Determination of serum total lipid and free N-acetylneuraminic acid in genitourinary malignancies by fluorimetric high performance liquid chromatography. Relevance of free N-acetylneuraminic acid as tumour marker

The use of multicomponent reactions in the development of bis-boronic acids for the detection of β-sialic acid

Sialic acid (SA) is a naturally occurring monosaccharide found in glycoproteins and glycolipids. Changes in the expression of SA are associated with several diseases; thus, the detection of SA is of great significance for biological research, cancer diagnosis, and treatment. Boronic acid analogs have emerged as a promising tool for detecting sugars such as SA due to its reversible covalent bonding ability. In this study, 11 bis-boronic acid compounds and 2 mono-boronic acid compounds were synthesized via a highly efficient Ugi-4CR strategy. The synthesized compounds were subjected to affinity fluorescence binding experiments to evaluate their binding capability to SA. Compound A1 was shown to have a promising binding constant of 2602 ± 100 M-1 at pH = 6.0. Density Functional Theory (DFT) calculations examining the binding modes between A1 and SA indicated that the position of the boronic acid functional group was strongly correlated with its interaction with SA's α-hydroxy acid unit. The DFT calculations were consistent with the observations from the fluorescence experiments, demonstrating that the number and relative positions of the boronic acid functional groups are critical factors in enhancing the binding affinity to SA. DFT calculations of both S and R configuration of A1 indicated that the effect of the S/R configuration of A1 on its binding with β-sialic acid was insignificant as the Ugi-4CR generated racemic products. A fluorine atom was incorporated into the R2 substituent of A1 as an electron-withdrawing group to produce A5, which possessed a significantly higher capability to bind to SA (Keq = 7015 ± 5 M-1 at pH = 6.0). Finally, A1 and A5 were shown to possess exceptional binding selectivity toward β-sialic acid under pH of 6.0 and 6.5 while preferring to bind with glucose, fructose, and galactose under pH of 7.0 and 7.5.

Validade dos marcadores tumorais

Considerando-se o número crescente dos chamados marcadores tumorais e a sua incorporação sistemática à prática médica, procedeu-se a um levantamento, por meio de Medline® 1995, na Biblioteca Central do Instituto Nacional de Câncer - INCA, e revisão de 95 resumos de trabalhos publicados de 1995 a abril de 1997. Verificou-se que a validade dos marcadores é maior para o diagnóstico patológico de alguns tipos tumorais e determinação de alguns fatores prognósticos; que poucos são os de real utilidade clínica, seja para prevenção, diagnóstico ou prognóstico, vez que a maioria deles só alcança significância quando a doença já provoca algum sinal ou sintoma; que a maioria das referências correspondem, a rigor, a trabalhos repetidos, que avaliam os mesmos marcadores, embora em diferentes tumores; e que há trabalhos que se referem a poucos casos, quando não pouquíssimos, e cujos resultados tomam-se, por isso, inconsistentes. Neste artigo, os marcadores tumorais são classificados por tipos (genes, expressões genéticas, substâncias circulantes, substâncias celulares, receptores da membrana celular e índices de proliferação tumoral) e por finalidades (prevenção, detecção, diagnóstico, estadiamento, monitoração terapêutica, seguimento pós-tratamento e prognóstico) e são correlacionados com o(s) tumor(es) em que foram pesquisados. Apresentam-se três grupos de critérios de validação (estatísticos, biomédicos e por finalidades) e resume-se, a partir também de mais 16 outras referências bibliográficas, a utilidade de marcadores dos cânceres de mama [ADN, fração de Fase S, índice de ADN, C-erbB-2 (HER-2/neu), P53, CAT-D, CA15.3 e CEA - sem validade; marcadores tumorais hormonais - úteis para a indicação de hormonioterapia adjuvante ou paliativa]; colorretal [LASA, CA 19.9, índice de ADN, fração de Fase S, p53 e ras - sem validade; CEA-com validade para estadiamento e planejamento cirúrgico, e para seguimento pós-operatório (dosagem seriada a cada 2-3 meses por 2 anos, se houve suspeita de metástase hepática em estádios cirúrgicos II e III)] e de próstata (PSA com utilidade para a detecção, mas associado ao toque retal, em homens acima de 40-50 anos, como indicativos da necessidade de exames mais acurados, e para o seguimento dos casos tratados). E inquestionável a utilidade da dosagem de alfa-feto-proteína (aFP) e da gonadotrofina coriônica (hCG), para o estadiamento, tratamento, avaliação da resposta terapêutica e seguimento dos casos tratados de tumores testiculares (aFP e hCG) e de neoplasia trofoblástica gestacional (hCG). Também inquestionável é o papel da identificação dos marcadores de diferenciação celular no diagnóstico patológico de leucemias e linfomas. Os dilemas evidenciados a partir deste estudo referem-se a cinco binômios: 1) ausência de sinal ou sintoma versus positividade de marcador tumoral; 2) detecção de recidiva assintomática versus a qualidade e a quantidade da sobrevida do indivíduo; 3) natureza da causa versus aumento do marcador; 4) exame falso-positivo versus tratamento; e 5) baixo risco de evolução de neoplasia detectada versus tratamento. Conclui-se que, exceto pelos marcadores de validade estabelecida para o diagnóstico, o seguimento do tratamento ou o prognóstico dos casos de alguns cânceres, o médico precisa, além de conhecer os marcadores tumorais e suas siglas, saber os limites das suas indicações e ter opinião, crítica e método na sua utilização.

NEU4 inhibits motility of HCC cells by cleaving sialic acids on CD44

Hepatocellular carcinoma (HCC) is an extremely metastatic tumor. Sialic acids (SAs) are associated with cancer development and metastasis. NEU4 is a sialidase that removes SAs from glycoconjugates, while the function of the NEU4 in HCC has not been clearly explored. In our research, we found the NEU4 expression was significantly down-regulated in HCC tissues, which was correlated with high grades and poor outcomes of HCC. The NEU4 expression could be regulated by histone acetylation. In the functional analysis of NEU4, the cell motility was inhibited when NEU4 was overexpressed, and restored when NEU4 expression was down-regulated. Similarly, NEU4 over-expressed HCC cells showed less metastasis in athymic nude mice. Further study revealed that NEU4 could inhibit cell migration by enzymatic decomposition of SAs. Our results verified a NEU4 active site (NEU4E235) and overexpressing inactivates NEU4E235A that weakens the inhibition ability to cell migration. Further, 70 kinds of specific interacting proteins of NEU4 including CD44 were identified through mass spectrum. Moreover, the α2,3-linked SAs on CD44 were decreased and the hyaluronic acid (HA) binding ability was increased when NEU4 over-expressed or activated. Additionally, the mutation of CD44 with six N-glycosylation sites showed less sensibility to NEU4 on cell migration compared with wild-type CD44. In summary, our results revealed the mechanism of low expression of NEU4 in HCC and its inhibitory effect on cell migration by removal of SAs on CD44, which may provide new treatment strategies to control the motility and metastasis of HCC.

Evaluation of the value of Preoperative Sialic Acid Levels in Diagnosis and Localization of Urothelial Tumors

Objective: To explore SA levels in the serum of urothelial tumor patients and their correlation with clinical pathological features and localization. Materials and Methods: Our research retrospectively collected data from 591 patients with urothelial tumors between July 2014 and April 2018. The SA levels in the serum of urothelial tumor patients and their correlation with clinical pathological features and localization were investigated. Univariate and multivariate logistic regression analyses were further performed to identify independent associations. Results: The levels of SA were significantly associated with the malignant degree (tumor grade and infiltration) of bladder cancer and tumor localization (all p < 0.05). The multivariate logistic regression model showed that SA levels were independently associated with the presence of high-grade urothelial carcinoma (BUC: HR = 1.941, UTUC: HR = 3.820, all p <0.05) and upper urinary tract urothelial carcinoma (HR = 2.047, p < 0.05). Finally, we validated the diagnosis and localization value of SA in an independent cohort from another institutions. Conclusions: Elevated serum SA levels are an independent predictor of high-grade urothelial carcinoma and upper urinary tract urothelial carcinoma, indicating that SA levels may be a potential biomarker for the diagnosis, prognosis and localization of urothelial tumors.

Elevated urinary total sialic acid and increased oxidative stress in patients with bladder cancer

Background: Increased production and release of sialic acid have been reported in many malignant conditions including bladder cancer. 8-hydroxydeoxyguanosine (8-OHdG) and malondialdehyde (MDA) have been widely used as oxidative stress biomarkers. Objective: Determine urinary levels of total sialic acid (TSA), 8-OHdG, and MDA in patients with urinary bladder cancer, and evaluate their clinical relevance. Patients and methods: Forty-five patients with histologically proven bladder cancer and 41 healthy subjects were recruited for the study. Morning urine samples were collected from all participants for measurements of TSA, 8-OHdG and MDA using thiobarbituric assay, competitive ELISA and spectrophotometry methods, respectively. Histological examination was performed for all patients. Results: Bladder cancer patients excreted urinary TSA, 8-OHdG, and MDA significantly higher than healthy controls. Based on receiver operating characteristic curve analysis, urinary TSA had adequate diagnostic potential to distinguish patients from healthy populations, and its cutoff value was chosen at 95.26 μg/g creatinine. Sensitivity, specificity, and accuracy of urinary TSA determination were 75.6%, 75.6%, and 75.6%, respectively. Both in patient and healthy groups, urinary TSA was linearly correlated with urinary 8-OHdG. Patients with highseverity grade (n=27) excreted urinary TSA significantly greater than those with low-severity grade (n=18). Conclusion: Urinary TSA, 8-OHdG, and MDA increased in patients with bladder cancer. The elevated urinary TSA was associated with enhanced oxidative stress. In addition, urinary TSA increased with progressiveness of the tumor.

Targeted metabolomics in bladder cancer: From analytical methods development and validation towards application to clinical samples

Bladder cancer constitutes the ninth most common cancer worldwide and, despite continuous development of new diagnostic approaches, the thirteenth leading cause of global cancer mortality. In our previous untargeted urine metabolomic investigation, seventeen metabolites were found to be statistically differentiating bladder cancer patients and healthy volunteers. Therefore, the main goal of this study was to develop and validate an analytical method for simultaneous quantitative determination of those metabolites using reversed phase high-performance liquid chromatography coupled with triple quadrupole mass spectrometry technique (RP-HPLC-QQQ/MS). Different chromatographic conditions, as well as various sample treatment procedures were tested in order to provide the best separation and the lowest limit of quantification (LOQ) values for studied compounds. The validation was performed according to the Food and Drug Administration guidelines (FDA). The limit of determination (LOD) and the LOQ values were in the range of 0.21-10.51 ng/ml and 0.69-35.02 ng/ml, respectively. The concentration range of compounds was developed between 2.5 and 12500 ng/ml. Only one compound (trimethyllysine) showed a significant matrix effect (61%) and consequently low process efficiency (64%). Overall, developed method presented recovery and precision values within the ranges proposed by FDA guidelines. The optimized and validated method was applied to urine samples obtained from 40 patients with bladder cancer and 40 healthy volunteers matched according to ones of the most important risk factors for developing urinary bladder tumors, e.i. age, gender and BMI. Afterwards, statistical analysis was provided by the use of Student's t-test or U-Mann Whitney test. The developed method was sensitive, selective and reproducible to be applied for the quantification of metabolites in the investigation of urine samples. As a consequence, ten out of previously chosen seventeen compounds, participating in different metabolites' pathways (gut floral metabolism, RNA degradation, purine metabolism, etc.), were found to be statistically significantly different in the urine concentration (p < 0.05) between cancer and control groups.

Affinity Capillary Electrophoresis for Selective Control of Electrophoretic Mobility of Sialic Acid Using Lanthanide-Hexadentate Macrocyclic Polyazacarboxylate Complexes

It is difficult to control the electrophoretic mobility in order to obtain high resolution among saccharides in complex samples. We report herein on a new affinity capillary electrophoresis (ACE) method for an anionic monosaccharide, N-acetylneuraminic acid (Neu5Ac), which is important in terms of pathological diagnosis, using lanthanide-hexadentate macrocyclic polyazacarboxylate complexes (Ln-NOTA) as affinity reagents. It was shown that Ln-NOTA complexes increased the anionic mobility of Neu5Ac by approximately 40% through selective complexation with Neu5Ac. The extent of change in the mobility strongly depended on the type of central metal ion of Ln-NOTA. The stability constant (K) of Lu-NOTA with Neu5Ac was determined by ACE to be log Kb = 3.62 ± 0.04, which is the highest value among artificial receptors for Neu5Ac reported so far. Using this ACE, the Neu5Ac content in a glycoprotein sample, α1-acid glycoprotein (AGP), was determined after acid hydrolysis. Complete separation between Neu5Ac and hydrolysis products was successful by controlling the mobility to determine the concentration of Neu5Ac.

Total and free serum sialic acid concentration in liver diseases

Background. The objective of this study was to compare the levels of total (TSA) and free (FSA) sialic acid in acute and chronic liver diseases. Materials and Methods. The serum TSA and FSA levels were determined in 278 patients suffering from acute and chronic liver diseases of different etiologies. TSA was estimated by enzymatic method and FSA by the thiobarbituric method modified by Skoza and Mohos. Results. There were no significant differences in the serum TSA concentration between liver diseases of different etiologies, although in most of the liver diseases the mean TSA level was significantly lower than that in the control group. In contrast to TSA, the concentration of FSA appears to differ between liver diseases. In toxic hepatitis it was higher than that in nonalcoholic cirrhosis. However, neither of them differs between alcoholic and nonalcoholic cirrhosis or between liver tumors and tumors with cirrhosis. Conclusions. We conclude that the changes in concentrations of TSA and FSA during the same liver diseases indicate significant disturbances in sialylation of serum glycoproteins.

In vivo (1) H MR spectroscopic imaging of aggressive prostate cancer: can we detect lactate?

PURPOSE

A semi-LASER sequence was optimized for in vivo lactate detection in the prostate.

METHODS

The ethical committee waived the need for informed consent to measure 17 patients with high grade prostate cancer on a 3T system. A semi-LASER sequence was used with an echo time of 144 ms and optimized interpulse timing for a spectral citrate shape with high signal intensity. An LCModel basis set was developed for fitting choline, creatine, spermine, citrate, and lactate and was used to fit all spectra in tumor-containing voxels. For patients without detectable lactate, the minimal detectable lactate concentration was determined by adding in all spectra of tumor tissue a simulated lactate signal. The amplitude of the simulated lactate signal was iteratively decreased until its fit reached a Cramér Rao lower bound >20%, which was then set as the patient-specific detection limit.

RESULTS

In none of the patients a convincing lactate signal was found. We estimated that on average the lactate levels in high grade prostate cancer are below 1.5 mM (range 0.9-3.5 mM), Interestingly, in one patient with extensive necrosis in the tumor biopsy samples (Gleason score 5+5), large lipid resonances were observed, which originated from the tumor.

CONCLUSION

The minimal detectable lactate concentration of 1.5 mM in high grade prostate cancer indicates that if lactate is increased it remains at low concentrations.

Measurement of melatonin in body fluids: standards, protocols and procedures

BACKGROUND AND PURPOSE

The circadian rhythm of melatonin in saliva or plasma, or of the melatonin metabolite 6-sulfatoxymelatonin (a6MTs) in urine, is a defining feature of suprachiasmatic nucleus (SCN) function, the body's endogenous oscillatory pacemaker. The primary objective of this review is to ascertain the clinical benefits and limitations of current methodologies employed for detection and quantification of melatonin in biological fluids and tissues.

DATA IDENTIFICATION

A search of the English-language literature (Medline) and a systematic review of published articles were carried out.

STUDY SELECTION

Articles that specified both the methodology for quantifying melatonin and indicated the clinical purpose were chosen for inclusion in the review.

DATA EXTRACTION

The authors critically evaluated the methodological issues associated with various tools and techniques (e.g. standards, protocols, and procedures).

RESULTS OF DATA SYNTHESIS

Melatonin measurements are useful for evaluating problems related to the onset or offset of sleep and for assessing phase delays or advances of rhythms in entrained individuals. They have also become an important tool for psychiatric diagnosis, their use being recommended for phase typing in patients suffering from sleep and mood disorders. Additionally, there has been a continuous interest in the use of melatonin as a marker for neoplasms of the pineal region. Melatonin decreases such as found with aging are or post pinealectomy can cause alterations in the sleep/wake cycle. The development of sensitive and selective methods for the precise detection of melatonin in tissues and fluids has increasingly been shown to have direct relevance for clinical decision making.

CONCLUSIONS

Due to melatonin's low concentration, as well as the coexistence of numerous other compounds in the blood, the routine determination of melatonin has been an analytical challenge. The available evidence indicates however that these challenges can be overcome and consequently that evaluation of melatonin's presence and activity can be an accessible and useful tool for clinical diagnosis.

Comparing Self-Assembling and Covalent Fluorescent Boronolectins for the Detection of Free Sialic Acid

A self-assembling fluorescence sensor with boronic acid functionalities was tested for binding selectivity to the monosaccharide, sialic acid. Working from a previously reported system, a self-assembling system could form an imine in situ that enables a conjugated fluorophore to display a measurable change in fluorescence in the presence of monosaccharide. However, further examination showed that free sugars give a similar fluorescence response to just the m-aminophenylboronic acid moiety on its own. Still, such a self-assembly method may be applicable to cell surface saccharide sensing as aldehydes and ketones are noticeably absent on most cells’ exteriors. The original covalent receptor appears best suited for the detection of free sialic acid.

Influence of beta-carotene on lysosomal hydrolases and their natural substrates in major salivary glands of hamsters treated with 7,12-dimethylbenzanthracene (DMBA)

We evaluated the effects of beta-carotene, a precursor of vitamin A, on the activity of some lysosomal hydrolases and on the levels of their natural substrates in hamster major salivary glands during experimental oral 7,12-dimethylbenzanthracene (DMBA) carcinogenesis. Sixty-four hamsters (Cricetus auratus) were divided into four groups--group 1: untreated control; group 2: DMBA was painted three times a week in the left buccal pouch; group 3: beta-carotene was painted three times a week in the left buccal pouch; group 4: DMBA and beta-carotene were painted alternatively in the left buccal pouch. After 16 weeks, the animals were sacrificed and the activities of some lysosomal hydrolases and their natural substrates in the major salivary glands were measured. beta-Carotene when administered topically in DMBA treated animals (group 4) reduced the levels of the majority of enzymes and substrates closer to those of the untreated control group, thus outlining a mild protective effect of beta-carotene towards the DMBA carcinogenic stress. Nevertheless, the presence of some enzymes which responded negatively to the combined administration of DMBA and beta-carotene suggests the necessity for future studies on the effect of beta-carotene at different concentrations, the systemic administration and the possibility to combine the topical beta-carotene administration with other chemopreventive drugs.

Lysosomal glycosidases and their natural substrates in major salivary glands of hamsters treated with 7,12-dimethylbenzanthracene (DMBA)

Oro-maxillofacial diseases may influence structure and function of salivary glands. In this study, 32 hamsters were treated with topical application of 7,12-dimethylbenzanthracene (DMBA) on the buccal pouch. After 16 weeks, the animals were killed and the major salivary glands extracted. The activities of some lysosomal glycosidases and their natural substrates were measured to understand how the carcinogenetic stress and the inflammatory reaction could influence the physiology of the salivary glands. Large differences were observed in lysosomal activities among treated and untreated animals. Similarly, large differences were shown in the concentration of natural substrates, including sialic acids. These results suggest that inflammation and/or tumors induce profound changes in the biology of the salivary glands.