Department of Biomedical Sciences, Cancer Research Center, University at Albany, State University of New York, Rensselaer, NY, USA.
Oncogene. 2013 Dec 5;32(49):5512-21. doi: 10.1038/onc.2013.217. Epub 2013 Jun 17.
Overexpression of the adverse prognostic marker ERBB2 occurs in 30% of breast cancers and is associated with aggressive disease and poor outcomes. Our recent findings have shown that NR1D1 and the peroxisome proliferator-activated receptor-γ (PPARγ)-binding protein (PBP) act through a common pathway in upregulating several genes in the de novo fatty acid synthesis network, which is highly active in ERBB2-positive breast cancer cells. NR1D1 and PBP are functionally related to PPARγ, a well-established positive regulator of adipogenesis and lipid storage. Here, we report that inhibition of the PPARγ pathway reduces the aldehyde dehydrogenase (ALDH)-positive population in ERBB2-positive breast cancer cells. Results from in vitro tumorsphere formation assays demonstrate that the PPARγ antagonists GW9662 and T0070907 decrease tumorsphere formation in ERBB2-positive cells, but not other breast cells. We show that the mechanism by which GW9662 treatment causes a reduction in ALDH-positive population cells is partially due to ROS, as it can be rescued by treatment with N-acetyl-cysteine. Furthermore, global gene expression analyses show that GW9662 treatment suppresses the expression of several lipogenic genes, including ACLY, MIG12, FASN and NR1D1, and the stem-cell related genes KLF4 and ALDH in BT474 cells. Antagonist treatment also decreases the level of acetylation in histone 3 and histone 4 in BT474 cells, compared with MCF7 cells. In vivo, GW9662 pre-treatment inhibits the tumor-seeding ability of BT474 cells. Together, these results show that the PPARγ pathway is critical for the cancer stem cell properties of ERBB2-positive breast cancer cells.
过表达不良预后标志物 ERBB2 发生在 30%的乳腺癌中，与侵袭性疾病和不良预后相关。我们最近的研究结果表明，NR1D1 和过氧化物酶体增殖物激活受体-γ（PPARγ）结合蛋白（PBP）通过共同途径上调从头脂肪酸合成网络中的几个基因，该网络在 ERBB2 阳性乳腺癌细胞中高度活跃。NR1D1 和 PBP 在功能上与 PPARγ 相关，后者是脂肪生成和脂质储存的公认正调控因子。在这里，我们报告抑制 PPARγ 途径可减少 ERBB2 阳性乳腺癌细胞中醛脱氢酶（ALDH）阳性细胞群。体外肿瘤球体形成实验结果表明，PPARγ 拮抗剂 GW9662 和 T0070907 减少 ERBB2 阳性细胞中的肿瘤球体形成，但对其他乳腺癌细胞没有影响。我们表明，GW9662 处理导致 ALDH 阳性细胞群减少的机制部分是由于 ROS，因为它可以通过用 N-乙酰半胱氨酸处理来挽救。此外，全基因表达分析表明，GW9662 处理抑制了几个脂肪生成基因的表达，包括 ACLY、MIG12、FASN 和 NR1D1，以及 BT474 细胞中的干细胞相关基因 KLF4 和 ALDH。拮抗剂处理还降低了 BT474 细胞中组蛋白 3 和组蛋白 4 的乙酰化水平，与 MCF7 细胞相比。在体内，GW9662 预处理抑制了 BT474 细胞的肿瘤播种能力。总之，这些结果表明 PPARγ 途径对于 ERBB2 阳性乳腺癌细胞的癌症干细胞特性至关重要。
