Abstract 665: Promoter DNA methylation is associated with metastatic properties of pancreatic cancer.
Authors: Lin Huey-Jen L. , Peng Zhengang , Fisher Amanda , Weber Jennifer C. , Li Ying-Wei 
Published: August 2014

The inability of early detection of pancreatic tumors is largely due to a lack of biomarkers and a poor understanding of molecular mechanisms conferring carcinogenic dissemination. Recent evidence has indicated that various neoplastic phenotypes are governed by epigenomic alterations (DNA methylation or histone modifications) which confer reversible effects without changing nucleotide sequences themselves.

During the past years, we have compared DNA methylation profiles between the parental pancreatic cells FG and its isogenic variant L3.6pl that gained remarkable migratory and invasive properties in culture (33- and 20-fold increase) and in mice (Neoplasia; 1(1); page 50, 1999). DNA methylation profiling was conducted by a method known as MBD-isolated Genome Sequencing which captures methylated DNA via a methyl-CpG binding protein followed by genome-wide DNA sequencing using Illumina sequencer (GAII). Reads were then aligned to a reference human genome browser (HG18) whereby the abundance of read coverage was calculated and indicative of methylation levels occurring at given loci. These methylation profiles were used to generate a list of candidate genes that displayed higher levels of DNA methylation within the L3.6 compared to FG cell lines. We hypothesize that these hypermethylated loci may be correlated to the enhanced invasive properties associated with not only L3.6pl, but also other metastatic pancreatic carcinomas in general. Among these candidates, COL7A1 was of interest. It encodes for a basement membrane protein that is known to be a type VII collagen and is the main component of anchoring fibrils that are involved in cellular processes such as cell adhesion and motility. Silenced expression of COL7A1 by DNA methylation has been shown by two lines of evidence generated from our laboratory. (1) CpG islands situated within COL7A1 promoter displayed prominent promote activity. (2) The induction of methylation by an in vitro method impaired its transcriptional activity. To determine if other epigenetic alterations such as histone modifications led to a similar reduction of COL7A1 expression, a histone deacetylase inhibitor, Trichostatin A, was introduced. It was found that this agent was unable to restore similar expression levels of COL7A1 compared to treatment of de-methylation agent (5-azacytidine). These data suggest that DNA methylation is an important mechanism governing COL7A1 expression We further suggest that this aberration may serve as a general phenomenon, as COL7A1 was concordantly methylated in other metastatic pancreatic cell lines including ASPC-1, Capan-2, and Miacapa-2.

Taken together, we hypothesize that promoter methylation leads to a reduced COL7A1 expression followed by an induction of metastasis in pancreatic adenocarcinoma. Thus, COL7A1 promoter could potentially serve as a diagnostic marker and a therapeutic target for impeding metastasis.

Citation Format: Huey-Jen L. Lin, Zhengang Peng, Amanda Fisher, Jennifer C. Weber, Ying-Wei Li. Promoter DNA methylation is associated with metastatic properties of pancreatic cancer. [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 665. doi:10.1158/1538-7445.AM2013-665