Marie-Noëlle Laguë

Synergistic effects of Pten loss and WNT/CTNNB1 signaling pathway activation in ovarian granulosa cell tumor development and progression

The mechanisms of granulosa cell tumor (GCT) development may involve the dysregulation of signaling pathways downstream of follicle-stimulating hormone, including the phosphoinosite-3 kinase (PI3K)/AKT pathway. To test this hypothesis, a genetically engineered mouse model was created to derepress the PI3K/AKT pathway in granulosa cells by conditional targeting of the PI3K antagonist gene Pten (Pten(flox/flox);Amhr2(cre/+)). The majority of Pten(flox/flox);Amhr2(cre/+) mice featured no ovarian anomalies, but occasionally ( approximately 7%) developed aggressive, anaplastic GCT with pulmonary metastases. The expression of the PI3K/AKT downstream effector FOXO1 was abrogated in Pten(flox/flox);Amhr2(cre/+) GCT, indicating a mechanism by which GCT cells may increase proliferation and evade apoptosis. To relate these findings to spontaneously occurring GCT, analyses of PTEN and phospho-AKT expression were performed on human and equine tumors. Although PTEN loss was not detected, many GCT (2/5 human, 7/17 equine) featured abnormal nuclear or perinuclear localization of phospho-AKT, suggestive of altered PI3K/AKT activity. As inappropriate activation of WNT/CTNNB1 signaling causes late-onset GCT development and cross talk between the PI3K/AKT and WNT/CTNNB1 pathways has been reported, we tested whether these pathways could synergize in GCT. Activation of both the PI3K/AKT and WNT/CTNNB1 pathways in the granulosa cells of a mouse model (Pten(flox/flox);Ctnnb1(flox(ex3)/+);Amhr2(cre/+)) resulted in the development of GCT similar to those observed in Pten(flox/flox);Amhr2(cre/+) mice, but with 100% penetrance, perinatal onset, extremely rapid growth and the ability to spread by seeding into the abdominal cavity. These data indicate a synergistic effect of dysregulated PI3K/AKT and WNT/CTNNB1 signaling in the development and progression of GCT and provide the first animal models for metastatic GCT.

Dysregulation of WNT/CTNNB1 and PI3K/AKT signaling in testicular stromal cells causes granulosa cell tumor of the testis

Synergistic effects of dysregulation of the WNT/CTNNB1 and phosphatidylinositol 3-kinase (PI3K)/AKT pathways are thought to be important for the development and progression of many forms of cancer, including the granulosa cell tumor of the ovary. Sustained WNT/CTNNB1 signaling in Sertoli cells causes testicular degeneration and the formation of foci of poorly differentiated stromal cells in the seminiferous tubules in mice. To test if concomitant dysregulation of the WNT/CTNNB1 and PI3K/AKT pathways could synergize to cause testicular cancer, Pten(tm1Hwu/tm1Hwu);Ctnnb1(tm1Mmt/+);Amhr2(tm3(cre)Bhr/+) mice that express a dominant, stable CTNNB1 mutant and lack the expression of phosphatase and tensin homolog (PTEN) in their Sertoli cells were generated. These mice developed aggressive testicular cancer with 100% penetrance by 5 weeks of age, and 44% of animals developed pulmonary metastases by 4 months, whereas Pten(tm1Hwu/tm1Hwu);Amhr2(tm3(cre)Bhr/+) controls were phenotypically normal. Surprisingly, the tumors could not be classified as Sertoli cell tumors, but rather bore histologic and ultrastructural characteristics of granulosa cell tumors of the testis (GCTT). Pten(tm1Hwu/tm1Hwu);Ctnnb1(tm1Mmt/+);Amhr2(tm3(cre)Bhr/+) testicular tumors did not express CYP17, CYP19, germ cell nuclear antigen, estrogen receptor 1 or progesterone receptor, but expressed the early granulosa cell markers WNT4 and FOXL2, confirming the diagnosis of GCTT. Immunohistochemical analyses of Pten(tm1Hwu/tm1Hwu);Ctnnb1(tm1Mmt/+);Amhr2(tm3(cre)Bhr/+) GCTT demonstrated a tumor marker profile similar to that reported in human GCTT. Immunoblotting analyses revealed high levels of phosphorylation of AKT and the PI3K/AKT signaling effector FOXO1A in Pten(tm1Hwu/tm1Hwu);Ctnnb1(tm1Mmt/+);Amhr2(tm3(cre)Bhr/+) GCTT, suggesting the involvement of FOXO1A in the mechanism of GCTT development. Together, these data provide the first insights into the molecular etiology of GCTT and the first animal model for the study of GCTT biology.

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.

WNT, RAS or phosphoinositide 3-kinase 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 β-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 whether 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 reverse transcription–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, they may be related to juvenile GCTs or to tumors in other tissues where CTNNB1 is mutated. Importantly, the 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.

Pharmacological targeting of mammalian target of rapamycin inhibits ovarian granulosa cell tumor growth

Few targeted therapies have been developed for ovarian granulosa cell tumor (GCT), even though it represents 5% of all malignant ovarian tumors in women. As misregulation of PI3K/AKT signaling has been implicated in GCT development, we hypothesized that the AKT signaling effector mammalian target of rapamycin (mTOR) may play a role in the pathogenesis of GCT and could represent a therapeutic target. Analyses of human GCT samples showed an increase in protein levels of mTOR and its downstream effectors RPS6KB1, RPS6, eIF4B and PPARG relative to normal granulosa cells, suggestive of an increase in mTOR pathway activity and increased translational activity and/or protein stability. We next sought to evaluate mTOR as a GCT therapeutic target using the Pten (tm1Hwu/tmiHwu);Ctnnb1 (tm1Mmt/+);Amhr2 (tm3(cre)Bhr/+) (PCA) mouse model, in which mTOR, RPS6KB1, eIF4B and PPARG are upregulated in tumor cells in a manner similar to human GCT. Treatment of PCA mice with the mTOR-specific inhibitor everolimus reduced tumor growth rate (1.5-fold; P < 0.05) and also reduced total tumor burden (4.7-fold; P < 0.05) and increased survival rate (78 versus 44% in the vehicle group) in a PCA surgical model of GCT peritoneal carcinomatosis. Everolimus decreased tumor cell proliferation and tumor cell volume relative to controls (P < 0.05), whereas apoptosis was unaffected. Phosphorylation of RPS6KB1 and RPS6 were decreased (P < 0.05) by everolimus, but RPS6KB1, RPS6, eIF4B and PPARG expressions were not affected. These results suggest that mTOR is a valid and clinically useful pharmacological target for the treatment of GCT, although its inhibition does not reverse all consequences of aberrant PI3K/AKT signaling in the PCA model.

Decidual PTEN expression is required for trophoblast invasion in the mouse

Trophoblast invasion likely depends on complex cross talk between the fetal and maternal tissues and may involve the modulation of phosphatidylinositol 3-kinase (PI3K)/AKT signaling activity in maternal decidual cells. In this report, we studied implantation in Pten(tm1Hwu/tm1Hwu);Amhr2(tm3(cre)Bhr/+) mice, which lack the PI3K signaling antagonist gene Pten in myometrial and stromal/decidual cells. Primiparous Pten(tm1Hwu/tm1Hwu);Amhr2(tm3(cre)Bhr/+) mice were found to be subfertile because of increased fetal mortality at e11.5. Histopathological analyses revealed a failure of decidual regression in these mice, accompanied by reduced or absent invasion of fetal trophoblast glycogen cells and giant cells, abnormal development of the placental labyrinth, and frequent apparent intrauterine fetal growth restriction. Unexpectedly, the loss of phosphate and tensin homolog deleted on chromosome 10 (PTEN) expression in Pten(tm1Hwu/tm1Hwu);Amhr2(tm3(cre)Bhr/+) decidual cells was not accompanied by a detectable increase in AKT phosphorylation or altered expression or activation of PI3K/AKT downstream effectors such as mammalian target of rapamycin or glycogen synthase kinase-3β. Terminal deoxynucleotidyl transferase-mediated nick end labeling and bromodeoxyuridine incorporation analyses attributed to the lack of decidual regression mainly to decreased apoptosis in Pten(tm1Hwu/tm1Hwu);Amhr2(tm3(cre)Bhr/+) decidual cells, rather than to increased proliferation. Remodeling of the maternal vasculature was delayed in Pten(tm1Hwu/tm1Hwu);Amhr2(tm3(cre)Bhr/+) uteri at e11.5, as evidenced by persistence of vascular smooth muscle and decreased infiltration of uterine natural killer cells. In addition, thickening of the myometrium and disorganization of the muscle fibers were observed before and throughout gestation. Almost all Pten(tm1Hwu/tm1Hwu);Amhr2(tm3(cre)Bhr/+) mice failed to carry a second litter to term, apparently attributable to endometrial hyperplasia and uterine infections. Together, these data demonstrate novel roles of PTEN in the mammalian uterus and its requirement for proper trophoblast invasion and decidual regression.

Proteomic Profiling of a Mouse Model for Ovarian Granulosa Cell Tumor Identifies VCP as a Highly Sensitive Serum Tumor Marker in Several Human Cancers

The initial aim of this study was to identify novel serum diagnostic markers for the human ovarian granulosa cell tumor (GCT), a tumor that represents up to 5% of all ovarian cancers. To circumvent the paucity of human tissues available for analyses, we used the Ctnnb1 tm1Mmt/+;Pten tm1Hwu/tmiHwu;Amhr2 tm3(cre)Bhr/+ transgenic mouse model, which features the constitutive activation of CTNNB1 signaling combined with the loss of Pten in granulosa cells and develops GCTs that mimic aggressive forms of the human disease. Proteomic profiling by mass spectrometry showed that vinculin, enolase 1, several heat shock proteins, and valosin containing protein (VCP) were more abundantly secreted by cultured mouse GCT cells compared to primary cultured GC. Among these proteins, only VCP was present in significantly increased levels in the preoperative serum of GCT cancer patients compared to normal subjects. To determine the specificity of VCP, serum levels were also measured in ovarian carcinoma, non-Hodgkins lymphoma and breast, colon, pancreatic, lung, and prostate cancer patients. Increased serum VCP levels were observed in the majority of cancer cases, with the exception of patients with lung or prostate cancer. Moreover, serum VCP levels were increased in some GCT, ovarian carcinoma, breast cancer, and colon cancer patients who did not otherwise display increased levels of widely used serum tumor markers for their cancer type (e.g. inhibin A, inhibin B, CA125, CEA, or CA15.3). These results demonstrate the potential use of VCP as highly sensitive serum marker for GCT as well as several other human cancers.

Atypical caudal duplication with phenotypic sex reversal in a dog

A male German Shepherd Dog mix was presented for chronic non–weight-bearing lameness of the left hind limb. At clinical examination, the dog’s left hind limb had severe joint contractures, with the presence of what appeared to be a second paw. The dog also had 2 sets of external genitalia of opposite phenotypic sex; a complete male reproductive tract with a left retained testicle and a right descended testicle, as well as rudimentary female external genitalia including a hypoplastic vulva with a blind-end vagina and a hypertrophied clitoris. The female genitalia were located on the proximal posterior third of the deformed limb. Following amputation of the hind limb, gross pathologic analysis revealed a duplication of the fibula, tarsal, and metatarsal bones, digits, and appendices. The supernumerary structures and female genitalia were concluded to represent a parasitic twin. As conjoined or parasitic twinning of non-identical twins is thought to be impossible, the presence of genitalia of opposite phenotypic sex appeared paradoxical. Polymerase chain reaction analyses were therefore performed to determine the genotypic sex of both animals, which revealed the presence of the Y chromosome in all tissues, including the female genitalia. The non-masculinization of the external genitalia in the parasitic twin was presumed to be the result of an embryonic developmental defect. On this basis, a diagnosis of atypical caudal duplication (parasitic twinning) with phenotypic sex reversal was made.

Abstract 3193: Valosin containing protein (VCP) is a potential novel serum marker for ovarian cancer

The measurement of various serum markers (estradiol, inhibin, MIS) is often performed as an ancillary diagnostic technique for ovarian granulosa cell tumor (GCT), and is widely used for postoperative surveillance for disease recurrence. However, both the sensitivity and specificity of these markers has been repeatedly questioned, and a truly reliable serum marker for GCT has yet to be identified. We have recently developed the Ctnnb1tm1Mmt/+;Ptentm1Hwu/tm1Hwu;Amhr2tm3(cre)Bhr/+ (CPA) transgenic mouse model, which features genetic modifications that mimic pathologically relevant genetic lesions and signaling processes that occur in GCT in women. CPA mice develop anaplastic, highly aggressive GCTs that can spread both by forming distant metastases and by seeding into the peritoneal cavity, which are the main modes of GCT dissemination in women. Due to the biological similarities between GCT in women and in CPA mice, we hypothesized that the CPA model could be used in a translational approach to identify novel serum markers for GCT. To test this, granulosa cells from control mice and GCT cells from CPA mice were placed in culture, and differential secretion or shedding of proteins into the culture supernatant was analyzed by SDSPAGE and silver staining. Proteins bands present in the experimental samples but absent (or present at much lower levels) in control media were isolated from the gels and identified by tryptic digestion followed by LC/MS/MS analyses. By this method, VCL, VCP, HSPA4, HSP90A, HSP70, SPARC, WIF1, CTSB, FAM3C, TIMP2, CFL2 and B2M were found to be selectively secreted/shed by CPA GCT cells. An in vivo validation step was then performed to determined if these proteins were overexpressed in the serum of CPA mice relative to controls. Western blotting showed that CPA mice had elevated (P Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3193. doi:10.1158/1538-7445.AM2011-3193