Gene Silencing Associated with SWI/SNF Complex Loss during NSCLC Development
MOLECULAR CANCER RESEARCH
Authors: Song, Shujie; Walter, Vonn; Karaca, Mehmet; Li, Ying; Bartlett, Christopher S.; Smiraglia, Dominic J.; Serber, Daniel; Sproul, Christopher D.; Plass, Christoph; Zhang, Jiren; Hayes, D. Neil; Zheng, Yanfang; Weissman, Bernard E.
Abstract
The SWI/SNF chromatin-remodeling complex regulates gene expression and alters chromatin structures in an ATP-dependent manner. Recent sequencing efforts have shown mutations in BRG1 (SMARCA4), one of two mutually exclusive ATPase subunits in the complex, in a significant number of human lung tumor cell lines and primary non-small cell lung carcinoma (NSCLC) clinical specimens. To determine how BRG1 loss fuels tumor progression in NSCLC, molecular profiling was performed after restoration of BRG1 expression or treatment with a histone deacetylase inhibitor or a DNA methyltransferase (DNMT) inhibitor in a BRG1-deficient NSCLC cells. Importantly, validation studies from multiple cell lines revealed that BRG1 reexpression led to substantial changes in the expression of CDH1, CDH3, EHF, and RRAD that commonly undergo silencing by other epigenetic mechanisms during NSCLC development. Furthermore, treatment with DNMT inhibitors did not restore expression of these transcripts, indicating that this common mechanism of gene silencing did not account for their loss of expression. Collectively, BRG1 loss is an important mechanism for the epigenetic silencing of target genes during NSCLC development. Implications: Inactivation of the SWI/SNF complex provides a novel mechanism to induce gene silencing during NSCLC development. (C) 2014 AACR.
Identification of Putative Immunologic Targets for Colon Cancer Prevention Based on Conserved Gene Upregulation from Preinvasive to Malignant Lesions
CANCER PREVENTION RESEARCH
Authors: Broussard, Elizabeth K.; Kim, Rachel; Wiley, Jesse C.; Marquez, Juan Pablo; Annis, James E.; Pritchard, David; Disis, Mary L.
Abstract
The length of time required for preinvasive adenoma to progress to carcinoma, the immunogenicity of colorectal cancer (CRC), and the identification of high-risk populations make development and testing of a prophylactic vaccine for the prevention of CRC possible. We hypothesized that genes upregulated in adenoma relative to normal tissue, which maintained increased expression in CRC, would encode proteins suitable as putative targets for immunoprevention. We evaluated existing adenoma and CRC microarray datasets and identified 160 genes that were >= 2-fold upregulated in both adenoma and CRC relative to normal colon tissue. We further identified 23 genes that showed protein overexpression in colon adenoma and CRC based on literature review. Silencing the most highly upregulated genes, CDH3, CLDN1, KRT23, and MMP7, in adenoma and CRC cell lines resulted in a significant decrease in viability (P < 0.0001) and proliferation (P < 0.0001) as compared to controls and an increase in cellular apoptosis (P < 0.05 for CDH3, KRT23). Results were duplicated across cell lines representing microsatellite instability, CpG island methylator, and chromosomal instability phenotypes, suggesting immunologic elimination of cells expressing these proteins could impact the progression of all CRC phenotypes. To determine whether these proteins were immunogens, we interrogated sera from early stage CRC patients and controls and found significantly elevated CDH3 (P = 0.006), KRT23 (P = 0.0007), and MMP7 (P < 0.0001) serum immunoglobulin G in cases as compared to controls. These data show a high throughput approach to the identification of biologically relevant putative immunologic targets for CRC and identified three candidates suitable for vaccine development. (c) 2013 AACR.