GLUCOSE CATABOLISM IN CANCER-CELLS - ISOLATION, SEQUENCE, AND ACTIVITY OF THE PROMOTER FOR TYPE-II HEXOKINASE

One of the most characteristic phenotypes of rapidly growing cancer ce lls is their propensity to catabolize glucose at high rates. Type II h exokinase, which is expressed at high levels in such cells and bound t o the outer mitochondrial membrane, has been implicated as a major pla yer in this aberrant metabolism. Here we report the isolation and sequ ence of a 4.3-kilobase pair proximal promoter region of the Type II he xokinase gene from a rapidly growing, highly glycolytic hepatoma cell line (AS-30D). Analysis of the sequence enabled the identification of putative promoter elements, including a TATA box, a CAAT element, seve ral Sp-1 sites, and response elements for glucose, insulin, cAMP, Ap-1 , and a number of other factors. Transfection experiments with AS-30D cells showed that promoter activity was enhanced 3.4-, 3.3-, 2.4-, 2.1 -, and 1.3-fold, respectively, by glucose, phorbol 12-myristate 13-ace tate (a phorbol ester), insulin, cAMP, and glucagon. In transfected he patocytes, these same agents produced little or no effect. The results emphasize normal versus tumor cell differences in the regulation of T ype II hexokinase and indicate that transcription of the Type II tumor gene may occur independent of metabolic state, thus, providing the ca ncer cell with a selective advantage over its cell of origin.