| Research Abstract |
New therapeutic vectors using transcriptional targeting were made for the treatment of advanced hepatocellular carcinoma with intra- and extra-hepatic metastases. Alpha-fetoprotein (AFP) is well known to be specifically expressed in hepatocellular carcinoma. We modified the promoter region of AFP gene by removal of non-functioning parts and enhancing the enhancer sequences, and put the new controlling element of AFP gene into an adenoviral vector. Therapeutic effect and expression analysis of the vectors was tested in transplanted hepatocellular carcinoma in athymic nude mice. Herpes simplex. virus thymidine kinase gene was used as a therapeutic gene.
Effect of transcriptional targeting was demonstrated by the AFP controlling element, the anti-tumor effect was low due to the weak promoter activity. Thus, we introduced cre-loxP system into the vector. By the cre-loxP-AFP system, specific and high expression can be obtained in cultured cells and mouse tumors including intra- and extra-hepatic lesions.
However, two viruses need to infect simultaneously a cell, and more than 25 MOI are necessary to enable the system. These results indicate large amount of adenovirus should be introduced in a body, which may cause serious problem in future.
When HVJ liposome, which is known to have less toxicity, was used with AFP controlling element, repeated administration of the vector confer significant anti-tumor effect in intra-hepatic metastasis model. Transcriptional targeting using AFP promoter is, thus, promising for the treatment of advanced hepatocellular carcinoma with intra- and extra-hepatic metastases.
|
