| Summary: | 博士 === 中原大學 === 生物醫學工程研究所 === 107 === Hyperthermia has long been used to treat cancers with concurrent chemotherapy or radiotherapy with synergistic effect. Oncothermia or modulated electro-hyperthermia (mEHT) is a type of heating method utilizing capacitive coupled 13.56MHz amplitude-modulated radiofrequency. mEHT can raise the temperature of the tumor region up to high fever range (39-42oC) and autofocus the electric field energy on cancer cell membrane, resulting massive apoptosis of cancer cells.
The effects of mEHT on dendritic cell immunotherapy and LipoDox® drug delivery were investigated to evaluate whether addition of mEHT can enhance cancer cell killing. This study utilized in vivo and in vitro CT26 murine colorectal cancer model. The inhibition of growth of the tumor and the systemic anti-tumor immune response were evaluated. The inoculated tumor was heated to a core temperature of 42°C for 30 min and matured synergetic dendritic cells (DCs) were intratumorally injected 24 hours following mEHT was applied.
The second part of the study was designed to compare the enhancement of liposome-encapsulated doxorubicin (LipoDox®) uptake by cancer cells after water bath control and mEHT treatment. Drug-uptake by cancer cells were measured by doxorubicin fluorescence technique. Viable cell yield was determined via Trypan Blue exclusion method. Various substrates were used to investigate the mechanism of drug-uptake enhancement. The in vitro experiment was used to confirm the tissue infiltration of Lipodox® and its therapeutic effect.
mEHT induced significant apoptosis and enhanced the release of heat shock protein70 (Hsp70) in CT26 cancer cells. mEHT-DCs combined treatment significantly inhibited inoculated CT26 tumor growth when compared with DCs or mEHT treatment alone. The rechallenging experiment showed systemic tumor protection effect in mice that were treated with mEHT-DCs. mEHT-DC treatment also increased the number of leukocytes, macrophages and eosinophil infiltration, evidenced by immunohistochemical staining of CD45, F4/80 and eosinophil markers. Cytotoxic T cell and ELISpot assay showed a tumor-specific T cell activity.
The effect of mEHT on LipoDox® drug delivery showed a significant enhancement of LipoDox® uptake of doxorubicin fluorescence when compared with 37°C or 42°C water bath treatment. In vivo experiment, mEHT treated tumor tissue sections revealed the highest doxorubicin uptake. Wortmannin was used to inhibit the macropinocytosis pathway and 70kDa Dextran-FITC was served as uptake substance. The uptake of Dextran-FITC by cancer cells was significantly increased after mEHT treatment whereas such enhancement was significantly inhibited by wortmannin.
mEHT induces tumor cell apoptosis and enhances the release of Hsp70 from heated tumor cells, better than conventional hyperthermia. mEHT creates a favorable tumor microenvironment that improves the success rate of intra-tumor DC immunotherapy. In addition, macropinocytosis is the main route of mEHT-induced LipoDox® uptake. mEHT enhanced uptake of Lipodox® may increase the therapeutic effect. This finding has potential clinical application and need further investigation.
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