Identification of a novel interplaying loop of PPARγ and respective lncRNAs are involved in colorectal cancer progress.

Long noncoding RNAs (lncRNAs) as regulatory molecules play important roles in early treatment and diagnosis of cancers. Considering the role of PPARγ in colorectal cancer (CRC) as a tumor suppressor, the GEO database was used to identify candidate genes that affect the activation of PPARγ protein in CRC cell lines. Then were selected 5 genes containing PPARγ response element (PPRE) in up to 4000 bp upstream and were affected by PPARγ protein activation in HT-29 colon cancer cell line using UCSC database. Expression meta-analysis was applied to map the expression network between candidate genes and all known lncRNAs through expression correlation and lncRNAs that correlated with a greater number of candidate genes (R > 0.5, P.value < 0.001). Moreover, were selected 3 lncRNAs as lncRNAs affected by PPARγ protein activation. Next, the expression levels of candidate genes and lncRNAs were evaluated using RT-qPCR in HT-29 cell line. Results showed a significant increase (FDR <0.05) in the expression level of 5 candidate genes and lncRNAs LINC01133, MBNL1-AS, LOC100288911 after treatment with pioglitazone as PPARγ ligand compared to the untreated group in HT-29 cells. Although additional tests are needed to confirm bioinformatics predictions, it can be concluded that increased expression of PPARγ may increase genes and lncRNAs expression. In summary, this study could be suggested identifying lncRNAs affected by PPARγ activation could be a new strategy in understanding the function and activity of PPARγ in colon cancer.

Title: Involvement of unsaturated fatty acid biosynthesis in CRC progression based on in vitro and in silico studies.

Obesity is one of the risk factors concerns of colorectal cancer (CRC), the most common type of gastrointestinal cancer, due to the changing lifestyle and especially diet. There are various molecular pathways associated with obesity and the risk of CRC incidence, such as insulin resistance or elevated plasma free fatty acids, which alter the signaling pathways of intestinal epithelial cells. The aim of this study was to better understand the significance of unsaturated fatty acid biosynthesis on pathogenesis of colon cancer in obese. Based on GSE20931 dataset, obese individuals affected by CRC had higher increased gene expression than non-obese individuals. The analysis showed that in obese individuals, the 16 signaling pathway genes were activated and increased (FDR <0.05) significantly. The biosynthetic pathway of unsaturated fatty acids showed a cross-talk with the arachidonic acid metabolism pathway and the PPAR signaling pathway is influenced and regulated via these pathways. The biosynthetic pathway of unsaturated fatty acids consisting of 22 genes, were analyzed using GEO data and revealed that 4 genes (HSD17B12, TECR, FADS2, ELOVL5) from this pathway were significantly increased (FDR <0.05). These data were validated based on TCGA data (Adj.p.value <0.001). The expression level of candidate genes in HT-29 cells decreased significantly (P.value <0.01), and PPARγ expression increased under linoleic acid treatment (200 µM) compared to control cells. Moreover, in presence of linoleic acid treatment, migration, colony formation, and proliferation decreased (P.value <0.01) in presence of treatment. In summary, the Biosynthesis pathway of unsaturated fatty acids is an interesting and critical pathway in CRC.