Abstract 4093: Growth factors regulated by the aryl hydrocarbon receptor in highly metastatic head and neck squamous cell carcinoma cell lines.
Authors: John Kaarthik , Hughes Jarod , Lahoti Tejas , Kelly Wagner , Gary Perdew 
Published: August 2014

Abstract
The aryl hydrocarbon receptor (AHR), a ligand activated transcription factor, is implicated in mediating pleotropic cellular effects in response to a variety of AHR ligands. Recent evidence has implicated the AHR in tumor initiation, promotion and progression as well.
Enhanced AHR expression has been associated with dysregulated cellular proliferation, enhanced cell motility and loss of cell-cell contact. Previous studies from this laboratory have revealed considerable constitutive and ligand-inducible AHR transcriptional activity in head and neck squamous cell carcinoma cell lines (HNSCC). Subsequently, antagonism of AHR activity was found to greatly attenuate the highly metastatic and proliferative phenotype of these cells, thereby suggesting that the AHR plays a pivotal role in dictating the ‘aggressive’ phenotype of these cells. Hence, this study sought to use a whole genome expression profiling based approach to identify putative novel targets of the AHR associated with cancer cell survival and tumor invasiveness. Given previous documented evidence, from other studies in the literature, of the involvement of growth factors in dictating the aggressive phenotype of various cancers, this study sought to focus specifically on the growth factor targets regulated by AHR. Additionally, enhanced growth factor expression, along with high inflammatory cytokine expression, has been found to play a prominent role in dictating tumor cell malignancy. Given previous evidence from our laboratory of high inflammatory cytokine expression (IL1B, IL6) in HNSCC cell lines, the expression of growth factors was also monitored in the presence of an inflammatory signal (IL1B) and an AHR agonist (TCDD). Three growth factor targets were considered; amphiregulin (AREG), epiregulin (EREG) and platelet-derived growth factor A (PDGFA) based on expression profiling and from previous studies. Quantitative PCR analysis revealed an attenuation of basal and/or induced gene expression levels of these growth factors following AHR antagonism, either by AHR antagonist treatment or by siRNA mediated AHR knock down. ELISA analysis revealed an attenuation of both basal and induced protein levels of the growth factors examined in these cell lines. In silico analysis revealed these growth factors to possess dioxin-like response elements in regions upstream of their promoter. Two other AHR ligands, 6-formylindolo[3,2-b]carbazole and benzo(a)pyrene also exhibited induction of gene expression of the AHR growth factors examined. TCDD+IL1B in combination caused a significant increase in the expression of all growth factors examined with CH223191 causing an attenuation of their expression. In conclusion, AREG, EREG and PDGFA were identified as three key growth factor targets of the AHR associated with metastatic phenotype of head and neck cancers.
Citation Format: Kaarthik John, Jarod Hughes, Tejas Lahoti, Wagner Kelly, Perdew Gary. Growth factors regulated by the aryl hydrocarbon receptor in highly metastatic head and neck squamous cell carcinoma cell lines. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4093. doi:10.1158/1538-7445.AM2013-4093