EXPRESSION OF 2 TYPE II-LIKE TUMOR HEXOKINASE RNA TRANSCRIPTS IN CANCER CELL-LINES

To maintain an elevated glycolytic rate, cancerous or proliferating ce lls alter the expression pattern of rate limiting glycolytic enzymes. Since glucose phosphorylation is the first step in glycolysis, hexokin ase (HK), the first rate limiting glycolytic enzyme, can play a key re gulatory role in this process. A low-Km, mitochondrial type II-like tu mor HK is described as the predominant form in hepatomas. However, rec ent identification of a high-Km glucose phosphorylating activity in a range of cancer cells prompted us to characterize glucose phosphorylat ing enzymes of cancer cells at the molecular level. Highly sensitive r everse-transcription polymerase chain reaction identifies an induction and overexpression of a type II-like tumor HK RNA in a range of cance r cell lines irrespective of tissue origin. In addition, we report her e the identification of two RNA transcripts of type II-like tumor HK o f similar to 5.5 and similar to 4.0 kb in these cancer cells lines, in cluding muscle-derived L6 myoblast cells. Interestingly, under normal conditions muscle cells express only a similar to 5.5-kb type II HK RN A transcript. A significant amount of type I HK RNA was also found exp ressed in cancer cell lines. RNA encoding glucokinase (GK), the high-K m HK isozyme, was found only in cancer cells originating from liver an d pancreas, which express GK under normal conditions.