17β-Estradiol sensitizes ovarian surface epithelium to transformation by suppressing Disabled-2 expression

The scaffold protein disabled 2 (DAB2) and its role in tumor development and progression

BACKGROUND

Disabled 2 (DAB2) is a multifunctional protein that has emerged as a critical component in the regulation of tumor growth. Its dysregulation is implicated in various types of cancer, underscoring its importance in understanding the molecular mechanisms underlying tumor development and progression. This review aims to unravel the intricate molecular mechanisms by which DAB2 exerts its tumor-suppressive functions within cancer signaling pathways.

METHODS AND RESULTS

We conducted a comprehensive review of the literature focusing on the structure, expression, physiological functions, and tumor-suppressive roles of DAB2. We provide an overview of the structure, expression, and physiological functions of DAB2. Evidence supporting DAB2's role as a tumor suppressor is explored, highlighting its ability to inhibit cell proliferation, induce apoptosis, and modulate key signaling pathways involved in tumor suppression. The interaction between DAB2 and key oncogenes is examined, elucidating the interplay between DAB2 and oncogenic signaling pathways. We discuss the molecular mechanisms underlying DAB2-mediated tumor suppression, including its involvement in DNA damage response and repair, regulation of cell cycle progression and senescence, and modulation of epithelial-mesenchymal transition (EMT). The review explores the regulatory networks involving DAB2, covering post-translational modifications, interactions with other tumor suppressors, and integration within complex signaling networks. We also highlight the prognostic significance of DAB2 and its role in pre-clinical studies of tumor suppression.

CONCLUSION

This review provides a comprehensive understanding of the molecular mechanisms by which DAB2 exerts its tumor-suppressive functions. It emphasizes the significance of DAB2 in cancer signaling pathways and its potential as a target for future therapeutic interventions.

AMPK-upregulated microRNA-708 plays as a suppressor of cellular senescence and aging via downregulating disabled-2 and mTORC1 activation

Senescence-associated microRNAs (SA-miRNAs) are important molecules for aging regulation. While many aging-promoting SA-miRNAs have been identified, confirmed aging-suppressive SA-miRNAs are rare, that impeded our full understanding on aging regulation. In this study, we verified that miR-708 expression is decreased in senescent cells and aged tissues and revealed that miR-708 overexpression can alleviate cellular senescence and aging performance. About the molecular cascade carrying the aging suppressive action of miR-708, we unraveled that miR-708 directly targets the 3'UTR of the disabled 2 (Dab2) gene and inhibits the expression of DAB2. Interestingly, miR-708-caused DAB2 downregulation blocks the aberrant mammalian target of rapamycin complex 1 (mTORC1) activation, a driving metabolic event for senescence progression, and restores the impaired autophagy, a downstream event of aberrant mTORC1 activation. We also found that AMP-activated protein kinase (AMPK) activation can upregulate miR-708 via the elevation of DICER expression, and miR-708 inhibitor is able to blunt the antiaging effect of AMPK. In summary, this study characterized miR-708 as an aging-suppressive SA-miRNA for the first time and uncovered a new signaling cascade, in which miR-708 links the DAB2/mTOR axis and AMPK/DICER axis together. These findings not only demonstrate the potential role of miR-708 in aging regulation, but also expand the signaling network connecting AMPK and mTORC1.

Disabled-2 (DAB2): A Key Regulator of Anti- and Pro-Tumorigenic Pathways

Disabled-2 (DAB2), a key adaptor protein in clathrin mediated endocytosis, is implicated in the regulation of key signalling pathways involved in homeostasis, cell positioning and epithelial to mesenchymal transition (EMT). It was initially identified as a tumour suppressor implicated in the initiation of ovarian cancer, but was subsequently linked to many other cancer types. DAB2 contains key functional domains which allow it to negatively regulate key signalling pathways including the mitogen activated protein kinase (MAPK), wingless/integrated (Wnt) and transforming growth factor beta (TGFβ) pathways. Loss of DAB2 is primarily associated with activation of these pathways and tumour progression, however this review also explores studies which demonstrate the complex nature of DAB2 function with pro-tumorigenic effects. A recent strong interest in microRNAs (miRNA) in cancer has identified DAB2 as a common target. This has reignited an interest in DAB2 research in cancer. Transcriptomics of tumour associated macrophages (TAMs) has also identified a pro-metastatic role of DAB2 in the tumour microenvironment. This review will cover the broad depth literature on the tumour suppressor role of DAB2, highlighting its complex relationships with different pathways. Furthermore, it will explore recent findings which suggest DAB2 has a more complex role in cancer than initially thought.

Microscopic Evaluation of Ovarian Surface Epithelium Following Treatment with Conjugated Estrogens in a Mouse Model

BACKGROUND

This study was designed to evaluate the effect of different concentrations of conjugated equine estrogens (CEE) on the ovarian epithelium of female CD1 mice.

METHODS

Twenty-four female mice at 7 months with irregular estrus cycles were randomly divided into four groups of 6 mice each. Group one was considered as a control group and received a daily dose of 0.5ml of propylene glycol, for three weeks, while those in the treatment groups received a daily dose of 14μg/kg, 28μg/kg and 56μg/kg conjugated equine estrogens, respectively.

RESULTS

The results from this study showed a strong correlation between elevated concentrations of CEE and histological changes in ovarian surface epithelium (OSE). They also showed that administration of high-dose estrogen created the conditions for excessive proliferation of OSE which may progress into the development of cysts in the ovaries.

CONCLUSION

This study concluded that high concentrations of CEE may increase the chances of developing epithelial ovarian cancer.

Effect of Interaction between 17β-Estradiol, 2-Methoxyestradiol and 16α-Hydroxyestrone with Chromium (VI) on Ovary Cancer Line SKOV-3: Preliminary Study

Ovarian cancer is the leading cause of death from gynecologic malignancies. Some estrogens, as well as xenoestrogens, such as chromium (VI) (Cr(VI)), are indicated as important pathogenic agents. The objective of this study was to evaluate the role of estradiol and some its metabolites upon exposure to the metalloestrogen Cr(VI) in an in vitro model. The changes in cell viability of malignant ovarian cancer cells (SKOV-3 resistant to cisplatin) exposed to 17β-estradiol (E2) and its two metabolites, 2-methoxyestradiol (2-MeOE2) and 16α-hydroxyestrone (16α-OHE1), upon exposure to potassium chromate (VI) and its interactions were examined. The single and mixed models of action, during short and long times of incubation with estrogens, were applied. The different effects (synergism and antagonism) of estrogens on cell viability in the presence of Cr(VI) was observed. E2 and 16α-OHE1 caused a synergistic effect after exposure to Cr(VI). 2-MeOE2 showed an antagonistic effect on Cr(VI). The examined estrogens could be ranked according to the most protective effect or least toxicity in the order: 2-MeOE2 > E2 > 16α-OHE1. Early pre-incubation (24 h or 7 days) of cells with estrogens caused mostly an antagonistic effect-protective against the toxic action of Cr(VI). The beneficial action of estrogens on the toxic effect of Cr(VI), in the context of the risk of ovarian cancer, seems to be important and further studies are needed.

COX2 is induced in the ovarian epithelium during ovulatory wound repair and promotes cell survival†

The ovarian surface epithelium (OSE) is a monolayer of cells surrounding the ovary that is ruptured during ovulation. After ovulation, the wound is repaired, however, this process is poorly understood. In epithelial tissues, wound repair is mediated by an epithelial-to-mesenchymal transition (EMT). Transforming Growth Factor Beta-1 (TGFβ1) is a cytokine commonly known to induce an EMT and is present throughout the ovarian microenvironment. We, therefore, hypothesized that TGFβ1 induces an EMT in OSE cells and activates signaling pathways important for wound repair. Treating primary cultures of mouse OSE cells with TGFβ1 induced an EMT mediated by TGFβRI signaling. The transcription factor Snail was the only EMT-associated transcription factor increased by TGFβ1 and, when overexpressed, was shown to increase OSE cell migration. A polymerase chain reaction array of TGFβ signaling targets determined Cyclooxygenase-2 (Cox2) to be most highly induced by TGFβ1. Constitutive Cox2 expression modestly increased migration and robustly enhanced cell survival, under stress conditions similar to those observed during wound repair. The increase in Snail and Cox2 expression with TGFβ1 was reproduced in human OSE cultures, suggesting these responses are conserved between mouse and human. Finally, the induction of Cox2 expression in OSE cells during ovulatory wound repair was shown in vivo, suggesting TGFβ1 increases Cox2 to promote wound repair by enhancing cell survival. These data support that TGFβ1 promotes ovulatory wound repair by induction of an EMT and activation of a COX2-mediated pro-survival pathway. Understanding ovulatory wound repair may give insight into why ovulation is the primary non-hereditary risk factor for ovarian cancer.

Non-canonical WNT5a regulates Epithelial-to-Mesenchymal Transition in the mouse ovarian surface epithelium

The ovarian surface epithelium (OSE) is a monolayer that covers the ovarian surface and is involved in ovulation by rupturing and enabling release of a mature oocyte and by repairing the wound after ovulation. Epithelial-to-mesenchymal transition (EMT) is a mechanism that may promote wound healing after ovulation. While this process is poorly understood in the OSE, in other tissues wound repair is known to be under the control of the local microenvironment and different growth factors such as the WNT signaling pathway. Among WNT family members, WNT4 and WNT5a are expressed in the OSE and are critical for the ovulatory process. The objective of this study was to determine the potential roles of WNT4 and WNT5a in regulating the OSE layer. Using primary cultures of mouse OSE cells, we found WNT5a, but not WNT4, promotes EMT through a non-canonical Ca2+-dependent pathway, up-regulating the expression of Vimentin and CD44, enhancing cell migration, and inhibiting the CTNNB1 pathway and proliferation. We conclude that WNT5a is a stimulator of the EMT in OSE cells, and acts by suppressing canonical WNT signaling activity and inducing the non-canonical Ca2+ pathway.

Single-cell RNA-sequencing reveals transcriptional dynamics of estrogen-induced dysplasia in the ovarian surface epithelium

Estrogen therapy increases the risk of ovarian cancer and exogenous estradiol accelerates the onset of ovarian cancer in mouse models. Both in vivo and in vitro, ovarian surface epithelial (OSE) cells exposed to estradiol develop a subpopulation that loses cell polarity, contact inhibition, and forms multi-layered foci of dysplastic cells with increased susceptibility to transformation. Here, we use single-cell RNA-sequencing to characterize this dysplastic subpopulation and identify the transcriptional dynamics involved in its emergence. Estradiol-treated cells were characterized by up-regulation of genes associated with proliferation, metabolism, and survival pathways. Pseudotemporal ordering revealed that OSE cells occupy a largely linear phenotypic spectrum that, in estradiol-treated cells, diverges towards cell state consistent with the dysplastic population. This divergence is characterized by the activation of various cancer-associated pathways including an increase in Greb1 which was validated in fallopian tube epithelium and human ovarian cancers. Taken together, this work reveals possible mechanisms by which estradiol increases epithelial cell susceptibility to tumour initiation.