Shamanna Raghavendra A, Lu Huiming, Croteau Deborah L, Arora Arvind, Agarwal Devika, Ball Graham, Aleskandarany Mohammed A, Ellis Ian O, Pommier Yves, Madhusudan Srinivasan, Bohr Vilhelm A
Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, NIH, Baltimore, Maryland, USA.
Academic Unit of Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, UK.
Oncotarget. 2016 Mar 22;7(12):13269-84. doi: 10.18632/oncotarget.7906.
Werner syndrome protein (WRN) is a RecQ helicase that participates in DNA repair, genome stability and cellular senescence. The five human RecQ helicases, RECQL1, Bloom, WRN, RECQL4 and RECQL5 play critical roles in DNA repair and cell survival after treatment with the anticancer drug camptothecin (CPT). CPT derivatives are widely used in cancer chemotherapy to inhibit topoisomerase I and generate DNA double-strand breaks during replication. Here we studied the effects of CPT on the stability and expression dynamics of human RecQ helicases. In the cells treated with CPT, we observed distinct effects on WRN compared to other human RecQ helicases. CPT altered the cellular localization of WRN and induced its degradation by a ubiquitin-mediated proteasome pathway. WRN knockdown cells as well as CPT treated cells became senescent and stained positive for senescence-associated β-galactosidase at a higher frequency compared to control cells. However, the senescent phenotype was attenuated by ectopic expression of WRN suggesting functional implication of WRN degradation in CPT treated cells. Approximately 5-23% of breast cancer tumors are known to respond to CPT-based chemotherapy. Interestingly, we found that the extent of CPT-induced WRN degradation correlates with increasing sensitivity of breast cancer cells to CPT. The abundance of WRN decreased in CPT-treated sensitive cells; however, WRN remained relatively stable in CPT-resistant breast cancer cells. In a large clinical cohort of breast cancer patients, we find that WRN and topoisomerase I expression correlate with an aggressive tumor phenotype and poor prognosis. Our novel observations suggest that WRN abundance along with CPT-induced degradation could be a promising strategy for personalizing CPT-based cancer chemotherapeutic regimens.
沃纳综合征蛋白（WRN）是一种RecQ解旋酶，参与DNA修复、基因组稳定性和细胞衰老过程。人类的五种RecQ解旋酶，即RECQL1、布卢姆综合征蛋白、WRN、RECQL4和RECQL5，在使用抗癌药物喜树碱（CPT）治疗后，对DNA修复和细胞存活起着关键作用。CPT衍生物广泛应用于癌症化疗，以抑制拓扑异构酶I并在复制过程中产生DNA双链断裂。在此，我们研究了CPT对人类RecQ解旋酶稳定性和表达动态的影响。在用CPT处理的细胞中，我们观察到WRN与其他人类RecQ解旋酶相比有明显不同的效应。CPT改变了WRN的细胞定位，并通过泛素介导的蛋白酶体途径诱导其降解。与对照细胞相比，WRN敲低细胞以及CPT处理的细胞更易衰老，且衰老相关β-半乳糖苷酶染色呈阳性。然而，通过WRN的异位表达，衰老表型得到了缓解，这表明WRN降解在CPT处理的细胞中具有功能意义。已知约5%-23%的乳腺癌肿瘤对基于CPT的化疗有反应。有趣的是，我们发现CPT诱导的WRN降解程度与乳腺癌细胞对CPT的敏感性增加相关。在CPT处理的敏感细胞中，WRN的丰度降低；然而，在对CPT耐药的乳腺癌细胞中，WRN保持相对稳定。在一个大型乳腺癌患者临床队列中，我们发现WRN和拓扑异构酶I的表达与侵袭性肿瘤表型和不良预后相关。我们的新发现表明，WRN丰度以及CPT诱导的降解可能是个性化基于CPT的癌症化疗方案的一个有前景的策略。
