Loss of Betaglycan Contributes to the Malignant Properties of Human Granulosa Tumor Cells

• Published in: Molecular endocrinology (Baltimore, Md.) Vol. 23; no. 4; pp. 539 - 548
• Main Authors: Bilandzic, Maree, Chu, Simon, Farnworth, Paul G, Harrison, Craig, Nicholls, Peter, Wang, Yao, Escalona, Ruth M, Fuller, Peter J, Findlay, Jock K, Stenvers, Kaye L
• Format: Journal Article
• Language: English
• Published: United States Endocrine Society 01.04.2009; Oxford University Press
• Subjects: Activins - genetics; Activins - metabolism; Cell Adhesion - physiology; Cell Line, Tumor; Female; Gene Silencing; Granulosa Cell Tumor - metabolism; Granulosa Cell Tumor - pathology; Humans; Inhibins - genetics; Inhibins - metabolism; Ligands; Neoplasm Invasiveness; Original Research; Ovarian Neoplasms - metabolism; Ovarian Neoplasms - pathology; Proteoglycans - genetics; Proteoglycans - metabolism; Receptors, Transforming Growth Factor beta - genetics; Receptors, Transforming Growth Factor beta - metabolism; Transforming Growth Factor beta - genetics; Transforming Growth Factor beta - metabolism
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/me.2008-0300

Betaglycan is a type III TGFβ receptor that modulates cellular sensitivity to inhibins and TGFβ. Previous studies have suggested that betaglycan acts as a tumor suppressor in certain human epithelial cancers. However, the roles of betaglycan in ovarian granulosa cell tumors (GCTs) are poorly understood. The objective of this study was to determine whether human GCTs exhibit betaglycan expression and, if so, what impact this receptor has on tumor biology. Real-time PCR was used to quantify betaglycan transcripts in human GCTs (n = 17) and normal premenopausal ovaries (n = 11). This analysis established that GCTs exhibited a significant 2-fold lower mean betaglycan mRNA level as compared with the normal ovary (P < 0.05). Similarly, two human GCT cell lines, KGN and COV434, exhibited low betaglycan expression and poor responsiveness to TGFβ and inhibin A in luciferase reporter assays, which was restored by stable transfection of wild-type betaglycan. Betaglycan significantly increased the adhesion of COV434 (P < 0.05) and KGN (P < 0.0001) cells, decreased cellular invasion through Matrigel, and inhibited wound healing. Expression of mutant forms of betaglycan that are defective in TGFβ and/or inhibin binding in each GCT cell line revealed that the inhibitory effects of betaglycan on wound healing were most strongly linked to the inhibin-binding region of betaglycan. Furthermore, knockdown of INHA mRNA expression abrogated the betaglycan-mediated inhibition of wound healing and invasion, whereas both INHA silencing and TGFβ neutralization abolished the betaglycan-mediated increase in adhesion to substrate. These data suggest that loss of betaglycan contributes to the pathogenesis of GCTs. Betaglycan expression on human granulosa tumor cells decreases cellular invasion and wound healing and increases substrate adhesion, actions most strongly linked to its inhibin-binding ability.