| Summary: | 碩士 === 國立臺灣大學 === 醫學工程學研究所 === 104 === Background: The capability of tumors for modulating anti-tumor immune response and orchestrating an immune permissive microenvironment was reported as one of the cancer hallmarks. Therefore, unlike the past concept of cancer therapy which simply aims at killing tumor cells and ignores the tolerance of the host itself to the immune-mediated attack, the emerging strategy for cancer treatment includes not only extirpating all localized tumor cells, but also arousing a systemic, long-lasting, and tumor-specific immune response synchronously, against tumor growth, recurrence and metastasis to achieve the ultimate objective: prolongation of survival times. In addition, ultrasound hyperthermia has been used against various types of cancer and recent studies demonstrated its potential of activating a systemic anti-tumor immune response.
Purpose: To evaluate whether an inducible anti-tumor immunity could be enhanced systemically through combining immunotherapies, in this study we exposed immunogenic moieties from tumor cells by sonicating tumors with pulsed ultrasound hyperthermia (pUSHT) and strengthened the anti-cancer immunity in an all-round way by injecting tumors with OK-432 immunostimulant and adoptive natural killer cell transfer therapy (ACT-NK).
Methods and Materials: A bilateral distant tumor model and a rechallenging tumor model were applied in the studies. For the bilateral distant tumor model, male BALB/c mice were inoculated CT26-luc-GFP tumors on both flanks. The treated tumor (right side) underwent a 10-day treatment including four times of pUSHT (once per 3 days), four times of subcutaneous OK-432 injection (3 hours before each pUSHT) and two times of local ACT-NK injection. The distant untreated tumor (left side) was regarded as a non-visualized small tumor used to assess the degree of anti-tumor immune response. For the rechallenging tumor model, a rechallenge tumor was implanted contralaterally on day 10 after the right-sided tumor had experienced a 5-day treatment (days 0~4) and then a surgical removal on day 5. This model was designed to evaluate whether or not the establishment of a long-term active tumor-specific immune memory is strong enough to prevent recurrence. All data was analyzed statistically by independent T-test or ANOVA with Fisher''s LSD test as a multiple comparison tool alternatively, and survival time was evaluated by the Kaplan-Meier method.
Results: The results of bilateral distant tumor model showed that the tumor growth rate and growth activity of both treated and distant tumors could be significantly inhibited with OK+pUSHT+NK combined therapy (p value＜0.05) and the systemic anti-tumor effect seemed to be prolonged as well. H&E staining results implicated that the necrosis area appeared earlier after the combination treatment. IF staining results also showed a remarkable increase of NK cell infiltration in the central zone of tumors due to the OK+pUSHT+NK therapy. Survival rates significantly increased in both OK+pUSHT and OK+pUSHT+NK groups. In the rechallenging test, all the reimplanted tumors failed to form solid tumors as compared with the control group due to an effective long-lasting anti-tumor immune response which was induced by the combinational treatment.
Conclusion: Combining ultrasound hyperthermia and multiple immunotherapies could lead immune system toward an anti-tumor regulation to overcome an immunosuppressive milieu of tumors. This combined approach has a potential to play an important role in the future cancer treatment of solid malignancy to improve the overall therapeutic benefit.
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