Forkhead box O3 promotes colon cancer proliferation and drug resistance by activating MDR1 expression.

Zhuanglei Gao,Zhaoxia Li,Zhonghao Liu,Yuelin Liu

doi:10.1002/mgg3.554

Zhuanglei Gao, Zhaoxia Li + Show 2 more

Open Access

https://doi.org/10.1002/mgg3.554

Copy DOI

Abstract

BackgroundGlobally, colon cancer (CC) is the third reason of tumor‐related deaths. Previous reports indicate that Forkhead box O3 (FOXO3) is involved in the development of various tumors and may have different effects depending upon the types of tumors. Hence, this study was to examine the effects of FOXO3 on CC cells and uncover the possible mechanisms.MethodsMTT and cell count assay were applied to analyze the viability of transfected CC cells. rVista, dual luciferase reporter assay, and chromatin immunoprecipitation assay were used to identify the downstream target of FOXO3 in HCT116 cells. The mRNA and protein abundance of FOXO3 and MDR1 were determined by quantitative PCR and Western blot, respectively.ResultsForkhead box O3 stimulated the proliferation of both HCT116 and DLD1 cells. Moreover, FOXO3 overexpression inhibited doxorubicin sensitivity of HCT116 cells, while the knockout of FOXO3 by FOXO3 shRNA restored the doxorubicin sensitivity in doxorubicin‐resistant HCT116 DR cells. Next, we found that FOXO3 directly bound to the promoter of MDR1 and enhanced MDR1 expression in HCT116 cells. MDR1 overexpression enhanced the viability and doxorubicin resistance of CC cells. Besides, MDR1 overexpression plasmid significantly abrogated the decrease in cell proliferation and resistance of HCT116 cells to doxorubicin caused by FOXO3 knockout.ConclusionForkhead box O3 exhibited promotive effects on the proliferation and doxorubicin resistance in CC cells via targeting MDR1.

Highlights

Colon cancer (CC), known as colorectal or bowel cancer, is the third most frequent malignant cancer, and more than 65 percent of CC cases are found in developed countries (Kotaka et al, 2018)
HCT116 cells transfected with Forkhead box O3 (FOXO3) shRNA plasmid had lower MDR1 mRNA (Figure 3c, p < 0.05) and protein levels (Figure 3d) compared with cells transfected with empty vector
People with early‐stage CC may be cured via surgery, whereas CC patients at the advanced stages treated with the combined chemotherapy are usually not curable due to drug resistance (Ma et al, 2012; Yu et al, 2017)

Summary

| INTRODUCTION

Colon cancer (CC), known as colorectal or bowel cancer, is the third most frequent malignant cancer, and more than 65 percent of CC cases are found in developed countries (Kotaka et al, 2018). Chemotherapy is often used for clinical CC treatment, whereas drug resistance is a frequent. There are urgent needs for investigating the underlying mechanisms of CC progression and chemotherapy resistance to develop new potent therapies for CC treatment. Yang et al (2010) showed that inhibited FOXO3 expression and activation enhanced the resistance to AZD6244 treatment in cells of various tumors. Wild‐type MDR1 promoter harboring potential FOXO3 binding sites was amplified and subcloned into pGL3 basic vector (Promega, Madison, WI, USA) to construct pGL3‐MDR1‐WT‐promoter plasmid. Absorbance at 545 nm was detected using a microplate reader

| METHODS AND MATERIALS

Findings

| DISCUSSION