In vitro inflammation and toxicity assessment of pre- and post-incinerated organomodified nanoclays to macrophages using high-throughput screening approaches

BACKGROUND

Organomodified nanoclays (ONC), two-dimensional montmorillonite with organic coatings, are increasingly used to improve nanocomposite properties. However, little is known about pulmonary health risks along the nanoclay life cycle even with increased evidence of airborne particulate exposures in occupational environments. Recently, oropharyngeal aspiration exposure to pre- and post-incinerated ONC in mice caused low grade, persistent lung inflammation with a pro-fibrotic signaling response with unknown mode(s) of action. We hypothesized that the organic coating presence and incineration status of nanoclays determine the inflammatory cytokine secretary profile and cytotoxic response of macrophages. To test this hypothesis differentiated human macrophages (THP-1) were acutely exposed (0-20 µg/cm2) to pristine, uncoated nanoclay (CloisNa), an ONC (Clois30B), their incinerated byproducts (I-CloisNa and I-Clois30B), and crystalline silica (CS) followed by cytotoxicity and inflammatory endpoints. Macrophages were co-exposed to lipopolysaccharide (LPS) or LPS-free medium to assess the role of priming the NF-κB pathway in macrophage response to nanoclay treatment. Data were compared to inflammatory responses in male C57Bl/6J mice following 30 and 300 µg/mouse aspiration exposure to the same particles.

RESULTS

In LPS-free media, CloisNa exposure caused mitochondrial depolarization while Clois30B exposure caused reduced macrophage viability, greater cytotoxicity, and significant damage-associated molecular patterns (IL-1α and ATP) release compared to CloisNa and unexposed controls. LPS priming with low CloisNa doses caused elevated cathepsin B/Caspage-1/IL-1β release while higher doses resulted in apoptosis. Clois30B exposure caused dose-dependent THP-1 cell pyroptosis evidenced by Cathepsin B and IL-1β release and Gasdermin D cleavage. Incineration ablated the cytotoxic and inflammatory effects of Clois30B while I-CloisNa still retained some mild inflammatory potential. Comparative analyses suggested that in vitro macrophage cell viability, inflammasome endpoints, and pro-inflammatory cytokine profiles significantly correlated to mouse bronchioalveolar lavage inflammation metrics including inflammatory cell recruitment.

CONCLUSIONS

Presence of organic coating and incineration status influenced inflammatory and cytotoxic responses following exposure to human macrophages. Clois30B, with a quaternary ammonium tallow coating, induced a robust cell membrane damage and pyroptosis effect which was eliminated after incineration. Conversely, incinerated nanoclay exposure primarily caused elevated inflammatory cytokine release from THP-1 cells. Collectively, pre-incinerated nanoclay displayed interaction with macrophage membrane components (molecular initiating event), increased pro-inflammatory mediators, and increased inflammatory cell recruitment (two key events) in the lung fibrosis adverse outcome pathway.

Variation in pentose phosphate pathway-associated metabolism dictates cytotoxicity outcomes determined by tetrazolium reduction assays

Tetrazolium reduction and resazurin assays are the mainstay of routine in vitro toxicity batteries. However, potentially erroneous characterization of cytotoxicity and cell proliferation can arise if verification of baseline interaction of test article with method employed is neglected. The current investigation aimed to demonstrate how interpretation of results from several standard cytotoxicity and proliferation assays vary in dependence on contributions from the pentose phosphate pathway (PPP). Non-tumorigenic Beas-2B cells were treated with graded concentrations of benzo[a]pyrene (B[a]P) for 24 and 48 h prior to cytotoxicity and proliferation assessment with commonly used MTT, MTS, WST1, and Alamar Blue assays. B[a]P caused enhanced metabolism of each dye assessed despite reductions in mitochondrial membrane potential and was reversed by 6-aminonicotinamide (6AN)-a glucose-6-phosphate dehydrogenase inhibitor. These results demonstrate differential sensitivity of standard cytotoxicity assessments on the PPP, thus (1) decoupling "mitochondrial activity" as an interpretation of cellular formazan and Alamar Blue metabolism, and (2) demonstrating the implicit requirement for investigators to sufficiently verify interaction of these methods in routine cytotoxicity and proliferation characterization. The nuances of method-specific extramitochondrial metabolism must be scrutinized to properly qualify specific endpoints employed, particularly under the circumstances of metabolic reprogramming.

Chemotherapy-induced PDL-1 expression in cancer-associated fibroblasts promotes chemoresistance in NSCLC

OBJECTIVES

A cure for cancer is out of reach for most patients due to chemoresistance. Cancer-associated fibroblasts (CAFs) play a vital role in cancer chemoresistance, but detailed understanding of the process particularly in chemoresistant lung cancer is lacking. In this study, we investigated programmed death-ligand 1 (PDL-1) as a potential biomarker for CAF-induced chemoresistance and evaluated its role and the underlying mechanisms of chemoresistance in non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

A systemic search of gene expression profiles of multiple tissues in NSCLC was carried out to determine the expression intensities of traditional fibroblast biomarkers and CAF-secreted protumorigenic cytokines. PDL-1 expression in CAFs was analyzed by ELISA, Western blotting, and flow cytometry. Human cytokine array was used to identify specific cytokines secreted from CAFs. Role of PDL-1 in NSCLC chemoresistance was assessed using CRISPR/Cas9 knockdown and various functional assays including MTT, cell invasion, sphere formation, and cell apoptosis. In vivo experiments were conducted using a co-implantation xenograft mouse model with live cell imaging and immunohistochemistry.

RESULTS

We demonstrated that chemotherapy-stimulated CAFs promoted tumorigenic and stem cell-like properties of NSCLC cells, which contribute to their chemoresistance. Subsequently, we revealed that PDL-1 expression is upregulated in chemotherapy-treated CAFs and is associated with poor prognosis. Silencing PDL-1 expression suppressed CAFs' ability to promote stem cell-like properties and invasiveness of lung cancer cells, favoring chemoresistance. Mechanistically, an upregulation of PDL-1 in chemotherapy-treated CAFs led to an increase in hepatocyte growth factor (HGF) secretion, which stimulates cancer progression, cell invasion, and stemness of lung cancer cells, while inhibiting apoptosis.

CONCLUSION

Our results show that PDL-1-positive CAFs modulate stem cell-like properties of NSCLC cells by secreting elevated HGF, thereby promoting chemoresistance. Our finding supports PDL-1 in CAFs as a chemotherapy response biomarker and as a drug delivery and therapeutic target for chemoresistant NSCLC.

SOX2Mediates Carbon Nanotube-Induced Fibrogenesis and Fibroblast Stem Cell Acquisition

Certain nanosized particles like carbon nanotubes (CNTs) are known to induce pulmonary fibrosis, but the underlying mechanisms are unclear, and efforts to prevent this disease are lacking. Fibroblast-associated stem cells (FSCs) have been suggested as a critical driver of fibrosis induced by CNTs by serving as a renewable source of extracellular matrix-producing cells; however, a detailed understanding of this process remains obscure. Here, we demonstrated that single-walled CNTs induced FSC acquisition and fibrogenic responses in primary human lung fibroblasts. This was indicated by increased expression of stem cell markers (e.g., CD44 and ABCG2) and fibrogenic markers (e.g., collagen and α-SMA) in CNT-exposed cells. These cells also showed increased sphere formation, anoikis resistance, and aldehyde dehydrogenase (ALDH) activities, which are characteristics of stem cells. Mechanistic studies revealed sex-determining region Y-box 2 (SOX2), a self-renewal associated transcription factor, as a key driver of FSC acquisition and fibrogenesis. Upregulation and colocalization of SOX2 and COL1 were found in the fibrotic lung tissues of CNT-exposed mice via oropharyngeal aspiration after 56 days. The knockdown of SOX2 by gene silencing abrogated the fibrogenic and FSC-inducing effects of CNTs. Chromatin immunoprecipitation assays identified SOX2-binding sites on COL1A1 and COL1A2, indicating SOX2 as a transcription factor in collagen synthesis. SOX2 was also found to play a critical role in TGF-β-induced fibrogenesis through its collagen- and FSC-inducing effects. Since many nanomaterials are known to induce TGF-β, our findings that SOX2 regulate FSCs and fibrogenesis may have broad implications on the fibrogenic mechanisms and treatment strategies of various nanomaterial-induced fibrotic disorders.

Abstract 3815: Cellular oxidative stress and immunological effects of carbon-based nanomaterials towards lung carcinogenicity

Lung cancer accounts for most number of cancer related death, reporting over 26.5% of all cancer deaths in United States alone. Among the risk factors, along with smoking, occupational as well as environmental exposure of carcinogens is considered as major driver of lung cancer in most cases. In that context, high aspect ratio nanomaterials (HARNs) with low density, such as carbon nanotubes (CNTs), remain efficient air-borne particulate matters during every step of their life cycle, from production to usage to disposal. Consequently, inhalation and potentially carcinogenic nanomaterial exposure to pulmonary tissues are anticipated, which may considerably facilitate lung cancer occurrence and mortality. Apart from pulmonary interaction, nanomaterial exposure via skin or oral route may play a significant role in adverse human health effects, especially when the use of nanomaterials in food and cosmetic industries are growing exponentially. CNTs are made of flat sheets of sp2 hybridized carbon atoms layered in hexagonal geometry that are rolled into unified cylindrical structures. CNTs are subdivided into single-walled (SWCNT), double-walled (DWCNT), or multi-walled carbon nanotube (MWCNT) based on the number of carbon layers in nanotubes. Size of CNTs can range from one to several nanometers in diameter and up to several micrometers in length, exhibiting a fibrous-like length-to-width (aspect) ratio similar to asbestos fibers and potentially harbor asbestos-like pulmonary fibrosis and lung cancer risks associated with their long-term exposure. Considerable efforts has been made to study Nano-toxicity but how cellular toxicological and immunological responses are affected by nanomaterial exposure is largely unknown. The present study investigated the effects of different CNT exposure on cellular proliferation, uptake, oxidative stress, DNA damage, Stem cell-like properties along with activation of cellular innate immune responses of human lung epithelial cells and immune cells to determine the underlying cross-talks. Using a physiologically relevant long-term-low-dose exposure model, we found that both single-walled and multi-walled carbon nanotubes, induced particle-specific cellular proliferation, tumor sphere formation, reactive oxygen species (ROS) and super oxide (SO), DNA-strand breaks, mitochondrial depolarization and reduced apoptosis, indicating the genotoxicity and carcinogenic potential of CNTs. We also determined distinct immune activation signature in these cells upon CNTs exposure that closely resembles “immune mediated” carcinogenesis signature as reported in “Inflammatory Cancer (C3)” subtypes. Finally, through in silico analyses and validation we have determined potential CNT exposure induced immune effectors to devise better targeted therapeutic intervention against nanomaterial exposure induced carcinogenesis.

Citation Format: Rajib Ghosh, Liying W. Rojanasakul, Yon Rojanasakul. Cellular oxidative stress and immunological effects of carbon-based nanomaterials towards lung carcinogenicity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3815.

Iron Oxide Nanoparticle-Induced Neoplastic-Like Cell Transformation in Vitro Is Reduced with a Protective Amorphous Silica Coating

Iron oxide nanoparticles (IONP) have recently surged in production and use in a wide variety of biomedical and environmental applications. However, their potential long-term health effects, including carcinogenesis, are unknown. Limited research suggests IONP can induce genotoxicity and neoplastic transformation associated with particle dissolution and release of free iron ions. "Safe by design" strategies involve the modification of particle physicochemical properties to affect subsequent adverse outcomes, such as an amorphous silica coating to reduce IONP dissolution and direct interaction with cells. We hypothesized that long-term exposure to a specific IONP (nFe₂O₃) would induce neoplastic-like cell transformation, which could be prevented with an amorphous silica coating (SiO₂-nFe₂O₃). To test this hypothesis, human bronchial epithelial cells (Beas-2B) were continuously exposed to a 0.6 μg/cm² administered a dose of nFe₂O₃ (∼0.58 μg/cm² delivered dose), SiO₂-nFe₂O₃ (∼0.55 μg/cm² delivered dose), or gas metal arc mild steel welding fumes (GMA-MS, ∼0.58 μg/cm² delivered dose) for 6.5 months. GMA-MS are composed of roughly 80% iron/iron oxide and were recently classified as a total human carcinogen. Our results showed that low-dose/long-term in vitro exposure to nFe₂O₃ induced a time-dependent neoplastic-like cell transformation, as indicated by increased cell proliferation and attachment-independent colony formation, which closely matched that induced by GMA-MS. This transformation was associated with decreases in intracellular iron, minimal changes in reactive oxygen species (ROS) production, and the induction of double-stranded DNA damage. An amorphous silica-coated but otherwise identical particle (SiO₂-nFe₂O₃) did not induce this neoplastic-like phenotype or changes in the parameters mentioned above. Overall, the presented data suggest the carcinogenic potential of long-term nFe₂O₃ exposure and the utility of an amorphous silica coating in a "safe by design" hazard reduction strategy, within the context of a physiologically relevant exposure scenario (low-dose/long-term), with model validation using GMA-MS.

Acquisition of Cancer Stem Cell-like Properties in Human Small Airway Epithelial Cells after a Long-term Exposure to Carbon Nanomaterials

Cancer stem cells (CSCs) are a key driver of tumor formation and metastasis, but how they are affected by nanomaterials is largely unknown. The present study investigated the effects of different carbon-based nanomaterials (CNMs) on neoplastic and CSC-like transformation of human small airway epithelial cells and determined the underlying mechanisms. Using a physiologically relevant exposure model (long-term/low-dose) with system validation using a human carcinogen, asbestos, we demonstrated that single-walled carbon nanotubes, multi-walled carbon nanotubes, ultrafine carbon black, and crocidolite asbestos induced particle-specific anchorage-independent colony formation, DNA-strand break, and p53 downregulation, indicating genotoxicity and carcinogenic potential of CNMs. The chronic CNM-exposed cells exhibited CSC-like properties as indicated by 3D spheroid formation, anoikis resistance, and CSC markers expression. Mechanistic studies revealed specific self-renewal and epithelial-mesenchymal transition (EMT)-related transcription factors that are involved in the cellular transformation process. Pathway analysis of gene signaling networks supports the role of SOX2 and SNAI1 signaling in CNM-mediated transformation. These findings support the potential carcinogenicity of high aspect ratio CNMs and identified molecular targets and signaling pathways that may contribute to the disease development.

Abstract 5159: Isoform specific expression of cadherin10 is associated with progression and drug resistance in non-small cell lung cancer

Lung cancer is the leading cause of cancer related death worldwide accounting for 1.69 million of total 8.8 million cancer deaths in 2015 alone. Nearly 85% of all lung cancer cases are classified as non-small cell lung cancer (NSCLC) with a 5-year survival rate of 16%, despite of all advanced targeted treatment modalities. Like any other cancer, cadherin proteins play a critical role in lung cancer progression, metastasis and drug resistance. Classical type I and type II cadherin proteins are calcium-dependent transmembrane glycoproteins with a cytoplasmic tail that mediates downstream signaling and a large extracellular N-terminal head that engages in homophilic and heterophilic adhesion. While alterations of type I cadherins (N-cadherin and E-cadherin) are well studied, functions as well as alterations of type II cadherins, such as cadherin-8, -9, -10, -12, and -18, remain largely unknown. Recent whole genome sequencing of patient samples towards Precision Medicine initiatives revealed 2,687 donors affected by 9,151 cadherin10 (CDH10) mutations alone across the 63 cancer projects worldwide. The majority of mutations in CDH10 are missense substitutions largely distributed throughout the entire gene length, without any specific hotspot. CDH10 copy number amplification is also reported in a significantly large number of lung cancer patients. Alternative splicing of this gene potentially results in multiple transcript variants. To resolve the conundrum of Loss-of-heterozygosity (LOH) and copy number amplification, we decided to look further in to expression and function of CDH10 using array of lung cancer cell lines and human lung cancer patient samples. Here we report, for the first time, that full-length CDH10 expression as well as the tumor suppressive function are compromised in the course of NSCLC development, while aberrant smaller isoforms appear in the cell lines and tumors that drive the oncogenic progression. Expression of such smaller isoforms were further altered when the cells were treated with commonly used chemotherapy drugs, such as Cisplatin, Doxorubicin and Paclitaxel indicating a direct relationship between drug resistance and appearance of these smaller isoforms. We found that the downregulation of full-length CDH10 using siRNA results in an increase in proliferation and invasion, indicating a potential anti-oncogenic function of full-length CDH10 protein. Therefore, we found that mutations and alternative splicing potentially downregulates full-length CDH10 expression along with its tumor suppressive function. However, appearance of smaller aberrant isoforms accounts for tumorigenic progression and drug resistance.

Citation Format: Rajib Ghosh, Phattrakorn Powan, Liying W. Rojanasakul, Yon Rojanasakul. Isoform specific expression of cadherin10 is associated with progression and drug resistance in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5159.

Predicting Nanotube Fibrogenicity through Stem Cell-Mediated Fibroblast Focus and Spheroid Formation

Fibroblast stem cells or stemlike cells (FSCs) are proposed to play a pivotal role in extracellular matrix (ECM) regeneration by serving as a key source of ECM-producing fibroblasts. We developed a mechanism-based in vitro model for fibrogenicity testing of nanomaterials based on their ability to induce FSCs. Using a FSC-enriched fibroblast focus model to mimic in vivo fibrogenic response, we demonstrated a dose-dependent increase in fibroblast focus formation and collagen production by primary lung fibroblasts treated with multiwalled carbon nanotubes (MWCNTs). The focus-forming cells exhibited stem properties as indicated by stem cell markers expression, sphere formation, and ALDH activity assays. Inhibition of ALDH activity diminished the focus and sphere formation as well as collagen production. In vivo animal studies supported the in vitro findings and indicated the potential utility of FSC-based assays as a rapid screening tool for fibrogenicity testing of nanomaterials. This study also unveils a novel mechanism of nanotube-induced fibrogenesis through ALDH-dependent FSC activation.