Walnut phenolic extracts reduce telomere length and telomerase activity in a colon cancer stem cell model.
Nutr Res Pract. 2019 Feb ;13(1):58-63. Epub 2018 Dec 3. PMID: 30788057
BACKGROUND/OBJECTIVES: Telomeres are located at the chromosomal ends and progressively shortened during each cell cycle. Telomerase, which is regulated byand-, 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/METHODS: CD133CD44cells 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 40µg/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 ofand-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;= 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 bothand-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.