Tetradecylthioacetic acid inhibits proliferation of human SW620 colon cancer cells - gene expression profiling implies endoplasmic reticulum stress

Abstract

BackgroundPrevious reports have shown an antiproliferative effect of the synthetic, 3-thia fatty acid tetradecylthioacetic acid (TTA) on different cancer cells in vitro and in vivo. The mechanisms behind the observed effects are poorly understood. We therefore wanted to explore the molecular mechanisms involved in TTA-induced growth inhibition of the human colon cancer cell line SW620 by gene expression profiling.MethodsAn antiproliferative effect of TTA on SW620 cells in vitro was displayed in real time using the xCELLigence System (Roche). Affymetrix gene expression profiling was performed to elucidate the molecular mechanisms behind the antiproliferative effect of TTA. Changes in gene expression were verified at protein level by western blotting.ResultsTTA reduced SW620 cell growth, measured as baseline cell index, by 35% and 55% after 48 h and 72 h, respectively. We show for the first time that TTA induces an endoplasmic reticulum (ER) stress response in cancer cells. Gene expression analysis revealed changes related to ER stress and unfolded protein response (UPR). This was verified at protein level by phosphorylation of eukaryote translation initiation factor 2 alpha (eIF2α) and downstream up-regulation of activating transcription factor 4 (ATF4). Transcripts for positive and negative cell cycle regulators were down- and up-regulated, respectively. This, together with a down-regulation of Cyclin D1 at protein level, indicates inhibition of cell cycle progression. TTA also affected transcripts involved in calcium homeostasis. Moreover, mRNA and protein level of the ER stress inducible C/EBP-homologous protein (CHOP), Tribbles homolog 3 (Drosophila) (TRIB3) and CCAAT/enhancer binding protein beta (C/EBPβ) were enhanced, and the C/EBPβ LIP/LAP ratio was significantly increased. These results indicate prolonged ER stress and a possible link to induction of cell death.ConclusionWe find that TTA-induced growth inhibition of SW620 cells seems to be mediated through induction of ER stress and activation of the UPR pathway.

New frontiers in the treatment of colorectal cancer: Autophagy and the unfolded protein response as promising targets

“…Like DHA, tetradecylthioacetic acid induces growth inhibition, which is mediated via ER stress and the UPR and involves EIF2A phosphorylation and downstream regulation of ATF4. 279 Riproximin (RPX) is a component of a plant extract and cytotoxic to breast and colorectal cancer cells by targeting type II ribosome inactivating proteins with high selectivity in certain tumor cell lines. This increases the expression of the UPR genes ATF6 and ERN1 .…”

Developmental roles of tribbles protein family members

“…Thus, their role as either oncogene or tumor suppressor of AML remains unresolved. Trib3 mediates the tumor suppressing effects homocystein in endothelial cell model (Zou et al, 2009), cannabinoid in hepatocellular carcinomas (Vara et al, 2011), tetradecylthioacetic acid (TTA) in colon cancer cells (Lundemo et al, 2011), and dehydroxymethylepoxyquinomicin (DHMEQ) in liver cancer cells (Lampiasi et al, 2009). …”

Tribbles Pseudokinases in Colorectal Cancer

“…Another study showed that transcript and protein levels of TRIB3 were upregulated in SW620 cells treated with the bioactive chemical modified fatty acid (FA) analog saturated 3-thia FA tetradecylthioacetic acid (TTA), compared to non-treated cells [ 98 ]. TTA not only inhibited the growth of colon cancer cells, but also induced the expression of several other genes involved in endoplasmic reticulum (ER) stress and unfolded protein response (UPR), such as CHOP and C/EBPβ, whereas Cyclin D1 was down-regulated [ 98 ].…”

“…Another study showed that transcript and protein levels of TRIB3 were upregulated in SW620 cells treated with the bioactive chemical modified fatty acid (FA) analog saturated 3-thia FA tetradecylthioacetic acid (TTA), compared to non-treated cells [ 98 ]. TTA not only inhibited the growth of colon cancer cells, but also induced the expression of several other genes involved in endoplasmic reticulum (ER) stress and unfolded protein response (UPR), such as CHOP and C/EBPβ, whereas Cyclin D1 was down-regulated [ 98 ]. After treating HCT116 cells with the photosensitizer hypericin and photodynamic therapy (HY-PDT) [ 99 ], at the higher concentration range, TRIB3 protein levels were induced, along with induction of CHOP, activation of the autophagy signal and cell death [ 85 ].…”