Ham Myeong-Sun, Lee Ju-Kyung, Kim Keun-Cheol
Medical and Bio-Material Research Center and Department of Biological Sciences, College of Natural Sciences, Kangwon National University, Chuncheon, Kangwon 200-701, Republic of Korea.
Mol Clin Oncol. 2013 Mar;1(2):373-378. doi: 10.3892/mco.2012.53. Epub 2012 Dec 18.
Cellular methylation is associated with stabilization of the chromatin structure. S-adenosyl methionine (SAM), a metabolite of methionine metabolism, is the methyl donor of essential cellular methyltransferase reactions. Using 3-(4,5-dimethylthiazol-2-yl)-2,5-dephenyl tetrazolium bromide (MTT) assay, we found that combination treatment of SAM and 5-fluorouracil (5-FU) specifically protected the anticancer effect of 5-FU, whereas the combination of SAM and cisplatin had no effect. This result was confirmed by FACS analysis. The combination treatment of SAM and 5-FU significantly decreased the dead cell population, while the G1 cell population was slightly increased, suggesting that protection of SAM is not associated with the cell cycle arrest of DNA-damaging drugs. We also analyzed which cellular methylation-related proteins were involved in the protective effect. Results showed the expression of DNA methyltransferases (DNMTs) was decreased with 5-FU alone but was increased with the combination treatment of SAM and 5-FU, suggesting that SAM protects the anticancer effect of 5-FU by regulating the expression of DNMTs. Taken together, the results indicated that SAM specifically modulates the anti-cancer effect of the DNA damage agent 5-FU and this may be modulated by aberrant DNA methylation.
细胞甲基化与染色质结构的稳定有关。S-腺苷甲硫氨酸（SAM）是甲硫氨酸代谢的一种代谢产物，是细胞内必需甲基转移酶反应的甲基供体。使用3-(4,5-二甲基噻唑-2-基)-2,5-二苯基溴化四氮唑（MTT）检测法，我们发现SAM与5-氟尿嘧啶（5-FU）联合处理能特异性地保护5-FU的抗癌效果，而SAM与顺铂联合则无此效果。流式细胞术分析证实了这一结果。SAM与5-FU联合处理显著降低了死细胞数量，而G1期细胞数量略有增加，这表明SAM的保护作用与DNA损伤药物的细胞周期阻滞无关。我们还分析了哪些细胞甲基化相关蛋白参与了这种保护作用。结果显示，单独使用5-FU时DNA甲基转移酶（DNMTs）的表达降低，但SAM与5-FU联合处理时其表达增加，这表明SAM通过调节DNMTs的表达来保护5-FU的抗癌效果。综上所述，结果表明SAM特异性地调节DNA损伤剂5-FU的抗癌作用，这可能受异常DNA甲基化的调节。
