From viability to cell death: Claims with insufficient evidence in high-impact cell culture studies

Assessment of Cell Viability in Drug Therapy: IC50 and Other New Time-Independent Indices for Evaluating Chemotherapy Efficacy

Background/Objectives: Cell viability assays play a crucial role in cancer research and the development of effective treatments. Evaluating the efficacy of conventional treatments across different tumor profiles is essential for understanding patient resistance to chemotherapy and relapse. The IC50 index has been commonly used as a guide in these assays. The idea behind the IC50 index is to compare cell proliferation under treatment with respect to a control population exposed to the same treatment. The index requires normalization to a control and is time dependent. These aspects are disadvantages, as small variations yield different results. In this article, we propose a new method to analyze cell viability assays. Methods: This method involves calculating the effective growth rate for both control (untreated) cells and cells exposed to a range of drug doses for short times, during which exponential proliferation can be assumed. The concentration dependence of the effective growth rate gives a real estimate of the treatment on cell proliferation. A curve fit of the effective growth rate related to concentration yields the concentration corresponding to a given effective growth rate. Results: We use this estimation to calculate the IC50 index and introduce two new parameters (ICr0 and ICrmed) to compare treatment efficacy under different culture conditions or cell lines. Conclusions: In summary, this study presents a new method to analyze cell viability assays and introduces two more precise parameters, improving the comparison and evaluation of efficacy under different conditions.

High molecular weight polycyclic aromatic hydrocarbon (HMW-PAH) isomers: unveiling distinct toxic effects from cytotoxicity to oxidative stress-induced DNA damage

Polycyclic aromatic hydrocarbons (PAHs) represent one of the most extensive classes of known carcinogenic and genotoxic compounds widely distributed across the globe. Particularly relevant to ecotoxicological studies is the possible presence of PAHs with molecular weight (MW) 302 Da. Since the toxicity of 302 Da PAHs differs significantly from isomer to isomer, understanding their relative toxicity is essential for assessing their potential risks to human health. This study investigates the toxic effects of micromolar concentrations of four HMW-PAHs isomers of MW = 302 Da, namely dibenzo(b,l)fluoranthene (DB(b,l)F), dibenzo(a,j)fluoranthene (DB(a,j)F), dibenzo(a,l)fluoranthene (DB(a,l)F) and naphtho(1-2j)fluoranthene (N(1-2j)F), upon exposure and metabolic activation in HepG2 cells. Appropriate assays were selected to investigate their potential to disrupt cellular viability and to induce cytotoxicity, apoptosis/necrosis, genotoxicity, and oxidative stress with DNA damage. After 48 h of exposure time, DB(a,l)F was the only isomer to reduce cellular viability in a concentration-dependent manner. In all cases, apoptosis was the main mechanism of HepG2 cell death, which could be induced by the significant DNA damage and an increase in 8-hydroxy-2'-deoxyguanosine (8-OHdG) adduct level formation. The highest concentrations of DB(a,l)F tested exhibited the greatest potential to induce HepG2 DNA damage and 8-OHdG formation. Altogether, these facts demonstrate that the distinct arrangements of the atoms in HMW-PAHs isomers can impact on their toxic potential and that DB(a,l)F was the most toxic isomer evaluated in this study. These results shed light on the importance to thoroughly characterize MW302 PAHs to substantiate their human and environmental risk assessments.

Experimental and computational approach to establish fit-for-purpose cell viability assays

Aim: Cell viability assays are critical for cell-based products. Here, we demonstrate a combined experimental and computational approach to identify fit-for-purpose cell assays that can predict changes in cell proliferation, a critical biological response in cell expansion. Materials & methods: Jurkat cells were systematically injured using heat (45 ± 1°C). Cell viability was measured at 0 h and 24 h after treatment using assays for membrane integrity, metabolic function and apoptosis. Proliferation kinetics for longer term cultures were modeled using the Gompertz distribution to establish predictive models between cell viability results and proliferation. Results & conclusion: We demonstrate an approach for ranking these assays as predictors of cell proliferation and for setting cell viability specifications when a particular proliferation response is required.

Breast Cancer Tissue Explants: An Approach to Develop Personalized Therapy in Public Health Services

Breast cancer is one of the main causes of death worldwide. Lately, there is great interest in developing methods that assess individual sensitivity and/or resistance of tumors to antineoplastics to provide personalized therapy for patients. In this study we used organotypic culture of human breast tumor slices to predict the experimental effect of antineoplastics on the viability of tumoral tissue. Samples of breast tumor were taken from 27 patients with clinically advanced breast cancer; slices were obtained and incubated separately for 48 h with paclitaxel, docetaxel, epirubicin, 5-fluorouracil, cyclophosphamide, and cell culture media (control). We determined an experimental tumor sensitivity/resistance (S/R) profile by evaluating tissue viability using the Alamar Blue® metabolic test, and by structural viability (histopathological analyses, necrosis, and inflammation). These parameters were related to immunohistochemical expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. The predominant histological type found was infiltrating ductal carcinoma (85.2%), followed by lobular carcinoma (7.4%) and mixed carcinoma (7.4%). Experimental drug resistance was related to positive hormone receptor status in 83% of samples treated with cyclophosphamide (p = 0.027). Results suggest that the tumor S/R profile can help to predict personalized therapy or optimize chemotherapeutic treatments in breast cancer.

Nanomaterial genotoxicity evaluation using the high-throughput p53-binding protein 1 (53BP1) assay

Toxicity evaluation of engineered nanomaterials is challenging due to the ever increasing number of materials and because nanomaterials (NMs) frequently interfere with commonly used assays. Hence, there is a need for robust, high-throughput assays with which to assess their hazard potential. The present study aimed at evaluating the applicability of a genotoxicity assay based on the immunostaining and foci counting of the DNA repair protein 53BP1 (p53-binding protein 1), in a high-throughput format, for NM genotoxicity assessment. For benchmarking purposes, we first applied the assay to a set of eight known genotoxic agents, as well as X-ray irradiation (1 Gy). Then, a panel of NMs and nanobiomaterials (NBMs) was evaluated with respect to their impact on cell viability and genotoxicity, and to their potential to induce reactive oxygen species (ROS) production. The genotoxicity recorded using the 53BP1 assay was confirmed using the micronucleus assay, also scored via automated (high-throughput) microscopy. The 53BP1 assay successfully identified genotoxic compounds on the HCT116 human intestinal cell line. None of the tested NMs showed any genotoxicity using the 53BP1 assay, except the positive control consisting in (CoO)(NiO) NMs, while only TiO2 NMs showed positive outcome in the micronucleus assay. Only Fe3O4 NMs caused significant elevation of ROS, not correlated to DNA damage. Therefore, owing to its adequate predictivity of the genotoxicity of most of the tested benchmark substance and its ease of implementation in a high throughput format, the 53BP1 assay could be proposed as a complementary high-throughput screening genotoxicity assay, in the context of the development of New Approach Methodologies.

The Use of Small-Molecule Compounds for Cell Adhesion and Migration in Regenerative Medicine

Cell adhesion is essential for cell survival, communication, and regulation, and it is of fundamental importance in the development and maintenance of tissues. Cell adhesion has been widely explored due to its many important roles in the fields of tissue regenerative engineering and cell biology. This is because the mechanical interactions between a cell and its extracellular matrix (ECM) can influence and control cell behavior and function. Currently, biomaterials for regenerative medicine have been heavily investigated as substrates for promoting a cells' adhesive properties and subsequent proliferation, tissue differentiation, and maturation. Specifically, the manipulation of biomaterial surfaces using ECM coatings such as fibronectin extracted from animal-derived ECM have contributed significantly to tissue regenerative engineering as well as basic cell biology research. Additionally, synthetic and natural bioadhesive agents with pronounced abilities to enhance adhesion in numerous biological components and molecules have also been assessed in the field of tissue regeneration. Research into the use of facilitative bioadhesives has aimed to further optimize the biocompatibility, biodegradability, toxicity levels, and crosslinking duration of bioadhesive materials for improved targeted delivery and tissue repair. However, the restrictive drawbacks of some of these bioadhesive and animal-derived materials include the potential risk of disease transmission, immunogenicity, poor reproducibility, impurities, and instability. Therefore, it is necessary for alternative strategies to be sought out to improve the quality of cell adhesion to biomaterials. One promising strategy involves the use of cell-adhesive small molecules. Small molecules are relatively inexpensive, stable, and low-molecular-weight (<1000 Da) compounds with great potential to serve as efficient alternatives to conventional bioadhesives, ECM proteins, and other derived peptides. Over the past few years, a number of cell adhesive small molecules with the potential for tissue regeneration have been reported. In this review, we discuss the current progress using cell adhesive small molecules to regulate tissue regeneration.

Functionalised Hybrid Collagen-Elastin for Acellular Cutaneous Substitute Applications

Wound contracture, which commonly happens after wound healing, may lead to physical distortion, including skin constriction. Therefore, the combination of collagen and elastin as the most abundant extracellular matrix (ECM) skin matrices may provide the best candidate biomaterials for cutaneous wound injury. This study aimed to develop a hybrid scaffold containing green natural resources (ovine tendon collagen type-I and poultry-based elastin) for skin tissue engineering. Briefly, freeze-drying was used to create the hybrid scaffolds, which were then crosslinked with 0.1% (w/v) genipin (GNP). Next, the physical characteristics (pore size, porosity, swelling ratio, biodegradability and mechanical strength) of the microstructure were assessed. Energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectrophotometry were used for the chemical analysis. The findings showed a uniform and interconnected porous structure with acceptable porosity (>60%) and high-water uptake capacity (>1200%), with pore sizes ranging between 127 ± 22 and 245 ± 35 µm. The biodegradation rate of the fabricated scaffold containing 5% elastin was lower (<0.043 mg/h) compared to the control scaffold (collagen only; 0.085 mg/h). Further analysis with EDX identified the main elements of the scaffold: it contained carbon (C) 59.06 ± 1.36-70.66 ± 2.89%, nitrogen (N) 6.02 ± 0.20-7.09 ± 0.69% and oxygen (O) 23.79 ± 0.65-32.93 ± 0.98%. FTIR analysis revealed that collagen and elastin remained in the scaffold and exhibited similar functional amides (amide A: 3316 cm^-1, amide B: 2932 cm^-1, amide I: 1649 cm^-1, amide II: 1549 cm^-1 and amide III: 1233 cm^-1). The combination of elastin and collagen also produced a positive effect via increased Young's modulus values. No toxic effect was identified, and the hybrid scaffolds significantly supported human skin cell attachment and viability. In conclusion, the fabricated hybrid scaffolds demonstrated optimum physicochemical and mechanical properties and may potentially be used as an acellular skin substitute in wound management.

Die hard: cell death mechanisms and their implications in nanotoxicology

Cell death is a fundamental biological process, and its fine-tuned regulation is required for life. However, the complexity of regulated cell death is often reduced to a matter of live-dead discrimination. Here, we provide a perspective on programmed or regulated cell death, focusing on apoptosis, pyroptosis, necroptosis, and ferroptosis (the latter three cell death modalities are examples of regulated necrosis). We also touch on other, recently described manifestations of (pathological) cell death including cuproptosis. Furthermore, we address how engineered nanomaterials impact on regulated cell death. We posit that an improved understanding of nanomaterial-induced perturbations of cell death may allow for a better prediction of the consequences of human exposure and could also yield novel approaches by which to mitigate these effects. Finally, we provide examples of the harnessing of nanomaterials to achieve cancer cell killing through the induction of regulated cell death.