Explore a method to measure the threshold of the effective or cytotoxity of trans-retinoic acid on nasopharyngeal carcinoma cells in vitro

Aim: To explore a method to measure the thresholds of the effective or cytotoxity of trans-retinoic acid on nasopharyngeal carcinoma cells in vitro. Methods: The nasopharyngeal carcinoma cell line(CNE) was suspended and cultured in RPMI-1640 medium containing 10% fetal serum and a series ratio concentration (10~(-3)～10~(-9) mol/L) of trans-retinoic acid (TRA) to give a final concentration then comparatively studied on the cloning plating efficiency and the cell doubling growth efficiency in vitro. Results: The effects of trans-retinoic acid on the cloning plating efficiency and the cell doubling growth efficiency of nasopharyngeal carcinoma cells were changed at a different concentration of TRA: compared with that of the control group (c(TRA)=0 mol/L), the cell doubling growth efficiency which was demonstrated positively consistent correlation to the cell proliferation was inhibited insignificantly at or below a concentration of 10~(-6) mol/L(P0.05) but significantly at a concentration of 10~(-5) mol/L (P0.05), and the cloning plating efficiency which was demonstrated negative consistent correlation to the cell differentiation was inhibited insignificantly below a concentration of 10~(-6) mol/L (P0.05) but significantly at or above a concentration of 10~(-6) mol/L (P0.01). The results indicated: The inhibition of the cloning plating efficiency on nasopharyngeal carcinoma cells induced by the concentration of 10~(-6) mol/L of trans-retinoic acid may be resulted in the cell differentiation, and that was a effective threshold; On the other hands, the inhibition of the cell cloning growth efficiency on nasopharyngeal carcinoma cells induced by the concentration of 10~(-5) mol/L of trans-retinoic acid may be resulted in cytotoxity, and that was a cytotoxic threshold. Conclusion: The cytotoxic threshold and the effective threshold of trans-retinoic acid were different in the experiment. It was suggested that identifying the concentration between the (cytotoxic) threshold and the effective threshold could provide a method to the proper application of trans-retinoic acid in the clinic or the research field.