Non-covalent inhibitors of thioredoxin glutathione reductase with schistosomicidal activity in vivo.

Only praziquantel is available for treating schistosomiasis, a disease affecting more than 200 million people. Praziquantel-resistant worms have been selected for in the lab and low cure rates from mass drug administration programs suggest that resistance is evolving in the field. Thioredoxin glutathione reductase (TGR) is essential for schistosome survival and a validated drug target. TGR inhibitors identified to date are irreversible and/or covalent inhibitors with unacceptable off-target effects. In this work, we identify noncovalent TGR inhibitors with efficacy against schistosome infections in mice, meeting the criteria for lead progression indicated by WHO. Comparisons with previous in vivo studies with praziquantel suggests that these inhibitors outperform the drug of choice for schistosomiasis against juvenile worms.

Exploration of Verticillins in High-Grade Serous Ovarian Cancer and Evaluation of Multiple Formulations in Preclinical In Vitro and In Vivo Models.

Verticillins are epipolythiodioxopiperazine alkaloids isolated from a fungus with nanomolar anti-tumor activity in high-grade serous ovarian cancer (HGSOC). HGSOC is the fifth leading cause of death in women, and natural products continue to be an inspiration for new drug entities to help tackle chemoresistance. Verticillin D was recently found in a new fungal strain and compared to verticillin A. Both compounds exhibited nanomolar cytotoxic activity against OVCAR4 and OVCAR8 HGSOC cell lines, significantly reduced 2D foci and 3D spheroids, and induced apoptosis. In addition, verticillin A and verticillin D reduced tumor burden in vivo using OVCAR8 xenografts in the peritoneal space as a model. Unfortunately, mice treated with verticillin D displayed signs of liver toxicity. Tolerability studies to optimize verticillin A formulation for in vivo delivery were performed and compared to a semi-synthetic succinate version of verticillin A to monitor bioavailability in athymic nude females. Formulation of verticillins achieved tolerable drug delivery. Thus, formulation studies are effective at improving tolerability and demonstrating efficacy for verticillins.

Breast cancer prevention with liquiritigenin from licorice through the inhibition of aromatase and protein biosynthesis in high-risk women's breast tissue.

Breast cancer risk continues to increase post menopause. Anti-estrogen therapies are available to prevent postmenopausal breast cancer in high-risk women. However, their adverse effects have reduced acceptability and overall success in cancer prevention. Natural products such as hops (Humulus lupulus) and three pharmacopeial licorice (Glycyrrhiza) species have demonstrated estrogenic and chemopreventive properties, but little is known regarding their effects on aromatase expression and activity as well as pro-proliferation pathways in human breast tissue. We show that Gycyrrhiza inflata (GI) has the highest aromatase inhibition potency among these plant extracts. Moreover, phytoestrogens such as liquiritigenin which is common in all licorice species have potent aromatase inhibitory activity, which is further supported by computational docking of their structures in the binding pocket of aromatase. In addition, GI extract and liquiritigenin suppress aromatase expression in the breast tissue of high-risk postmenopausal women. Although liquiritigenin has estrogenic effects in vitro, with preferential activity through estrogen receptor (ER)-ß, it reduces estradiol-induced uterine growth in vivo. It downregulates RNA translation, protein biosynthesis, and metabolism in high-risk women's breast tissue. Finally, it reduces the rate of MCF-7 cell proliferation, with repeated dosing. Collectively, these data suggest that liquiritigenin has breast cancer prevention potential for high-risk postmenopausal women.

Kaempferol, a Phytoprogestin, Induces a Subset of Progesterone-Regulated Genes in the Uterus.

Progesterone functions as a steroid hormone involved in female reproductive physiology. While some reproductive disorders manifest with symptoms that can be treated by progesterone or synthetic progestins, recent data suggest that women also seek botanical supplements to alleviate these symptoms. However, botanical supplements are not regulated by the U.S. Food and Drug Administration and therefore it is important to characterize and quantify the inherent active compounds and biological targets of supplements within cellular and animal systems. In this study, we analyzed the effect of two natural products, the flavonoids, apigenin and kaempferol, to determine their relationship to progesterone treatment in vivo. According to immunohistochemical analysis of uterine tissue, kaempferol and apigenin have some progestogenic activity, but do not act in exactly the same manner as progesterone. More specifically, kaempferol treatment did not induce HAND2, did not change proliferation, and induced ZBTB16 expression. Additionally, while apigenin treatment did not appear to dramatically affect transcripts, kaempferol treatment altered some transcripts (44%) in a similar manner to progesterone treatment but had some unique effects as well. Kaempferol regulated primarily unfolded protein response, androgen response, and interferon-related transcripts in a similar manner to progesterone. However, the effects of progesterone were more significant in regulating thousands of transcripts making kaempferol a selective modifier of signaling in the mouse uterus. In summary, the phytoprogestins, apigenin and kaempferol, have progestogenic activity in vivo but also act uniquely.

The Flavonoid Baicalein Negatively Regulates Progesterone Target Genes in the Uterus in Vivo.

Baicalein is a flavonoid extracted from the root of Scutellaria baicalensis (Chinese skullcap) and is consumed as part of this botanical dietary supplement to reduce oxidative stress, pain, and inflammation. We previously reported that baicalein can also modify receptor signaling through the progesterone receptor (PR) and glucocorticoid receptor (GR) in vitro, which is interesting due to the well-established roles of both PR and GR in reducing inflammation. To understand the effects of baicalein on PR and GR signaling in vivo in the uterus, ovariectomized CD-1 mice were treated with DMSO, progesterone (P4), baicalein, P4 with baicalein, and P4 with RU486, a PR antagonist, for a week. The uteri were collected for histology and RNA sequencing. Our results showed that baicalein attenuated the antiproliferative effect of P4 on luminal epithelium as well as on the PR target genes HAND2 and ZBTB16. Baicalein did not change levels of PR or GR RNA or protein in the uterus. RNA sequencing data indicated that many transcripts significantly altered by baicalein were regulated in the opposite direction by P4. Similarly, a large portion of GO/KEGG terms and GSEA gene sets were altered in the opposite direction by baicalein as compared to P4 treatment. Treatment of baicalein did not change body weight, organ weight, or blood glucose level. In summary, baicalein functioned as a PR antagonist in vivo and therefore may oppose P4 action under certain conditions such as uterine hyperplasia, fibroids, and uterine cancers.

Irilone, a Red Clover Isoflavone, Combined with Progesterone Enhances PR Signaling through the Estrogen and Glucocorticoid Receptors.

Trifolium pratense L. (red clover) is a popular botanical supplement used for women's health. Irilone isolated from red clover previously demonstrated progestogenic potentiation activity. In this study, irilone enhanced progesterone signaling was determined to not occur due to post-translational phosphorylation or by reducing progesterone receptor (PR) protein levels but instead increased PR protein levels in T47D breast cancer cells, which could be blocked by estrogen receptor (ER) antagonists, suggesting an ER dependent effect. Further, irilone increased luciferase activity from a hormone responsive element in a cell line that lacked ER and PR but expressed the glucocorticoid receptor (GR). A siRNA knockdown of GR in Ishikawa PR-B endometrial cancer cells reduced irilone's ability to enhance progesterone signaling. In an ovariectomized CD-1 mouse model, irilone did not induce uterine epithelial cell proliferation. The mechanism of action of irilone gives insight into PR crosstalk with other steroid hormone receptors, which can be important for understanding botanicals that are used for women's health.

Silencing PTEN in the fallopian tube promotes enrichment of cancer stem cell-like function through loss of PAX2.

High-grade serous ovarian cancer (HGSOC) is the most lethal gynecological malignancy that is primarily detected at the metastatic stage. Most HGSOC originates from the fallopian tube epithelium (FTE) and metastasizes to the ovary before invading the peritoneum; therefore, it is crucial to study disease initiation and progression using FTE-derived models. We previously demonstrated that loss of PTEN from the FTE leads to ovarian cancer. In the present study, loss of PTEN in FTE led to the enrichment of cancer stem cell markers such as LGR5, WNT4, ALDH1, CD44. Interestingly, loss of the transcription factor PAX2, which is a common and early alteration in HGSOC, played a pivotal role in the expression of cancer stem-like cells (CSC) markers and cell function. In addition, loss of PTEN led to the generation of two distinct subpopulations of cells with different CSC marker expression, tumorigenicity, and chemoresistance profiles. Taken together, these data suggest that loss of PTEN induces reprogramming of the FTE cells into a more stem-like phenotype due to loss of PAX2 and provides a model to study early events during the FTE-driven ovarian cancer tumor formation.

Mammary Tumors Growing in the Absence of Growth Hormone Are More Sensitive to Doxorubicin Than Wild-Type Tumors.

Previously, we reported that N-methyl-N-nitrosourea (MNU)-induced mammary tumors could be established in mutant spontaneous dwarf rats (SDRs), which lack endogenous growth hormone (GH) by supplementing with exogenous GH, and almost all such tumors regressed upon GH withdrawal. When the highly inbred SDR line was outcrossed to wild-type (WT) Sprague-Dawley rats, MNU-induced mammary tumors could still be established in resulting outbred SDRs by supplementing with exogenous GH. However, unlike tumors in inbred SDRs, 65% of mammary tumors established in outbred SDRs continued growth after GH withdrawal. We further tested whether these tumors were more sensitive to doxorubicin than their WT counterparts. To accomplish this, MNU-induced mammary tumors were established in WT rats and in SDRs supplemented with exogenous GH. Once mammary tumors reached 1 cm3 in size, exogenous GH was withdrawn from SDRs, and the subset that harbored tumors that continued or resumed growth in the absence of GH were selected for doxorubicin treatment. Doxorubicin was then administered in 6 injections over 2 weeks at 2.5 mg/kg or 1.25 mg/kg for both the WT and SDR groups. The SDR mammary tumors that had been growing in the absence of GH regressed at both doxorubicin doses while WT tumors continued to grow robustly. The regression of SDR mammary tumors treated with 1.25 mg/kg doxorubicin was accompanied by reduced proliferation and dramatically higher apoptosis relative to the WT mammary tumors treated with 1.25 mg/kg doxorubicin. These data suggest that downregulating GH signaling may decrease the doxorubicin dose necessary to effectively treat breast cancer.

Baicalein Is a Phytohormone that Signals Through the Progesterone and Glucocorticoid Receptors.

While flavonoids have been studied extensively for estrogen receptor activity, they have not been well studied for their ability to modify progesterone receptor (PR) and glucocorticoid receptor (GR) signaling. Three flavonoid compounds, tangeretin, wogonin, and baicalein, were selected for testing for PR and GR activity based on their structural similarity to known phytoprogesterone-like compounds. Each compound was docked in the binding pocket of PR and GR. Of these compounds, baicalein was predicted to be most likely to bind to both receptors. A fluorescence polarization competitive binding assay for PR and GR confirmed that baicalein binds to both the PR and GR with IC50 values of 15.30 µM and 19.26 µM, respectively. In Ishikawa PR-B and T47D cells, baicalein acted as a PR antagonist in a hormone response element (HRE) luciferase (Luc) assay. In OVCAR5 cells, which only express GR, baicalein was a GR agonist via an HRE/Luc assay and induced GR target genes, FKBP5 and GILZ. RU486, a PR and GR antagonist, abrogated baicalein's activity in OVCAR5 cells, confirming baicalein's activity is mediated through the GR. In vivo, baicalein administered intraperitoneally to female mice twice a week for 4 weeks at a dose of 25 mg/kg induced the GR target gene GILZ in the reproductive tract, which was blocked by RU486. In summary, baicalein has PR antagonist and GR agonist activity in vitro and demonstrates GR agonist activity in the uterus in vivo.

Loss of PTEN in Fallopian Tube Epithelium Results in Multicellular Tumor Spheroid Formation and Metastasis to the Ovary.

High-grade serous ovarian cancer (HGSOC) can originate in the fallopian tube and then spread to the ovary. Our objective was to evaluate the role of multicellular tumor spheroids (MTS) in ovarian metastasis. By testing a panel of murine oviductal epithelial (MOE) cells with genetic alterations mimicking those seen in HGSOC, we found that loss of PTEN allowed MTS formation under ultra-low adhesion conditions. Confirming these results in vivo, MTS-like structures were observed in the oviducts of PAX8Cre/+ PTENflox/flox mice. MOE PTENshRNA cells could incorporate up to 25% wild type cells into MTS, while higher percentages of wild type cells resulted in a loss of MTS formation. MTS formation allowed MOE PTENshRNA cells to survive better under ultra-low adhesion conditions than control cells. MTS also attached to the ovarian stroma, as would be exposed during ovulation. Interestingly, MTS more robustly cleared monolayers of murine ovarian surface epithelia than murine ovarian fibroblasts. When xenografted into the ovarian bursa, OVCAR8 MTS were able to form tumors in the ovary at a similar rate as an equal number of OVCAR8 cells grown on traditional cell culture plastic. In conclusion, loss of a single gene (PTEN) allows the fallopian tube epithelia to form MTS, which survive better under ultra-low adhesion conditions, attach to the extracellular matrix exposed during ovulation, and colonize the ovary. These results suggest that MTS may contribute to seeding of the ovary in HGSOC patients.

Bioactivity-Guided Isolation of Totarane-Derived Diterpenes from Podocarpus neriifolius and Structure Revision of 3-Deoxy-2α-hydroxynagilactone E.

Bioactivity-guided phytochemical investigation of Podocarpus neriifolius D. Don. (Podocarpaceae) has led to the isolation of one new (2) and three known (1, 3, and 4) B-type podolactones, along with three totarane-type diterpenes (5-7). Their structures were determined by interpretation of High Resolution ElectroSpray Ionization Mass Spectrometry (HRESIMS) and 1D and 2D NMR data, and comparison with the values reported in the literature. The structure of compound 1, previously identified as 3-deoxy-2α-hydroxynagilactone E (8), was revised as its 2ß-epimer, which has been reported recently as a new compound. All of the isolates were evaluated for their antiproliferative activity against a panel of four human cancer cell lines, namely, ovarian (OVCAR3), breast (MDA-MB-231), colon (HT-29), and melanoma (MDA-MB-435), and compounds 1 and 3 were found to be cytotoxic with IC50 values in the low micromolar range for most of the cell lines used. The major compound, inumakilactone A (3), was further tested in vivo using the HT-29, MDA-MB-435, and OVCAR3 cells in a murine hollow fiber model, for the first time.

Exposure of the extracellular matrix and colonization of the ovary in metastasis of fallopian-tube-derived cancer.

High-grade serous ovarian cancer (HGSOC) can originate in the fallopian tube epithelium (FTE), but the role of the ovary in these tumors is unclear. Tumorigenic murine oviductal epithelial (MOE) cells allografted in the ovarian bursa resulted in aggressive tumors that spread throughout the peritoneum whereas intraperitoneal xenografting the same number of cells did not form tumors, indicating that colonization of the ovary may play a role in metastasis. Physical tearing of the ovarian surface to mimic rupture of the ovary during ovulation (independent of hormonal changes) resulted in more MOE and HGSOC cells adhering to the ovary compared with intact ovaries. More MOE cells also adhered to three-dimensional (3D) collagen and primary ovarian stromal cells than to ovarian surface epithelia, indicating that FTE cells adhered to the extracellular matrix exposed during ovulation. However, plating cells on 3D collagen reduced the viability of normal FTE but not cancer cells. Mutation of p53 (R273H or R248W) and activation of Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) (G12V) did not increase the viability of MOE cells on 3D collagen. In contrast, loss of phosphatase and tensin homolog (PTEN) allowed MOE cells to retain normal viability on 3D collagen. Loss of PTEN activated AKT and RAC1/c-jun N-terminal kinase signaling that each contributed to the increased viability, invasion and attachment in the collagen rich ovarian microenvironment. These results show that loss of PTEN activates multiple pathways that together enhance colonization of the ovary due to access to 3D collagen, which is a critical organ in the colonization of FTE-derived HGSOC.

Evidence for Chemopreventive and Resilience Activity of Licorice: Glycyrrhiza Glabra and G. Inflata Extracts Modulate Estrogen Metabolism in ACI Rats.

Women are increasingly using botanical dietary supplements (BDS) to reduce menopausal hot flashes. Although licorice (Glycyrrhiza sp.) is one of the frequently used ingredients in BDS, the exact plant species is often not identified. We previously showed that in breast epithelial cells (MCF-10A), Glycyrrhiza glabra (GG) and G. inflata (GI), and their compounds differentially modulated P450 1A1 and P450 1B1 gene expression, which are responsible for estrogen detoxification and genotoxicity, respectively. GG and isoliquiritigenin (LigC) increased CYP1A1, whereas GI and its marker compound, licochalcone A (LicA), decreased CYP1A1 and CYP1B1 The objective of this study was to determine the distribution of the bioactive licorice compounds, the metabolism of LicA, and whether GG, GI, and/or pure LicA modulate NAD(P)H quinone oxidoreductase (NQO1) in an ACI rat model. In addition, the effect of licorice extracts and compounds on biomarkers of estrogen chemoprevention (CYP1A1) as well as carcinogenesis (CYP1B1) was studied. LicA was extensively glucuronidated and formed GSH adducts; however, free LicA as well as LigC were bioavailable in target tissues after oral intake of licorice extracts. GG, GI, and LicA caused induction of NQO1 activity in the liver. In mammary tissue, GI increased CYP1A1 and decreased CYP1B1, whereas GG only increased CYP1A1 LigC may have contributed to the upregulation of CYP1A1 after GG and GI administration. In contrast, LicA was responsible for GI-mediated downregulation of CYP1B1 These studies highlight the polypharmacologic nature of botanicals and the importance of standardization of licorice BDS to specific Glycyrrhiza species and to multiple constituents.

Phyllanthusmin Derivatives Induce Apoptosis and Reduce Tumor Burden in High-Grade Serous Ovarian Cancer by Late-Stage Autophagy Inhibition.

High-grade serous ovarian cancer (HGSOC) is a lethal gynecological malignancy with a need for new therapeutics. Many of the most widely used chemotherapeutic drugs are derived from natural products or their semi-synthetic derivatives. We have developed potent synthetic analogues of a class of compounds known as phyllanthusmins, inspired by natural products isolated from Phyllanthus poilanei Beille. The most potent analogue, PHY34, had the highest potency in HGSOC cell lines in vitro and displayed cytotoxic activity through activation of apoptosis. PHY34 exerts its cytotoxic effects by inhibiting autophagy at a late stage in the pathway, involving the disruption of lysosomal function. The autophagy activator, rapamycin, combined with PHY34 eliminated apoptosis, suggesting that autophagy inhibition may be required for apoptosis. PHY34 was readily bioavailable through intraperitoneal administration in vivo where it significantly inhibited the growth of cancer cell lines in hollow fibers, as well as reduced tumor burden in a xenograft model. We demonstrate that PHY34 acts as a late-stage autophagy inhibitor with nanomolar potency and significant antitumor efficacy as a single agent against HGSOC in vivo This class of compounds holds promise as a potential, novel chemotherapeutic and demonstrates the effectiveness of targeting the autophagic pathway as a viable strategy for combating ovarian cancer. Mol Cancer Ther; 17(10); 2123-35. ©2018 AACR.

Prolactin signaling drives tumorigenesis in human high grade serous ovarian cancer cells and in a spontaneous fallopian tube derived model.

The pathways responsible for tumorigenesis of high grade serous ovarian cancer (HGSOC) from the fallopian tube epithelium (FTE) are still poorly understood. A human prolactin (PRL) like gene, Prl2c2 was amplified >100 fold in a spontaneous model of FTE-derived ovarian cancer (MOEhigh - murine oviductal epithelium high passage). Prl2c2 stable knockdown in MOEhigh cells demonstrated a significant reduction in cell proliferation, 2-dimensional foci, anchorage independent growth, and blocked tumor formation. The overall survival of ovarian cancer patients from transcriptome analysis of 1868 samples was lower when abundant PRL and prolactin receptors (PRL-R) were expressed. A HGSOC cell line (OVCAR3) and a tumorigenic human FTE cell line (FT33-Tag-Myc) were treated with recombinant PRL and a significant increase in cellular proliferation was detected. A CRISPR/Cas9 mediated PRL-R deletion in OVCAR3 and FT33-Tag-Myc cells demonstrated significant reduction in cell proliferation and eliminated tumor growth using the OVCAR3 model. PRL was found to phosphorylate STAT5, m-TOR and ERK in ovarian cancer cells. This study identified Prl2c2 as a driver of tumorigenesis in a spontaneous model and confirmed that prolactin signaling supports tumorigenesis in high grade serous ovarian cancer.

The Flavonoid Apigenin Is a Progesterone Receptor Modulator with In Vivo Activity in the Uterus.

Apigenin is a flavonoid with well-documented anti-cancer properties; however, its mechanisms of action are still unclear. We previously identified apigenin as a potential phytoprogestin, a natural product with a chemical scaffold that interacts with the progesterone receptor (PR). Our objective was to characterize the ability of apigenin to interact with PR through molecular docking studies, in vitro activity assays, and the ability of apigenin to elicit progestin-like effects in vivo. Molecular docking confirmed that apigenin could interact with PR, though with lower affinity than progesterone due to fewer van der Waals interactions. In Ishikawa cells stably expressing PR-B, apigenin significantly increased progesterone response element/luciferase (PRE/Luc) activity at 5 and 10 µM, but not in the parental Ishikawa cells that lack PR expression. In the presence of 100 nM of progesterone, 10 µM apigenin reduced PRE/Luc activity, indicative of mixed agonist activity. Apigenin also triggered degradation of PR in Ishikawa PR-B cells as measured by western blot. Apigenin reduced proliferation of Ishikawa cells, but through a PR-independent mechanism. In contrast, apigenin and progesterone both stimulated proliferation of T47D cells, an effect blocked by RU486. Apigenin activated other nuclear receptors evidenced by increased luciferase activity in MDA-MB-231 cells, which are PR negative. In vivo, apigenin blocked the genistein-stimulated increase in uterine epithelial cell height; stimulated endometrial expression of Hand2, a transcription factor stimulated by PR, and significantly reduced genistein-induced proliferation. In summary, apigenin is a phytoprogestin, with mixed agonist activity that demonstrates activity in vivo by hindering estrogen receptor-mediated uterine proliferation.

PTEN loss in the fallopian tube induces hyperplasia and ovarian tumor formation.

The signaling events involved in the onset of ovarian cancer from the fallopian tube epithelium (FTE) are crucial for early detection and treatment of the disease, but they remain poorly defined. Conditional homozygous knockout of PTEN mediated by PAX8-cre recombinase was sufficient to drive endometrioid and serous borderline ovarian carcinoma, providing the first model of FTE-derived borderline tumors. In addition, heterozygous PTEN deletion in the FTE resulted in hyperplasia, providing a model to study early events of human ovarian pathogenesis. To uncover the mechanism underlying the invasion of cancerous oviductal cells to the ovary, PTEN-deficient murine oviductal cells were developed and tagged with green fluorescent protein. Loss of PTEN increased cell migration, invasion, and upregulated WNT4, a key regulator of Müllerian duct development during embryogenesis. Further investigation revealed that WNT4 was required for increased migration and colonization of the ovary by PTEN-deficient oviductal cells in a ß-catenin independent manner. Human tumor microarrays and ovarian cancer cells lines confirmed WNT4 expression in cancer and its role in migration. Together, these findings provide a novel model to study the mechanism of fallopian tube tumor initiation and invasion to the ovary mediated by loss of PTEN, which may help to define early events of human ovarian carcinogenesis.

Merocyclophanes C and D from the Cultured Freshwater Cyanobacterium Nostoc sp. (UIC 10110).

Merocyclophanes C and D (1 and 2) were isolated from the cell extract of the cultured cyanobacterium UIC 10110. The structures were determined by one-dimensional nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry and confirmed by 2D NMR techniques. The absolute configurations were determined using electronic circular dichroism spectroscopy. Merocyclophanes C and D represent the first known analogues of the merocyclophane core structure, a recently discovered scaffold of [7,7] paracyclophanes characterized by an α-branched methyl at C-1/C-14; 1 and 2 showed antiproliferative activity against the MDA-MB-435 cell line with IC50 values of 1.6 and 0.9 µM, respectively. Partial 16S analysis determined UIC 10110 to be a Nostoc sp., and it was found to clade with UIC 10062 Nostoc sp., the only other strain known to produce merocyclophanes. The genome of UIC 10110 was sequenced, and a biosynthetic gene cluster was identified that is proposed to encode type I and type III polyketide synthases that are potentially responsible for production of the merocyclophanes; however, further experiments will be required to verify the true function of the gene cluster. The gene cluster provides a genetic basis for the observed structural differences of the [7,7] paracyclophane core structures.

Cardiac Glycoside Constituents of Streblus asper with Potential Antineoplastic Activity.

Three new (1-3) and two known (4 and 5) cytotoxic cardiac glycosides were isolated and characterized from a medicinal plant, Streblus asper Lour. (Moraceae), collected in Vietnam, with six new analogues and one known derivative (5a-g) synthesized from (+)-strebloside (5). A preliminary structure-activity relationship study indicated that the C-10 formyl and C-5 and C-14 hydroxy groups and C-3 sugar unit play important roles in the mediation of the cytotoxicity of (+)-strebloside (5) against HT-29 human colon cancer cells. When evaluated in NCr nu/nu mice implanted intraperitoneally with hollow fibers facilitated with either MDA-MB-231 human breast or OVCAR3 human ovarian cancer cells, (+)-strebloside (5) showed significant cell growth inhibitory activity in both cases, in the dose range 5-30 mg/kg.

Cadherin-6 type 2, K-cadherin (CDH6) is regulated by mutant p53 in the fallopian tube but is not expressed in the ovarian surface.

High-grade serous ovarian cancer (HGSOC) is the most lethal gynecological malignancy and may arise in either the fallopian tube epithelium (FTE) or ovarian surface epithelium (OSE). A mutation in p53 is reported in 96% of HGSOC, most frequently at R273 and R248. The goal of this study was to identify specific gene targets in the FTE that are altered by mutant p53, but not in the OSE. Gene analysis revealed that both R273 and R248 mutant p53 reduces CDH6 expression in the oviduct, but CDH6 was not detected in murine OSE cells. p53R273H induced SLUG and FOXM1 while p53R248W did not induce SLUG and only modestly increased FOXM1, which correlated with less migration as compared to p53R273H. An oviduct specific PAX8Cre/+/p53R270H/+ mouse model was created and confirmed that in vivo mutant p53 repressed CDH6 but was not sufficient to stabilize p53 expression alone. Overexpression of mutant p53 in the p53 null OVCAR5 cells decreased CDH6 levels indicating this was a gain-of-function. SLUG knockdown in murine oviductal cells with p53R273H restored CDH6 repression and a ChIP analysis revealed direct binding of mutant p53 on the CDH6 promoter. NSC59984, a small molecule that degrades mutant p53R273H, rescued CDH6 expression. In summary, CDH6 is expressed in the oviduct, but not the ovary, and is repressed by mutant p53. CDH6 expression with further validations may aide in establishing markers that inform upon the cell of origin of high grade serous tumors.