Hormonal and Growth Regulation of Epithelial and Stromal Cells From the Normal and Malignant Endometrium by Pigment Epithelium-Derived Factor

Potential therapeutic role for pigment epithelium-derived factor in post-menopausal breast cancer bone metastasis

OBJECTIVES

This review discusses key oestrogens associated with the circulating pre- and post-menopausal milieu and how they may impact intratumoral oestrogen levels and breast cancer (BC) metastasis. It also identifies critical steps in BC metastasis to bone from the viewpoint of pigment epithelium-derived factor (PEDF) function, and discusses the role of several associated pro-metastatic biomarkers in BC bone metastasis.

KEY FINDINGS

PEDF is regulated by oestrogen in a number of oestrogen-sensitive tissues. Changes in circulating oestrogen levels associated with menopause may enhance the growth of BC bone metastases, leading to the establishment of a pre-metastatic niche. The establishment of such a pre-metastatic niche is driven by several key mediators, with pro-osteoclastic and pro-metastatic function which are upregulated by BC cells. These mediators appear to be regulated by oestrogen, as well as differentially affected by menopausal status. PEDF interacts with several pro-metastatic, pro-osteoclastic biomarkers, including C-X-C motif chemokine receptor 4 (CXCR4) and nuclear factor kappa B (NFκB) in BC bone metastasis.

CONCLUSION

Mediators such as CXCR4 and MT1-MMP underpin the ability of PEDF to function as an antimetastatic in other cancers such as osteosarcoma, highlighting the possibility that this serpin could be used as a therapeutic against BC metastasis in future.

Cancer-associated fibroblasts in gynecological malignancies: are they really allies of the enemy?

Molecular and cellular components of the tumor microenvironment are essential for cancer progression. The cellular element comprises cancer cells and heterogeneous populations of non-cancer cells that satisfy tumor needs. Immune, vascular, and mesenchymal cells provide the necessary factors to feed the tumor mass, promote its development, and favor the spread of cancer cells from the primary site to adjacent and distant anatomical sites. Cancer-associated fibroblasts (CAFs) are mesenchymal cells that promote carcinogenesis and progression of various malignant neoplasms. CAFs act through the secretion of metalloproteinases, growth factors, cytokines, mitochondrial DNA, and non-coding RNAs, among other molecules. Over the last few years, the evidence on the leading role of CAFs in gynecological cancers has notably increased, placing them as the cornerstone of neoplastic processes. In this review, the recently reported findings regarding the promoting role that CAFs play in gynecological cancers, their potential use as therapeutic targets, and the new evidence suggesting that they could act as tumor suppressors are analyzed and discussed.

Pigment epithelium-derived factor downregulation in oestrogen receptor positive breast cancer bone metastases is associated with menopause

Pigment epithelium-derived factor (PEDF) has a critical role in bone development and anti-tumour function in breast cancer (BC). As the expression and role of PEDF in BC bone metastases is unknown, we aimed to characterise PEDF in primary and metastatic BC. Subcellular PEDF localisation was semi-quantitatively analysed via immunohistochemistry in patient-matched, archived formalin-fixed paraffin-embedded primary BC and liver, lung, and decalcified bone metastases specimens. PEDF localisation was evaluated in 23 metastatic BC patients diagnosed with ER+, human epidermal growth factor receptor-2 (HER2) negative BC or TNBC. Cytoplasmic (p = 0.019) and membrane (p = 0.048) PEDF was lower in bone metastases compared to primary ER+/HER2- BC. In contrast, nuclear PEDF scores were higher in metastases compared to primary TNBC (p = 0.027), and increased membrane PEDF in metastatic tissue had improved disease-free interval (p = 0.016). Nuclear PEDF was decreased in bone metastases compared to primary ER+//HER2- BC in post-menopausal patients (p = 0.029). These novel findings indicate PEDF plays a role in clinical BC metastasis. Significantly lower PEDF levels in the post-menopausal compared to pre-menopausal setting suggests future PEDF research may have greater clinical importance in the post-menopausal ER+/HER2- BC population.

Pigment Epithelium-Derived Factor and Sex Hormone-Responsive Cancers

Oestrogens and androgens play important roles in normal and cancerous tissue and have been shown to negatively regulate pigment epithelium-derived factor (PEDF) expression in sex hormone-responsive tumours. PEDF suppresses tumour growth and its downregulation by oestrogen is implicated in tumorigenesis, metastasis, and progression. PEDF expression is reduced in cancerous tissue of the prostate, breast, ovary, and endometrium compared to their normal tissue counterparts, with a link between PEDF downregulation and sex hormone signalling observed in pre-clinical studies. PEDF reduces growth and metastasis of tumour cells by promoting apoptosis, inhibiting angiogenesis, increasing adhesion, and reducing migration. PEDF may also prevent treatment resistance in some cancers by downregulating oestrogen receptor signalling. By interacting with components of the tumour microenvironment, PEDF counteracts the proliferative and immunosuppressive effects of oestrogens, to ultimately reduce tumorigenesis and metastasis. In this review, we focus on sex hormone regulation of PEDF's anti-tumour action in sex hormone-responsive tumours.

Therapeutic Potential of Pigment Epithelium-derived Factor in Cancer

Pigment epithelium-derived factor (PEDF) is one of the serine protease inhibitors with multifunctional properties, which is produced by various types of organs and tissues. There is an accumulating body of evidence that PEDF plays an important role in the maintenance of tissue homeostasis. Indeed, PEDF not only works as an endogenous inhibitor of angiogenesis, but also suppresses oxidative stress, inflammatory and thrombotic reactions in cell culture systems, animal models, and humans. Furthermore, we, along with others, have found that PEDF inhibits proliferation of, and induces apoptotic cell death in, numerous kinds of tumors. In addition, circulating as well as tumor expression levels of PEDF have been inversely associated with tumor growth and metastasis. These observations suggest that supplementation of PEDF proteins and/or enhancement of endogenous PEDF expression could be a novel therapeutic strategy for the treatment of cancer. Therefore, in this paper, we review the effects of PEDF on diverse types of cancer, and discuss its therapeutic perspectives.

Pigment epithelium-derived factor in lipid metabolic disorders

Pigment epithelium-derived factor (PEDF) is a secreted glycoprotein that has anti-angiogenic, anti-proliferative, neurotrophic and immunomodulatory properties. PEDF has recently emerged as a critical metabolic regulatory protein since the discovery of its modulatory activities in the lipolytic pathway by binding to adipose triglyceride lipase (ATGL). Despite being beneficial in maintaining the homeostasis of hepatic lipid accumulation, PEDF has been uncovered an unfavorable role associated with insulin resistance. The molecular events that connect these two apparent distinct observations have been controversial and remained largely unknown. Therefore in this short review, we attempt to summarize the current findings of PEDF regarding its lipid metabolic functions and provide perspectives in identifying PEDF as a potential therapeutic target in lipid disorders.

Decreased PEDF Expression Promotes Adipogenic Differentiation through the Up-Regulation of CD36

Adipogenesis is a tightly regulated cellular process that involves the action of multiple signaling pathways. Characterization of regulators that are associated with adipose development is crucial to understanding the mechanisms underlying obesity and other metabolic disorders. Pigment epithelium-derived factor (PEDF) is a secreted glycoprotein that was first described as a neurotrophic factor. The role of PEDF in lipid metabolism was established when adipose triglyceride lipase (ATGL), a major triglyceride hydrolase, was characterized as its binding partner. In this study, we investigated the downstream effects of PEDF on adipogenic differentiation using rat adipose-derived stem cells (AdSCs) and the mouse pre-adipocyte cell line 3T3-L1. Knocking down PEDF in differentiating cells resulted in elevated levels of ATGL and CD36, as well as other adipogenic markers, with a concomitant increase in adipocyte number. CD36, a scavenger receptor for a variety of ligands, regulated proliferation and lipogenic gene expression during adipogenesis. The CD36 increase due to PEDF down-regulation might be a result of elevated PPARγ. We further demonstrated that PEDF expression was regulated by dexamethasone, a synthetic glucocorticoid that is widely used for adipogenesis at the transcriptional level. Taken together, our findings highlight that PEDF negatively regulates adipogenesis through the regulation of various signaling intermediates, and it may play a crucial role in lipid metabolic disorders.

Ulipristal Acetate Interferes With Actin Remodeling Induced by 17β-Estradiol and Progesterone in Human Endometrial Stromal Cells

Ulipristal acetate (UPA) is a selective progesterone receptor modulator (SPRM) used for emergency contraception and for the medical management of symptomatic uterine fibroids (UF). Treatment with UPA turns in amenorrhea and UF volume reduction. Treatment with UPA is associated with the frequent development of benign, transitory endometrial changes known as SPRM-associated endometrial changes (PAECs). Why PAECs develop and their biological or cellular basis is unknown. Sex steroids, including estrogen and progesterone, are established modulators of the actin cytoskeleton in various cells, including endometrial cells. This explains several morphological and functional changes in endometrial cells. We thus hypothesized that UPA may alter the appearance of the endometrium by interfering with the actions of 17β-estradiol (E2) or progesterone (P4) on actin dynamics. We isolated and cultured human endometrial stromal cells (ESC) from endometrial biopsies from healthy fertile women. Treatment with E2 or P4 stimulated visible actin rearrangements with actin remodeling toward the membrane. Activation through phosphorylation of the actin regulatory proteins, Moesin, and focal adhesion kinase (FAK), hacked actin remodeling induced by E2 and P4. Membrane re-localization of Paxillin and Vinculin were also induced by E2 and P4, showing the formation of focal adhesion complexes. All these E2 and P4 actions were inhibited by co-treatment with UPA, which was otherwise inactive if given alone. The cytoskeletal changes induced by E2 and P4 turned into increased motility of ESC, and UPA again blocked the actions E2 and P4. In conclusion, we find that UPA interferes with the cytoskeletal actions of E2 and P4 in ESC. This finding helps understanding the mode of actions of SPRMs in the endometrium and may be relevant for other potential clinical applications of UPA.