Walnut phenolic extracts reduce telomere length and telomerase activity in a colon cancer stem cell model

• Published in: Nutrition research and practice 2019, 13(1), , pp.58-63
• Main Authors: Shin, Phil-Kyung, Zoh, Yoonchae, Choi, Jina, Kim, Myung-Sunny, Kim, Yuri, Choi, Sang-Woon
• Format: Article
• Language: English
• Subjects: c-Myc protein; CD44 antigen; Cell culture; Cell cycle; Cell viability; Colon cancer; Colorectal cancer; Deoxyribonucleic acid; DNA; Flow cytometry; Myc protein; Nucleotide sequence; Phenolic compounds; Polymerase chain reaction; Primers; Short Communication; Stem cells; Telomerase; Telomerase reverse transcriptase; Telomeres; Transcription; Yeast; 생활과학
• ISSN: 1976-1457; 2005-6168
• DOI: 10.4162/nrp.2019.13.1.58

Telomeres are located at the chromosomal ends and progressively shortened during each cell cycle. Telomerase, which is regulated by and - , maintains telomeric DNA sequences. Especially, telomerase is active in cancer and stem cells to maintain telomere length for replicative immortality. Recently we reported that walnut phenolic extract (WPE) can reduce cell viability in a colon cancer stem cell (CSC) model. We, therefore, investigated the effect of WPE on telomere maintenance in the same model. CD133 CD44 cells from HCT116, a human colon cancer cell line, were sorted by Fluorescence-activated cell sorting (FACS) and treated with WPE at the concentrations of 0, 10, 20, and 40 µg/mL for 6 days. Telomere lengths were assessed by quantitative real-time PCR (qRT-PCR) using telomere specific primers and DNA extracted from the cells, which was further adjusted with single-copy gene and reference DNA ( ). Telomerase activity was also measured by qRT-PCR after incubating the PCR mixture with cell protein extracts, which was adjusted with reference DNA ( ). Transcriptions of and - were determined using conventional RT-PCR. Telomere length of WPE-treated cells was significantly decreased in a dose-dependent manner (5.16 ± 0.13 at 0 µg/mL, 4.79 ± 0.12 at 10 µg/mL, 3.24 ± 0.08 at 20 µg/mL and 3.99 ± 0.09 at 40 µg/mL; = 0.0276). Telomerase activities concurrently decreased with telomere length (1.47 ± 0.04, 1.09 ± 0.01, 0.76 ± 0.08, and 0.88 ± 0.06; = 0.0067). There was a positive correlation between telomere length and telomerase activity (r = 0.9090; < 0.0001). Transcriptions of both and - were also significantly decreased in the same manner. In the present cell culture model, WPE reduced telomere maintenance, which may provide a mechanistic link to the effect of walnuts on the viability of colon CSCs.