Hypercalcemia in Cancer: Causes, Effects, and Treatment Strategies.

Calcium plays central roles in numerous biological processes, thereby, its levels in the blood are under strict control to maintain homeostatic balance and enable the proper functioning of living organisms. The regulatory mechanisms ensuring this balance can be affected by pathologies such as cancer, and as a result, hyper- or hypocalcemia can occur. These states, characterized by elevated or decreased calcium blood levels, respectively, have a significant effect on general homeostasis. This article focuses on a particular form of calcium metabolism disorder, which is hypercalcemia in neoplasms. It also constitutes a summary of the current knowledge regarding the diagnosis of hypercalcemia and its management. Hypercalcemia of malignancy is estimated to affect over 40% of cancer patients and can be associated with both solid and blood cancers. Elevated calcium levels can be an indicator of developing cancer. The main mechanism of hypercalcemia development in tumors appears to be excessive production of parathyroid hormone-related peptides. Among the known treatment methods, bisphosphonates, calcitonin, steroids, and denosumab should be mentioned, but ongoing research promotes progress in pharmacotherapy. Given the rising global cancer prevalence, the problem of hypercalcemia is of high importance and requires attention.

The Antagonistic and Synergistic Role of Fe3+ Compounds in Chemo- and Electrochemotherapy in Human Colon Cancer In Vitro.

Colon cancer (CC) management includes surgery, radio- and chemotherapy based on treatment with 5-fluorouracil (5-FU) or its derivatives. However, its application is limited to low-grade carcinomas. Thus, much research has been conducted to introduce new techniques and drugs to the therapy. CC mostly affects older people suffering from cardiac diseases, where iron compounds are commonly used. Ferric citrate and iron (III)-EDTA complexes have proven to be effective in colon cancer in vitro. This study aimed to determine the potency and action of iron-containing compounds in colon cancer treatment by chemo- and electrochemotherapy in both nano- and microsecond protocols. The viability of the cells was assessed after standalone iron (III) citrate and iron (III)-EDTA incubation. Both compounds were also assessed with 5-FU to determine the combination index. Additionally, frataxin expression was taken as the quantitative response to the exposition of iron compounds. Each of the substances exhibited a cytotoxic effect on the LoVo cell line. Electroporation with standalone drugs revealed the potency of 5-FU and iron(III)-EDTA in CC treatment. The combination of 5-FU with iron(III)-EDTA acted synergistically, increasing the viability of the cells in the nanosecond electrochemotherapy protocol. Iron(III)-EDTA decreased the frataxin expression, thus inducing ferroptosis. Iron(III) citrate induced the progression of cancer; therefore, it should not be considered as a potential therapeutic option. The relatively low stability of iron(III) citrate leads to the delivery of citrate anions to cancer cells, which could increase the Krebs cycle rate and promote progression.

Negative effects of cancellation during nanosecond range High-Frequency calcium based electrochemotherapy in vitro.

Drug delivery using nanosecond pulsed electric fields is a new branch of electroporation-based treatments, which potentially can substitute European standard operating procedures for electrochemotherapy. In this work, for the first time, we characterize the effects of ultra-fast repetition frequency (1-2.5 MHz) nanosecond pulses (5-9 kV/cm, 200 and 400 ns) in the context of nano-electrochemotherapy with calcium. Additionally, we investigate the feasibility of bipolar symmetric (↑200 ns + ↓200 ns) and asymmetric (↑200 ns + ↓400 ns) nanosecond protocols for calcium delivery. The effects of bipolar cancellation and the influence of interphase delay (200 ns) are overviewed. Human lung cancer cell lines A549 and H69AR were used as a model. It was shown that unipolar pulses delivered at high frequency are effective for electrochemotherapy with a significant improvement in efficiency when the delay between separate pulses is reduced. Bipolar symmetric pulses trigger the cancellation phenomenon limiting applications for drug delivery and can be compensated by the asymmetry of the pulse (↑200 ns + ↓400 ns or ↑400 ns + ↓200 ns). The results of this study can be successfully used to derive a new generation of nsPEF protocols for successful electrochemotherapy treatments.

Susceptibility of various human cancer cell lines to nanosecond and microsecond range electrochemotherapy: Feasibility of multi-drug cocktails.

Electrochemotherapy (ECT) involves combining anticancer drugs with electroporation, which is induced by pulsed electric fields (PEFs), while the effects vary in effectiveness based on the specific parameters of the electrical pulses and susceptibility of the cells to a specific drug. In this work, we utilized conventional microsecond electroporation protocols (0.8 - 1.5 kV/cm × 100 µs × 8, 1 Hz) and the new modality of nanosecond pulses (4 and 8 kV/cm × 500 ns × 100, 1 kHz and 1 MHz), which are compressed into a high frequency burst. Sensitive and resistant lung, breast and ovarian human cancer cell lines were used in the study. In order to overcome drug-resistance, we have investigated the feasibility to use anticancer drug cocktails i.e., bleomycin and cisplatin combinations with metformin, vinorelbine and Dp44mT. The different susceptibility of various human cancer cells lines to electric pulses was determined, the efficacy of ECT was characterized and the type of cell death depending on the combinations of drugs was investigated. The results indicate that synergistic effects of PEFs with drug cocktails may be used to overcome drug-resistance in cancer, while the application of nsPEF provides more flexibility in parametric protocols and modulation of cancer cell death.

The influence of asymmetrical bipolar pulses and interphase intervals on the bipolar cancellation phenomenon in the ovarian cancer cell line.

The application of negative polarity electrical pulse (↓) following positive polarity pulses (↑) may induce bipolar cancellation (BPC), a unique physiological response believed to be specific to nanosecond electroporation (nsEP). The literature lacks analysis of bipolar electroporation (BP EP) involving asymmetrical sequences composed of nanosecond and microsecond pulses. Moreover, the impact of interphase interval on BPC caused by such asymmetrical pulse needs consideration. In this study, the authors utilized the ovarian clear carcinoma cell line (OvBH-1) model to investigate the BPC with asymmetrical sequences. Cells were exposed to pulses delivered in 10-pulse bursts but as uni- or bipolar, symmetrical, or asymmetrical sequences with a duration of 600 ns or 10 µs and electric field strength equal to 7.0 or 1.8 kV/cm, respectively. It was shown that the asymmetry of pulses influences BPC. The obtained results have also been investigated in the context of calcium electrochemotherapy. The reduction of cell membrane poration, and cell survival have been observed following Ca2+ electrochemotherapy. The effects of interphase delays (1 and 10 µs) on the BPC phenomenon were reported. Our findings show that the BPC phenomenon can be controlled using pulse asymmetry or delay between the positive and negative polarity of the pulse.

Evaluation of the Anticancer Activity of Calcium Ions Introduced into Human Breast Adenocarcinoma Cells MCF-7/WT and MCF-7/DOX by Electroporation.

Breast cancer ranks among the top three most common malignant neoplasms in Poland. The use of calcium ion-assisted electroporation is an alternative approach to the classic treatment of this disease. The studies conducted in recent years confirm the effectiveness of electroporation with calcium ions. Electroporation is a method that uses short electrical pulses to create transitional pores in the cell membrane to allow the penetration of certain drugs. The aim of this study was to investigate the antitumor effects of electroporation alone and calcium ion-assisted electroporation on human mammary adenocarcinoma cells that are sensitive (MCF-7/WT) and resistant to doxorubicin (MCF-7/DOX). The cell viability was assessed using independent tests: MTT and SRB. The type of cell death after the applied therapy was determined by TUNEL and flow cytometry (FACS) methods. The expression of Cav3.1 and Cav3.2 proteins of T-type voltage-gated calcium channels was assessed by immunocytochemistry, and changes in the morphology of CaEP-treated cells were visualized using a holotomographic microscope. The obtained results confirmed the effectiveness of the investigated therapeutic method. The results of the work constitute a good basis for planning research at the in vivo level and in the future to develop a more effective and safer method of breast cancer treatment for patients.

Nanoelectropulse delivery for cell membrane perturbation and oxidation in human colon adenocarcinoma cells with drug resistance.

Ultrashort electric pulses in the nanosecond range (nsPEF) can affect extra- and intracellular lipid structures and can also alternate cell functioning reversibly and irreversibly. Several of the nsPEF effects are due to the abrupt rise in intracellular free calcium levels and calcium ions influx from the outside. Calcium is one of the most important factors in cell proliferation, differentiation, and cell death (apoptosis or necrosis). Manipulating calcium levels using electroporation can have different effects on normal and malignant cells. This study aimed to examine the impact of nsPEFs, combined with 1 mM Ca2+ in human colon adenocarcinoma cell lines: sensitive- LoVo and drug resistant-LoVoDX. In this study 200 pulses of 10 ns and high voltage (12.5-50 kVcm-1) were used. Cell viability was determined by MTT and clonogenic assay. Proteasomal activity, GSH/GSSG assay, ROS production, and PALS-1 protein were evaluated as oxidative stress markers and protein damage. Cell morphology was visualized by AFM, SEM, and confocal microscopy imaging. The results revealed that nsPEF with 1 mM Ca2+ is cytotoxic, particularly for LoVoDX cells, and safe for normal cells. NsPEF provoked ROS release, altered cell polarity, and destabilized cell morphology. These results can be important for future protocols for colon adenocarcinoma using calcium nsPEF.

Nanosecond PEF Induces Oxidative Stress and Apoptosis via Proteasomal Activity Inhibition in Gastric Adenocarcinoma Cells with Drug Resistance.

Nanosecond (ns) pulsed electric field (PEF) is a technology in which the application of ultra-short electrical pulses can be used to disrupt the barrier function of cell plasma and internal membranes. Disruptions of the membrane integrity cause a substantial imbalance in cell homeostasis in which oxidative stress is a principal component. In the present study, nsPEF-induced oxidative stress was investigated in two gastric adenocarcinoma cell lines (EPG85-257P and EPG85-257RDB) which differ by their sensitivity to daunorubicin. Cells were exposed to 200 pulses of 10 ns duration, with the amplitude and pulse repetition frequency at 1 kHz, with electric field intensity varying from 12.5 to 50 kV/cm. The electroporation buffer contained either 1 mM or 2 mM calcium chloride. CellMask DeepRed visualized cell plasma permeabilization, Fluo-4 was used to visualize internal calcium ions content, and F-actin was labeled with AlexaFluor®488 for the cytoskeleton. The cellular viability was determined by MTT assay. An alkaline and neutral comet assay was employed to detect apoptotic and necrotic cell death. The luminescent method estimated the modifications in GSSG/GSH redox potential and the imbalance of proteasomal activity (chymotrypsin-, trypsin- and caspase-like). The reactive oxygen species (ROS) level was measured by flow cytometry using dihydroethidium (DHE) dye. Morphological visualization indicated cell shrinkage, affected cell membranes (characteristic bubbles and changed cell shape), and the reorganization of actin fibers with sites of its dense concentration; the effect was more intense with the increasing electric field strength. The most significant decrease in cell viability and GSSG/GSH redox potential was noted at the highest amplitude of 50 kV/cm, and calcium ions amplified this effect. nsPEF, particularly with calcium ions, inhibited proteasomal activities, resulting in increased protein degradation. nsPEF increased the percentage of apoptotic cells and ROS levels. The EPG85-257 RDB cell line, which is resistant to standard chemotherapy, was more sensitive to applied nsPEF protocols. The applied nsPEF method disrupted the metabolism of cancer cells and induced apoptotic cell death. The nsPEF ability to cause apoptosis, oxidative stress, and protein degradation make the nsPEF methodology a suitable alternative to current anticancer pharmacological methods.

Synthesis, Anticancer Activity and Molecular Docking Studies of Novel N-Mannich Bases of 1,3,4-Oxadiazole Based on 4,6-Dimethylpyridine Scaffold.

Cancer is one of the greatest challenges in modern medicine today. Difficult and long-term treatment, the many side effects of the drugs used and the growing resistance to treatment of neoplastic cells necessitate new approaches to therapy. A very promising targeted therapy is based on direct impact only on cancer cells. As a continuation of our research on new biologically active molecules, we report herein the design, synthesis and anticancer evaluation of a new series of N-Mannich-base-type hybrid compounds containing morfoline or different substituted piperazines moieties, a 1,3,4-oxadiazole ring and a 4,6-dimethylpyridine core. All compounds were tested for their potential cytotoxicity against five human cancer cell lines, A375, C32, SNB-19, MCF-7/WT and MCF-7/DX. Two of the active N-Mannich bases (compounds 5 and 6) were further evaluated for growth inhibition effects in melanoma (A375 and C32), and normal (HaCaT) cell lines using clonogenic assay and a population doubling time test. The apoptosis was determined with the neutral version of comet assay. The confocal microscopy method enabled the visualization of F-actin reorganization. The obtained results demonstrated that compounds 5 and 6 have cytotoxic and proapoptotic effects on melanoma cells and are capable of inducing F-actin depolarization in a dose-dependent manner. Moreover, computational chemistry approaches, molecular docking and electrostatic potential were employed to study non-covalent interactions of the investigated compounds with four receptors. It was found that all the examined molecules exhibit a similar binding affinity with respect to the chosen reference drugs.

Structure and cytotoxic properties of 1-hydroxy-5-methyl-7-phenylpyrido[3,4-d]pyridazin-4(3H)-one and its mono- and disubstituted ethyl acetates.

Derivatives of pyrido[3,4-d]pyridazine, namely, 1-hydroxy-5-methyl-7-phenylpyrido[3,4-d]pyridazin-4(3H)-one dimethylformamide monosolvate, C14H11N3O2·C3H7NO (2), ethyl [1-(2-ethoxy-2-oxoethoxy)-5-methyl-4-oxo-7-phenyl-3,4-dihydropyrido[3,4-d]pyridazin-3-yl]acetate, C18H17N3O4 (3), and ethyl [(5-methyl-4-oxo-7-phenyl-3,4-dihydropyrido[3,4-d]pyridazin-1-yl)oxy]acetate, C22H23N3O6 (4), were synthesized with the aim of discovering new potential biologically active agents. The properties of all three derivatives were characterized by 1H NMR, 13C NMR and FT-IR spectroscopic analysis. All the crystals were obtained by a solvent diffusion method from dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) and characterized by single-crystal X-ray diffraction. The collected X-ray data revealed that the crystals of 2 and 4 belong to the triclinic space group P-1, whereas the crystal of 3 belongs to the monoclinic space group P21/c. The presented derivatives crystallized with one molecule in the asymmetric unit, but only compound 2 crystallized as a solvate with DMF. Structure analysis showed that the molecule of 2 exists as its amide-imidic acid tautomer and that O-alkylation occurred before N-alkylation during the synthesis of the mono- and disubstituted derivatives, i.e. 3 and 4, respectively. The molecular geometries of the 5-methyl-7-phenylpyrido[3,4-d]pyridazine core within the studied derivatives differ in the mutual orientation of the rings. The interplanar angles between the heterocyclic ring and the bound aromatic ring are 1.71 (7), 18.16 (3) and 3.1 (1)° for 2, 3 and 4, respectively. The potential cytotoxicity of these compounds was evaluated against one normal (HaCat) and four human cancer cell lines (A549, DU145, MDA-MB-231 and SKOV-3).

Does the shape of the electric pulse matter in electroporation?

Electric pulses are widely used in biology, medicine, industry, and food processing. Numerous studies indicate that electroporation (EP) is a pulse-dependent process, and the electric pulse shape and duration strongly determine permeabilization efficacy. EP protocols are precisely planned in terms of the size and charge of the molecules, which will be delivered to the cell. In reversible and irreversible EP applications, rectangular or sine, polar or bipolar pulses are commonly used. The usage of pulses of the asymmetric shape is still limited to high voltage and low voltage (HV/LV) sequences in the context of gene delivery, while EP-based applications of ultra-short asymmetric pulses are just starting to emerge. This review emphasizes the importance and role of the pulse shape for membrane permeabilization by EP.

Pulsed electric fields with calcium ions stimulate oxidative alternations and lipid peroxidation in human non-small cell lung cancer.

Pulsed electric fields (PEFs) are commonly used to facilitate the delivery of various molecules, including pharmaceuticals, into living cells. However, the applied protocols still require optimization regarding the conditions of the permeabilization process, i.e., pulse waveform, voltage, duration, and the number of pulses in a burst. This study highlights the importance of electrochemical processes involved in the electropermeabilization process, known as electroporation. This research investigated the effects of electroporation on human non-small cell lung cancer cells (A549) in potassium (SKM) and HEPES-based buffers (SHM) using sub-microsecond and microsecond range pulses. The experiments were performed using 100 ns - 100 µs (0.6-15 kV/cm) bursts with 8 pulses in a sequence. It was shown that depending on the buffer composition, the susceptibility of cells to PEF varies, while calcium enhances the cytotoxic effects of PEF, if high cell membrane permeabilization is triggered. It was also determined that electroporation with calcium ions induces oxidative stress in cells, including lipid peroxidation (LPO), generation of reactive oxygen species (ROS), and neutral lipid droplets. Here, we demonstrated that calcium ions and optimized pulse parameters could potentiate PEF efficacy and oxidative alternations in lung cancer cells. Thus, the anticancer efficacy of PEF in lung cancers in combination with standard cytostatic drugs or calcium ions should be considered, but this issue still requires in-depth detailed studies with in vivo models.

Nanosecond electrochemotherapy using bleomycin or doxorubicin: Influence of pulse amplitude, duration and burst frequency.

Electroporation is a pulsed electric field (PEF) induced phenomenon, which effectiveness varies dependent on pulse parameters. This work focuses on nano-electrochemotherapy with bleomycin and doxorubicin to derive protocols as effective as European Standard Operating Procedures on Electrochemotherapy (ESOPE), which employ conventional microsecond range pulses. As a model, murine Lewis lung carcinoma (LLC1) cell line was used. The effects of pulse duration (100-500 ns), PEF amplitude (6-10 kV/cm) and pulse repetition frequency (10 kHz, 100 kHz, 1 MHz) were studied. A total of 75 ns protocol variations have been used. For detection of cell permeabilization, Yo-Pro-1 and flow cytometry were employed. Cell viability was evaluated 24-, 48-, or 72-hours post-electroporation. Nanosecond parametric protocols resulting in comparable treatment efficiency as ESOPE (1.3 kV/cm × 100 µs × 8) have been proposed. It was shown that high-frequency nanosecond electrochemotherapy with bleomycin or doxorubicin could be an alternative for established ESOPE protocols.

RCCS Bioreactor-Based Modeled Microgravity Affects Gastric Cancer Cells and Improves the Chemotherapeutic Effect.

(1) Background: The main purpose of the study was to determine whether altered gravity might alter cell viability, improve drug delivery and modulate the expression of drug resistance-related genes. (2) Methods: This study investigated the intracellular mechanisms activated by microgravity in human resistant and sensitive gastric cancer cells (EPG85-257 RDB) and (EPG85-257 P). We used a rotary cell culture system (RCCS) developed by NASA to expose cells to altered gravity. The antitumor potential of microgravity was simulated by the RCCS bioreactor, and its effectiveness was evaluated in sensitive cell lines compared to chemotherapy-resistant cells concerning drug-sensitive cancer cells. Microgravity with chemotherapy was estimated by the viability assay, cytoskeleton imaging, MDR (multidrug resistance) gene expression analysis, MTCO-1 (mitochondrially encoded cytochrome C oxidase I), and 8-OHdG immunocytochemical analysis. (3) Results: We found that altered gravity combined with doxorubicin was cytotoxic to cancer cells. Cells following simulated microgravity revealed decreased expression of genes related to drug resistance and increased DNA/RNA damage marker expression. Cytoskeleton evaluation demonstrated significant reorganization of F-actin fibers after exposure to changed gravity conditions. (4) Conclusions: Intracellular alterations caused by simulated microgravity can increase gastric cancer cells' sensitivity to chemotherapy. We have obtained satisfactory results showing the correlation between altered gravity and MDR phenomena which seems promising in future therapeutic applications.

Anticancer Efficacy of 6-Gingerol with Paclitaxel against Wild Type of Human Breast Adenocarcinoma.

Breast cancer is one of the most common malignant neoplasms, and despite the dynamic development of anticancer therapies, 5-year survival in the metastatic stage is still less than 30%. 6-Gingerol (1-[4'-hydroxy-3'-methoxyphenyl]-5-hydroxy-3-decanone) is a substance contained in ginger, which exhibits anti-cancer properties. Paclitaxel is a cytostatic substance used to treat breast cancer, but its therapeutically effective dose has many adverse effects. The aim of the presented study was to assess the anticancer effect of 6-gingerol and the possibility of increasing the effectiveness of Paclitaxel in the death induction of wild type human breast cancer cells. MCF-7/WT cells were treated with drugs-6-gingerol and paclitaxel at selected concentrations. The mitochondrial activity assay, caspase 7 activity assay, ATP assay, microscopy studies, and RT-PCR assays were performed to evaluate the antitumor activity and mechanism of action of both compounds, alone and in combination. After 72 h of incubation, the mitochondrial activity showed that the combination of 5 nM Paclitaxel with 10 µM 6-Gingerol led to the same decrease in viability as the use of 20 nM Paclitaxel alone; 10 µM 6-Gingerol led to an enhancement of caspase 7 activity, with the highest activity observed after 24 h of incubation. A real-time PCR study showed that 6-Gingerol induces the simultaneous transcription of Bax with TP53 genes in large excess to BCL-2. In contrast, 5 nM Paclitaxel induces TP53 transcription in excess of BCL-2 and Bax. Our results suggest that 6-Gingerol may act as a cell death-inducing agent in cancer cells and, in combination with paclitaxel, and increase the effectiveness of conventional chemotherapy.

Micro- and Nanosecond Pulses Used in Doxorubicin Electrochemotherapy in Human Breast and Colon Cancer Cells with Drug Resistance.

(1) Background: Pulsed electric field (PEF) techniques are commonly used to support the delivery of various molecules. A PEF seems a promising method for low permeability drugs or when cells demonstrate therapy resistance and the cell membrane becomes an impermeable barrier. (2) Methods: In this study, we have used doxorubicin-resistant and sensitive models of human breast cancer (MCF-7/DX, MCF-7/WT) and colon cancer cells (LoVo, LoVoDX). The study aimed to investigate the susceptibility of the cells to doxorubicin (DOX) and electric fields in the 20-900 ns pulse duration range. The viability assay was utilized to evaluate the PEF protocols' efficacy. Cell confluency and reduced glutathione were measured after PEF protocols. (3) Results: The obtained results showed that PEFs significantly supported doxorubicin delivery and cytotoxicity after 48 and 72 h. The 60 kV/cm ultrashort pulses × 20 ns × 400 had the most significant cytotoxic anticancer effect. The increase in DOX concentration provokes a decrease in cell viability, affected cell confluency, and reduced GSSH when combined with the ESOPE (European Standard Operating Procedures of Electrochemotherapy) protocol. Additionally, reactive oxygen species after PEF and PEF-DOX were detected. (4) Conclusions: Ultrashort electric pulses with low DOX content or ESOPE with higher DOX content seem the most promising in colon and breast cancer treatment.

Synthesis, Structural Characterization and Anticancer Activity of New 5-Trifluoromethyl-2-thioxo-thiazolo[4,5-d]pyrimidine Derivatives.

Thiazolo[4,5-d]pyrimidine derivatives are considered potential therapeutic agents, particularly in the development of anticancer drugs. In this study, new 7-oxo-(2a-e), 7-chloro-(3a-e) and also three 7-amino-(4a-c) 5-trifluoromethyl-2-thioxo-thiazolo[4,5-d]pyrimidine derivatives have been synthesized and evaluated for their potential anticancer activity. These derivatives were characterized by spectroscopic methods and elemental analysis, and the single-crystal X-ray diffraction was further performed to confirm a 3D structure for compounds 2e and 4b. The antiproliferative activity evaluation of twelve new compounds was carried out on a variety of cell lines including four human cancer (A375, C32, DU145, MCF-7/WT) and two normal cell lines (CHO-K1 and HaCaT). Four of them (2b, 3b, 4b and 4c) were selected by the National Cancer Institute and evaluated for their in vitro anticancer activity using the NCI-60 screening program. 7-Chloro-3-phenyl-5-(trifluoromethyl)[1,3]thiazolo[4,5-d]pyrimidine-2(3H)-thione (3b) proved to be the most active among the newly synthesized compounds.

Atorvastatin Modulates the Efficacy of Electroporation and Calcium Electrochemotherapy.

Electroporation is influenced by the features of the targeted cell membranes, e.g., the cholesterol content and the surface tension of the membrane. The latter is eventually affected by the organization of actin fibers. Atorvastatin is a statin known to influence both the cholesterol content and the organization of actin. This work analyzes the effects of the latter on the efficacy of electroporation of cancer cells. In addition, herein, electroporation was combined with calcium chloride (CaEP) to assess as well the effects of the statin on the efficacy of electrochemotherapy. Cholesterol-rich cell lines MDA-MB231, DU 145, and A375 underwent (1) 48 h preincubation or (2) direct treatment with 50 nM atorvastatin. We studied the impact of the statin on cholesterol and actin fiber organization and analyzed the cells' membrane permeability. The viability of cells subjected to PEF (pulsed electric field) treatments and CaEP with 5 mM CaCl2 was examined. Finally, to assess the safety of the therapy, we analyzed the N-and E-cadherin localization using confocal laser microscopy. The results of our investigation revealed that depending on the cell line, atorvastatin preincubation decreases the total cholesterol in the steroidogenic cells and induces reorganization of actin nearby the cell membrane. Under low voltage PEFs, actin reorganization is responsible for the increase in the electroporation threshold. However, when subject to high voltage PEF, the lipid composition of the cell membrane becomes the regulatory factor. Namely, preincubation with atorvastatin reduces the cytotoxic effect of low voltage pulses and enhances the cytotoxicity and cellular changes induced by high voltage pulses. The study confirms that the surface tension regulates of membrane permeability under low voltage PEF treatment. Accordingly, to reduce the unfavorable effects of preincubation with atorvastatin, electroporation of steroidogenic cells should be performed at high voltage and combined with a calcium supply.

The Impact of Extracellular Ca2+ and Nanosecond Electric Pulses on Sensitive and Drug-Resistant Human Breast and Colon Cancer Cells.

(1) Background: Calcium electroporation (CaEP) is based on the application of electrical pulses to permeabilize cells (electroporation) and allow cytotoxic doses of calcium to enter the cell. (2) Methods: In this work, we have used doxorubicin-resistant (DX) and non-resistant models of human breast cancer (MCF-7/DX, MCF-7/WT) and colon cancer cells (LoVo, LoVo/DX), and investigated the susceptibility of the cells to extracellular Ca2+ and electric fields in the 20 ns-900 ns pulse duration range. (3) Results: We have observed that colon cancer cells were less susceptible to PEF than breast cancer cells. An extracellular Ca2+ (2 mM) with PEF was more disruptive for DX-resistant cells. The expression of glycoprotein P (MDR1, P-gp) as a drug resistance marker was detected by the immunofluorescent (CLSM) method and rhodamine-123 efflux as an MDR1 activity. MDR1 expression was not significantly modified by nanosecond electroporation in multidrug-resistant cells, but a combination with calcium ions significantly inhibited MDR1 activity and cell viability. (4) Conclusions: We believe that PEF with calcium ions can reduce drug resistance by inhibiting drug efflux activity. This phenomenon of MDR mechanism disruption seems promising in anticancer protocols.

Modifications of Plasma Membrane Organization in Cancer Cells for Targeted Therapy.

Modifications of the composition or organization of the cancer cell membrane seem to be a promising targeted therapy. This approach can significantly enhance drug uptake or intensify the response of cancer cells to chemotherapeutics. There are several methods enabling lipid bilayer modifications, e.g., pharmacological, physical, and mechanical. It is crucial to keep in mind the significance of drug resistance phenomenon, ion channel and specific receptor impact, and lipid bilayer organization in planning the cell membrane-targeted treatment. In this review, strategies based on cell membrane modulation or reorganization are presented as an alternative tool for future therapeutic protocols.