Ellagic Acid Resensitizes Gemcitabine-Resistant Bladder Cancer Cells by Inhibiting Epithelial-Mesenchymal Transition and Gemcitabine Transporters.

Ying-Si Wu,Cheng-Ping Yu,Hong-Wei Gao,Cheng-Shuo Huang,Chun-Jung Cho,Dah-Shyong Yu,Jar-Yi Ho,Chia-Lun Wu

doi:10.3390/cancers13092032

Ying-Si Wu, Cheng-Ping Yu + Show 6 more

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https://doi.org/10.3390/cancers13092032

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Abstract

Simple SummaryChemoresistance of bladder cancer has become a major obstacle to clinical treatment, especially in first-line treatments involving gemcitabine (GCB). Epithelial-mesenchymal transition (EMT) is highly correlated with GCB resistance but less correlated with GCB metabolism and less reported as a novel therapeutic strategy. Our findings indicated that EMT-related GCB resistance occurs through the TGF-β/Smad signaling pathways and involves repressed expression of the GCB transporters hCNT1 and hENT1. Ellagic acid (EA) combined with GCB intensified the chemosensitivity of GCB in resistant cells by repressing Smad2, Smad3, and Smad4 expression and rescuing hCNT1 and hENT transcription. These data suggest that EA is a good adjuvant agent for blocking TGF-β/Smad signaling-related GCB resistance in bladder cancer.Gemcitabine (GCB) resistance is a major issue in bladder cancer chemoresistance, but its underlying mechanism has not been determined. Epithelial-mesenchymal transition (EMT) has been shown to be comprehensively involved in GCB resistance in several other cancer types, but the direct connection between EMT and GCB remains unclear. This study was designed to elucidate the mechanism of EMT-related GCB resistance in bladder cancer and identify a potential phytochemical to modulate drug sensitivity. The biological effects of ellagic acid (EA) or its combined effects with GCB were compared in GCB-resistant cells and the GCB-sensitive line in terms of cell viability, apoptosis, motility, and in vivo tumorigenicity. The molecular regulation of EMT-related GCB resistance was evaluated at both the mRNA and protein expression levels. Our results indicated that TGF-β/Smad induced the overactivation of EMT in GCB-resistant cells and reduced the expression of GCB influx transporters (hCNT1 and hENT1). Moreover, ellagic acid (EA) inhibited the TGF-β signaling pathway both in vitro and in vivo by reducing Smad2, Smad3, and Smad4 expression and thereby resensitized GCB sensitivity. In conclusion, our results demonstrate that TGF-β/Smad-induced EMT contributes to GCB resistance in bladder cancer by reducing GCB influx and also elucidate the novel mechanisms of EA-mediated inhibition of TGF-β/Smad-induced EMT to overcome GCB resistance. Our study warrants further investigation of EA as an effective therapeutic adjuvant agent for overcoming GCB resistance in bladder cancer.

Highlights

Bladder cancer is the seventh most common cancer worldwide and the second most common urological malignancy
ellagic acid (EA) or EA combined with GCB obviously reduced the intratumoral expression of Smad 2 and Smad 3, reduced angiogenesis within tumor burden and had inhibitory effects on vascular endothelial growth factor-A (VEGFA), a TGFβ 7sigof 14 naling transactivated proangiogenic factor (Figure 5G, Supplementary Figure S7A)
EA or EA combined with GCB obviously reduced the intratuGCB resistance is a major type of chemotherapeutic resistance in bladder cancer, and moral expression of Smad 2 and Smad 3, reduced angiogenesis within tumor burden and the Epithelial-mesenchymal transition (EMT) process has been shown to be comprehensively involved in GCB resistance in had inhibitory effects on vascular endothelial growth factor-A (VEGFA), a TGFβ signalseveral cancer types [21,23,24,25], but it has been less addressed in bladder cancer

Summary

Introduction

Bladder cancer is the seventh most common cancer worldwide and the second most common urological malignancy. The use of phytochemicals participating in anti-DNA replication and overcoming resistance to nucleoside analogs should be a proper alternative treatment strategy to overcome GCB resistance in bladder cancer. Ellagic acid (EA), a polyphenolic compound found as a naturally occurring hydrolysis product of ellagitannins in pomegranates, berries, grapes, green tea, and nuts, was selected as a study candidate for this study because of its comprehensive involvement in several antitumor and anti-inflammatory processes [8] and because of its potential to enhance the sensitivity of nucleoside analogs, as shown in several virological [9,10,11,12] and cancer treatment studies [13]

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