Insulin-like growth factor I induces tumor hexokinase RNA expression in cancer cells.

Increased glycolysis is a characteristic of cancer cells. Though less efficient in energy production, it ensures continuous supply of energy and phosphometabolites for biosynthesis enabling metastatic and less vascularized cancer cells to proliferate even under hypoxic conditions. Since hexokinase is the first rate limiting enzyme in the glycolytic pathway, elevated levels of Type II like hexokinase in tumors are of great significance in this context. Under normal conditions insulin regulates expression of hexokinase Type II isoenzyme, which is predominantly expressed in muscle. On the other hand cancer cells overexpress insulin-like growth factors and their receptors which mimic many activities of insulin. This prompted us to examine a hypothesis that insulin-like growth factors may be responsible for overexpression of tumor hexokinase. Our experiments demonstrate that insulin-like growth factor I indeed induces hexokinase gene expression in a concentration and time dependent manner in two cancer cell lines we studied.