Gene expression profiling study by RNA-seq in colorectal cancer

The objective of this study is to identify a prognostic signature in colorectal cancer (CRC) patients with diverse progression and heterogeneity of CRCs. We generated RNA-seq data of 54 samples (normal colon, primary CRC, and liver metastasis) from 18 CRC patients and, from the RNA-seq data, identified significant genes associated with aggressiveness of CRC. Through diverse statistical methods including generalized linear model likelihood ratio test, two significantly activated regulators were identified. In the validation cohorts, two activated regulators were independent risk factors and potential chemotherapy-sensitive agenets in colorectal cancers. Overall design: RNA-seq data of 54 samples (normal colon, primary CRC, and liver metastasis) were generated from 18 CRC patients. Total RNA was isolated by RNeasy Mini Kit (Qiagen, CA, USA), according to the manufacturer's protocol. The quality and integrity of the RNA were confirmed by agarose gel electrophoresis and ethidium bromide staining, followed by visual examination under ultraviolet light. Sequencing library was prepared using TruSeq RNA Sample Preparation kit v2 (Illumina, CA, USA) according to the manufacturer's protocols. Briefly, mRNA was purified from total RNA using poly-T oligo-attached magnetic beads, fragmented, and converted into cDNAs. Then, adapters were ligated and the fragments were amplified on a PCR. Sequencing was performed in paired end reads (2x100 bp) using Hiseq-2000 (Illumina).