Division of Cardiovascular Surgery, Department of Surgery, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan.
Sci Rep. 2020 Jun 2;10(1):8936. doi: 10.1038/s41598-020-65823-2.
Modulated electro-hyperthermia (mEHT) is a form of mild hyperthermia (HT) used for cancer treatment. The principle utility of HT is the ability not only to increase cell temperature, but also to increase blood flow and associated pO to the microenvironment. While investigational evidence has shown the unique ability of mEHT to elicit apoptosis in cancer cells, in vivo and in vitro, the same trait has not been observed with conventional HT. There is dissension as to what allows mEHT to elicit apoptosis despite heating to only mild temperatures, with the predominant opinion in favor of increased temperature at a cellular level as the driving force. For this study, we hypothesized that in addition to temperature, the amount of electrical energy delivered is a major factor in induction of apoptosis by mEHT. To evaluate the impact of electrical energy on apoptosis, we divided generally practiced mEHT treatment into 3 phases: Phase I (treatment start to 10 min. mark): escalation from 25 °C to 37 °C Phase II (10 min. mark to 15 min. mark): escalation from 37 °C to 42 °C Phase III (15 min. mark to 45 min. mark): maintenance at 42 °C Combinations of mEHT at 18 W power, mEHT at 7.5 W power, water bath, and incubator were applied to each of the three phases. Power output was recorded per second and calculated as average power per second. Total number of corresponding Joules emitted per each experiment was also recorded. The biological effect of apoptotic cell death was assayed by annexin-V assay. In group where mEHT was applied for all three phases, apoptosis rate was measured at 31.18 ± 1.47%. In group where mEHT was only applied in Phases II and III, apoptosis rate dropped to 20.2 ± 2.1%. Where mEHT was only applied in Phase III, apoptosis was 6.4 ± 1.7%. Interestingly, when mEHT was applied in Phases I and II, whether Phase III was conducted in either water bath at 42 °C or incubator at 37 °C, resulted in nearly identical apoptosis rates, 26 ± 4.4% and 25.9 ± 3.1%, respectively. These results showed that accumulation of mEHT at high-powered setting (18 W/sec) during temperature escalation (Phase I and Phase II), significantly increased apoptosis of tested cancer cells. The data also showed that whereas apoptosis rate was significantly increased during temperature escalation by higher power (18 W/sec), apoptosis was limited during temperature maintenance with lower power (7.5 W/sec). This presents that neither maintenance of 42 °C nor accumulation of Joules by mEHT has immediate correlating effect on apoptosis rate. These findings may offer a basis for direction of clinical application of mEHT treatment.
调制的电加热（mEHT）是一种用于癌症治疗的温和加热（HT）形式。HT 的主要用途不仅在于增加细胞温度，还在于增加微环境的血流量和相关的 pO2。虽然研究证据表明 mEHT 具有独特的能力，可以在体内和体外诱导癌细胞凋亡，但常规 HT 并没有观察到这种特性。尽管 mEHT 加热到温和温度，但它能够引发凋亡的原因存在争议，占主导地位的观点认为细胞水平的温度升高是驱动力。在这项研究中，我们假设除了温度之外，输送的电能数量也是 mEHT 诱导细胞凋亡的主要因素。为了评估电能对细胞凋亡的影响，我们将通常的 mEHT 治疗分为 3 个阶段：阶段 I（治疗开始到 10 分钟标记）：从 25°C 升高到 37°C 阶段 II（10 分钟标记到 15 分钟标记）：从 37°C 升高到 42°C 阶段 III（15 分钟标记到 45 分钟标记）：在 42°C 下维持 组合的 mEHT 在 18W 功率、mEHT 在 7.5W 功率、水浴和孵育器应用于这三个阶段中的每一个。每秒记录功率输出并计算每秒平均功率。还记录了每个实验发出的相应焦耳数。通过 Annexin-V 测定法测定凋亡细胞死亡的生物学效应。在 mEHT 应用于所有三个阶段的组中，凋亡率为 31.18±1.47%。在 mEHT 仅应用于第二和第三阶段的组中，凋亡率降至 20.2±2.1%。mEHT 仅应用于第三阶段时，凋亡率为 6.4±1.7%。有趣的是，当 mEHT 仅应用于第一和第二阶段时，无论第三阶段是在 42°C 的水浴中还是在 37°C 的孵育器中进行，凋亡率几乎相同，分别为 26±4.4%和 25.9±3.1%。这些结果表明，在温度升高（第一阶段和第二阶段）期间，mEHT 在高功率设置（18W/sec）下的积累，显著增加了测试癌细胞的凋亡。数据还表明，虽然在更高功率（18W/sec）下的温度升高导致凋亡率显著增加，但在较低功率（7.5W/sec）下的温度维持导致凋亡受限。这表明 mEHT 维持 42°C 或积累焦耳数对凋亡率没有直接的相关影响。这些发现可能为 mEHT 治疗的临床应用方向提供依据。
