Gonadal tumorigenesis in transgenic mice bearing the mouse inhibin alpha-subunit promoter/simian virus T-antigen fusion gene: characterization of ovarian tumors and establishment of gonadotropin- responsive granulosa cell lines

Abstract

To establish in vivo gonadal tumor models and permanent lines of gonadal somatic cells we produced transgenic (TG) mice expressing the Simian virus (SV) 40 T-antigens (T-ag), driven by 6 or 2.1 kilobase fragments of the mouse inhibin alpha-subunit promoter. Hitherto, altogether 44 TG mice, one of which carried the shorter transgene, have produced gonadal tumors. Two founder females expressing the longer transgene, KK1 and KK3, and three established TG mouse lines were studied in detail. Penetrance of the phenotype in IT6-M and IT6-F mouse lines was 100% (tumors/TG: IT6-M 22/22, IT6-F 14/14). The T-ag mRNA was strongly expressed in the gonads, adrenal glands, pituitary, and brain. The KK-1 and KK-3 ovarian tumor cells immunostained with anti-SV40 large-T antibody. The KK-1 cells possessed high-affinity LH receptors [equilibrium association constant (Ka = 7.8 x 10(10) liters/mol] and responded to human CG by elevated cAMP and progesterone production. Also FSH slightly stimulated their cAMP and estradiol production (P < 0.01). These cells expressed cytochrome P450arom and inhibin alpha mRNA, but not cytochrome P450c17 alpha. In conclusion, the KK-1 cells are immortalized luteinizing granulosa cells expressing endogenous gonadotropin receptors, steroidogenic enzymes, and inhibin alpha. These cells will be useful in studies on the molecular aspects of granulosa cell function. The present study indicates that the 6-kilobase fragment of the inhibin alpha promoter described in this article contains the elements directing tissue-specific expression in vivo and is useful for targeted expression of other genes in the gonads.

GATA-4 Regulates Bcl-2 Expression in Ovarian Granulosa Cell Tumors

“…Three normal human ovaries, removed because of cervical cancer from women younger than 35 yr of age, were used as normal reference tissues. Mouse GCT samples originated from transgenic mice, expressing the SV40 T antigen driven by the inhibin-␣ promoter (27). Given that these mice spontaneously develop typical GCTs by 4 -5 months of age, samples from a 5-month-old mouse were used in this study.…”

Adrenocortical tumorigenesis, luteinizing hormone receptor and transcription factors GATA-4 and GATA-6

“…We have studied the molecular mechanisms of adrenal tumorigenesis extensively in the inh α/Tag TG mouse model, where the mice bearing the Simian Virus 40 T-antigen (Tag) under a 6-kb fragment of the murine inhibin α-subunit promoter (inhα), develop gonadal tumors with 100% penetrance by the age of 5-6 mo (Kananen et al 1995). When prepubertally gonadectomized, these mice develop adrenocortical tumors by the same age (Kananen et al 1996.…”

Murine homologues of the Drosophila gustavus gene are expressed in ovarian granulosa cells

“…To confirm these results, we also analysed SSB-1 expression in immortalized cell lines derived from granulosa cells (see Havelock et al (2004) for review). KK-1 and NT-1 cells were derived from granulosa cell tumours of transgenic mice expressing SV40 T-antigen under the control of the inhibin a-subunit promoter (Kananen et al 1995, Rilianawati et al 1999. DC3 cells were derived from rat granulosa cells transformed using SV40 in vitro (Fitz et al 1989).…”