Thoracic Oncology Research Group, Institute of Molecular Medicine, Trinity College Dublin, Dublin 2, Republic of Ireland.
Int J Mol Med. 2012 Dec;30(6):1505-11. doi: 10.3892/ijmm.2012.1138. Epub 2012 Sep 21.
Gemcitabine is indicated in combination with cisplatin as first-line therapy for solid tumours including non-small cell lung cancer (NSCLC), bladder cancer and mesothelioma. Gemcitabine is an analogue of pyrimidine cytosine and functions as an anti-metabolite. Structurally, however, gemcitabine has similarities to 5-aza-2-deoxycytidine (decitabine/Dacogen®), a DNA methyltransferase inhibitor (DNMTi). NSCLC, mesothelioma and prostate cancer cell lines were treated with decitabine and gemcitabine. Reactivation of epigenetically silenced genes was examined by RT-PCR/qPCR. DNA methyltransferase activity in nuclear extracts and recombinant proteins was measured using a DNA methyl-transferase assay, and alterations in DNA methylation status were examined using methylation-specific PCR (MS-PCR) and pyrosequencing. We observe a reactivation of several epigenetically silenced genes including GSTP1, IGFBP3 and RASSF1A. Gemcitabine functionally inhibited DNA methyltransferase activity in both nuclear extracts and recombinant proteins. Gemcitabine dramatically destabilised DNMT1 protein. However, DNA CpG methylation was for the most part unaffected by gemcitabine. In conclusion, gemcitabine both inhibits and destabilises DNA methyltransferases and reactivates epigenetically silenced genes having activity equivalent to decitabine at concentrations significantly lower than those achieved in the treatment of patients with solid tumours. This property may contribute to the anticancer activity of gemcitabine.
吉西他滨联合顺铂适用于多种实体瘤的一线治疗，包括非小细胞肺癌（NSCLC）、膀胱癌和间皮瘤。吉西他滨是嘧啶胞嘧啶类似物，作为一种抗代谢物发挥作用。然而，从结构上看，吉西他滨与 5-氮杂-2′-脱氧胞苷（地西他滨/达珂®）相似，后者是一种 DNA 甲基转移酶抑制剂（DNMTi）。我们用地西他滨和吉西他滨处理 NSCLC、间皮瘤和前列腺癌细胞系。通过 RT-PCR/qPCR 检测表观遗传沉默基因的重新激活。使用 DNA 甲基转移酶测定法测量核提取物和重组蛋白中的 DNA 甲基转移酶活性，并使用甲基化特异性 PCR（MS-PCR）和焦磷酸测序检测 DNA 甲基化状态的改变。我们观察到几个表观遗传沉默基因的重新激活，包括 GSTP1、IGFBP3 和 RASSF1A。吉西他滨在核提取物和重组蛋白中均能抑制 DNA 甲基转移酶的活性。吉西他滨显著破坏 DNMT1 蛋白。然而，DNA CpG 甲基化在很大程度上不受吉西他滨影响。总之，吉西他滨既能抑制又能破坏 DNA 甲基转移酶，并使表观遗传沉默基因重新激活，其活性与地西他滨相当，而浓度明显低于治疗实体瘤患者时的浓度。这种特性可能有助于吉西他滨的抗癌活性。
