The role of glycoprotein-130 cytokines in female reproduction and reproductive cancer

Abstract

There are many similarities between trophoblast and cancer cells. Both share similar capabilities since they are highly proliferative, invasive and migratory. Cytokines regulate the physiological and temporal proliferation, invasion and migration of specialized trophoblast cells that largely comprise the placenta, which is required to sustain healthy pregnancy. Aberrant cytokine signalling however, can contribute to abnormal trophoblast function and placental development, leading to placental insufficiency and pregnancy disorders. Leukemia inhibitory factor (LIF) and interleukin (IL)11 share a common accessory signalling molecule, glycoprotein (gp) 130 and are both expressed in placental tissue. Important functional roles for these cytokines in embryo implantation and decidualization during the initiation of pregnancy have been well established. More recent studies demonstrate roles in human trophoblast function in vitro, however their precise functional role during placental development in vivo are yet to be determined. The endometrium is the inner lining of the uterus and the site of embryo implantation during the initiation of pregnancy. Conversely, the endometrium is also the most common site for the occurrence of uterine cancer, which is the most common gynecological malignancy. After menopause, the endometrium becomes atrophic and endometrial carcinomas most commonly arise when this quiescent state is altered by hormonal imbalances, molecular genetic alterations, or both. Alarmingly though, the burden of endometrial cancer is also rapidly increasing in women of reproductive age. IL11 has previously been linked to various epithelial cell malignancies and there is some in vitro evidence to suggest a functional role in endometrial cancer, although the mechanisms of this are not understood. In this thesis, I sought to determine the functional roles of LIF and IL11 in placental development and also the role of IL11 in endometrial tumour growth and metastasis in vivo in mice. To investigate the roles of endogenous LIF and IL11 in placental development in vivo, pregnant C56BL6/J mice were treated with one of two unique PEGylated antagonists that block LIF (PEGLA), or IL11 (PEGIL11A) signalling, or PEG alone as a vehicle control. To investigate the effect of elevated levels of IL11 on placentation and preeclampsia features, mice were administered with recombinant human IL11 or saline vehicle control. Treatments were administered intraperitoneally during the time of placental development at embryonic day (E)8-10, E10-13 or E10- 17 and mice sacrificed on final day of treatment. The number of viable implantation sites was recorded and placental morphology was assessed by immunohistochemistry and gene targets by PCR arrays. Systolic blood pressure and total urinary protein were measured in IL11 or saline treated mice pregnant and non-pregnant mice. To determine the role of IL11 signalling in endometrial tumour growth, female immune-compromised Balb/c athymic nude mice were used to form endometrial xenograft tumours, subcutaneously and orthotopically in the uterine lumen. Mice were administered with an IL11 receptor (R)α blocking antibody or IgG control antibody after tumour establishment. Tumour growth (volume mm3) was measured in mice with subcutaneous tumours. Intrauterine tumours were weighed (mg) at the study endpoint and the number of peritoneal metastatic lesions counted. Tumour morphology was assessed by immunohistochemistry and gene targets by PCR arrays. Temporally blocking LIF during placentation impaired trophoblast invasion and placental vascular development compared to PEG. PEGLA altered gene targets regulating placental angiogenesis and oxidative stress and increased trophoblast apoptosis at all time points. Ultimately, at late gestation, pregnancy viability was significantly compromised following LIF inhibition from E10-17. IL11 inhibition using PEGIL11A resulted in dysregulated placental trophoblast and vasculature structure, demonstrating that placental-derived IL11 is required for normal placentation. IL11 overexpression from E8-10/E10-13 resulted in impaired spiral artery remodeling. Mice treated with recombinant IL11 from E10-17 demonstrated the hallmark features of preeclampsia including elevated systolic blood pressure, proteinuria, altered placentas and significantly growth restricted fetal phenotype compared to controls. In mice with established tumours, IL11Rα antibody treatment significantly reduced subcutaneous and intrauterine endometrial tumour growth and peritoneal metastasis, compared to IgG control. The studies in this thesis are the first to demonstrate that LIF and IL11 are critical for trophoblast function, placentation and pregnancy viability in vivo in mice. Our data show alterations in the normal levels of IL11 and LIF leads to abnormal placentation and contributes to features of pregnancy disorders in an in vivo animal model. Meanwhile blocking IL11 signalling reduced endometrial tumour growth and dissemination in mice, highlighting the potential for therapeutically targeting IL11 in women with endometrial cancer.