Sistayanarain Anchalee, Tsuneyama Koichi, Zheng Huachuan, Takahashi Hiroyuki, Nomoto Kazuhiro, Cheng Chunmei, Murai Yoshihiro, Tanaka Atsushi, Takano Yasuo
Molecular and Pathology, School of Medicine, University of Toyama, Sugitani 2630, Toyama, Japan.
Anticancer Res. 2006 Sep-Oct;26(5A):3585-93.
Aurora-B, a chromosomal passenger protein forming a complex with INCENP (inner centromere protein) and survivin, regulates stable bipolar spindle-kinetochore attachment in mitosis and chromosome segregation and cytokinesis. It was recently documented that Aurora-B directly phosphorylated histone H3, not only at Ser10, but also at Ser28, which contributed to chromosome number instability and mitotic chromosome condensation. This study aimed at investigating the expression of Aurora-B kinase (Aurora-B) and phosphorylated histone H3 (H3-P) and their roles in hepatocellular carcinogenesis.
The expressions of Aurora-B and H3-P were examined in hepatocellular carcinoma (HCC) by immunohistochemistry. A hepatoblastoma cell line, HepG2, was targeted and the isolation and characterization of alternative variants of Aurora-B were carried out. The Aurora encoding protein was detected in COS-7 transfected with different Aurora transcripts by Western blot. Finally, the expression of Aurora-B and its variant forms was examined in 17 HCCs by RT-PCR.
Immunohistochemically, Aurora-B was observed only in a few cases of HCC, while H3-P expression was more frequently detected in carcinoma foci than in non-carcinoma foci (p < 0.05). The isolation and characterization of two alternative variant forms of Aurora-B (termed Aurora-B1 and -B2) in the HepG2 cell line were successful. Aurora-B-transfected COS-7 cells expressed two different proteins, one of which was similar to the expression product of Aurora-B1 in size. Aurora-B transcripts were detected in 12 out of 17 (70.5%) HCC cases examined. Aurora-B2 was predominantly detected in 9 (52.9%) cases, while regular Aurora-B and Aurora-B1 were detected in 6 (35.2%) and 7 (41.1%) cases, respectively.
Aberrant expression of Aurora-B and H3-P plays a role in hepatocarcinogenesis. Alterative splicing of Aurora-B produces different sizes of proteins in HCC. Temporally altered phosphorylation of histone-H3 in the entire cell cycle may up-regulate the entry of HCC into the cell cycle to enhance their proliferation.
Aurora-B是一种染色体乘客蛋白，与着丝粒内蛋白（INCENP）和生存素形成复合物，在有丝分裂过程中调节稳定的双极纺锤体-动粒附着、染色体分离和胞质分裂。最近有文献报道，Aurora-B不仅在Ser10位点，而且在Ser28位点直接磷酸化组蛋白H3，这导致了染色体数目不稳定和有丝分裂染色体凝聚。本研究旨在探讨Aurora-B激酶（Aurora-B）和磷酸化组蛋白H3（H3-P）的表达及其在肝细胞癌发生中的作用。
采用免疫组织化学方法检测肝细胞癌（HCC）中Aurora-B和H3-P的表达。以肝母细胞瘤细胞系HepG2为研究对象，对Aurora-B的可变剪接变体进行分离和鉴定。通过蛋白质印迹法检测在转染了不同Aurora转录本的COS-7细胞中Aurora编码蛋白的表达。最后，采用逆转录-聚合酶链反应（RT-PCR）检测17例HCC中Aurora-B及其变体形式的表达。
免疫组织化学结果显示，仅在少数HCC病例中观察到Aurora-B表达，而癌灶中H3-P的表达频率高于非癌灶（p<0.05）。成功分离并鉴定了HepG2细胞系中Aurora-B的两种可变剪接变体形式（分别命名为Aurora-B1和Aurora-B2）。转染Aurora-B的COS-7细胞表达两种不同的蛋白产物，其中一种在大小上与Aurora-B1的表达产物相似。在17例检测的HCC病例中，有12例（70.5%）检测到Aurora-B转录本。9例（52.9%）病例中主要检测到Aurora-B2，6例（35.2%）和7例（41.1%）病例中分别检测到正常的Aurora-B和Aurora-B1。
Aurora-B和H3-P的异常表达在肝癌发生中起作用。Aurora-B的可变剪接在HCC中产生不同大小的蛋白质。整个细胞周期中组蛋白H3磷酸化的时间改变可能上调HCC进入细胞周期的进程，从而增强其增殖能力。
