma to react with bio-objects safely. Reactive oxygen species (ROS) produced by cold plasma regulate cell activity in an intensity- and time-dependent manner. A low level of ROS produced by cold plasma treatment within the appropriate intensities and times promotes proliferation of skin-related cells and increases angiogenesis, which aid in the acceleration of the wound healing process, while a high level of ROS produced by cold plasma treatment performed at a high intensity or over a long period of time inhibits the proliferation of endothelial cells, keratinocytes, fibroblasts, and cancer cells. Moreover, cold plasma can regulate stem cell proliferation by changing niche interface and producing nitric oxide directly. However, the molecular mechanism of cold plasma regulating cell activity and its potential application in the field of animal husbandry remain unclear in the literature. Therefore, this paper reviews the effects and possible regulatory mechanisms of cold plasma on the activities of endothelial cells, keratinocytes, fibroblasts, stem cells, and cancer cells to provide a theoretical basis for the application of cold plasma to skin-wound healing and cancer therapy. In addition, cold plasma exposure at a high intensity or an extended time shows excellent performances in killing various microorganisms existing in the environment or on the surface of animal food, and preparing inactivated vaccines, while cold plasma treatment within the appropriate conditions improves chicken growth and reproductive capacity. This paper introduces the potential applications of cold plasma treatment in relation to animal-breeding environments, animal health, their growth and reproduction, and animal food processing and preservation, which are all beneficial to the practice of animal husbandry and guarantee good animal food safety results.

Current State of Cold Atmospheric Plasma and Cancer-Immunity Cycle: Therapeutic Relevance and Overcoming Clinical Limitations Using Hydrogels

Cold atmospheric plasma (CAP) is a partially ionized gas that gains attention as a well-tolerated cancer treatment that can enhance anti-tumor immune responses, which are important for durable therapeutic effects. This review offers a comprehensive and critical summary on the current understanding of mechanisms in which CAP can assist anti-tumor immunity: induction of immunogenic cell death, oxidative post-translational modifications of the tumor and its microenvironment, epigenetic regulation of aberrant gene expression, and enhancement of immune cell functions. This should provide a rationale for the effective and meaningful clinical implementation of CAP. As discussed here, despite its potential, CAP faces different clinical limitations associated with the current CAP treatment modalities: direct exposure of cancerous cells to plasma, and indirect treatment through injection of plasma-treated liquids in the tumor. To this end, a novel modality is proposed: plasma-treated hydrogels (PTHs) that can not only help overcome some of the clinical limitations but also offer a convenient platform for combining CAP with existing drugs to improve therapeutic responses and contribute to the clinical translation of CAP. Finally, by integrating expertise in biomaterials and plasma medicine, practical considerations and prospective for the development of PTHs are offered.

Selective Effects of Cold Atmospheric Plasma on Bone Sarcoma Cells and Human Osteoblasts

BACKGROUND

The use of cold atmospheric plasma (CAP) in oncology has been intensively investigated over the past 15 years as it inhibits the growth of many tumor cells. It is known that reactive oxidative species (ROS) produced in CAP are responsible for this effect. However, to translate the use of CAP into medical practice, it is essential to know how CAP treatment affects non-malignant cells. Thus, the current in vitro study deals with the effect of CAP on human bone cancer cells and human osteoblasts. Here, identical CAP treatment regimens were applied to the malignant and non-malignant bone cells and their impact was compared.

METHODS

Two different human bone cancer cell types, U2-OS (osteosarcoma) and A673 (Ewing's sarcoma), and non-malignant primary osteoblasts (HOB) were used. The CAP treatment was performed with the clinically approved kINPen MED. After CAP treatment, growth kinetics and a viability assay were performed. For detecting apoptosis, a caspase-3/7 assay and a TUNEL assay were used. Accumulated ROS was measured in cell culture medium and intracellular. To investigate the influence of CAP on cell motility, a scratch assay was carried out.

RESULTS

The CAP treatment showed strong inhibition of cell growth and viability in bone cancer cells. Apoptotic processes were enhanced in the malignant cells. Osteoblasts showed a higher potential for ROS resistance in comparison to malignant cells. There was no difference in cell motility between benign and malignant cells following CAP treatment.

CONCLUSIONS

Osteoblasts show better tolerance to CAP treatment, indicated by less affected viability compared to CAP-treated bone cancer cells. This points toward the selective effect of CAP on sarcoma cells and represents a further step toward the clinical application of CAP.

Cold atmospheric plasma: Novel opportunities for tumor microenvironment targeting

With mounting preclinical and clinical evidences on the prominent roles of the tumor microenvironment (TME) played during carcinogenesis, the TME has been recognized and used as an important onco-therapeutic target during the past decade. Delineating our current knowledge on TME components and their functionalities can help us recognize novel onco-therapeutic opportunities and establish treatment modalities towards desirable anti-cancer outcome. By identifying and focusing on primary cellular components in the TME, that is, tumor-infiltrating lymphocytes, tumor-associated macrophages, cancer-associated fibroblasts and mesenchymal stem cells, we decomposed their primary functionalities during carcinogenesis, categorized current therapeutic approaches utilizing traits of these components, and forecasted possible benefits that cold atmospheric plasma, a redox modulating tool with selectivity against cancer cells, may convey by targeting the TME. Our insights may open a novel therapeutic avenue for cancer control taking advantages of redox homeostasis and immunostasis.

Modulation of the Tumor-Associated Immuno-Environment by Non-Invasive Physical Plasma

Over the past 15 years, investigating the efficacy of non-invasive physical plasma (NIPP) in cancer treatment as a safe oxidative stress inducer has become an active area of research. So far, most studies focused on the NIPP-induced apoptotic death of tumor cells. However, whether NIPP plays a role in the anti-tumor immune responses need to be deciphered in detail. In this review, we summarized the current knowledge of the potential effects of NIPP on immune cells, tumor-immune interactions, and the immunosuppressive tumor microenvironment. In general, relying on their inherent anti-oxidative defense systems, immune cells show a more resistant character than cancer cells in the NIPP-induced apoptosis, which is an important reason why NIPP is considered promising in cancer management. Moreover, NIPP treatment induces immunogenic cell death of cancer cells, leading to maturation of dendritic cells and activation of cytotoxic CD8⁺ T cells to further eliminate the cancer cells. Some studies also suggest that NIPP treatment may promote anti-tumor immune responses via other mechanisms such as inhibiting tumor angiogenesis and the desmoplasia of tumor stroma. Though more evidence is required, we expect a bright future for applying NIPP in clinical cancer management.

Glutamine Deprivation Synergizes the Anticancer Effects of Cold Atmospheric Plasma on Esophageal Cancer Cells

Esophageal cancer is a highly aggressive malignancy with a low response to standard anti-cancer therapies. There is an unmet need to develop new therapeutic strategies to improve the clinical outcomes of current treatments. Cold atmospheric plasma (CAP) is a promising approach for cancer treatment, and has displayed anticancer efficacy in multiple preclinical models. Recent studies have shown that the efficacy of CAP is positively correlated with intracellular reactive oxygen species (ROS) levels. This suggests that aggressively increasing intracellular ROS levels has the potential to further improve CAP-mediated anticancer efficacy. Glutamine plays an important role in cellular ROS scavenging after being converted to glutathione (GSH, a well-described antioxidant) under physiological conditions, so reducing intracellular glutamine levels seems to be a promising strategy. To test this hypothesis, we treated esophageal cancer cells with CAP while controlling the supply of glutamine. The results showed that glutamine did affect the anticancer effect of CAP, and the combination of CAP stimulation and glutamine deprivation significantly inhibited the proliferation of esophageal cancer cells compared to the control group (p < 0.05). Furthermore, flow cytometric analysis documented a significant increase in more than 10% in apoptosis and necrosis of esophageal cancer cells after this synergistic treatment compared to the control group (p < 0.05). Thus, these results provide the first direct evidence that the biological function of CAP can be modulated by glutamine levels and that combined CAP stimulation and glutamine deprivation represent a promising strategy for the future treatment of esophageal cancer.

Recent advances in cold atmospheric plasma (CAP) for breast cancer therapy

The serious problems of conventional breast cancer therapy strategies such as drug resistance, severe side effects, and lack of selectivity prompted the development of various cold atmospheric plasma (CAP) devices. Due to its advanced technology, CAP can produce a unique environment rich in reactive oxygen and nitrogen species (RONS), photons, charged ions, and an electric field, making it a promising revolutionary platform for cancer therapy. Despite substantial technological successes, CAP-based therapeutic systems are encounter with distinct limitations, including low control of the generated RONS, poor knowledge about its anticancer mechanisms, and challenges concerning designing, manufacturing, clinical translation, and commercialization, which must be resolved. The latest developments in CAP-based therapeutic systems for breast cancer treatment are discussed in this review. More significantly, the integration of CAP-based medicine approaches with other breast cancer therapies, including chemo- and nanotherapy is thoroughly addressed.

Conductive Gas Plasma Treatment Augments Tumor Toxicity of Ringer's Lactate Solutions in a Model of Peritoneal Carcinomatosis

Reactive species generated by medical gas plasma technology can be enriched in liquids for use in oncology targeting disseminated malignancies, such as metastatic colorectal cancer. Notwithstanding, reactive species quantities depend on the treatment mode, and we recently showed gas plasma exposure in conductive modes to be superior for cancer tissue treatment. However, evidence is lacking that such a conductive mode also equips gas plasma-treated liquids to confer augmented intraperitoneal anticancer activity. To this end, employing atmospheric pressure argon plasma jet kINPen-treated Ringer's lactate (oxRilac) in a CT26-model of colorectal peritoneal carcinomatosis, we tested repeated intraabdominal injection of such remotely or conductively oxidized liquid for antitumor control and immunomodulation. Enhanced reactive species formation in conductive mode correlated with reduced tumor burden in vivo, emphasizing the advantage of conduction over the free mode for plasma-conditioned liquids. Interestingly, the infiltration of lymphocytes into the tumors was equally enhanced by both treatments. However, significantly lower levels of interleukin (IL)4 and IL13 and increased levels of IL2 argue for a shift in intratumoral T-helper cell subpopulations correlating with disease control. In conclusion, our data argue for using conductively over remotely prepared plasma-treated liquids for anticancer treatment.

Cold Atmospheric Plasma-Activated Media Improve Paclitaxel Efficacy on Breast Cancer Cells in a Combined Treatment Model

Simple Summary

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer mortality in females, with chemotherapy currently the only adjunctive therapy. However, the disadvantages of chemotherapy are represented by toxicity/side effects, and for many women the benefit is uncertain. Cold atmospheric plasma in in vitro and in vivo experiments proved that it is able to selectively inhibit the growth of cancer cells in various cancer types, with less deleterious side effects. Current guidelines include paclitaxel as a chemotherapy of choice for various types of breast cancers. The aim of the study was to evaluate in vitro, on human breast cancer cell lines, a plasma-activated media as a cytotoxic agent and as an associative agent in a combined treatment for breast cancer with paclitaxel. The collected data indicated that the plasma-activated media amplified the cytotoxic effect of paclitaxel.

Abstract

The use of plasma-activated media (PAM), an alternative to direct delivery of cold atmospheric plasma to cancer cells, has recently gained interest in the plasma medicine field. Paclitaxel (PTX) is used as a chemotherapy of choice for various types of breast cancers, which is the leading cause of mortality in females due to cancer. In this study, we evaluated an alternative way to improve anti-cancerous efficiency of PTX by association with PAM, the ultimate achievement being a better outcome in killing tumoral cells at smaller doses of PTX. MCF-7 and MDA-MB-231 cell lines were used, and the outcome was measured by cell viability (MTT assay), the survival rate (clonogenic assay), apoptosis occurrence, and genotoxicity (COMET assay). Treatment consisted of the use of PAM in combination with under IC50 doses of PTX in short- and long-term models. The experimental data showed that PAM had the capacity to improve PTX’s cytotoxicity, as viability of the breast cancer cells dropped, an effect maintained in long-term experiments. A higher frequency of apoptotic, dead cells, and DNA fragmentation was registered in cells treated with the combined treatment as compared with those treated only with PT. Overall, PAM had the capacity to amplify the anti-cancerous effect of PTX.