Hye-Rim Lee

Cell growth of BG-1 ovarian cancer cells is promoted by di-n-butyl phthalate and hexabromocyclododecane via upregulation of the cyclin D and cyclin-dependent kinase-4 genes

Endocrine-disrupting chemicals (EDCs) are environmentally persistent exogenous compounds released from various industrial products such as plastics, pesticides, drugs, detergents and cosmetics. They can cause a variety of adverse effects to the reproductive, developmental, immune and nervous systems in humans and wildlife. Di-n-butyl phthalate (DBP) is the main compound of phthalates and is reported to inhibit estrogen receptor (ER)-mediated gene expression and to interfere with normal fetal development of the male reproductive system. Hexabromocyclododecane (HBCD or HBCDD) is one of the brominated flame retardants (BFRs) which have been widely used in plastic, electronic and textile applications and are known to cause endocrine disruption with toxicity of the nervous system. In the present study, the estrogenic effects of DBP and HBCD were examined in an ovarian cancer cell line, BG-1, expressing high levels of ER via MTT assay and semi-quantitative reverse-transcription PCR. Treatment with DBP (10(-8)-10(-5) M) or HBCD (2 x 10(-8) -2 x 10(-6) M) resulted in increased cell proliferation of BG-1 cells as observed with 17-β estradiol (E2). In addition, both DBP and HBCD upregulated the expression levels of cell cycle-regulatory genes, such as cyclin D and cyclin-dependent kinase-4 (cdk-4), which are downstream target genes of ER, at 6 h after treatment. However, the expression of the p21 gene was not altered by DBP or HBCD at any time as with E2. Taken together, these results suggest that DBP and HBCD are EDCs which have apparent estrogenic activities by stimulating the cell proliferation of BG-1 cells and by inducing the expression of cyclin D and cdk-4. Our results suggest that DBP and HBCD have sufficient potency to disrupt the endocrine system and to stimulate cell growth in ER-positive cancer cells.

Functions and physiological roles of two types of estrogen receptors, ERα and ERβ, identified by estrogen receptor knockout mouse.

Estrogens, a class of steroid hormones, regulate the growth, development, and physiology of the human reproductive system. Estrogens also involve in the neuroendocrine, skeletal, adipogenesis, and cardiovascular systems. Estrogen signaling pathways are selectively stimulated or inhibited depending on a balance between the activities of estrogen receptor (ER) α or ERβ in target organs. ERs belong to the steroid hormone superfamily of nuclear receptors, which act as transcription factors after binding to estrogen. The gene expression regulation by ERs is to modulate biological activities, such as reproductive organ development, bone modeling, cardiovascular system functioning, metabolism, and behavior in both females and males. Understanding of the general physiological roles of ERs has been gained when estrogen levels were ablated by ovariectomy and then replenished by treatment with exogenous estrogen. This technique is not sufficient to fully determine the exact function of estrogen signaling in general processes in living tissues. However, a transgenic mouse model has been useful to study gene-specific functions. ERα and ERβ have different biological functions, and knockout and transgenic animal models have distinct phenotypes. Analysis of ERα and ERβ function using knockout mouse models has identified the roles of estrogen signaling in general physiologic processes. Although transgenic mouse models do not always produce consistent results, they are the useful for studying the functions of these genes under specific pathological conditions.

Progression of breast cancer cells was enhanced by endocrine-disrupting chemicals, triclosan and octylphenol, via an estrogen receptor-dependent signaling pathway in cellular and mouse xenograft models.

In the present study, we determined whether two endocrine-disrupting chemicals (EDCs), triclosan (TCS) and octylphenol (OP), are able to alter the expression of two cell cycle regulators, cyclin D1 and p21, in both in vitro and mouse breast cancer models. In addition, we determined whether the stimulatory effects of OP or TCS on breast cancer progression may be associated with an estrogen receptor (ER)-mediated signaling pathway. Altered expressions of cyclin D1 and p21 were observed in MCF-7 human breast cancer cells treated with TCS and OP, which is linked to the G1/S transition of cell cycle, leading to cell proliferation. In a xenograft mouse model, breast tumor masses were established following exposure to TCS and OP for 8 weeks. In these animals, the tumor cells with BrdU-positive nuclei were increased by treatment with 17β-estradiol (E2), OP, and TCS compared to that of a control (corn oil), suggesting that TCS and OP increase DNA synthesis during the S phase in tumor cells. Increased level of cyclin D1 protein by TCS and OP was also observed in vivo, implying that the effects of these EDCs possessing estrogenic activity alter the expression of genes related to cancer progression. It was of interest that the effects of TCS and OP were reversed by ICI 182,780, an ER antagonist, indicating that EDC-induced activities are mediated by an ER-dependent signaling pathway. Taken together, these results suggest that TCS and OP may promote breast cancer progression, via an ER-mediated signaling cascade.

Molecular mechanism(s) of endocrine-disrupting chemicals and their potent oestrogenicity in diverse cells and tissues that express oestrogen receptors

Endocrine‐disrupting chemicals (EDCs) are natural or synthetic compounds present in the environment which can interfere with hormone synthesis and normal physiological functions of male and female reproductive organs. Most EDCs tend to bind to steroid hormone receptors including the oestrogen receptor (ER), progesterone receptor (PR) and androgen receptor (AR). As EDCs disrupt the actions of endogenous hormones, they may induce abnormal reproduction, stimulation of cancer growth, dysfunction of neuronal and immune system. Although EDCs represent a significant public health concern, there are no standard methods to determine effect of EDCs on human beings. The mechanisms underlying adverse actions of EDC exposure are not clearly understood. In this review, we highlighted the toxicology of EDCs and its effect on human health, including reproductive development in males and females as shown in in vitro and in vivo models. In addition, this review brings attention to the toxicity of EDCs via interaction of genomic and non‐genomic signalling pathways through hormone receptors.

Benzophenone-1 stimulated the growth of BG-1 ovarian cancer cells by cell cycle regulation via an estrogen receptor alpha-mediated signaling pathway in cellular and xenograft mouse models.

2,4-Dihydroxybenzophenone (benzophenone-1; BP-1) is an UV stabilizer primarily used to prevent polymer degradation and deterioration in quality due to UV irradiation. Recently, BP-1 has been reported to bioaccumulate in human bodies by absorption through the skin and has the potential to induce health problems including endocrine disruption. In the present study, we examined the xenoestrogenic effect of BP-1 on BG-1 human ovarian cancer cells expressing estrogen receptors (ERs) and relevant xenografted animal models in comparison with 17-β estradiol (E2). In in vitro cell viability assay, BP-1 (10(-8)-10(-5)M) significantly increased BG-1 cell growth the way E2 did. The mechanism underlying the BG-1 cell proliferation was proved to be related with the up-regulation of cyclin D1, a cell cycle progressor, by E2 or BP-1. Both BP-1 and E2 induced cell growth and up-regulation of cyclin D1 were reversed by co-treatment with ICI 182,780, an ER antagonist, suggesting that BP-1 may mediate the cancer cell proliferation via an ER-dependent pathway like E2. On the other hand, the expression of p21, a regulator of cell cycle progression at G1 phase, was not altered by BP-1 though it was down-regulated by E2. In xenograft mouse models transplanted with BG-1 cells, BP-1 or E2 treatment significantly increased the tumor mass formation compared to a vehicle (corn oil) within 8 weeks. In histopathological analysis, the tumor sections of E2 or BP-1 group displayed extensive cell formations with high density and disordered arrangement, which were supported by the increased number of BrdUrd positive nuclei and the over-expression of cyclin D1 protein. Taken together, these results suggest that BP-1 is an endocrine disrupting chemical (EDC) that exerts xenoestrogenic effects by stimulating the proliferation of BG-1 ovarian cancer via ER signaling pathway associated with cell cycle as did E2.

Stem cells with fused gene expression of cytosine deaminase and interferon-β migrate to human gastric cancer cells and result in synergistic growth inhibition for potential therapeutic use

Genetically engineered stem cells (GESTECs) producing suicide enzymes and immunotherapeutic cytokines have therapeutic effects on tumors, and may possibly reduce the side effects of toxic drugs used for treatments. Suicide enzymes can convert non-toxic pro-drugs to toxic metabolites that can reduce tumor growth. Cytosine deaminase (CD) is a suicide enzyme that metabolizes a non-toxic pro-drug, 5-fluorocytosine (5-FC), into the cytotoxic agent, 5-fluorouracil (5-FU). As an immunotherapeutic agent, human interferon-β (IFN-β) has anticancer effects. In this study, we used modified human neural stem cells (HB1.F3) expressing the Escherichia coli (E. coli) CD gene (HB1.F3.CD) or both the CD and human IFN-β genes (HB1.F3.CD.IFN-β) and evaluated their effectiveness on gastric carcinoma cells (AGS); migration of GESTECs to AGS was analyzed as well as formation of 5-FU and IFN-β. Reverse transcription-polymerase chain reaction (RT-PCR) was used to confirm the expression of CD and IFN-β genes in GESTECs along with confirming the production of chemoattractant molecules such as stem cell factor (SCF), CXCR4, c-Kit, vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2). In addition, by co-culturing GESTECs with AGS in the presence of 5-FC, we were able to confirm that cancer growth was inhibited, along with a synergistic effect when the CD and IFN-β genes (HB1.F3.CD.IFN-β) were co-expressed. Indeed a marked anticancer effect was demonstrated when the CD and IFN-β genes were expressed together compared to expression of the CD gene alone (HB1.F3.CD). According to a modified transwell migration assay, the migration of GESTECs toward AGS was confirmed. In conclusion, these data suggest potential application of GESTECs to gastric cancer therapy, due to a remarkable synergistic effect of CD and IFN-β genes in the presence of 5-FC. Additionally, the tumor-selective migration capability in vitro suggests that GESTECs are a potential anticancer therapy candidate that may result in minimal side effects compared to the conventional chemotherapy.

4-tert-Octylphenol stimulates the expression of cathepsins in human breast cancer cells and xenografted breast tumors of a mouse model via an estrogen receptor-mediated signaling pathway.

Endocrine disrupting chemicals (EDCs) are defined as environmental compounds that modulate steroid hormone receptor-dependent responses an abnormal manner, resulting in adverse health problems for humans such as cancer growth and metastasis. Cathepsins are proteases that have been implicated in cancer progression. However, there have been few studies about the association between cathepsins and estrogenic chemicals during the cancer progression. In this study, we examined the effect(s) of 4-tert-octylphenol (OP), a potent EDC, on the expression of cathepsins B and D in human MCF-7 breast cancer cells and a xenograft mouse model. Treatment with OP significantly induced the proliferation MCF-7 cells in an MTT assay. In addition, the expression of cathepsins B and D was markedly enhanced in MCF-7 cells at both the transcriptional and the translational levels following treatment with E2 or OP up to 48h. These results demonstrated the ability of OP to disrupt normal transcriptional regulation of cathepsins B and D in human breast cancer cells. However, the effects of OP on cell growth or overexpression of cathepsins by inhibiting ER-mediated signaling were abolished by an ER antagonist and siRNA specific for ERα. In conclusion, our findings suggest that OP at 10(-6)M, like E2, may accelerate breast cancer cell proliferation and the expression of cathepsins through an ER-mediated signaling pathway. In addition, the breast cancer cells exposed with OP to a xenograft mouse model were more aggressive according to our histological analysis and showed markedly increased expression of cathepsin B. These effects of mouse model resulted in an increased potential for metastasis in breast cancer. Taken together, we determined that OP can adversely affect human health by promoting cancer proliferation and metastasis through the amplification of cathepsins B and D via the ER-mediated signaling pathway.

Cell Growth of BG-1 Ovarian Cancer Cells was Promoted by 4-Tert-octylphenol and 4-Nonylphenol via Downregulation of TGF-β Receptor 2 and Upregulation of c-myc

Transforming growth factor β (TGF-β) is involved in cellular processes including growth, differentiation, apoptosis, migration, and homeostasis. Generally, TGF-β is the inhibitor of cell cycle progression and plays a role in enhancing the antagonistic effects of many growth factors. Unlike the antiproliferative effect of TGF-β, E2, an endogeneous estrogen, is stimulating cell proliferation in the estrogen-dependent organs, which are mediated via the estrogen receptors, ERα and ERβ, and may be considered as a critical risk factor in tumorigenesis of hormone-responsive cancers. Previous researches reported the cross-talk between estrogen/ERα and TGF-β pathway. Especially, based on the E2-mediated inhibition of TGF-β signaling, we examined the inhibition effect of 4-tert-octylphenol (OP) and 4-nonylphenol (NP), which are well known xenoestrogens in endocrine disrupting chemicals (EDCs), on TGF-β signaling via semi-quantitative reverse-transcription PCR. The treatment of E2, OP, or NP resulted in the downregulation of TGF- β receptor2 (TGF-β R2) in TGF-β signaling pathway. However, the expression level of TGF-β1 and TGF- β receptor1 (TGF-β R1) genes was not altered. On the other hand, E2, OP, or NP upregulated the expression of a cell-cycle regulating gene, c-myc, which is a oncogene and a downstream target gene of TGF-β signaling pathway. As a result of downregulation of TGF-β R2 and the upregulation of c-myc, E2, OP, or NP increased cell proliferation of BG-1 ovarian cancer cells. Taken together, these results suggest that E2 and these two EDCs may mediate cancer cell proliferation by inhibiting TGF-β signaling via the downregulation of TGF-β R2 and the upregulation of c-myc oncogene. In addition, it can be inferred that these EDCs have the possibility of tumorigenesis in estrogen-responsive organs by certainly representing estrogenic effect in inhibiting TGF-β signaling.

Suppression of the growth of human colorectal cancer cells by therapeutic stem cells expressing cytosine deaminase and interferon-β via their tumor-tropic effect in cellular and xenograft mouse models

Genetically engineered stem cells (GESTECs) exhibit a potent therapeutic efficacy via their strong tumor tropism toward cancer cells. In this study, we introduced the human parental neural stem cells, HB1.F3, with the human interferon beta (IFN‐β) gene which is a typical cytokine gene that has an antitumor effect and the cytosine deaminase (CD) gene from Escherichia coli (E. coli) that could convert the non‐toxic prodrug, 5‐fluorocytosine (5‐FC), to a toxic metabolite, 5‐fluorouracil (5‐FU). Two types of stem cells expressing the CD gene (HB1.F3.CD cells) and both the CD and human IFN‐β genes (HB1.F3.CD.IFN‐β) were generated. The present study was performed to examine the migratory and therapeutic effects of these GESTECs against the colorectal cancer cell line, HT‐29. When co‐cultured with colorectal cancer cells in the presence of 5‐FC, HB1.F3.CD and HB1.F3.CD.IFN‐β cells exhibited the cytotoxicity on HT‐29 cells via the bystander effect. In particular, HB1.F3.CD.IFN‐β cells showed the synergistic cytotoxic activity of 5‐FU and IFN‐β. We also confirmed the migration ability of HB1.F3.CD and HB1.F3.CD.IFN‐β cells toward HT‐29 cells by a modified migration assay in vitro, where chemoattractant factors secreted by HT‐29 cells attracted the GESTECs. In a xenograft mouse model, the volume of tumor mass was decreased up to 56% in HB1.F3.CD injected mice while the tumor mass was greatly inhibited about 76% in HB1.F3.CD.IFN‐β injected mice. The therapeutic treatment by these GESTECs is a novel strategy where the combination of the migration capacity of stem cells as a vector for therapeutic genes towards colorectal cancer and a synergistic antitumor effect of CD and IFN‐β genes can selectively target this type of cancer.

Modulation of lipid metabolism by mixtures of protamine and chitooligosaccharide through pancreatic lipase inhibitory activity in a rat model

Overweight and obesity are usually related with high fat and calorie intake, and seriously causative of lifestyle-related diseases such as cardiovascular disorders, arteriosclerosis, and colon cancer. In this study, we propose a novel dietary therapy against overweight and obesity using mixtures of protamine and chitooligosaccharide (COS), which are known to interrupt the lipid metabolism in the body. Protamine is a dietary protein originated from salmon reproductive organ, and COS is an oligosaccharide made from chitin or chitosan by chemical or enzymatic hydrolysis. In the enzyme activity analysis in vitro, protamine and COS strongly suppressed the activity of pancreatic lipase, which is the primary enzyme for the digestion and absorption of lipids in the intestine. In in vivo animal test, the mixtures of protamine and COS significantly reduced the serum levels of triglyceride (TG), total cholesterol (T-CHO), and low density lipoprotein-cholesterol (LDLC) and inhibited the accumulation of lipids in liver tissue of Sprague Dawley (SD) rats fed high fat diets. On the other hand, they increased fecal TG and T-CHO contents. From these alterations in lipid metabolism, we verified that protamine and COS mixtures could effectively interrupt the digestion and absorption of dietary lipids in the body by inhibiting pancreatic lipase activity. In addition, protamine and COS mixtures increased the serum level of high density lipoprotein-cholesterol (HDLC), responsible for removing cholesterol from cells and protecting atherosclerosis, and therefore decreased the potential risks of cardiovascular diseases by lowering values of the atherogenic index (AI) and cardiac risk factor (CRF). Taken together, we suggest protamine and COS mixtures as a prominent dietary therapy for the prevention of overweight, obesity, and further cardiovascular diseases related with hyperlipidemia.