Inhibition of junctional intercellular communication as a possible short-term test to detect tumor-promoting agents: results with nine chemicals tested by dye transfer assay in Chinese hamster V79 cells

Abstract

In an attempt to establish an in vitro short-term test to detect tumor-promoting agents, we studied the effects of these agents on junctional intercellular communication in cultured Chinese hamster V79 cells using a microinjection-dye transfer technique. When Lucifer Yellow CH solution is injected into a cell, the average number of cells that become fluorescent after 10 min is 11.6 +/- 7.8 (SD). When the phorbol ester 12-O-tetradecanoylphorbol-13-acetate was used as a positive control, the extent of dye transfer was reduced to 2.9 +/- 2.1 cells within 2 h after incubation with 12-O-tetradecanoylphorbol-13-acetate (100 ng/ml). Nine chemicals that have been reported to have or suspected of having tumor-promoting activity in experimental animals were tested at different doses and after different incubation times. 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane, lindane (1,2,3,4,5,6-hexachlorocyclohexane), phenobarbital, and butylated hydroxyanisole showed inhibitory properties in V79 cells, but with kinetics different from that of 12-O-tetradecanoylphorbol-13-acetate. With 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane and lindane, exposure for 24 h resulted in full blockage of dye transfer; with phenobarbital, a treatment time of 96 h was necessary to achieve this effect, and butylated hydroxyanisole was more active after 48 h than after 24 or 72 h incubation. Five of the reported or suspected tumor-promoting agents, benzoyl peroxide, anthralin, deoxycholic acid, lithocholic acid, and butylated hydroxytoluene, had no effect on communication between V79 cells at noncytotoxic doses; deoxycholic acid, lithocholic acid, and butylated hydroxytoluene but not anthralin inhibited communication only at cytotoxic doses. Our results indicate that we can detect several, but not all, types of tumor-promoting agents, using microinjection-dye transfer assay of junctional communication between Chinese hamster V79 cells.