Abstract:

Background and purpose: Traditional preparation of subcutaneous transplanted tumor of prostate cancer relies on cell suspension injection. However, there are great limitations. The purpose of this study was to explore the feasibility of developing a new animal model of subcutaneous transplanted prostate cancer with cell sheet technology. Methods: Human prostate cancer DU145 cells were inoculated into a 35 mm temperature sensitive cell culture dish, and the prostate cancer cell sheet was prepared by continuous culture and identified by H-E staining and immunohistochemistry. According to the research purpose, cell suspension group and cell membrane group were set up. DU145 cell suspension was subcutaneously injected into nude mice in cell suspension group, and DU145 cell sheet was subcutaneously injected into BALB/c nude mice in cell sheet group. The BALB/c nude mice were sacrificed 4 weeks after transplantation, and the grafted tumors in both groups were dissected for further histological analysis, including collagen fiber content, local infiltration and angiogenesis. Meanwhile, the common organs of prostate cancer metastasis, such as bone, lung and liver, were dissected to evaluate the systemic metastasis in both groups. Results: DU145 prostate cancer cell sheet could be prepared at 1 week after continuous culture. Histological staining revealed a membrane structure with an average thickness of (32.6±7.5) μm. The DU145 cell sheet was rich in collagen fibrin with high vimentin expression and low E-cadherin expression. H-E staining showed that the tumor structure was dense with obvious infiltration of surrounding muscles in the cell sheet group, while the tumor had more vacuoles and a clear boundary with surrounding tissues in the cell suspension group 4 weeks after subcutaneous transplantation. Moreover, the transplanted tumor volume was significantly higher in the cell sheet group than in the cell suspension group, and the measured tumor volume in the two groups were (0.967±0.129) and (0.437±0.054) cm³ (t = 3.774, P = 0.019 5), respectively. Masson staining showed that the content of blue collagen fiber was significantly higher in the cell sheet group than in the cell suspension group, and the optical densities (D) value of the two groups were 0.023 0±0.001 1 and 0.014 0±0.000 7 (t = 7.022, P = 0.000 1), respectively. Immunohistochemical staining of CD31 showed that the microvascular density per ×200 field in the cell sheet group and the cell suspension group were 53.20±3.56 and 32.40±4.98 (t = 3.392, P = 0.009 5), respectively. Gross anatomy and H-E staining showed no obvious systemic metastasis in the two groups 4 weeks after subcutaneous transplantation. Conclusion: It is feasible and advantageous to develop the animal model of subcutaneous transplanted prostate cancer using cell sheet technology. Compared with traditional cell suspension injection method, the tumor volum was larger, the infiltration degree was deeper with surrounding tissues, the density of new microvessels was higher, and the collagen content was richer, which is more helpful to reveal the real biological characteristics of prostate cancer. It is expected to be applied in the research of molecular genetics of prostate cancer, drug resistance mechanism and drug discovery.

Key words: Cell sheet technology, Prostate cancer model, Ectopic implantation, Tumor microenvironment