Aberrant expression of ovary determining gene FOXL2 in the testis and juvenile granulosa cell tumor in children. J Urol

Unité d'Endocrinologie-Gynécologie Pédiatrique, Service de Pédiatrie 1, Hôpital Arnaud-de-Villeneuve and Service d'Hormonologie du Développement et de Reproduction, Hôpital Lapeyronie, Centre Hospitalier Universitaire Montpellier, Montpellier, France.
The Journal of urology (Impact Factor: 3.75). 09/2008; 180(4 Suppl):1810-3. DOI: 10.1016/j.juro.2008.03.097
Source: PubMed

ABSTRACT FOXL2 is the earliest known marker of ovarian differentiation in mammals. It is involved in ovarian somatic cell differentiation and further follicle maintenance. FOXL2 is not implicated in determination of the male gonad and it is absent in the testis. We investigated whether the rare JGCTT (juvenile granulose cell tumor of the testis), named for its histological similarity to ovarian tumor, could be the first illustration of aberrant expression of this ovary determining gene in the human testis.
Between 1990 and 2004, 3 boys with JGCTT were reported from the TGM95 database of the French Society for Childhood Cancer and from 8 pediatric endocrinology centers. Orchiectomy was performed in these patients. Immunohistochemistry of FOXL2, and co-immunofluorescence of FOXL2 and SOX9 were performed on tumor sections.
Testicular tumor cells showed aberrant expression of FOXL2, which resembled normal ovarian granulosa cells. The localization of FOXL2 expression was nuclear without any cytoplasmic sequestration, suggesting that FOXL2 had biological activity. Conversely SOX9, which is present in the nucleus of normal testicular cells, was sequestered in the cytoplasm of granulosa tumor cells or markedly under expressed in the nuclei. In this case of residual SOX9 nuclear expression the expression of FOXL2 and SOX9 was mutually exclusive.
To our knowledge we report the first human model of aberrant intratesticular expression of an ovary determining gene along with the extinction of SOX9 and the transdifferentiation of a testicular cell into a granulosa tumor cell.

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    • "Whilst KGN is shown to have abundant FOXL2 expression, this gene is almost absent in COV434 [13], [21]. This finding correlates to observations made by Kalfa et al, who noted FOXL2 immunochemistry to be decreased or absent in juvenile-type GCTs [24], [25]. "
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    ABSTRACT: Despite their distinct biology, granulosa cell tumours (GCTs) are treated the same as other ovarian tumours. Intriguingly, a recurring somatic mutation in the transcription factor Forkhead Box L2 (FOXL2) 402C>G has been found in nearly all GCTs examined. This investigation aims to identify the pathogenicity of mutant FOXL2 by studying its altered transcriptional targets. The expression of mutant FOXL2 was reduced in the GCT cell line KGN, and wildtype and mutant FOXL2 were overexpressed in the GCT cell line COV434. Total RNA was hybridised to Affymetrix U133 Plus 2 microarrays. Comparisons were made between the transcriptomes of control cells and cells altered by FOXL2 knockdown and overexpression, to detect potential transcriptional targets of mutant FOXL2. The overexpression of wildtype and mutant FOXL2 in COV434, and the silencing of mutant FOXL2 expression in KGN, has shown that mutant FOXL2 is able to differentially regulate the expression of many genes, including two well known FOXL2 targets, StAR and CYP19A. We have shown that many of the genes regulated by mutant FOXL2 are clustered into functional annotations of cell death, proliferation, and tumourigenesis. Furthermore, TGF-β signalling was found to be enriched when using the gene annotation tools GATHER and GeneSetDB. This enrichment was still significant after performing a robust permutation analysis. Given that many of the transcriptional targets of mutant FOXL2 are known TGF-β signalling genes, we suggest that deregulation of this key antiproliferative pathway is one way mutant FOXL2 contributes to the pathogenesis of adult-type GCTs. We believe this pathway should be a target for future therapeutic interventions, if outcomes for women with GCTs are to improve.
    PLoS ONE 07/2012; 7(9):e46270. DOI:10.1371/journal.pone.0046270 · 3.23 Impact Factor
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    • "In support of this, the KGN cells had been generated from a 73 year old patient [27] and the COV434 cells were taken from a 27 year old [28], [29]. Significantly, the finding that COV434 cells lack FOXL2 together with reports by Kalfa and co-workers, that juvenile-type GCT have low or aberrant FOXL2 expression [38], [39] suggest that an alteration of FOXL2 function is a feature of both the adult and juvenile GCT subtypes. "
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    ABSTRACT: Granulosa cell tumors (GCT) of the ovary often express aromatase and synthesize estrogen, which in turn may influence their progression. Recently a specific point mutation (C134W) in the FOXL2 protein was identified in >94% of adult-type GCT and it is likely to contribute to their development. A number of genes are known to be regulated by FOXL2, including aromatase/CYP19A1, but it is unclear which are direct targets and whether the C134W mutation alters their regulation. Recently, it has been reported that FOXL2 forms a complex with steroidogenic factor 1 (SF-1) which is a known regulator of aromatase in granulosa cells. In this work, the human GCT-derived cell lines KGN and COV434 were heterozygous and wildtype for the FOXL2:C134W mutation, respectively. KGN had abundant FOXL2 mRNA expression but it was not expressed in COV434. Expression of exogenous FOXL2:C134W in COV434 cells induced higher expression of a luciferase reporter for the ovarian specific aromatase promoter, promoter II (PII) (-516bp) than expression of wildtype FOXL2, but did not alter induction of a similar reporter for the steroidogenic acute regulatory protein (StAR) promoter (-1300bp). Co-immunoprecipitation confirmed that FOXL2 bound SF-1 and that it also bound its homologue, liver receptor homologue 1 (LRH-1), however, the C134W mutation did not alter these interactions or induce a selective binding of the proteins. A highly conserved putative binding site for FOXL2 was identified in PII. FOXL2 was demonstrated to bind the site by electrophoretic mobility shift assays (EMSA) and site-directed mutagenesis of this element blocked its differential induction by wildtype FOXL2 and FOXL2:C134W. These findings suggest that aromatase is a direct target of FOXL2:C134W in adult-type GCT via a single distinctive and highly conserved binding site in PII and therefore provide insight into the pathogenic mechanism of this mutation.
    PLoS ONE 12/2010; 5(12):e14389. DOI:10.1371/journal.pone.0014389 · 3.23 Impact Factor
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    • "These results indicate that FOXL2 likely impacts not only embryonic ovarian formation but also specific basic metabolic aspects required for somatic cell proliferation and differentiation. Reduced levels of Foxl2 have also been linked to aggressive progression of ovarian GCTs (Kalfa et al. 2008), indicating that FOXL2 may regulate multiple effects in granulosa cells that are context and stage specific. Another striking, recently published, ovarian phenotype occurs in mice in which the Foxo3 gene has been disrupted (Castrillon et al. 2003). "
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    ABSTRACT: Infertility adversely affects many couples worldwide. Conversely, the exponential increase in world population threatens our planet and its resources. Therefore, a greater understanding of the fundamental cellular and molecular events that control the size of the primordial follicle pool and follicular development is of utmost importance to develop improved in vitro fertilization as well as to design novel approaches to regulate fertility. In this review we attempt to highlight some new advances in basic research of the mammalian ovary that have occurred in recent years focusing primarily on mouse models that have contributed to our understanding of ovarian follicle formation, development, and ovulation. We hope that these new insights into ovarian function will trigger more research and translation to clinically relevant problems.
    Handbook of experimental pharmacology 01/2010; 198(198):3-27. DOI:10.1007/978-3-642-02062-9_1
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