Research article

Spontaneous transformation of human granulosa cell tumours into an aggressive phenotype: a metastasis model cell line

Misa Imai^1,2 , Miho Muraki¹ , Kiyoshi Takamatsu³ , Hidekazu Saito¹ , Motoharu Seiki² and Yuji Takahashi¹

¹  Division of Reproductive Medicine, Department of Perinatal Medicine and Maternal Care, National Center for Child Health and Development, Tokyo 157-8535, Japan

²  Division of Cancer Cell Research, Institute of Medical Science, the University of Tokyo, Tokyo 108-8639, Japan

³  Department of Obstetrics and Gynecology, Tokyo Dental College Ichikawa General Hospital, Chiba 272-8513, Japan

author email corresponding author email

BMC Cancer 2008, 8:319doi:10.1186/1471-2407-8-319

Published:	4 November 2008

Abstract

Background

Granulosa cell tumours (GCTs) are frequently seen in menopausal women and are relatively indolent. Although the physiological properties of normal granulosa cells have been studied extensively, little is known about the molecular mechanism of GCT progression. Here, we characterise the unique behavioural properties of a granulosa tumour cell line, KGN cells, for the molecular analysis of GCT progression.

Methods

Population doubling was carried out to examine the proliferation capacity of KGN cells. Moreover, the invasive capacity of these cells was determined using the in vitro invasion assay. The expression level of tumour markers in KGN cells at different passages was then determined by Western blot analysis. Finally, the growth and metastasis of KGN cells injected subcutaneously (s.c.) into nude mice was observed 3 months after injection.

Results

During in vitro culture, the advanced passage KGN cells grew 2-fold faster than the early passage cells, as determined by the population doubling assay. Moreover, we found that the advanced passage cells were 2-fold more invasive than the early passage cells. The expression pattern of tumour markers, such as p53, osteopontin, BAX and BAG-1, supported the notion that with passage, KGN cells became more aggressive. Strikingly, KGN cells at both early and advanced passages metastasized to the bowel when injected s.c. into nude mice. In addition, more tumour nodules were formed when the advanced passage cells were implanted.

Conclusion

KGN cells cultured in vitro acquire an aggressive phenotype, which was confirmed by the analysis of cellular activities and the expression of biomarkers. Interestingly, KGN cells injected s.c. are metastatic with nodule formation occurring mostly in the bowel. Thus, this cell line is a good model for analysing GCT progression and the mechanism of metastasis in vivo.