Department of Laboratory Science, the Fourth Hospital Affiliated to Guangxi Medical University, Liuzhou 545005, Guangxi, China.
Int J Mol Sci. 2013 Aug 9;14(8):16554-69. doi: 10.3390/ijms140816554.
Nuclear hormone receptor family member PPARγ plays an important role in mammary gland tumorigenesis. Previous studies have shown PPARγ has cytoplasmic activities upon tetradecanoyl phorbol acetate (TPA) stimulation. However, the clinical pathological significance of cytoplasmic PPARγ is not completely understood in human breast cancer. Skp2 is oncogenic, and its frequent amplification and overexpression correlated with the grade of malignancy. In this study, the role of cytoplasmic PPARγ and Skp2 expression was investigated in human breast cancer progression. Therefore, immunohistochemical analysis was performed on formalin-fixed paraffin sections of 70 specimens. Furthermore, Western blot and immunofluorescence microscopy analysis were used to study the relationship between expression of cytoplasmic PPARγ and Skp2 expression in human breast cancer cells in vitro. Results showed that the expression of cytoplasmic PPARγ was positively correlated with Skp2 expression (p < 0.05), and correlated significantly with estrogen receptor (p = 0.026) and pathological grade (p = 0.029), respectively. In addition, Skp2 overexpression can provoke cytoplasmic localization of PPARγ upon MEK1-dependent mechanisms in human breast cancer cells by nuclear-cytosolic fractionation technology and immunofluorescence microscopy analysis. Using RNA interference technology, we also found that down-regulated Skp2 reduced the phosphorylation level of MEK1 and significantly reversed TPA-induced nuclear export of PPARγ in MDA-MB-231 cells. The changes in the subcellular localization of PPARγ may represent a novel target for selective interference in patients with breast cancer.
核激素受体家族成员 PPARγ 在乳腺肿瘤发生中起重要作用。先前的研究表明，PPARγ 在十四烷酰佛波醇乙酸酯（TPA）刺激下具有细胞质活性。然而，细胞质 PPARγ 在人类乳腺癌中的临床病理意义尚不完全清楚。Skp2 是致癌的，其频繁扩增和过表达与恶性程度相关。在这项研究中，研究了细胞质 PPARγ 和 Skp2 表达在人类乳腺癌进展中的作用。因此，对 70 例福尔马林固定石蜡切片进行了免疫组织化学分析。此外，还使用 Western blot 和免疫荧光显微镜分析研究了体外人类乳腺癌细胞中细胞质 PPARγ 和 Skp2 表达之间的关系。结果表明，细胞质 PPARγ 的表达与 Skp2 的表达呈正相关（p<0.05），并且分别与雌激素受体（p=0.026）和病理分级（p=0.029）显著相关。此外，通过核质分离技术和免疫荧光显微镜分析发现，Skp2 过表达可以通过 MEK1 依赖性机制引起人类乳腺癌细胞中 PPARγ 的细胞质定位。使用 RNA 干扰技术，我们还发现下调 Skp2 可降低 MEK1 的磷酸化水平，并显著逆转 TPA 诱导的 MDA-MB-231 细胞中 PPARγ 的核输出。PPARγ 亚细胞定位的变化可能代表了一种针对乳腺癌患者的选择性干扰的新靶点。
