Source of elevated serum mitochondrial creatine kinase activity in patients with malignancy

Mitochondrial creatine kinase (CK-mit) is increased in cancer tissues of the digestive tract. There is no difference in molecular weight, electrophoretic and kinetic properties between the isoenzymes extracted from the tumor and those from the adjacent normal tissues. High non-CK-M/total CK activity ratios in some sera from cancer patients probably reflect leakage of CK-mit from the tumor tissues.