Forest insect cell lines responsive to 20-hydroxyecdysone and two nonsteroidal ecdysone agonists, RH-5849 and RH-5992

Abstract The effects of 20-hydroxyecdysone (20E) and two substituted dibenzoylbutylhydrazines, RH-5849 and RH-5992, were investigated in vitro using three forest insect cell lines. Two of these cell lines, IPRI-MD-66 (MD-66) from the forest tent caterpillar, Malacosoma disstria and IPRI-CF-1 (CF-1) from the spruce budworm, Choristoneura fumiferana , grow freely suspended, whereas the cells of the third line, FPMI-CF-70 (CF-70) from C. fumiferana , stay attached to the culture flask. MD-66 cells responded to all three compounds by forming clumps and by producing filamentous extensions. In addition, these compounds produced increased cell attachment and reduced cell proliferation in this cell line. CF-70 cells also responded to all three compounds although to a lesser extent. On the other hand, CF-1 cells showed little or no morphological response. The above effects of RH-5992 on MD-66 cells were both dose and time dependent. This compound also induced the expression of the Malacosoma disstria hormone receptor (MdHR3) in these cells in a dose dependent manner, as was the case with 20E. This result indicated that the effect of RH-5992 on MD-66 cells is specific and related to their response to 20E. These phenotypic and molecular observations indicate that MD-66 cells and RH-5992 will be an excellent in vitro model system for studying the mode of action of ecdysteroid agonists.