Triggering of Endoplasmic Reticulum Stress by Tannic Acid Inhibits the Proliferation and Migration of Colorectal Cancer Cells

Abstract

Introduction: Due to the pivotal role of endoplasmic reticulum (ER) stress in cancers, interfering with its function can cause the accumulation of unfolded proteins, which ultimately leads to the activation of the unfolded protein response (UPR) signaling pathway and apoptosis. Therefore, the use of plant compounds such as tannic acid with UPR-inducing properties can be proposed as a possible treatment method for cancer. In this study, we investigated the effect of tannic acid on cell migration, colony formation, growth, and UPR-induced apoptosis in the SW48 colorectal cancer cell line.

Methods: The MTT assay was performed to investigate the cytotoxic effect of tannic acid. We performed the qPCR method to elucidate the effect of tannic acid on the expression of Bim, MMP-9, Bcl-xL, cyclin D1, CHOP, and ATF4 genes. We also used the colony formation and migration experiments to investigate the effect of this compound on the colony formation and migration ability of tumor cells. Finally, we used Hoechst staining to measure cell apoptosis.

Results: Tannic acid inhibited the cell survival, clonogenic, and migration of colon cancer cells. This compound increased the expression of ER stress-mediated UPR genes, ATF4 and CHOP. Moreover; tannic acid increased the expression of pro-apoptotic proteins like Bim, while at the same time causing a sharp decline in the expression of anti-apoptotic protein Bcl-xL. A decline in MMP-9 expression confirmed the anti-metastatic role of this compound.

Conclusion: Taken together, tannic acid can induce apoptosis via ER stress-mediated UPR pathway, and has a suppressive effect on cell viability, growth, migration, colony formation, and metastasis, suggesting it may be a potential drug in colorectal cancer treatment.

Keywords: ATF4; CHOP; Endoplasmic reticulum; Tannic acid; colorectal cancer.

Figure 1.

The Effect of Tannic Acid on Cell Survival. The SW48 cells were treated with tannic acid at indicated concentrations. After 24 h, the cell survival rate was measured by the MTT assay. The cell survival curves were plotted using GraphPad 6.1 software. Data are expressed as mean ± SD of three independent experiments. (A) MTT graph; (B) the morphology of SW48 cells; (C) the chemical structure of tannic acid

Figure 2

RT-qPCR Analysis of SW48 Cells. The SW48 cells were treated with tannic acid (IC30 and IC50 doses) for 24 h. Relative expression levels of CHOP (A), MMP-9 (B), Bcl-xL (C), Bim (D), cyclin D1 (E), and ATF4 (F) mRNAs were measured by RT-qPCR using 2^-(∆∆Ct) method and β-actin as an endogenous control. Data are presented as mean ± SD (n=3). #p< 0.05 relative to IC₃₀; *p < 0.05 relative to blank control. TA, tannic acid

Figure 3

The Effect of Tannic Acid on Colorectal Cancer Cell Migration. Monolayer of SW48 cells were treated with IC30 and IC50 doses of tannic acid. The migration of SW48 cells was quantified by measuring wound closure areas at 0, 24, 48, 72, and 96 h. Data were representative of three independent experiments. TA, tannic acid

Figure 4

Effect of Tannic Acid on Colony Formation in SW48 Cell. Cells were treated with tannic acid for 24 h. Next, the cell colonies were stained with crystal violet and the number of colonies was observed after 7 days. TA, tannic acid

Figure 5

Morphologic changes of SW48 cells treated with tannic acid for 24 h. Representative images of cells treated with tannic acid after Hoechst 33342 staining. The apoptotic cells showed condensed nuclei or apoptotic bodies (indicated by arrows). TA, tannic acid