Min-Ah Park

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.

Anticancer effect of genistein on BG-1 ovarian cancer growth induced by 17 β-estradiol or bisphenol A via the suppression of the crosstalk between estrogen receptor alpha and insulin-like growth factor-1 receptor signaling pathways

The interaction between estrogen receptor (ER) and insulin-like growth factor-1 receptor (IGF-1R) signaling pathway plays an important role in proliferation of and resistance to endocrine therapy to estrogen dependent cancers. Estrogen (E2) upregulates the expression of components of IGF-1 system and induces the downstream of mitogenic signaling cascades via phosphorylation of insulin receptor substrate-1 (IRS-1). In the present study, we evaluated the xenoestrogenic effect of bisphenol A (BPA) and antiproliferative activity of genistein (GEN) in accordance with the influence on this crosstalk. BPA was determined to affect this crosstalk by upregulating mRNA expressions of ERα and IGF-1R and inducing phosphorylation of IRS-1 and Akt in protein level in BG-1 ovarian cancer cells as E2 did. In the mouse model xenografted with BG-1 cells, BPA significantly increased a tumor burden of mice and expressions of ERα, pIRS-1, and cyclin D1 in tumor mass compared to vehicle, indicating that BPA induces ovarian cancer growth by promoting the crosstalk between ER and IGF-1R signals. On the other hand, GEN effectively reversed estrogenicity of BPA by reversing mRNA and protein expressions of ERα, IGF-1R, pIRS-1, and pAkt induced by BPA in cellular model and also significantly decreased tumor growth and in vivo expressions of ERα, pIRS-1, and pAkt in xenografted mouse model. Also, GEN was confirmed to have an antiproliferative effect by inducing apoptotic signaling cascades. Taken together, these results suggest that GEN effectively reversed the increased proliferation of BG-1 ovarian cancer by suppressing the crosstalk between ERα and IGF-1R signaling pathways upregulated by BPA or E2.

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.

Effects of 4-nonylphenol and bisphenol A on stimulation of cell growth via disruption of the transforming growth factor-β signaling pathway in ovarian cancer models.

Transforming growth factor β (TGF-β) signaling pathway is a major pathway in cellular processes such as cell growth, apoptosis, and cellular homeostasis. The signaling pathway activated by 17β-estadiol (E2) appeared to inhibit the TGF-β signaling pathway by cross-talk with the TGF-β components in estrogen receptor (ER) positive cells. In this study, we examined the inhibitory effects of endocrine disrupting chemicals (EDCs), including 4-nonylphenol (NP), 4-otylphenol (OP), bisphenol A (BPA), and benzophenon-1 (BP-1), in the TGF-β signaling pathway in BG-1 ovarian cancer cells expressing estrogen receptors (ERs). The transcriptional and translational levels of TGF-β related genes were examined by reverse transcription-PCR (RT-PCR), Western blot analysis, and xenograft mouse models of ovarian cancer cells. As a result, treatment with NP, OP, and BPA induced the expressions of SnoN, a TGF-β pathway inhibitor, and c-Fos, a TGF-β target transcription factor. Treatment with NP, BPA, and BP-1 resulted in decreased phosphorylation of Smad3, a downstream target of TGF-β. These results indicate that NP and BPA may stimulate the proliferation of BG-1 cells via inhibition of the TGF-β signaling pathway. In a xenograft mouse model, transplanted BG-1 ovarian cancer cells showed significantly decreased phosphorylation of Smad3 and increased expression of SnoN in the ovarian tumor masses following treatment with E2, NP, or BPA. In parallel with an in vitro model, the expressions of these TGF-β signaling pathway were similarly regulated by NP or BPA in a xenograft mouse model. These results support the fact that the existence of an unproven relationship between EDCs/ER-α and TGF-β signaling pathway and a further study are required in order to verify more profound and distinct mechanism(s) for the disturbance of the TGF-β signaling pathway by diverse EDCs.

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.

Risk of cardiovascular disease is suppressed by dietary supplementation with protamine and chitooligosaccharide in Sprague-Dawley rats

Protamine from salmon spermaries is a novel dietary protein. Chitooligosaccharide (COS) is an oligosaccharide derived from chitin or chitosan, a long-chain polymer, by chemical or enzymatic hydrolysis. These two compounds are known to enhance lipid metabolism by interrupting the digestion and absorption of fat in the body. Cardiovascular disease (CVD) refers to any type of specific disease that affects the heart and circulatory system. Dyslipidemia, a condition involving high levels of low-density lipoprotein (LDL) cholesterol and low levels of high-density lipoprotein (HDL) cholesterol, is generally known to be a primary cause of CVD development. The risk of CVD is usually associated with the atherogenic index (AI) and cardiac risk factor (CRF). The CVD risk is also closely associated with serum levels of total cholesterol (T-CHO), LDL cholesterol and HDL cholesterol. In the present study, we evaluated alterations in serum lipid contents following the administration of protamine, COS and mixtures of these two compounds to male Sprague-Dawley (SD) rats, and their ability to reduce CVD risk. Based on the results of a serum lipid assay, protamine, COS and their mixtures were found to significantly reduce AI, CRF and CVD risk by decreasing serum levels of TG, T-CHO and LDL cholesterol and increasing serum HDL cholesterol levels. By contrast, TG and T-CHO concentrations in feces were markedly increased. Accumulation of lipids in the liver tissues of the SD rats fed high-fat diets was also inhibited by the intake of protamine and COS. Our findings suggest that protamine, COS and combinations of the two compounds may be used as a dietary therapy for preventing CVD due to their suppressive effects on hyperlipidemia and hypercholesterolemia.