Tumor Initiation Capacity and Therapy Resistance Are Differential Features of EMT-Related Subpopulations in the NSCLC Cell Line A549

Dynamic microphysiological system chip platform for high-throughput, customizable, and multi-dimensional drug screening

Spheroids and organoids have attracted significant attention as innovative models for disease modeling and drug screening. By employing diverse types of spheroids or organoids, it is feasible to establish microphysiological systems that enhance the precision of disease modeling and offer more dependable and comprehensive drug screening. High-throughput microphysiological systems that support optional, parallel testing of multiple drugs have promising applications in personalized medical treatment and drug research. However, establishing such a system is highly challenging and requires a multidisciplinary approach. This study introduces a dynamic Microphysiological System Chip Platform (MSCP) with multiple functional microstructures that encompass the mentioned advantages. We developed a high-throughput lung cancer spheroids model and an intestine-liver-heart-lung cancer microphysiological system for conducting parallel testing on four anti-lung cancer drugs, demonstrating the feasibility of the MSCP. This microphysiological system combines microscale and macroscale biomimetics to enable a comprehensive assessment of drug efficacy and side effects. Moreover, the microphysiological system enables evaluation of the real pharmacological effect of drug molecules reaching the target lesion after absorption by normal organs through fluid-based physiological communication. The MSCP could serves as a valuable platform for microphysiological system research, making significant contributions to disease modeling, drug development, and personalized medical treatment.

Modulation of PD-L1 by Astragalus polysaccharide attenuates the induction of melanoma stem cell properties and overcomes immune evasion

BACKGROUND

Melanoma is a highly aggressive form of skin cancer. The existence of cancer stem cells (CSCs) and tumor immune evasion are two major causes of melanoma progression, but no effective treatment has been found at present. Astragalus polysaccharide (APS) is a principal active component derived from Astragalus membranaceus, showing anti-tumor effects in various tumors including melanoma. However, the underlying mechanism is still unclear.

METHODS

The regulation of APS on self-renewal ability and CSC markers expression in melanoma stem cells (MSCs) was measured by tumor sphere formation and tumorigenicity assays, RT-qPCR, and western blot. Flow cytometry was conducted to evaluate the activation of immune system by APS in melanoma mice. Further, the mechanism was explored based on PD-L1 overexpression and knock-down B16 cells.

RESULTS

APS attenuated the tumor sphere formation of MSCs in vitro as well as the tumorigenicity in vivo. It also decreased the expression of CD133, BMI1 and CD47. Based on the PD-L1 overexpression and knock-down B16 cells, it was confirmed that APS inhibited the induction of MSCs by down-regulating PD-L1 expression. Meanwhile, APS increased the infiltration of CD4+ and CD8+T cells in tumor tissues because of its inhibitory effect on PD-L1.

CONCLUSIONS

APS inhibited MSC induction and overcame tumor immune evasion through reducing PD-L1 expression. This study provided compelling evidence that APS could be a prospective therapeutic agent for treating melanoma.

Chemotherapy increases CDA expression and sensitizes malignant pleural mesothelioma cells to capecitabine treatment

The combination of cisplatin and pemetrexed remains the gold standard chemotherapy for malignant pleural mesothelioma (MPM), although resistance and poor response pose a significant challenge. Cytidine deaminase (CDA) is a key enzyme in the nucleotide salvage pathway and is involved in the adaptive stress response to chemotherapy. The cytidine analog capecitabine and its metabolite 5'-deoxy-5-fluorocytidine (5'-DFCR) are converted via CDA to 5-fluorouracil, which affects DNA and RNA metabolism. This study investigated a schedule-dependent treatment strategy, proposing that initial chemotherapy induces CDA expression, sensitizing cells to subsequent capecitabine treatment. Basal CDA protein expression was low in different mesothelioma cell lines but increased in the corresponding xenografts. Standard chemotherapy increased CDA protein levels in MPM cells in vitro and in vivo in a schedule-dependent manner. This was associated with epithelial-to-mesenchymal transition and with HIF-1alpha expression at the transcriptional level. In addition, pretreatment with cisplatin and pemetrexed in combination sensitized MPM xenografts to capecitabine. Analysis of a tissue microarray (TMA) consisting of samples from 98 human MPM patients revealed that most human MPM samples had negative CDA expression. While survival curves based on CDA expression in matched samples clearly separated, significance was not reached due to the limited sample size. In non-matched samples, CDA expression before but not after neoadjuvant therapy was significantly associated with worse overall survival. In conclusion, chemotherapy increases CDA expression in xenografts, which is consistent with our in vitro results in MPM and lung cancer. A subset of matched patient samples showed increased CDA expression after therapy, suggesting that a schedule-dependent treatment strategy based on chemotherapy and capecitabine may benefit a selected MPM patient population.

From immune checkpoints to therapies: understanding immune checkpoint regulation and the influence of natural products and traditional medicine on immune checkpoint and immunotherapy in lung cancer

Lung cancer is a disease of global concern, and immunotherapy has brought lung cancer therapy to a new era. Besides promising effects in the clinical use of immune checkpoint inhibitors, immune-related adverse events (irAEs) and low response rates are problems unsolved. Natural products and traditional medicine with an immune-modulating nature have the property to influence immune checkpoint expression and can improve immunotherapy's effect with relatively low toxicity. This review summarizes currently approved immunotherapy and the current mechanisms known to regulate immune checkpoint expression in lung cancer. It lists natural products and traditional medicine capable of influencing immune checkpoints or synergizing with immunotherapy in lung cancer, exploring both their effects and underlying mechanisms. Future research on immune checkpoint modulation and immunotherapy combination applying natural products and traditional medicine will be based on a deeper understanding of their mechanisms regulating immune checkpoints. Continued exploration of natural products and traditional medicine holds the potential to enhance the efficacy and reduce the adverse reactions of immunotherapy.

RGMb impacts partial epithelial-mesenchymal transition and BMP2-Induced ID mRNA expression independent of PD-L2 in nonsmall cell lung cancer cells

PD-1/PD-ligand-axis immunotherapy-mediated activation of T-cells for cancer cell elimination is a promising treatment of nonsmall cell lung cancer (NSCLC). However, the effect of immunotherapy on intracellular signaling pathways in cancer cells still needs further delineation. Repulsive Guidance Molecule b (RGMb), a regulator of Bone Morphogenetic Proteins (BMPs) signaling, interacts with the PD-ligand, PD-L2, at cancer cell membranes. Accordingly, a clarification of the functions of RGMb and its relation to PD-L2 might provide insight into NSCLC cell signaling responses to PD-1/PD-ligand-axis immunotherapy. In this study, the functions of RGMb and PD-L2 were examined using the two NSCLC cell lines HCC827 and A549. CRISPR/Cas9 was used to decrease the expression of RGMb and PD-L2, while lentiviral vectors were used to increase their expression. Downstream effects were examined by RT-qPCR and immunoassays. Ectopic expression of RGMb impacted BMP2-induced expression of ID1 and ID2 messenger RNA (mRNA) independently of PD-L2, while RGMb depletion by CRISPR/Cas9 did not affect the BMP2-mediated induction of ID1, ID2, and ID3 mRNA. However, depletion of RGMb resulted in a partial epithelial-mesenchymal transition (EMT) gene expression profile in HCC827 cells, which was not mimicked by PD-L2 depletion. The results show that RGMb is a coregulator of BMP signaling and hence, ID mRNA expression and that RGMb can control the EMT balance in NSCLC cells. However, RGMb appears to exert these functions independently of PD-L2, and accordingly, the PD-1/PD-ligand axis for immune surveillance in NSCLC cells.

Anti-proliferative activity of nitroquinolone fused acylhydrazones as non-small cell human lung cancer agents

A new series of 8-nitroquinolone-based aromatic heterocyclic acyl hydrazones have been synthesised and characterised through various spectroscopic techniques. They were theoretically examined for molecular docking with various proteins related to the apoptosis of the non-small cell lung cancer cell line A549. The results indicate that the possible modes of interaction of all the synthesised compounds are compatible for use as anti-proliferative drugs. Also, the drug-likeness of the compounds was examined through theoretical ADMET analysis, which indicated good gastrointestinal absorption as well as low toxicity. Selected compounds were evaluated for their in vitro anti-cancer activity using A549, MCF-7 and HeLa cell lines through an MTT assay to determine cytotoxicity. Compounds 3c, 3a and 11c exhibited significant cytotoxicity towards A549 cells in the order of 3c (15.3 ± 0.7) > 3a (15.8 ± 0.1) > 11c (17.1 ± 0.2), whereas all the compounds show insignificant toxicity on normal human embryonic kidney cells up to a concentration of 200 μM. The best compounds among the series (3c and 11c) were chosen for further detection of apoptosis through fluorescence microscopic techniques using AO/EtBr and DAPI. The reduced DNA synthesis during the cell cycle was also investigated through flow cytometric techniques. The results indicate that the compounds possess significant anticancer properties due to the activation of the mitochondrial mediated intrinsic pathway.

Longitudinal characterization of TK6 cells sequentially adapted to animal product-free, chemically defined culture medium: considerations for genotoxicity studies

Introduction: In vitro approaches are an essential tool in screening for toxicity of new chemicals, products and therapeutics. To increase the reproducibility and human relevance of these in vitro assessments, it is advocated to remove animal-derived products such as foetal bovine serum (FBS) from the cell culture system. Currently, FBS is routinely used as a supplement in cell culture medium, but batch-to-batch variability may introduce inconsistency in inter- and intra-lab assessments. Several chemically defined serum replacements (CDSR) have been developed to provide an alternative to FBS, but not every cell line adapts easily and successfully to CDSR-supplemented medium, and the long-term effect on cell characteristics remains uncertain. Aim: The aim of this study was to adapt the TK6 cell line to animal-product free CDSR-supplemented medium and evaluate the long-term effects on cell health, growth, morphology, phenotype, and function. This included a provisional assessment to determine the suitability of the transitioned cell line for standardised genotoxicity testing using the "in vitro mammalian cell micronucleus test" (OECD TG 487). Materials and methods: Gradual adaptation and direct adaptation methodologies were compared by assessing the cell proliferation, size and viability every passage until the cells were fully adapted to animal-free CDSR. The metabolic activity and membrane integrity was assessed every 4-8 passages by PrestoBlue and CytoTox-ONE™ Homogeneous Membrane Integrity Assay respectively. A detailed morphology study by high content imaging was performed and the expression of cell surface markers (CD19 and CD20) was conducted via flow cytometry to assess the potential for phenotypic drift during longer term culture of TK6 in animal-free conditions. Finally, functionality of cells in the OECD TG 487 assay was evaluated. Results: The baseline characteristics of TK6 cells cultured in FBS-supplemented medium were established and variability among passages was used to set up acceptance criteria for CDSR adapted cells. TK6 were adapted to CDSR supplemented medium either via direct or gradual transition reducing from 10% v/v FBS to 0% v/v FBS. The cell growth rate was compromised in the direct adaptation and therefore the gradual adaptation was preferred to investigate the long-term effects of animal-free CDSR on TK6 cells. The new animal cells showed comparable (p > 0.05) viability and cell size as the parent FBS-supplemented cells, with the exception of growth rate. The new animal free cells showed a lag phase double the length of the original cells. Cell morphology (cellular and nuclear area, sphericity) and phenotype (CD19 and CD20 surface markers) were in line (p > 0.05) with the original cells. The new cells cultured in CDSR-supplemented medium performed satisfactory in a pilot OECD TG 487 assay with compounds not requiring metabolic activation. Conclusion: TK6 cells were successfully transitioned to FBS- and animal product-free medium. The new cell cultures were viable and mimicked the characteristics of FBS-cultured cells. The gradual transition methodology utilised in this study can also be applied to other cell lines of interest. Maintaining cells in CDSR-supplemented medium eliminates variability from FBS, which in turn is likely to increase the reproducibility of in vitro experiments. Furthermore, removal of animal derived products from cell culture techniques is likely to increase the human relevance of in vitro methodologies.

A Monoclonal Human Alveolar Epithelial Cell Line ("Arlo") with Pronounced Barrier Function for Studying Drug Permeability and Viral Infections

In the development of orally inhaled drug products preclinical animal models regularly fail to predict pharmacological as well as toxicological responses in humans. Models based on human cells and tissues are potential alternatives to animal experimentation allowing for the isolation of essential processes of human biology and making them accessible in vitro. Here, the generation of a novel monoclonal cell line "Arlo," derived from the polyclonal human alveolar epithelium lentivirus immortalized cell line hAELVi via single-cell printing, and its characterization as a model for the human alveolar epithelium as well as a building block for future complex in vitro models is described. "Arlo" is systematically compared in vitro to primary human alveolar epithelial cells (hAEpCs) as well as to the polyclonal hAELVi cell line. "Arlo" cells show enhanced barrier properties with high transepithelial electrical resistance (TEER) of ≈3000 Ω cm2 and a potential difference (PD) of ≈30 mV under air-liquid interface (ALI) conditions, that can be modulated. The cells grow in a polarized monolayer and express genes relevant to barrier integrity as well as homeostasis as is observed in hAEpCs. Successful productive infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a proof-of-principle study offers an additional, attractive application of "Arlo" beyond biopharmaceutical experimentation.

Schedule-Dependent Treatment Increases Chemotherapy Efficacy in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare but aggressive thoracic malignancy with limited treatment options. One of the standard treatments for MPM is chemotherapy, which consists of concurrent treatment with pemetrexed and cisplatin. Pemetrexed limits tumor growth by inhibiting critical metabolic enzymes involved in nucleotide synthesis. Cisplatin causes direct DNA damage, such as intra-strand and inter-strand cross-links, which are repaired by the nucleotide excision repair pathway, which depends on relatively high nucleotide levels. We hypothesized that prolonged pretreatment with pemetrexed might deplete nucleotide pools, thereby sensitizing cancer cells to subsequent cisplatin treatment. The MPM cell lines ACC-MESO-1 and NCI-H28 were treated for 72 h with pemetrexed. Three treatment schedules were evaluated by initiating 24 h of cisplatin treatment at 0 h (concomitant), 24 h, and 48 h relative to pemetrexed treatment, resulting in either concomitant administration or pemetrexed pretreatment for 24 h or 48 h, respectively. Multicolor flow cytometry was performed to detect γH2AX (phosphorylation of histone H2AX), a surrogate marker for the activation of the DNA damage response pathway. DAPI staining of DNA was used to analyze cell cycle distribution. Forward and side scatter intensity was used to distinguish subpopulations based on cellular size and granularity, respectively. Our study revealed that prolonged pemetrexed pretreatment for 48 h prior to cisplatin significantly reduced long-term cell growth. Specifically, pretreatment for 48 h with pemetrexed induced a cell cycle arrest, mainly in the G2/M phase, accumulation of persistent DNA damage, and induction of a senescence phenotype. The present study demonstrates that optimizing the treatment schedule by pretreatment with pemetrexed increases the efficacy of the pemetrexed-cisplatin combination therapy in MPM. We show that the observed benefits are associated with the persistence of treatment-induced DNA damage. Our study suggests that an adjustment of the treatment schedule could improve the efficacy of the standard chemotherapy regimen for MPM and might improve patient outcomes.

In Vitro Effects of Fungal Phytotoxins on Cancer Cell Viability: First Insight into Structure Activity Relationship of a Potent Metabolite of Cochliobolus australiensis Radicinin

Natural compounds have always represented an important source for new drugs. Although fungi represent one such viable source, to date, no fungal metabolite has been marketed as an anticancer drug. Based on our work with phytotoxins as potential chemical scaffolds and our recent findings involving three phytopathogenic fungi, i.e., Cochliobolus australiensis, Kalmusia variispora and Hymenoscyphus fraxineus, herein, we evaluate the in vitro anti-cancer activity of the metabolites of these fungi by MTT assays on three cancer cell models harboring various resistance levels to chemotherapeutic drugs. Radicinin, a phytotoxic dihydropyranopyran-4,5-dione produced by Cochliobolus australiensis, with great potential for the biocontrol of the invasive weed buffelgrass (Cenchrus ciliaris), showed significant anticancer activity in the micromolar range. Furthermore, a SAR study was carried out using radicinin, some natural analogues and hemisynthetic derivatives prepared by synthetic methods developed as part of work aimed at the potential application of these molecules as bioherbicides. This investigation opens new avenues for the design and synthesis of novel radicinin analogues as potential anticancer agents.

Targeting lactate dehydrogenase B-dependent mitochondrial metabolism affects tumor initiating cells and inhibits tumorigenesis of non-small cell lung cancer by inducing mtDNA damage

Once considered a waste product of anaerobic cellular metabolism, lactate has been identified as a critical regulator of tumorigenesis, maintenance, and progression. The putative primary function of lactate dehydrogenase B (LDHB) is to catalyze the conversion of lactate to pyruvate; however, its role in regulating metabolism during tumorigenesis is largely unknown. To determine whether LDHB plays a pivotal role in tumorigenesis, we performed 2D and 3D in vitro experiments, utilized a conventional xenograft tumor model, and developed a novel genetically engineered mouse model (GEMM) of non-small cell lung cancer (NSCLC), in which we combined an LDHB deletion allele with an inducible model of lung adenocarcinoma driven by the concomitant loss of p53 (also known as Trp53) and expression of oncogenic KRAS (G12D) (KP). Here, we show that epithelial-like, tumor-initiating NSCLC cells feature oxidative phosphorylation (OXPHOS) phenotype that is regulated by LDHB-mediated lactate metabolism. We show that silencing of LDHB induces persistent mitochondrial DNA damage, decreases mitochondrial respiratory complex activity and OXPHOS, resulting in reduced levels of mitochondria-dependent metabolites, e.g., TCA intermediates, amino acids, and nucleotides. Inhibition of LDHB dramatically reduced the survival of tumor-initiating cells and sphere formation in vitro, which can be partially restored by nucleotide supplementation. In addition, LDHB silencing reduced tumor initiation and growth of xenograft tumors. Furthermore, we report for the first time that homozygous deletion of LDHB significantly reduced lung tumorigenesis upon the concomitant loss of Tp53 and expression of oncogenic KRAS without considerably affecting the animal's health status, thereby identifying LDHB as a potential target for NSCLC therapy. In conclusion, our study shows for the first time that LDHB is essential for the maintenance of mitochondrial metabolism, especially nucleotide metabolism, demonstrating that LDHB is crucial for the survival and proliferation of NSCLC tumor-initiating cells and tumorigenesis.

Maximizing the relevance and reproducibility of A549 cell culture using FBS-free media

Scientists are using in vitro methods to answer important research questions and implementing strategies to maximize the reliability and human relevance of these methods. One strategy is to replace the use of fetal bovine serum (FBS)-an undefined and variable mixture of biomolecules-in cell culture media with chemically defined or xeno-free medium. In this study, A549 cells, a human lung alveolar-like cell line commonly used in respiratory research, were transitioned from a culture medium containing FBS to media without FBS. A successful transition was determined based on analysis of cell morphology and functionality. Following transition to commercially available CnT-Prime Airway (CELLnTEC) or X-VIVO™ 10 (Lonza) medium, the cells were characterized by microscopic evaluation and calculation of doubling time. Their genotype, morphology, and functionality were assessed by monitoring the expression of gene markers for lung cell types, surfactant production, cytokine release, the presence of multilamellar bodies, and cell viability following sodium dodecyl sulphate exposure. Our results showed that A549 cells successfully transitioned to FBS-free media under submerged and air-liquid-interface conditions. Cells grown in X-VIVO™ 10 medium mimicked cellular characteristics of FBS-supplemented media while those grown in CnT-Prime Airway medium demonstrated characteristics possibly more reflective of normal human alveolar epithelial cells.

A novel EHD1/CD44/Hippo/SP1 positive feedback loop potentiates stemness and metastasis in lung adenocarcinoma

BACKGROUND

There is growing evidence that endocytosis plays a pivotal role in cancer metastasis. In this study, we first identified endocytic and metastasis-associated genes (EMGs) and then investigated the biological functions and mechanisms of EMGs.

METHODS

Cancer stem cells (CSCs)-like characteristics were evaluated by tumour limiting dilution assays, three-dimensional (3D) spheroid cancer models. Microarray analysis was used to identify the pathways significantly regulated by mammalian Eps15 homology domain protein 1 (EHD1) knockdown. Mass spectrometry (MS) was performed to identify EHD1-interacting proteins. The function of EHD1 as a regulator of cluster of differentiation 44 (CD44) endocytic recycling and lysosomal degradation was determined by CD44 biotinylation and recycling assays.

RESULTS

EHD1 was identified as a significant EMG. Knockdown of EHD1 suppressed CSCs-like characteristics, epithelial-mesenchymal transition (EMT), migration and invasion of lung adenocarcinoma (LUAD) cells by increasing Hippo kinase cascade activation. Conversely, EHD1 overexpression inhibited the Hippo pathway to promote cancer stemness and metastasis. Notably, utilising MS analysis, the CD44 protein was identified as a potential binding partner of EHD1. Furthermore, EHD1 enhanced CD44 recycling and stability. Indeed, silencing of CD44 or disruption of the EHD1/CD44 interaction enhanced Hippo pathway activity and reduced CSCs-like traits, EMT and metastasis. Interestingly, specificity protein 1 (SP1), a known downstream target gene of the Hippo-TEA-domain family members 1 (TEAD1) pathway, was found to directly bind to the EHD1 promoter region and induce its expression. Among clinical specimens, the EHD1 expression level in LUAD tissues of metastatic patients was higher than that of non-metastatic patients.

CONCLUSIONS

Our findings emphasise that EHD1 might be a potent anti-metastatic target and present a novel regulatory mechanism by which the EHD1/CD44/Hippo/SP1 positive feedback circuit plays pivotal roles in coupling modules of CSCs-like properties and EMT in LUAD. Targeting this loop may serve as a remedy for patients with advanced metastatic LUAD.

Pan-cancer quantitation of epithelial-mesenchymal transition dynamics using parallel reaction monitoring-based targeted proteomics approach

Epithelial–mesenchymal transition (EMT) is a dynamic and complex cellular process that is known to be hijacked by cancer cells to facilitate invasion, metastasis and therapeutic resistance. Several quantitative measures to assess the interplay between EMT and cancer progression are available, based on large scale genome and transcriptome data. However, these large scale multi-omics studies have repeatedly illustrated a lack of correlation in mRNA and protein abundances that may be influenced by diverse post-translational regulation. Hence, it is imperative to understand how changes in the EMT proteome are associated with the process of oncogenic transformation. To this effect, we developed a parallel reaction monitoring-based targeted proteomics method for quantifying abundances of EMT-associated proteins across cancer cell lines. Our study revealed that quantitative measurement of EMT proteome which enabled a more accurate assessment than transcriptomics data and revealed specific discrepancies against a backdrop of generally strong concordance between proteomic and transcriptomic data. We further demonstrated that changes in our EMT proteome panel might play a role in tumor transformation across cancer types. In future, this EMT panel assay has the potential to be used for clinical samples to guide treatment choices and to congregate functional information for the development and advancing novel therapeutics.

Interconnected high-dimensional landscapes of epithelial-mesenchymal plasticity and stemness in cancer

Establishing macrometastases at distant organs is a highly challenging process for cancer cells, with extremely high attrition rates. A very small percentage of disseminated cells have the ability to dynamically adapt to their changing micro-environments through reversibly switching to another phenotype, aiding metastasis. Such plasticity can be exhibited along one or more axes-epithelial-mesenchymal plasticity (EMP) and cancer stem cells (CSCs) being the two most studied, and often tacitly assumed to be synonymous. Here, we review the emerging concepts related to EMP and CSCs across multiple cancers. Both processes are multi-dimensional in nature; for instance, EMP can be defined on morphological, molecular and functional changes, which may or may not be synchronized. Similarly, self-renewal, multi-lineage potential, and resistance to anoikis and/or therapy may not all occur simultaneously in CSCs. Thus, understanding the complexity in defining EMP and CSCs is essential if we are to understand their contribution to cancer metastasis. This will require a more comprehensive understanding of the non-linearity of these processes. These processes are dynamic, reversible, and semi-independent in nature; cells traverse the inter-connected high-dimensional EMP and CSC landscapes in diverse paths, each of which may exhibit a distinct EMP-CSC coupling. Our proposed model offers a potential unifying framework for elucidating the coupled decision-making along these dimensions and highlights a key set of open questions to be answered.

Glutamine promotes escape from therapy-induced senescence in tumor cells

Therapy-induced senescence (TIS) is a major cellular response to anticancer therapies. While induction of a persistent growth arrest would be a desirable outcome in cancer therapy, it has been shown that, unlike normal cells, cancer cells are able to evade the senescence cell cycle arrest and to resume proliferation, likely contributing to tumor relapse. Notably, cells that escape from TIS acquire a plastic, stem cell-like phenotype. The metabolic dependencies of cells that evade senescence have not been thoroughly studied. In this study, we show that glutamine depletion inhibits escape from TIS in all cell lines studied, and reduces the stem cell subpopulation. In line with a metabolic reliance on glutamine, escaped clones overexpress the glutamine transporter SLC1A5. We also demonstrate a central role of glutamine synthetase that mediates resistance to glutamine deprivation, conferring independence from exogenous glutamine. Finally, rescue experiments demonstrate that glutamine provides nitrogen for nucleotides biosynthesis in cells that escape from TIS, but also suggest a critical involvement of glutamine in other metabolic and non-metabolic pathways. On the whole, these results reveal a metabolic vulnerability of cancer stem cells that recover proliferation after exposure to anticancer therapies, which could be exploited to prevent tumor recurrence.

Identification of Chemo and Radio-Resistant Sub-Population of Stem Cells in Human Cervical Cancer HeLa Cells

BACKGROUND

Cervical cancer ranks the second female malignancy after breast cancer. Cancer stem cells (CSCs) are hard to be eradicated, so can recur. We aim to isolate and characterize CSCs from HeLa cells.

METHODS

These cells express clusters of differentiation (CDs), 44 and 24, to be sorted by fluorescence-activated cell sorting (FACS).

RESULTS

CD44⁺CD24⁺ cells showed potential to form spheres, tumorigenicity, stemness genes and higher resistance to cisplatin, X-ray.

CONCLUSION

CD44⁺CD24⁺ HeLa cells hold characteristics of CSCs, in vitro, in vivo studies, suggesting that targeting may lead to screening of new anti-cancer therapies.

Chemotherapy-induced CDA expression renders resistant non-small cell lung cancer cells sensitive to 5'-deoxy-5-fluorocytidine (5'-DFCR)

BACKGROUND

Pemetrexed (MTA) plus cisplatin combination therapy is considered the standard of care for patients with advanced non-small-cell lung cancer (NSCLC). However, in advanced NSCLC, the 5-year survival rate is below 10%, mainly due to resistance to therapy. We have previously shown that the fraction of mesenchymal-like, chemotherapy-resistant paraclone cells increased after MTA and cisplatin combination therapy in the NSCLC cell line A549. Cytidine deaminase (CDA) and thymidine phosphorylase (TYMP) are key enzymes of the pyrimidine salvage pathway. 5'-deoxy-5-fluorocytidine (5'-DFCR) is a cytidine analogue (metabolite of capecitabine), which is converted by CDA and subsequently by TYMP into 5-fluorouracil, a chemotherapeutic agent frequently used to treat solid tumors. The aim of this study was to identify and exploit chemotherapy-induced metabolic adaptations to target resistant cancer cells.

METHODS

Cell viability and colony formation assays were used to quantify the efficacy of MTA and cisplatin treatment in combination with schedule-dependent addition of 5'-DFCR on growth and survival of A549 paraclone cells and NSCLC cell lines. CDA and TYMP protein expression were monitored by Western blot. Finally, flow cytometry was used to analyze the EMT phenotype, DNA damage response activation and cell cycle distribution over time after treatment. CDA expression was measured by immunohistochemistry in tumor tissues of patients before and after neoadjuvant chemotherapy.

RESULTS

We performed a small-scale screen of mitochondrial metabolism inhibitors, which revealed that 5'-DFCR selectively targets chemotherapy-resistant A549 paraclone cells characterized by high CDA and TYMP expression. In the cell line A549, CDA and TYMP expression was further increased by chemotherapy in a time-dependent manner, which was also observed in the KRAS-addicted NSCLC cell lines H358 and H411. The addition of 5'-DFCR on the second day after MTA and cisplatin combination therapy was the most efficient treatment to eradicate chemotherapy-resistant NSCLC cells. Moreover, recovery from treatment-induced DNA damage was delayed and accompanied by senescence induction and acquisition of a hybrid-EMT phenotype. In a subset of patient tumors, CDA expression was also increased after treatment with neoadjuvant chemotherapy.

CONCLUSIONS

Chemotherapy increases CDA and TYMP expression thereby rendering resistant lung cancer cells susceptible to subsequent 5'-DFCR treatment.

Exposure of Human Lung Cells to Polystyrene Microplastics Significantly Retards Cell Proliferation and Triggers Morphological Changes

Microplastics in the environment produced by decomposition of globally increasing waste plastics have become a dominant component of both water and air pollution. To examine the potential toxicological effects of microplastics on human cells, the cultured human alveolar A549 cells were exposed to polystyrene microplastics (PS-MPs) of 1 and 10 μm diameter as a model of the environmental contaminants. Both sizes caused a significant reduction in cell proliferation but exhibited little cytotoxicity, as measured by the maintenance of cell viabilities determined by trypan blue staining and by Calcein-AM staining. The cell viabilities did not drop below 93% even at concentrations of PS-MPs as high as 100 μg/mL. Despite these high viabilities, further assays revealed a population level decrease in metabolic activity parallel in time with a dramatic decrease in proliferation rate in PS-MP exposed cells. Furthermore, phase contrast imaging of live cells at 72 h revealed major changes in the morphology of cells exposed to microplastics, as well as the uptake of multiple 1 μm PS-MPs into the cells. Confocal fluorescent microscopy at 24 h of exposure confirmed the incorporation of 1 μm PS-MPs. These disturbances at the proliferative and cytoskeletal levels of human cells lead us to propose that airborne polystyrene microplastics may have toxicologic consequences. This is the first report of exposure of human cells to an environmental contaminant resulting in the dual effects of inhibition of cell proliferation and major changes in cell morphology. Our results make clear that human exposure to microplastic pollution has significant consequence and potential for harm to humans.

Knockdown of E-cadherin induces cancer stem-cell-like phenotype and drug resistance in cervical cancer cells

Cervical cancer is one of the leading causes of mortality amongst women in developing countries, and resistance to therapy is the main reason for treatment failure. Recent advances suggest that cancer stem cells (CSCs) are critically involved in regulating the chemo-resistant behavior of cervical cancer cells. In our study, cells with the CSC phenotype were isolated, and we examined the expression levels of stem cell markers and genes associated with epithelial-mesenchymal transition (EMT) using different assays. However, the cells with the CSC phenotype could not be cultured for further cytotoxicity studies, so we established a model of CSC in cervical cancer cells. We performed siRNA-mediated knockdown of E-cadherin in these cells, and studied them for EMT-associated stem-cell-like properties. We also performed dose-dependent cell viability assays using clinically relevant drugs such as cisplatin, cyclopamine, and GANT58 to analyze the drug resistant behavior of these cancer cells. We found that knockdown of E-cadherin induces EMT in cervical cancer cells, imparting stem-cell like characteristics along with enhanced tumorsphere formation, cell migration, invasiveness, and drug resistance. This is the first study to establish a CSC model in cervical cancer cells by knockdown of E-cadherin, which can be used to develop anti-cancer therapies.

Inference and analysis of cell-cell communication using CellChat

Understanding global communications among cells requires accurate representation of cell-cell signaling links and effective systems-level analyses of those links. We construct a database of interactions among ligands, receptors and their cofactors that accurately represent known heteromeric molecular complexes. We then develop CellChat, a tool that is able to quantitatively infer and analyze intercellular communication networks from single-cell RNA-sequencing (scRNA-seq) data. CellChat predicts major signaling inputs and outputs for cells and how those cells and signals coordinate for functions using network analysis and pattern recognition approaches. Through manifold learning and quantitative contrasts, CellChat classifies signaling pathways and delineates conserved and context-specific pathways across different datasets. Applying CellChat to mouse and human skin datasets shows its ability to extract complex signaling patterns. Our versatile and easy-to-use toolkit CellChat and a web-based Explorer ( http://www.cellchat.org/ ) will help discover novel intercellular communications and build cell-cell communication atlases in diverse tissues.

Mathematical Modeling of Plasticity and Heterogeneity in EMT

The epithelial-mesenchymal transition (EMT) and the corresponding reverse process, mesenchymal-epithelial transition (MET), are dynamic and reversible cellular programs orchestrated by many changes at both biochemical and morphological levels. A recent surge in identifying the molecular mechanisms underlying EMT/MET has led to the development of various mathematical models that have contributed to our improved understanding of dynamics at single-cell and population levels: (a) multi-stability-how many phenotypes can cells attain during an EMT/MET?, (b) reversibility/irreversibility-what time and/or concentration of an EMT inducer marks the "tipping point" when cells induced to undergo EMT cannot revert?, (c) symmetry in EMT/MET-do cells take the same path when reverting as they took during the induction of EMT?, and (d) non-cell autonomous mechanisms-how does a cell undergoing EMT alter the tendency of its neighbors to undergo EMT? These dynamical traits may facilitate a heterogenous response within a cell population undergoing EMT/MET. Here, we present a few examples of designing different mathematical models that can contribute to decoding EMT/MET dynamics.

Phenotypic Heterogeneity in Tumor Progression, and Its Possible Role in the Onset of Cancer

Heterogeneity among isogenic cells/individuals has been known for at least 150 years. Even Mendel, working on pea plants, realized that not all tall plants were identical. However, Mendel was more interested in the discontinuous variation between genetically distinct individuals. The concept of environment dictating distinct phenotypes among isogenic individuals has since been shown to impact the evolution of populations in numerous examples at different scales of life. In this review, we discuss how phenotypic heterogeneity and its evolutionary implications exist at all levels of life, from viruses to mammals. In particular, we discuss how a particular disease condition (cancer) is impacted by heterogeneity among isogenic cells, and propose a potential role that phenotypic heterogeneity might play toward the onset of the disease.

Thymidylate synthase drives the phenotypes of epithelial-to-mesenchymal transition in non-small cell lung cancer

Background

Epithelial-to-mesenchymal transition (EMT) enhances motility, stemness, chemoresistance and metastasis. Little is known about how various pathways coordinate to elicit EMT’s different functional aspects in non-small cell lung cancer (NSCLC). Thymidylate synthase (TS) has been previously correlated with EMT transcription factor ZEB1 in NSCLC and imparts resistance against anti-folate chemotherapy. In this study, we establish a functional correlation between TS, EMT, chemotherapy and metastasis and propose a network for TS mediated EMT.

Methods

Published datasets were analysed to evaluate the significance of TS in NSCLC fitness and prognosis. Promoter reporter assay was used to sort NSCLC cell lines in TS^HIGH and TS^LOW. Metastasis was assayed in a syngeneic mouse model.

Results

TS levels were prognostic and predicted chemotherapy response. Cell lines with higher TS promoter activity were more mesenchymal-like. RNA-seq identified EMT as one of the most differentially regulated pathways in connection to TS expression. EMT transcription factors HOXC6 and HMGA2 were identified as upstream regulator of TS, and AXL, SPARC and FOSL1 as downstream effectors. TS knock-down reduced the metastatic colonisation in vivo.

Conclusion

These results establish TS as a theranostic NSCLC marker integrating survival, chemo-resistance and EMT, and identifies a regulatory network that could be targeted in EMT-driven NSCLC.

Distinct characteristics of dasatinib-induced pyroptosis in gasdermin E-expressing human lung cancer A549 cells and neuroblastoma SH-SY5Y cells

Dasatinib, a multikinase inhibitor, is used in the treatment of chronic myeloid leukemia and was developed to overcome imatinib resistance. Its mechanism of action involves the induction of apoptosis, autophagy and necroptosis. However, it remains unclear whether dasatinib can induce pyroptosis. In the present study, gasdermin E (GSDME)-expressing SH-SY5Y and A549 cells were chosen for investigation. Typical pyroptotic features, such as cleavage of GSDME protein, leakage of lactate dehydrogenase and large bubbled morphology, were observed in both cell lines after exposure to dasatinib. The generation of GSDME fragments was inhibited by specific caspase-3 inhibitor zDEVD in SH-SY5Y cells and pan-caspase inhibitor zVAD in A549 cells. Moreover, distinct characteristics of pyroptosis were observed in A549 cells, which occurred only with a high percentage of Annexin V/propidium iodide double-stained cells and low level of GSDME protein cleavage. The sensitivity of A549 cells to dasatinib is significantly reduced by increasing cell numbers. The elevation of GSDMD and GSDME protein levels was induced by low concentrations of dasatinib, which was not influenced by the reduction of p53 protein with RNA interference. In conclusion, to the best of our knowledge, this is the first study to report that dasatinib can induce pyroptosis in tumor cells and increase the protein levels of GSDMD and GSDME in a p53-independent manner.

A mechanism for epithelial-mesenchymal heterogeneity in a population of cancer cells

Epithelial-mesenchymal heterogeneity implies that cells within the same tumor can exhibit different phenotypes-epithelial, mesenchymal, or one or more hybrid epithelial-mesenchymal phenotypes. This behavior has been reported across cancer types, both in vitro and in vivo, and implicated in multiple processes associated with metastatic aggressiveness including immune evasion, collective dissemination of tumor cells, and emergence of cancer cell subpopulations with stem cell-like properties. However, the ability of a population of cancer cells to generate, maintain, and propagate this heterogeneity has remained a mystifying feature. Here, we used a computational modeling approach to show that epithelial-mesenchymal heterogeneity can emerge from the noise in the partitioning of biomolecules (such as RNAs and proteins) among daughter cells during the division of a cancer cell. Our model captures the experimentally observed temporal changes in the fractions of different phenotypes in a population of murine prostate cancer cells, and describes the hysteresis in the population-level dynamics of epithelial-mesenchymal plasticity. The model is further able to predict how factors known to promote a hybrid epithelial-mesenchymal phenotype can alter the phenotypic composition of a population. Finally, we used the model to probe the implications of phenotypic heterogeneity and plasticity for different therapeutic regimens and found that co-targeting of epithelial and mesenchymal cells is likely to be the most effective strategy for restricting tumor growth. By connecting the dynamics of an intracellular circuit to the phenotypic composition of a population, our study serves as a first step towards understanding the generation and maintenance of non-genetic heterogeneity in a population of cancer cells, and towards the therapeutic targeting of phenotypic heterogeneity and plasticity in cancer cell populations.

Cisplatin-resistant A549 non-small cell lung cancer cells can be identified by increased mitochondrial mass and are sensitive to pemetrexed treatment

Background

Cisplatin plus pemetrexed combination therapy is considered the standard treatment for patients with advanced, non-squamous, non-small-cell lung cancer (NSCLC). However, advanced NSCLC has a 5-year survival rate of below 10%, which is mainly due to therapy resistance. We previously showed that the NSCLC cell line A549 harbors different subpopulations including a mesenchymal-like subpopulation characterized by increased chemo- and radiotherapy resistance. Recently, therapy resistance in hematological and solid tumors has been associated with increased mitochondrial activity. Thus, the aim of this study was to investigate the role of the mitochondrial activity in NSCLC chemotherapy resistance.

Methods

Based on MitoTracker staining, subpopulations characterized by the highest 10% (Mito-High) or lowest 10% (Mito-Low) mitochondrial mass content were sorted by FACS (Fluorescence-Activated Cell Sorting) from paraclonal cultures of the NSCLC A549 cell line . Mitochondrial DNA copy numbers were quantified by real-time PCR whereas basal cellular respiration was measured by high-resolution respirometry. Cisplatin and pemetrexed response were quantified by proliferation and colony formation assay.

Results

Pemetrexed treatment of parental A549 cells increased mitochondrial mass over time. FACS-sorted paraclonal Mito-High cells featured increased mitochondrial mass and mitochondrial DNA copy number compared to the Mito-Low cells. Paraclonal Mito-High cells featured an increased proliferation rate and were significantly more resistant to cisplatin treatment than Mito-Low cells. Interestingly, cisplatin-resistant, paraclonal Mito-High cells were significantly more sensitive to pemetrexed treatment than Mito-Low cells. We provide a working model explaining the molecular mechanism underlying the increased cisplatin- and decreased pemetrexed resistance of a distinct subpopulation characterized by high mitochondrial mass.

Conclusions

This study revealed that cisplatin resistant A549 lung cancer cells can be identified by their increased levels of mitochondrial mass. However, Mito-High cells feature an increased sensitivity to pemetrexed treatment. Thus, pemetrexed and cisplatin target reciprocal lung cancer subpopulations, which could explain the increased efficacy of the combination therapy in the clinical setting.

B4GALT1 Is a New Candidate to Maintain the Stemness of Lung Cancer Stem Cells

BACKGROUND

According to the cancer stem cells (CSCs) hypothesis, a population of cancer cells with stem cell properties is responsible for tumor propagation, drug resistance, and disease recurrence. Study of the mechanisms responsible for lung CSCs propagation is expected to provide better understanding of cancer biology and new opportunities for therapy.

METHODS

The Lung Adenocarcinoma (LUAD) NCI-H460 cell line was grown either as 2D or as 3D cultures. Transcriptomic and genome-wide chromatin accessibility studies of 2D vs. 3D cultures were carried out using RNA-sequencing and Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-seq), respectively. Reverse transcription polymerase chain reaction (RT-PCR) was also carried out on RNA extracted from primary cultures derived from malignant pleural effusions to validate RNA-seq results.

RESULTS

RNA-seq and ATAC-seq data disentangled transcriptional and genome accessibility variability of 3D vs. 2D cultures in NCI-H460 cells. The examination of genomic landscape of genes upregulated in 3D vs. 2D cultures led to the identification of 2D cultures led to the identification of Beta-1,4-galactosyltranferase 1 (B4GALT1) as the top candidate. B4GALT1 as the top candidate. B4GALT1 was validated as a stemness factor, since its silencing caused strong inhibition of 3D spheroid formation.

CONCLUSION

Combined transcriptomic and chromatin accessibility study of 3D vs. 2D LUAD cultures led to the identification of B4GALT1 as a new factor involved in the propagation and maintenance of LUAD CSCs.

HSP90/AXL/eIF4E-regulated unfolded protein response as an acquired vulnerability in drug-resistant KRAS-mutant lung cancer

Drug resistance and tumor heterogeneity are formidable challenges in cancer medicine, which is particularly relevant for KRAS-mutant cancers, the epitome of malignant tumors recalcitrant to targeted therapy efforts and first-line chemotherapy. In this study, we delineate that KRAS-mutant lung cancer cells resistant to pemetrexed (MTA) and anti-MEK drug trametinib acquire an exquisite dependency on endoplasmic reticulum (ER) stress signaling, rendering resistant cancer cells selectively susceptible to blockage of HSP90, the receptor tyrosine kinase AXL, the eukaryotic translation initiation factor 4E (eIF4E), and the unfolded protein response (UPR). Mechanistically, acquisition of drug resistance enables KRAS-mutant lung cancer cells to bypass canonical KRAS effectors but entail hyperactive AXL/eIF4E, increased protein turnover in the ER, and adaptive activation of an ER stress-relief UPR survival pathway whose integrity is maintained by HSP90. Notably, the unique dependency and sensitivity induced by drug resistance are applicable to KRAS-mutant lung cancer cells undergoing de novo intratumor heterogeneity. In line with these findings, HSP90 inhibitors synergistically enhance antitumor effects of MTA and trametinib, validating a rational combination strategy to treat KRAS-mutant lung cancer. Collectively, these results uncover collateral vulnerabilities co-occurring with drug resistance and tumor heterogeneity, informing novel therapeutic avenues for KRAS-mutant lung cancer.

Advances in Molecular Mechanisms and Immunotherapy Involving the Immune Cell-Promoted Epithelial-to-Mesenchymal Transition in Lung Cancer

Immunotherapy has offered a new opportunity for the treatment of many malignancies. In patients with lung cancer, immune checkpoint inhibitors have significantly improved survival. However, little is known about predictive factors or primary and acquired resistance mechanisms. Epithelial-to-mesenchymal transition (EMT) is a complex of phenotypic changes involved in carcinogenesis and resistance to cancer treatments. Specifically, immune cells in the tumor microenvironment can promote EMT, and mesenchymal phenotype acquisition negatively regulates the anticancer immune response. EMT is associated with higher expression of PD-L1 and other immune checkpoints. In this review, we focused on the role of EMT in the interplay between tumor cells and the immune system, with particular emphasis on lung cancer. On the basis of our findings, we hypothesize that the effects of EMT on immune cells could be overcome in this disease by a new combination of immune checkpoint inhibitors.

MiR-4319 hinders YAP expression to restrain non-small cell lung cancer growth through regulation of LIN28-mediated RFX5 stability

Non-small cell lung cancer (NSCLC) is demonstrated as one of the most common malignant tumors and accounts for about 25% of cancer-related deaths each year. Extensive bodies of studies have manifested that microRNAs (miRNAs) play pivotal roles in the development of numerous malignant tumors by involving in modulation of cell biological processes. Although miR-4319 has been validated to execute tumor suppressor properties in triple-negative breast cancer, explorations on the function and latent mechanism of miR-4319 participating in NSCLC are still unclear. In this study, we proved that miR-4319 acted as a tumor suppressor in NSCLC progression via restraining cell proliferation and migration as well as boosting apoptosis. Further, miR-4319 bound with LIN28 and negatively regulated the expression of LIN28. Our data unveiled that LIN28 promoted RFX5 mRNA stability and miR-4319 led to the destabilization of RFX5 by targeting LIN28. In addition, RFX5 motivated the transcription of YAP and enhanced expression of YAP abolished the miR-4319 upregulation-mediated suppressive regulation of NSCLC tumorigenesis. In conclusion, miR-4319 dampened YAP expression to mitigate the tumorigenesis of NSCLC through inhibiting LIN28-mediated RFX5 stability, which offered an insight into the molecular mechanism underlying miR-4319 in NSCLC development.