Shibuta Kenji, Mori Masaki, Shimoda Katsuhiro, Inoue Hiroshi, Mitra Prasenjit, Barnard Graham F
Department of Clinical Oncology, Medical Institute of Bioregulation, Kyushu University, Tsurumibaru, Beppu 874-0838, Japan.
Jpn J Cancer Res. 2002 Jul;93(7):789-97. doi: 10.1111/j.1349-7006.2002.tb01321.x.
The CXCL12 / CXCR4 system may be important in carcinoma. Expression of the alpha-chemokine SDF-1alpha (stromal cell derived factor-1alpha) / CXCL12 mRNA is reduced in many carcinomas, yet its tissue protein expression may guide metastasis. Here we first compare the mRNA and protein expression of CXCL12 and its receptor CXCR4 in human liver, hepatocellular carcinoma, and malignant cell lines, and then assess cell cycle variation in CXCR4 expression. CXCR4 mRNA was present in most normal human tissues and malignant cell lines; it was only marginally reduced in hepatomas, while CXCL12 was markedly reduced, P < 0.0001. Immuno-histochemical staining of adjacent non-malignant liver showed regional CXCR4 cytoplasmic and cell-surface staining, limited to those hepatocytes around the central vein, a distribution resembling that of CXCL12. CXCL12 protein was not present in hepatocellular carcinoma cells in vivo, nor was cytoplasmic CXCR4 staining; nuclear CXCR4 protein expression in some malignant hepatocytes and CXCR4 staining of capillary endothelial cells around tumor cells were noted. In some malignant cell lines that had no CXCL12 on northern blots CXCL12 was weakly detectable by RT-PCR or protein staining in the cytoplasm of a few cells. With a view to future manipulation of CXCL12 / CXCR4 expression and growth we noted that in HT-29 cells CXCR4 protein expression was less on confluent than on non-confluent cells and varied during the cell cycle. Higher expression was associated most closely with the percentage of cells in the S-phase and inversely with the percentage of cells in the G1-phase. Treatment of HT-29 cells with butyrate reduced CXCR4 cell surface expression and reduced the percentage of cells in S-phase. In summary, CXCL12 protein expression parallels its mRNA, being markedly reduced in malignant cell lines and hepatomas; in liver, the regional distributions of CXCL12 and cytoplasmic CXCR4 are similar; finally, in HT-29, CXCR4 expression correlates with the S-phase of the cell cycle and is reduced during butyrate-induced differentiation.
CXCL12/CXCR4系统在癌症中可能具有重要作用。许多癌症中α-趋化因子SDF-1α（基质细胞衍生因子-1α）/CXCL12 mRNA的表达降低，但其组织蛋白表达可能会引导转移。在此，我们首先比较CXCL12及其受体CXCR4在人肝脏、肝细胞癌和恶性细胞系中的mRNA和蛋白表达，然后评估CXCR4表达的细胞周期变化。CXCR4 mRNA存在于大多数正常人体组织和恶性细胞系中；在肝癌中仅略有降低，而CXCL12则明显降低，P<0.0001。对相邻非恶性肝脏进行免疫组织化学染色显示，CXCR4在细胞质和细胞表面呈区域性染色，仅限于中央静脉周围的肝细胞，其分布类似于CXCL12。在体内，肝细胞癌细胞中不存在CXCL12蛋白，细胞质中也没有CXCR4染色；在一些恶性肝细胞中观察到核CXCR4蛋白表达，以及肿瘤细胞周围毛细血管内皮细胞的CXCR4染色。在一些Northern印迹上没有CXCL12的恶性细胞系中，通过RT-PCR或蛋白染色在少数细胞的细胞质中可微弱检测到CXCL12。为了未来对CXCL12/CXCR4表达和生长进行调控，我们注意到在HT-29细胞中，汇合细胞上的CXCR4蛋白表达低于未汇合细胞，并且在细胞周期中有所变化。较高的表达与S期细胞百分比最密切相关，与G1期细胞百分比呈负相关。用丁酸盐处理HT-29细胞可降低CXCR4细胞表面表达，并降低S期细胞百分比。总之，CXCL12蛋白表达与其mRNA平行，在恶性细胞系和肝癌中明显降低；在肝脏中，CXCL12和细胞质CXCR4的区域分布相似；最后，在HT-29中，CXCR4表达与细胞周期的S期相关，并且在丁酸盐诱导的分化过程中降低。
