Simultaneous detection of 5-fluorocytosine and 5-fluorouracil in human cells carrying CD/5-FC suicide gene system by using capillary zone electrophoresis

Recent advances of engineered oncolytic viruses-based combination therapy for liver cancer

Liver cancer is a major malignant tumor, which seriously threatens human health and increases the economic burden on patients. At present, gene therapy has been comprehensively studied as an excellent therapeutic measure in liver cancer treatment. Oncolytic virus (OV) is a kind of virus that can specifically infect and kill tumor cells. After being modified by genetic engineering, the specificity of OV infection to tumor cells is increased, and its influence on normal cells is reduced. To date, OV has shown its effectiveness and safety in experimental and clinical studies on a variety of tumors. Thus, this review primarily introduces the current status of different genetically engineered OVs used in gene therapy for liver cancer, focuses on the application of OVs and different target genes for current liver cancer therapy, and identifies the problems encountered in OVs-based combination therapy and the corresponding solutions, which will provide new insights into the treatment of liver cancer.

Development of a facile electrochemical sensor based on GCE modified with one-step prepared PNMA-CeO2-fMWCNTs composite for simultaneous detection of UA and 5-FU

In this study, a poly(N-methyl aniline)-cerium oxide-functionalized MWCNTs (PNMA-CeO2-fMWCNTs) composite was synthesized in a one-step preparation technique. As a highly efficient modifier, the composite was used to modify the glassy carbon electrode surface for simultaneous detection of uric acid (UA) and 5-fluorouracil (5-FU). Morphological characterization of the GCE/PNMA-CeO2-fMWCNTs was studied using scanning electron microscopy. Structural characterization of the composite was performed using X-ray diffraction and Fourier-transformed infrared spectroscopy. Electron transfer properties of the prepared electrodes were carried out with electrochemical impedance spectroscopy and cyclic voltammetry. The linear working range for UA and 5-FU was found to be 0.25-50 μM and 0.5-750 μM, respectively. The limit of detection values for UA and 5-FU were 0.04 μM and 0.19 μM, respectively. The effects of various interfering substances on the electrochemical response of UA and 5-FU were investigated. The GCE/PNMA-CeO2-fMWCNTs sensor has excellent stability, reproducibility, anti-interference ability, and reproducibility. To demonstrate the practical application of the sensing platform, fetal bovine serum was selected and tested in the spiked samples, and satisfactory results were obtained. The prepared composite proved to be a promising platform for simple, rapid, and simultaneous analysis of UA and 5-FU.

Enhancement of nanoparticle-mediated double suicide gene expression driven by 'E9-hTERT promoter' switch in dedifferentiated thyroid cancer cells

Differentiated thyroid cancer (DTC), such as papillary thyroid cancer, has a good prognosis after routine treatment. However, in the course of treatment, 5% to 20% of cases may dedifferentiate and can be transformed into dedifferentiated DTC (deDTC) or anaplastic thyroid cancer, leading to treatment failure. To date, several drugs have been used effectively for dedifferentiated thyroid cancer, whereas gene therapy may be a potential method. Literature reported that double suicide genes driven by human telomerase reverse transcriptase promoter (hTERTp) can specifically express in cancer cells and kill them. However, the weak activity of hTERTp limits its further research. To overcome this weakness, we constructed a novel chitosan nanocarrier containing double suicide genes driven by a ‘gene switch’ (a cascade of radiation enhancer E9 and a hTERTp). The vector was labeled with iodine-131 (¹³¹I). On one hand, E9 can significantly enhance the activity of hTERTp under the weak radiation of ¹³¹I, thereby increasing the expression of double suicide genes in deDTC cells. On the other hand, ¹³¹I also plays a certain killing role when it enters host cells. The proposed nanocarrier has good specificity for deDTC cells and thus deserves further study.

Development of LC-HRMS methods for evaluation of metabolic conversion of 5-fluorocytosine at GDEPT procedure

Gene-directed enzyme/prodrug therapy represents one of the experimental treatment approaches. The system based on conversion of nontoxic prodrug 5-fluorocytosine to chemotherapeutic 5-fluorouracil by cytosine deaminase or fusion cytosine deaminase::uracil phosphoribosyl transferase belongs to the most frequently used. The detailed analysis of 5-fluorocytosine, 5-fluorouracil and its metabolites enables to understand various responses of tumour cells to treatment as well as mechanisms of resistance. A fast, sensitive and accurate methods based on liquid chromatography with high-resolution mass spectrometry (LC-HRMS) for the identification and quantification of 5-fluorocytosine, 5-fluorouracil and its major metabolites were developed. Two different hybrid high-resolution mass spectrometers sufficient for study of metabolic pathways were used. The LC-ESI IT-TOF MS method was successfully used for identification of 5-fluorocytosine, 5-fluorouracil and its metabolites in complex biological matrices (mesenchymal stromal cells and tumour cells media) and for confirmation of the metabolic conversion of 5-fluorocytosine even in chemoresistant tumour cells media samples. For quantification, the LC-HESI QExactive MS method was developed and validated. The developed method demonstrated a very good linear range for 5-fluorocytosine from 1 ng/mL to 1000 ng/mL and for its major metabolites from 5 ng/mL to 1000 ng/mL. The limits of detection and limits of quantification ranged from 1.1 to 26 ng/mL and from 3.6 to 87 ng/mL, respectively. Both developed methods confirmed the ability of gene-directed enzyme prodrug therapy to metabolically convert 5-fluorocytosine to 5-fluorouracil and its major metabolites in real samples of tumour cell media and mesenchymal stromal cells.

Prodrugs and prodrug-activated systems in gene therapy

The inclusion of genes that control cell fate (so-called suicide, or kill-switch, genes) into gene therapy vectors is based on a compelling rationale for the safe and selective elimination of aberrant transfected cells. Prodrug-activated systems were developed in the 1980s and 1990s and rely on the enzymatic conversion of non-active prodrugs to active metabolites that lead to cell death. Although considerable effort and ingenuity has gone into vector design for gene therapy, less attention has been directed at the efficacy or associated adverse effects of the prodrug systems employed. In this review, we discuss prodrug systems employed in clinical trials and consider their role in the field of gene therapy. We highlight potential drawbacks associated with the use of specific prodrugs, such as systemic toxicity of the activated compound, the paucity of data on biodistribution of prodrugs, bystander effects, and destruction of genetically modified cells, and how these can inform future advances in cell therapies.

Determination of 5-fluorocytosine, 5-fluorouracil, and 5-fluorouridine in hospital wastewater by liquid chromatography-mass spectrometry

Chemotherapeutics are pharmaceutical compounds the occurrence of which in the environment is of growing concern because of the increase in treatments against cancer diseases. They can reach the aquatic ecosystems after passing through wastewater treatment plants without complete removal. One of the most frequently used chemotherapeutics is 5-fluorouracil which exhibits a strong cytostatic effect. In this paper, an analytical methodology was developed, validated, and applied to determine 5-fluorouracil, its precursor, 5-fluorocytosine, and its major active metabolite, 5-fluorouridine, in hospital wastewater samples. Due to the expected low concentrations after dilution and interferences present in such a complex matrix, a very selective and sensitive detection method is required. Moreover, an extraction method must be implemented prior to the determination in order to purify the sample extract and preconcentrate the target analytes at micrograms per liter concentration levels. Solid-phase extraction followed by liquid chromatography with tandem mass spectrometry was the combination of choice and all included parameters were studied. Under optimized conditions for wastewater samples analysis, recoveries from 63 to 108% were obtained, while intraday and interday relative standard deviations never exceeded 20 and 25%, respectively. Limits of detection between 61 and 620 ng/L were achieved. Finally, the optimized method was applied to samples from hospital wastewater effluents.