Smorenburg S M, Griffini P, Tiggelman A B, Moorman A F, Boers W, Van Noorden J F
Laboratory of Cell Biology and Histology, University of Amsterdam, The Netherlands.
Hepatology. 1996 Mar;23(3):560-70. doi: 10.1002/hep.510230323.
Localization and production of alpha2-macroglobulin (alpha2M), a multifunctional binding protein with protease and cytokine scavenging properties, was studied in situ in rat livers containing experimentally induced colon carcinoma metastases by means of immunocytochemistry and in situ hybridization methods. The study was performed to investigate whether alpha2M production by hepatocytes plays a role in the defense against the growth of metastases on the basis of its protease inhibiting capacity. It was found that colon cancer cells in all developmental stages of the metastases contained large amounts of messenger RNA (mRNA) of alpha2M but hardly any alpha2M protein. Cancer cells in culture contained large amounts of both mRNA and protein of alpha2M. In contrast, stromal cells and liver cells did not show positivity for alpha2M mRNA above background levels. The exception was a few layers of hepatocytes around the latest stage of metastases. Hepatocytes contained both alpha2M mRNA and protein only when Kupffer cells were present, indicating that alpha2M mRNA production was induced via Kupffer cells. On the other hand, alpha2M protein was found in high amounts in the sinusoids and stroma of all metastases, irrespective of their developmental stage. Increased levels of alpha2M could not be detected in serum in all but one rat tested (n=8). It is concluded that production of alpha2M by hepatocytes occurs only around the latest developmental stage of metastases and that alpha2M does not play a significant role in the defense against metastatic cancer growth in rat liver. In contrast, cancer cells produce and secrete large amounts of alpha2M, which seems to be linked with their tumorigenicity. We suggest that this alpha2M captures cytokines rather than proteases by complex formation. These complexes were observed using immunocytochemical staining for alpha2M protein indicating that it was captured by either stromal cells, sinusoidal cells, or hepatocytes that are in direct contact with cancer cells, Therefore, changes in serum levels of alpha2M were limited, indicating that these levels do not reflect local production and effects of alpha2M.
利用免疫细胞化学和原位杂交方法，对含有实验性诱导结肠癌转移灶的大鼠肝脏进行了α2-巨球蛋白（α2M）的定位和产生情况的研究。α2M是一种具有蛋白酶和细胞因子清除特性的多功能结合蛋白。进行这项研究是为了基于其蛋白酶抑制能力，探讨肝细胞产生的α2M在抵御转移灶生长中是否发挥作用。研究发现，转移灶各个发育阶段的结肠癌细胞都含有大量的α2M信使核糖核酸（mRNA），但几乎没有α2M蛋白。培养的癌细胞含有大量的α2M mRNA和蛋白。相比之下，基质细胞和肝细胞在背景水平之上未显示α2M mRNA阳性。例外情况是转移灶最晚阶段周围的几层肝细胞。仅当存在库普弗细胞时，肝细胞才同时含有α2M mRNA和蛋白，这表明α2M mRNA的产生是通过库普弗细胞诱导的。另一方面，在所有转移灶的窦状隙和基质中都发现了大量的α2M蛋白，无论其发育阶段如何。在除一只大鼠外的所有受试大鼠（n = 8）血清中均未检测到α2M水平升高。结论是，肝细胞产生α2M仅发生在转移灶最晚发育阶段周围，并且α2M在大鼠肝脏抵御转移性癌症生长中不发挥重要作用。相比之下，癌细胞产生并分泌大量的α2M，这似乎与其致瘤性有关。我们认为这种α2M通过形成复合物捕获细胞因子而非蛋白酶。使用α2M蛋白的免疫细胞化学染色观察到这些复合物，表明它被与癌细胞直接接触的基质细胞、窦状隙细胞或肝细胞捕获。因此，α2M血清水平的变化有限，表明这些水平不能反映α2M的局部产生和作用。
