Differential inhibition of single and cluster type tumor cell migration

For the control of tumor metastasis it is important to identify chemical compounds with antimigratory potency. Agents acting against single cell and cluster type migration are necessary for successful antimetastatic therapy. In the present study, the migration of HT-1080 fibrosarcoma cells and OSCORT osteosarcoma cells was compared in a Boyden chamber and in an extracellular matrix (ECM)-based three-dimensional cell culture (3-DCC) model system. The Boyden chamber offers a model of single tumor cell migration, whereas the 3-DCC model system demonstrates invasive growth in the form of a cluster. Since PD98059 (MEK inhibitor) exclusively reduced migration in the 3-DCC model, it may be plausible that the ERK/MAPK signaling pathway is essential for cluster type migration. Interestingly, single cell migration was stimulated upon blocking phosphatidylinositol 3-kinase (PI3K) and also p38-MAPK by treatment with LY294002 and SB203580 respectively. A remarkable reduction of single cell migration was observed following treatment with okadaic acid, a phosphatase 1 (PP1) and 2A (PP2A) inhibitor, which was rather intriguing. This study provided evidence that certain cytotoxic/cytostatic agents at appropriate concentrations were able to preferentially inhibit certain types of migration relative to cell proliferation. Single cell migration was selectively inhibited by taxol at very low subtoxic concentration, whereas 5-hexyl-2'-deoxyuridine (HUdR) exclusively inhibited the cluster type of migration. The borrelidin compound was able to inhibit both types of tumor cell migration, but single tumor cell migration was much less affected. It is interesting that migration was more reduced than proliferation by borrelidin, especially at the advanced growth stage. Taxol is recommended as an agent acting against single cell migration, as well as HUdR and borrelidin as leading compounds for developing antimetastatic drugs against cluster type migration.