The Role of Alkaline Phosphatase Isoenzymes as Tumor Markers for Testicular Germ Cell Tumors

Abstract

The role of serum alkaline phosphatase as a tumor marker for testicular germ cell disease was investigated in 26 patients with testicular seminoma and 13 with nonseminomatous germ cell testis tumors. Placental alkaline phosphatase-like enzyme was elevated in 50% of the stage I seminoma patients and in all patients with stages II to III disease. In addition, liver (tissue unspecific) alkaline phosphatase was elevated in 10 and 83% of the patients, respectively. Lactic dehydrogenase and β-human chorionic gonadotropin (β-HCG) were detected in 50 to 60% of the patients with stage I seminoma. By combining placental alkaline phosphatase-like enzyme, lactic dehydrogenase and β-HCG, 75% of the stage I and 100% of the stages II and III seminoma patients could be identified correctly. Placental alkaline phosphatase-like enzyme in serum also occurred with nonseminomatous germ cell tumor but less frequently, while liver alkaline phosphatase was not detected at all. Thus, placental alkaline phosphatase-like enzyme and liver alkaline phosphatase were predominantly determined in the serum of patients with seminoma.In studies of tumor tissues from 31 of these patients, those with normal serum placental alkaline phosphatase-like enzyme levels had significantly lower tissue placental alkaline phosphatase-like enzyme levels than patients with elevated serum levels (p <0.01). Seminoma tissues showed significantly higher levels of placental alkaline phosphatase-like enzyme and liver alkaline phosphatase than nonseminomatous germ cell tumors (p <0.01), explaining the infrequent elevation of serum placental alkaline phosphatase-like enzyme and liver alkaline phosphatase found in patients with nonseminomatous germ cell tumors.