TY - JOUR
T1 - Chronic exposure to arsenic, estrogen, and their combination causes increased growth and transformation in human prostate epithelial cells potentially by hypermethylation-mediated silencing of MLH1
AU - Treas, Justin
AU - Tyagi, Tulika
AU - Singh, Kamaleshwar P.
PY - 2013/11
Y1 - 2013/11
N2 - BACKGROUND. Chronic exposure to arsenic and estrogen is associated with risk of prostate cancer, but their mechanism is not fully understood. Additionally, the carcinogenic effects of their co-exposure are not known. Therefore, the objective of this study was to evaluate the effects of chronic exposure to arsenic, estrogen, and their combination, on cell growth and transformation, and identify the mechanism behind these effects. METHODS. RWPE-1 human prostate epithelial cells were chronically exposed to arsenic and estrogen alone and in combination. Cell growth was measured by cell count and cell cycle, whereas cell transformation was evaluated by colony formation assay. Gene expression was measured by quantitative real-time PCR and confirmed at protein level by Western blot analysis. MLH1 promoter methylation was determined by pyrosequencing method. RESULTS. Exposure to arsenic, estrogen, and their combinations increases cell growth and transformation in RWPE-1 cells. Increased expression of Cyclin D1 and Bcl2, whereas decreased expression of mismatch repair genes MSH4, MSH6, and MLH1 was also observed. Hypermethylation of MLH1 promoter further suggested the epigenetic inactivation of MLH1 expression in arsenic and estrogen treated cells. Arsenic and estrogen combination caused greater changes than their individual treatments. CONCLUSIONS. Findings of this study for the first time suggest that arsenic and estrogen exposures cause increased cell growth and survival potentially through epigenetic inactivation of MLH1 resulting in decreased MLH1-mediated apoptotic response, and consequently increased cellular transformation.
AB - BACKGROUND. Chronic exposure to arsenic and estrogen is associated with risk of prostate cancer, but their mechanism is not fully understood. Additionally, the carcinogenic effects of their co-exposure are not known. Therefore, the objective of this study was to evaluate the effects of chronic exposure to arsenic, estrogen, and their combination, on cell growth and transformation, and identify the mechanism behind these effects. METHODS. RWPE-1 human prostate epithelial cells were chronically exposed to arsenic and estrogen alone and in combination. Cell growth was measured by cell count and cell cycle, whereas cell transformation was evaluated by colony formation assay. Gene expression was measured by quantitative real-time PCR and confirmed at protein level by Western blot analysis. MLH1 promoter methylation was determined by pyrosequencing method. RESULTS. Exposure to arsenic, estrogen, and their combinations increases cell growth and transformation in RWPE-1 cells. Increased expression of Cyclin D1 and Bcl2, whereas decreased expression of mismatch repair genes MSH4, MSH6, and MLH1 was also observed. Hypermethylation of MLH1 promoter further suggested the epigenetic inactivation of MLH1 expression in arsenic and estrogen treated cells. Arsenic and estrogen combination caused greater changes than their individual treatments. CONCLUSIONS. Findings of this study for the first time suggest that arsenic and estrogen exposures cause increased cell growth and survival potentially through epigenetic inactivation of MLH1 resulting in decreased MLH1-mediated apoptotic response, and consequently increased cellular transformation.
KW - MLH1 hypermethylation
KW - arsenic
KW - epigenetics
KW - estrogen
KW - prostate cancer
UR - http://www.scopus.com/inward/record.url?scp=84884901780&partnerID=8YFLogxK
U2 - 10.1002/pros.22701
DO - 10.1002/pros.22701
M3 - Article
C2 - 23804311
AN - SCOPUS:84884901780
SN - 0270-4137
VL - 73
SP - 1660
EP - 1672
JO - Prostate
JF - Prostate
IS - 15
ER -