ABSTRACT
Abstract Hepatocellular carcinoma (HCC) is the most common primary liver tumor. Hexachlorobenzene (HCB) is an endocrine disruptor and a liver tumor promoter. Deregulation of thyroid hormone (TH) homeostasis may play a significant role in early neoplastic transformation. The aim of this study was to evaluate the relation between TH metabolism and the regulation of cell growth in an in vivo and in vitro model. We examined the role of transforming growth factor-β1 (TGF-β1) on TH deiodinase expression and hepatocyte proliferation. An initiation (DEN)/promotion (HCB) tumor model from rat liver and HepG2 cells were used. We evaluated PCNA, p21, p27, SMAD2/3, TGF-β1, deiodinase 1 (D1), D3, protein expression levels; D1 and D3 mRNA expression; TH and TGF-β1, D1, D3, and GST-P protein levels in focal/non-focal areas. In vivo, HCB decreased triiodothyronine (T3) and D1 mRNA levels and increased thyroxine (T4) and D3 mRNA levels in liver from DEN+HCB vs. DEN group. HCB increased protein levels from D3, TGF-β1, and PCNA and decreased D1 in focal-areas. In vitro, HCB increased PCNA, pSMAD 2/3, and TGF-β1 protein levels and mRNA expression and decreased p21 and p27 protein levels. Exogenous T3 treatment prevent HCB induced molecular alterations related to hepatocyte proliferation whereas T4 did not have any effect. These effects were prevented by using a TGF-β1 receptor II inhibitor. Results suggest that alteration of TH homeostasis, through D1 function, play a key role in hepatocyte proliferation and that TGF-β1-SMAD pathway is involved in this process confirming their role in early neoplastic transformation in HCC.
Resumen El hepatocarcinoma (HCC) es un tumor hepático primario. El hexaclorobenceno (HCB) es un disruptor endocrino y un promotor de tumores hepáticos. La desregulación de la homeostasis de las hormonas tiroideas (HT) puede ser un proceso importante para la transformación neoplásica temprana. Nuestro objetivo fue evaluar la relación entre el metabolismo de las HT y la regulación de la prolifera ción celular. Se utilizó un modelo tumoral de iniciación (DEN)/promoción (HCB) de hígado de rata (in vivo) (DEN/ HCB) y células HepG2 (in vitro). Evaluamos los niveles de PCNA, p21, p27, SMAD2/3, TGF-β1, D1, D3, ARNm de D1 y D3, HT y los niveles de TGF-β1, D1, D3 y GST-P en áreas focales/no focales. In vivo, HCB disminuyó los niveles de T3 y ARNm de la D1 y aumentó los niveles de T4 y ARNm de D3 del grupo DEN + HCB frente al grupo DEN. El HCB aumentó los niveles de D3, TGF-β1 y PCNA y disminuyó el D1 en las áreas focales. In vitro, HCB aumentó los niveles de PCNA, pSMAD 2/3 y TGF-β1 y la expresión de ARNm mientras que disminuyó los niveles de p21 y p27. El tratamiento con T3 exógeno previno las alteraciones moleculares relacionadas con la proliferación hepatocitaria. Estos efectos se evitaron utilizando un inhibidor del receptor II de TGF-β1. Los resultados sugieren que la alteración de la homeostasis de HT, a través de la D1 y la vía TGF-β1-SMAD, juega un papel clave en la proliferación celular y en las transformaciones neoplásicas tempranas en el HCC.
Subject(s)
Animals , Rats , Carcinoma, Hepatocellular , Transforming Growth Factor beta1 , Iodide Peroxidase/genetics , Liver Neoplasms , Cell ProliferationABSTRACT
Hexachlorobenzene (HCB) is a widespread environmental pollutant and an endocrine disruptor. Chronic exposure of humans to HCB elicits porphyria, neurologic symptoms, immune disorders and thyroid dysfunctions. It is a dioxin-like compound and a weak ligand of the AhR (aryl hydrocarbon receptor), a transcription factor that modulates genes related to detoxification, proliferation, migration and invasion. This study was carried out to revise the results of HCB action on mammary gland and breast cancer, summarizing the main ideas of its mechanism of action. HCB increases tumor development and active c-Src/EGFR (epidermal growth factor receptor) signaling pathways, while reducing tyrosine537-ER-alpha (estrogen receptor-alpha) phosphorylation, and promoting a phenotype with enhanced malignancy and lung metastasis in different animal models. In a rat mammary gland, HCB promotes an estrogenic microenvironment by activation of ER-alpha and Insulin/IGFs (insulin growth factors) pathways. HCB induces cell proliferation, promoting cell cycle progression and enhancing cyclin D1 expression and c-Src/p27 interaction in (ER-alpha) MCF-7 human breast cancer cell line. In (ER-alpha)(-) MDA-MB-231 breast cancer cells, the pesticide enhances cell migration and invasion as well as metalloproteases and TGF-beta1 (transformig growth factor-beta1) expression. In conclusion our current study suggests that alterations in the estrogenic microenvironment may influence the biological behavior of mammary gland or breast tumors, leading to preneoplastic lesions or enhanced malignancy, respectively. Our findings suggest that HCB may be a risk factor for human breast cancer progression.
El hexaclorobenceno (HCB) es un contaminante ambiental ampliamente distribuido y un desorganizador endocrino. Su exposición crónica en seres humanos produce porfiria, síntomas neurológicos, trastornos inmunitarios y disfunciones tiroideas. Es un agonista débil del receptor de hidrocarburos aromáticos (AhR), un factor de transcripción que modula genes relacionados con el metabolismo de xenobióticos, la proliferación, la migración y la invasión. Nuestro objetivo es revisar los efectos del HCB en la glándula mamaria y el cáncer mamario, resumiendo los principales mecanismos de acción. El HCB aumenta el desarrollo tumoral y activa vías de señalización de c-Src/receptor del factor de crecimiento epidérmico (EGFR), mientras que disminuye la fosforilación de tirosina 537/receptor de estrógenos alfa (RE-alfa), promoviendo un fenotipo de mayor malignidad y metástasis pulmonar en diferentes modelos con animales. En la glándula mamaria de rata genera un microambiente estrogénico por activación del RE-alfa y las vías de insulina/factores de crecimiento similares a la insulina (IGF). En células de cáncer mamario humanas MCF-7 (RE-alfa) induce proliferación celular, promoviendo la progresión del ciclo, aumentando la ciclina D1 y la interacción p27/c-Src. En MDA-MB-231 (-RE-alfa) estimula la migración e invasión, así como la expresión de metaloproteasas y factor de crecimiento transformante beta 1 (TGF-beta 1). Estos estudios indican que las alteraciones en el microambiente estrogénico podrían influir el comportamiento biológico de la glándula mamaria y los tumores, lo que provoca lesiones preneoplásicas o aumento en la malignidad tumoral mamaria. Nuestros hallazgos sugieren que el HCB podría ser un factor de riesgo para la progresión del cáncer de mama humano.
Subject(s)
Humans , Pesticides , Breast Neoplasms , HexachlorobenzeneABSTRACT
Background. Persistent organic pollutants include pesticides such as aldrin,dieldrin, endrin, chlordane, heptachlor, hexachlorobenzene, mirex, toxaphene, polychlorinated biphenyls, dioxins, furans. Hexachlorobenzene has been used on timber and unnatural rubber. It has also been used for the preparation of paints and ammunition. HCB is a fungicide for cereals, onion and wheat, and also a byproducts of the pesticide manufacturing process. During the past four decades, great concern and considerable attention have been given to the toxic effects of the hexachlorobenzene that eliminated or restricted the production, use, import and export by the Stockholm convention. The aim of this work is to estimate a dietary intake of hexachlorobenzene with some food by a general population in Mongolia. Goal: The goal of this study is to estimate a dietary intake of hexachlorobenzene with some food by a general population in Mongolia which eliminated or restricted the production, use, import and export in the worldwide by the Stockholm Convention and to assess an oral exposure and health risk. Objectives: 1. To determine concentrations residue of hexachlorobenzene in vegetables, fruits and in rice. 2. To estimate a dietary intake of hexachlorobenzene with some vegetables, fruits and rice by a general population in Mongolia 3. To estimate the oral Reference Dose of hexachlorobenzene as units of mg/kg-day in body weight. Results: Total quantity of fungicides imported to Mongolia in 2007 was about 4.087 l. Residue of hexaclorobenzene was detected in potatoes, vegetables ranging from 0.12 to 0.16 mg/kg, in fruits 0.66 mg/kg, and in rice 0.25-mg/kg. The intake of HCBz in men was estimated at about 0.17806 mg, and in women 0.05791 mg, respectively. The oral Reference Dose of HCBz was estimated 0.0026 mg in per kilogram of body weight in Mongolian men and 0.00094 mg in per kilogram of body weight in Mongolian women per day. The intake of HCBz were estimated about at 0.17196 mg in children aged 1-3 years, 0.13954 mg in children aged 4-6 years, 0.18596 mg in children aged 7-10 years, and 0.18596 mg in children of aged 11-14 years. The oral reference Dose of HCBz was estimated about at 0.17196 mg in per kilogram of the body weight of children aged 1-3 years and 0.13954 mg in per kilogram of the body weight of children aged 4-6. Also the oral reference dose of HCBz were estimated 0.13954 mg in per kilogram of the body weight of children aged 7-10 years while 0.18596 mg in per kilogram of the body of children aged 11-14 years per day. Conclusions: 1. Hexachlorobenzene is being imported to Mongolia which eliminated or restricted the production, use, import and export. 2. Potatoes, vegetables, fruit and rice were contained residues of hexachlorobenzene. 3. The oral reference Dose of HCB was reached to liver effects dose in 0.0008 mg/kg day.