Department of Medicine, Stanford University School of Medicine, 269 Campus Drive, CCSR 1105, Stanford, CA 94305-5151, USA.
Mol Cancer Ther. 2010 Nov;9(11):2970-81. doi: 10.1158/1535-7163.MCT-10-0780. Epub 2010 Nov 9.
The microtubule-associated protein Tau has been reported to be a predictive factor for clinical response to taxanes in metastatic breast cancer. We generated a panel of eight taxane-resistant variants from four human breast cancer cell lines (MCF-7, T-47D, MDA-MB-231, and BT-549). Four variants had higher levels of Tau compared with their T-47D and MDA-MB-231 parental cells. Using isoform-specific primers, we found that Tau 0N, 1N, 2N, 3R, and 4R isoforms are overexpressed in the resistant variants, as is Tau exon 6 but not exons 4A or 8. To determine whether Tau overexpression produces resistance to taxanes, we derived three independent T-47D clones stably overexpressing Tau 3R and 4R isoforms. Tau overexpression did not result in taxane resistance compared with parental cells transfected with vector alone. We then knocked down Tau expression in three cell lines that expressed Tau constitutively (MCF-7 and ZR-75-1 breast cancer cells, and OVCAR-3 ovarian cancer cells). Lentivirus-mediated silencing of Tau expression in MCF-7 and OVCAR-3 cells did not result in increased taxane sensitivity compared with luciferase short hairpin RNA-infected cells and uninfected parental cells. Transient silencing using Tau-specific small interfering RNAs also did not alter taxane sensitivity relative to nontargeting controls in both MCF-7 and ZR-75-1 cells. These results show that neither overexpression nor depletion of Tau modulates cellular sensitivity to taxanes. Although Tau overexpression has been reported to be a predictive marker of taxane resistance, it is not likely to be a direct mechanism of taxane resistance in breast cancer.
微管相关蛋白 Tau 已被报道为转移性乳腺癌中紫杉烷类药物临床反应的预测因子。我们从四种人乳腺癌细胞系（MCF-7、T-47D、MDA-MB-231 和 BT-549）中生成了一组八种紫杉烷类耐药变体。四种变体的 Tau 水平高于其 T-47D 和 MDA-MB-231 亲本细胞。使用同工型特异性引物，我们发现耐药变体中过度表达 Tau 0N、1N、2N、3R 和 4R 同工型，以及 Tau 外显子 6，但不包括外显子 4A 或 8。为了确定 Tau 过表达是否产生对紫杉烷类药物的耐药性，我们从 T-47D 中衍生出三种独立的稳定过表达 Tau 3R 和 4R 同工型的克隆。与单独转染载体的亲本细胞相比，Tau 过表达并未导致紫杉烷类药物耐药。然后，我们敲低了三种持续表达 Tau 的细胞系（乳腺癌细胞 MCF-7 和 ZR-75-1 以及卵巢癌细胞 OVCAR-3）中的 Tau 表达。慢病毒介导的 MCF-7 和 OVCAR-3 细胞中 Tau 表达的沉默并未导致与荧光素酶短发夹 RNA 感染细胞和未感染的亲本细胞相比增加紫杉烷类药物敏感性。在 MCF-7 和 ZR-75-1 细胞中，使用 Tau 特异性小干扰 RNA 进行瞬时沉默也没有改变相对于非靶向对照的紫杉烷类药物敏感性。这些结果表明，Tau 的过表达或耗竭均不能调节细胞对紫杉烷类药物的敏感性。尽管 Tau 过表达已被报道为紫杉烷类耐药的预测标志物，但它不太可能是乳腺癌中紫杉烷类耐药的直接机制。
