Differentiating effects of 1,25-dihydroxycholecalciferol (D3) on LA-N-5 human neuroblastoma cells and its synergy with retinoic acid.

PURPOSE

1,25-Dihydroxycholecalciferol (D3) plays an important role in embryonic development and cell differentiation. It has previously been reported to decrease c-myc expression by HL-60 cells and downregulate c-myc expression by breast and ovarian cancer cells. We report the results of our investigations into the differentiating effects of D3 on LA-N-5 human neuroblastoma cells.

METHODS

LA-N-5 human neuroblastoma cell line was treated with D3, retinoic acid (RA), D3 and RA, or solvent control. Growth inhibitory effects, neurite extension, acetylcholinesterase activity, invasiveness, motility, and N-myc protein expression were examined following treatment.

RESULTS

Growth inhibition was observed at concentrations of > 24 nM. D3 stimulated the differentiation of LA-N-5 cells as demonstrated by increased neurite outgrowth, increased acetylcholinesterase activity, and decreased invasiveness. A decrease in N-myc expression was observed in immunostained cells treated with either agent alone, with a more profound effect appreciated with the combination.

CONCLUSION

Vitamin D3 decreases N-myc expression in LA-N-5 human neuroblastoma cells, with extended treatment causing growth inhibition and differentiation. When used in combination with RA, these effects are more profound than with either agent alone. The therapeutic use of differentiating agent combinations such as D3 and RA may provide a relatively nontoxic means of treating susceptible tumor types.