Lotan R, Amos B, Watanabe H, Raz A
Department of Tumor Biology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Cancer Res. 1992 Sep 15;52(18):4878-84.
beta-All-trans-retinoic acid (RA) has been shown to inhibit the growth, enhance the differentiation, and suppress the transformed and metastatic properties of certain human and murine melanoma cells. This study examined the effect of RA on the level of a cell surface receptor (M(r) 78,000) (gp78) for an autocrine motility factor, which has been implicated in invasion and metastasis. Treatment of murine melanoma cell lines S91-C2, B16-F1, and K1735-P with RA (10 microM) for 5 days decreased the level of gp78 by 37, 72, and 92%, respectively, as revealed by immunoblotting with monoclonal antibodies raised against gp78. In contrast, RA had only a limited effect on gp78 levels in melanoma cell clones or variant cell lines that are resistant to the growth-inhibitory effects of RA (S91-C154, B16-F10, and K1735-Cl19). Further studies with K1735-P, the most sensitive cell line with respect to modulation of gp78, showed that the decrease in gp78 level required at least 1 microM RA and 4 to 5 days of treatment. The binding of anti-gp78 antibodies to the surface of intact RA-treated cells and to intracellular gp78 in permeabilized cells was also lower than in untreated cells. Furthermore, RA treatment decreased the induction of cell motility, on colloidal gold-coated glass coverslips, by anti-gp78 antibodies, which mimic the effect of autocrine motility factor. The RA-induced decrease in antibody-enhanced cell motility was similar to the time- and RA concentration-dependent decrease in the amount of gp78, suggesting that the two events are related. These results raise the possibility that the previously reported suppression by RA of tumor cell invasion and metastasis may be related, at least in part, to suppression of cell motility resulting from the decreased level of the autocrine motility factor receptor.
β-全反式维甲酸（RA）已被证明可抑制某些人源和鼠源黑色素瘤细胞的生长、促进其分化，并抑制其转化和转移特性。本研究检测了RA对一种自分泌运动因子的细胞表面受体（分子量78,000）（gp78）水平的影响，该受体与侵袭和转移有关。用RA（10微摩尔）处理鼠源黑色素瘤细胞系S91-C2、B16-F1和K1735-P 5天，通过用针对gp78的单克隆抗体进行免疫印迹分析发现，gp78水平分别降低了37%、72%和92%。相比之下，RA对黑色素瘤细胞克隆或对RA生长抑制作用有抗性的变异细胞系（S91-C154、B16-F10和K1735-Cl19）中的gp78水平影响有限。对gp78调节最敏感的细胞系K1735-P进行的进一步研究表明，gp78水平的降低至少需要1微摩尔RA和4至5天的处理。抗gp78抗体与完整的经RA处理细胞表面以及通透细胞内的gp78的结合也低于未处理细胞。此外，RA处理降低了抗gp78抗体在胶体金包被的玻璃盖玻片上诱导的细胞运动，抗gp78抗体可模拟自分泌运动因子的作用。RA诱导的抗体增强细胞运动的降低与gp78量的时间和RA浓度依赖性降低相似，表明这两个事件相关。这些结果提示，先前报道的RA对肿瘤细胞侵袭和转移的抑制作用可能至少部分与自分泌运动因子受体水平降低导致的细胞运动抑制有关。
