Eliciting effective tumor immunity against ovarian cancer by cancer stem cell vaccination

Advanced ovarian cancer (OC) patients have limited benefit from current relevant cytotoxic and targeted therapies following debulking surgery. Therefore, new therapeutic strategies are in urgent need. Immunotherapy has shown great potential in tumor treatment, especially in tumor vaccine development. The study objective was to evaluate the immune effects of cancer stem cells (CSCs) vaccines on OC. The CD44⁺CD117⁺CSCs were isolated from human OC HO8910 and SKOV3 cells using the magnetic cell sorting system; the cancer stem-like cells were selected from murine OC ID8 cell by no-serum formed sphere culture. The CSC vaccines were prepared by freezing and thawing these CSCs, which were then injected into mice followed by challenging the different OC cells. The in vivo antitumor efficacy of CSC immunization revealed the vaccines were capable of significantly provoking immune responses to autologous tumor antigens in vaccinated mice as the mice were found to have markedly inhibited tumor growth, prolonged survival, and decreased CSC counts in OC tissues when compared to mice without the CSC vaccination. The in vitro cytotoxicities of immunocytes toward SKOV3, HO8910 and ID8 cells indicated a significant killing efficacy compared with the controls. However, the antitumor efficacy was remarkably reduced whilst the mucin-1 expression in CSC vaccines was down-regulated by small interfering RNA. Overall, findings from this study provided the evidence that has deepened our understanding of CSC vaccine immunogenicity and anti-OC efficacy, particularly for the role of dominant antigen mucin-1. It is possible to turn the CSC vaccine into an immunotherapeutic approach against ovarian cancer.