BCH에 의한 구강암세포 성장억제기전에서 세포주기조절인자의 영향

Abstract

Objectives : Amino acid transporters are essential for the growth and proliferation in all living cells. Among the amino acid transporters, the system L amino acid transporters are the major nutrient transport system responsible for the Na+-independent transport of neutral amino acids including several essential amino acids. The system L is divided into two major subgroups, the L-type amino acid transporter 1 (LAT1) and the L-type amino acid transporter 2 (LAT2). The LAT1 is highly expressed in cancer cells to support their continuous growth and proliferation. 2-Aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) is a model compound for study of amino acid transporter as a system L selective inhibitor. The purpose of this study was to examine the effect of BCH on cell growth suppression in KB human oral epidermoid carcinoma cells and the influence of cell cycle regulatory factors in growth inhibition mechanism of KB cells by BCH. Materials and methods : The effect of BCH on cell growth suppression and the influence of cell cycle regulatory factors in KB cells were examined using MTT analysis and immunoblotting. Results : The growth of KB cells was inhibited by BCH in a concentration- and a time-dependent manner. The expression of cyclin D1 by BCH treatment was not different from the control group in KB cells. However the expression of cyclin D3 was remarkably decreased by BCH treatment. Furthermore, BCH inhibited the expression of cyclin-dependent protein kinase 6 (CDK6) in a time-dependent manner. In addition, the expression of CDK inhibitor p27 was increased by BCH treatment in KB cells, but not CDK inhibitors p21 and p15. Conclusions : These results suggest that the BCH inhibits the growth of KB cells through the intracellular depletion of neutral amino acids for cell growth induced by inhibition of LAT1 activity. In addition, these results suggest that the BCH arrests the G1 phase of cell cycle through the inhibition of cyclin D3-CDK6 complex expression for cell cycle progression induced by increase of p27 expression in KB cells.