A preliminary study on a new model system to evaluate tumour-detection and tumour-purging protocols in ovarian cortex tissue intended for fertility preservation.

STUDY QUESTION: Is it possible to create a model system that mimics ovarian metastatic disease in order to devise new strategies to detect cancer cells and prevent cancer cell transmission via ovarian tissue autotransplantation in cancer survivors? SUMMARY ANSWER: Injection of bovine or human ovarian cortex fragments with cells from different cancer types led to the formation of proliferating tumour masses and newly formed small metastatic lesions. WHAT IS KNOWN ALREADY: Autotransplantation of ovarian tissue comes with the major concern of cancer cells possibly being present in the tissue. A model system to develop strategies aimed at enhancing the safety of ovarian tissue autotransplantation is currently lacking. STUDY DESIGN, SIZE, DURATION: The ability of injected human leukaemia, lymphoma, Ewing's sarcoma or breast cancer cells to proliferate and form tumour-like structures in bovine and human ovarian cortex tissue in vitro was assessed. The injected cells were from human cancer cell lines. After 4 days of culture, some tissue fragments were harvested for standard histological staining and immunohistochemical staining of tumour cell specific antigens and the Ki67 proliferation marker, while the remaining fragments were incubated for an additional 6 days (bovine tissue) or 3 days (human tissue) before analysis. PARTICIPANTS/MATERIALS, SETTING,
METHODS: Experiments were performed with ovarian tissue from women after prophylactic salpingo-oophorectomy. Bovine ovarian tissue was obtained at an abattoir. Glucose uptake during in vitro culture was monitored to quantify the viability of tissue. Tumour formation was assessed at Day 4 and Day 10 in bovine ovarian tissue and at Day 4 and Day 7 in human ovarian tissue, using histology and immunohistochemistry. MAIN RESULTS AND THE ROLE OF CHANCE: We found that bovine and human ovarian cortex tissue could be cultured for up to 10 and 7 days, respectively, without any loss of viability. Our preliminary results show that all cell lines tested were capable of forming proliferating tumours in ovarian cortex tissue in vitro. Lymphoma and breast cancer cells produced small metastases near the original lesions. LIMITATIONS, REASONS FOR CAUTION: The tumour model presented was based on the growth of human cancer cell lines in ovarian cortex tissue. It is unknown whether these cells behave differently from malignant cells derived from primary tumours. In addition, the human ovarian tissue was derived from women over 39 years of age, which is obviously considerably older than patients opting for ovarian tissue cryopreservation. WIDER IMPLICATIONS OF THE
FINDINGS: Our model system will facilitate the development of procedures to detect cancer cells in, or purge cancer cells from, human ovarian tissue. STUDY FUNDING/COMPETING INTERESTS: Unconditional funding was received from the Radboud Institute for Health Sciences, KiKa Foundation and Merck Serono. There are no conflicts of interest to declare.