Ashida Y, Ueno A, Miwa Y, Miyoshi K, Inoue H
Department of Biochemistry, School of Dentistry, Tokushima University.
Jpn J Cancer Res. 1998 Jan;89(1):67-75. doi: 10.1111/j.1349-7006.1998.tb00481.x.
Our previous study showed that treatment of highly invasive rat ascites hepatoma (LC-AH) cells with alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, decreased both their intracellular level of putrescine and their in vitro invasion of a monolayer of calf pulmonary arterial endothelial (CPAE) cells, and that both these decreases were completely reversed by exogenous putrescine, but not spermidine or spermine. Here we show that all adhering control (DFMO-untreated) cells migrated beneath CPAE monolayer with morphological change from round to cauliflower-shaped cells (migratory cells). DFMO treatment increased the number of cells that remained round without migration (nonmigratory cells). Exogenous putrescine, but not spermidine or spermine, induced transformation of all nonmigratory cells to migratory cells with a concomitant increase in their intracellular Ca2+ level, [Ca2+]i. The putrescine-induced increase in their [Ca2+]i preceded their transformation and these effects of putrescine were not affected by antagonists of the voltage-gated Ca2+ channel, but were completely suppressed by ryanodine, which also suppressed the invasiveness of the control cells. The DFMO-induced decreases in both [Ca2+]i and the invasiveness of the cells were restored by thapsigargin, which elevated [Ca2+]i by inhibiting endoplasmic Ca2+-ATPase, indicating that thapsigargin mimics the effects of putrescine. These results support the idea that putrescine is a cofactor for Ca2+ release through the Ca2+ channel in the endoplasmic reticulum that is inhibited by ryanodine, this release being initiated by cell adhesion and being a prerequisite for tumor cell invasion.
我们之前的研究表明，用鸟氨酸脱羧酶抑制剂α-二氟甲基鸟氨酸（DFMO）处理高侵袭性大鼠腹水肝癌（LC-AH）细胞，可降低其细胞内腐胺水平以及其对单层小牛肺动脉内皮（CPAE）细胞的体外侵袭能力，且这两种降低作用均可被外源性腐胺完全逆转，但亚精胺或精胺则无此作用。在此我们发现，所有贴壁的对照（未用DFMO处理）细胞在CPAE单层下方迁移，细胞形态从圆形变为菜花状（迁移细胞）。DFMO处理增加了保持圆形不迁移的细胞数量（非迁移细胞）。外源性腐胺而非亚精胺或精胺可诱导所有非迁移细胞转变为迁移细胞，同时其细胞内钙离子水平[Ca2+]i升高。腐胺诱导的[Ca2+]i升高先于其转变，且腐胺的这些作用不受电压门控钙离子通道拮抗剂的影响，但可被ryanodine完全抑制，ryanodine也抑制对照细胞的侵袭能力。DFMO诱导的细胞[Ca2+]i降低和侵袭能力降低可被毒胡萝卜素恢复，毒胡萝卜素通过抑制内质网Ca2+-ATP酶升高[Ca2+]i，表明毒胡萝卜素模拟了腐胺的作用。这些结果支持以下观点：腐胺是通过内质网中被ryanodine抑制的钙离子通道释放钙离子的辅助因子，这种释放由细胞黏附引发，是肿瘤细胞侵袭的前提条件。
