Comparison of diagnostic and prognostic performance of two assays measuring thymidine kinase 1 activity in serum of breast cancer patients.

BACKGROUND: We compared two recently developed immunoassays for serum thymidine kinase 1 (TK1) activity: one manual assay (DiviTum, Biovica(®)) and one fully automated assay (Liaison, Diasorin(®)). METHODS: The study included 368 women: 149 healthy blood donors (control), 59 patients with benign breast disease (BBD) and 160 patients with primary breast cancer (BC). RESULTS: A regression analysis of the Liaison (y) and DiviTum (x) assays for all three groups yielded the equation y=3.93+0.03x (r=0.85, n=368). The r-value in BC was higher than in control and BBD (0.90 vs. 0.81 and 0.64). The correlation between the two assays for TK1 values above the cut-off was higher compared to that below (0.88 and 0.59). Breakdown of the BBD group into subgroups with proliferative and non-proliferative lesions was effective only with the measurement of TK1 with DiviTum assay (p=0.03). The TK1 activity determined preoperatively in BC patients with DiviTum and Liaison assays was significantly associated with T-stage (for both p=0.01), presence of vascular invasion (p=0.002 and p=0.02), lack of estrogen receptor (ER) (p=0.001 and p=0.01) and progesterone receptor (PR) (p=0.01 and p=0.03) expression. Only TK1 analyzed with the DiviTum assay was associated with tumor grade and molecular subtype of BC (p=0.02 and p=0.003). Multivariate Cox proportional hazards analyses demonstrated that T-stage, PR status and TK1 activity measured by both methods (DiviTum, RR=3.0, p=0.02 and Liaison, RR=3.1, p=0.01) were independent predictors of disease recurrence. CONCLUSIONS: In spite of differences observed between TK1 activity measured by the DiviTum and Liaison assays, both of them may be used for recurrence prediction in preoperative evaluation of BC patients.

Preoperative Serum Thymidine Kinase Activity as Novel Monitoring, Prognostic, and Predictive Biomarker in Pancreatic Cancer.

OBJECTIVE: The aim of the study was to investigate serum thymidine kinase 1 (S-TK) activity as a diagnostic and prognostic marker for patients with pancreatic ductal adenocarcinoma (PDAC). METHODS: Using the sensitive TK activity assay DiviTum, preoperative serum samples from 404 PDAC, 28 chronic pancreatitis, and 25 autoimmune pancreatitis patients and 83 healthy volunteers were analyzed. The preoperative S-TK activities of 54 PDAC patients who received neoadjuvant therapy (nTx) were also compared with those of 258 PDAC patients who did not receive nTx. RESULTS: The preoperative S-TK activities of PDAC patients were significantly higher and discriminatory from autoimmune and chronic pancreatitis patients and control groups. The S-TK activity in PDAC patients was associated with overall survival. Patients with S-TK activity of less than 80 Du (DiviTum units)/L demonstrated median survival of 20.3 months with an estimated 18.0% 5-year survival rate; for S-TK activity of 80 Du/L or greater, median survival was 15.1 months with a 6.8% 5-year survival rate. For early-stage PDAC, these differences were even more pronounced. The S-TK activity in the nTx group was significantly higher than that in the group not receiving nTx. CONCLUSIONS: Pancreatic ductal adenocarcinomas reveal a significant increase in S-TK activity, which is associated with overall survival, especially in early tumor stages. Serum thymidine kinase 1 activity may be a useful parameter for monitoring nTx efficacy.

Alternative approach to blood screening using the ExaVir reverse transcriptase activity assay.

408 non-selected samples were obtained from healthy, adult individuals donating blood at the Ethiopian Red Cross Society-National Blood Transfusion Service. All samples were screened for HIV using the Vironostika Ag/Ab test, the Amplicor DNA PCR and examined for the presence of HIV reverse transcriptase (RT) using the ExaVir Load test (version 2). A panel of supplementary tests was used to evaluate the HIV status of the discordant samples and to confirm positivity. One aim was to assess an RT based test for screening for HIV in comparison with other more conventional tests. An HIV-prevalence of 3.4 % (14/408) was found. The Vironostika Ag/Ab test produced 391 negative, and according to the supplementary testing, 14 true- and three false- positive test results. The corresponding figures for the Amplicor DNA PCR test was 384 negative, 14 true- and two extra probably false -positive samples. In addition, the DNA PCR generated eight indeterminate results. The colorimetric version of the ExaVir load test exhibited 100 % specificity and detected RT in 13 of the true positive samples, but failed to detect one sample containing 200 HIV RNA copies /mL. This sample was detectable in the fluorimetric version of the test. The detection of RT activity in addition to the currently used markers would seem to have a potential for use in blood screening.

Analysis of thymidine kinase serum levels by novel method DiviTum in multiple myeloma and monoclonal gammopathy of undetermined significance - comparison with imaging methods 99mTc-MIBI scintigraphy and 18F-FDG PET/CT.

AIMS: The study aimed at comparing two methods for evaluating thymidinekinase TK in serum - an older RIA method and novel DiviTum - in patients with MM and MGUS, and also comparing them with biochemical markers and degree of activity evaluated by imaging methods 99mTc-MIBI scintigraphy and 18F-FDG PET/CT. METHODS: Serum thymidinekinase TK levels were evaluated by DiviTum and an RIA method (TK REA kit by Immunotech);The study analyzed correlation of TK activity in serum with biochemical markers reflecting activity of MM: ß2-m, LDH, the ratio of kappa to lambda (κ/λ) free light chains and percentage of bone marrow plasma cells (BMPC). 99mTc-MIBI scintigraphy and 18F-FDG PET/CT were performed at the time of diagnosis. The degree of activity was expressed semiquantitatively. Scans were classified as 0 (normal activity), 1 (diffuse positivity) or 2 (focal positivity). RESULTS: We found a strong positive correlation between TK in serum evaluated by DiviTum and by TK REA.. The DiviTum analytic method extended the detection range and was able to detect higher levels of TK than the RIA method. DiviTum technique found positive correlation with ß2-m (r = 0.497) and LDH (r = 0.502) and moderate positive correlation with BMPC (r = 0.368). Significantly higher TK values measured by TK REA and DiviTum in the group of patients with MM (stages I, II or III) than in those with MGUS. Increased TK levels were observed in MIBI- or PET/CT-positive patients. Analysis of repeated measurements of TK in serum during treatment of MM patients found a correlation between change in TK measured by DiviTum and LDH during treatment. CONCLUSIONS: Analysis revealed a significant correlation between TK in serum and LDH, ß2-m and BMPC. Increased levels of TK in serum were observed in MIBI- or PET/CT-positive patients. Combination of positivity of imaging methods which can localize active tumor lesions and increased levels of TK in serum can have an impact on decision-making and optimization of the therapeutic approach.

Serum thymidine kinase 1 activity in the prognosis and monitoring of chemotherapy in lung cancer patients: a brief report.

INTRODUCTION: Thymidine kinase 1 (TK1) is a metabolic enzyme involved in DNA synthesis. Most standard treatment protocols for lung cancer (LC) include cytotoxic agents, which are potential modulators of TK1. We aimed to assess the prognostic significance of serum TK1 activity and its role in monitoring chemotherapy in LC patients. METHODS: TK1 activity was measured using the DiviTum (Biovica) assay in sera from 233 patients with non-small-cell lung cancer (NSCLC), 91 with small-cell lung cancer (SCLC), and 90 with benign lung disease. RESULTS: TK1 activity was significantly associated with age, performance status, and stage in NSCLC and with stage and weight loss in SCLC. In multivariate analysis, pretreatment TK1 activity, adjusted for performance status, stage, and weight loss, independently affected survival in NSCLC (relative risk =1.45, p = 0.031) and SCLC (relative risk = 2.49, p = 0.001). In NSCLC patients, adjusted elevated TK1 activity (>100 Du/L) at pretreatment was a significant predictor of treatment failure (odds ratio = 2.55, p = 0.01). A small (less than twofold) increase in TK1 activity after the first and second cycle of chemotherapy was significantly associated with treatment failure and poor overall survival. CONCLUSIONS: Elevated pretreatment serum TK1 activity was an independent, adverse prognostic factor, based on survival, in the two main histological types of LC. A small (less than twofold) increase in TK1 activity after the first and second cycle of chemotherapy was associated with treatment failure and poor overall survival.

Screening of herpes simplex virus type 1 isolates for acyclovir resistance using DiviTum® assay.

Rapid alternative methods are required to evaluate easily acyclovir (ACV) sensitivity of clinical herpes simplex virus (HSV) isolates. The objective of this study was to screen 54 ACV-sensitive and 41 ACV-resistant clinical HSV-1 isolates, well characterized by phenotypic and genotypic methods, for the phosphorylation activity of the viral thymidine kinase (TK) using a commercially available and modified non-radioactive DiviTum® test on the basis of an indirect enzyme linked immunosorbent assay. The ACV-sensitive HSV-1 isolates had high TK activity values between 31.5±6.4 DiviTum® Units per liter (DU/L) and 487.4±60.1 DU/L. The mean activity of all ACV-sensitive isolates was calculated as 212.3±15.7 DU/L. By contrast, the mean activity of all ACV-resistant HSV-1 isolates was significantly lower at 5.5±1.3 DU/L. Out of the 41 ACV-resistant HSV-1 isolates, 38 had no or very low phosphorylation activities of the viral TK between 0 DU/L and 9.3±3.2 DU/L. The remaining three ACV-resistant viral isolates had TK activities between 44.6±5.1 DU/L and 80.9±13.3D U/L. In conclusion, the modified DiviTum® test can be used to screen HSV-1 isolates for their sensitivity to ACV. Acyclovir-sensitive HSV-1 isolates show TK activities >30 DU/L and ACV-resistant isolates have activity values <10 DU/L. However, single ACV-resistant HSV-1 isolates can have TK activity values >30 DU/L. These strains are most likely ACV-resistant TK-altered mutants, but no evidence was provided for an alteration of the TK.

Increased proliferative background in healthy women with BRCA1/2 haploinsufficiency is associated with high risk for breast cancer.

Previous studies indicated that BRCA haploinsufficiency was associated with activation of the EGF receptor (EGFR) signaling pathway and increased proliferative activity in mammary epithelial cells of healthy women. We hypothesized that these processes might be reflected in the expression of serologic soluble EGFR (sEGFR) and thymidine kinase 1 (TK1) activity, which signal the initial and final steps of the proliferative pathway, respectively. We found that healthy carriers of BRCA1/2 mutations (n = 80) showed a significantly higher TK1 activity than age-matched controls (P = 0.0003), and TK1 activity was similar in women with BRCA1 and BRCA2 mutations (P = 0.74). The sEGFR concentration was significantly higher in women with BRCA1 than in controls and BRCA2 mutation (P = 0.013 and 0.002, respectively). During follow-up, four of 80 BRCA1/2 mutation carriers developed breast cancer. These women showed a significantly higher TK1 activity and somewhat higher sEGFR concentrations than the other 76 BRCA1/2 carriers (P = 0.04 and 0.09, respectively). All tumors were negative for ovarian hormone receptors, but showed a high EGFR expression. This study was limited by the short-term follow-up (mean, 27 months; range, 5-45), which resulted in a small sample size. Women with BRCA1 and BRCA2 mutations that had undergone risk-reducing bilateral salpingo-oophorectomy (BSO) showed significantly lower sEGFR compared with those without surgery (P = 0.007 and 0.038, respectively). Larger, prospective studies are warranted to investigate whether TK1 and sEGFR measurements may be useful for identifying healthy BRCA1/2 carriers with high risk of developing breast cancer; moreover, sEGFR measurements may serve as effective tools for assessing risk before and after BSO.

Significance of amino acid substitutions in the thymidine kinase gene of herpes simplex virus type 1 for resistance.

The analysis of the viral thymidine kinase (TK) genotype is of rising significance for testing resistance of herpes simplex virus (HSV) to antivirals especially acyclovir. However, numerous of the described amino acid (aa) substitutions are diagnostically less conclusive because of the pronounced natural polymorphism of this gene. In this study, several aa substitutions in the TK sequence of HSV-1 with unclear significance for resistance were analyzed by expression of recombinant TK proteins and determination of enzymatic activity on the basis of an enzyme linked immunosorbent assay using bromodeoxyuridine (BrdU) as TK substrate. The recombinant TK wild-type protein resulted in high TK activity and TK mutant with stop of translation showed negative results. The recombinant TK proteins containing the aa substitutions R41H or V348I had high phosphorylation activities suggesting most likely natural gene polymorphisms. By contrast, the aa changes Y53H, L139V, R163H, L298A and L315S were accompanied by negative or weakly positive TK activities indicating resistance association. In conclusion, the combination of methods described here represents a useful tool to evaluate the significance of aa substitutions for resistance of clinical HSV-1 strains.

Serum thymidine kinase 1 activity in breast cancer.

AIMS: Thymidine kinase 1 (TK1) is an enzyme involved in DNA synthesis and an important proliferation marker. We explored the association of preoperative serum TK1 activity with clinicopathological parameters and prognosis in terms of recurrence-free survival (RFS) in breast cancer (BC) patients. PATIENTS AND METHODS: TK1 activity in serum of 120 healthy women and 161 BC patients was measured by quantitative ELISA. RESULTS: Serum TK1 activity in BC patients was significantly higher than in healthy women (P < 0.0001). In BC patients elevated TK1 activity was significantly associated with advanced T stage (P = 0.015), higher grade (P = 0.013), presence of tumor necrosis (P = 0.006), vascular invasion (P = 0.002), and lack of estrogen receptor (ER) and progesterone receptor (PR) expression (P = 0.0004 and P = 0.003). Higher TK1 activity was found in patients with BRCA1/2 mutations compared to those without the mutation (P = 0.004). Multivariate Cox proportional hazards analyses demonstrated that TK1, adjusted for stage, grade, necrosis, ER and PR negativity was retained as an independent predictor of disease recurrence (Hazard Ratio = 3.9, 95%CI 1.3-11.6, P = 0.013). CONCLUSION: Elevated serum TK1 is an important risk factor indicating a high proliferation potential of tumors at the time of excision. In multivariate analysis TK1 activity was found to be an independent prognostic factor for RFS.

Circulating tumor M2 pyruvate kinase and thymidine kinase 1 are potential predictors for disease recurrence in renal cell carcinoma after nephrectomy.

OBJECTIVES: Pyruvate kinase type M2 (TuM2-PK) and thymidine kinase 1 (TK1) are the key enzymes involved in tumor cells metabolism and proliferation. We explored the association of their preoperative circulating levels with disease recurrence in patients with renal cell carcinoma (RCC). METHODS: We measured the plasma levels of TuM2-PK levels and serum TK1 activity preoperatively in patients with RCC, using a quantitative ELISA, and correlated the results with clinicopathological parameters. RESULTS: Significantly higher levels of TuM2-PK and TK1 were found in 116 patients with RCC compared with 20 healthy participants (P < .001 and P = .03), but not compared with 27 patients with benign kidney tumors (P = .13 and P = .72). There was a significant association between the level of TuM2-PK and of TK1 activity with T stage (P = .01 and P = .04). Of 2 markers only TuM2-PK was significantly associated with tumor grade (P = .001). The presence of extensive tumor necrosis (> 50%) was associated with high TuM2-PK (P = .001) and low TK1 (P = .03). The 5-year recurrence-free survival for patients with elevated TuM2-PK or TK1 was significantly lower compared with those for patients with normal marker levels (55% vs 94%, P < .001 and 21% vs 90%, P = .002). Multivariate Cox Proportional Hazard analysis demonstrated that TuM2-PK and TK1, adjusted for stage, grade and tumor necrosis were retained as independent predictors of disease recurrence (HR = 7.3, P = .04 and HR = 3.8, P = .03). CONCLUSIONS: The measurements of 2 circulating biomarkers, TuM2-PK and TK1, in RCC patients before nephrectomy can be useful for predicting recurrence and stratifying the patients into risk groups for possible adjuvant treatment.