Department of Breast and Thyroid Surgery, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama, 701-0192, Japan.
Breast Cancer. 2014 Jan;21(1):75-85. doi: 10.1007/s12282-012-0356-z. Epub 2012 Mar 28.
Although the poly adenosine diphosphate (ADP)-ribose polymerase (PARP) inhibitor olaparib is known to have potent antitumor activity in BRCA-related breast cancer cells, a limited number of preclinical and clinical studies have shown antitumor activity of olaparib in non-BRCA-related breast cancer. We investigated antitumor activity of olaparib in breast cancer cell lines derived from patients with nonfamilial sporadic breast cancer.
Effects of olaparib alone or in combination with five different chemotherapeutic agents on cell growth, cell cycle progression, apoptosis, and proportion of cancer stem cells using the mammosphere assay and CD44/CD24/ESA cell surface marker assay were investigated in a panel of six sporadic breast cancer cell lines. Extracellular-signal-regulated kinase (ERK) phosphorylation was also investigated to elucidate action mechanisms of olaparib.
Olaparib inhibited the growth of two estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer cell lines and two ER-negative and HER2-negative breast cancer cell lines (50% growth inhibitory concentrations 1.3-3.0 μM) associated with G2/M accumulation and induction of apoptosis. In contrast, two HER2-positive cell lines were resistant to olaparib. Interestingly, olaparib significantly decreased the proportion of putative cancer stem cells in either sensitive or resistant cell lines. In addition, olaparib increased expression of p-ERK. Combined treatments of olaparib with a mitogen-activated protein kinase kinase (MEK) inhibitor U0126 completely suppressed expression of p-ERK. These treatments also inhibited the G2/M accumulation and apoptosis induction by olaparib. Among five chemotherapeutic agents commonly used for breast cancer treatment, only an irinotecan metabolite SN38 showed additive antitumor activity with olaparib. Importantly, the combined treatment enhanced the increase in G2/M accumulation and apoptosis induction as well as a decrease in the proportion of cancer stem cells.
This study has indicated for the first time that the PARP inhibitor olaparib has substantial antitumor and anticancer stem cell activity in breast cancer cell lines of nonfamilial origin. Upregulation of p-ERK might explain, at least in part, antitumor and anticancer stem cell activity of olaparib. Combined treatment of olaparib with irinotecan might be effective in treatment of non-BRCA-related breast cancer.
尽管聚腺苷二磷酸核糖聚合酶（PARP）抑制剂奥拉帕尼在 BRCA 相关乳腺癌细胞中具有很强的抗肿瘤活性，但为数不多的临床前和临床研究表明，奥拉帕尼在非 BRCA 相关乳腺癌中也具有抗肿瘤活性。我们研究了奥拉帕尼在非家族性散发性乳腺癌患者来源的乳腺癌细胞系中的抗肿瘤活性。
我们使用六株散发性乳腺癌细胞系研究了奥拉帕尼单独或与五种不同化疗药物联合应用对细胞生长、细胞周期进程、凋亡和使用球体形成实验和 CD44/CD24/ESA 细胞表面标志物实验检测的肿瘤干细胞比例的影响。还研究了细胞外信号调节激酶（ERK）磷酸化，以阐明奥拉帕尼的作用机制。
奥拉帕尼抑制了两株雌激素受体（ER）阳性和人表皮生长因子受体 2（HER2）阴性乳腺癌细胞系和两株 ER 阴性和 HER2 阴性乳腺癌细胞系（半数生长抑制浓度为 1.3-3.0μM）的生长，与 G2/M 积累和诱导凋亡有关。相比之下，两株 HER2 阳性细胞系对奥拉帕尼具有抗性。有趣的是，奥拉帕尼显著降低了敏感或耐药细胞系中推测的肿瘤干细胞比例。此外，奥拉帕尼增加了 p-ERK 的表达。奥拉帕尼与丝裂原活化蛋白激酶激酶（MEK）抑制剂 U0126 的联合治疗完全抑制了 p-ERK 的表达。这些治疗还抑制了奥拉帕尼诱导的 G2/M 积累和凋亡。在五种常用于乳腺癌治疗的化疗药物中，只有伊立替康代谢物 SN38 与奥拉帕尼具有相加的抗肿瘤活性。重要的是，联合治疗增强了 G2/M 积累和凋亡诱导的增加以及肿瘤干细胞比例的降低。
本研究首次表明，PARP 抑制剂奥拉帕尼在非家族性起源的乳腺癌细胞系中具有显著的抗肿瘤和抗肿瘤干细胞活性。p-ERK 的上调至少部分解释了奥拉帕尼的抗肿瘤和抗肿瘤干细胞活性。奥拉帕尼与伊立替康联合治疗可能对非 BRCA 相关乳腺癌的治疗有效。
