Background & objective: 6B11minibody (6B11mini), an anti-idiotypic vaccine against human ovarian cancer, has been proven to induce specific humoral and cellular immunity against ovarian cancer in vivo and in vitro. This study was to investigate the safety and efficacy of using 6B11mini as an antigen to treat ovarian cancer.
Methods: After being loaded with purified 6B11mini, dendritic cells (DCs) were co-cultured with peripheral blood mononucleocytes (PBMNC) and stimulated by various cytokines, including CD3 monoclonal antibody,interleukin-2, interferon-gamma, to obtain 6B11mini-ovarian-cytokine-induced-killer cells (6B11-O-CIK). Tumor-forming ability was determined using soft agar colony-forming assay in vitro and nude mice xenografts in vivo. The acute toxicity of 6B11-OCIK at different doses was observed in BALB/c mice. Cytotoxicity of 6B11-OCIK to different target cells was detected using 51Cr release test in vitro. The ovarian tumor model was established using severe combined immune deficiency (SCID) mice transplanted with human ovarian cancer cell line SKOV3. The tumor growth was detected after injection of 6B11-OCIK into SCID mice. Injection of CIK, PBMNC and physiological saline were used as controls.
Results: After a cultural period of 14 days in soft agar, SKOV3 cell clones were well formed with a ratio of 50%; while 6B11-OCIK, CIK and PBMNC did not form any clones. All nude mice injected with human cervical carcinoma cell line HeLa (positive control) grew tumors after 14 days, and mice injected with 6B11-OCIK, CIK, PBMNC and normal human fetal lung fibroblast WI-38 cells did not form tumors after 13 weeks. BALB/c mice did not show any abnormal response half an hour after the administration of 6B11-OCIK cells at different doses. Mice were sacrificed 13 days after treatments, but no distinct abnormality of the main organs were found. 6B11-OCIK exerted specific cytotoxicity against tumor cells with positive OC166-9, which was related to the limitation of MHC. The tumor weights of SCID mice transplanted with SKOV3 cells were significantly lighter in 6B11-OCIK treatment group than in the saline group(P=0.023); while the tumor weights were not significantly different between the 6B11-OCIK group with CIK and the PBMNC group(P=0.540; P=0.285).
Conclusions: The application of 6B11-OCIK in vivo has reached the safety standard. 6B11-OCIK has the inhibitory effect on the growth of ovarian cancer cells.