Identifying Novel Genes Critical To Invasion In Head And Neck Squamous Cell Carcinoma

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Oral squamous cell carcinomas (OSCC) have a poor patient prognosis, which is attributed to their invasive nature. Our goal was to identify specific genes that are important in OSCC invasion utilizing genome-wide expression data generated from HNSCC patient tumor samples of varying degrees of invasiveness. Invasion was assessed using the histological parameter pattern of invasion (POI), which describes the manner in which tumor cells infiltrate the normal tissue at the tumor-host interface. POI was used to categorize tumor resections into five types (1-5), type 5 being the most invasive with a “widely dispersed pattern of tumor infiltrate” and correlated significantly with the appearance of local recurrence and decreased overall survival of the patients after surgery. Global gene expression data was acquired from analysis of the surgical resections from 9 OSCC patient samples collected at Montefiore Medical Center between 2001 and 2008. Tumor cell-enriched cores from FFPE samples were used to generate global gene expression data using the Illumina® WG-DASL array to compare gene expression in four tumors that were WPOI type 5 and five tumors that were WPOI type 3. RNA extracted from flash-frozen tumor samples following surgical resection from the same patients was used to obtain global gene expression data using the Illumina® HumanHT-12 v4 Expression BeadChip. Candidate genes were assessed using in vitro invasion assays following siRNA knockdown of specific gene expression using siGENOME smart pools from Dharmacon. When both gene expression datasets were analyzed, we identified 104 genes that were overexpressed at least 1.5-fold in the WPOI type 5 tumors compared to the less invasive WPOI type 3 tumors. Fifty genes were initially tested based on functional criteria. In our initial screen, 16 of these genes showed a significant reduction in tumor cell invasion when expression was knocked down by siRNA in an OSCC cell line. The top gene from the screen, APOE, is now being further examined to determine a mechanistic explanation for its effect on invasion. Downstream signaling of APOE receptors and how this may interact with invasion are currently being assessed. This initial screen of global gene expression data in combination with pattern of invasion has revealed APOE as a novel gene that may play a critical role in OSCC invasion. Citation Format: Sangeeta K. Jayakar, Olivier D. Loudig, Margaret Brandwein-Gensler, Ryung S. Kim, Michael B. Prystowsky, Jeffrey E. Segall, Thomas J. Belbin. Identifying novel genes critical to invasion in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3158. doi:10.1158/1538-7445.AM2014-3158