Combination of Therapeutic Ultrasound and CXCL10 Plasmid Transfect for Cancer Tumor Treatment

Background: Surgery, chemotherapy and radiotherapy are the major modalities for cancer tumor treatment, but the development of tumor recurrence is still the major issue for cancer treatment. Immunotherapy is a systemic cancer treatment and it may be useful for reducing relapse of the treated tumors. Purpose: To use ultrasound sonication/hyperthermia to disrupt the microenvironment of tumor and to transfect CXCL10 plasmid into cancer cells, and then the release of CXCL10 from cancer cells to attract and activate natural killer(NK) cells to kill the remaining cancer cells and enhance the immune system to improve the treatment efficacy. Materials and Methods: In in-vitro study, different concentration of CXCL10 was used to evaluate the chemotaxis of NK cells and different ratio of NK cells to cancer cells was used to assess the cytotoxicity of NK cells. The transfect of CXCL10 plasmid into cancer cells by ultrasound sonication was investigated both in-vitro and in-vivo studies. The studies included four groups: control, plasmid only, ultrasound hyperthermia (pUH), and plasmid +pUH. For the in-vivo study, the first treatment was conducted when the tumor grew up to 50 mm3, and treatment was conducted twice a week for two weeks. Body weight and tumor volume were measured every two days. The tumors were also observed by In-vivo Image System (IVIS) during the treatment. Results: The results showed that the chemotaxis of NK cells increased with the concentration of CXCL10, and the cytotoxicity of NK cells to cancer cells also increased with the NK/cancer cell ratio. Both in-vitro and in-vivo results displayed that the concentration of CXCL10 increased after plasmid injection plus ultrasound hyperthermia (plasmid +pUH) and there was a significant difference compared with the other groups. The chemotaxis assay and immunohistochemical staining indicated that the increased tumor infiltration of NK cells in the plasmid +pUH group and it had a significant difference. For the change of tumor volumes, the plasmid +pUH group was significantly smaller than the control group since day 17 and significantly smaller than the plasmid group since day 23. However, there was no significant difference between the pUH group and the plasmid +pUH group. Similar results were observed in the expression of bioluminescence (IVIS image). Conclusion: Ultrasound hyperthermia might damage tumor to disrupt its microenvironment and enhance the CXCL10 plasmid transfection to cancer cells to release CXCL10 to attract NK cells for a better cancer tumor treatment.