Effects of okadaic acid on cell growth,anchorage-independent growth,and co-cultures of normal (KMS-6), immortalized (KMST-6), and neoplastically transformed (KMST-6T and KMST-6/RAS) human fibroblasts

The effects of okadaic acid (OA) on normal human (KMS-6), its immortalized (KMST-6) and neoplastically transformed (KMST-6T and KMST-6/RAS) cells were investigated as a model of two-stage carcinogenesis. The presence of OA inhibited cell growth of the normal and immortalized cells but not that of the neoplastic KMST-6T cells. In contrast, cell growth of the other neoplastic KMST-6/RAS cells transformed with the Ha-ras oncogene was inhibited by OA. OA enhanced colony formation of KMST-6T cells in soft agar, but it suppressed that of KMST-6/RAS cells. Co-cultures of KMST-6T cells with normal KMS-6 cells showed an increase in focus formation of KMST-6T cells in the presence of OA, whereas focus formation of KMST-6/RAS cells decreased. These results indicate that OA has growth-promoting effects on certain types of transformed human cells.Abbreviation OA okadaic acid This work was supported by a grant-in-aid from the Ministry of Education, Science, Culture and Sports of Japan