Abstract 698: Overexpression of the Aryl Hydrocarbon Receptor Correlates with High Tumor Grade in Human Breast Invasive Carcinomas

Abstract The aryl hydrocarbon receptor (AhR) is a ligand-activated basic helix-loop-helix transcription factor which binds environmental poly aromatic hydrocarbons (PAH) and mediates their carcinogenic effects. Recent reports, including data from our laboratory implicate AhR in breast cancer development and progression independent of the receptor occupancy by PAH. In this study we investigated the potential of AhR as a stage specific marker of breast cancer. We examined the expression of AhR by immunohistochemistry in tissue microarrays (TMA) containing 192 specimens of clinically defined three stages of invasive breast cancer: node-negative (NN), node-positive (NP) and metastatic (Met) carcinoma. The TMA were obtained from the National Cancer Institute Cooperative Breast Cancer Tissue Resource [NCI-CBCTR] and were stained for AhR using high affinity antibody. The AhR staining was then scored by three evaluators, including two pathologists who were blinded to the study. Statistical analysis showed a significant correlation between the AhR expression and the carcinoma case type (NN, NP or Met) (p-value of ANOVA is < 0.0003), and although there is a significant difference of AhR expression among carcinoma case type of white women (p< 0.0017) there is no significant difference for black women (p<0.0968). There is also a strong positive correlation between the receptor expression and the tumor grade (p <0.0001). While there is no correlation with the status of estrogen or progesterone receptors (p= 0.1643 and 0.1884, respectively), there is strong correlation of high AhR expression and invasive breast carcinoma in women over 50 years old (p<0.0043). In conclusion, our findings identify the AhR as a new predictive clinical marker for metastatic breast cancer and a unique target for the design of novel selective inhibitors for therapeutic intervention of metastatic breast cancer. More importantly, the AhR overexpression identifies a subset of patients who could benefit from therapy targeting this receptor. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 698. doi:1538-7445.AM2012-698