Either Kras activation or Pten loss similarly enhance the dominant-stable CTNNB1-induced genetic program to promote granulosa cell tumor development in the ovary and testis

Abstract

WNT, PI3K or RAS signaling pathways control specific stages of ovarian follicular development. To analyze the functional interactions of these pathways in granulosa cells during follicular development in vivo, we generated specific mutant mouse models. Stable activation of the WNT signaling effector beta-catenin (CTNNB1) in granulosa cells results in the formation of premalignant lesions that develop into granulosa cell tumors (GCTs) spontaneously later in life or following targeted deletion of the tumor suppressor gene Pten. Conversely, expression of oncogenic KRASG12D dramatically arrests proliferation, differentiation and apoptosis in granulosa cells, and consequently, small abnormal follicle-like structures devoid of oocytes accumulate in the ovary. Because of the potent anti-proliferative effects of KRASG12D in granulosa cells, we sought to determine if KRASG12D would block precancerous lesion and tumor formation in follicles of the CTNNB1 mutant mice. Unexpectedly, transgenic Ctnnb1;Kras mutant mice exhibited increased GC proliferation, decreased apoptosis and impaired differentiation and developed early-onset GCTs leading to premature death in a manner similar to the Ctnnb1;Pten mutant mice. Microarray and RT-PCR analyses revealed that gene regulatory processes induced by CTNNB1 were mostly enhanced by either KRAS activation or Pten loss in remarkably similar patterns and degree. The concomitant activation of CTNNB1 and KRAS in Sertoli cells also caused testicular granulosa cell tumors that showed gene expression patterns that partially overlapped those observed in GCTs of the ovary. Although the mutations analyzed herein have not yet been linked to adult GCTs in humans, 1) other components of these pathways may be altered or mutated, 2) these mutations may relate to juvenile GCTs or 3) they may occur in tumors of other tissues where CTNNB1 is mutated. Importantly, our results provide strong evidence that CTNNB1 is the driver in these contexts and that KRASG12D and Pten loss promote the program set in motion by the CTNNB1.

Proteomic Analysis of Exosomes from Mutant KRAS Colon Cancer Cells Identifies Intercellular Transfer of Mutant KRAS

“…Among these, EPHA2 and EPS8 levels positively correlate with mutant KRAS expression in cancer tissue and cells (59,60), and when KRAS is transfected into intestinal epithelial cells, enhanced CTNND1 phosphorylation is observed (61). These proteins might play an important role in imparting exosome-induced effects on recipient cells.…”

FOXL2: a central transcription factor of the ovary

“…Inactivation of Pten in mice where b-catenin is constitutively active also leads to a worsening of the tumour phenotype, suggesting that the PI3K/AKT pathway can be effectively mobilised in GCTs (Richards et al 2012). More surprisingly, deregulation of the ERK pathway in the same mice, through the use of a Kras mutant, also leads to a worsening of the phenotype, while the introduction of this mutation into WT mice leads to cell cycle arrest in GCs (Richards et al 2012). The MAPKs, particularly ERK, could thus play an important role in tumorigenesis of GCs.…”

“…Thus, deletion of the genes coding the oestrogen receptors Esr1 and/or Esr2 in Inha K/K mice leads to earlier and more aggressive tumour formation (Burns et al 2003). Inactivation of Pten in mice where b-catenin is constitutively active also leads to a worsening of the tumour phenotype, suggesting that the PI3K/AKT pathway can be effectively mobilised in GCTs (Richards et al 2012). More surprisingly, deregulation of the ERK pathway in the same mice, through the use of a Kras mutant, also leads to a worsening of the phenotype, while the introduction of this mutation into WT mice leads to cell cycle arrest in GCs (Richards et al 2012).…”

FOXO1/3 and PTEN Depletion in Granulosa Cells Promotes Ovarian Granulosa Cell Tumor Development

“…GCTs can also occur in the testis (9,10). In women GCTs have been subclassified as adult or juvenile based on the onset of tumor formation, tumor cell morphology and the expression of specific genes, most notably forkhead box (FOX)L2, globin transcription factor (GATA) 4, and inhibin beta B (INHBB) (6,11).…”