Detection of MAGE-4 protein in sera of lung cancer patients.

We investigated the level of MAGE-4 protein in sera of patients with primary lung cancer to understand better the biological roles of the MAGE proteins. MAGE-4 protein was detected as a non-degraded form in both the supernatant of a MAGE-4+ tumor cell line and in a patient's serum. Serum level of the MAGE-4 protein in lung cancer patients (n=100, mean=1.17 ng/ml) was significantly higher than that in either patients with benign pulmonary diseases (n=80, 0.33 ng/ml) or healthy donors (n=68, 0.32 ng/ml). It was higher than the cutoff level (1.15 ng/ml) in 34 of 100 cancer patients, but not in anyone in the other groups.