Requirement of Aryl Hydrocarbon Receptor Overexpression for CYP1B1 Up-Regulation and Cell Growth in Human Lung Adenocarcinomas

Abstract

Purpose: CYP1B1and CYP1A1expression is up-regulated by activation of the aryl hydrocarbon receptor (AhR) through binding of ligands such as cigarette smoke components. We examined the association between AhR, CYP1B1, and CYP1A1expression in noninvasive bronchioloalveolar carcinomas (BAC) and lung adenocarcinomas and investigated the effects of AhR overexpression on cell physiology. Experimental Design: AhR, CYP1B1, and CYP1A1 expression was examined in 107 lung adenocarcinomas and 57 BAC by immunohistochemistry. AhR expression in lung adenocarcinoma H1355 cells was stably reduced by RNA interference (RNAi). AhR, CYP1B1, and CYP1A1 expression was examined using real-time reverse transcription-PCR. Cell physiology was evaluated by measuring anchorage-independent growth and intracellular reactive oxygen species. Results: Expression of AhR and CYP1A1 was associated in smoking adenocarcinoma patients, whereas expression of AhR and CYP1B1was associated regardless of smoking status. The level of CYP1B1, but not CYP1A1, was positively associated with AhR overexpression in BAC. 2,3,7,8-Tetrachlorobenzo-p-dioxin^induced CYP1A1/1B1 expression was reduced in AhR RNAi clones. In the absence of 2,3,7,8-tetrachlorobenzo-p-dioxin, CYP1B1 mRNA levels were reduced in AhR RNAi clones, whereas CYP1A1 mRNA levels were barely detectable. Furthermore, anchorageindependent growth and intracellular oxidative stress were significantly reduced in AhR RNAi cells. Conclusions: In the absence of exogenous AhR ligands (such as cigarette smoke components), AhR overexpression up-regulated the expression of CYP1B1in the early stage of lung adenocarcinoma. Elevated AhR expression in lung adenocarcinoma cells could increase intracellular oxidative stress and promote cell growth, implying that disrupting AhR expression might prevent the early development of lung adenocarcinomas.

Expression of CYP1A1 and GSTP1 in Human Brain Tumor Tissues in Pakistan

“…Similar results have also been observed in lung cancer and human endothelial cell (Shah et al, 2009;Conway et al, 2009). Whereas conflicting results for CYP1A1 expression pattern have been reported in some of other studies in different cancers (Chang et al, 2007;Masood et al, 2011;Hafeez et al, 2012). Significant upregulation of CYP1A1 was observed in different types of brain tumors in current study.…”

Aryl hydrocarbon receptor in association with RelA modulates IL-6 expression in non-smoking lung cancer

“…Both AhR and RelA are transcription factors and undergo nuclear translocation after activation. Cytosolic AhR is associated with downstream gene expression in AD (Chang et al, 2007a;Wang et al, 2009a) and therefore both cytosolic and nuclear AhR expression were measured and reported. More than 90% of lung tumor cells highly expressed cytosolic RelA, but only nuclear RelA was measured and reported in this study.…”

“…Previously, we have shown that AhR is highly expressed in lung AD as well as in bronchioalveolar carcinoma, which is considered to be carcinoma in situ (Lin et al, 2003;Su et al, 2009). Furthermore, interference with AhR expression reduces colony formation by human lung AD cells (Chang et al, 2007a). Therefore, we propose that AhRmediated biological responses may enhance the development of lung AD.…”

“…Assessment of AhR (Biomol) immunohistochemistry was done as previously described (Chang et al, 2007a). For RelA (Millipore), IL-6 (H-183, Santa Cruz Biotechnology) and CYP1A1 (H-70, Santa Cruz Biotechnology) evaluation, the immunoreactivity of the tumor or bronchiolar cells was compared with those in the adjacent stoma that showed negative immunoreactivity.…”

“…Western blotting was performed as previously published (Chang et al, 2007a) with anti-AhR (Biomol), anti-Flag (Sigma, Louis, MO, USA), anti-HSP90 (Assay Designs, Ann Arbor, MI, USA), anti-Arnt (H-172, Santa Cruz Biotechnology), anti-RelA (C-20, Santa Cruz Biotechnology), anti-p50 (Cell Signaling), anti-IkBa (C-21, Santa Cruz Biotechnology), anti-a-tubulin (Genetex, Hsinchu City, Taiwan) and anti-LaminB (C-20, Santa Cruz Biotechnology) antibodies. The protein bands were detected by chemiluminescence.…”