ING3 as a novel regulator of pancreatic cancer growth and aggressiveness.

Abstract

304 Background: Recent studies demonstrate that chromatin regulation by posttranslational means, such as histone methylation or acetylation, is an essential control mechanism in tumorigenesis and tumor progression. Accumulative findings support the notion that pancreatic cancer tumorigenesis is not only governed by genetic alterations but also aberrant epigenetic regulation. The aim of the present study was to identify and assess the role of chromatin regulators in pancreatic cancer. Methods: The gene expression profile of chromatin regulators was assessed using gene expression microarray analysis in pancreatic cancer and uninvolved human tissues. Validation of microarray findings was performed by qRT-PCR in two extended cohorts of patients and by immunohistochemistry in pancreas tumor tissue microarrays. PANC-1, MIA Paca-2, Capan-2, HPAF-II and AsPC-1 cell lines were used for in vitro assays. Efficiency of knockdown experiments, performed by RNAi interference assays and shRNA-expressing lentiviral vectors, was evidenced by qRT-PCR and Western Blot Analysis. Cell proliferation, invasion and colony formation assays were conducted in genetically modified cells. The significance of variability between the results from each group and corresponding control was determined by unpaired t-test. Results: Differential expression analysis of chromatin regulators in pancreatic cancer versus uninvolved tissues demonstrates that 27 epigenetic molecules are significantly de-regulated (>1.5 fold, P<0.05). By hierarchical clustering, the samples are classified into two major groups that reflect the normal and cancer state. The decreased expression of inhibitor of growth family member 3 (ING3), a component of the NuA4 histone acetyl-transferase complex, was further validated by qRT-PCR and immunohistochemistry analysis in tumor tissues. Transient or stable silencing of ING3 caused significant increase of viability, proliferation, colony formation and invasion in several pancreatic cell lines. Conclusions: Our data show that human pancreatic cancer is characterized by loss of ING3 expression and we defined a potential role of the latter in pancreatic cancer cell growth and invasion.