Purpose: Metastatic activity is one parameter indicating the malignancy of tumor cells. Angiogenesis has now been extensively studied to clarify the mechanisms of tumor growth and metastasis. Vascular endothelial growth factor (VEGF) is an angiogenic cytokine expressed by many human and animal tumors. We studied the role of VEGF in tumor growth by transfecting the VEGF gene into tumor cells and analyzing the survival period of nude mice implanted with these transfected tumor cells.
Materials and Methods:
Cell line: The tumor cell line, OKK-LN, was established from human maxillary squamous cell carcinoma and used in this study. The tumor cells did not produce VEGF in the culture supernatant.
Transfection: OKK-LN cells were stably transfected with sense VEGF165 cDNA or with the vector alone. The full-length VEGF165 cDNA was cloned into an expression vector (pCIneo). The DNA transfection was performed by the lipofection method, and the limiting dilution method was used for cloning. ELISA was used to measure VEGF in the culture supernatant. As a control, OKK-LN cells were transfected with the vector alone without VEGF (OKK-LN/pCIneo). The tumor cells were subcutaneously injected into nude mice (Balb/c nu/nu, 6W), and the survival period and tumor volume were analyzed.
Effects of angio-suppressive agent, TNP-470, and anti-VEGF antibody on tumor growth and angiogenesis: TNP-470 (supplied by Takeda Pharmaceutical Co., Ltd.) and monoclonal anti-human VEGF antibodies were intraperitoneally administered to mice implanted with tumor cells once a week and twice a week for 5 weeks, respectively. The effects of TNP-470 and anti-VEGF antibodies were analyzed by examining tumor size and survival rate and immunohistologically using CD31 monoclonal antibody.
Results: Tumor cells transfected with sense VEGF 165 cDNA (referred to as OKK-LN/pCIneo-VEGF ) produced VEGF in the supernatant permanently, confirming the establishment of a VEGF-producing human cancer cell line. We observed marked tumor growth and a shortened survival period by nine days in the OKK-LN/pCIneo-VEGF group, compared to the control group. The administration of TNP-470 and anti-VEGF antibody significantly suppressed tumor growth. The immunohistological study showed the significant suppression of a number of tumor vessels in anti-VEGF antibody-administered mice.
Conclusion: Our data strongly suggests that VEGF plays an important role in tumor growth and that treatment by anti-VEGF antibody may be a promising strategy against head and neck cancers.