Medical Molecular Biology Unit, University College London, UK.
Cell Stress Chaperones. 2011 Jul;16(4):427-39. doi: 10.1007/s12192-011-0256-8. Epub 2011 Jan 29.
POU4F2/Brn-3b transcription factor (referred to as Brn-3b) is elevated in >60% of breast cancers and profoundly alters growth and behaviour of cancer cells by regulating distinct subsets of target genes. Previous studies showed that Brn-3b was required to maximally transactivate small heat shock protein, HSPB1/Hsp-27 (referred to as Hsp-27), and consequently, Brn-3b expression correlated well with Hsp27 levels in human breast biopsies. In these studies, we showed that Brn-3b is increased in MCF7 breast cancer cells that survive following treatment with chemotherapeutic drug doxorubicin (Dox) with concomitant increases in Hsp-27 expression. Targeting of Brn-3b using short interfering RNA reduced Hsp-27 in Dox-treated cells, suggesting that Brn-3b regulates Hsp-27 expression under these conditions. Wound healing assays showed increased Brn-3b in Dox-treated migratory cells that also express Hsp-27. Interestingly, Hsp-27 phosphorylation and cellular localisation are also significantly altered at different times following Dox treatment. Thus, phospho-Hsp-27 (p-Hsp27) protein displayed widespread distribution after 24 hrs of Dox treatment but was restricted to the nucleus after 5 days. However, in drug-resistant cells (grown in Dox for > 1 month), p-Hsp-27 was excluded from nuclei and most of the cytoplasm and appeared to be associated with the cell membrane. Studies to determine how this protein promotes survival and migration in breast cancer cells showed that the protective effects were conferred by unphosphorylated Hsp-27 protein. Thus, complex and dynamic mechanisms underlie effects of Hsp-27 protein in breast cancer cells following treatment with chemotherapeutic drugs such as Dox, and this may contribute to invasiveness and drug resistance following chemotherapy.
POU4F2/Brn-3b 转录因子（简称 Brn-3b）在超过 60%的乳腺癌中升高，并通过调节不同的靶基因亚群，显著改变癌细胞的生长和行为。以前的研究表明，Brn-3b 是最大程度地激活小热休克蛋白 HSPB1/Hsp-27（简称 Hsp-27）所必需的，因此，Brn-3b 在人类乳腺活检中的表达与 Hsp27 水平密切相关。在这些研究中，我们发现，在接受化疗药物阿霉素（Dox）治疗后存活下来的 MCF7 乳腺癌细胞中，Brn-3b 增加，同时 Hsp-27 表达增加。使用短发夹 RNA 靶向 Brn-3b 减少了 Dox 处理细胞中的 Hsp-27，表明在这些条件下，Brn-3b 调节 Hsp-27 的表达。划痕愈合试验显示，在接受 Dox 处理的迁移细胞中 Brn-3b 增加，这些细胞也表达 Hsp-27。有趣的是，在 Dox 处理后不同时间，Hsp-27 的磷酸化和细胞定位也发生了显著改变。因此，在 Dox 处理 24 小时后，p-Hsp-27 蛋白广泛分布，但在 5 天后则局限于核内。然而，在耐药细胞（在 Dox 中生长超过 1 个月）中，p-Hsp-27 被排除在核外，大部分细胞质中，并似乎与细胞膜相关。研究确定这种蛋白如何在乳腺癌细胞中促进存活和迁移，结果表明，未磷酸化的 Hsp-27 蛋白赋予了保护作用。因此，在乳腺癌细胞中，Hsp-27 蛋白在接受化疗药物（如 Dox）治疗后的作用是由复杂和动态的机制所决定的，这可能导致化疗后侵袭性和耐药性的增加。
