[A study of thymidine kinase activity in lung cancer tissue]

In order to investigate the usefulness of thymidine kinase, which acts to salvage thymidine to its nucleotide for DNA biosynthesis, as a marker of malignancy in lung cancer, the enzyme activities in extracts of tumors and uninvolved lungs of 83 resected cases of lung cancer were determined. The mean value of thymidine kinase activity in tumors was as much as 4.3 times higher than that of uninvolved lungs. There was no significant correlation between the activity in tumors and clinicopathological findings such as histological type, the grade of histological differentiation, pT factor, pN factor, pTNM stage and tumor size. The tumor doubling time did, however, show a significant inverse correlation with activity when compared logarithmically (r = 0.879, p = 0.00002). Moreover, there was a significant relationship between enzyme activity and post-operative recurrence of lung cancer. In conclusion, thymidine kinase was found to be a useful marker of malignancy in lung cancer.