Zimmers Stephanie M, Browne Eva P, Williams Kristin E, Jawale Rahul M, Otis Christopher N, Schneider Sallie S, Arcaro Kathleen F
1Department of Veterinary & Animal Sciences, University of Massachusetts, Amherst, Life Sciences Laboratories, Room 540D, 240 Thatcher Road, Amherst, MA 01003 USA.
2Pathology Department, Baystate Medical Center, 759 Chestnut Street, Springfield, MA 01199 USA.
Cancer Cell Int. 2018 Jul 6;18:94. doi: 10.1186/s12935-018-0589-9. eCollection 2018.
The DNA methyltransferase 1 inhibitor, 5-Aza-2'-deoxycytidine (5-Aza-dC) is a potential treatment for breast cancer. However, not all breast tumors will respond similarly to treatment with 5-Aza-dC, and little is known regarding the response of hormone-resistant breast cancers to 5-Aza-dC.
We demonstrate that 5-Aza-dC-treatment has a stronger effect on an estrogen receptor-negative, Tamoxifen-selected cell line, TMX2-28, than on the estrogen receptor-positive, MCF7, parental cell line. Using data obtained from the HM450 Methylation Bead Chip, pyrosequencing, and RT-qPCR, we identified a panel of genes that are silenced by promoter methylation in TMX2-28 and re-expressed after treatment with 5-Aza-dC.
One of the genes identified, tumor associated calcium signal transducer 2 (), is altered by DNA methylation, and there is evidence that in some cancers decreased expression may result in greater proliferation. Analysis of DNA methylation of and protein expression of its product, trophoblast antigen protein 2 (TROP2), was extended to a panel of primary (n = 34) and recurrent (n = 34) breast tumors. Stratifying tumors by both recurrence and ER status showed no significant relationship between TROP2 levels and methylation. Knocking down expression in MCF7 increased proliferation however; re-expressing in TMX2-28 did not inhibit proliferation, indicating that re-expression alone was insufficient to explain the decreased proliferation observed after treatment with 5-Aza-dC.
These results illustrate the complexity of the TROP2 signaling network. However, TROP2 may be a valid therapeutic target for some cancers. Further studies are needed to identify biomarkers that indicate how TROP2 signaling affects tumor growth and whether targeting TROP2 would be beneficial to the patient.
DNA甲基转移酶1抑制剂5-氮杂-2'-脱氧胞苷（5-aza-dC）是一种潜在的乳腺癌治疗药物。然而，并非所有乳腺肿瘤对5-aza-dC治疗的反应都相似，关于激素抵抗性乳腺癌对5-aza-dC的反应知之甚少。
我们证明，5-aza-dC处理对雌激素受体阴性、经他莫昔芬筛选的细胞系TMX2-28的作用比对雌激素受体阳性的亲本细胞系MCF7更强。利用从HM450甲基化微珠芯片、焦磷酸测序和逆转录定量聚合酶链反应获得的数据，我们鉴定了一组在TMX2-28中因启动子甲基化而沉默并在5-aza-dC处理后重新表达的基因。
鉴定出的基因之一肿瘤相关钙信号转导蛋白2（）因DNA甲基化而改变，有证据表明在某些癌症中其表达降低可能导致增殖增加。对其产物滋养层抗原蛋白2（TROP2）的DNA甲基化和蛋白表达分析扩展到一组原发性（n = 34）和复发性（n = 34）乳腺肿瘤。按复发和雌激素受体状态对肿瘤进行分层显示，TROP2水平与甲基化之间无显著关系。然而，在MCF7中敲低表达会增加增殖；在TMX2-28中重新表达并不能抑制增殖，这表明单独重新表达不足以解释5-aza-dC处理后观察到的增殖减少。
这些结果说明了TROP2信号网络的复杂性。然而，TROP2可能是某些癌症的有效治疗靶点。需要进一步研究以鉴定指示TROP2信号如何影响肿瘤生长以及靶向TROP2是否对患者有益的生物标志物。
