Purpose of Study:
Several forms of cancer contain a misregulated Wnt/β-catenin signalling pathway. The authors of this paper set out to examine if this pathway is involved in granulosa cell tumorigenesis using a transgenic mouse model with a mutation in β-catenin in the granulosa cells.
Wnts = Large family of glycoprotein signalling molecules secreted in the body that interact with Frizzled (Fzd) receptors and are involved largely in embryonic development.
β-catenin = a protein involved in cell-cell adhesions and is a component of the Wnt signal pathway.
Pathway:
During Wnt signal transduction pathway β-catenin localizes in the cytoplasm of the cell in a large multiprotein complex (APC + Axin). Here, during rest β-catenin is consistently degraded preventing its accumulation. However during Wnt signalling β-catenin separates from its cytoplasmic complex and relocated in the nucleus affecting transcription activity.
Figure 1. Wnt/β-catenin Signaling Pathway
Results:
Misregulated Wnt/β-catenin signalling in ovarian GCT.
β-catenin expression and cellular localization was analyzed using immunohistochemistry in a human and equine GCT sample. Nuclear staining was observed in the GCT samples but not in the normal ovary samples representing the activation of the Wnt/β-catenin signalling pathway in granulosa cell tumors. 
Genetically engineered mice develop multiple follicle like ovarian lesions.
A transgenic mouse was created in which the recombined allele encodes a mutated β-catenin that lacks the ability to form in its cytoplasmic complex and under degradation and localized this to the ovary.
In figure 3:
Catnbflox(ex3)/+ (control)- No Transgene
Catnbflox(ex3)/+;Amhr2cre/+- Contain Transgene
The Catnbflox(ex3)/+;Amhr2cre/+ mice have multiple abnormal follicles, are cystic and possess very disorganized cellular arrangement that is not present in the control mice. This image also clearly illustrates the different ovarian lesion types that can be observed.
Characterization of ovarian lesions.
Catnbflox(ex3)/+ (control) and Catnbflox(ex3)/+;Amhr2cre/+ ovarian tissues were examined using immunohistochemistry for β-catenin expression. It was found that all cells in the ovarian lesions expressed β-catenin mainly localized in the nucleus. In the control mouse and the normal follicles of the transgene mouse β-catenin was found but was mainly localized to the cytoplasm. Through further immunohistochemical analysis it was discovered that the ovarian lesions present in the Catnbflox(ex3)/+;Amhr2cre/+ mice are vascularised in a way similar to the corpora lutea in the ovary but the granulosa cells in these lesions have a very slow proliferation rate and at not luteinized (Figure 4).
Subfertility of Catnbflox(ex3)/+;Amhr2cre mice.
6 week old Catnbflox(ex3)/+;Amhr2cre mice were tested for their relative fertility with the control mice buy placing them in the presence of and adult male mouse. It was found that the Catnbflox(ex3)/+;Amhr2cre mice produced fewer and smaller litters and the onset of pregnancy was delayed suggesting a delayed puberty or the ability to overcome the subfertility phenotype with age.
Personal Critique
The methodology and data analysis of this paper are presented in a very clear manner. The figures provided supply the reader with a clear visualization of the ovary subjects and a great comparison of their characteristics. Biomedical research makes great use of transgenic mice in which targeted gene changes are made to create a mouse model for a particular disease. Before the successes of this paper, there was a lack of transgenic mouse models for ovarian cancer, especially for the Granulosa Cell Tumour type. The authors of this paper have presented one of the first models for this disease type and have shown that there is a significant involvement of the misregulated Wnt/β-catenin signalling pathway in the development of GCTs. This paper alludes to further research of Granulosa Cell Tumours using their newly developed transgenic model in hope to reveal further information concerning the etiology of this disease. Overall I would recommend this paper as a great clear presentation of the important advancements and discoveries in the field of ovarian cancer research.
References:
Boerboom D, Paquet M, Hsieh M, Liu J, Jamin SP, Behringer RR, Sirois J, Taketo MM, Richards JS. Misregulated Wnt/beta-catenin signaling leads to ovarian granulosa cell tumor development. Cancer Res. 2005 15;65(20):9206-15
