[Current situation and problems of PET examinations].

In recent years, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) has become a remarkable new modality for use in preventive medicine. FDG-PET examinations have many characteristics that are not available through conventional examinations, including the diagnosis of cancer. However, devices and examination techniques that take advantage of the merits of FDG-PET examinations are still required. In addition, many problems related to the management of facilities need to be solved. Therefore, we introduce the current situation of FDG-PET examinations in our facility and discuss our problem-solving efforts. FDG-PET examinations are very useful as screening examinations for cancer, and, in the future, FDG-PET will combine with other techniques and examinations in preventive medicine to provide a general cancer-screening system. For the future development of FDG-PET, we need to focus on the effective utilization of FDG-PET examinations and to establish evidence of their effectiveness. Moreover, we must create guidelines for the improvement of technology and the standardization of PET examination facilities.

CpG oligonucleotides enhance the tumor antigen-specific immune response of a granulocyte macrophage colony-stimulating factor-based vaccine strategy in neuroblastoma.

Granulocyte macrophage colony-stimulating factor (GM-CSF)-transduced autologous tumor cells form the basis of many immunotherapeutic strategies. We tested whether combining this approach with T-helper 1 (Th-1)-like immunostimulatory CpG oligodeoxynucleotides (CpG ODNs) would improve therapeutic efficacy in an established model of murine neuroblastoma. The weakly immunogenic Neuro-2a cell line was used in syngeneic A/J mice. CpG 1826 was tested for its antitumor effect alone and as an adjuvant to Neuro-2a cells retrovirally transduced to express murine GM-CSF (GM/Neuro-2a). Three days after wild-type (WT) tumor cell inoculation, mice in different groups were s.c. vaccinated in the opposite leg with combinations of WT neuro2a, irradiated (15 Gy) WT or GM/Neuro-2a transfectants with or without CpG 1826 (200 micro g). To test for the induction of memory responses, mice that rejected their tumor were rechallenged with WT Neuro-2a (1 x 10(6)) 7 weeks after vaccination. All of the mice in the control (unvaccinated) group died within 3 weeks after Neuro-2a inoculation. Most of the vaccinated groups had only minimal-to-modest antitumor responses, and the mice succumbed to tumor. Tumor growth was remarkably inhibited in the group of mice that received irradiated GM/Neuro-2a plus CpG and four (50%) of eight mice in this group survived tumor free. Tumor-free mice were resistant to further WT tumor cell challenge, indicating a memory response. Mechanistic studies showed that CpG alone induced a favorable Th-1-like cytokine immune response and vaccine-induced tumor cell killing was dependent on both CD4 and CD8 T cells that killed tumor cell targets by apoptosis. These results demonstrate that CpG ODNs enhanced the antitumor effect of irradiated GM-CSF secreting Neuro-2a cells. This vaccine strategy elicits a potent tumor antigen-specific immune response against established murine neuroblastoma and generates systemic neuroblastoma-specific immunity.