Ovarian carcinoma patients frequently develop malignant ascites containing single and aggregated tumor cells, or spheroids. Spheroids have been shown to be resistant to many therapies, but their contribution to ovarian cancer dissemination remains undetermined. We have previously shown that ascites spheroids adhere to extracellular matrix (ECM) proteins and live human mesothelial cells via β1 integrin subunits. Here, we assessed the ability of spheroids that were generated from the human ovarian carcinoma cell line NIH: OVCAR5 to disseminate and invade in vitro. Spheroids were seeded on ECM proteins for 24 h. While laminin and type IV collagen stimulated some cell migration, spheroids completely disaggregated on type I collagen substrates. A monoclonal antibody against the β1 integrin subunit significantly inhibited disaggregation on all proteins tested. To test their invasive ability, spheroids were added to monolayers of live human LP9 mesothelial cells. Within 24 h, the spheroids adhered and disaggregated on top of the monolayers, and within a week had established foci of invasion encompassing a 200-fold larger surface area. Addition of a monoclonal antibody against the β1 integrin subunit drastically reduced spheroid invasion into the mesothelial cell monolayers. GM 6001, a broad-scale matrix metalloproteinase inhibitor, also significantly blocked spheroid invasion into the mesothelial cell monolayers. ε-amino-N-caproic acid, a serine protease inhibitor, partially inhibited spheroid invasion. Based on their ability to attach to, disaggregate on, and invade into live human mesothelial cell monolayers, spheroids should thus be regarded as potential contributors to the dissemination of ovarian cancer.
Bibliographical noteFunding Information:
We thank Dr James McCarthy for providing fibronectin, Dr Leo Furcht for providing the mAb P5D2 against the β1 integrin subunit, and Dr Judah Folk-man for providing the NIH:OVCAR5 cell line. We thank Dr John Fassett for assistance and discussion regarding the type I collagen gels, and Dr George Iida and Dr Keith Skubitz for helpful discussions. This project was supported by grants from the Minnesota Ovarian Cancer Alliance, the Department of the Army (DA/DAMD 17-99-1-9564), the Minnesota Medical Foundation, and a Grant-in-Aid of Research from the Office of the Vice President for Research and the Dean of the Graduate School of the University of Minnesota. The content of the information presented in this manuscript does not necessarily reflect the position of the government.
- Cell adhesion molecules
- Extracellular matrix
- Ovarian carcinoma