GSE121043
Integrated multi-omics approach reveals a role of ALDH1A1 in lipid metabolism in human colon cancer cells
Purpose: Next-generation sequencing (NGS) has revolutionized systems-based analysis of cellular pathways. An integrated systems approach was used with bioinformatics tools to understand the the role of aldehyde dehydrogenase 1A1 (ALDH1A1) in human colon cancer cells. We combined transcriptomics, proteomics and untargeted metabolomics to gain insight into the mechanisms affected by the suppression of the ALDH1A1 gene in COLO320 cells Methods: COLO 320 cells. Cellular ALDH1A1 expression was suppressed using MISSION shRNA lentiviral transduction particles containing validated ALDH1A1 shRNA in a pLKO plasmid vector. Scramble control shRNA in pLKO plasmid vector was used to generate control cells. Signal intensities were converted to individual base calls during a run using the system's Real Time Analysis (RTA) software. Primary analysis sample de-multiplexing and alignment to the human genome was performed using Illumina's CASAVA 1.8.2 software suite. The reads were trimmed for quality and aligned with the hg19 reference genome using TopHat2. The transcripts were assembled using Cufflinks. The assembled transcripts were used to estimate transcript abundance and differential gene expression using Cuffdiff. The results were visualized using R (CRAN) and CummeRbund Results: We combined transcriptomics, proteomics and untargeted metabolomics to gain insight into the mechanisms affected by the suppression of the ALDH1A1 gene in COLO320 cells. RNA-seq and proteomics analyses revealed 1747 transcripts and 336 proteins that were differentially expressed in cells in which the ALDH1A1 had been suppressed by shRNA transfection. Transcriptomics pathway analysis showed significant signaling pathways, such as Wnt/ß-catenin (p=3.47E-6), molecular mechanisms of cancer (7.41E-5) and others relevant to lipid metabolism, such as cholesterol biosynthesis I, II and III (p=1.82E-4). Proteomics pathway analysis identified oxidative phosphorylation to be the most highly significant pathway (p=5.01E-31). Pathway  analysis of the genes common to the transcriptomics and proteomics analyses revealed the asparagine biosynthesis (p=3.16E-3) and cholesterol biosynthesis the most statistically significant (p=3.36E-3). Univariate analysis of the  untargeted metabolomics dataset revealed 859 ions statistically significant. Network analysis showed alterations in pathways linked to energy and lipid metabolism, such carnitine shuttle (p=5.3E-4) and fatty acid oxidation (p=2.9E-2). A systems biology approach was used to integrate all three datasets and a total of 61 pathways were generated. A direct association between the suppression of ALDH1A1 and the Vitamin A (retinol) metabolism pathway and downregulation of retinol and the UGT2B17, UGT2A3 and PRDX6 genes was shown Conclusions: the present results confirm the role of ALDH1A1 in retinol metabolism and shows for the first time the influence of this gene on lipid metabolism pathways that may be crucial for cholesterol synthesis in human colon cancer cells. In addition, they demonstrate how an integrated systems approach using unbiased bioinformatics tools can be used to understand the interplay of cellular pathways. Overall design: An integrated systems approach was used with bioinformatics tools to understand the the role of aldehyde dehydrogenase 1A1 (ALDH1A1) in human colon cancer cells.