Function of immunoadjuvants in laser immunotherapy for treatment of metastatic breast tumors in rats

摘要

Tumor cell destruction usually induces host immune responses, such as local inflammation and increased activities of macrophages and neutrophils. Use of immunoadjuvant can usually enhance such immune activities. Laser immunotherapy is designed to use the combination of laser photothermal and immunological interactions to induce long-term antitumor immunity with the help of immunoadjuvant. It uses a selective hyperthermia for acute tumor destruction through an intratumor administration of indocyanine green and a non-invasive irradiation by an 805-nm laser. The concurrent in situ administration of immunoadjuvant helped achieve the desired effect: tumor eradication and antitumor immunity. The current study further explores the function of immunoadjuvants in laser immunotherapy by testing four different adjuvants: glycated chitosan, complete Freund's adjuvant, incomplete Freund's adjuvant, and c-parvum. Each adjuvant provided long-term tumor cure in the treatment of a metastatic mammary tumor model in rats. However, glycated chitosan and complete Freund's adjuvant were most effective with 25% and 18% long-term cure rates, respectively. Different concentrations of glycated chitosan were also used in treatment of rats bearing metastatic breast tumors. Among the three concentrations tried in our experiments, 1% solution glycated chitosan provided the highest long-term cure rate. Our results showed that in combination with our laser-dye treatment, most adjuvants could serve as immunostimulus in treating the metastatic tumors. However, different immunoadjuvants can have different potency. It is anticipated that other cancer treatment modalities, such as PDT and radiation, as well as chemotherapy, could also achieve the similar effect when combined with the immunoadjuvants as specified in the treatment protocol of laser immunotherapy.