Progesterone receptors induce FOXO1-dependent senescence in ovarian cancer cells

FoxO1 inhibition promotes differentiation of human embryonic stem cells into insulin producing cells

Insulin-producing cells (IPCs) derived from human embryonic stem cells (hESCs) hold great potential for cell transplantation therapy in diabetes. Tremendous progress has been made in inducing differentiation of hESCs into IPCs in vitro, of which definitive endoderm (DE) protocol mimicking foetal pancreatic development has been widely used. However, immaturity of the obtained IPCs limits their further applications in treating diabetes. Forkhead box O1 (FoxO1) is involved in the differentiation and functional maintenance of murine pancreatic β cells, but its role in human β cell differentiation is under elucidation. Here, we showed that although FoxO1 expression level remained consistent, cytoplasmic phosphorylated FoxO1 protein level increased during IPC differentiation of hESCs induced by DE protocol. Lentiviral silencing of FoxO1 in pancreatic progenitors upregulated the levels of pancreatic islet differentiation-related genes and improved glucose-stimulated insulin secretion response in their progeny IPCs, whereas overexpression of FoxO1 showed the opposite effects. Notably, treatment with the FoxO1 inhibitor AS1842856 displayed similar effects with FoxO1 knockdown in pancreatic progenitors. These effects were closely associated with the mutually exclusive nucleocytoplasmic shuttling of FoxO1 and Pdx1 in the AS1842856-treated pancreatic progenitors. Our data demonstrated a promising effect of FoxO1 inhibition by the small molecule on gene expression profile during the differentiation, and in turn, on determining IPC maturation via modulating subcellular location of FoxO1 and Pdx1. Therefore, we identify a novel role of FoxO1 inhibition in promoting IPC differentiation of hESCs, which may provide clues for induction of mature β cells from hESCs and clinical applications in regenerative medicine.

Progesterone Prevents High-Grade Serous Ovarian Cancer by Inducing Necroptosis of p53-Defective Fallopian Tube Epithelial Cells

High-grade serous ovarian carcinoma (HGSOC) originates mainly from the fallopian tube (FT) epithelium and always carries early TP53 mutations. We previously reported that tumors initiate in the FT fimbria epithelium because of apoptotic failure and the expansion of cells with DNA double-strand breaks (DSB) caused by bathing of the FT epithelial cells in reactive oxygen species (ROSs) and hemoglobin-rich follicular fluid (FF) after ovulation. Because ovulation is frequent and HGSOC is rare, we hypothesized that luteal-phase progesterone (P4) could eliminate p53-defective FT cells. Here we show that P4, via P4 receptors (PRs), induces necroptosis in Trp53^-/- mouse oviduct epithelium and in immortalized human p53-defective fimbrial epithelium through the TNF-α/RIPK1/RIPK3/MLKL pathway. Necroptosis occurs specifically at diestrus, recovers at the proestrus phase of the estrus cycle, and can be augmented with P4 supplementation. These results reveal the mechanism of the well-known ability of progesterone to prevent ovarian cancer.

Progesterone improves neurocognitive outcomes following therapeutic cranial irradiation in mice

Despite improved therapeutic methods, CNS toxicity resulting from cancer treatment remains a major cause of post-treatment morbidity. More than half of adult patients with cranial irradiation for brain cancer develop neurobehavioral/cognitive deficits that severely impact quality of life. We examined the neuroprotective effects of the neurosteroid progesterone (PROG) against ionizing radiation (IR)-induced neurobehavioral/cognitive deficits in mice. Male C57/BL mice were exposed to one of two fractionated dose regimens of IR (3Gy×3 or 3Gy×5). PROG (16mg/kg; 0.16mg/g) was given as a pre-, concurrent or post-IR treatment for 14days. Mice were tested for short- and long-term effects of IR and PROG on neurobehavioral/cognitive function on days 10 and 30 after IR treatment. We evaluated both hippocampus-dependent and -independent memory functions. Locomotor activity, elevated plus maze, novel object recognition and Morris water maze tests revealed behavioral deficits following IR. PROG treatment produced improvement in behavioral performance at both time points in the mice given IR. Western blot analysis of hippocampal and cortical tissue showed that IR at both doses induced astrocytic activation (glial fibrillary acidic protein), reactive macrophages/microglia (CD68) and apoptosis (cleaved caspase-3) and PROG treatment inhibited these markers of brain injury. There was no significant difference in the degree of deficit in any test between the two dose regimens of IR at either time point. These findings could be important in the context of patients with brain tumors who may undergo radiotherapy and eventually develop cognitive deficits.

Parity History Determines a Systemic Inflammatory Response to Spread of Ovarian Cancer in Naturally Aged Mice

Aging intersects with reproductive senescence in women by promoting a systemic low-grade chronic inflammation that predisposes women to several diseases including ovarian cancer (OC). OC risk at menopause is significantly modified by parity records during prior fertile life. To date, the combined effects of age and parity on the systemic inflammation markers that are particularly relevant to OC initiation and progression at menopause remain largely unknown. Herein, we profiled a panel of circulating cytokines in multiparous versus virgin C57BL/6 female mice at peri-estropausal age and investigated how cytokine levels were modulated by intraperitoneal tumor induction in a syngeneic immunocompetent OC mouse model. Serum FSH, LH and TSH levels increased with age in both groups while prolactin (PRL) was lower in multiparous respect to virgin mice, a finding previously observed in parous women. Serum CCL2, IL-10, IL-5, IL-4, TNF-α, IL1-β and IL-12p70 levels increased with age irrespective of parity status, but were specifically reduced following OC tumor induction only in multiparous mice. Animals developed hemorrhagic ascites and tumor implants in the omental fat band and other intraperitoneal organs by 12 weeks after induction, with multiparous mice showing a significantly extended survival. We conclude that previous parity history counteracts aging-associated systemic inflammation possibly by reducing the immunosuppression that typically allows tumor spread. Results suggest a partial impairment of the M2 shift in tumor-associated macrophages as well as decreased stimulation of regulatory B-cells in aged mice. This long term, tumor-concurrent effect of parity on inflammation markers at menopause would be a contributing factor leading to decreased OC risk.

Characterizing the "POAGome": A bioinformatics-driven approach to primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a genetically, physiologically, and phenotypically complex neurodegenerative disorder. This study addressed the expanding collection of genes associated with POAG, referred to as the "POAGome." We used bioinformatics tools to perform an extensive, systematic literature search and compiled 542 genes with confirmed associations with POAG and its related phenotypes (normal tension glaucoma, ocular hypertension, juvenile open-angle glaucoma, and primary congenital glaucoma). The genes were classified according to their associated ocular tissues and phenotypes, and functional annotation and pathway analyses were subsequently performed. Our study reveals that no single molecular pathway can encompass the pathophysiology of POAG. The analyses suggested that inflammation and senescence may play pivotal roles in both the development and perpetuation of the retinal ganglion cell degeneration seen in POAG. The TGF-β signaling pathway was repeatedly implicated in our analyses, suggesting that it may be an important contributor to the manifestation of POAG in the anterior and posterior segments of the globe. We propose a molecular model of POAG revolving around TGF-β signaling, which incorporates the roles of inflammation and senescence in this disease. Finally, we highlight emerging molecular therapies that show promise for treating POAG.

The role of sex hormones and steroid receptors on female reproductive cancers

Sex steroids have been widely described to be associated with a number of human diseases, including hormone-dependent tumors. Several studies have been concerned about the factors regulating the availability of sex steroids and its importance in the pathophysiological aspects of the reproductive cancers in women. In premenopausal women, large fluctuations in the concentration of circulating estradiol (E2) and progesterone (P4) orchestrate many events across the menstrual cycle. After menopause, the levels of circulating E2 and P4 decline but remain at high concentration in the peripheral tissues. Notably, there is a strong relationship between circulating sex hormones and female reproductive cancers (e.g. ovarian, breast, and endometrial cancers). These hormones activate a number of specific signaling pathways after binding either to estrogen receptors (ERs), especially ERα, ERα36, and ERβ or progesterone receptors (PRs). Importantly, the course of the disease will depend on particular transactivation pathway. Identifying ER- or PR-positive tumors will benefit patients in terms of proper endocrine therapy. Based on hormonal responsiveness, effective prevention methods for ovarian, breast, and endometrial cancers represent a special opportunity for women at risk of malignancies. Hormone replacement therapy (HRT) might significantly increase the risk of these cancer types, and endocrine treatments targeting ER signaling may be helpful against E2-dependent tumors. This review will present the role of sex steroids and their receptors associated with the risk of developing female reproductive cancers, with emphasis on E2 levels in pre and postmenopausal women. In addition, new therapeutic strategies for improving the survival rate outcomes in women will be addressed.

IGF-1 Receptor Modulates FoxO1-Mediated Tamoxifen Response in Breast Cancer Cells

Tamoxifen is a common adjuvant treatment for estrogen receptor (ER)α-positive patients with breast cancer; however, acquired resistance abrogates the efficacy of this therapeutic approach. We recently demonstrated that G protein-coupled estrogen receptor 1 (GPER1) mediates tamoxifen action in breast cancer cells by inducing insulin-like growth factor-binding protein-1 (IGFBP-1) to inhibit IGF-1-dependent signaling. To determine whether dysregulation of IGFBP-1 induction is associated with tamoxifen resistance, IGFBP-1 transcription was measured in tamoxifen-resistant MCF-7 cells (TamR) after tamoxifen (Tam) treatment. IGFBP-1 transcription was not stimulated in tamoxifen-treated TamR cells whereas decreased expression of FoxO1, a known modulator of IGFBP-1, was observed. Exogenous expression of FoxO1 rescued the ability of tamoxifen to induce IGFBP-1 transcription in TamR cells. As decreased IGF-1R expression is observed in tamoxifen-resistant cells, the requirement for IGF-1R expression on tamoxifen-stimulated IGFBP-1 transcription was investigated. In TamR and SK-BR-3 cells, both characterized by low IGF-1R levels, exogenous IGF-1R expression increased FoxO1 levels and IGFBP-1 expression, whereas IGF-1R knockdown in MCF-7 cells decreased tamoxifen-stimulated IGFBP-1 transcription. Interestingly, both 17β-estradiol (E2)-stimulated ERα phosphorylation and progesterone receptor (PR) expression were altered in TamR. PR is a transcription factor known to modulate FoxO1 transcription. In addition, IGF-1R knockdown decreased FoxO1 protein levels in MCF-7 cells. Furthermore, IGF-1R or FoxO1 knockdown inhibited the ability of tamoxifen to induce IGFBP-1 transcription and tamoxifen sensitivity in MCF-7 cells. These data provide a molecular mechanistic connection between IGF-1R expression and the FoxO1-mediated mechanism of tamoxifen action in breast cancer cells.Implications: Loss of IGF-1R expression is associated with decreased tamoxifen efficacy in patients with breast cancer and the development of tamoxifen resistance. This contribution identifies potential molecular mechanisms of altered tamoxifen sensitivity in breast cancer cells resulting from decreased IGF-1R expression. Mol Cancer Res; 15(4); 489-97. ©2017 AACR.

Active Estrogen Receptor-alpha Signaling in Ovarian Cancer Models and Clinical Specimens

Purpose: High-grade serous ovarian cancer (HGSOC) is an aggressive disease with few available targeted therapies. Despite high expression of estrogen receptor-alpha (ERα) in approximately 80% of HGSOC and some small but promising clinical trials of endocrine therapy, ERα has been understudied as a target in this disease. We sought to identify hormone-responsive, ERα-dependent HGSOC.Experimental Design: We characterized endocrine response in HGSOC cells across culture conditions [ two-dimensional (2D), three-dimensional (3D), forced suspension] and in patient-derived xenograft (PDX) explants, assessing proliferation and gene expression. Estrogen-regulated transcriptome data were overlapped with public datasets to develop a comprehensive panel of ERα target genes. Expression of this panel and ERα H-score were assessed in HGSOC samples from patients who received endocrine therapy. Time on endocrine therapy was used as a surrogate for clinical response.Results: Proliferation is ERα-regulated in HGSOC cells in vitro and in vivo, and is partly dependent on 3D context. Transcriptomic studies identified genes shared by cell lines and PDX explants as ERα targets. The selective ERα downregulator (SERD) fulvestrant is more effective than tamoxifen in blocking ERα action. ERα H-score is predictive of efficacy of endocrine therapy, and this prediction is further improved by inclusion of target gene expression, particularly IGFBP3Conclusions: Laboratory models corroborate intertumor heterogeneity of endocrine response in HGSOC but identify features associated with functional ERα and endocrine responsiveness. Assessing ERα function (e.g., IGFBP3 expression) in conjunction with H-score may help select patients who would benefit from endocrine therapy. Preclinical data suggest that SERDs might be more effective than tamoxifen. Clin Cancer Res; 23(14); 3802-12. ©2017 AACR.

Impact of levonorgestrel-releasing intrauterine system use on the cancer risk of the ovary and fallopian tube

BACKGROUND

Levonorgestrel-releasing intrauterine system (LNG-IUS) is used for contraception and heavy menstrual bleeding. A long-term hormone therapy can modify the risk of gynecologic cancers. Little is known about the impact of LNG-IUS use on the risk for invasive and borderline ovarian tumor subtypes or for primary fallopian tube carcinoma. We examined the associations of LNG-IUS use with these tumors.

MATERIAL AND METHODS

We identified from the national Medical Reimbursement Registry of Finland the women aged 30-49 years who had used LNG-IUS for menorrhagia in 1994-2007, and from the Finnish Cancer Registry ovarian cancers and primary fallopian tube carcinomas diagnosed before the age of 55 and by the end of 2013.

RESULTS

A total of 77 invasive ovarian cancers and seven primary fallopian tube carcinoma cases were diagnosed in a cohort of 93 843 LNG-IUS users during the follow-up of 1 083 126 women-years. The LNG-IUS users had decreased risk for both invasive ovarian cancer [standardized incidence ratio (SIR) 0.59, 95% confidence interval (CI) 0.47-0.73] and for borderline ovarian tumors (SIR 0.76, 95% CI 0.57-0.99) as compared to the background population. The risk of primary fallopian tube carcinoma was not increased (SIR 1.22, 95% CI 0.49-2.50). Decreased risks for mucinous (SIR 0.49, 95% CI 0.24-0.87), endometrioid (SIR 0.55, 95% CI 0.28-0.98), and serous ovarian carcinomas (SIR 0.75, 95% CI 0.55-0.99) were seen in LNG-IUS users.

CONCLUSIONS

LNG-IUS use associated with decreased risk for both invasive and borderline ovarian tumors. The incidence of primary fallopian tube carcinoma did not significantly differ between LNG-IUS users and the background population.

Progesterone induces progesterone receptor gene (PGR) expression via rapid activation of protein kinase pathways required for cooperative estrogen receptor alpha (ER) and progesterone receptor (PR) genomic action at ER/PR target genes

Progesterone Receptors (PRs) are critical effectors of estrogen receptor (ER) signaling required for mammary gland development and reproductive proficiency. In breast and reproductive tract malignancies, PR expression is a clinical prognostic marker of ER action. While estrogens primarily regulate PR expression, other factors likely contribute to a dynamic range of receptor expression across diverse tissues. In this study, we identified estrogen-independent but progestin (R5020)-dependent regulation of ER target genes including PGR in ER+/PR+ cancer cell lines. R5020 (10nM-10μM range) induced dose-dependent PR mRNA and protein expression in the absence of estrogen but required both PR and ERα. Antagonists of either PR (RU486, onapristone) or ERα (ICI 182,780) attenuated R5020 induction of TFF1, CTSD, and PGR. Chromatin immunoprecipitation (ChIP) assays performed on ER+/PR+ cells demonstrated that both ERα and PR were recruited to the same ERE/Sp1 site-containing region of the PGR proximal promoter in response to high dose progestin (10μM). Recruitment of ERα and PR to chromatin and subsequent PR mRNA induction were dependent upon rapid activation of MAPK/ERK and AKT; inhibition of these kinase pathways via U0126 or LY294002 blocked these events. Overall, we have identified a novel mechanism of ERα activation initiated by rapid PR-dependent kinase pathway activation and associated with phosphorylation of ERα Ser118 for estrogen-independent but progestin-dependent ER/PR cross talk. These studies may provide insight into mechanisms of persistent ER-target gene expression during periods of hormone (i.e. estrogen) ablation and suggest caution following prolonged treatment with aromatase or CYP17 inhibitors (i.e. contexts when progesterone levels may be abnormally elevated).

Treating gynecologic malignancies with selective estrogen receptor downregulators (SERDs): promise and challenges

Endometrial and ovarian cancers are estrogen-dependent gynecologic malignancies. Although many are estrogen receptor (ER) positive, treatment with the selective estrogen receptor modulator (SERM) tamoxifen, a tissue selective partial-agonist, has demonstrated only modest clinical benefit. Selective estrogen receptor downregulators (SERDs) are pure ER antagonists showing a benefit for advanced ER positive breast cancer, which has bolstered their potential use for ER positive gynecologic malignancies. We summarize these preclinical and clinical data, suggesting that a subpopulation of patients with endometrial or ovarian cancer exists in which treatment with SERDs results in improved outcome. However, the full potential of SERDs for a gynecologic malignancies will be realized only when the appropriate predictive biomarkers are identified. Additionally, a further understanding ER signaling in the context of ovarian and endometrial tissues that appear to involve c-Src and other kinase pathways is needed to successfully address the emergence of resistance with rationally designed combination therapies.

The role of reproductive hormones in epithelial ovarian carcinogenesis

Epithelial ovarian cancer comprises ∼85% of all ovarian cancer cases. Despite acceptance regarding the influence of reproductive hormones on ovarian cancer risk and considerable advances in the understanding of epithelial ovarian carcinogenesis on a molecular level, complete understanding of the biologic processes underlying malignant transformation of ovarian surface epithelium is lacking. Various hypotheses have been proposed over the past several decades to explain the etiology of the disease. The role of reproductive hormones in epithelial ovarian carcinogenesis remains a key topic of research. Primary questions in the field of ovarian cancer biology center on its developmental cell of origin, the positive and negative effects of each class of hormones on ovarian cancer initiation and progression, and the role of the immune system in the ovarian cancer microenvironment. The development of the female reproductive tract is dictated by the hormonal milieu during embryogenesis. Intensive research efforts have revealed that ovarian cancer is a heterogenous disease that may develop from multiple extra-ovarian tissues, including both Müllerian (fallopian tubes, endometrium) and non-Müllerian structures (gastrointestinal tissue), contributing to its heterogeneity and distinct histologic subtypes. The mechanism underlying ovarian localization, however, remains unclear. Here, we discuss the role of reproductive hormones in influencing the immune system and tipping the balance against or in favor of developing ovarian cancer. We comment on animal models that are critical for experimentally validating existing hypotheses in key areas of endocrine research and useful for preclinical drug development. Finally, we address emerging therapeutic trends directed against ovarian cancer.

Active FOXO1 Is a Key Determinant of Isoform-Specific Progesterone Receptor Transactivation and Senescence Programming

Progesterone promotes differentiation coupled to proliferation and prosurvival in the breast, but inhibits estrogen-driven growth in the reproductive tract and ovaries. Herein, it is demonstrated, using progesterone receptor (PR) isoform-specific ovarian cancer model systems, that PR-A and PR-B promote distinct gene expression profiles that differ from PR-driven genes in breast cancer cells. In ovarian cancer models, PR-A primarily regulates genes independently of progestin, while PR-B is the dominant ligand-dependent isoform. Notably, FOXO1 and the PR/FOXO1 target gene p21 (CDKN1A) are repressed by PR-A, but induced by PR-B. In the presence of progestin, PR-B, but not PR-A, robustly induced cellular senescence via FOXO1-dependent induction of p21 and p15 (CDKN2B). Chromatin immunoprecipitation (ChIP) assays performed on PR isoform-specific cells demonstrated that while each isoform is recruited to the same PRE-containing region of the p21 promoter in response to progestin, only PR-B elicits active chromatin marks. Overexpression of constitutively active FOXO1 in PR-A-expressing cells conferred robust ligand-dependent upregulation of the PR-B target genes GZMA, IGFBP1, and p21, and induced cellular senescence. In the presence of endogenous active FOXO1, PR-A was phosphorylated on Ser294 and transactivated PR-B at PR-B target genes; these events were blocked by the FOXO1 inhibitor (AS1842856). PR isoform-specific regulation of the FOXO1/p21 axis recapitulated in human primary ovarian tumor explants treated with progestin; loss of progestin sensitivity correlated with high AKT activity.

IMPLICATIONS

This study indicates FOXO1 as a critical component for progesterone signaling to promote cellular senescence and reveals a novel mechanism for transcription factor control of hormone sensitivity.

Targeting FoxO1 with AS1842856 suppresses adipogenesis

Hyperplasia (i.e., increased adipogenesis) contributes to excess adiposity, the hallmark of obesity that can trigger metabolic complications. As FoxO1 has been implicated in adipogenic regulation, we investigated the kinetics of FoxO1 activation during adipocyte differentiation, and tested the effects of FoxO1 antagonist (AS1842856) on adipogenesis. We found for the first time that the kinetics of FoxO1 activation follows a series of sigmoid curves, and reveals the phases relevant to clonal expansion, cell cycle arrest, and the regulation of PPARγ, adiponectin, and mitochondrial proteins (complexes I and III). In addition, multiple activation-inactivation transitions exist in the stage of terminal differentiation. Importantly, persistent inhibition of FoxO1 with AS1842856 almost completely suppressed adipocyte differentiation, while selective inhibition in specific stages had differential effects on adipogenesis. Our data present a new view of FoxO1 in adipogenic regulation, and suggest AS1842856 can be an anti-obesity agent that warrants further investigation.

Progesterone action in breast, uterine, and ovarian cancers

Progesterone and progesterone receptors (PRs) are essential for the development and cyclical regulation of hormone-responsive tissues including the breast and reproductive tract. Altered functions of PR isoforms contribute to the pathogenesis of tumors that arise in these tissues. In the breast, progesterone acts in concert with estrogen to promote proliferative and pro-survival gene programs. In sharp contrast, progesterone inhibits estrogen-driven growth in the uterus and protects the ovary from neoplastic transformation. Progesterone-dependent actions and associated biology in diverse tissues and tumors are mediated by two PR isoforms, PR-A and PR-B. These isoforms are subject to altered transcriptional activity or expression levels, differential crosstalk with growth factor signaling pathways, and distinct post-translational modifications and cofactor-binding partners. Herein, we summarize and discuss the recent literature focused on progesterone and PR isoform-specific actions in breast, uterine, and ovarian cancers. Understanding the complexity of context-dependent PR actions in these tissues is critical to developing new models that will allow us to advance our knowledge base with the goal of revealing novel and efficacious therapeutic regimens for these hormone-responsive diseases.

Deletion of PDK1 causes cardiac sodium current reduction in mice

Background

The AGC protein kinase family regulates multiple cellular functions. 3-phosphoinositide-dependent protein kinase-1 (PDK1) is involved in the pathogenesis of arrhythmia, and its downstream factor, Forkhead box O1 (Foxo1), negatively regulates the expression of the cardiac sodium channel, Nav1.5. Mice are known to die suddenly after PDK1 deletion within 11 weeks, but the underlying electrophysiological bases are unclear. Thus, the aim of this study was to investigate the potential mechanisms between PDK1 signaling pathway and cardiac sodium current.

Methods and Results

Using patch clamp and western blotting techniques, we investigated the role of the PDK1-Foxo1 pathway in PDK1 knockout mice and cultured cardiomyocytes. We found that PDK1 knockout mice undergo slower heart rate, prolonged QRS and QTc intervals and abnormal conduction within the first few weeks of birth. Furthermore, the peak sodium current is decreased by 33% in cells lacking PDK1. The phosphorylation of Akt (308T) and Foxo1 (24T) and the expression of Nav1.5 in the myocardium of PDK1-knockout mice are decreased, while the nuclear localization of Foxo1 is increased. The role of the PDK1-Foxo1 pathway in regulating Nav1.5 levels and sodium current density was verified using selective PDK1, Akt and Foxo1 inhibitors and isolated neonatal rat cardiomyocytes.

Conclusion

These results indicate that PDK1 participates in the dysregulation of electrophysiological basis by regulating the PDK1-Foxo1 pathway, which in turn regulates the expression of Nav1.5 and cardiac sodium channel function.

Influence of AKT on progesterone action in endometrial diseases

Progesterone plays an essential role in the maintenance of the endometrium; it prepares the endometrium for pregnancy, promotes decidualization, and inhibits estrogen-dependent proliferation. Progesterone function is often dysregulated in endometrial disease states. In addition, the PI3K/AKT signaling pathway is often overactive in endometrial pathologies and promotes the survival and proliferation of the diseased cells. Understanding how AKT influences progesterone action is critical in improving hormone-based therapies in endometrial pathologies. Here, we summarize recent studies investigating the crosstalk between the AKT pathway and progesterone receptor function in endometriosis and endometrial cancer.

RC-6 ribonuclease induces caspase activation, cellular senescence and neuron-like morphology in NT2 embryonal carcinoma cells

Frog ribonucleases have been demonstrated to have anticancer activities. However, whether RC-6 ribonuclease exerts anticancer activity on human embryonal carcinoma cells remains unclear. In the present study, RC-6 induced cytotoxicity in NT2 cells (a human embryonal carcinoma cell line) and our studies showed that RC-6 can exert anticancer effects and induce caspase-9 and -3 activities. Moreover, to date, there is no evidence that frog ribonuclease-induced cytotoxicity effects are related to cellular senescence. Therefore, our studies showed that RC-6 can increase p16 and p21 protein levels and induce cellular senescence in NT2 cells. Notably, similar to retinoic acid-differentiated NT2 cells, neuron-like morphology was found on some remaining live cells after RC-6 treatment. In conclusion, our study is the first to demonstrate that RC-6 can induce cytotoxic effects, caspase-9/-3 activities, cellular senescence and neuron-like morphology in NT2 cells.

Early pregnancy sex steroids and maternal risk of epithelial ovarian cancer

Well-established associations between reproductive characteristics and epithelial ovarian cancer (EOC) support an involvement of sex steroid hormones in the etiology of EOC. Limited previous studies have evaluated circulating androgens and the risk of EOC, and estrogens and progesterone have been investigated in only one of the previous studies. Furthermore, there is little data on potential heterogeneity in the association between circulating hormones and EOC by histological subgroup. Therefore, we conducted a nested case-control study within the Finnish Maternity Cohort and the Northern Sweden Maternity Cohort to investigate the associations between circulating pre-diagnostic sex steroid concentrations and the histological subtypes of EOC. We identified 1052 EOC cases among cohort members diagnosed after recruitment (1975-2008) and before March 2011. Up to three controls were individually matched to each case (n=2694). Testosterone, androstenedione, 17-hydroxyprogesterone (17-OHP), progesterone, estradiol (E2), and sex hormone-binding globulin levels were measured in serum samples collected during the last pregnancy before EOC diagnosis. We used conditional logistic regression to estimate odds ratios (ORs) and 95% CIs. Associations between hormones and EOC differed with respect to tumor histology and invasiveness. Sex steroid concentrations were not associated with invasive serous tumors; however, doubling of testosterone and 17-OHP concentration was associated with approximately 40% increased risk of borderline serous tumors. A doubling of androgen concentrations was associated with a 50% increased risk of mucinous tumors. The risk of endometrioid tumors increased with higher E2 concentrations (OR: 1.89 (1.20-2.98)). This large prospective study in pregnant women supports a role of sex steroid hormones in the etiology of EOC arising in the ovaries.

Post-transcriptional repression of FOXO1 by QKI results in low levels of FOXO1 expression in breast cancer cells

The RNA-binding protein Quaking (QKI) is known to be essential for embryonic development and postnatal myelination. Forkhead box O1 (FOXO1) is a critical tumor suppressor for cell proliferation control. Dysregulation of FOXO1 expression has been observed in a variety of cancers. In the present study, we demonstrated that QKI decreased FOXO1 mRNA expression at the post-transcriptional level. QKI was able to bind the 3'UTR of FOXO1 mRNA directly and decreased its mRNA stability. To determine whether QKI-mediated post-transcriptional repression of FOXO1 indeed plays a role in cancer cells, we first detected both QKI and FOXO1 expression in four breast cancer cell lines. FOXO1 expression was extremely low in these cell lines, whereas QKI expression was relative high. Knockdown of QKI significantly restored FOXO1 expression. ATRA, an inducer of apoptosis or differentiation, dramatically enhanced FOXO1 expression while it repressed QKI expression. Importantly, the ATRA-induced increase in FOXO1 expression was dependent on QKI-mediated post-transcriptional regulation. Consistently, 5-FU, a widely used chemotherapeutic agent, increased FOXO1 expression via inhibition of QKI. In summary, our study provides initial evidence demonstrating that QKI-mediated repression of FOXO1 may be one of the factors contributing to the oncogenesis and progression of breast carcinoma, which suggests that targeting QKI may serve as a novel strategy to sensitize breast cancers to chemotherapy.