Tissue polypeptide antigen as a tumor marker of brain tumors

Abstract

Tissue polypeptide antigen (TPA), a tumor associated antigen and first described in 1957 by Bjorklund et al., is a surface antigen and has an approximate molecular weight between 20, 000 and 45, 000. TPA is a single-chain polypeptide having 4 subfractions, and is released from propagating cells. TPA in serum, cerebrospinal fluid (CSF) or intratumoral cystic fluid of patients with brain tumor was assayed by the radioimmunoassay technique and found quite useful as a brain tumor marker. TPA level in serum was significantly elevated in patients with glioblastoma, metastatic brain tumor, malignant lymphoma and pituitary adenoma. TPA was elevated in malignant tumors, probably because more TPA was produced in propagating tumor cells. However, elevated TPA levels were also found in non-malignant diseases, for example, hepatitis and infection. Therefore, elevation of the TPA level should be considered indicative of a brain tumor when other diseases can be excluded. TPA in serum was found useful for differentiating glioblastoma and metastatic brain tumor. If TPA level in serum exceeded 150 U./l, it was more likely a metastatic brain tumor. TPA level in cystic fluid was elevated in metastatic brain tumor, craniopharyngioma and pineal teratocarcinoma, and it was suggested that TPA was increased in tumors of epithelial origin. TPA in the CSF was not noticeable in normal CSF, but was markedly elevated in meningeal carcinomatosis. TPA in CSF was positive in 13 (81%) out of 16 patients of brain tumors with proven leptomeningeal dissemination, and leptomeningeal dissemination was verified in 13 (68%) out of 19 patients with positive TPA in CSF. TPA in CSF is considered quite useful in clinical observation of brain tumors.