Mechanistic Study of Shikonin on Immunogenic Tumor Cell Vaccine and Its Application in Controlling Rapamycin-induced Tumor Metastasis

• Main Authors: Tien-Jen Lin, 林天仁
• Other Authors: Ning-Sun Yang
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/19080614832166250136

博士 === 國立中興大學 === 生物科技學研究所 === 103 === The dendritic cell (DC)-based cancer vaccine approaches are being actively evaluated for application to cancer immunotherapy. In our previous study, phytochemical shikonin (SK) has been shown to drastically enhance ICD activity in mouse tumor cells treated ex-vivo, and the resultant tumor cell lysate (TCL) can effectively augment such SK-TCL pulsed DC vaccine activity in vivo in anti-tumor activities. For the first part of my dissertation study, I further investigated the specifics and the multi-functional effects of various damaged associated molecular pattern (DAMP) components of the ICD complex for their participation, roles and potential cross talks in activating DCs, as measured by five different functional assays. Among three DAMPs tested, HSP70 and CRT mediate a key role in SK-TCL-induced DC immunity for both CD4+ and CD8+ T cell proliferations in vitro. HSP70 is the most important component, followed by CRT, then HMGB1 in facilitating DC immunity on suppressing metastasis of mouse 4T1 mammary tumors and prolonging survival in test mice. Only HSP70, but not CRT or HMGB1, is effective for the suppression of both granulocytic and monocytic MDSC populations in vivo. Both HSP70 and HMGB1, but not CRT, are essential in activating the expression of three key ICD molecules-associated receptors on test DCs. Each of the three test ICD proteins can exhibit a distinguishable pattern in stimulating the expression of four key chemokines in test DCs. Together, these findings may help formulate new strategies for future cancer vaccine designs. Previous studies indicated that rapamycin (sirolimus) may promote tumor regression activity or enhance immune response against tumor targets. However, rapamycin also exhibits immunosuppressant effects and is hence used clinically as an organ transplantation drug. The chronic use of immunosuppressive drugs in renal transplant recipients may therefore, in my consideration, increase the risk of developing de novo malignancies. The second part of my study was therefore aimed to investigate the effect of rapamycin and phytochemical shikonin, in vitro and in vivo, on growth and metastasis of 4T1 mouse mammary tumors, through quantitative assessment of immunogenic cell death (ICD), autophagy, tumor growth and metastasis. Tumor-bearing mice were immunized with test vaccines to monitor their effect on tumor metastasis. I found that in vivo administration of rapamycin after a tumor-resection surgery drastically increased the metastatic activity of 4T1 tumors. Possible correlation of this finding to human cancers was suggested by epidemiological analysis of data from Taiwan’s National Health Insurance Research Database (NHIRD). I hypothesized that the immunosuppressive activities of rapamycin might also negatively mediate the host immunity, resulting in promotion of tumor metastasis. Since the previous studies of Yang laboratory showed that modified tumor cell lysate (TCL)-pulsed, dendritic cell (DC)-based cancer vaccines can effectively suppress metastasis in mouse tumor models, we assessed whether such vaccines may help offset this rapamycin-promoted metastasis. I observed that shikonin efficiently induced ICD of 4T1 cells in culture, and DC vaccines pulsed with shikonin-treated TCL (SK-TCL-DC) significantly suppressed rapamycin-enhanced metastasis and Treg cell expansion in test mice. In conclusion, rapamycin treatment in mice (and perhaps in humans) can promote metastasis and this side effect may be offset by treatment with a DC-based cancer vaccine.