Human Dendritic Cells Transfected With RNAs From Gastric Garcinoma Induce Specific Antitumor Immunity

Objective: To investigate whether total RNAs from gastric cancer cell line and surgical specimen with gastric carcinoma can transfect DC directly and induce specific antitumor immunity, to explore the possibility of such an approach in the biological treatment of gastric carcinoma and also to set the base for future immunotherapy of gastric carcinoma using DCs transfected with screened and amplified genes differentially expressed in gastric carcinoma. Methods: 1. Total RNAs were isolated from the cultured gastric cancer cell line AGS, a surgical specimen with gastric carcinoma and its peritumor tissue. 2.100 ml peripheral blood drawn from a healthy volunteer mobilized with 50ug of rhGM-CSF 2 days before was used for the preparation of peripheral blood mononuclear cells(PBMNC). 3. The adherent fraction of PBMNC was cultured with the presence of relevant cytokines (rhGM-CSF 800u/ml,rhIL-4 500u/ml) to generate DCs, which were transfected (or not transfected as control) with RNAs of various origins. 4. The four kinds of pulsed DCs were cocultured with the nonadherent fraction of PBMNC for T cell priming. 5. The MTT method was used to measure the killing rates of AGS and SoRb-70 by the activated lymphocytes. Results: Intact RNAs of high purities with clear 18S and 28S bands were successfully extracted from AGS, gastric cancer specimen and its peritumor tissue. After mobilization with rhGM-CSF, 100 ml venous blood from a healthy volunteer yielded 3.2 X108 PBMNCs. After in vitro culture and amplification, 4.4 X 106 DCs with typical morphology and phenotype were harvested. Transfected with the RNAs from AGS and gastric cancer specimen, DCs were able to induce potent tumor specific CTL responses. The lytic killing rates of CTLs activated by AGS RNAs transfected DCs were 94.54% and 1.53% for AGS and SoRb-70, respectively ,at an effector: target ratio of 20:1. Those of CTLs activated by DCs transfected with tumor specimen RNAs were 92.88% and 1.16% for the two cancer cell lines, respectively. The killing rates of the peritumor RNA transfection group were 8.77% and 1.27% for the two cell lines. Whereas those of the blank control group were 1.34% and 1.70% for the cell lines. Conclusions: Intact RNAs can be extracted with the method from gastric carcinoma cell line AGS, gastric cancer specimen and peritumor tissue. Without the presence of transfection agents, DCs can be successfully transfected with RNAs fromvarious sources. Tumor RNA transfection of DCs can fulfill the uptake and presentation process of total rumor antigens, and can induce potent antitumor immunity. Our research and those of others' demonstrate DCs transfected with tumor RNA is a promising approach for cancer therapy. Using tumor RNA transfected DCs to treat gastric carcinoma doesn't need to know the exact antigen profiles and can avoid the contamination of surgical specimens, enabling the strategy of whole antigen- loaded DCs to be used in immunotherapy for contaminated cancers (including gastric carcinoma). This study represents the first report in the field.