SPARC promoter hypermethylation in colorectal cancers can be reversed by 5-Aza-2'deoxycytidine to increase SPARC expression and improve therapy response.
SPARC promoter hypermethylation in colorectal cancers can be reversed by 5-Aza-2'deoxycytidine to increase SPARC expression and improve therapy response.
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大肠癌中的SPARC启动子高甲基化可以被5-Aza-2'deoxyCytidine逆转以增加SPARC表达并改善治疗反应。
DOI：
10.1038/sj.bjc.6604377
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发表时间：
2008-06-03
影响因子：
8.8
通讯作者：
Tai, I. T.
中科院分区：
文献类型：
--
作者：
Cheetham, S.;Tang, M. J.;Mesak, F.;Kennecke, H.;Owen, D.;Tai, I. T.
癌症的不良临床结果通常可归因于对化疗的反应不足。克服原发性或获得性化疗耐药的策略可能最终对患者的生存产生有利影响。我们之前的研究表明，低水平的SPARC与治疗难治性结直肠癌（CRC）相关，上调其表达可增强体内化疗敏感性，从而导致更大的肿瘤消退。在这里，我们研究了SPARC启动子异常高甲基化作为抑制crc中SPARC的潜在机制，以及用去甲基化剂5-Aza-2 '脱氧胞苷（5-Aza）恢复其表达是否可以增强化学敏感性。首先，通过直接DNA测序从激光捕获的微解剖标本中分离基因组DNA，评估原代人crc中SPARC启动子的甲基化状态。研究人员还利用MIP101、RKO、HCT 116和HT-29评估了5-Aza对：SPARC启动子甲基化、SPARC表达、DNMT1与SPARC启动子相互作用（ChIP测定）、细胞活力、细胞凋亡和细胞增殖的影响。我们的研究结果揭示了crc中SPARC启动子的整体高甲基化，并确定了特定的CpG位点，这些位点在crc中一致甲基化，而在正常结肠中则没有甲基化。我们还证明，暴露于5-Aza后，CRC细胞系中的SPARC抑制可以逆转，这导致SPARC表达增加，导致细胞活力显著降低（在RKO细胞中额外降低39%）和更大的凋亡（在RKO细胞中额外降低18%），当与5-FU联合使用时（与单独使用5-FU相比）。我们令人兴奋的发现提示了基于特定甲基化CpG位点的潜在crc诊断标记。此外，研究结果揭示了使用去甲基化药物通过增加SPARC表达来改善反应的治疗效用。
Poor clinical outcomes in cancer can often be attributed to inadequate response to chemotherapy. Strategies to overcome either primary or acquired chemoresistance may ultimately impact on patients' survival favourably. We previously showed that lower levels of SPARC were associated with therapy-refractory colorectal cancers (CRC), and that upregulating its expression enhances chemo-sensitivity resulting in greater tumour regression in vivo. Here, we examined aberrant hypermethylation of the SPARC promoter as a potential mechanism for repressing SPARC in CRCs and whether restoration of its expression with a demethylating agent 5-Aza-2′deoxycytidine (5-Aza) could enhance chemosensitivity. Initially, the methylation status of the SPARC promoter from primary human CRCs were assessed following isolation of genomic DNA from laser capture microdissected specimens by direct DNA sequencing. MIP101, RKO, HCT 116, and HT-29 CRC cell lines were also used to evaluate the effect of 5-Aza on: SPARC promoter methylation, SPARC expression, the interaction between DNMT1 and the SPARC promoter (ChIP assay), cell viability, apoptosis, and cell proliferation. Our results revealed global hypermethylation of the SPARC promoter in CRCs, and identified specific CpG sites that were consistently methylated in CRCs but not in normal colon. We also demonstrate that SPARC repression in CRC cell lines could be reversed following exposure to 5-Aza, which resulted in increased SPARC expression, leading to a significant reduction in cell viability (by an additional 39% in RKO cells) and greater apoptosis (an additional 18% in RKO cells), when combined with 5-FU in vitro (in comparison to 5-FU alone). Our exciting findings suggest potential diagnostic markers of CRCs based on specific methylated CpG sites. Moreover, the results reveal the therapeutic utility of employing demethylating agents to improve response through augmentation of SPARC expression.
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影响因子：
20.3
作者：
Cameron, EE;Baylin, SB;Herman, JG
通讯作者：
Herman, JG
影响因子：
4.8
作者：
Rich, JN;Shi, Q;Wang, XF
通讯作者：
Wang, XF
DOI：
10.1073/pnas.93.18.9821
发表时间：
1996-09-03
影响因子：
11.1
作者：
Herman, JG;Graff, JR;Baylin, SB
通讯作者：
Baylin, SB
影响因子：
15.9
作者：
Brekken, RA;Puolakkainen, P;Sage, EH
通讯作者：
Sage, EH
影响因子：
6.4
作者：
Chlenski, A;Liu, SQ;Cohn, SL
通讯作者：
Cohn, SL