Abstract
BACKGROUND/OBJECTIVES: Telomeres are located at the chromosomal ends and progressively shortened during each cell cycle. Telomerase, which is regulated by hTERT and c-MYC, 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. MATERIALS AND METHODS: 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 (ddC t ). Telomerase activity was also measured by qRT-PCR after incubating the PCR mixture with cell protein extracts, which was adjusted with reference DNA (dC t ). Transcriptions of hTERT and c-MYC were determined using conventional RT-PCR. RESULTS: 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; P = 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; P = 0.0067). There was a positive correlation between telomere length and telomerase activity (r = 0.9090; P < 0.0001). Transcriptions of both hTERT and c-MYC were also significantly decreased in the same manner. CONCLUSION: 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.
| Original language | English |
|---|---|
| Pages (from-to) | 58-63 |
| Number of pages | 6 |
| Journal | Nutrition Research and Practice |
| Volume | 13 |
| Issue number | 1 |
| DOIs | |
| State | Published - Feb 2019 |
Bibliographical note
Funding Information:This work was supported by research grants from the California Walnut Commission (S.W.C.) and Korean Food Research Institute (project no. E0150302-04) (S.W.C.). All the authors participated in the conception, design, and conduction of the study as well as interpreting the data and drafting the manuscript. P.K.S and Y.Z. also performed cell culture studies and measured endpoints. J.C., M.S.K., Y.K., and S.W.C supervised the study. §Corresponding Author: Sang-Woon Choi, Tel. 82-2-3015-5025, Fax. 82-2-3015-5315, Email. sang.choi@cha.ac.kr Received: February 14, 2018, Revised: March 28, 2018, Accepted: September 19, 2018 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Funding Information:
This work was supported by research grants from the California Walnut Commission (S.W.C.) and Korean Food Research Institute (project no. E0150302-04) (S.W.C.). All the authors participated in the conception, design, and conduction of the study as well as interpreting the data and drafting the manuscript. P.K.S and Y.Z. also performed cell culture studies and measured endpoints. J.C., M.S.K., Y.K., and S.W.C supervised the study.
Publisher Copyright:
© 2019 The Korean Nutrition Society and the Korean Society of Community Nutrition.
Keywords
- Colonic neoplasms
- Stem cells
- Telomerase
- Telomere
- Walnut
