Basic study of polynucleotide vaccine for tumor immunotherapy

[目的]肌肉注射裸露DNA(如质粒型表达载体)可导致编码蛋白在肌肉中表达，当该蛋白为非自身类病毒蛋白时，可激发宿主对该蛋白的免疫应答。在本研究中，我们探讨了这一新方法是否适用于癌症免疫治疗。[方法]首先肌肉注射几种CAT表达载体，用肌肉提取液进行CAT检测，发现CAG启动子和CE启动子在肌肉中的表达效率最高。编码在小鼠黑色素瘤细胞系B16上表达的一种黑色素瘤抗原的cDNAH52。插入CAG启动子下游(PCAGH52)。在小鼠纤维肉瘤细胞系Meth-A中表达的突变型P53蛋白的另一个编码区被插入到CE启动子(PCEP53)的下游。C57BL或BALB/c小鼠每隔一周分别肌肉注射100微克pCAGH52和pCEP53，共3次。最后一次注射一周后，这些小鼠分别皮下注射100000个B16或Meth-A细胞。[结果]治疗组和对照组肿瘤发生率无明显差异，注射DNA不能延长小鼠的生存期。[结论]单纯注射DNA不足以诱导宿主对自体肿瘤的免疫应答。由于DNA注射后产生的蛋白质量很少，需要一些佐剂才能被抗原提呈细胞识别。

[PURPOSE] Intramuscular injection of naked DNA such as plasmid-type expression vector leads to the expression of coded protein in the muscle, and host immune response against the protein is elicited when it is non-self like viral protein. In present study we investigate whether this new method is applicable to cancer immunotherapy or not. [METHOD] At first several kinds of CAT expression vectors were intramusculary injected to perform CAT assay with muscular extract and CAG promoter and CE promoter were found to be most efficient in muscle. cDNA designated as H52, which codes one of melanoma antigens expressed on murine melanoma cell line B16. was inserted downstreams of CAG promoter (pCAGH52). Another cDNA, which codes mutant p53 protein expressed in murine fibrosarcoma cell line Meth-A, was inserted downstreams of CE promoter (pCEp53). C57BL or BALB/c mice were intramusculary injected thrice at one week interval with 100 microgram of pCAGH52 or pCEp53 respectively. One week after the last injection those mice were injected subcutaneously with 100000 cells of B16 or Meth-A respectively. [RESULT] There was no difference in tumor incidence between treated group and control group and survival was not prolonged by DNA injection. [CONCLUSION] Simple DNA injection is not sufficient to elicit host immune response against autologous tumor. Becausae the amount of protein produced after DNA injection is very small, some adjuvant would be necessary to be recognized by antigen presenting cells.