TECHNICAL EVALUATION OF THYMIDINE KINASE ASSAY IN CYTOSOLS FROM BREAST CANCERS

Pilot retrospective studies have pointed to the prognostic value of th ymidine kinase (TK) in breast cancer. We studied the Prolifigen TK-REA assay (Sangtec Medical, Sweden), usually applied to serum, for TK ana lysis in breast cancer cytosols. Reproducibility was good, provided th at small volume pipetting was performed carefully. The TK assay was no t influenced by the short-term storage of cytosols in liquid nitrogen or at -80 degrees C. However, some steps appeared critical for good la boratory practice. The TK level was affected by thawing the cytosols m ore than twice. Tumour storage in liquid nitrogen should be preferred over storage at -80 degrees C. The components of the homogenisation bu ffer, especially sodium molybdate and KCl can have a marked influence on results. Finally, linearity problems arose with some cytosols. Thus , although assay of TK in cytosols is aparently simple, care must be t aken in practice. The TK-REA kit should be standardised before widespr ead use in breast cancer.