Expression of nuclear matrix proteins binding matrix attachment regions in prostate cancer. PARP‐1: New player in tumor progression

Prostate cancer (PCa) displays infrequent point mutations, whereas genomic rearrangements are highly prevalent. In eukaryotes, the genome is compartmentalized into chromatin loop domains by the attachment to the nuclear matrix (NM), and it has been demonstrated that several recombination hot spots are situated at the base of loops. Here, we have characterized the binding between NM proteins and matrix attachment regions (MARs) in PCa. Nontumor and 44 PCa tissues were analyzed. More aggressive tumors were characterized by an increase in the complexity of the NM protein patterns that was synchronous with a decrease in the number of proteins binding the MAR sequences. PARP‐1 was the protein that showed the most evident changes. The expression of the PARP‐1 associated with NM increased and it was dependent on tumor aggressiveness. Immunohistochemical analysis showed that the protein was significantly overexpressed in tumor cells. To explore the role of PARP‐1 in PCa progression, PCa cells were treated with the PARP inhibitor, ABT‐888. In androgen‐independent PC3 cells, PARP inhibition significantly decreased cell viability, migration, invasion, chromatin loop dimensions and histone acetylation. Collectively, our study provides evidence that MAR‐binding proteins are involved in the development and progression of PCa. PARP could play a key role in the compartmentalization of chromatin and in the development of the more aggressive phenotype. Thus, PARP can no longer be viewed only as an enzyme involved in DNA repair, but that its role in chromatin modulation could provide the basis for a new therapeutic approach to the treatment of PCa.     

EZH2和H3K27me3的表达对食管癌细胞迁移和侵袭能力的影响

目的:通过转染Zeste同源物增强子2(enhancer of zeste homolog 2,EZH2)过表达或者敲低载体,探讨EZH2和Lys27位点三甲基化组蛋白H3(histone H3 methylated Lys27,H3K27me3)对食管麟状细胞癌(esophageal squamous cell cancer,ESCC)细胞迁移和侵袭能力的影响.方法:应用实时荧光定量PCR、Western blotting法检测ESCC细胞株KYSE30、KYSE170、TE1、Eca109中EZH2 mRNA水平,以及ESCC细胞过表达或者敲低EZH2对H3 K27me3表达水平的影响.用划痕实验及Transwell侵袭实验分析过表达或者敲低EZH2后ESCC细胞的迁移侵袭能力.用实时荧光定量PCR法分析ESCC细胞过表达及敲低EZH2对MMPs mRNA水平的影响.结果:食管癌Eea109及TE1细胞中EZH2和H3K27me3 mRNA和蛋白水平明显高于KYSE30及KYSE170细胞(P＜0.05).过表达EZH2的食管癌KYSE30及KYSE170细胞H3K27me3蛋白的表达水平显著升高(P＜0.05),敲低EZH2后Eca109及TE1细胞H3 K27 me3蛋白的表达水平明显降低(P＜0.05).过表达EZH2后,KYSE30及KYSE170细胞的穿膜数目明显增多[(281.33±4.10)、(241.67 ±4.04) vs(132.00 ±4.00)、(105.33 ±3.51)个,均P＜0.05]、迁移距离明显增大[(63.6±1.2)、(62.5±2.5)vs (23.0±2.3)、(21.2±1.0) μm,P＜0.05].敲低EZH2后Eca109及TE1细胞的穿膜数目显著减少(均P＜0.05),转染shEZH2后Eca109及TE1细胞迁移的距离明显减小(均P＜0.05).结论:EZH2可增加靶基因启动子上组蛋白H3第27位赖氨酸的三甲基化,并增强ESCC细胞的迁移和侵袭能力.     

Transforming growth factor‐β induces CD44 cleavage that promotes migration of MDA‐MB‐435s cells through the up‐regulation of membrane type 1‐matrix metalloproteinase

CD44, a transmembrane receptor for hyaluronic acid, is implicated in various adhesion‐dependent cellular processes, including cell migration, tumor cell metastasis and invasion. Recent studies demonstrated that CD44 expressed in cancer cells can be proteolytically cleaved at the ectodomain by membrane type 1‐matrix metalloproteinase (MT1‐MMP) to form soluble CD44 and that CD44 cleavage plays a critical role in cancer cell migration. Here, we show that transforming growth factor‐β (TGF‐β), a multifunctional cytokine involved in cell proliferation, differentiation, migration and pathological processes, induces MT1‐MMP expression in MDA‐MB‐435s cells. TGF‐β‐induced MT1‐MMP expression was blocked by the specific extracellular regulated kinase‐1/2 (ERK1/2) inhibitor PD98059 and the specific phosphoinositide 3‐OH kinase (PI3K) inhibitor LY294002. In addition, treatment with SP600125, an inhibitor for c‐Jun NH₂‐terminal kinase (JNK), resulted in a significant inhibition of MT1‐MMP production. These data suggest that ERK1/2, PI3K, and JNK likely play a role in TGF‐β‐induced MT1‐MMP expression. Interestingly, treatment of MDA‐MB‐435s cells with TGF‐β resulted in a colocalization of MT1‐MMP and CD44 in the cell membrane and in an increased level of soluble CD44. Using an electric cell‐substrate impedance sensing cell‐electrode system, we demonstrated that TGF‐β treatment promotes MDA‐MB‐435s cell migration, involving MT1‐MMP‐mediated CD44 cleavage. MT1‐MMP siRNA transfection‐inhibited TGF‐β‐induced cancer cell transendothelial migration. Thus, this study contributes to our understanding of molecular mechanisms that play a critical role in tumor cell invasion and metastasis. © 2009 Wiley‐Liss, Inc.