A Color Indicator Based on 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide (MTT) and a Biodegradable Poly(ester amide) for Detecting Bacterial Contamination.

Bacterial contamination is a hazard in many industries, including food, pharmaceuticals, and healthcare. The availability of a rapid and simple method for detecting this type of contamination in sterile areas enables immediate intervention to avoid or reduce detrimental effects. Among these methods, colorimetric indicators are becoming increasingly popular due to their affordability, ease of use, and quick visual interpretation of the signal. In this article, a bacterial contamination indicator system was designed by incorporating MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) into an electrospun PADAS matrix, which is a biodegradable poly(ester amide) synthesized from L-alanine, 1,12-dodecanediol, and sebacic acid. Uniaxial stress testing, thermogravimetric analysis and scanning electron microscopy were used to examine the mechanical properties, thermal stability, and morphology of the mats, respectively. The capacity for bacterial detection was not only analyzed with agar and broth assays but also by replicating important environmental conditions. Among the MTT concentrations tested in this study (0.2%, 2%, and 5%), it was found that only with a 2% MTT content the designed system produced a color response visible to the naked eye with optimal intensity, a sensitivity limit of 104 CFU/mL, and 86% cell viability, which showed the great potential for its use to detect bacterial contamination. In summary, by means of the process described in this work, it was possible to obtain a simple, low-cost and fast-response bacterial contamination indicator that can be used in mask filters, air filters, or protective clothing.

Accelerated Method for Determining Ischemic Brain Damage in Rats and Assessment the Neuroprotective Effect of a Complex Herbal Remedy.

The severity of ischemic injury was evaluated by densitometry of brain samples stained with 2,3,5-triphenyltetrazolium chloride (TTC) on a rat model of cerebral ischemia/reperfusion (common carotid artery occlusion) and the neuroprotective activity of an extract of Astragalus membranaceus, Scutellaria baicalensis, and Phlojodicarpus sibiricus was assessed. Occlusion of the common carotid arteries led to a weakening of TTC staining of the brain tissue: densitometric indicators of the staining intensity for the cortex and striatum were lower than the corresponding indicators of sham-operated rats by 18.3 and 10.4%. The mean intensity of staining of brain samples did not differ in rats treated with the extract and sham-operated animals, which attested to its neuroprotective effect. The applied method is convenient for evaluation of the severity of ischemic brain damage at the early stages and screening potential neuroprotective agents.

Discovery of orally bioavailable phenyltetrazolium derivatives for the acute treatment and the secondary prevention of ischemic stroke.

The potential for secondary stroke prevention, which can significantly reduce the risk of recurrent strokes by almost 90%, underscores its critical importance. N-butylphthalide (NBP) has emerged as a promising treatment for acute cerebral ischemia, yet its efficacy for secondary stroke prevention is hindered by inadequate pharmacokinetic properties. This study, driven by a comprehensive structural analysis, the iterative process of structure optimization culminated in the identification of compound B4, which demonstrated exceptional neuroprotective efficacy and remarkable oral exposure and oral bioavailability. Notably, in an in vivo transient middle cerebral artery occlusion (tMCAO) model, B4 substantially attenuated infarct volumes, surpassing the effectiveness of NBP. While oral treatment with B4 exhibited stronger prevention potency than NBP in photothrombotic (PT) model. In summary, compound B4, with its impressive oral bioavailability and potent neuroprotective effects, offers promise for both acute ischemic stroke treatment and secondary stroke prevention.

Single-Cell MTT: A Simple and Sensitive Assay for Determining the Viability and Metabolic Activity of Polyploid Giant Cancer Cells (PGCCs).

Solid tumors and tumor-derived cell lines commonly contain highly enlarged (giant) cancer cells that enter a state of transient dormancy (active sleep) after they are formed, but retain viability, secrete growth promoting factors, and exhibit the ability to generate rapidly proliferating progeny with stem cell-like properties. Giant cells with a highly enlarged nucleus or multiple nuclei are often called polyploid giant cancer cells (PGCCs). Although PGCCs constitute only a subset of cells within a solid tumor/tumor-derived cell line, their frequency can increase markedly following exposure to ionizing radiation or chemotherapeutic drugs. In this chapter we outline a simple and yet highly sensitive cell-based assay, called single-cell MTT, that we have optimized for determining the viability and metabolic activity of PGCCs before and after exposure to anticancer agents. The assay measures the ability of individual PGCCs to convert the MTT tetrazolium salt to its water insoluble formazan metabolite. In addition to evaluating PGCCs, this assay is also a powerful tool for determining the viability and metabolic activity of cancer cells undergoing premature senescence following treatment with anticancer agents, as well as for distinguishing dead cancer cells and dying cells (e.g., exhibiting features of apoptosis, ferroptosis, etc.) that have the potential to resume proliferation through a process called anastasis.

XTT assay for detection of bacterial metabolic activity in water-based polyester polyurethane.

Cellular metabolic activity can be detected by tetrazolium-based colorimetric assays, which rely on dehydrogenase enzymes from living cells to reduce tetrazolium compounds into colored formazan products. Although these methods have been used in different fields of microbiology, their application to the detection of bacteria with plastic-degrading activity has not been well documented. Here, we report a microplate-adapted method for the detection of bacteria metabolically active on the commercial polyester polyurethane (PU) Impranil®DLN using the tetrazolium salt 2,3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT). Bacterial cells that are active on PU reduce XTT to a water-soluble orange dye, which can be quantitatively measured using a microplate reader. We used the Pseudomonas putida KT2440 strain as a study model. Its metabolic activity on Impranil detected by our novel method was further verified by Fourier-transform infrared spectroscopy (FTIR) analyses. Measurements of the absorbance of reduced XTT at 470 nm in microplate wells were not affected by the colloidal properties of Impranil or cell density. In summary, we provide here an easy and high-throughput method for screening bacteria active on PU that can be adapted to other plastic substrates.

Development of a Convenient and Quantitative Method for Evaluating Photosensitizing Activity Using Thiazolyl Blue Formazan Dye.

Photosensitizers cause oxidative damages in various biological systems under light. In this study, the method for analyzing photosensitizing activity of various dietary and medicinal sources was developed using 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan (thiazolyl blue formazan; MTT-F) as a probe. Significant and quantitative decolorization of MTT-F was observed in the presence of photosensitizers used in this study under light but not under dark conditions. The decolorization of MTT-F occurred irradiation time-, light intensity-, and photosensitizer concentration-dependently. The decolorized MTT-F was reversibly reduced by living cells; the LC-MS/MS results indicated the formation of oxidized products with -1 m/z of base peak from MTT-F, suggesting that MTT-F decolorized by photosensitizers was its corresponding tetrazolium. The present results indicate that MTT-F is a reliable probe for the quantitative analysis of photosensitizing activities, and the MTT-F-based method can be an useful tool for screening and evaluating photosensitizing properties of various compounds used in many industrial purposes.

Evaluation of Antibiotic Penicillin G Activities Based on Electrochemical Measurement of a Tetrazolium Salt.

This study focused on the electrochemical properties of tetrazolium salts to develop a simple method for evaluating viable bacterial counts, which are indicators of drug susceptibility. Considering that the oxidized form of tetrazolium, which has excellent cell membrane permeability, changes to the insoluble reduced form formazan inside the cell, the number of viable cells was estimated based on the reduction current of the tetrazolium remaining in the bacterial suspension. Dissolved oxygen is an important component of bacterial activity. However, it interferes with the electrochemical response of tetrazolium. We estimated the number of viable bacteria in the suspension based on potential-selective current responses that were not affected by dissolved oxygen. Based on solubility, cell membrane permeability, and characteristic electrochemical properties of the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium, we developed a method for rapidly measuring viable bacteria within one-fifth of the time required by conventional colorimetric methods for drug susceptibility testing.

Viability and Proliferation Assessment of Gingival Fibroblasts Cultured on Silver Nanoparticle-Doped Ti-6Al-4V Surfaces.

PURPOSE: To investigate the biocompatibility of silver nanoparticle (AgNP)-doped Ti-6Al-4V surfaces by evaluating the viability and proliferation rate of human gingival fibroblasts (HGFs)-as the dominant cells of peri-implant soft tissues-seeded on the modified surfaces. MATERIALS AND METHODS: AgNPs (sizes 8 nm and 30 nm) were incorporated onto Ti-6Al-4V specimen surfaces via electrochemical deposition, using colloid silver dispersions with increasing AgNP concentrations of 100 ppm, 200 ppm, and 300 ppm. One control and six experimental groups were included in the study: (1) control (Ti-6Al-4V), (2) 8 nm/100 ppm, (3) 8 nm/200 ppm, (4) 8 nm/300 ppm, (5) 30 nm/100 ppm, (6) 30 nm/200 ppm, and (7) 30 nm/300 ppm. HGF cell primary cultures were isolated from periodontally healthy donor patients and cultured in direct contact with the group specimens for 24 and 72 hours. The cytotoxicity of AgNP-doped Ti-6Al-4V specimens toward HGF was assessed by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) and BrdU (5-bromo-2'-deoxyuridine) assay tests. Calcein AM and ethidium homodimer (EthD-1) fluorescent stains were used to determine the live and dead cells. The morphology and attachment properties of the HGFs were determined via scanning electron microscopy (SEM). RESULTS: Energy dispersive x-ray (EDX) analysis confirmed the presence of AgNPs on the specimens. The MTT test revealed that AgNPs of both sizes and all concentrations presented a decreased cellular metabolic activity compared to the control discs. All concentrations of both sizes of AgNPs affected the cell proliferation rate compared to the control group, as revealed by the BrdU assay. Overall, cytotoxicity of the modified Ti-6Al-4V surfaces depended on cell exposure time. Observation via confocal microscopy confirmed the results of the MTT and BrdU assay tests. Specifically, most cells remained alive throughout the 72-hour culture period. SEM images revealed that adjacent cells form bonds with each other, creating confluent layers of conjugated cells. CONCLUSIONS: The findings of the present study indicate that Ti-6Al-4V surfaces modified with 8 nm and 30 nm AgNPs at concentrations of 100 ppm, 200 ppm, and 300 ppm do not produce any serious cytotoxicity toward HGFs. The initial arrest of the HGF proliferation rate recovered at 72 hours. These results on the antibacterial activity against common periodontal pathogens, in combination with the results found in a previous study by the same research group, suggest that AgNP-doped Ti-6Al-4V surfaces are potential candidates for use in implant abutments for preventing peri-implant diseases.

Re-evaluation and modification of dehydrogenase activity tests in assessing microbial activity for wastewater treatment plant operation.

Reliable and cost-effective methods for monitoring microbial activity are critical for process control in wastewater treatment plants. The dehydrogenase activity (DHA) test has been recognized as an efficient measure of biological activity due to its simplicity and broad applicability. Nevertheless, the existing DHA test methods suffer from imperfections and are difficult to implement as routine monitoring techniques. In this work, an accurate and cost-effective modified DHA approach was developed and the procedure for the DHA test was critically evaluated with respect to the standard construction, sample pretreatment, incubation and extraction conditions. The feasibility of the modified DHA test was demonstrated by comparison with the oxygen uptake rate and adenosine triphosphate in a sequencing batch reactor. The sensitivities of the two typical tetrazolium salts to toxicant inhibition by heavy metals and antibiotics were compared, revealing that 2,3,5-triphenyltetrazolium chloride (TTC) exhibited a higher sensitivity. Furthermore, the sensitivity mechanism of the two DHA tests was elucidated through electrochemical experiments, theoretical analysis and molecular simulations. Both tetrazolium salts were found to be effective artificial electron acceptors due to their low redox potentials. Molecular docking simulations revealed that TTC could outperform other tetrazolium salts in accepting electrons and hydrogens from dehydrogenase. Overall, the modified DHA approach presents an accurate and cost-effective way to measure microbial activity, making it a practical tool for wastewater treatment plants.

An improved MTT colorimetric method for rapid viable bacteria counting.

The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay has been employed in the analysis of bacterial growth. In comparison to experiments conducted on mammalian cells, the MTT bacterial assay encounters a greater number of interfering factors and obstacles that impact the accuracy of results. In this study, we have elucidated an improved MTT assay protocol and put forth an equation that establishes a correlation between colony-forming units (CFU) and the amount of formazan converted by the bacteria, drawing upon the fundamental principle of the MTT assay. This equation is represented as CFU=kF. Furthermore, we have explicated a methodology to determine the scale factor "k" by employing S. aureus and E. coli as illustrative examples. The findings indicate that S. aureus and E. coli reduce MTT by a cyclic process, from which the optimal reduction time at room temperature was determined to be approximately 30 mins. Furthermore, individual E. coli exhibits an MTT reduction capacity approximately four times greater than that of S. aureus. HPLC analysis proves to be the most accurate method for mitigating interferences during the dissolution and quantification of formazan. Additionally, this study has identified a new constraint related to the narrow linear range (0-125 µg/mL) of formazan concentration-absorbance and has presented strategies to circumvent this limitation.

A Study of the Bisphosphonic Derivatives from the Pudovik Reaction of Dialkyl α-Oxophosphonates and >P(O)H Reagents: X-ray Structure and Bioactivity.

New hydroxy-methylenebisphosphonic derivatives were prepared with different P-functions. The outcome of the reaction of α-oxophosphonates (YC(O)P(O)(OR)2) and dialkyl phosphites or diarylphosphine oxides depended on the Y substituent of the oxo-compound, the nature of the P-reagent and the amount of the diethylamine catalyst. Starting from dimethyl α-oxoethylphosphonate, in the presence of 5% of diethylamine, the corresponding Pudovik adduct was the single product. While using 40% of the catalyst, the rearranged species with the >P(O)-O-CH-P(O)< skeleton was the exclusive component. A similar reaction of α-oxobenzylphosphonate followed the rearrangement protocol. X-ray crystallography revealed not only the spatial structures of the three products, but also an intricate pattern evolving from the interplay of slight chemical differences, solvent inclusion and disorder as well as H-bridge patterns, which invite further investigation. In vitro activity of the compounds was assessed on different tumor cell cultures using end-point-type cell tetrazolium-based measurements. These structure-activity studies revealed a cytostatic effect for four rearranged derivatives containing aromatic units. One of them had a pronounced effect on MDA-MB 231 and Ebc-1 cells, showing IC50 = 37.8 and 25.9 µM, respectively.

Assessment of clustering techniques to support the analyses of soybean seed vigor.

Soy is the main product of Brazilian agriculture and the fourth most cultivated bean globally. Since soy cultivation tends to increase and due to this large market, the guarantee of product quality is an indispensable factor for enterprises to stay competitive. Industries perform vigor tests to acquire information and evaluate the quality of soy planting. The tetrazolium test, for example, provides information about moisture damage, bedbugs, or mechanical damage. However, the verification of the damage reason and its severity are done by an analyst, one by one. Since this is massive and exhausting work, it is susceptible to mistakes. Proposals involving different supervised learning approaches, including active learning strategies, have already been used, and have brought significant results. Therefore, this paper analyzes the performance of non-supervised techniques for classifying soybeans. An extensive experimental evaluation was performed, considering (9) different clustering algorithms (partitional, hierarchical, and density-based) applied to 5 image datasets of soybean seeds submitted to the tetrazolium test, including different damages and/or their levels. To describe those images, we considered 18 extractors of traditional features. We also considered four metrics (accuracy, FOWLKES, DAVIES, and CALINSKI) and two-dimensionality reduction techniques (principal component analysis and t-distributed stochastic neighbor embedding) for validation. Results show that this paper presents essential contributions since it makes it possible to identify descriptors and clustering algorithms that shall be used as preprocessing in other learning processes, accelerating and improving the classification process of key agricultural problems.

Evaluation of Bacterial Activity Based on the Electrochemical Properties of Tetrazolium Salts.

This study focused on the electrochemical properties of tetrazolium salts to develop a simple method for evaluating viable bacterial counts, which are indicators of hygiene control at food and pharmaceutical manufacturing sites. Given that the oxidized form of 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), which has excellent cell membrane permeability, changes to the insoluble reduced form of formazan inside the cell, the number of viable cells was estimated by focusing on the reduction current of MTT remaining in the suspension. Dissolved oxygen is an important substance for bacterial activity; however, it interferes with the electrochemical response of MTT. We investigated the electrochemical properties of MTT to obtain a potential-selective current response that was not affected by dissolved oxygen. Real-time observation of viable bacteria in suspension revealed that uptake of MTT into bacteria was completed within 10 min, including the lag period. In addition, we observed that the current response depends on viable cell density regardless of the bacterial species present. Our method enables a rapid estimation of the number of viable bacteria, making it possible to confirm the safety of food products before they are shipped from the factory and thereby prevent food poisoning.

Coordination Compound (2,3,5-Triphenyltetrazolium)2[CuBr4] as Catalyst for the Curing Process of Epoxy Vinyl Ester Binders.

This article presents a study on the synthesis and catalytic properties of copper complex (TPhTz)2[CuBr4] (here TPhTz is 2,3,5-triphenyltetrazolium). The obtained complex was characterized by various spectroscopic methods. The catalytic properties of the complex were evaluated in the curing of an epoxy vinyl ester system and their effectiveness was compared with that of cobalt octoate (its synonyms are known as Co(Oct)2, cobalt(II) 2-ethylhexanoate, cobalt isocaprylate, etc.). The catalyst was added at an amount of 2 w.%. The results showed that a 8 w.% solution of the complex provides catalytic properties with an activation energy of 54.7 kJ/mol, which is 25.2 kJ/mol higher than a standard curing system with Co(Oct)2. Thus, the solution of (TPhTz)2[CuBr4] in THF/DMSO accelerates the initiator decay process at room temperature, but for a longer time. The authors suggest that the curing mechanism may be accelerated by the appearance of (TPhTz)2[CuIBr3] and free bromine in the system. A strength test of fiberglass-reinforced plastic revealed that the addition of this complex did not lead to a decrease in flexural strength and hardness. Thus, use of the complex allowed for the production of polymer composite products using vacuum-assisted resin transfer molding where an extended injection time was needed.

Design of Tetrazolium Cations for the Release of Antiproliferative Formazan Chelators in Mammalian Cells.

Cancer cells generally present a higher demand for iron, which plays crucial roles in tumor progression and metastasis. This iron addiction provides opportunities to develop broad spectrum anticancer drugs that target iron metabolism. In this context, prochelation approaches are investigated to release metal-binding compounds under specific conditions, thereby limiting off-target toxicity. Here, we demonstrate a prochelation strategy inspired by the bioreduction of tetrazolium cations widely employed to assess the viability of mammalian cells. We designed a series of tetrazolium-based compounds for the intracellular release of metal-binding formazan ligands. The combination of reduction potentials appropriate for intracellular reduction and an N-pyridyl donor on the formazan scaffold led to two effective prochelators. The reduced formazans bind as tridentate ligands and stabilize low-spin Fe(II) centers in complexes of 2:1 ligand-to-metal stoichiometry. The tetrazolium salts are stable in blood serum for over 24 h, and antiproliferative activities at micromolar levels were recorded in a panel of cancer cell lines. Additional assays confirmed the intracellular activation of the prochelators and their ability to affect cell cycle progression, induce apoptotic death, and interfere with iron availability. Demonstrating the role of iron in their intracellular effects, the prochelators impacted the expression levels of key iron regulators (i.e., transferrin receptor 1 and ferritin), and iron supplementation mitigated their cytotoxicity. Overall, this work introduces the tetrazolium core as a platform to build prochelators that can be tuned for activation in the reducing environment of cancer cells and produce antiproliferative formazan chelators that interfere with cellular iron homeostasis.

The MTT Assay: A Method for Error Minimization and Interpretation in Measuring Cytotoxicity and Estimating Cell Viability.

The MTT assay is extensively used, most often to infer a measure of cytotoxicity of treatments to cells. As with any assay though, there are a number of limitations. The method described here is designed with consideration of how the MTT assay fundamentally works to account for, or at least identify, confounding factors in measurements. It also provides a decision-making framework to best interpret and complement the MTT assay to apply it as either a measure of metabolic activity or cell viability.

In vitro cytocompatibility and antibacterial studies on biodegradable Zn alloys supplemented by a critical assessment of direct contact cytotoxicity assay.

In vitro cytotoxicity assessment is indispensable in developing new biodegradable implant materials. Zn, which demonstrates an ideal corrosion rate between Mg- and Fe-based alloys, has been reported to have excellent in vivo biocompatibility. Therefore, modifications aimed at improving Zn's mechanical properties should not degrade its biological response. As sufficient strength, ductility and corrosion behavior required of load-bearing implants has been obtained in plastically deformed Zn-3Ag-0.5Mg, the effect of simultaneous Ag and Mg additions on in vitro cytocompatibility and antibacterial properties was studied, in relation to Zn and Zn-3Ag. Direct cell culture on samples and indirect extract-based tests showed almost no significant differences between the tested Zn-based materials. The diluted extracts of Zn, Zn-3Ag, and Zn-3Ag-0.5Mg showed no cytotoxicity toward MG-63 cells at a concentration of ≤12.5%. The cytotoxic effect was observed only at high Zn2+ ion concentrations and when in direct contact with metallic samples. The highest LD50 (lethal dose killing 50% of cells) of 13.4 mg/L of Zn2+ ions were determined for the Zn-3Ag-0.5Mg. Similar antibacterial activity against Escherichia coli and Staphylococcus aureus was observed for Zn and Zn alloys, so the effect is attributed mainly to the released Zn2+ ions exhibiting bactericidal properties. Most importantly, our experiments indicated the limitations of water-soluble tetrazolium salt-based cytotoxicity assays for direct tests on Zn-based materials. The discrepancies between the WST-8 assay and SEM observations are attributed to the interference of Zn2+ ions with tetrazolium salt, therefore favoring its transformation into formazan, giving false cell viability quantitative results.

Immobilisation of Neuro-2a cells on electrodes and electrochemical detection of MTT formazan crystals to assess their viability.

Marine toxins are potent toxic compounds that may reach humans and poison them. Therefore, their detection in seafood is crucial to prevent intoxication cases. Colorimetric cell-based assays (CBAs) have been developed to analyse marine neurotoxins, such as ciguatoxins (CTXs) and tetrodotoxins (TTXs), and are based on the toxicological effect of these toxins on the cells. Cell viability can be quantified by measuring the mitochondrial activity with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). With the purpose of moving forward in the development of cell-based biosensors (CBBs) for neurotoxins, Neuro-2a cells were immobilised on electrodes of different materials (carbon, carbon/polyaniline, carbon/poly-l-lysine, carbon/poly(3,4-ethylenedioxythiophene) and gold) and their presence and viability were assessed by the detection of MTT formazan crystals with cyclic voltammetry (CV). Best results in terms of oxidation potential and current intensity were achieved with carbon and carbon/polyaniline electrodes. Light microscopy also proved the presence of immobilised and living cells on electrodes. Cell density, incubation time and MTT concentration were optimised. Appropriate electrochemical responses were obtained incubating 100,000 cells/electrode for 2 h and using 0.86 mg/mL MTT. The system was able to detect toxicity when exposed to CTX1B and TTX standard solutions as well as Seriola dumerili and Lagocephalus sceleratus fish extracts containing these toxins.

Loss of Heterozygosity of BRCA1/2 as a Predictive Marker for Talazoparib Response.

BACKGROUND/AIM: Tumor cell lines are essential tools in understanding the molecular mechanisms underlying cancer biology and therapeutic responses. Poly (ADP-ribose) polymerase inhibitors (PARPi) kill tumor cells harboring pathogenic mutations of BRCA DNA repair-associated genes 1/2 (BRCA1/2) and are approved to treat ovarian and metastatic breast cancer. Loss of heterozygosity (LOH) of the wild-type BRCA1/2 locus is suspected to increase cellular response to PARPi. To better elucidate the molecular mechanisms underlying PARPi sensitivity and resistance, this study assessed the responses of various pathogenic BRCA1/2-mutant cell lines to the PARPi talazoparib. MATERIALS AND METHODS: Mutant cell lines were extracted and cultured from four surgically resected, human breast cancer specimens with different pathogenic BRCA1/2, one normal breast specimen and one ovarian cancer specimen. Mutation analysis was performed on all cell lines using genomic DNA extraction and polymerase chain reaction. Following treatment with talazoparib, cell growth was assessed using tetrazolium salt and half-maximal inhibitory concentration values were determined. RESULTS: A partial correlation between different variants of pathogenic BRCA1/2 mutation and talazoparib susceptibility was found, with five of the cell lines exhibiting sensitivity to talazoparib. The most sensitive cell-line to talazoparib had LOH for BRCA1, while the breast cancer cell line harboring BRCA2 LOH was resistant to talazoparib. CONCLUSION: This study suggests that LOH does not necessarily correlate with PARPi efficacy. These results lay a foundation for future studies to utilize these novel cell lines to further elucidate the underlying molecular mechanisms of PARPi resistance and reveal new potential drug targets.

Epigallocatechin-3-gallate suppresses hemin-aggravated colon carcinogenesis through Nrf2-inhibited mitochondrial reactive oxygen species accumulation.

BACKGROUND: Previous studies have presented evidence to support the significant association between red meat intake and colon cancer, suggesting that heme iron plays a key role in colon carcinogenesis. Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, exhibits anti-oxidative and anti-cancer effects. However, the effect of EGCG on red meat-associated colon carcinogenesis is not well understood. OBJECTIVES: We aimed to investigate the regulatory effects of hemin and EGCG on colon carcinogenesis and the underlying mechanism of action. METHODS: Hemin and EGCG were treated in Caco2 cells to perform the water-soluble tetrazolium salt-1 assay, lactate dehydrogenase release assay, reactive oxygen species (ROS) detection assay, real-time quantitative polymerase chain reaction and western blot. We investigated the regulatory effects of hemin and EGCG on an azoxymethane (AOM) and dextran sodium sulfate (DSS)-induced colon carcinogenesis mouse model. RESULTS: In Caco2 cells, hemin increased cell proliferation and the expression of cell cycle regulatory proteins, and ROS levels. EGCG suppressed hemin-induced cell proliferation and cell cycle regulatory protein expression as well as mitochondrial ROS accumulation. Hemin increased nuclear factor erythroid-2-related factor 2 (Nrf2) expression, but decreased Keap1 expression. EGCG enhanced hemin-induced Nrf2 and antioxidant gene expression. Nrf2 inhibitor reversed EGCG reduced cell proliferation and cell cycle regulatory protein expression. In AOM/DSS mice, hemin treatment induced hyperplastic changes in colon tissues, inhibited by EGCG supplementation. EGCG reduced the hemin-induced numbers of total aberrant crypts and malondialdehyde concentration in the AOM/DSS model. CONCLUSIONS: We demonstrated that EGCG reduced hemin-induced proliferation and colon carcinogenesis through Nrf2-inhibited mitochondrial ROS accumulation.