Abstract 1003: The inhibitory role of quercetin-induced Dickkopf-1 on the growth of 4T1 breast cancer cell line
Authors: Kim Hae-Sung , Sinha Nidhi , Sharma Ashish R , Ryu Byung-Yoon , Kim Lee-Su , Hong Mi-Gyeong , Kang Hee Joon , Lee Sang-Soo , Nam Ju-Suk 
Published: June 2012

Abstract
Introduction: The highly conserved Wnt/β-catenin canonical signaling pathway plays a crucial role in the normal development and tumor development. Although β-catenin is stabilized in about 50% of breast cancer, mutations in the Wnt/β-catenin signaling pathway are relatively rare. Dickkopf-1 (Dkk-1) was first identified as a secreted inhibitor of the canonical Wnt/β-catenin signaling pathway and increased Dkk-1 results in the inhibition of β-catenin dependent target gene expression. In this study, we investigated the effect of quercetin, a flavonoid, to regulate 4T1 breast cancer cells by inducing the expression of Dkk-1.
Methods: Using a MTT assay, the inhibition of cell proliferation by quercetin (0-40μM) on 4T1 cancer cells was measured. Effects of quercetin (20μM) on Dkk-1 mRNA expression were detected by quantitative real-time RT-PCR. To test the regulation of Wnt/β-catenin signaling activity, 4T1 cells were transiently transfected with β-catenin repoter gene (Topflash). After treatment of quercetin(20μM) for 48 hours, transcriptional activity of β-catenin was estimated by luciferase assay. The protein stability of β-catenin was analyzed by Western blotting. To confirm the inhibitory effect of Dkk-1, MTT assay was performed after treatment of human-recombinant Dkk-1 (h-r-Dkk-1) on 4T1 cells.
Results: The growth of 4T1 cells, treated with the indicated amount of quercetin (0-40μM) for 48 hours, were reduced in a dose-dependent manner (p=0.0002). Real-time RT-PCR revealed that the expression of Dkk-1 mRNA was significantly increased by about five-fold at 20μM of quercetin. Within 48 hours of treatment, a 20μM concentration of quercetin reduced β-catenin transcriptional activity by approximately 2-fold (p=0.0037). Protein stability of β-catenin was down-regulated by quercetin (20μM) in a time-dependent manner. Also the addition of h-r-Dkk-1 to 4T1 cell line showed a similar role in the inhibition of cell proliferation (p=0.0320).
Conclusion: The present study investigated the possible existence of autocrine Wnt/β-catenin signaling for regulating breast cancer cell growth. quercetin showed a potent inhibitory role in the Wnt/β-catenin signaling activity as well as the growth of 4T1 breast cancer cells. Moreover, Dkk-1, as a negative regulator for Wnt/β-catenin signaling, was confirmed to be induced by quercetin. Therefore the present study suggest that Wnt/β-catenin signaling may be a promising target pathway for innovative treatment strategies of breast cancer.
Aknowledgement : This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-000-1266).
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1003. doi:10.1158/1538-7445.AM2011-1003