Min Ahrum, Im Seock-Ah, Kim Debora Keunyoung, Song Sang-Hyun, Kim Hee-Jun, Lee Kyung-Hun, Kim Tae-Yong, Han Sae-Won, Oh Do-Youn, Kim Tae-You, O'Connor Mark J, Bang Yung-Jue
Cancer Research Institute, Seoul National University College of Medicine, Seoul, 110-799, Korea.
Biomedical Research Institute, Seoul National University Hospital, Seoul, 110-799, Korea.
Breast Cancer Res. 2015 Mar 7;17:33. doi: 10.1186/s13058-015-0534-y.
Olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, has been found to have therapeutic potential for treating cancers associated with impaired DNA repair capabilities, particularly those with deficiencies in the homologous recombination repair (HRR) pathway. Histone deacetylases (HDACs) are important for enabling functional HRR of DNA by regulating the expression of HRR-related genes and promoting the accurate assembly of HRR-directed sub-nuclear foci. Thus, HDAC inhibitors have recently emerged as a therapeutic agent for treating cancer by inhibiting DNA repair. Based on this, HDAC inhibition could be predicted to enhance the anti-tumor effect of PARP inhibitors in cancer cells by blocking the HRR pathway.
We determined whether suberoylanilide hydroxamic acid (SAHA), a HDAC inhibitor, could enhance the anti-tumor effects of olaparib on breast cancer cell lines using a cytotoxic assay, cell cycle analysis, and Western blotting. We evaluated how exposure to SAHA affects the expression of HRR-associated genes. The accumulation of DNA double strand breaks (DSBs) induced by combination treatment was assessed. Induction of autophagy was monitored by imaging green fluorescent protein-tagged microtubule-associated protein 1A/1B-light chain 3 (LC3) expression following co-treatment with olaparib and SAHA. These in vitro data were validated in vivo using a human breast cancer xenograft model.
Triple-negative breast cancer cell (TNBC) lines showed heterogeneous responses to the PARP and HDAC inhibitors. Co-administration of olaparib and SAHA synergistically inhibited the growth of TNBC cells that expressed functional Phosphatase and tensin homolog (PTEN). This effect was associated with down-regulation of the proliferative signaling pathway, increased apoptotic and autophagic cell death, and accumulation of DNA damage. The combined anti-tumor effect of olaparib and SAHA was also observed in a xenograft model. These data suggest that PTEN expression in TNBC cells can sensitize the cell response to simultaneous inhibition of PARP and HDAC both in vitro and in vivo.
Our findings suggest that expression of functional PTEN may serve as a biomarker for selecting TNBC patients that would favorably respond to a combination of olaparib with SAHA. This provides a strong rationale for treating TNBC patients with PTEN expression with a combination therapy consisting of olaparib and SAHA.
奥拉帕利是一种聚（ADP - 核糖）聚合酶（PARP）抑制剂，已被发现对治疗与DNA修复能力受损相关的癌症具有治疗潜力，特别是那些在同源重组修复（HRR）途径存在缺陷的癌症。组蛋白脱乙酰酶（HDAC）通过调节HRR相关基因的表达并促进HRR导向的亚核灶的精确组装，对实现DNA的功能性HRR很重要。因此，HDAC抑制剂最近已成为通过抑制DNA修复来治疗癌症的治疗剂。基于此，可以预测HDAC抑制通过阻断HRR途径增强PARP抑制剂在癌细胞中的抗肿瘤作用。
我们使用细胞毒性试验、细胞周期分析和蛋白质印迹法，确定HDAC抑制剂辛二酰苯胺异羟肟酸（SAHA）是否能增强奥拉帕利对乳腺癌细胞系的抗肿瘤作用。我们评估了暴露于SAHA如何影响HRR相关基因的表达。评估了联合治疗诱导的DNA双链断裂（DSB）的积累。在与奥拉帕利和SAHA共同处理后，通过成像绿色荧光蛋白标记的微管相关蛋白1A/1B轻链3（LC3）的表达来监测自噬的诱导。这些体外数据在人乳腺癌异种移植模型中进行了体内验证。
三阴性乳腺癌细胞（TNBC）系对PARP和HDAC抑制剂表现出异质性反应。奥拉帕利和SAHA联合给药协同抑制表达功能性磷酸酶和张力蛋白同源物（PTEN）的TNBC细胞的生长。这种作用与增殖信号通路的下调、凋亡和自噬性细胞死亡增加以及DNA损伤的积累有关。在异种移植模型中也观察到了奥拉帕利和SAHA联合的抗肿瘤作用。这些数据表明，TNBC细胞中的PTEN表达可使细胞在体外和体内对PARP和HDAC的同时抑制产生敏感反应。
我们的研究结果表明，功能性PTEN的表达可作为选择对奥拉帕利与SAHA联合治疗有良好反应的TNBC患者的生物标志物。这为用奥拉帕利和SAHA联合疗法治疗PTEN表达的TNBC患者提供了有力的理论依据。
