| Popis: |
Vaccination of GM-CSF-transduced tumor cells (GVAX®) have been demonstrated to induce cellular and humoral immune response to tumors in animal studies as well as human clinical trials. We have recently done clinical trials of GVAX® using autologous renal cell cancer (RCC) cells in Japan. Four out of six advanced RCC who were entered to our clinical gene therapy trial were injected with GVAX. First of all, to examine whether the therapeutic regimen induced antitumor antibody responses in them, we compared the serum antibody reactivity against autologous tumor cell lysates before and after the vaccinations by immunoblot analysis. Using post-therapy serum as probes, high molecular weight proteins of around 250 kDa generated clear signals, whereas the pre-vaccination serum showed no or only weak signals at the same position, suggesting that the gene therapy induced an antibody response in them. In three of them (Cases 2–4), the induction of antibodies immunoreactive with the 250 kDa proteins was significant, while the results were less clear in Case 1. The suspected common antigen was actually demonstrated in both RCC lysates and normal renal cell lysates, and in human lip-derived fibroblasts, but not in H69 lung cancer cells. Furthermore, the changes in the magnitude of the antibody immunoreactivity over time were analyzed using serum from Case 2. The strongest signal was observed in serum obtained at 67 days after the initial vaccination, between the 5th and 6th vaccinations. This response was maintained from day 67 until day 281, just after the 17th vaccination, although it decreased slightly. After the last vaccination, the immunoreactivity remained at a lower level, although it did not disappear completely. Secondly, based on the results of Western blot analysis, we applied SEREX, the serological identification of antigens by recombinant expression cloning, using patient's serum. We constructed RCC cDNA-expression library on lambda phage vector, and screened the plaques with Case 2 serum pooled between days 25 and 80 after the first vaccination. The mRNA source was Case 2 autologous cultured tumor cells. Sequencing analysis of isolated positive clones (twelve in total) revealed some of them were reported as SEREX defined antigen in previous studies but others were not. Recombinant antigen proteins, fused to epitope tags, were expressed in E. coli and the antibody titration of sera from patients or healthy donner is now going on. The identification of the new anti-RCC antigen might cast a new light on the treatment of patients suffered from advanced RCC. |
