Up to now, cancer is still one of the major diseases that threaten the survival of mankind, and it is difficult to cure clinically. In addition to single or combined surgery, chemotherapy and radiotherapy, which are commonly used clinically, a number of promising therapeutic strategies have been recently put forward including immunotherapy and gene therapy, photothermal therapy (PTT), photodynamic therapy (PDT), and so on. However, these techniques usually rely on chemical and genetic drugs or exotic nanomaterials to actualize treatments, making them quite difficult or debatable for practical clinical applications in the near future due to the uncertainties of potential biotoxicity and biohazards, and related genetic and ethical issues. Also, immunotherapy and gene therapy are complex and expensive. Therefore, the popularization of these techniques in clinical practice is restricted. Consequently, the development of simple, green, efficient and cheap treatment methods is urgently needed to combat cancer.
Hydrogen (H2), owing to its small molecular size and physiological inertness, resistance to oxidation, and good gas diffusivity in vivo, is considered as a kind of green and endogenous gas. H2 can easily penetrate into the biological membrane to disperse into cytoplasm and other organelles such as the nucleus, mitochondria and so on due to its small size. Dole et al. attempted to use the antioxidation ability of hyperbaric H2 to treat skin squamous cell carcinoma in 1975, but the need to provide hyperbaric H2 with diving medical equipment limited the possible clinical application of hyperbaric H2 in tumor therapy. How to produce H2 non-invasively and sufficiently without using nanomaterials and how to achieve the release of H2 on demand in vivo are two huge challenges facing the H2 therapy of cancers.
Acupuncture is a traditional and unique minimally invasive method to treat diseases in China. It is quite effective for the treatment of systemic diseases, especially arthritis, cervical spondylopathy, psoatic strain and so on, but applying it to the treatment of major diseases, such as cancers, is still a great challenge. In this study, by innovative combined use of the traditional Chinese acupuncture Fe needle (electrode) and in vivo electrochemistry, we developed a simple and precise cancer therapy approach based on selective electrochemical generation of H2 in the tumor region, termed in vivo H2 generation electrochemotherapy (H2-ECT). Very impressively and excitingly, the two acupuncture electrodes inserted into the tumor lump work well at ∼3 V direct current (DC) electric field (which causes minimal damage to healthy tissues), driving the electrochemical H2 generation reaction effectively under the acidic tumor microenvironment and destroys solid tumors. Importantly, the H2-ECT method enables large-scale tumor therapy by applying a gas diffusion effect, avoiding the shortcoming of limited effective area for classic electrochemical reactions. Moreover, due to the puncture positioning and acidic tumor microenvironment (compared to normal tissue), the method provides ideal selectivity and targeting to precisely kill tumors with minimal damage to normal tissue, which is very promising for potential clinical applications. The effectiveness of the method has been demonstrated by successful and fast treatment of glioma and breast cancers in mice in this study.
(A) Schematic diagram of green H2-ECT therapy in vivo. (B) Schematic EC processes of two acupuncture Fe electrode systems showing anodic Fe dissolution and cathodic H2 production. (C–E) The H2-production polarization curves of acupuncture electrodes recorded, respectively, in simulated body fluid (SBF, pH = 6.0) under three different voltages (C), in SBF but with different pH (5.5, 6.0, 6.5, 7.0 and 7.5) at 3 V (D), and in fresh pork (mimicking complex tumor tissue) at two pHs (6.0 and 7.4) (E). (F) Dissolved amount of iron from the anode during the EC process. (G) The dependence of H2 production of the system on various pH levels in SBF recorded at 3 V for 10 min (n = 3). (H, I) The dependence of the amounts of dissolved iron and produced H2 on voltages varying from 0 to 3 V, each for 10 min duration, at pH = 6.0 and 7.4, respectively (n = 3). All the data are represented as mean ± SEM (standard error of the mean). n denotes samples or number of experiments. n = 3, P < 0.0001 representing the statistical significance of different pH values (pH = 7.5 and pH = 6.0), which is evaluated by two-tailed Student's t-test with GraphPad Prism software.
(A) Schematic illustration of C6 tumor xenograft establishment, blank and H2-ECT procedures, and therapeutic outcome (n = 3). (B) Typical photographs of the tumor-bearing mice and tumor lumps, and their control groups, before and after 15 days of first treatment in different conditions (10 min twice a day for first 3 days). Red circle indicates the eliminated tumor in this case. Scale bar: 1.5 cm. (C) The body weights of C6 tumor-bearing nude mice with different groups, recorded every day. (D–F) Tumor weight and tumor volume dissected and relative tumor volume after 15 days of first treatment in different conditions (10 min twice a day for first 3 days, n = 3). All the data are represented as mean ± SEM. n denotes the number of mice. n = 3, P < 0.05 and P < 0.005 representing statistical significance, which is evaluated by Student's two-sided t-test with GraphPad Prism software compared to the control group.
This study reports a green and conceptually new in vivo H2 generation electrochemotherapy (H2-ECT) of tumors, by combined use of Chinese acupuncture Fe needle electrode and in vivo electrochemistry. The method solves the above problems by virtue of the acidic microenvironment of the tumor and in vivo electrochemical technology. The acupuncture electrodes inserted in the acidic tumor area, and working under the applied voltage of 3 V, produce effectively sufficient H2 to damage and kill cancer. The method is highly biosafe without an obvious poisoning effect, solving the difficult problems of material metabolism and biotoxicity in conventional therapeutic methods for clinical applications. By taking advantage of the puncture positioning, gas diffusion effect and self-protection mechanism of H2 generation, the H2-ECT method provides strong selectivity and targeting to effectively and precisely kill tumors, with minimal damage to healthy tissues. The effectiveness of the method has been demonstrated by in vivo treatment of glioma and breast cancers of diseased mice. More importantly, as the volume of the tumor tissue determines the total amount of hydrogen ions within the tumor, the larger tumors provide more hydrogen ions to produce enough hydrogen for effective treatment. Consequently, in principle, irrespective of the size of the tumor, the inherent volume effect of the method can solve the defect of insufficient hydrogen generation during the therapy process.
We use this electrical acupuncture-based therapy to produce local hydrogen, with minimal invasion, good tolerance and high safety. The pilot data is very encouraging.
Guohua Qi, Bo Wang, Xiangfu Song, Haijuan Li, Yongdong Jin A green, efficient and precise hydrogen therapy of cancer based on in vivo electrochemistry. National Science Review.. 2020;7(3):660-670. doi: 10.1093/nsr/nwz199.