Thymidine kinase in extracts of human brain tumours.

Deoxythymidine kinase (TK) is an enzyme involved in DNA synthesis. It can be used as a marker of cell proliferation. TK was measured in extracts of human brain tumours and non-neoplastic brain tissue. In astrocytomas the mean TK activity increased with increasing grade of malignancy. Oligodendrogliomas showed higher TK activity than astrocytomas. The highest activities were noted in menigiomas, of which the recurrent ones exceeded the primary in TK activity. In non-neoplastic brain tissue lower TK activity was found. It is concluded that TK can be measured in human brain tumour extracts, and is potentially of use for studies on tumour cell proliferation.