Objective: Determine the effects of factors secreted by normal human ovarian stroma on the proliferation of benign and malignant ovarian epithelia, in vitro.
Methods: Primary cultures of normal human ovarian surface epithelium (HOSE), human ovarian stromal tissue (HOST), and epithelial ovarian carcinomas (CSOC) were established from surgical specimens and characterized immunohistochemically using anti-cytokeratin, vimentin, and Factor VIII antibodies. Stroma-conditioned media (SCM) were collected over 3 days from confluent HOST cultures. The SCM were dialyzed, lyophilized, resuspended, and added to HOSE, CSOC, SKOV-3, and Caov-3 ovarian cancer cell cultures and growth inhibitory effects were assayed by MTS and [3H]thymidine uptake.
Results: SCM inhibited the growth and DNA synthesis of normal HOSE cells and cancer cells by 79-99% in > 10-cell lines studied to date. The inhibitory effect was rapid in onset with 31-82% reduction in DNA synthesis at 1 hr and approximately 50% return of activity by 23 hr following a 1-hr SCM pulse treatment. The SCM inhibitory activity was not abolished by boiling or by absorption with heparin-agarose. Size exclusion filtration places the molecular weight of the inhibitory substance between 1 and 3 kDa. Neither trypsin nor proteinase K treatments altered the inhibitory activity of SCM, while a Bligh-Dyer organic extraction placed the activity in the aqueous phase.
Conclusion: A heat-stable, non-heparin-binding, low-molecular-weight, water-soluble substance secreted by normal ovarian stroma significantly inhibits HOSE and ovarian cancer cell proliferation. Derangements in normal ovarian stroma-epithelial interactions may contribute to growth dysregulation of the surface epithelia and result in ovarian carcinogenesis.