BRCA1 modulates sensitivity to 5F-203 by regulating xenobiotic stress-inducible protein levels and EROD activity

Kang, Hyo Jin; Kim, Hee Jeong; Kwon, Sang Hoon; Kang, Brian DongHoon; Eling, Thomas E.; Lee, Sang‐Han; Bae, Insoo

doi:10.1007/s00280-007-0657-7

Cited by 5 publications

(8 citation statements)

References 15 publications

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“…MCF-10A cells were transfected with a DNA vector containing shRNA (pSuper-control vs. pSuper-BRCA1) for 72 h and treated with various doses of BaP (0, 1, 2.5, 5μM) for 24 h. Then, cells were washed and incubated with reaction buffers (5μM of 7-ethoxyresorufin and 10μM of dicumarol) for 30 min. Fluorescence was measured every 10 min for 60 min at 37°C with an Ultra 384 fluorometer (Tecan, Switzerland) using 535 nm excitation and 590 nm emission filters as previously described (Kang et al , 2008b). …”

Section: Methodsmentioning

confidence: 99%

Detoxification: A Novel Function of BRCA1 in Tumor Suppression?

Kang

Hong

Kim

et al. 2011

Toxicological Sciences

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Our studies found that BRCA1 levels negatively correlate with DNA adducts induced by Benzo(a)pyrene (BaP). Pulse-chase experiments showed that the increase in BaP-induced DNA adducts in BRCA1 knockdown cells may not be associated with BRCA1’s function in nucleotide excision repair activity; rather, it may be associated with its function in modulating transcriptional regulation. BRCA1 knockdown in MCF-10A cells significantly attenuated the induction of CYP1A1 following BaP treatment indicating that the increase in BaP-induced adducts in BRCA1 knockdown cells is not CYP1A1 dependent. However, our study shows that BRCA1 defective cells may still be able to biotransform BaP by regulating other CYP enzymes, including CYP1B1. Knockdown of BRCA1 also severely affected the expression levels of two types of uridine diphosphate glucorunyltransferase (UGT1A1 and UGT1A9) and NRF2. Both UGTs are known as BaP-specific detoxification enzymes, and NRF2 is a master regulator of antioxidant and detoxification genes. Thus, we concluded that the increased amount of BaP-induced DNA adducts in BRCA1 knockdown cells is strongly associated with its loss of functional detoxification. Chromatin immunoprecipitation assay revealed that BRCA1 is recruited to the promoter/enhancer sequences of UGT1A1, UGT1A9, and NRF2. Regulation of UGT1A1 and UGT1A9 expression showed that the induction of DNA adducts by BaP is directly affected by their expression levels. Finally, overexpression of UGTs, NRF2, or ARNT significantly decreased the amount of BaP-induced adducts in BRCA1-deficient cells. Overall, our results suggest that BRCA1 protects cells by reducing the amount of BaP-induced DNA adducts possibly via transcriptional activation of detoxification gene expression.

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Section: Methodsmentioning

confidence: 99%

Detoxification: A Novel Function of BRCA1 in Tumor Suppression?

Kang

Hong

Kim

et al. 2011

Toxicological Sciences

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“…To determine whether the mRNA induction of CYP1A1 by TCDD or BaP led to increasing enzyme activity, we measured its activity (EROD activity) in cells treated with different dose of TCDD or BaP (Kang et al, 2008(b)). We found that either TCDD or BaP increased the EROD activity in a dose-dependent manner (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…BRCA1 has been demonstrated to have function in DNA damage repair of double strand breaks, ubiquitination and transcriptional regulation (Starita and Parvin, 2003). Our group has previously reported that BRCA1 modulates a range of expression of genes induced by various environmental stressors including xenobiotics or oxidative stressors (Bae et al, 2004; Kang et al, 2006(a); Kang et al, 2006(b); Kang et al, 2008(a); Kang et al, 2008(b)). In this study, we demonstrated increased accumulation of the BaP-DNA adducts in the BRCA1-siRNA treated cells, which implicates that loss of BRCA1 or its expression may confer sensitivity to environmental stresses such as BaP.…”

Section: Discussionmentioning

confidence: 99%

“…Briefly, HPDE6 cells treated with various doses of BaP and TCDD for 24 hr, and then cells were washed twice with PBS and incubated with reaction buffers, containing 5 μM of 7-ethoxyresorufin and 10 μM of dicumarol for 30 min at 37 °C. Fluorescence was measured every 10 min for 60 min at 37 °C with an Ultra 384 fluorometry (Tecan, Männedorf, Switzerland) using 535 nm excitation and 590 nm emission filter as previously described (Burke and Mayer, 1974; Kang et al, 2008(b)). …”

Section: Methodsmentioning

confidence: 99%

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A novel in vitro pancreatic carcinogenesis model

et al. 2011

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Environmental factors (e.g., BaP) have been pointed out as one of the etiologies of pancreatic cancer. However, very limited experimental assays are available to identify pancreatic specific environmental mutagens or susceptibility genes. In this study, we have developed a simple in vitro cell culture model system that can be used to study the molecular and biochemical aspects of carcinogenesis in a near-normal immortalized pancreatic ductal epithelial cell lines. In order to demonstrate that xenobiotic stress response is intact in these cells we employed standard molecular biology techniques. For examples, luciferase reporter and/or real-time quantitative PCR assays were used to determine stress-induced CYP1A1 and CYP1B1 gene expression. Western blotting and immunocytochemistry assays were used to demonstrate that TCDD or BaP could activate AhR signaling. For exploring the carcinogenesis mechanism, we incubated cells with [3H]BaP and determined BaP-DNA binding activity by measuring its radioactivity. BaP-DNA adduct formation was further confirmed by [32P]-postlabeling assay. Finally, we demonstrated the effects of endogenous AhR or BRCA1 in BaP-DNA adduct accumulation in our cell system: As results, no apparent BaP-DNA adduct accumulation by [32P]-postlabeling assay was found in either control-siRNA or AhR-siRNA pretreated cells. On the other hand, a significant increase of BaP-DNA adduct accumulation was found in BRCA1 knockdown cells. In conclusion, we suggest that this in vitro model may provide the feasibility for future studies on the molecular basis of pancreatic ductal cell carcinogenesis caused by dietary mutagens.

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“…Although major function of BRCA1 is known as a classical tumor suppressor gene, we have demonstrated that BRCA1 regulates transcription of phase I and II enzymes upon exposure to various exogenous stresses (Kang et al, 2006(Kang et al, , 2008a(Kang et al, and 2008b. BRCA1 can stimulate antioxidant gene expression and modulate intracellular reactive oxygen species (ROS) levels through enhancing the activity of the antioxidant response transcription factor, NRF2 (Bae et al, 2004;Kang et al, 2012).…”

Section: Introductionmentioning

confidence: 99%