CDKN1B and breast cancer: Moderate increase in the concentration of D-(+)-glucose down-regulated the expression of p27, and, conversely, deficiency of D-(+)-glucose, L-leucine, L-methionine, L-cysteine or combination of L-methionine and L-cysteine up-regulated the expression of p27 in human MDA-MB-231 breast cancer cells in vitro