Abstract: PD33-11
Sources of Funding: This study was supported by scientific research grants from the Pearl River Nova Program of Guangzhou (No. 2013J2200044), the Project Supported by Guangdong Natural Science Foundation (No. 2015A030313291), and the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. KAKENHI 25861425, 15K20093).

Introduction

Prostate cancer is a major cause of death in men around the world. Despite a variety of treatments, disease progression and metastases still occur in most cases. Given the promising effect of combination with immunotherapy for prostate cancer, the construction of an immunocompetent mouse model for simultaneous monitoring of tumor volume, tumor biomarker and immune cell functions, would be useful for further understanding the mechanism of tumor progression and immune regulation.

Methods

Through genetic engineering techniques, a new cell line, RM9-Luc-pIRES-KLK3 was constructed. The cells were inoculated into immunocompetent mice of strain C57BL/6 via dorsal flank, dorsolateral prostate and tail vein to obtained subcutaneous model, orthotopic model and metastasis model, respectively. Tumor volumes, non-invasive imaging and prostate-specific antigen (PSA) were evaluated. In the metastasis models, either anti-CTLA-4 antibody or PBS was administered to the tumor bearing mice, and the status of circulating immune cells was assessed by flow cytometry.

Results

The new cell line, RM9-Luc-pIRES-KLK3 was successfully constructed and steadily expressed PSA and Luc, which were confirmed by Western blotting and bioluminescence detection in vitro. The level of expression was positively correlated with cell counts. Three days after injection, RM9-Luc-pIRES-KLK3 cells grew readily in the mice and the tumors could be detected by IVIS imaging system from then on. Four days later, PET scan was conducted to confirm the lesions. The intensity of bioluminescence imaging in coronal section and FDG uptake in sagittal slices of PET imaging were totally overlay. Comparing with PBS treated mice; MDSCs and T regs in peripheral blood were significantly decreased in the tumor bearing mice treated with anti-CTLA-4. Meanwhile, the proportion of CD44+CD62? effector and memory T cells on CD3+CD8+ cells were significantly increased by >2–3 times after CTLA-4 blockade compared with the control treatment, as well as IFN? and TNF?.

Conclusions

The presented models were ideally suited for real-time tracking of drug response and imaging of tumor progression and immune function. In comparison with traditional methodologies, this biomarker/imaging-based approach could lead to improved, early, and sensitive assessment of tumor status.

Funding

This study was supported by scientific research grants from the Pearl River Nova Program of Guangzhou (No. 2013J2200044), the Project Supported by Guangdong Natural Science Foundation (No. 2015A030313291), and the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. KAKENHI 25861425, 15K20093).