Managing hemolysis in serum neuron-specific enolase measurements - an automated algorithm for routine practice.

Neuron-specific enolase (NSE) derived from neurons and peripheral neuroendocrine cells is a biomarker for neuroendocrine tumors and for prognostication in comatose cardiac arrest survivors. However, as platelets and erythrocytes contain NSE, hemolysis causes falsely elevated NSE. We used native serum and hemolysate derived from the same patients to make serial dilutions, and subsequently measured NSE (mNSE) and hemolytic index (HI) in each dilution. An algorithm suitable for the laboratory information system was developed based on the mNSE, HI and the estimated gradient of hemolytic interference from 30 patients. We estimated the associated uncertainty of the corrected NSE (cNSE) results based on the observed range of the gradient and derived an equation for cNSE for samples with limited hemolysis (i.e. 5 < HI ≤ 30): cNSE = mNSE - HI × (0.34 ± 0.23) µg/L. By semi-quantitatively grading the contribution from limited hemolysis, a texted result noting the hemolysis-associated degree of uncertainty can accompany the cNSE result. The major challenge of hemolysis when using serum NSE as a biomarker can be managed using an automated algorithm for correction of NSE results based on degree of hemolysis. However, laboratorians and clinicians should be aware of the limitations associated with in vivo hemolysis.

Thyroid hypofunction in aging testicular cancer survivors.

PURPOSE: Thyroid hypofunction is a late effect observed in several groups of cancer survivors, but has to date not been evaluated in-depth in testicular cancer survivors (TCSs). We investigated the prevalence of thyroid hypofunction in long-term TCSs and compared the findings with those of a comparison group from the general population. PATIENTS AND METHODS: Norwegian TCSs diagnosed with unilateral testicular cancer in the period 1980-1994 (N = 1,436) were grouped according to their cancer treatment (Surgery only; Radiotherapy only; Cisplatin-based chemotherapy, eventually combined with radiotherapy). They were invited to participate in three surveys covering up to three decades post-diagnosis. Serum thyrotropin (s-TSH) from samples collected from the last survey were analyzed. S-TSH results were also available from a health survey of the general population performed in a county in mid-Norway (the HUNT3 Survey [comparison group]). Data on the prescription of thyroid hormone replacement therapy (levothyroxine) from the Norwegian Prescription Database were obtained for the TCSs and the comparison group's participants. Thyroid hypofunction was defined as 'untreated' (overt or subclinical) hypothyroidism (with s-TSH ≥3.5 mIU/L and no regular prescription of levothyroxine) or 'treated' hypothyroidism with regular prescription of levothyroxine. RESULTS: Three decades after diagnosis the prevalence of thyroid hypofunction (i.e., both treated and untreated) was 11% in the TCSs and the prevalence ratio was 1.9 indicating an almost doubled prevalence in the TCSs compared to the comparison group (prevalence ratio 1.91, 95% CI [1.54; 2.38]). However, there were no significant differences in the risk of thyroid hypofunction related to the TCSs' treatment modality. CONCLUSION: TCSs may have an increased prevalence of thyroid hypofunction compared to the general population. Hypothyroidism has negative consequences related both to primary hypogonadism and to cardiovascular disease. As both conditions are overrepresented in TCSs, regular monitoring of thyroid hormones may be advisable.

Longitudinal kidney function outcome in aging testicular cancer survivors.

Purpose: Testicular cancer survivors (TCSs) have increased risk of reduced kidney function related to treatment burden, but longitudinal studies of renal outcome in aging TCSs have been lacking. This longitudinal study describes age- and treatment-related kidney function changes in TCSs compared to a comparison group from the general population.Patients and methods: Estimated glomerular filtration rate (eGFR) was determined in blood samples from Norwegian TCSs (diagnosed 1980-1994) and surveyed median 11, 19 and 26 years since diagnosis (Survey1 [N = 1273], 2 [N = 849] and 3 [N = 670]) defining four treatment groups; Surgery only, Radiotherapy (RT) only, Cisplatin-based chemotherapy (CBCT) ≤850 mg and High CBCT/RT >850 mg cisplatin or any combination of CBCT with RT. A comparison group was constructed from similarly aged men who participated in a population-based health survey. By multiple linear regressions and generalized mixed models for repeated measurements, we studied difference in eGFR between TCSs and the comparison group for all TCSs combined and stratified by treatment modality.Results: At Survey 1, the kidney function for the youngest TCSs combined versus the comparison group was significantly reduced by mean six units (mL/min/1.73 m2) with further decline to mean 12 units at Survey 3. The kidney function was significantly reduced in all treatment groups with the largest differences emerging for TCSs from the High CBCT/RT Group, thus indicating a deteriorating impact of high cumulative doses of cisplatin.Conclusion: Collated to the comparison group, the kidney function in TCSs became increasingly impaired during nearly three post-treatment decades, related to the treatment modality. Early detection and intervention of kidney dysfunction is important to reduce the risk of TCSs' long-term morbidity and mortality related to nephrotoxicity, such as cardio-vascular diseases.

Lowered reference limits for hCG improve follow-up of patients with hCG-producing tumors.

BACKGROUND: Human Chorionic Gonadotropin (hCG) is produced by germ cell tumors, but can also be elevated in benign conditions such as primary hypogonadism, where hCG is produced by the pituitary gland. In our experience, the reference limits for hCG (Elecsys hCG+ß-assay, Roche Diagnostics), were unnecessarily high and did not reflect levels encountered in clinical practice. We wanted to establish new reference limits to increase the clinical utility of the hCG-assay. METHODS: We analysed hCG in serum samples from a healthy adult population and in a cohort of testicular cancer survivors. The gonadotropins LH and FSH were measured in the cohort and in a selection of the reference population to assess gonadal function. RESULTS: We found low hCG levels for all men and women <45years (97.5 percentiles 0.1 and 0.2IU/L, respectively) from the healthy population (n=795) having normal FSH and LH. Due to assay limitations, we suggest a common reference limit of <0.3IU/L. For the age group ≥45, the 97.5 percentiles in the healthy population were 0.5IU/L for men and 6.0IU/L for women. In all subjects from both the reference population and the cohort (n=732), hCG levels exceeding the reference limit could be fully explained by reduced gonadal function indicated by elevated LH and FSH levels. CONCLUSION: The Elecsys hCG+ß-assay should have lower reference limits than recommended by the manufacturer, with important implications for tumor follow-up. Elevated hCG is rare with intact gonadal function, both in a normal population and among survivors of testicular cancer, and should lead to further investigations when encountered in clinical practice.

Radiosensitization of colorectal carcinoma cell lines by histone deacetylase inhibition.

BACKGROUND: The tumor response to preoperative radiotherapy of locally advanced rectal cancer varies greatly, warranting the use of experimental models to assay the efficacy of molecular targeting agents in rectal cancer radiosensitization. Histone deacetylase (HDAC) inhibitors, agents that cause hyperacetylation of histone proteins and thereby remodeling of chromatin structure, may override cell cycle checkpoint responses to DNA damage and amplify radiation-induced tumor cell death. METHODS: Human colorectal carcinoma cell lines were exposed to ionizing radiation and HDAC inhibitors, and cell cycle profiles and regulatory factors, as well as clonogenicity, were analyzed. RESULTS: In addition to G(2)/M phase arrest following irradiation, the cell lines displayed cell cycle responses typical for either intact or defective p53 function (the presence or absence, respectively, of radiation-induced expression of the cell cycle inhibitor p21 and subsequent accumulation of G(1) phase cells). In contrast, histone acetylation was associated with complete depletion of the G1 population of cells with functional p53 but accumulation of both G(1) and G(2)/M populations of cells with defective p53. The cellular phenotypes upon HDAC inhibition were consistent with the observed repression of Polo-like kinase-1, a regulatory G(2)/M phase kinase. Following pre-treatment with HDAC inhibitors currently undergoing clinical investigation, the inhibitory effect of ionizing radiation on clonogenicity was significantly amplified. CONCLUSION: In these experimental models, HDAC inhibition sensitized the tumor cells to ionizing radiation, which is in accordance with the concept of increased probability of tumor cell death when chromatin structure is modified.

DNA damage responses in cell cycle G2 phase and mitosis--tracking and targeting.

BACKGROUND: In order to determine temporal responses of cell cycle populations to DNA damage, a rational combination of cell cycle analyses is critical. Moreover, the targeting of cell cycle checkpoint responses may modify the cytotoxic effect of DNA damage. MATERIALS AND METHODS: The characteristics of cell cycle populations (DNA content, cell cycle transitioning of S phase cells and size of mitotic cell fraction within the total G2/M phase population) in HeLa cells exposed to ionizing radiation were analyzed using three individual flow cytometry-based assays. The potential radiosensitization from inhibiting DNA damage responses was assessed by the colony formation assay. RESULTS: Irradiation resulted in an initial accumulation of S phase cells in G2 phase, from which the arrested cells were subsequently released to enter mitosis. Upon drug inhibition of G2 checkpoint signaling or mitotic progression, the cytotoxic effect of ionizing radiation on the HeLa cells was amplified. CONCLUSION: DNA damage-induced cell cycle responses, analyzed by selected cytometry assays and modified by specific targeting, might contribute to an understanding of how to improve radiotherapy outcome.

Cell cycle checkpoint signaling involved in histone deacetylase inhibition and radiation-induced cell death.

In breast cancer, radiation has a central role in the treatment of brain metastasis, although tumor sensitivity might be limited. The tumor cell defense response to ionizing radiation involves activation of cell cycle checkpoint signaling. Histone deacetylase (HDAC) inhibitors, agents that cause hyperacetylation of histone proteins and thereby aberrations in the chromatin structure, may also override the DNA damage defense response and facilitate the radiation-induced mitotic cell death. In experimental metastasis models, the human breast carcinoma cell line MA-11 invariably disseminates to the central nervous system. We compared profiles of in vitro MA-11 cell cycle response to ionizing radiation and HDAC inhibition. After radiation exposure, the G2-M phase accumulation and the preceding repression of the G2 phase regulatory factors Polo-like kinase-1 and cyclin B1 required intact G2 checkpoint signaling through the checkpoint kinase CHK1, whereas the similar phenotypic changes observed with HDAC inhibition did not. MA-11 cells did not show radiation-induced expression of the G1 cell cycle inhibitor p21, indicative of a defective G1 checkpoint and consistent with a point mutation detected in the tumor suppressor TP53 gene. Increase in the p21 level, however, was observed with HDAC inhibition. Following pretreatment with the HDAC inhibitor, the efficiency of clonogenic regrowth after irradiation was reduced, which is in accordance with the concept of increased probability of mitotic cell death when the chromatin structure is disrupted. Among molecular cell cycle-targeted drugs currently in the pipeline for testing in early-phase clinical trials, HDAC inhibitors may have therapeutic potential as radiosensitizers.

Inhibitory targeting of checkpoint kinase signaling overrides radiation-induced cell cycle gene regulation: a therapeutic strategy in tumor cell radiosensitization?

BACKGROUND AND PURPOSE: The tumor cell defense response to ionizing radiation involves a temporary arrest at the cell cycle G(2) checkpoint, which is activated by a signaling cascade initiated by the ATM kinase response to DNA damage, ultimately leading to the outcome of further cell survival if the DNA is properly repaired. The inhibitory targeting of the checkpoint kinase signaling elicited by ATM may define a biologically based strategy to override the G(2) phase delay that prevents mitotic entry after DNA damage, thereby increasing the probability of mitotic cell death following exposure to ionizing radiation. MATERIALS AND METHODS: Breast carcinoma cell lines with intact or defective function of the tumor-suppressor protein BRCA1 were exposed to ionizing radiation in the absence or presence of a specific inhibitor (UCN-01) of the checkpoint kinase CHK1, and the response profiles of cell cycle distribution and G(2) phase regulatory factors, as well as the efficiency of clonogenic regrowth, were analyzed. RESULTS: The radiation-induced G(2) phase accumulation was preceded by a transient down-regulation of the G(2) phase-specific polo-like kinase-1 and cyclin B1, which required intact function of both BRCA1 and CHK1. The concomitant treatment with UCN-01 seemed to amplify the cytotoxic effect of ionizing radiation on clonogenic regrowth. CONCLUSION: The effector mechanism of DNA damage on cell cycle gene regulation signals through the checkpoint kinase network. Among molecular cell cycle-targeted drugs currently in pipeline for testing in early phase clinical trials, CHK1 inhibitors may have therapeutic potential as radiosensitizers.

Repression of mRNA for the PLK cell cycle gene after DNA damage requires BRCA1.

DNA damage activates the G2 cell cycle checkpoint to allow time for DNA repair before mitotic entry. The mechanism involves inhibition of the enzymatic activity for polo-like kinase 1 (Plk1), rendering Cdc25C with a basal phosphatase activity that is insufficient for converting Cdc2 to the fully active G2/M transition kinase. We found that cell cycle arrest at the G2/M boundary after ionizing radiation (IR) of breast carcinoma cells may involve repression of the gene for Plk1, PLK, mediated by the tumor-suppressor protein BRCA1. The p53-defective MT-1 cell line had an apparent accumulation of G2/M phase cells 12 h after irradiation. This response was preceded by a transient downregulation of PLK mRNA expression with a barely detectable level 6 h after exposure to IR but recovered after 12 h. A significantly lower fraction of irradiated BRCA1(-/-) HCC1937 cells arrested in the G2/M phase after 12 h, and the transient response of PLK mRNA was also considerably impaired. After reconstitution of wild-type BRCA1 in the HCC1937 cells however, downregulation of PLK mRNA as well as Plk1 protein expression after IR was restored. Moreover, the suppression of PLK mRNA expression 6 h after irradiation was completely abolished by the specific CHEK1 kinase inhibitor UCN-01, further indicating that the effector mechanism of DNA damage on PLK signals through BRCA1 and its downstream CHEK1. Our observations provide new information about the diversity of regulatory mechanisms governed by BRCA1 in DNA damage checkpoint control.