免疫基因療法對原位性肝腫瘤之治療機制及探討

Abstract

肝細胞癌為全世界共通的疾病，也長期位居國人的十大死因之一，在目前的傳統治療中以手術及化學療法為主，但大多只對於較小及尚未轉移的癌細胞有較好的治療效果，因此找尋新的治療方法來搭配傳統治療，就成了最近熱門的研究方向。我們實驗室以免疫基因療法來治療原位性肝腫瘤，先以3 x 105 BNL細胞在BALB/c老鼠肝臟建立原位性肝腫瘤，七天後以攜帶IL-12或合併IL-12及GM-CSF的腺病毒作治療，發現都很有效，且合併治療的效果更好，探究其治療機制發現，在IL-12治療組中， NK為清除腫瘤的主要細胞，而合併治療時，最重要的則是NKT，CD8 T細胞次之；另外抗血管新生的作用在兩個治療組中也都有貢獻。 另外，由於Sindbis virus能在哺乳動物細胞內大量表現外來基因，因此我們希望將此載體系統，應用在腫瘤治療的研究。我們將5 x 104會表現腫瘤抗原mAFP的CT26細胞種在BALB/c老鼠的肝臟，七天後將攜帶CRT-tmAFP、VP22-tmAFP及mAFP的Sindbis virus以肌肉注射的方式，連續三天打入老鼠體內作治療，結果發現CRT-tmAFP及VP22-tmAFP具有治療效果(P < 0.05)，mAFP則和控制組無差別。未來希望能進一步改進，讓治療效果更好。

Hepatocellular carcinoma (HCC) is a worldwide disease, and is one of the leading cancers in Taiwan. Traditional therapies, such as surgery or chemotherapy, were effective only on small tumors or non-metastatic tumors. Thus, searching for new therapeutic strategies has become a topic of intensive research recently. In our laboratory, we have used gene therapy strategies to treat orthotopic hepatocellular carcinoma. Mouse hepatoma cells BNL were inoculated in the liver lobe of BALB/c mice to generate orthotopic liver tumor. Then, adenoviruses carrying IL-12 gene or combination of IL-12 and GM-CSF genes were used to treat tumors seven days after tumor cells inoculation. The results showed that both treatments significantly inhibited tumor growth, but the therapeutic effects of combination therapy were better than IL-12 monotherapy. The most important effector cells involved in the IL-12 treatment were NK cells, whereas those in the combination therapy were NKT cells and CD8 T cells. In the second part, we employed Sindbis viral vector, which could express high level of heterologous genes in mammalian cells, to direct tomor-associated antigen (TAA) expression and performed TAA-based immunotherapy. CT26 cells expressing tumor antigen mAFP were inoculated in the liver lobe of BALB/c mice to generate liver tumor. Seven days after tumor inoculation, mice were immunized intramuscularly with Sindbis virus expressing CRT-tmAFP, VP22-tmAFP or mAFP for three constituitive days. The results indicated that fusion of CRT or VP22 with mAFP induced significant immunity against mAFP-expressing tumors. Further studies are still needed to improve the strategy in the future.