Effects of retinoic acid on cell differentiation and reversion toward normal in human endometrial adenocarcinoma (RL95-2) cells.

BACKGROUND

All-trans retinoic acid is currently used in clinical trials in combination with tamoxifen to treat breast cancer, and 13-cis retinoic acid is used with a-interferon to treat metastatic endometrial cancer. We examined the effects of all-trans retinoic acid and 13-cis RA alone on endometrial adenocarcinoma (RL95-2) cells to investigate the cell biological mechanisms by which retinoic acid may reduce the metastatic phenotype and induce differentiation.

METHODS

RL95-2 cells were seeded onto 4-chamber plastic slides and treated with 13-cis retinoic acid or all-trans retinoic at 0.5 microM, 1 microM and 5 microM doses for 90 minutes at 37 degrees C and stained for F-actin.

RESULTS

Untreated RL95-2 cells exhibited staining of disrupted aggregates of F-actin only near the cell periphery. Cells treated with the three doses of 13-cis retinoic acid exhibited a dramatic reorganization of F-actin throughout the cells. When cells were treated with 0.5 microM all-trans retinoic acid, actin filaments reorganized. Cells treated with 1 microM all-trans retinoic acid and 5 microM all-trans retinoic acid displayed increased organization of F-actin and cell size increased. The percentage of S-phase cells increased at the high doses of retinoic acid treatment. This effect was apparently transient, since retinoic acid did not significantly affect cell growth.

CONCLUSION

An organized cytoskeleton and an increase in cell size are associated with differentiation. We suggest that retinoic acid exerts its effects on these transformed cells by reorganizing actin filaments, and inducing differentiation, thus inducing a more stationary phenotype.