Application of an in vitro assay for serum thymidine kinase: results on viral disease and malignancies in humans

Nanochannel-based biosensor for ultrasensitive and label-free detection of thymidine kinase activity

Thymidine Kinase 1 (TK1) is a pivotal enzyme in fundamental biochemistry and molecular diagnosis, but recognition and molecule detection is a challenging task. Here, we constructed a DNA-integrated hybrid nanochannel sensor for TK1 activity and inhibition assay. Single-stranded DNA containing thymidine was used as a substrate to functionalize the nanochannels, restricting the ion current through channels. With kinase, the thymidine at the termini of the substrate DNA is phosphorylated, elevating surface charge density and mitigating the pore-obstruction effect by increasing transmembrane ion current. The kinase-induced distinctness can be accurately monitored by this hybrid nanodevice, which benefits from its high sensitivity to the change of surface charge. The excellent analytical performance in both kinase enzyme activity and inhibition analysis resulted in efficient and selective evaluation in human serum. Furthermore, compared to current approaches, it greatly simplifies and offers a direct method of analysis, making it a promising sensor technology for cancer management as well as the activities of multiple types of nucleic acid kinases.

A monoclonal antibody-based sandwich ELISA for measuring canine Thymidine kinase 1 protein and its role as biomarker in canine lymphoma

Introduction

Dogs play an important role in society, which increased during the covid epidemics. This has led to a much higher workload for the veterinarians. Therefore, there is a need for efficient diagnostic tools to identify risk of malignant diseases. Here the development of a new test that can solve some of these problems is presented. It is based on serum Thymidine Kinase 1 (TK1), which is a biomarker for cell proliferation and cell lysis.

Methods

Anti-TK1 monoclonal antibodies were produced against two different epitopes, the active site of the TK1 protein and the C-terminal region of canine TK1. The antibodies were developed with hybridoma technology and validated using dot blot, Quartz Crystal Microbalance (QCM) technology, western blots, immunoprecipitation (IP), and enzyme-linked immunosorbent assay (ELISA). Clinical evaluation of Canine TK1 ELISA was done by using sera from 131 healthy dogs and 93 dogs with lymphoma. The two selected Anti-TK1 monoclonal antibodies have Kd values in the range of 10-9 M and further analysis with dot and western blots confirmed the high affinity binding of these antibodies. A sandwich Canine TK1 ELISA was developed using the anti-TK1 antibodies, and TK1 concentrations in serum samples were determined using dog recombinant TK1 as a standard.

Results

Serum TK1 protein levels were significantly higher in dogs with lymphoma compared to those in healthy dogs (p < 0.0001). Receiver operating curve analysis showed that the canine TK1-ELISA obtain a sensitivity of 0.80, at a specificity of 0.95. Moreover, the Canine TK1 ELISA has a positive predictive value (PPV) of 97%, and the negative predictive value (NPV) of 83%, reflecting the proportion of test results that are truly positive and negative. Furthermore, Canine TK1 ELISA had significantly higher capacity to differentiate dogs with T-cell lymphoma from those with B-cell lymphoma compared to earlier used TK1 activity assays.

Discussion

These results demonstrate that the Canine TK1 ELISA can serve as an efficient tool in the diagnosis and management of dogs with lymphomas.

Is serum thymidine kinase 1 a prognostic biomarker in primary tumor location of colorectal carcinomas?

AIM

To assess whether serum thymidine kinase 1 (STK1p), CEA and CA19.9 can be used as prognostic biomarkers in the primary tumor location (PTL) of colorectal carcinoma (CRC). Additional clinical factors of TNM stage, pathological grade, age and sex were also included.

METHODS

STK1p was determined by an ECL-dot-blot assay, and CEA/CA19.9 was determined by an automatic electrochemiluminescence analyzer in a retrospective presurgery of right-colon carcinoma (R-CC, n = 90), left-colon carcinoma (L-CC, n = 128) and rectal carcinoma (RC, n = 270). Prognostic factors were evaluated by COX and overall survival (OS).

RESULTS

The multivariate-COX and OS in relation to the prognostic factors of PTL in CRC were different and complex. An elevated STK1p value was significantly associated with poor OS in RC (P = 0.002) and L-CC (P = 0.037) but not in R-CC (P > 0.05). Elevated CEA (P≈.000) and CA19.9 (P≈.000) were significantly associated with poor OS in RC but not in L-CC and R-CC. Multivariate-COX showed that STK1p (P = 0.02, HR = 1.779, 95%CI 1.30-7.582), CEA (P = 0.001, HR = 2.052, 95%CI 1.320-3.189), CA19.9 (P≈.000, HR = 2.574, 95%CI 1.592-4.162) and TNM-stage (P≈.000, HR = 2.368, 95%CI 1.518-3.694) were independent prognostic factors in RC, while TNM-stage was an independent prognostic factor only in R-CC (P = 0.011, HR = 3.139, 95% CI 1.30-7.582) and L-CC (P≈.000, HR = 4.168, 95%CI 1.980-8.852). Moreover, elevated STK1p was significantly more sensitive (P < .001) for predicting mortality than CEA and CA19.9. No correlation was found between STK1p, CEA or AFP.

CONCLUSION

Combining TNM stage and suitable biomarkers, STK1p provides further reliable information on the survival of PTL of CRC.

Markers for internal neoplasia in the horse

The diagnosis of internal neoplasia in horses is challenging. Increased production of hormones physiologic for adult animals (e.g., adrenocorticotropin, norepinephrine, and erythropoietin) or typical for the foetal phase (alpha-fetoprotein, anti-Müllerian hormone, and parathyroid-hormone-related protein) might aid in tumour diagnostics. Thymidine kinase-1 and alkaline phosphatase are examples of intracellular enzymes, whose activity in the blood may increase in some neoplasia cases. Furthermore, inappropriate production of abnormal monoclonal or autologous antibodies can accompany lymphoma and multiple myeloma. Many of those tumour markers lead to clinical or laboratory changes, called paraneoplastic syndromes, such as hypercalcaemia and erythrocytosis. The interpretation of the results of the tumour marker measurements in horses is complicated due to many factors affecting the markers' concentration or activity (e.g., young age, pregnancy, and inflammation) and other diseases triggering the same changes. Moreover, the presence of paraneoplastic syndromes is inconsistent, which leads to low sensitivity of those substances as tumour markers. In conclusion, screening for neoplasia in horses is not recommended. The measurement of tumour markers should be performed only in risk groups with suspicious clinical or laboratory findings, and the results should be interpreted with caution. It is advisable to add inflammatory markers to the tumour profile or repeat the measurements.

Thymidine kinase 1 through the ages: a comprehensive review

Proliferation markers, such as proliferating cell nuclear antigen (PCNA), Ki-67, and thymidine kinase 1 (TK1), have potential as diagnostic tools and as prognostic factors in assessing cancer treatment and disease progression. TK1 is involved in cellular proliferation through the recovery of the nucleotide thymidine in the DNA salvage pathway. TK1 upregulation has been found to be an early event in cancer development. In addition, serum levels of TK1 have been shown to be tied to cancer stage, so that higher levels of TK1 indicate a more serious prognosis. As a result of these findings and others, TK1 is not only a potentially viable biomarker for cancer recurrence, treatment monitoring, and survival, but is potentially more advantageous than current biomarkers. Compared to other proliferation markers, TK1 levels during S phase more accurately determine the rate of DNA synthesis in actively dividing tumors. Several reviews of TK1 elaborate on various assays that have been developed to measure levels in the serum of cancer patients in clinical settings. In this review, we include a brief history of important TK1 discoveries and findings, a comprehensive overview of TK1 regulation at DNA to protein levels, and recent findings that indicate TK1’s potential role in cancer pathogenesis and its growing potential as a tumor biomarker and therapeutic target.

Blood biomarker algorithms for the diagnosis of mycoplasma pneumoniae respiratory infections

The correct diagnosis of acute infections as to bacteria, mycoplasma or virus is a clinical challenge and has a great impact on the therapeutic decisions. Current diagnostic tests of mycoplasma pneumoniae infections of the respiratory tract such as PCR and serology are either somewhat unreliable or slow and do not entirely meet the clinical needs of accurate and fast diagnosis. The aim of this report was to examine a panel of candidate biomarkers and their capacity to distinguish mycoplasma pneumoniae respiratory infections from respiratory infections caused by either bacterial or virus.

METHOD

Patients with confirmed etiology of their acute respiratory infections (n = 156) were included of which 28 patients were diagnosed with mycoplasma pneumoniae. Blood was taken before any antibiotics treatment and analysed for Azurocidin (HBP), Calprotectin, CRP, Human Neutrophil Lipocalin (HNL), Interferon γ-induced Protein 10 kDa (IP-10), Procalcitonin (PCT), Thymidine Kinase 1 (TK1), TNF-Related Apoptosis-Inducing Ligand (TRAIL).

RESULTS

Individually the concentrations of IP-10, TK1 and P-HNL distinguished mycoplasma pneumoniae from bacterial infections with AUCs of 0.79-0.85. However, in combination, TK1 with either IP-10 or P-HNL showed an AUC of 0.97-0.95. In the distinction between mycoplasma pneumoniae and viral respiratory infections CRP, Calprotectin and TRAIL showed individual AUCs of 0.94-0.84. Together with either P-HNL dimer or PCT, CRP showed AUCs of 0.97.

CONCLUSION

Our results indicate that it may be possible to design useful diagnostic algorithms of biomarkers that could help distinguish mycoplasma pneumoniae from respiratory infections caused by bacteria or virus. The development of rapid point-of-care assays based on such algorithms could be clinically useful tools in the therapeutic decision-making.

HNL (Human Neutrophil Lipocalin) and a multimarker approach to the distinction between bacterial and viral infections

OBJECTIVES

The distinction between bacterial and viral causes of acute infections is a major clinical challenge. In this report we investigate the diagnostic performance in this regard of nine candidate biomarkers together with HNL (Human Neutrophil Lipocalin).

METHODS

Blood was obtained from patients with symptoms of infectious (n = 581). HNL was measured in whole blood (B-HNL) after pre-activation with the neutrophil activator fMLP or in plasma (P-HNL). Azurocidin also known as heparin-binding protein (HBP), Calprotectin, PMN-CD64, CRP (C-reactive protein), IP-10 (Interferon γ-induced Protein 10 kDa), PCT (Procalcitonin), TK1 (Thymidine kinase 1), TRAIL (TNF-related apoptosis-inducing ligand) were measured in plasma/serum. Area under the ROC (receiver operating characteristics) curve (AuROC) was used for the evaluation of the clinical performance of the biomarkers.

RESULTS

Side-by-side comparisons of the ten biomarkers showed large difference in the AuROC with B-HNL being the superior biomarker (0.91, 95% CI 0.86-0.95) and with the other nine biomarkers varying from AuROC of 0.63-0.79. The combination of B-HNL with IP-10 and/or TRAIL increased the diagnostic performance further to AuROCs of 0.94-0.97. The AuROCs of the combination of CRP with IP-10 and/or TRAIL were significantly lower than combinations with B-HNL 0.87 (95% CI 0.83-0.91).

CONCLUSION

The diagnostic performance of whole blood activated HNL was superior in the distinction between bacterial or viral infections. The addition of IP-10 and/or TRAIL to the diagnostic algorithm increased the performance of B-HNL further. The rapid analysis of HNL, reflecting bacterial infections, together with biomarkers reflecting viral infections may be the ideal combination of diagnostic biomarkers of acute infections.

Thymidine kinase 1 as a tumor biomarker: technical advances offer new potential to an old biomarker

Thymidine kinase 1 (TK1) is a key enzyme in DNA precursor synthesis. It is upregulated during the S phase of the cell cycle and its presence in cells is an indicator of active cell proliferation. In studies since the 1980s, TK1 has been shown as a clinically valuable biomarker for the management of hematological malignancies. However, TK1 activity assays may underestimate serum TK1 in subjects with solid tumors limiting its sensitivity. The development of TK1 immunoassays has made the assay of TK1 more widely available and increased its applicability to solid tumor diseases. This paper will review TK1 as a tumor biomarker with emphasis on recent studies and technologies plus highlight its potential in drug discovery and as a therapeutic target.

Serum Thymidine Kinase and Beta-2 Microglobulin in Monoclonal Gammopathies

We evaluated the serum thymidine kinase (TK) and β-2 microglobulin (β-2) levels of 22 patients with monoclonal gammopathy of undetermined significance (MGUS) and of 29 patients with multiple myeloma (MM). Both parameters were significantly lower in MGUS than in MM patients and in early (stage I+II) than in advanced (stage III) MM. TK was also lower in MGUS than in stage I MM (p < 0.025). A seven-fold increase of TK level was documented in one patient who developed a full blown picture of MM 6 years after a diagnosis of MGUS. In 3 patients with stage III MM, a sharp decrease in TK (40–77%) and in β-2 (29–53%) levels at remission was evident with respect to the levels measured at diagnosis. Patients with high levels of TK or [3-2 had a shorter survival than those with low levels; however, this was statistically significant only for β-2 levels (p < 0.02). Serum TK as well as β-2 levels appear to be of clinical value in monoclonal gammopathies and related to the course of the disease.

Serum Thymidine Kinase (TK) Evaluation in HIV Infection

Serum thymidine kinase (TK), measured using Prolifigen TK-REA, from AB Sangtec Medical, was investigated in 24 HIV seropositive patients without immunological alterations, 26 seropositives with immunological alterations, 125 LAS, 25 ARC, and 20 AIDS. Subjects with serological markers of prior EBV, HBV, and CMV infection were included but none with acute infectious mononucleosis or acute viral hepatitis. Serum TK was elevated from the beginning of the HIV infection, the seropositive stage, and more markedly afterwards during the course of the infection, with a close correlation with the stage.

TK also increased during AZT treatment, due to bone-marrow toxicity. On lowering the dosage or discontinuing the drug TK returned to basal levels.

Although the rise in serum may well not be correlated only with the HIV infection, it does add to the picture given by other clinical and/or laboratory methods. Serum TK can be a helpful laboratory test in the follow-up ofpatients with HIV infection, especially when serum levels are disproportionate to the stage, opportunistic infections, lymphoproliferative malignancies. In such cases bone-marrow toxicity due to treatment can be suspected.

The Clinical Significance of Thymidine Kinase 1 Measurement in Serum of Breast Cancer Patients Using Anti-TK1 Antibody

The activity of total thymidine kinase in serum (S-TK) has been used as a tumor maker for decades. To date such activity has been determined using [125]I-iodo-deoxyuridine as a substrate. The aim of this study was to develop a new, antibody-based technique for the measurement of cytoplasmic thymidine kinase (TK1) in serum. Both mono- and polyclonal antibodies against S-TK1 were used in dot blot assay. S-TK1 was characterized by SDS and IEF techniques. Sixty-five breast cancer patients were studied, including 17 preoperative and 38 postoperative tumor-free patients and 10 patients with metastases to the lymph nodes (N1–2). They were compared to patients with benign tumors (n=21) and healthy volunteers (n=11). S-TK1 was low (0–1.0 pM) in healthy volunteers, while in preoperative patients the level was increased 6–110-fold. Significant differences were observed between preoperative patients and healthy volunteers (p=0.005), preoperative patients and patients with benign tumors (p<0.001), and preoperative patients and postoperative patients without metastases (p<0.001). No significant difference was observed between preoperative patients and postoperative patients with metastases (p=0.191). The S-TK activity in preoperative patients was also high in serum, but no decrease was observed following surgery. In conclusion, the anti-TK1 antibody could be a good marker for monitoring the response of breast cancer patients to therapy.

The Half-Life of Thymidine Kinase 1 in Serum Measured by ECL Dot Blot: A Potential Marker for Monitoring the Response to Surgery of Patients with Gastric Cancer

Thymidine kinase 1 in serum (STK1) of patients with gastric cancer was determined by two methods: ECL dot blot and radioactivity assay. Both measurements showed significantly different values for preoperative STK1 and healthy STK1 (p=0.012 for ECL dot blot and p=0.003 for the radioactivity assay). The preliminary results of ECL dot blot STK1 measurement showed that in tumor-free subjects the level of the enzyme was significantly reduced to 52.7% 35 days after surgery (n=8, p=0.0106). The decrease in STK1 levels in the tumor-free subjects paralleled the decline of the half-life of the STK1 enzyme. In patients with distant metastases (n=6) the enzyme level had increased to 173% 35 days postoperatively. By contrast, with the radioactivity assay no significant differences in thymidine kinase activity for 0-day-postoperative patients and 35-day-postoperative tumor-free patients was found (p=0.329). The activity decreased to 80% in 35-day-postoperative patients with metastatic disease. We suggest that the value of the half-life of STK1 measured by ECL dot blot can be used as a potential marker for monitoring the response to surgery in patients with gastric or other cancers one month after surgery.

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.

Thymidine Kinase: A Biomarker for Recently Diagnosed Acute Leukemia in Pediatric Patients According to the Cell Line Involved

BACKGROUND AND AIMS

Acute leukemia (AL) is a heterogeneous group of diseases characterized by a disorganized clone proliferation of hematopoietic cells. Thymidine kinase (TK) is a cell enzyme involved in DNA synthesis and is considered a cellular proliferation marker in some solid tumors.

METHODS

A cross-sectional prospective and comparative study was performed in the Federico Gomez Children's Hospital in Mexico (HIMFG, in Spanish) in 125 samples of patients of the HIMFG with AL and 138 samples of children without leukemia. Serum TK levels were determined for both groups.

RESULTS

Of the children with AL, 90 presented B-cell acute lymphoblastic leukemia (B-ALL); 13, T-cell acute lymphoblastic leukemia (T-ALL); and 22, acute myeloid leukemia (AML). A median (m) TK level of 23.7 IU (IQR 17-35.7) was observed in the group without AL and 91 IU (IQR 98-392) in the AL group. This difference was statistically significant (p <0.0001). When analyzing TK levels according to the type of leukemia, the m was as follows: 68 IU (IQR 35-118) for B-ALL, 470 IU (IQR 88-750) for AML, and 1678 IU (IQR 288-2108) for T- ALL.

CONCLUSION

TK is an enzyme showing heterogeneous levels in B-ALL although it is significantly increased in 90% of patients with T-ALL and AML.

Serum thymidine kinase activity in clinically healthy and diseased horses: a potential marker for lymphoma

Serum thymidine kinase (sTK) activity is a tumour marker used as a prognostic indicator for lymphoma in humans, dogs and cats. The aim of this study was to evaluate the clinical utility of sTK as a biomarker for lymphoma in horses. Serum samples were collected from clinically normal horses (n = 37), horses with lymphoma (n = 23), horses with non-haematopoietic neoplasia (n = 9) and horses with inflammatory disease (n = 14). sTK was measured using a radioenzyme assay. A reference cut-off value of <2.7 U/L (mean + 2 standard deviations, SDs) was established using data from clinically normal horses. sTK activity (mean ± SD) was 26.3 ± 91.5 U/L (range 0.8-443 U/L) for horses with lymphoma, 2.3 ± 1.4 U/L (range 0.6-5.7 U/L) for horses with non-haematopoietic neoplasia and 1.5 ± 0.6 U/L (range 0.6-2.8 U/L) for horses with inflammatory disease. Horses with lymphoma had significantly higher sTK activity than horses without clinical signs of disease (P <0.01), horses with inflammatory disease (P <0.01) and horses with non-haematopoietic neoplasia (P <0.05). sTK activity is a potentially useful biomarker for equine lymphoma.

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.

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.

Serum thymidine kinase activity in clinically healthy and diseased cats: a potential biomarker for lymphoma

The thymidine kinases are enzymes that convert deoxythymidine to deoxythymidine monophosphate and have a function in DNA synthesis. Rapidly proliferating cells will have higher levels of thymidine kinase. Serum thymidine kinase activity (sTK) is a useful tumour marker in humans and dogs, with utility as a prognostic indicator in lymphoma. In the current study serum samples were collected from 49 clinically healthy cats, 33 with lymphoma, 55 with inflammatory disease and 34 with non-haematopoietic neoplasia (NHPN). sTK was measured using a radioenzyme assay and a reference interval (1.96 × SD) was established from the clinically healthy cats (<5.5 U/l). Mean sTK activity for healthy cats was 2.2 U/l (range 0.8-8.4, ± SD 1.7). Mean sTK activity for cats with lymphoma was 17.5 U/l (range 1.0-100.0 SD ± 27.4). Mean sTK activity for cats with NHPN was 4.2 U/l (range 1.0-45.0, SD ± 8.6). Mean sTK activity for the inflammatory group was 3.4 U/l (range 1.0-19.6, SD 3.9). Cats with lymphoma had significantly higher sTK activity than healthy cats or cats with inflammatory disease (P <0.0001) and cats with NHPN (P <0.0002). sTK activity is a potentially useful biomarker for feline lymphoma and further study is required to assess its utility as a prognostic indicator.

Liquid chromatography-tandem mass spectrometry method for quantification of thymidine kinase activity in human serum by monitoring the conversion of 3'-deoxy-3'-fluorothymidine to 3'-deoxy-3'-fluorothymidine monophosphate

Thymidine kinase 1 (TK1) is an enzyme involved in DNA synthesis whose activity in serum is indicative of tumor proliferation and the severity of blood malignancies. 3'-deoxy-3'-fluorothymidine (FLT), a specific exogenous substrate for TK1, is phosphorylated by TK1 in the presence of a phosphorylating buffer, therefore the conversion of FLT to 3'-deoxy-3'-fluorothymidine monophosphate (FLT-MP) can be measured to assess serum TK1 activity. Here we describe a liquid chromatography-MS/MS (LC-MS/MS) method for quantification of FLT and FLT-MP from serum using protein precipitation and column switching followed by detection on an Applied Biosystems SCIEX API 4000 QTrap mass spectrometer. The method was linear over the range of 0.5-500 ng/mL for FLT and 2.5-2000 ng/mL for FLT-MP with a mean correlation coefficient of 0.9964 and 0.9935 for FLT and FLT-MP, respectively. The lower limit of quantification was 0.5 ng/mL for FLT and 2.5 ng/mL for FLT-MP. Intra-assay accuracy and inter-assay accuracy was within ±12% for both FLT and FLT-MP. Intra-assay precision was 2.8% to 7.7% for FLT and 3.3% to 5.8% for FLT-MP. Inter-assay precision was 4.6% to 14.9% for FLT and 4.9% to 14.6% for FLT-MP. Serum TK1 activity was measured in serum from hepatocellular carcinoma patients and age-matched controls under standardized conditions. Elevated TK1 activity was detected in 26.3% of hepatocellular carcinoma samples compared to controls. This method provides a robust alternative to radiometric and immunochemical assays of serum TK1 activity.

Homogeneous assay for real-time and simultaneous detection of thymidine kinase 1 and deoxycytidine kinase activities

Measurement of thymidine kinase-1 (TK1) and deoxycytidine kinase (dCK) activity may be useful in cancer disease management. Therefore, a one-step homogeneous assay for real-time determination of TK1 and dCK was developed by combining enzyme complementation with fluorescent signal generation using primer extension and a quenched probe oligodeoxyribonucleotide system at 37 °C. Complementation, for producing dCTP and TTP from nucleoside substrates, was carried out by dTMP kinase and/or UMP/CMP kinase and nucleoside diphosphate kinase. dNTP was continuously incorporated into a fixed oligodeoxyribonucleotide primer, template, and probe system, and the fluorescent signal was generated by using the combined actions of primer extension and 5' exonuclease activity of Thermophilus aquaticus (Taq) DNA polymerase for specific relief of fluorescent quenching. Fluorescence was captured at 1-min intervals using a real-time polymerase chain reaction (PCR) instrument. A horizontal threshold line, crossing all sample relative fluorescent units (RFU) values at the level of the RFU of the blank sample at the end of the assay (i.e., 90 min), was drawn, obtaining RFU measurement data in minutes for each sample. Duplex proof of principle was demonstrated by the independent determination of different amounts of dCK and TK1 in combination. R(2) values of 0.90 were demonstrated with Prolifigen TK-REA U/L reference values obtained from pathological canine and human serum samples.

High baseline serum thymidine kinase 1 level predicts unfavorable outcome in patients with follicular lymphoma

Serum thymidine kinase 1 (TK1) is a sensitive marker of tumor cell proliferation. TK1 has been reported as a reliable prognostic factor in solid tumors and chronic lymphocytic leukemia, but has not yet been tested in large populations of patients with non-Hodgkin lymphoma. In this study, the prognostic significance of TK1 levels was assessed in 170 prospectively enrolled patients with previously untreated follicular lymphoma (FL). The TK1 level at the time of treatment initiation was shown to correlate with the clinical stage, Follicular Lymphoma International Prognostic Index (FLIPI) score, β(2)-microglobulin level, lactate dehydrogenase level and B symptoms. No correlation was found with FL grade or Ki-67 proliferation index. Cox regression analysis identified high TK1 levels (≥ 15I U/L) as a prognostic factor for overall survival (hazard ratio 2.91, p = 0.019) and progression-free survival (hazard ratio 1.94, p = 0.022) independent of FLIPI score variables. Thus, TK1 levels may help to refine risk assessment in the modern immunotherapy era.

High thymidine kinase activity is a strong predictive factor for poor prognosis in peripheral T-cell lymphoma treated with cyclophosphamide, adriamycin, vincristine and prednisone

The prognosis of patients with peripheral T-cell lymphoma (PTCL) treated with cyclophosphamide, adriamycin, vincristine and prednisone (CHOP) is poor, but their laboratory prognostic parameters had not previously been evaluated. We retrospectively reviewed 55 patients with newly diagnosed PTCL treated with CHOP from August 1999 to May 2009 at our institution. We analyzed six laboratory parameters, including thymidine kinase (TK) activity, to evaluate overall survival, which was the primary end-point. In multivariate analysis, the overall survival was significantly worse in patients with high TK activity (hazard ratio 34.8, 95% confidence interval [CI] 1.03-1176.23). The overall response rate among patients with high TK activity was 21.4%, significantly poorer compared with other parameters (p = 0.001). High TK activity predicts poor overall survival among patients with newly diagnosed PTCL treated with CHOP. Response to CHOP treatment is significantly decreased in patients with PTCL with high TK activity.

XPA-210: a new proliferation marker to characterize tumor biology and progression of renal cell carcinoma

PURPOSE

Recent lung cancer data have shown an association of XPA-210, a key peptide of thymidine kinase, with advanced disease. We thus assessed its proliferation status in primary (M0) and metastatic (M1) renal cell carcinoma (RCC).

METHODS

Paraffin slides from 30 patients (mean age: 61.2 years; range: 42-84) with clear-cell RCC (M0 in 10; non-osseous M1 in 10; osseous M1 in 10) were T-matched for pT1/pT3. Corresponding malignant and benign renal parenchyma were immunohistochemically stained against XPA-210. Staining density was determined by a semi-quantitative score of positive cell shares. Staining intensity included the precise cellular location.

RESULTS

XPA-210 occurred predominantly in the nucleus, with a minor cytoplasmatic component. RCC tissue showed higher density and stronger intensity than did benign renal tissue in both nucleus (P = 0.005) and cytoplasm (P = 0.01). Density and intensity were positively associated with tumor diameters ≤7 cm, whereas they tended to correlate inversely in tumors >7 cm (P 0.07). Density of stained cells was significantly higher in metastatic than in localized RCC in both nucleus and cytoplasm (P < 0.04). Non-osseous M1 tissue showed significantly higher nuclear and cytoplasmatic expression than did M0 tissue (P < 0.05), whereas osseous M1 tissue did not.

CONCLUSIONS

In all RCC tissues, XPA-210 staining was significantly higher in the nucleus than in cytoplasm, potentially owing to large cytoplasmatic spaces as a characteristic histologic feature of clear-cell component. XPA-210 expression gradually increased from localized to metastatic disease, peaking in patients without bone involvement. Therefore, XPA-210 might aid the selection of appropriate adjuvant treatment in high-risk patients.

Serum thymidine kinase activity as a useful marker for bovine leukosis

Serum thymidine kinase (TK) activity has recently been evaluated as a serum marker for human and canine hematopoietic neoplasms. The purpose of the current study was to establish the significance of serum TK activity in the diagnosis of bovine leukosis. The discrimination value for TK activity was set at 5.4 U/l based on the receiver operating characteristic curve. In the group of clinically healthy cows, only 2 out of 83 cows (2.4%) had serum TK activity above the discrimination value. In contrast, 19 out of 20 cows (95.0%) with bovine leukosis showed serum TK activity above the discrimination value, although only 7 of 79 (8.9%) cows diagnosed with diseases other than bovine leukosis showed elevated serum TK activity. Thymidine kinase activities of all Bovine leukemia virus-positive cows with or without lymphocytosis were below the discrimination value. Sensitivity and specificity of measuring serum TK activity as a diagnostic tool for bovine leukosis was 95.0% and 95.9%, respectively. Results indicate that serum TK activity may be a marker for bovine leukosis.

Serum TK levels in CLL identify Binet stage A patients within biologically defined prognostic subgroups most likely to undergo disease progression

OBJECTIVE

Serum thymidine kinase (TK) levels have been shown to be correlated with survival in many malignancies, including chronic lymphocytic leukaemia (CLL). This study was designed to investigate associations between TK levels and other prognostic markers, in newly and previously diagnosed Binet stage A patients. Furthermore, the use of serum TK measurement to identify subcategories of disease within those defined by IgV(H) mutational status, gene usage and chromosomal aberrations was investigated.

METHODS

Ninety-one CLL patients were enrolled. Serum TK levels were measured using a radioenzyme assay. IgV(H) mutational status and V(H) gene usage were determined using BIOMED-2 primers and protocol. Recurring chromosomal abnormalities were detected by interphase fluorescent in situ hybridisation (FISH). Flow cytometry and reverse transcriptase polymerase chain reaction (RT-PCR) determined CD38 and Zap-70 expression, respectively.

RESULTS

Significantly higher serum TK levels were found in IgV(H) unmutated, compared with IgV(H) mutated, patients (P < 0.001). Elevated TK levels were also found in patients with CD38 and Zap-70 positivity (P = 0.004, P < 0.001, respectively), short lymphocyte doubling time (LDT) (P = 0.044) and poor or intermediate prognosis chromosomal aberrations (P < 0.001).

CONCLUSION

A TK level of >8.5 U/L best identified patients with progressive disease. Elevated TK levels could identify patients categorised, at diagnosis, into good prognosis subgroups by the various biological markers (mutated IgV(H), good prognosis chromosomal aberrations, Zap-70(-) and CD38(-)) who subsequently showed disease progression. Additionally, patients with V(H)3-21 gene usage showed high TK levels, irrespective of mutational status, and serum TK measurement retained predictive power as disease progressed in all subcategories studied.

Structures of thymidine kinase 1 of human and mycoplasmic origin

Cytosolic thymidine kinase 1, TK1, is a well known cell-cycle-regulated enzyme of importance in nucleotide metabolism as well as an activator of antiviral and anticancer drugs such as 3'-azido-3'-deoxythymidine (AZT). We have now determined the structures of the TK1 family, the human and Ureaplasma urealyticum enzymes, in complex with the feedback inhibitor dTTP. The TK1s have a tetrameric structure in which each subunit contains an alpha/beta-domain that is similar to ATPase domains of members of the RecA structural family and a domain containing a structural zinc. The zinc ion connects beta-structures at the root of a beta-ribbon that forms a stem that widens to a lasso-type loop. The thymidine of dTTP is hydrogen-bonded to main-chain atoms predominantly coming from the lasso loop. This binding is in contrast to other deoxyribonucleoside kinases where specific interactions occur with side chains. The TK1 structure differs fundamentally from the structures of the other deoxyribonucleoside kinases, indicating a different evolutionary origin.

Sensitive nonradiometric method for determining thymidine kinase 1 activity

BACKGROUND

Thymidine kinase 1 (TK1) is a cytoplasmic enzyme, produced only in the S-phase of proliferating cells, that has potential as a tumor marker. Specific determination of TK1 in serum is difficult, in part because of differences in the physical properties of serum TK1 compared with cytoplasmic TK1.

METHODS

The first step in the new assay was phosphorylation of 3'-azido-2',3'-deoxythymidine (AZT) to AZT 5'-monophosphate (AZTMP) by TK1 present in patient material. The AZTMP formed was measured in a competitive immunoassay with specific anti-AZTMP antibodies and AZTMP-labeled peroxidase. Results were compared with those of a TK radioenzyme assay (REA) for 78 samples from patients suffering from hematologic diseases.

RESULTS

The detection limit was 78 microIU/L, and within-run CVs <20% were seen for samples with TK1 down to 130 microIU/L. Cross-determination of the mitochondrial isoenzyme TK2 activity was <0.1%. Between-assay imprecision (CV) was 3.5-7.4%, and the within-assay imprecision was 4.1-9.1%. In studies of recovery and linearity on dilution, measured values ranged from 84% to 115% of expected at concentrations of 0.26-10.4 mIU/L. Results of the new assay (mIU/L) = 0.109 x TK REA (U/L) + 0.092. Heterophilic antibodies did not interfere in the assay. The upper 95th percentile, in 100 healthy individuals, was 0.94 mIU/L, and the median value was 0.43 mIU/L.

CONCLUSION

The TK1 enzyme-labeled immunoassay uses a stable substrate, is precise, appears to be accurate, and is resistant to interferences. It may provide a practical tool in the management of hematologic malignancies.

Production and characterisation of a novel chicken IgY antibody raised against C-terminal peptide from human thymidine kinase 1

Egg yolk is a good source of highly specific antibodies against mammalian antigens because of the phylogenetic distance between birds and mammals. Chicken egg yolk immunoglobulins (IgY) were generated to a synthetic 31-amino acid peptide from the C-terminal of human HeLa thymidine kinase 1 (TK1) enzyme. The anti-TK1 IgY antibody was purified using affinity chromatography against the 31-amino acid peptide. The purified antibody inhibited the catalytic activity of the TK1 enzyme in the CEM TK1(+) cells and recognized the 25-kDa subunit and tetrameric form of TK1, which has a pI value of 8.3. No immunoreaction was observed in CEM TK1(-) cells. Western blot of the serum TK1 (S-TK1) also showed that only a single band was found in the serum of patients with malignancies. No band was seen in healthy serum. Furthermore, dot blots and enhanced chemiluminescence (ECL) detection of S-TK1 performed on sera of preoperative patients with gastric cancer (GC) (n=31) and healthy controls (n=62) showed that the levels of S-TK1 in the sera of cancer patients were significantly different (P<0.01). Using ECL dot blots, 0.1 pg of TK1 in 3 microl sera could be detected. Immunohistostaining of tissues in the 11 advanced-stage cancer patients (four breast carcinomas, three hepatocarcinomas and four thyroid carcinomas) indicated that a strong staining of TK1 enzyme was found in the cytoplasm of malignant cells. No staining or weak staining was seen in normal tissues. We suggest that screening for TK1 using anti-TK1 IgY may be potentially useful for serological and immunohistochemical detection of TK1 as an early prognosis and for monitoring patients undergoing treatment.

Thymidine kinase in epithelial ovarian cancer: relationship with the other pyrimidine pathway enzymes

TK is a pyrimidine metabolic pathway enzyme involved in salvage DNA synthesis. What roles TK may play in epithelial ovarian cancer and the relationships between TK and the other pyrimidine pathway enzymes remain unclear. We examined TK1 gene expression by RT-PCR and related it to gene expression of TS, TP and DPD in 69 samples from epithelial ovarian cancer, 8 low-malignant-potential tumors, 16 benign ovarian tumors and 34 normal ovaries. Additionally, cytosolic and serum TK activities were determined by radioenzymatic assay. TK1 gene expression, the ratio of TK1 to TS gene expression, that of TK1 to TP and that of TK1 to DPD were significantly higher in epithelial ovarian cancer than in normal ovaries. In epithelial ovarian cancer, TK1 gene expression correlated with cytosolic and serum TK activities, TS and TP gene expression and the ratio of TP to DPD gene expression. Patients with high-TK1 gene expression had a significantly poorer survival than those with low TK1 gene expression. Combined analysis demonstrated that the relative risk of cancer death for tumors with high TK1, high TS and high TP gene expression was greater than that for tumors with high TK1 gene expression alone. TK1 gene expression together with TS, TP and DPD gene expression may play important roles in influencing the malignant behavior of epithelial ovarian cancer. Combination therapy including TK inhibitor is a possible therapeutic intervention in patients with epithelial ovarian cancer.

Retrospective study of the prognostic role of serum thymidine kinase level in CLL patients with active disease treated with fludarabine

BACKGROUND

Previous studies have shown that the serum thymidine kinase (TK) level can be used to determine prognosis in patients with lymphoproliferative diseases, but mainly those with multiple myeloma and non-Hodgkin's lymphoma. In patients with chronic lymphocytic leukemia (CLL), TK levels may provide prognostic information independent of stage and other prognostic factors, but it is still unclear whether they can be used to predict the response to treatment and length of survival.

PATIENTS AND METHODS

To determine whether TK levels can be used to predict response and survival, we retrospectively examined the serum TK level in 188 previously treated and untreated patients with active or advanced CLL who were then treated with fludarabine alone or in combination with prednisone. The correlation of the TK level with other prognostic features and with outcome was then assessed.

RESULTS

Serum TK levels were elevated in 92% of the patients, and the levels proved to associate with previous treatment, stage of disease, and other tumor-burden related features (i.e., white blood cell counts, absolute lymphocyte count, bone marrow cellularity). The levels were also directly associated with indicators of tumor cell turnover (i.e., beta2-microglobulin and lactate dehydrogenase levels). Of particular importance, we found that the TK level was a significant prognostic indicator of both response to treatment and survival. Specifically, 83% of patients with a TK level of < 10 U/L responded (complete and partial response) to treatment with fludarabine, whereas only 45% of patients with a TK level of > or = 10 U/l responded to treatment (P < 0.01). This difference was maintained when we separately analyzed untreated and previously treated patients, and in patients divided according to the Binet stage. The TK level also added prognostic information about response to a predictive model based on the hemoglobin and, albumin levels and the extent of prior treatment. Of further importance, the median survival rate in patients with a TK level of < 10 U/l was 65%, as opposed to a rate of 22% in patients with a TK level of > or = 10 U/l (P = 0.000).

CONCLUSIONS

The serum TK level in CLL patients provides useful prognostic information regarding both response to therapy and length of survival and should be used in planning appropriate therapy. In particular, patients with a TK level of > or = 10 U/l have a poor prognosis and should be considered for aggressive treatment.

Induction of thymidine kinase in mouse skin exposed to 12-O-tetradecanoylphorbol-13-acetate

Topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) exhibited an increase in the epidermal thymidine kinase (TK) activity in a dose dependent manner. Maximum induction of TK was observed at a TPA concentration of 2.5 microg per animal. The induction of TK by TPA appeared to be a function of time with the maximum TK induction between 4 and 16 h after TPA application. Repeated applications of TPA every 24 h did not show any cumulative effect rather TK activity appeared to be normal after two applications. However, repeated applications of TPA at an interval of 48 h exhibited increased TK activity even after 16 applications. Cycloheximide and actinomycin D, the inhibitors of protein and RNA synthesis, inhibited the TPA induced activation of TK. Our results demonstrated that TPA induced the TK activity may be, by increasing de novo synthesis of enzyme protein and this induction might lead to increased de novo DNA synthesis after TPA application. DMBA was used as a reference compound. As far as the authors are aware, this is the first report on TK induction by topical application of TPA.

Co-expression of thymidine kinase and cathepsin D in 200 primary breast carcinomas

We assayed thymidine kinase (TK) and cathepsin D (Cath-D) in 200 breast carcinomas and we found that they were significantly correlated. This correlation was present in lymph node positive tumours, in G2 and G3, in T1 and in invasive ductal carcinomas. In addition, TK and Cath-D did not correlate with oestrogen receptor (ER) and progesterone receptor (PgR) status. We conclude that the relationship between Cath-D and TK may indicate a tumour population of high proliferation activity and invasiveness potential, related to a more aggressive phenotype, whose identification may be useful in defining prognosis.

Neuron-specific enolase, thymidine kinase, and tissue polypeptide-specific antigen in diagnosis and response to chemotherapy of small-cell lung cancer

The clinical usefulness of neuron-specific enolase (NSE), thymidine kinase (TK), and tissue polypeptide-specific antigen (TPS) was investigated in 41 patients (53-80 years old) with recently discovered small-cell lung cancer (SCLC). Eleven patients exhibited limited disease (LD) and 30 extensive disease (ED). Serum samples for NSE, TPS (immunoradiometric assay), and TK (radioenzymatic assay) evaluations were drawn from all patients at the time of diagnosis and before each cycle of chemotherapy in the treated patients. Therapy consisted of i.v. carboplatin 300 mg/m2 on the first day and i.v. etoposide 120 mg/m2 from the first to the third day every 3 weeks. Nine patients refused or were not eligible for chemotherapy. Five patients received only one course and showed no response (NR); 9 patients received two courses; 18 patients received three or more courses. In the last group, complete remission (CR) was obtained in 9 cases, partial remission (PR) in 18 cases. The tumor markers studied did not show any significant difference in distinguishing LD from ED. NSE and TPS were significantly more often abnormal than TK, either at the time of diagnosis (p < 0.05) or in PR or NR patients (p < 0.05). In relation to chemotherapy response, NSE and TPS serum patterns were shown to be more reliable than TK in PR (p < 0.05) and NR patients (computed error between 10% and 15%). No significant difference was observed between serum NSE and TPS patterns. Serum NSE and TPS seem to be more useful in the diagnosis and follow-up of SCLC patients undergoing chemotherapy. Further trials are necessary to ascertain whether the associated assessment of NSE and TPS can add useful information to that provided by the assessment of NSE alone.

Serum thymidine kinase levels are elevated and exhibit diurnal variations in patients with advanced ovarian cancer

Deoxythymidine kinase (TK) is an enzyme involved in DNA synthesis whose serum activity reflects the proliferative activity of tumors and correlates with prognosis in various malignancies. In ovarian cancer, the value of s-TK has not been studied so far. Therefore the serum levels of TK were investigated in patients with advanced ovarian cancer. Because considerable diurnal fluctuations of s-TK levels were reported previously, repeated determinations were performed over a 48-h time span. Fourteen patients (mean age +/- S.D., 56.1 +/- 8.0 years) with advanced ovarian cancer and five healthy volunteers (30.2 +/- 3.5 years) were studied. Serial determinations of s-TK and serum CA 125 (s-CA 125) levels were performed over a 48-h time period. S-TK and s-CA 125 were elevated (> 4.7 U/l and > 35 U/ml) in 10 patients at least once over the 48-h period, respectively. Linear regression analysis showed a strong correlation between s-TK and s-CA 125. However, three patients with consistently normal s-CA 125 values (< or = 35 U/ml) had elevated s-TK levels, indicating that these two parameters may be independent in some patients. Both s-TK and s-CA 125 levels showed considerable diurnal changes over the 24-h period in individual patients, in marked contrast to normal subjects. Individual peak-trough differences ranged from 0.1-8.5 U/l or 5-268% for s-TK, and from 4-75 U/ml or 15-100% for s-CA 125. Peak-trough differences of s-TK > or = 100% were found in five patients. The circadian fluctuations of s-TK and CA 125 did not show a regular circadian pattern nor any temporal covariation. This study demonstrates for the first time that s-TK levels may be elevated in ovarian cancer. In some patients, s-TK levels may exhibit considerable, irregular diurnal fluctuations. Repeated determinations should therefore be performed in situations where this marker is relevant for patient monitoring.

Plasma thymidine kinase activity in dogs with lymphoma and leukemia

Plasma thymidine kinase (TK) activity was evaluated as a plasma marker for canine lymphoma and leukemia. A tentative "cut-off" value was set at 6.0 U/l as the upper level of plasma TK based on the mean + 2SD of plasma TK activity in 13 clinically healthy dogs. The levels of plasma TK activity in all of the 20 dogs with lymphoma and leukemia were higher than the cut-off value, whereas those in dogs with lymphoma decreased in parallel with the reduction of the tumor mass after chemotherapy. These findings suggested that estimation of plasma TK activity can be used as a plasma marker for lymphoma and leukemia in the dog.

Trypanosoma cruzi: use of herpes simplex virus-thymidine kinase as a negative selectable marker

Trypanosoma cruzi, the protozoan that causes Chagas' disease, was transfected with a fusion gene of hygromycin phosphotransferase and herpes simplex virus-thymidine kinase, HyTK. Transfectants selected in hygromycin had thymidine kinase activity, whereas controls did not. In vitro growth of the mammalian life-stage forms, amastigotes and trypomastigotes, was inhibited 98% by the nucleoside analogue ganciclovir (5 micrograms/ml). Growth of the insect-stage form, epimastigotes, was not inhibited by ganciclovir (up to 250 micrograms/ml) or other nucleoside analogues. Intracellular uptake of ganciclovir by epimastigotes was found to be 10-fold less than that by amastigotes. Mice infected with the HyTK-expressing parasites and treated with ganciclovir had a statistically significant reduction of parasitemia by 57%; however, complete eradication of parasites was not achieved. The parasites recovered from the treated mice continued to be susceptible to ganciclovir in vitro. Parasite clones with higher expression of thymidine kinase were more sensitive to ganciclovir, suggesting that greater expression of the thymidine kinase gene may lead to parasites that can be fully eradicated from infected experimental animals.

Serum beta(2)-microglobulin and serum thymidine kinase are independent predictors of progression-free survival in chronic lymphocytic leukemia and immunocytoma

Chronic lymphocytic leukemia (CLL) and immunocytoma (IC) are remarkably heterogeneous with regard to their clinical course. The current staging systems can distinguish prognostic subgroups, but do not seem to predict the risk of disease progression of an individual patient with sufficient accuracy. Given the increase of treatment options for CLL and IC, additional parameters are needed to decide which patients may benefit from early or intensified treatment. It has been shown that two biochemical markers, serum beta 2-microglobulin (s-beta 2M) and serum thymidine kinase (s-TK), might identify CLL and IC patients at high risk of disease progression. Therefore, the prognostic value of these two serum parameters was compared with a panel of several established prognostic factors in a prospective clinical trial. 113 patients with CLL and 41 patients with IC (mean age +/- SD 63.9 +/- 10.7 years) were included. The following parameters were determined: histopathological diagnosis (IC vs. CLL), age, sex, performance status (Karnofsky index), B symptoms, peripheral blood lymphocyte count, platelet count, blood hemoglobin, serum lactate dehydrogenase (s-LDH), s-beta 2M, s-TK, serum creatinine, number of lymph node areas involved, prior therapy, and the time from diagnosis to inclusion in the study. Univariate analyses showed that nine parameters (Karnofsky index, peripheral blood lymphocytosis, platelet count, blood hemoglobin, lymph node areas involved, pretreatment, s-LDH, s-beta 2M, and s-TK) significantly predicted progression-free survival. In a Cox regression model, only four of these parameters provided independent prognostic information on progression-free survival: 1. s-beta 2M, 2. Karnofsky index, 3. platelet count, and 4. s-TK. The results show that s-beta 2M and s-TK independently predict progression-free survival in patients with CLL and IC, and suggest that these prognostic factors may allow an improved prediction of progression-free survival, particularly in early disease stages.

Deoxythymidine kinase in the staging of prostatic adenocarcinoma

The role of prostate-specific antigen in the management of prostatic adenocarcinoma is still not fully ascertained. Its place in the monitoring of patients who have undergone radical treatment is without question but its role in the primary assessment of a lesion is a point of continuous discussion. This study reports the analysis of prostate-specific antigen (PSA) in 92 patients with different stages of prostatic adenocarcinoma prior to treatment; in the case of the localized lesions, this was based to a great extent on the findings at lymphadenectomy. Apart from PSA analysis, deoxythymidine kinase (dTK) analyses were also performed in an attempt to discover whether the latter could provide additional information about the tumor load in the different patient categories, viz. those with lymph node involvement (group 1), those with lymph node involvement but without distant metastases (group 2), and those with disseminated disease (group 3). The median PSA and dTK values in groups 1-3 were 6.5 micrograms/L and 2.7 U/microliter, 16 micrograms/L and 2.6 U/microL, and 90 micrograms/L and 7.8 U/microL, respectively. If the two analyses were used concomitantly, they could differentiate true localized disease from metastatic in approximately 92% of cases. The combination should prove of value in the primary assessment of a patient with a newly diagnosed prostatic adenocarcinoma.

Rat peripheral mononuclear cell thymidine kinase activity increases during liver regenerative processes after partial hepatectomy

Deoxythymidine kinase (TK; EC 2.7.1.21) activity in the liver has been used as a marker of liver regeneration after partial hepatectomy. In this study we examined TK activity of various organs, plasma and peripheral blood mononuclear cells (PMNC) in 70% partially hepatectomized rats. TK activity of lymph nodes, small intestine, heart, lung, kidney and thymus did not increase significantly during the course of the study, except for spleen at 72 h. On the other hand, PMNC-TK and liver cystosolic TK activity increased in a parallel fashion at all times after partial hepatectomy; they began to increase 12 h after surgery and peaked 48 h post-surgery. Fractionation of PMNC into T cells and B cells revealed that both populations increased and peaked 48 h post-surgery. Plasma TK peaked 12-24 h after surgery, then declined at 36, 48 and 72 h after partial hepatectomy. This change paralleled plasma levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). PMNC-TK activity correlated significantly with liver cystosolic TK activity 24 h (r = 0.743; P < 0.05) and 48 h (r = 0.708; P < 0.05) after partial hepatectomy. However, it did not correlate with plasma levels of TK, AST and ALT. The results indicate that in the early stage of liver regeneration PMNC-TK may provide a marker of liver regenerative processes.

Deoxythymidine kinase in the tumour cells and serum of patients with non-Hodgkin lymphomas

The levels of deoxythymidine kinase in tumour cells (C-TK) and in serum (S-TK) were investigated and the tumour volume calculated in 89 patients with non-Hodgkin lymphoma (NHL), in order to ascertain the importance of C-TK and tumour burden as regards the S-TK levels. Among all patients, a correlation was seen between S-TK and tumour volume but not between S-TK and C-TK. However, within different tumour volume categories (small, medium-sized and large), there was a correlation between S-TK and C-TK. Multiple regression analysis supported this notion. C-TK correlated with the proliferation-associated parameters, S-phase fraction and mitotic index. As already known, S-TK was found to have a strong prognostic value. C-TK and tumour burden were also of prognostic value. In multivariate analyses, C-TK and tumour volume did not provide prognostic information in addition to S-TK, whereas, in the absence of S-TK, C-TK and tumour volume did provide additional information. It is concluded that the serum level of TK depends on both the tumour burden and the tumour cell proliferation rate. Based upon estimations of S-TK in patients assessed shortly after chemotherapy, we also suggest that S-TK reflects the number of proliferating cells that have died during the period immediately before sampling.

Prognostic value of cytosolic thymidine kinase activity as a marker of proliferation in breast cancer

Thymidine kinase (TK) is involved in DNA synthesis by the salvage pathway. In this study, thymidine kinase (TK) was determined in routinely prepared cytosols of primary tumors from 290 breast-cancer patients. Enzyme activity was measured using a radioenzymatic method optimized for detection of the fetal isoenzyme. High levels of TK (> or = 126 mU/mg protein) were positively associated with histological grade in both pre/peri-and post-menopausal patients. In pre/peri-menopausal patients, high concentrations of TK were also found more frequently in progesterone receptor (PgR)-negative tumors than in PgR-positive samples. In post-menopausal patients, high levels of TK were associated with large tumor size, estrogen receptor (ER) negativity and PgR negativity. In univariate analysis, high levels of TK were strongly associated with shorter overall survival in both pre/peri- (p = 0.001) and post-menopausal patients (p = 0.02). Pre/peri-menopausal patients whose tumors had high levels of TK also had an increased risk of relapse (p = 0.001). In multivariate analysis (including treatment protocol, patient age, lymph-node involvement, tumor size, histological grade, ER and PgR status), TK status was found to be an independent prognostic factor for recurrence-free survival in pre/peri-menopausal patients with a weight similar to that of PgR status. In post-menopausal patients, TK was the only factor selected for overall survival.

Serum levels of interleukin-2 receptor (CD 25) in patients with Hodgkin's disease, with special reference to age and prognosis

BACKGROUND

The serum levels of soluble interleukin-2 receptor (S-sIL-2R) have been shown to be related to clinical outcome in Hodgkin's disease (HD). sIL-2R may be involved in or aggravate the immunodeficiency seen in HD patients. This immunodeficiency is most pronounced in elderly patients.

PATIENTS AND METHODS

S-sIL-2R was determined in 127 untreated patients with HD, diagnosed between 1979 and 1991, in order to evaluate its prognostic value in relation to other known prognostic variables with special emphasis on the elderly.

RESULTS

S-sIL-2R levels were significantly higher in patients with stages III-IV and with B-symptoms (p < 0.001) but not in patients over 60 years of age. In multivariate analyses, S-sIL-2R, stage and S-orosomucoid were the most important prognostic factors in all patients and S-sIL-2R was the only prognostic factor in patients over the age of 60.

CONCLUSIONS

The results indicate a future role for estimation of S-sIL-2R in the management of patients with HD.

Serum thymidine kinase in congenital dyserythropoietic anaemia type III

Serum thymidine kinase (TK) was determined in a family with congenital dyserythropoietic anaemia type III (CDA, type III). 20 patients and 10 of their healthy siblings were investigated. Elevated TK was found in all 20 patients (median 56.2 U) but their healthy siblings had normal values (median 2.65 U). We suggest that determination of TK should be used for discrimination between healthy siblings and individuals affected by CDA type III when bone marrow examination is not suitable.

Thymidine kinase activity in liver and serum of rats after cadmium administration

Intraperitoneal administration of a cadmium (Cd) salt at concentrations of 2.5 and 4.0 mg CdCl2/kg of body wt., caused time-dependent severe liver injury, in Quinster rats, more intense at the higher administered dose. Thymidine kinase, the key enzyme of the salvage pathway of DNA biosynthesis, was strongly affected in liver tissue and serum of cadmium-intoxicated rats. Lower thymidine kinase activity was observed both in liver and serum of rats treated with the higher dose of cadmium, in which the maximal liver injury appeared.