ANTITUMOR EFFECT OF INTRATUMORAL INJECTION OF LIPOSOME-ENCAPSULATED G-CSF GENE AND IN SITU BIOLOGICAL CHARACTERISTICS OF THE TREATED TUMOR CELLS

This word was supported by grant from Military Medical Research Foundation of china (96z032). ** To whom correspondence and requests for reprints should be addressed. This is one of papers of the special issue on gene therapy research (Chin J Cancer Res Vol. 9 No. 4 December, 1997). In order to investigate the antitumor effects of the in vivo G CSF gene therapy mediated by liposome and its mechanisms, human G CSF gene was encapsulated into liposome and was directly injected into tumor mass of C 26 colon adenocarcinoma bearing mice. After direct intratumoral injection of liposome encapsulated G CSF DNA, the subcutaneous tumor growth was dramatically inhibited and the survival time was prolonged signifi cantly. Tumor regression could be observed in about 30% of C 26 bearing mice. By the analysis of the antitumor mechanisms, we found that anti G 418 (600ug/ml) clone could be selected from the tumor cells freshly separated from the treated C 26 tumor mass, and secretion of G CSF in the supernatant could be detected. Northern blot also confirmed the expression of hG CSF by the tumor cells. Higher expressions of MHC class I(H 2k d) molecule and ICAM 1 on the tumor cells could be observed. The results demonstrated that liposome can effectively transfect G CSF gene into tumor cells in situ , and then increase the immunogenicity of the tumor cells which may contribute to the activation of the local antitumor immune responses effectively.

Construction and immunogenicity prediction of Plasmodium falciparum CTL epitope minigene vaccine

The minigenes encoding Plasmodium falciparum CTL epitopes restricted to human MHC class I molecular HLA-A2 and HLA-B51, which were both at high frequency among Chinese population, were constructed as mono-epitope CTL vaccines named pcDNA3.1/frand pcDNA3.1/ sh. The minigenes of the two epitopes were then tandem linked to form a dimeric CTL epitope minigene recombinant vaccine. After DNA transfection, the epitope minigenes were expressed respectively in two human cell lines, each bearing one MHC class I molecule named CIR/HLA-A2.1 and K562/HLA-B51. The intraceliular expression of the CTL epitope minigenes not only enhanced the stability of HLA-A2.1 and HLA-B51 molecules but also increased the assemblage of MHC class I molecules on cell surfaces, which testified the specific process and presentation of those endogenous expressed epitopes. For the cells transfected with the dimeric minigene encoding two tandem linked epitopes, the expression and presentation of each epitope were also detected on cell membranes that bore different MHC class I molecules. It meant that the adjacency of the two CTL epitopes did not interfere with the specific process and presentation of each epitope. Compared with the ordinary CTL studies that inoculated synthesized epitope peptides with peripheral blood cells, this work aimed to process the epitopes directly inside HLA class I allele specific human cells, and thus theoretically imitated the same procedure in vivo. It was also an economical way to predict the immunogenicity of CTL epitopes at an early stage especially in laboratories with limited financial resource.