The proliferation marker thymidine kinase 1 in clinical use

Muscle-invasive bladder cancer is characterized by overexpression of thymidine kinase 1

OBJECTIVE

Thymidine kinases have an important role in the synthesis of DNA and exhibit high activity in rapidly proliferating cells. Thymidine kinase 1 (TK1) activity has been shown to be increased in various cancer types and proposed as a prognostic parameter. Aim of the present study was to investigate TK1 in muscle-invasive urothelial carcinoma (UC).

METHODS

Corresponding UC and benign samples from paraffin embedded tissue of 111 patients treated with cystectomy for invasive UC from 1996 to 2006 were immunohistochemically (IHC) assessed for TK1. IHC expression patterns were evaluated in a semiquantitative fashion by 2 independent reviewers. Localization of staining was categorized into pure nuclear and additional cytoplasmic localization. Uni- and multivariate analyses were performed to assess differential expression in normal and UC tissue and to evaluate the diagnostic and predictive capability of TK1 by correlation to clinical data. To correlate TK1 expression with molecular subtypes of UC, analysis of TK1 RNA expression levels of the Cancer Genome Atlas UC cohort was performed.

RESULTS

TK1 was significantly overexpressed in invasive UC, compared to benign urothelium (P<0.0001), and cytoplasmic expression was more often found in cancer tissue than in benign tissue (P = 0.0001). No correlations of TK1 protein expression patterns to standard histopathological determinants were detected. In univariate analysis, TK1 nuclear and cytoplasmic expression was associated with improved cancer-specific survival (P = 0.0119). However, only metastasis status and histologic grade were identified as independent predictors of cancer-specific survival in multivariate analysis. TK1 expression was merely found in the basal layers of benign urothelium. RNA overexpression of TK1 could be correlated to the biologically more aggressive basal UC subtype.

CONCLUSIONS

TK1 expression is significantly different in invasive UC and benign urothelium, which underlines its potential as a diagnostic marker. Although TK1 is considered to be a marker of proliferation, and TK1 RNA overexpression is associated with an aggressive UC subtype, its capability as a predictive IHC biomarker for invasive UC remains limited.

Serum thymidine kinase 1 is a reliable maker for the assessment of the risk of developing malignancy: A case report

With regard to different types of malignancies, thymidine kinase 1 (TK1) is a useful prognostic marker in clinical oncology, both as a serum proliferation marker and in immunohistochemistry. The present study investigated the use of serum TK1 protein (STK1p) for the identification of multiple proliferating diseases linked to the risk of developing cancer, by following one patient during the period of 2003-2014. The patient presented with adenomatous polyps in the stomach in 2003, follicular cervicitis in 2007 and hyperplasia of the breast/fibrocystic breasts in 2010. The breast cysts increased from 4×5 mm in size in 2010 to 8×7 mm in size in 2013, and were assessed as a suspicious malignancy at the end of this period. In parallel, the STK1p values increased from 2.0 to 7.6 pM. Based on this information, a minimally invasive surgery using the Mammotome® Biopsy System was performed. Immunohistochemistry on the cyst tissue showed strong staining of TK1 in the ductal epithelial cells and thus confirmed the abnormal proliferation in the lesion. One week after the surgery, the STK1p value had decreased to almost normal values (1.6 pM), but then fluctuated above 2.0 pM for the next 7 months. After the surgery, the patient was re-examined and small foci with squamous cell hyperplasia and a suspected ulcerated cervix, as well as flat gastric erosive, were identified, but not treated; this may explain why the STK1 P-values did not return to within normal values. The patient is currently being followed up using STK1p analysis combined with imaging/pathology in order to begin therapeutic intervention as early as possible to avoid the risk of developing cancer. Overall, STK1p is useful in health screening to identify individuals at risk of developing premalignancy/malignancy.

Breast and prostate cancer patients differ significantly in their serum Thymidine kinase 1 (TK1) specific activities compared with those hematological malignancies and blood donors: implications of using serum TK1 as a biomarker

Background

Thymidine kinase 1 (TK1) is a cellular enzyme involved in DNA precursor synthesis, and its activity has been used as a proliferation marker for monitoring malignant diseases. Here, for the first time, we evaluated both TK1 activity and protein levels in sera from patients with different malignancies.

Methods

Serum samples from patients with myelodysplastic syndrome (MDS, n = 22), breast cancer (n = 42), prostate cancer (n = 47) and blood donors (n = 30) were analyzed for TK1 protein and activity levels, using a serum TK1 (STK1) protein assay based on antibodies and an activity assay that measured [³H]-deoxythymidine (dThd) phosphorylation. The molecular forms of TK1 in sera from some of these patients were analyzed using size-exclusion chromatography.

Results

Mean STK1 activities in sera from MDS, breast and prostate cancer were 11 ± 17.5, 6.7 ± 19 and 1.8 ± 1.4 pmol/min/mL, differing significantly from blood donors (mean ± standard deviation (SD) = 1.1 ± 0.9 pmol/min/mL). Serum TK1 protein (25 kDa polypeptide) levels were also significantly higher in MDS, breast, prostate cancer compared to blood donors (mean ± SD = 19 ± 9, 22 ± 11, 20 ± 12, and 5 ± 3.5 ng/mL, respectively). The STK1 specific activities of sera from patients with MDS and blood donors were significantly higher when compared with activities in sera from breast and prostate cancer patients. Size-exclusion analysis of sera from breast and prostate cancer showed that the detected active TK1 was primarily a high molecular weight complex, similar to the forms found in sera from MDS patients and blood donors. However, Western blotting demonstrated high TK1 25 kDa protein levels in fractions lacking TK1 activity in sera from cases with breast and prostate cancer.

Conclusions

These results demonstrate that there are differences in the specific activities and the subunit compositions of STK1 in hematological malignancies compared with breast and prostate cancer. This fact has several important implications for the use of STK1 as a tumor biomarker. One is that STK1 protein assays may differentiate early-stage tumor development in breast and prostate cancer more effectively than STK1 activity assays.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1073-8) contains supplementary material, which is available to authorized users.

Thymidine kinase 1 is a better prognostic marker than Ki-67 for pT1 adenocarcinoma of the lung

OBJECTIVES

The sensitivity and reliability of the biomarkers thymidine kinase 1 (TK1) and Ki-67 were studied in relation to clinical features and prognosis of survival for pathological-T1 (pT1) lung adenocarcinoma patients.

METHODS

TK1 and Ki-67 expression was determined in 80 patients with pT1 adenocarcinoma of the lung and in 20 specimens from normal lung tissues, using immunohistochemistry.

RESULTS

TK1 was found in most lung tumor cells both in the cytoplasm and the nuclei. The positive labelling index (LI) for total TK1 was significantly higher than that for Ki-67. There was a significant correlation between the LI of total TK1 and lymph node metastasis, degree of tumor invasion and pathologic stages, which was not found for Ki-67. In addition, the overall 5-year survival of patients was statistically significant different between low and high levels of TK1 expression, but not in cases of Ki-67. A multivariate analysis revealed that expression of TK1, lymph node involvement and TNM pathology staging could serve as independent prognostic factors for the disease progression of pT1 lung adenocarcinoma patients.

CONCLUSIONS

Compared with Ki-67, TK1 is a more reliable proliferation index in pT1 adenocarcinoma of lung, which can evaluate the invasion and the prognosis of tumor.

Serum thymidine kinase activity: analytical performance, age-related reference ranges and validation in chronic lymphocytic leukemia

Background

To date no age-related reference ranges are available for serum thymidine kinase (TK1) activity. Being a proliferation marker, it may be used as a prognostic marker in malignant diseases, including chronic lymphocytic leukemia (CLL). Our aim was to establish age-specific reference ranges for TK1 and examine its utility as a screening marker in CLL, a disease of the elderly.

Methods

Serum TK1 activity was measured by a competitive chemiluminescent immunoassay in 369 healthy adults and 115 de novo CLL patients.

Results

We observed a statistically significant decline in TK1 activity from young (18–35 years) to middle-aged (36–60 years) and further on to elderly (60–86 years) healthy individuals. Age-related reference range was: <30 U/L for young, <25 U/L for middle-aged and <19 U/L for elderly. There was no difference in TK1 activity between the studied healthy men and women. In CLL patients, TK1 activity was the highest in the advanced Rai stages. The area under the receiver operating characteristic curve (ROC-AUC) for TK1 was 0.840 (95% CI: 0.787–0.892), for differentiating CLL patients from age and sex matched healthy controls, with a cut-off value of 10.5 U/L (sensitivity: 80.9%, specificity: 73.4%). TK1 was significantly elevated in CD38+/Zap70+ CLL patients, and showed significant correlation with WBC and absolute B-cell count.

Conclusion

In the healthy, serum TK1 activity does not differ in the two sexes but declines significantly with age. As such, use of age-related reference ranges is warranted, especially when evaluating CLL patients who generally belong to the elderly age group.

Serum thymidine kinase 1 levels predict cancer-free survival following neoadjuvant, surgical and adjuvant treatment of patients with locally advanced breast cancer

In this study, the use of serum thymidine kinase 1 protein (STK1p) concentration for the prognosis of the overall survival of patients with locally advanced breast cancer (n=51) following routine treatment (neoadjuvant treatment, surgery and chemotherapy) was investigated. The patients were followed up for 44 months and the STK1p values were determined by a high-sensitivity enhanced chemiluminescence (ECL) dot blot assay. The variables investigated in relation to metastasis and survival were STK1p, clinical stage, tumor size and age, by the Kaplan-Meier method, the log-rank test and Cox uni- and multivariate analyses. Patients with high STK1p values (≥2.0 pM) 3–6 months after surgery exhibited a positive correlation to clinical stage, tumor size, occurrence of metastasis and survival. The hazard risk for the development of metastatic disease and mortality among breast cancer patients was 11–12 times higher in patients with high compared to those with low STK1p values (<2.0 pM). Notably, patients with stage III/IV disease and low STK1p values exhibited statistically significantly improved survival compared to patients with high STK1p values. A multivariate Cox analysis demonstrated that the STK1p levels 6 months after surgery was the only independent prognostic factor for metastasis and survival. In conclusion, STK1p is a prognostic marker in patients with locally advanced breast cancer and it may help identify a subgroup of stage III/IV patients with improved cancer-free survival expectancy, enabling personalized treatment.