Macro--creatine kinase 2: a possible marker of gastrointestinal cancer?

Creatine kinase (CK) is an enzyme found in many body organs. It is used clinically in the diagnosis of myocardial infarction. Recently an atypical isoenzyme, macro-CK2, not found in the sera of healthy individuals, has been reported in patients with gastrointestinal malignancies. This study is a report of our findings in serum samples obtained from 200 patients from November 1981 until December 1982. Twenty-eight patients had gastrointestinal complaints but did not have malignant disease. One hundred seventy-two patients had malignancy. Samples of serum were studied for macro-CK2 with a standard laboratory agarose gel electrophoresis technique. The tests were done without knowledge of the patients' diagnoses. The results show no detectable macro-CK2 in sera from patients without malignancy. It was present before operation in nine of 13 patients with colorectal cancer and 16 of 21 patients with metastases from colorectal cancer or gastric cancer. This preliminary study suggests that the presence of macro-CK2 in serum may be an indicator of malignancy of the gastrointestinal tract and in particular of colorectal cancer.