Animal models for treatment of unresectable liver tumours: a histopathologic and ultra-structural study of cellular toxic changes after electrochemical treatment in rat and dog liver

Manganese-Doped Potassium Chloride Nanoelectrodes to Potentiate Electrochemical Immunotherapy

Hypochlorous acid (HClO), as a powerful oxidizer, is obtained from the oxidation of Cl- ions during the electrochemical therapy (EChT) process for cancer therapy. However, the extracellular generated HClO is inadequate to inhibit effective tumor cell death. Herein, manganese-doped potassium chloride nanocubes (MPC NCs) fabricated and modified with amphipathic polymer PEG (PMPC NCs) to function as massive three-dimensional nanoelectrodes (NEs) were developed to enhance the generation of HClO for electrochemical immunotherapy under an alternating electric field. Under an square-wave alternating current (AC) electric field, the generation of HClO was boosted by PMPC NEs due to the enlarged active surface area, enhanced mass transfer rate, and improved electrocatalytic activity. Notably, PMPC NEs upregulated the intracellular HClO concentration to induce robust immunogenic cell death (ICD) under an AC electric field. Meanwhile, the electric-triggered release of Mn2+ effectively stimulated dendritic cells (DCs) maturation. In vivo results illustrated that PMPC-mediated EChT inhibited tumor growth and triggered the promotion of the immune response to regulate the tumor immune microenvironment. Based on the potent antitumor immunity, PMPC-mediated EChT was further combined with an immune checkpoint inhibitor (αCTLA-4) to realize combined EChT-immunotherapy, which demonstrated enhanced tumor inhibition of the primary tumors and an abscopal effect on distant tumors. To summarize, our work highlights the application of electrochemical-immunotherapy technology in tumor therapy.

Electrochemical therapy (EChT) of cancer tumor with an external anode, a way to achieve pathological complete response

There is a critical need for re-evaluation of electrochemical therapy (EChT) approaches of solid tumors to address the challenges of the currently used method: incomplete pathological response. The coexistence of anode and cathode in the tumor region resulted in acid-alkaline mixation (buffered pH) when the electrodes are so near each other (d < 1 cm), and in the non-affected lesions when the electrodes are far from each other (d > 1 cm), both have resulted in intact tumoral lesions in EChT field. Here, we presented a designation model study of EChT with an external anode out of the tumor and filled the tumor with dense distribution of cathode electrodes to completely destroy the tumoral lesions without any remaining vital tumoral residues. Anode was located in a biological ionic gel chamber (located on top of the skin) which mediates the ionic interface between the external anode and intratumoral cathode. Our newly reported method can solve the lack of a comprehensive therapeutic guideline for any solid tumors. A remarkable increase in the efficiency of EChT without any over-treating was achieved by alkaline therapy of the tumor (without any limitation in locating cathodic needles all over the tumor) and an external acidic region on top of the skin in a cylindrical gel chamber. We found that the destructive volumes and treating ability of mice tumors by this newly represented method were more significant than the conventional EChT method in fewer therapy sessions and no damage to the skin (both anode and cathode electrodes inside the tumor) (P < 0.05). Results of this study applied to mouse model tumors shed new light on returning attraction to EChT as a valuable complementary method for treating different types of solid breast tumors.

Beyond Photo: Xdynamic Therapies in Fighting Cancer

Reactive oxygen species (ROS)-related therapeutic approaches are developed as a promising modality for cancer treatment because the aberrant increase of intracellular ROS level can cause cell death due to nonspecific oxidation damage to key cellular biomolecules. However, the most widely considered strategy, photodynamic therapy (PDT), suffers from critical limitations such as limited tissue-penetration depth, high oxygen dependence, and phototoxicity. Non-photo-induced ROS generation strategies, which are defined as Xdynamic therapies (X = sono, radio, microwave, chemo, thermo, and electro), show good potential to overcome the drawbacks of PDT. Herein, recent advances in the development of Xdynamic therapies, including the design of systems, the working mechanisms, and examples of cancer therapy application, are introduced. Furthermore, the approaches to enhance treatment efficiency of Xdynamic therapy are highlighted. Finally, the perspectives and challenges of these strategies are also discussed.

Nanoporous platinum needle for cancer tumor destruction by EChT and impedance-based intra-therapeutic monitoring

Herein, we present a new design on the Single Needle Electrochemical Therapy (SNEChT) method by introducing some major improvements, including a nanoporous platinum electrode, tunable in situ anode size that depends on the width and location of the tumor, and the capability of measuring the efficacy of therapy based in intra-therapeutic impedance recording by the same EChT needle. It could have significant implications in optimizing EChT operative conditions. The nanoporous Pt electrode increased the interactive surface with a tumor, and produced a higher amount of current with lower stimulating DC voltage. The tunable anode size prevents the over-acidification of treated or non-desired lesions. Hence, this feature reduced the over distribution of tissue. Monitoring the impedance during the therapy clearly informs us about the local destruction of the tumor in each location. Thus, we can be informed about the threshold of tissue acidosis with the lowest electrical stimulation. The insertion of one needle with a tunable anode length for both precise therapy and impedance-based intra-therapeutic monitoring will shed new light on the applications of EChT.

Platinum Nanoparticles to Enable Electrodynamic Therapy for Effective Cancer Treatment

Electrochemical therapy (EChT), by inserting electrodes directly into tumors to kill cancer cells under direct current (DC), is clinically used in several countries. In EChT, the drastic pH variation nearby the inserted electrodes is the main cause of tumor damage. However, its limited effective area and complex electrode configuration have hindered the clinical application of EChT in treating diverse tumor types. Herein, a conceptually new electric cancer treatment approach is presented through an electro-driven catalytic reaction with platinum nanoparticles (PtNPs) under a square-wave alternating current (AC). The electric current triggers a reaction between water molecules and chloride ions on the surface of the PtNPs, generating cytotoxic hydroxyl radicals. Such a mechanism, called electrodynamic therapy (EDT), enables effective killing of cancer cells within the whole electric field, in contrast to EChT, which is limited to areas nearby electrodes. Remarkable tumor destruction efficacy is further demonstrated in this in vivo EDT treatment with PtNPs. Therefore, this study presents a new type of cancer therapy strategy with a tumor-killing mechanism different from existing methods, using nanoparticles with electrocatalytic functions. This EDT method appears to be minimally invasive, and is able to offer homogeneous killing effects to the entire tumor with a relatively large size.

Dose-response study for the highly aggressive and metastatic primary F3II mammary carcinoma under direct current

Electrochemical treatment has been suggested as an effective alternative to local cancer therapy. Nevertheless, its effectiveness decreases when highly aggressive primary tumors are treated. The aim of this research was to understand the growth kinetics of the highly aggressive and metastatic primary F3II tumor growing in male and female BALB/c/Cenp mice under electrochemical treatment. Different amounts of electric charge (6, 9, and 18 C) were used. Two electrodes were inserted into the base, perpendicular to the tumor's long axis, keeping about 1 cm distance between them. Results have shown that the F3II tumor is highly sensitive to direct current. The overall effectiveness (complete response + partial response) of this physical agent was ≥75.0% and observed in 59.3% (16/27) of treated F3II tumors. Complete remission of treated tumors was observed in 22.2% (6/27). An unexpected result was the death of 11 direct current-treated animals (eight females and three males). It is concluded that direct current may be addressed to significantly affect highly aggressive and metastatic primary tumor growth kinetics, including the tumor complete response. Bioelectromagnetics. 39:460-475, 2018. © 2018 Wiley Periodicals, Inc.

Tissue Damage, Temperature, and pH Induced by Different Electrode Arrays on Potato Pieces (Solanum tuberosum L.)

One of the most challenging problems of electrochemical therapy is the design and selection of suitable electrode array for cancer. The aim is to determine how two-dimensional spatial patterns of tissue damage, temperature, and pH induced in pieces of potato (Solanum tuberosum L., var. Mondial) depend on electrode array with circular, elliptical, parabolic, and hyperbolic shape. The results show the similarity between the shapes of spatial patterns of tissue damage and electric field intensity, which, like temperature and pH take the same shape of electrode array. The adequate selection of suitable electrodes array requires an integrated analysis that involves, in a unified way, relevant information about the electrochemical process, which is essential to perform more efficiently way the therapeutic planning and the personalized therapy for patients with a cancerous tumor.

Amorphous liquid metal electrodes enabled conformable electrochemical therapy of tumors

Electrochemical treatment of tumors (EChT) has recently been identified as a very effective way for local tumor therapy. However, hindered by the limited effective area of a single rigid electrode, multiple electrodes are often recruited when tackling large tumors, where too many electrodes not only complicate the clinical procedures but also aggravate patients' pain. Here we present a new conceptual electric stimulation tumor therapy through introducing the injectable liquid metal electrodes, which can adapt to complex tumor shapes so as to achieve desired therapeutic performance. This approach can offer evident merits for dealing with the complex physiological situations, especially for those irregular body cavities like stomach, colon, rectum or even blood vessel etc., which are hard to tackle otherwise. As it was disclosed from the conceptual experiments that, Unlike traditional rigid and uncomfortable electrodes, liquid metal possesses high flexibility to attach to any crooked biological position to deliver and adjust targeted electric field to fulfill anticipated tumor destruction. And such amorphous electrodes exhibit rather enhanced treatment effect of tumors. Further, we also demonstrate that EChT with liquid metal electrodes produced more electrochemical products during electrolysis. Transformations with the shapes of liquid metal provided an easily regulatable strategy to improve EChT efficiency, which can conveniently aid to achieve better output compared to multiple electrodes. In vivo EChT of tumors further clarified the effect of liquid metal electrodes in retarding tumor growth and increasing life spans.

NaK alloy-induced in vivo tumor ablation therapy

PURPOSE

Alkali metal ablation is newly emerging as an effective, economic and minimally invasive ablation therapy. This study is dedicated to demonstrate the high efficiency of NaK alloy ablation on in vivo tumors with different stages in mice.

MATERIAL AND METHODS

Panc02 tumor cells were injected into 21 female C57B/L mice, which were divided into three groups. Two experimental groups of mice received the same percutaneous NaK alloy injection for a week apart. The inner temperature response and surface temperature distribution were measured using a thermal couple and an infrared camera. After each ablation experiment, two mice in each group were chosen randomly to make pathological sections. The tumor volumes were measured once every two days. At the end, all tumors were cut off to calculate the tumor inhibition rates.

RESULTS

The NaK alloy-induced ablation therapy produced an obvious temperature increase (85 °C) in the ablation region and the high temperature distribution was relatively concentrated. The histopathology sections showed that developing stage tumors received incomplete destruction of the malignant cells compared with early stage tumors. The tumor inhibition rate in the early and developing tumor treatment groups were 88.5% and 67.6%, respectively.

CONCLUSIONS

This technology provides a nearly thorough ablation treatment for early stage tumors and also a palliative treatment for developing tumors.

Magnetic Resonance-Monitored Coaxial Electrochemical Ablation--Preliminary Evaluation of Technical Feasibility

PURPOSE

To evaluate the technical feasibility of a coaxial electrode configuration to rapidly create a mechanically defined electrochemical ablation zone monitored by magnetic resonance (MR) imaging in real time.

MATERIALS AND METHODS

A direct current generator supplied the nitinol cathode cage and central platinum anode for coaxial electrochemical ablation. Safety and efficacy were evaluated by measuring local pH, temperature, and current scatter in saline solutions. Ablation zone diameters of 3-6 cm (n = 72) were created on ex vivo bovine liver and verified by gross pathology. Feasibility of MR monitoring was evaluated using 8 swine livers to create ablations of 3 cm (n = 12), 4 cm (n = 4), and 5 cm (n = 4) verified by histology.

RESULTS

Local pH was 3.2 at the anode and 13.8 at the cathode. Current scatter was negligible. Ablation progress increased relative to local ion concentration, and MR signal changes corresponded to histologic findings. In the ex vivo model, the times to achieve complete ablation were 15 minutes, 20 minutes, 35 minutes, and 40 minutes for diameters of 3 cm, 4 cm, 5 cm, and 6 cm, respectively. Ablation times for the in situ model were 15 minutes, 35 minutes, and 50 minutes for 3 cm, 4 cm, and 5 cm, respectively.

CONCLUSIONS

The coaxial configuration mechanically defined the electrochemical ablation zone with times similar to comparably sized thermal ablations. MR compatibility allowed for real-time monitoring of ablation progress.

Electrochemical red-ox therapy of prostate cancer in nude mice

Minimally invasive therapies are increasingly in demand for organ-confined prostate tumors. Electrochemical therapy (EChT) is attractive, as it relies on locally-induced reduction-oxidation reactions to kill tumor cells. Its efficacy for prostate cancer was assessed in human PC-3 and LNCaP tumor xenografts growing subcutaneously in nude mice (n = 80) by applying 2 Stainless Steel vs. 4 Platinum-Iridium (Pt-Ir) electrodes to deliver current densities of 10 to 35 mA/cm(2) for 30 or 60 min. The procedure was uneventful in 90% of mice. No difference in tumor vs. body temperature was observed. Changes at electrode-tumor junctions were immediate, with dryness and acidity (pH2-3) at the anode and oedema and alkalinity (pH10-12) at the cathode. This was accompanied by cellular alterations, found more pronounced at the cathode. Such acidic and alkaline conditions were cytotoxic in vitro and dissolved cells at pH>10. In mice, tumor destruction was extensive by 24h with almost undetectable blood prostate specific antigen (LNCaP model) and covered the whole tumor surface by 4 days. EChT was most efficient at 25-30 mA/cm(2) for 60 min, yielding the longest recurrence-free survival and higher cure rates, especially with 4 Pt-Ir electrodes. EChT is a promising option to optimize for organ-confined prostate tumors.

Combining Electrolysis and Electroporation for Tissue Ablation

Electrolytic ablation is a method that operates by delivering low magnitude direct current to the target region over long periods of time, generating electrolytic products that destroy cells. This study was designed to explore the hypothesis stating that electrolytic ablation can be made more effective when the electrolysis-producing electric charges are delivered using electric pulses with field strength typical in reversible electroporation protocols. (For brevity we will refer to tissue ablation protocols that combine electroporation and electrolysis as E(2).) The mechanistic explanation of this hypothesis is related to the idea that products of electrolysis generated by E(2) protocols can gain access to the interior of the cell through the electroporation permeabilized cell membrane and therefore cause more effective cell death than from the exterior of an intact cell. The goal of this study is to provide a first-order examination of this hypothesis by comparing the charge dosage required to cause a comparable level of damage to a rat liver, in vivo, when using either conventional electrolysis or E(2) approaches. Our results show that E(2) protocols produce tissue damage that is consistent with electrolytic ablation. Furthermore, E(2) protocols cause damage comparable to that produced by conventional electrolytic protocols while delivering orders of magnitude less charge to the target tissue over much shorter periods of time.

Antitumor effects of electrochemical treatment

Electrochemical treatment is an alternative modality for tumor treatment based on the application of a low intensity direct electric current to the tumor tissue through two or more platinum electrodes placed within the tumor zone or in the surrounding areas. This treatment is noted for its great effectiveness, minimal invasiveness and local effect. Several studies have been conducted worldwide to evaluate the antitumoral effect of this therapy. In all these studies a variety of biochemical and physiological responses of tumors to the applied treatment have been obtained. By this reason, researchers have suggested various mechanisms to explain how direct electric current destroys tumor cells. Although, it is generally accepted this treatment induces electrolysis, electroosmosis and electroporation in tumoral tissues. However, action mechanism of this alternative modality on the tumor tissue is not well understood. Although the principle of Electrochemical treatment is simple, a standardized method is not yet available. The mechanism by which Electrochemical treatment affects tumor growth and survival may represent more complex process. The present work analyzes the latest and most important research done on the electrochemical treatment of tumors. We conclude with our point of view about the destruction mechanism features of this alternative therapy. Also, we suggest some mechanisms and strategies from the thermodynamic point of view for this therapy. In the area of Electrochemical treatment of cancer this tool has been exploited very little and much work remains to be done. Electrochemical treatment constitutes a good therapeutic option for patients that have failed the conventional oncology methods.

Patterns of histological changes following hepatic electrolytic ablation in an ex-vivo perfused model

Electrolytic ablation (EA) destroys the liver by releasing toxic radicles and producing modifications in the local pH without increasing the tissue temperature. We assessed the histological changes produced by EA using an ex-vivo perfused model. Five porcine livers were harvested, preserved in ice and reperfused for six hours in an extracorporeal circuit using autologous normothermic blood. One hour after reperfusion EA was performed and liver biopsies collected at the end of the experiments. The main necrotic zone consisted of coagulative necrosis, sinusoidal dilatation and haemorrhage with an unusual morphological pattern. The coagulative necrosis and haemorrhage affected mainly the peripheral area of the lobule with relative sparing of the area surrounding the centrilobular vein. Contrasting with this sinusoidal dilatation appeared to be more prominent in the centrilobular area. EA produces patterns of tissue destruction that have not been observed with the more commonly used thermal techniques. Further studies should obtain more information about the influence of adjacent biliary and vascular structures so that appropriate clinical trials can be designed.

Bimodal electric tissue ablation (BETA)--effect of reversing the polarity of the direct current on the size of ablation

BACKGROUND

Bimodal electric tissue ablation (BETA) is a new technique that uses the direct current in electrolysis to improve the efficacy of radio frequency (RF) ablation. It was hypothesized that attaching the cathode of the electrolytic circuit to the RF electrode will increase the tissue hydration, therefore delaying tissue desiccation during ablation. Consequently, the ablation process can continue for a longer period of time and produce larger ablations. This hypothesis was tested by reversing the polarity of the electrolytic circuit, which theoretically would cause tissue desiccation and therefore produce smaller ablations. This new setup is called reversed polarity bimodal electric ablation (RP-BEA).

MATERIALS AND METHODS

Three types of ablations standard radiofrequency ablation (RFA), BETA, and RP-BEA) were tested in a pig liver model. In BETA and RP-BEA, 9 V of direct current were provided for 10 min, after which the rf generator were switched on and both electrical circuits allowed to run concurrently. In all three setups, ablations were continued until "roll-off." The size of ablation was measured and compared with each other.

RESULTS

The duration of ablation was significantly shorted in RP-BEA compared with standard RFA and BETA (48 s verus 148 s and 84 s, respectively, P = 0.004). The sizes of ablations in RP-BEA were also significantly smaller compared with standard RFA and BETA-skin.

CONCLUSION

RP-BEA caused tissue desiccation resulting in a shorter duration of ablation and smaller ablations. Therefore, the theory that BETA increases ablation size due to the effects of increased tissue hydration around the rf electrode is correct.

Intrahepatic radiofrequency ablation versus electrochemical treatment ex vivo

BACKGROUND

Radiofrequency ablation (RFA) and electrochemical treatment (ECT) are two methods of local liver tumor ablation. A reproducible perfusion model allowed us to compare these methods when applied in proximity to vascular structures.

MATERIAL AND METHODS

In a porcine liver perfusion model, we used RFA (group A) and ECT (group B) to perform ablations under ultrasound guidance within 10 mm of a vessel and examined the induced necrosis macroscopically and histologically.

RESULTS

We created 83 lesions (RFA: 59, ECT: 24) in 27 livers. In group A (mean liver weight: 2046 g), perfusion was macroscopically found to limit necrosis in 52.5% of the procedures. Histology demonstrated the destruction of only 30.4% of the vessel walls within the ablation areas. In group B (mean liver weight: 1885 g), we detected reproducible and sharply demarcated ablation areas both macroscopically and histologically. Necrosis was unaffected by nearby vessels. No viable cells were found perivascularly. Histology showed destruction of the vascular endothelium without any discontinuities. We measured pH values of 0.9 (range: 0.6-1.8) at the anode and 12.2 (range: 11.4-12.6) at the cathode. Treatment time was 100 min when a charge of 300 coulombs was delivered.

CONCLUSIONS

Electrochemical treatment is a method of ablation that creates reproducible and predictable volumes of necrosis. It produces sharply demarcated areas of complete necrosis also in perivascular sites. ECT, however, requires much longer treatment times than RFA. In our model, the effects of RFA were considerably limited by perfusion, which caused incomplete areas of necrosis in proximity to vessels.

Electrochemical treatment: An investigation of dose-response relationships using an isolated liver perfusion model

BACKGROUND/AIM

Ablative techniques such as radiofrequency ablation or non-thermal electrochemical treatment (ECT) are used to manage unresectable liver metastases. Although ECT is not affected by the cooling effect from adjacent vessels, there is a paucity of data available on ECT.

MATERIALS AND METHODS

We used porcine livers to establish an organ model with portal venous and hepatic arterial blood flow for a standardized analysis of the relationship between dose (electric charge) and response (volume of necrosis).

RESULTS

This model allowed us to study pressure-controlled perfusion of portal venous and hepatic arterial circulation in the absence of a capillary leak. A specially designed guiding template helped us place platinum electrodes at reproducible locations. With two electrodes, there was a linear relationship between charges of no more than 200 C and necrosis. The relationship was logarithmic at charges of 400-600 C. Larger electrode spacing led to a significant increase in necrosis. We measured pH values of 0.9 (range: 0.6-1.3) at the anode and 12.6 (range: 11.6-13.4) at the cathode.

CONCLUSIONS

Using a perfusion model, we established an experimental design that allowed us to study ECT in the liver of large animals without experiments on living animals. An electrode template helped us improve the standardized analysis of dose-response relationships. ECT created reproducible and sharply demarcated areas of necrosis, the size of which depended on the charge delivered as well as on the number and spacing of electrodes. Doses higher than 600 C require longer treatment times but do not increase the area of necrosis (logarithmic dose-response relationship).

Experimental application of electrolysis in the treatment of liver and pancreatic tumours: principles, preclinical and clinical observations and future perspectives

BACKGROUND

Electrolytic ablation (EA) is a treatment that destroys tissues through electrochemical changes in the local microenvironment. This review examined studies using EA for the treatment of liver and pancreatic tumours, in order to define the characteristics that could endow the technique with specific advantages compared with other ablative modalities.

METHODS

Literature search of all studies focusing on liver and pancreas EA.

RESULTS

A specific advantage of EA is its safety even when conducted close to major vessels, while a disadvantage is the longer ablation times compared to more frequently employed techniques. Bimodal electric tissue ablation modality combines radiofrequency with EA and produced significant larger ablation zones compared to EA or radiofrequency alone, reducing the time required for ablation. Pancreatic EA has been investigated in experimental studies that confirmed similar advantages to those found with liver ablation, but has never been evaluated on patients. Furthermore, few clinical studies examined the results of liver EA in the short-term but there is no appropriate follow-up to confirm any survival advantage.

CONCLUSIONS

EA is a safe technique with the potential to treat lesions close to major vessels. Specific clinical studies are required to confirm the technique's safety and eventually demonstrate a survival advantage.