Non-small cell lung cancer stem/progenitor cells are enriched in multiple distinct phenotypic subpopulations and exhibit plasticity. Cell Death Dis. 2012;3:e352. [PMID: 22825470 PMCID: PMC3406592 DOI: 10.1038/cddis.2012.93]

EMT induces characteristic changes of Rho GTPases and downstream effectors with a mitosis-specific twist

Epithelial-mesenchymal transition (EMT) is a key cellular transformation for many physiological and pathological processes ranging from cancer over wound healing to embryogenesis. Changes in cell migration, cell morphology and cellular contractility were identified as hallmarks of EMT. These cellular properties are known to be tightly regulated by the actin cytoskeleton. EMT-induced changes of actin-cytoskeletal regulation were demonstrated by previous reports of changes of actin cortex mechanics in conjunction with modifications of cortex-associated f-actin and myosin. However, at the current state, the changes of upstream actomyosin signaling that lead to corresponding mechanical and compositional changes of the cortex are not well understood. In this work, we show in breast epithelial cancer cells MCF-7 that EMT results in characteristic changes of the cortical association of Rho-GTPases Rac1, RhoA and RhoC and downstream actin regulators cofilin, mDia1 and Arp2/3. In the light of our findings, we propose that EMT-induced changes in cortical mechanics rely on two hitherto unappreciated signaling paths-i) an interaction between Rac1 and RhoC and ii) an inhibitory effect of Arp2/3 activity on cortical association of myosin II.

Immunotherapy and targeted therapy for lung cancer: Current status and future perspectives

Lung cancer has the highest incidence of morbidity and mortality throughout the globe. A large number of patients are diagnosed with lung cancer at the later stages of the disease. This eliminates surgery as an option and places complete dependence on radiotherapy or chemotherapy, and/or a combination of both, to halt disease progression by targeting the tumor cells. Unfortunately, these therapies have rarely proved to be effective, and this necessitates the search for alternative preventive approaches to reduce the mortality rate of lung cancer. One of the effective therapies against lung cancer comprises targeting the tumor microenvironment. Like any other cancer cells, lung cancer cells tend to use multiple pathways to maintain their survival and suppress different immune responses from the host's body. This review comprehensively covers the role and the mechanisms that involve the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in lung adenocarcinoma and methods of treating it by altering the tumor microenvironment. It focuses on the insight and understanding of the lung cancer tumor microenvironment and chemokines, cytokines, and activating molecules that take part in angiogenesis and metastasis. The review paper accounts for the novel and current immunotherapy and targeted therapy available for lung cancer in clinical trials and in the research phases in depth. Special attention is being paid to mark out single or multiple genes that are required for malignancy and survival while developing targeted therapies for lung cancer treatment.

Hepatoblastoma Cancer Stem Cells Express PD-L1, Reveal Plasticity and Can Emerge upon Chemotherapy

The biology of cancer stem cells (CSCs) of pediatric cancers, such as hepatoblastoma, is sparsely explored. This is mainly due to the very immature nature of these tumors, which complicates the distinction of CSCs from the other tumor cells. Previously, we identified a CSC population in hepatoblastoma cell lines expressing the CSC markers CD34 and CD90, cell surface Vimentin (csVimentin) and binding of OV-6. In this study, we detected the co-expression of the immune escape factor PD-L1 in the CSC population, whereas the other tumor cells remained negative. FACS data revealed that non-CSCs give rise to CSCs, reflecting plasticity of CSCs and non-CSCs in hepatoblastoma as seen in other tumors. When we treated cells with cisplatin and decitabine, a new CD34^+/lowOV-6^lowCD90⁺ population emerged that lacked csVimentin and PD-L1 expression. Expression analyses showed that this new CSC subset shared similar pluripotency and EMT features with the already-known CSCs. FACS results further revealed that this subset is also generated from non-CSCs. In conclusion, we showed that hepatoblastoma CSCs express PD-L1 and that the biology of hepatoblastoma CSCs is of a plastic nature. Chemotherapeutic treatment leads to another CSC subset, which is highly chemoresistant and could be responsible for a poor prognosis after postoperative chemotherapy.

ERK inactivation enhances stemness of NSCLC cells via promoting Slug-mediated epithelial-to-mesenchymal transition

Rationale: The mitogen-activated protein kinase pathway (MAPK) is one of the major cancer-driving pathways found in non-small cell lung cancer (NSCLC) patients. ERK inhibitors (ERKi) have been shown to be effective in NSCLC patients with MAPK pathway mutations. However, like other MAPK inhibitors, ERKi rarely confers complete and durable responses. The mechanism of tumor relapse after ERKi treatment is yet defined. Methods: To best study the mechanism of tumor relapse after ERK inhibitor treatment in NSCLC patients, we treated various NSCLC cell lines and patient-derived xenograft (PDX) with ERK inhibitors and evaluated the enrichment of cancer stem cell (CSC) population. We then performed a Next-generation sequencing (NGS) to identify potential pathways that are responsible for the CSC enrichment. Further, the involvement of specific pathways was examined using molecular and cellular methods. Finally, we investigated the therapeutic benefits of ERKi treatment combined with JAK/STAT pathway inhibitor using cellular and xenograft NSCLC models. Results: We found that ERKi treatment expands the CSC population in NSCLC cells through enhanced epithelial-to-mesenchymal transition (EMT)-mediated cancer cell dedifferentiation. Mechanistically, ERK inactivation induces EMT via pSTAT3-mediated upregulation of Slug, in which, upregulation of miR-204 and downregulation of SPDEF, a transcription repressor of Slug, are involved. Finally, the JAK/STAT pathway inhibitor Ruxolitinib blocks the ERK inactivation-induced EMT and CSC expansion, as well as the tumor progression in xenograft models after ERKi treatment. Conclusions: This study revealed a potential tumor relapse mechanism of NSCLC after ERK inhibition through the unintended activation of the EMT program, ascertained the pSTAT-miR-204-SPDEF-Slug axis, and provided a promising combination inhibitor approach to prevent tumor relapse in patients.

A Comprehensive Bioinformatic Analysis for Identification of Myeloid-Associated Differentiation Marker as a Potential Negative Prognostic Biomarker in Non-Small-Cell Lung Cancer

Objectives: This study aimed to identify a molecular marker associated with the prognosis of non-small-cell lung cancer (NSCLC).

Materials and Methods: The RNA sequencing data and clinical information of NSCLC patients were obtained from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO). The weighted gene co-expression network analysis (WGCNA) was used to identify the co-expression gene modules and differentially expressed genes (DEGs) by comparing gene expression between NSCLC tumor tissues and normal tissues. Subsequently, the functional enrichment analysis of the DEGs was performed. Kaplan-Meier survival analysis and the GEPIA2 online tool were performed to investigate the relationship between the expression of these genes of interest and the survival of NSCLC patients, and to validate one most survival-relevent hub gene, as well as validated the hub gene using independent datasets from the GEO database. Further analysis was carried out to characterize the relationship between the hub gene and tumor immune cell infiltration, tumor mutation burden (TMB), microsatellite instability (MSI), and other known biomarkers of lung cancer. The related genes were screened by analyzing the protein-protein interaction (PPI) network and the survival model was constructed. GEPIA2 was applied in the potential analysis of pan-cancer biomarker of hub gene.

Results: 57 hub genes were found to be involved in intercellular connectivity from the 779 identified differentially co-expressed genes. Myeloid-associated differentiation marker (MYADM) was strongly associated with overall survival (OS) and disease-free survival (DFS) of NSCLC patients, and high MYADM expression was associated with poor prognosis. Thus, MYADM was identified as a risk factor. Additionally, MYADM was validated as a survival risk factor in NSCLC patients in two independent datasets. Further analysis showed that MYADM was nagetively associated with TMB, and was positively correlated with macrophages, neutrophils, and dendritic cells, suggesting its role in regulating tumor immunity. The MYADM expression differed across many types of cancer and had the potential to serve as a pan-cancer marker.

Conclusion:MYADM is an independent prognostic factor for NSCLC patients, which can predict the progression of cancer and play a role in the tumor immune cell infiltration in NSCLC.

Multicellular Effects of STAT3 in Non-small Cell Lung Cancer: Mechanistic Insights and Therapeutic Opportunities

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and accounts for 85% of lung cancer cases. Aberrant activation of the Signal Transducer and Activator of Transcription 3 (STAT3) is frequently observed in NSCLC and is associated with a poor prognosis. Pre-clinical studies have revealed an unequivocal role for tumor cell-intrinsic and extrinsic STAT3 signaling in NSCLC by promoting angiogenesis, cell survival, cancer cell stemness, drug resistance, and evasion of anti-tumor immunity. Several STAT3-targeting strategies have also been investigated in pre-clinical models, and include preventing upstream receptor/ligand interactions, promoting the degradation of STAT3 mRNA, and interfering with STAT3 DNA binding. In this review, we discuss the molecular and immunological mechanisms by which persistent STAT3 activation promotes NSCLC development, and the utility of STAT3 as a prognostic and predictive biomarker in NSCLC. We also provide a comprehensive update of STAT3-targeting therapies that are currently undergoing clinical evaluation, and discuss the challenges associated with these treatment modalities in human patients.

Potential of Stem Cells and CART as a Potential Polytherapy for Small Cell Lung Cancer

Despite the increasing urgency of the problem of treating small cell lung cancer (SCLC), information on the causes of its development is fragmentary. There is no complete understanding of the features of antitumor immunity and the role of the microenvironment in the development of SCLC resistance. This impedes the development of new methods for the diagnosis and treatment of SCLC. Lung cancer and chronic obstructive pulmonary disease (COPD) have common pathogenetic factors. COPD is a risk factor for lung cancer including SCLC. Therefore, the search for effective approaches to prevention, diagnosis, and treatment of SCLC in patients with COPD is an urgent task. This review provides information on the etiology and pathogenesis of SCLC, analyses the effectiveness of current treatment options, and critically evaluates the potential of chimeric antigen receptor T cells therapy (CART therapy) in SCLC. Moreover, we discuss potential links between lung cancer and COPD and the role of endothelium in the development of COPD. Finally, we propose a new approach for increasing the efficacy of CART therapy in SCLC.

Cannabidiol Induces Cell Death in Human Lung Cancer Cells and Cancer Stem Cells

Currently, there is no effective therapy against lung cancer due to the development of resistance. Resistance contributes to disease progression, recurrence, and mortality. The presence of so-called cancer stem cells could explain the ineffectiveness of conventional treatment, and the development of successful cancer treatment depends on the targeting also of cancer stem cells. Cannabidiol (CBD) is a cannabinoid with anti-tumor properties. However, the effects on cancer stem cells are not well understood. The effects of CBD were evaluated in spheres enriched in lung cancer stem cells and adherent lung cancer cells. We found that CBD decreased viability and induced cell death in both cell populations. Furthermore, we found that CBD activated the effector caspases 3/7, increased the expression of pro-apoptotic proteins, increased the levels of reactive oxygen species, as well as a leading to a loss of mitochondrial membrane potential in both populations. We also found that CBD decreased self-renewal, a hallmark of cancer stem cells. Overall, our results suggest that CBD is effective against the otherwise treatment-resistant cancer stem cells and joins a growing list of compounds effective against cancer stem cells. The effects and mechanisms of CBD in cancer stem cells should be further explored to find their Achilles heel.

Activation of a Ductal-to-Endocrine Transdifferentiation Transcriptional Program in the Pancreatic Cancer Cell Line PANC-1 Is Controlled by RAC1 and RAC1b through Antagonistic Regulation of Stemness Factors

Simple Summary

For patients with metastatic pancreatic ductal adenocarcinoma (PDAC) there is currently no cure; hence, novel effective therapies are desperately needed. Among PDAC patients, the tumor cell phenotypes are heterogeneous as a result of epithelial–mesenchymal transition, a process that endows them with the ability to metastasize, resist therapy, and generate cancer stem cells. The heightened plasticity of quasimesenchymal and potentially metastatic tumor cells may, however, also be exploited for their transdifferentiation into benign, highly differentiated or post-mitotic cells. Since PDAC patients often have a need for replacement of insulin-producing cells, conversion of tumor cells with a ductal/exocrine origin to endocrine β cell-like cells is an attractive therapeutic option. Successful transdifferentiation into insulin-producing cells has been reported for the quasimesenchymal cell line PANC-1; however, the mechanistic basis of this transformation process is unknown. Here, we show that the small GTPases, RAC1 and RAC1b control this process by antagonistic regulation of stemness genes.

Abstract

Epithelial–mesenchymal transition (EMT) is a driving force for tumor growth, metastatic spread, therapy resistance, and the generation of cancer stem cells (CSCs). However, the regained stem cell character may also be exploited for therapeutic conversion of aggressive tumor cells to benign, highly differentiated cells. The PDAC-derived quasimesenchymal-type cell lines PANC-1 and MIA PaCa-2 have been successfully transdifferentiated to endocrine precursors or insulin-producing cells; however, the underlying mechanism of this increased plasticity remains elusive. Given its crucial role in normal pancreatic endocrine development and tumor progression, both of which involve EMT, we analyzed here the role of the small GTPase RAC1. Ectopic expression in PANC-1 cells of dominant negative or constitutively active mutants of RAC1 activation blocked or enhanced, respectively, the cytokine-induced activation of a ductal-to-endocrine transdifferentiation transcriptional program (deTDtP) as revealed by induction of the NEUROG3, INS, SLC2A2, and MAFA genes. Conversely, ectopic expression of RAC1b, a RAC1 splice isoform and functional antagonist of RAC1-driven EMT, decreased the deTDtP, while genetic knockout of RAC1b dramatically increased it. We further show that inhibition of RAC1 activation attenuated pluripotency marker expression and self-renewal ability, while depletion of RAC1b dramatically enhanced stemness features and clonogenic potential. Finally, rescue experiments involving pharmacological or RNA interference-mediated inhibition of RAC1 or RAC1b, respectively, confirmed that both RAC1 isoforms control the deTDtP in an opposite manner. We conclude that RAC1 and RAC1b antagonistically control growth factor-induced activation of an endocrine transcriptional program and the generation of CSCs in quasimesenchymal PDAC cells. Our results have clinical implications for PDAC patients, who in addition to eradication of tumor cells have a need for replacement of insulin-producing cells.

Polycaprolactone Electrospun Scaffolds Produce an Enrichment of Lung Cancer Stem Cells in Sensitive and Resistant EGFRm Lung Adenocarcinoma

Simple Summary

The culture of lung cancer stem cells (LCSCs) is not possible using traditional flat polystyrene surfaces. The study of these tumor-initiating cells is fundamental due to their key role in the resistance to anticancer therapies, tumor recurrence, and metastasis. Hence, we evaluated the use of polycaprolactone electrospun (PCL-ES) scaffolds for culturing LCSC population in sensitive and resistant EGFR-mutated lung adenocarcinoma models. Our findings revealed that both cell models seeded on PCL-ES structures showed a higher drug resistance, enhanced levels of several genes and proteins related to epithelial-to-mesenchymal process, stemness, and surface markers, and the activation of the Hedgehog pathway. We also determined that the non-expression of CD133 was associated with a low degree of histological differentiation, disease progression, distant metastasis, and worse overall survival in EGFR-mutated non-small cell lung cancer patients. Therefore, we confirmed PCL-ES scaffolds as a suitable three-dimensional cell culture model for the study of LCSC niche.

Abstract

The establishment of a three-dimensional (3D) cell culture model for lung cancer stem cells (LCSCs) is needed because the study of these stem cells is unable to be done using flat surfaces. The study of LCSCs is fundamental due to their key role in drug resistance, tumor recurrence, and metastasis. Hence, the purpose of this work is the evaluation of polycaprolactone electrospun (PCL-ES) scaffolds for culturing LCSCs in sensitive and resistant EGFR-mutated (EGFRm) lung adenocarcinoma cell models. We performed a thermal, physical, and biological characterization of 10% and 15%-PCL-ES structures. Several genes and proteins associated with LCSC features were analyzed by RT-qPCR and Western blot. Vimentin and CD133 tumor expression were evaluated in samples from 36 patients with EGFRm non-small cell lung cancer through immunohistochemistry. Our findings revealed that PC9 and PC9-GR3 models cultured on PCL-ES scaffolds showed higher resistance to osimertinib, upregulation of ABCB1, Vimentin, Snail, Twist, Sox2, Oct-4, and CD166, downregulation of E-cadherin and CD133, and the activation of Hedgehog pathway. Additionally, we determined that the non-expression of CD133 was significantly associated with a low degree of histological differentiation, disease progression, and distant metastasis. To sum up, we confirmed PCL-ES scaffolds as a suitable 3D cell culture model for the study of the LCSC niche.

Alternative models of cancer stem cells: The stemness phenotype model, 10 years later

The classical cancer stem cell (CSCs) theory proposed the existence of a rare but constant subpopulation of CSCs. In this model cancer cells are organized hierarchically and are responsible for tumor resistance and tumor relapse. Thus, eliminating CSCs will eventually lead to cure of cancer. This simplistic model has been challenged by experimental data. In 2010 we proposed a novel and controversial alternative model of CSC biology (the Stemness Phenotype Model, SPM). The SPM proposed a non-hierarchical model of cancer biology in which there is no specific subpopulation of CSCs in tumors. Instead, cancer cells are highly plastic in term of stemness and CSCs and non-CSCs can interconvert into each other depending on the microenvironment. This model predicts the existence of cancer cells ranging from a pure CSC phenotype to pure non-CSC phenotype and that survival of a single cell can originate a new tumor. During the past 10 years, a plethora of experimental evidence in a variety of cancer types has shown that cancer cells are indeed extremely plastic and able to interconvert into cells with different stemness phenotype. In this review we will (1) briefly describe the cumulative evidence from our laboratory and others supporting the SPM; (2) the implications of the SPM in translational oncology; and (3) discuss potential strategies to develop more effective therapeutic regimens for cancer treatment.

Rac1, A Potential Target for Tumor Therapy

RAS-related C3 botulinum toxin substrate 1 (Rac.1) is one of the important members of Rho GTPases. It is well known that Rac1 is a cytoskeleton regulation protein that regulates cell adhesion, morphology, and movement. Rac1 is highly expressed in different types of tumors, which is related to poor prognosis. Studies have shown that Rac1 not only participates in the tumor cell cycle, apoptosis, proliferation, invasion, migration and angiogenesis, but also participates in the regulation of tumor stem cell, thus promoting the occurrence of tumors. Rac1 also plays a key role in anti-tumor therapy and participates in immune escape mediated by the tumor microenvironment. In addition, the good prospects of Rac1 inhibitors in cancer prevention and treatment are exciting. Therefore, Rac1 is considered as a potential target for the prevention and treatment of cancer. The necessity and importance of Rac1 are obvious, but it still needs further study.

Control of Intestinal Epithelial Permeability by Lysophosphatidic Acid Receptor 5

BACKGROUND & AIMS

Epithelial cells form a monolayer at mucosal surface that functions as a highly selective barrier. Lysophosphatidic acid (LPA) is a bioactive lipid that elicits a broad range of biological effects via cognate G protein-coupled receptors. LPA receptor 5 (LPA₅) is highly expressed in intestinal epithelial cells, but its role in the intestine is not well-known. Here we determined the role of LPA₅ in regulation of intestinal epithelial barrier.

METHODS

Epithelial barrier integrity was determined in mice with intestinal epithelial cell (IEC)-specific LPA₅ deletion, Lpar5^ΔIEC. LPA was orally administered to mice, and intestinal permeability was measured. Dextran sulfate sodium (DSS) was used to induce colitis. Human colonic epithelial cell lines were used to determine the LPA₅-mediated signaling pathways that regulate epithelial barrier.

RESULTS

We observed increased epithelial permeability in Lpar5^ΔIEC mice with reduced claudin-4 expression. Oral administration of LPA decreased intestinal permeability in wild-type mice, but the effect was greatly mitigated in Lpar5^ΔIEC mice. Serum lipopolysaccharide level and bacterial loads in the intestine and liver were elevated in Lpar5^ΔIEC mice. Lpar5^ΔIEC mice developed more severe colitis induced with DSS. LPA₅ transcriptionally regulated claudin-4, and this regulation was dependent on transactivation of the epidermal growth factor receptor, which induced localization of Rac1 at the cell membrane. LPA induced the translocation of Stat3 to the cell membrane and promoted the interaction between Rac1 and Stat3. Inhibition of Stat3 ablated LPA-mediated regulation of claudin-4.

CONCLUSIONS

This study identifies LPA₅ as a regulator of the intestinal barrier. LPA₅ promotes claudin-4 expression in IECs through activation of Rac1 and Stat3.

Persistent effects of pair bonding in lung cancer cell growth in monogamous Peromyscus californicus

Epidemiological evidence suggests that social interactions and especially bonding between couples influence tumorigenesis, yet whether this is due to lifestyle changes, homogamy (likelihood of individuals to marry people of similar health), or directly associated with host-induced effects in tumors remains debatable. In the present study, we explored if tumorigenesis is associated with the bonding experience in monogamous rodents at which disruption of pair bonds is linked to anxiety and stress. Comparison of lung cancer cell spheroids that formed in the presence of sera from bonded and bond-disrupted deer mice showed that in monogamous Peromyscus polionotus and Peromyscus californicus, but not in polygamous Peromyscus maniculatus, the disruption of pair bonds altered the size and morphology of spheroids in a manner that is consistent with the acquisition of increased oncogenic potential. In vivo, consecutive transplantation of human lung cancer cells between P. californicus, differing in bonding experiences (n = 9 for bonded and n = 7 for bond-disrupted), and nude mice showed that bonding suppressed tumorigenicity in nude mice (p<0.05), suggesting that the protective effects of pair bonds persisted even after bonding ceased. Unsupervised hierarchical clustering indicated that the transcriptomes of lung cancer cells clustered according to the serum donors' bonding history while differential gene expression analysis pointed to changes in cell adhesion and migration. The results highlight the pro-oncogenic effects of pair-bond disruption, point to the acquisition of expression signatures in cancer cells that are relevant to the bonding experiences of serum donors, and question the ability of conventional mouse models to capture the whole spectrum of the impact of the host in tumorigenesis.

EMT-Induced Cell-Mechanical Changes Enhance Mitotic Rounding Strength

To undergo mitosis successfully, most animal cells need to acquire a round shape to provide space for the mitotic spindle. This mitotic rounding relies on mechanical deformation of surrounding tissue and is driven by forces emanating from actomyosin contractility. Cancer cells are able to maintain successful mitosis in mechanically challenging environments such as the increasingly crowded environment of a growing tumor, thus, suggesting an enhanced ability of mitotic rounding in cancer. Here, it is shown that the epithelial-mesenchymal transition (EMT), a hallmark of cancer progression and metastasis, gives rise to cell-mechanical changes in breast epithelial cells. These changes are opposite in interphase and mitosis and correspond to an enhanced mitotic rounding strength. Furthermore, it is shown that cell-mechanical changes correlate with a strong EMT-induced change in the activity of Rho GTPases RhoA and Rac1. Accordingly, it is found that Rac1 inhibition rescues the EMT-induced cortex-mechanical phenotype. The findings hint at a new role of EMT in successful mitotic rounding and division in mechanically confined environments such as a growing tumor.

Electrical Impedance Spectroscopy for Monitoring Chemoresistance of Cancer Cells

Electrical impedance spectroscopy (EIS) is an electrokinetic method that allows for the characterization of intrinsic dielectric properties of cells. EIS has emerged in the last decade as a promising method for the characterization of cancerous cells, providing information on inductance, capacitance, and impedance of cells. The individual cell behavior can be quantified using its characteristic phase angle, amplitude, and frequency measurements obtained by fitting the input frequency-dependent cellular response to a resistor-capacitor circuit model. These electrical properties will provide important information about unique biomarkers related to the behavior of these cancerous cells, especially monitoring their chemoresistivity and sensitivity to chemotherapeutics. There are currently few methods to assess drug resistant cancer cells, and therefore it is difficult to identify and eliminate drug-resistant cancer cells found in static and metastatic tumors. Establishing techniques for the real-time monitoring of changes in cancer cell phenotypes is, therefore, important for understanding cancer cell dynamics and their plastic properties. EIS can be used to monitor these changes. In this review, we will cover the theory behind EIS, other impedance techniques, and how EIS can be used to monitor cell behavior and phenotype changes within cancerous cells.

Cancer Stem Cells-Origins and Biomarkers: Perspectives for Targeted Personalized Therapies

The use of biomarkers in diagnosis, therapy and prognosis has gained increasing interest over the last decades. In particular, the analysis of biomarkers in cancer patients within the pre- and post-therapeutic period is required to identify several types of cells, which carry a risk for a disease progression and subsequent post-therapeutic relapse. Cancer stem cells (CSCs) are a subpopulation of tumor cells that can drive tumor initiation and can cause relapses. At the time point of tumor initiation, CSCs originate from either differentiated cells or adult tissue resident stem cells. Due to their importance, several biomarkers that characterize CSCs have been identified and correlated to diagnosis, therapy and prognosis. However, CSCs have been shown to display a high plasticity, which changes their phenotypic and functional appearance. Such changes are induced by chemo- and radiotherapeutics as well as senescent tumor cells, which cause alterations in the tumor microenvironment. Induction of senescence causes tumor shrinkage by modulating an anti-tumorigenic environment in which tumor cells undergo growth arrest and immune cells are attracted. Besides these positive effects after therapy, senescence can also have negative effects displayed post-therapeutically. These unfavorable effects can directly promote cancer stemness by increasing CSC plasticity phenotypes, by activating stemness pathways in non-CSCs, as well as by promoting senescence escape and subsequent activation of stemness pathways. At the end, all these effects can lead to tumor relapse and metastasis. This review provides an overview of the most frequently used CSC markers and their implementation as biomarkers by focussing on deadliest solid (lung, stomach, liver, breast and colorectal cancers) and hematological (acute myeloid leukemia, chronic myeloid leukemia) cancers. Furthermore, it gives examples on how the CSC markers might be influenced by therapeutics, such as chemo- and radiotherapy, and the tumor microenvironment. It points out, that it is crucial to identify and monitor residual CSCs, senescent tumor cells, and the pro-tumorigenic senescence-associated secretory phenotype in a therapy follow-up using specific biomarkers. As a future perspective, a targeted immune-mediated strategy using chimeric antigen receptor based approaches for the removal of remaining chemotherapy-resistant cells as well as CSCs in a personalized therapeutic approach are discussed.

All-trans retinoic acid reduces cancer stem cell-like cell-mediated resistance to gefitinib in NSCLC adenocarcinoma cells

Background

The enrichment of cancer stem cell-like cells (CSCs) has been considered to be responsible for tumor progression after an initial response to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs) in patients with non-small cell lung adenocarcinoma (NSCLC/ADC). CSCs with ALDH1A1^bright /CD44^high expression contribute to the TKIs resistance in NSCLC/ADC cells. All-trans retinoic acid (ATRA) has been shown to be a potential targeted therapy against CSCs due to its ability to inhibit ALDH1A1 activity. We therefore investigated whether ATRA could circumvent the resistance to improve the response to gefitinib in NSCLC/ADC cells.

Methods

Treatment of NSCLC/ADC A549 and H1650 cells with gefitinib enriched the gefitinib surviving cells (GSCs). The expression of ALDH1A1 and CD44 and the IC50 values for gefitinib were determined by flow cytometry (FCM) and crystal violet assay in GSCs and ATRA-treated GSCs, respectively. Using DEAB as the positive control, direct inhibitory effect of ATRA on ALDH1A1 activity was determined by ALDEFLUOR assay,

Results

GSCs showed higher expression of ALDH1A1 and CD44 and IC50 values for gefitinib than their respective parental cells, suggesting that gefitinib can lead to propagation of CSC-enriched gefitinib-resistant cells. Treatment with ATRA was found to significantly reduce the increased expression of ALDH1A1 and CD44 and the IC50 values for gefitinib in A549GSC and H1650GSC cells, and ATRA could directly inhibit active ALDH1A1 as compared to DEAB.

Conclusion

Our findings suggest that combination treatment with ATRA prevents gefitinib-induced enrichment of ALDH1A1^bright/CD44^high CSCs and enhances gefitinib-induced growth inhibition of NSCLC/ADC cells.

Autophagy inhibition of cancer stem cells promotes the efficacy of cisplatin against non-small cell lung carcinoma

Background:

Clinical treatment of non-small cell lung carcinoma (NSCLC) by cisplatin eventually results in drug resistance, which cancer stem cells and autophagy are believed to be involved in. In the present study, we aimed to explore the effect of autophagy-inhibited cancer stem cells in NSCLC.

Methods:

Cancer stem cells were identified by CD133 expression levels detected by immunochemistry, real-time polymerase chain reaction, western blot, and flow cytometry. Stemness was detected by sphere-forming assays of tumor cells. Autophagy was determined by LC3-II expression at mRNA and protein levels. The effect of chloroquine (CQ) on autophagy was detected by real-time polymerase chain reaction, western blot and sphere-forming assay in vitro, and tumor growth in male NOD/SCID mice.

Results:

Cisplatin (CDDP) treatment enhanced CD133⁺ cell ratios in clinical NSCLC specimens and NSCLC cell line A549. The CD133⁺ cells enriched by CDDP exhibited higher autophagy levels. Autophagy inhibition by CQ inhibited CD133⁺ stemness and promoted CDDP efficiency in A549 cells. In addition, the combination of CDDP and CQ treatment significantly inhibited autophagy levels and cancer stem cell proportions in vitro, and dramatically suppressed tumor growth compared with individual agents.

Conclusion:

Autophagy inhibition of cancer stem cells could promote the efficacy of cisplatin against NSCLC.

Targeted destruction of cancer stem cells using multifunctional magnetic nanoparticles that enable combined hyperthermia and chemotherapy

Cancer stem cells (CSCs) have been implicated in cancer recurrence and therapy resistance. Therefore, a CSC-targeted therapy that disrupts the maintenance and survival of CSCs may offer an effective approach in killing tumor cells in primary tumors and preventing the metastasis caused by CSCs. Nanoparticles (NPs)-based thermotherapy and/or chemotherapy are promising therapeutic methods for cancer treatment. Methods: A silica-based multifunctional NP system was present, which encapsulated a chemotherapeutic agent and magnetic cores and coated with a specific antibody against the lung CSCs. The efficacy of this novel therapeutic strategy was systematically studied both in vitro and in vivo by simultaneous activating the combined thermotherapy and chemotherapy via CSC-targeted NPs. Results: These NPs were systematically administered and activated for targeted chemotherapy and thermotherapy by using an externally applied alternating magnetic field (AMF). The antibody-modified NPs targeted to lung CSCs with enhanced cellular uptake in vitro and extended accumulation in tumor in vivo. Up to 98% of lung CSCs was killed in vitro with 30-min application of AMF, due to the combined effects of hyperthermia and chemotherapeutic drug treatment. In in vivo models, this combined therapy significantly suppressed tumor growth and metastasis in lung CSC xenograft-bearing mice, with minimal side effects and adverse effects. Conclusion: With good biocompatibility and targeting capability, the nanodrug delivery system may offer a promising clinical platform for the combined thermotherapy and chemotherapy. This work demonstrated the feasibility of developing multifunctional nanomedicine targeting CSCs for effective cancer treatment.

Amino Acid-Mediated Metabolism: A New Power to Influence Properties of Stem Cells

The self-renewal and differentiation potentials of stem cells are dependent on amino acid (AA) metabolism. We review the literature on the metabolic preference of both cancer and noncancer stem cells. The balance in AA metabolism is responsible for maintaining the functionality of noncancer stem cells, and altering the levels of AAs can influence the malignant biological behavior of cancer stem cells. AAs are considered nutrients participating in metabolism and playing a critical role in maintaining the activity of normal stem cells and the effect of therapy of cancer stem cells. Targeting AA metabolism helps inhibit the stemness of cancer stem cells and remodels the function of normal stem cells. This review summarizes the metabolic characteristics and regulation pathways of AA in different stem cells, not only from the nutritional perspective but also from the genomic perspective that have been reported in the recent five years. In addition, we briefly survey new therapeutic modalities that may help eradicate cancer stem cells by exploiting nutrient deprivation. Understanding AA uptake characteristics helps researchers define the preference for AA in different stem cells and enables clinicians make timely interventions to specifically target the cell behavior.

A bidirectional effect of Rac1 inhibition-Protects radiation-induced intestinal injury while inhibits tumor

AIMS

To investigate whether Rac1 inhibition can alleviate radiation-induced intestinal injury (RIII), meanwhile exist no protection on tumors.

MATERIALS AND METHODS

Rac1 inhibition was achieved by its specific inhibitor, NSC23766. Mice were pretreated with different intraperitoneal injections, which were normal saline for NS group (N = 9), and 2.5 mg/kg and 5 mg/kg of NSC23766 for Low-Dose group (N = 9) and High-Dose group (N = 9), respectively. After total body irritation (10Gy), small intestinal tissues were collected for Hematoxylin-Eosin (H&E) staining and Terminal-deoxynucleotidyl Transferase Mediated dUTP Nick End Labeling (TUNEL). Intestinal epithelial and tumor cell lines, namely MODE-k and CT-26, were used to further study the role of Rac1 inhibition on radiation damage. Flow cytometry was used to detect changes in reactive oxygen species production, cell cycles and mitochondrial membrane potential, the latter was also checked by fluorescence microscope. Changes of protein-expression associated with apoptosis and cell cycles were detected by Western blotting to explain the possible molecular mechanism.

KEY FINDINGS

Height of intestine villi and depth of crypt were higher (P < 0.01) and apoptosis ratio lower (P < 0.01) in High-Dose group compared with those in NS group. After radiation, Rac1 inhibition pre-treatment improved the vitality (P < 0.01) and reduced the apoptosis (P < 0.01) in MODE-k while yielded opposite results in CT-26, and reduced ROS production of MODE-k (P < 0.01) while had little effect on that of CT-26. Rac1 inhibition differently affected the cell cycles of normal cells and that of tumor cells.

SIGNIFICANCE

Inhibition of Rac1 could alleviate RIII, meanwhile assist the killing effect of radiation on tumor cells.

Protective autophagy decreases osimertinib cytotoxicity through regulation of stem cell-like properties in lung cancer

Osimertinib, a third-generation epidermal growth factor receptor - tyrosine kinase inhibitor (EGFR-TKI), shows great efficacy in EGFR-mutant non-small cell lung cancer (NSCLC); however, the resistance is inevitable. Osimertinib induces autophagy in NSCLC cells, but the role of autophagy in osimertinib resistance is not clear. We discovered that enhanced autophagy is associated with osimertinib resistance in vitro and in vivo. Inhibition of autophagy enhanced osimertinib cytotoxicity in both osimertinib-resistant and sensitive cells. Moreover, osimertinib-resistant cells exhibited stem cell-like properties, whereas autophagy inhibition decreased the stemness by downregulating the expression of SOX2 and ALDH1A1. Further, we found that knockdown of Beclin-1 inhibited the stem cell-like properties and restored osimertinib cytotoxicity. Osimertinib combined with chloroquine inhibited tumor growth more effectively than alone in xenograft mice. These results reveal that autophagy plays an adverse role in osimertinib cytotoxicity through inducing stem cell-like properties. Combination therapy of EGFR-TKI and autophagy inhibitor could provide a promising strategy to improve osimertinib cytotoxicity.

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

Cell lines are essential tools to standardize and compare experimental findings in basic and translational cancer research. The current dogma states that cancer stem cells feature an increased tumor initiation capacity and are also chemoresistant. Here, we identified and comprehensively characterized three morphologically distinct cellular subtypes in the non–small cell lung cancer cell line A549 and challenge the current cancer stem cell dogma. Subtype-specific cellular morphology is maintained during short-term culturing, resulting in the formation of holoclonal, meroclonal, and paraclonal colonies. A549 holoclone cells were characterized by an epithelial and stem-like phenotype, paraclone cells featured a mesenchymal phenotype, whereas meroclone cells were phenotypically intermediate. Cell-surface marker expression of subpopulations changed over time, indicating an active epithelial-to-mesenchymal transition (EMT), in vitro and in vivo. EMT has been associated with the overexpression of the immunomodulators PD-L1 and PD-L2, which were 37- and 235-fold overexpressed in para- versus holoclone cells, respectively. We found that DNA methylation is involved in epigenetic regulation of marker expression. Holoclone cells were extremely sensitive to cisplatin and radiotherapy in vitro, whereas paraclone cells were highly resistant. However, inhibition of the receptor tyrosine kinase AXL, whose expression is associated with an EMT, specifically targeted the otherwise highly resistant paraclone cells. Xenograft tumor formation capacity was 24- and 269-fold higher in holo- than mero- and paraclone cells, respectively. Our results show that A549 subpopulations might serve as a unique system to explore the network of stemness, cellular plasticity, tumor initiation capacity, invasive and metastatic potential, and chemo/radiotherapy resistance.

Lung cancer stem cells: origin, features, maintenance mechanisms and therapeutic targeting

Lung cancer remains the leading cause of cancer-related deaths despite recent breakthroughs in immunotherapy. The widely embraced cancer stem cell (CSC) theory has also been applied for lung cancer, postulating that an often small proportion of tumor cells with stem cell properties are responsible for tumor growth, therapeutic resistance and metastasis. The identification of these CSCs and underlying molecular maintenance mechanisms is considered to be absolutely necessary for developing therapies for their riddance, hence achieving remission. In this review, we will critically address the CSC concept in lung cancer and its advancement thus far. We will describe both normal lung stem cells and their malignant counterparts in order to identify common aspects with respect to their emergence and regulation. Subsequently, the importance of CSCs and their molecular features in lung cancers will be discussed in a preclinical and clinical context. We will highlight some examples on how lung CSCs attain stemness through different molecular modifications and cellular assistance from the tumor microenvironment. The exploitation of these mechanistic features for the development of pharmacological therapy will also be discussed. In summary, the validity of the CSC concept has been evidenced by various studies. Ongoing research to identify molecular mechanisms driving lung CSC have revealed potential new cell intrinsic as well as tumor microenvironment-derived therapeutic targets. Although successfully demonstrated in preclinical models, the clinical benefit of lung CSC targeted therapies has thus far not been demonstrated. Therefore, further research to validate the therapeutic value of CSC concept is required.

Lung Cancers: Molecular Characterization, Clonal Heterogeneity and Evolution, and Cancer Stem Cells

Lung cancer causes the largest number of cancer-related deaths in the world. Most (85%) of lung cancers are classified as non-small-cell lung cancer (NSCLC) and small-cell lung cancer (15%) (SCLC). The 5-year survival rate for NSCLC patients remains very low (about 16% at 5 years). The two predominant NSCLC histological phenotypes are adenocarcinoma (ADC) and squamous cell carcinoma (LSQCC). ADCs display several recurrent genetic alterations, including: KRAS, BRAF and EGFR mutations; recurrent mutations and amplifications of several oncogenes, including ERBB2, MET, FGFR1 and FGFR2; fusion oncogenes involving ALK, ROS1, Neuregulin1 (NRG1) and RET. In LSQCC recurrent mutations of TP53, FGFR1, FGFR2, FGFR3, DDR2 and genes of the PI3K pathway have been detected, quantitative gene abnormalities of PTEN and CDKN2A. Developments in the characterization of lung cancer molecular abnormalities provided a strong rationale for new therapeutic options and for understanding the mechanisms of drug resistance. However, the complexity of lung cancer genomes is particularly high, as shown by deep-sequencing studies supporting the heterogeneity of lung tumors at cellular level, with sub-clones exhibiting different combinations of mutations. Molecular studies performed on lung tumors during treatment have shown the phenomenon of clonal evolution, thus supporting the occurrence of a temporal tumor heterogeneity.

Utilization of lung cancer cell lines for the study of lung cancer stem cells

Lung cancer is one of the most lethal types of cancer, and its poor prognosis is primarily due to drug resistance and cancer recurrence. As it is associated with a low five-year survival rate, lung cancer stem cells (LCSCs) have been the subject of numerous recent studies. For these studies of LCSCs, lung cancer cell lines are more commonly used than lung cancer tissues obtained from patients, as they are easier to acquire. The methods utilized for the identification of LCSCs from lung cancer cell lines include fluorescence activated cell sorting (FACS), magnetic activated cell sorting (MACS), sphere-forming assay and bacterial surface display library screening. As LCSCs have certain proteins expressed on the surface (CD133, CD44 and CD24) or in the cytoplasm (ALDH and ABCG2), which may act as specific markers, the most frequently used technique to identify and obtain LCSCs is FACS. The current lack of recognized biomarkers in LCSCs makes the identification of LCSCs problematic. Furthermore, the various proportions of LCSCs in specific cell lines, as revealed by numerous previous studies, may cause the LCSC model to be questioned with regard to whether the utilization of certain lung cancer cell lines is dependable for LCSC studies. The current review focuses on lung cancer cell lines that are used for the study of LCSCs and the methods available to identify LCSCs with various markers. The present study also aimed to determine the proportion of LCSCs present in specific cell lines reported by various studies, and to discuss the suitability of specific lung cancer cell lines for the study of LCSCs.

Hypericin affects cancer side populations via competitive inhibition of BCRP

OBJECTIVE

Cancer stem-like cells (CSLCs) are considered a root of tumorigenicity and resistance. However, their identification remains challenging. The use of the side population (SP) assay as a credible marker of CSLCs remains controversial. The SP assay relies on the elevated activity of ABC transporters that, in turn, can be modulated by hypericin (HYP), a photosensitizer and bioactive compound of St. John's Wort (Hypericum perforatum), a popular over-the-counter antidepressant. Here we aimed to comprehensively characterize the SP phenotype of cancer cells and to determine the impact of HYP on these cells.

METHODS

Flow cytometry and sorting-based assays were employed, including CD24-, CD44-, CD133-, and ALDH-positivity, clonogenicity, 3D-forming ability, ABC transporter expression and activity, and intracellular accumulation of HYP/Hoechst 33342. The tumorigenic ability of SP, nonSP, and HYP-treated cells was verified by xenotransplantation into immunodeficient mice.

RESULTS

The SP phenotype was associated with elevated expression of several investigated transporters and more intensive growth in non-adherent conditions but not with higher clonogenicity, tumorigenicity or ALDH-positivity. Despite stimulated BCRP level and MRP1 activity, HYP reversibly decreased the SP proportion, presumably via competitive inhibition of BCRP. HYP-selected SP cells acquired additional traits of resistance and extensively eliminated HYP.

CONCLUSIONS

Our results suggest that SP is not an unequivocal CSLC-marker. However, SP could play an important role in modulating HYP-treatment and serve as a negative predictive tool for HYP-based therapies. Moreover, the use of supplements containing HYP by cancer patients should be carefully considered, due to its proposed effect on drug efflux and complex impact on tumor cells, which have not yet been sufficiently characterized.

Concise Review: Resistance to Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer: The Role of Cancer Stem Cells

Among the potential mechanisms involved in resistance to tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer, the manifestation of stem-like properties in cancer cells seems to have a crucial role. Alterations involved in the development of TKI resistance may be acquired in a very early phase of tumorigenesis, supporting the hypothesis that these aberrations may be present in cancer stem cells (CSCs). In this regard, the characterization of tumor subclones in the initial phase and the identification of the CSCs may be helpful in planning a specific treatment to target selected biomarkers, suppress tumor growth, and prevent drug resistance. The aim of this review is to elucidate the role of CSCs in the development of resistance to TKIs and its implication for the management of patients. Stem Cells 2018;36:633-640.

Histone acetyltransferase inhibitor CPTH6 preferentially targets lung cancer stem-like cells

Cancer stem cells (CSCs) play an important role in tumor initiation, progression, therapeutic failure and tumor relapse. In this study, we evaluated the efficacy of the thiazole derivative 3-methylcyclopentylidene-[4-(4′-chlorophenyl)thiazol-2-yl]hydrazone (CPTH6), a novel pCAF and Gcn5 histone acetyltransferase inhibitor, as a small molecule that preferentially targets lung cancer stem-like cells (LCSCs) derived from non-small cell lung cancer (NSCLC) patients. Notably, although CPTH6 inhibits the growth of both LCSC and NSCLC cell lines, LCSCs exhibit greater growth inhibition than established NSCLC cells. Growth inhibitory effect of CPTH6 in LCSC lines is primarily due to apoptosis induction. Of note, differentiated progeny of LCSC lines is more resistant to CPTH6 in terms of loss of cell viability and reduction of protein acetylation, when compared to their undifferentiated counterparts. Interestingly, in LCSC lines CPTH6 treatment is also associated with a reduction of stemness markers. By using different HAT inhibitors we provide clear evidence that inhibition of HAT confers a strong preferential inhibitory effect on cell viability of undifferentiated LCSC lines when compared to their differentiated progeny. In vivo, CPTH6 is able to inhibit the growth of LCSC-derived xenografts and to reduce cancer stem cell content in treated tumors, as evidenced by marked reduction of tumor-initiating capacity in limiting dilution assays. Strikingly, the ability of CPTH6 to inhibit tubulin acetylation is also confirmed in vivo. Overall, our studies propose histone acetyltransferase inhibition as an attractive target for cancer therapy of NSCLC.

Road to stemness in hepatocellular carcinoma

Carcinogenic process has been proposed to relay on the capacity to induce local tissue damage and proliferative repair. Liver has a great regeneration capacity and currently, most studies point towards the dominant role of hepatocytes in regeneration at all levels of liver damage. The most frequent liver cancer is hepatocellular carcinoma (HCC). Historical findings originally led to the idea that the cell of origin of HCC might be a progenitor cell. However, current linage tracing studies put the progenitor hypothesis of HCC origin into question. In agreement with their dominant role in liver regeneration, mature hepatocytes are emerging as the cell of origin of HCC, although, the specific hepatocyte subpopulation of origin is yet to be determined. The relationship between the cancer cell of origin (CCO) and cancer-propagating cells, known as hepatic cancer stem cell (HCSC) is unknown. It has been challenging to identify the definitive phenotypic marker of HCSC, probably due to the existence of different cancer stem cells (CSC) subpopulations with different functions within HCC. There is a dynamic interconversion among different CSCs, and between CSC and non-CSCs. Because of that, CSC-state is currently defined as a description of a highly adaptable and dynamic intrinsic property of tumor cells, instead of a static subpopulation of a tumor. Altered conditions could trigger the gain of stemness, some of them include: EMT-MET, epigenetics, microenvironment and selective stimulus such as chemotherapy. This CSC heterogeneity and dynamism makes them out reach from therapeutic protocols directed to a single target. A further avenue of research in this line will be to uncover mechanisms that trigger this interconversion of cell populations within tumors and target it.

Detachment-induced E-cadherin expression promotes 3D tumor spheroid formation but inhibits tumor formation and metastasis of lung cancer cells

The epithelial-to-mesenchymal transition is proposed to be a key mechanism responsible for metastasis-related deaths. Similarly, cancer stem cells (CSCs) have been proposed to be a key driver of tumor metastasis. However, the link between the two events and their control mechanisms is unclear. We used a three-dimensional (3D) tumor spheroid assay and other CSC-indicating assays to investigate the role of E-cadherin in CSC regulation and its association to epithelial-to-mesenchymal transition in lung cancer cells. Ectopic overexpression and knockdown of E-cadherin were found to promote and retard, respectively, the formation of tumor spheroids in vitro but had opposite effects on tumor formation and metastasis in vivo in a xenograft mouse model. We explored the discrepancy between the in vitro and in vivo results and demonstrated, for the first time, that E-cadherin is required as a component of a major survival pathway under detachment conditions. Downregulation of E-cadherin increased the stemness of lung cancer cells but had an adverse effect on their survival, particularly on non-CSCs. Such downregulation also promoted anoikis resistance and invasiveness of lung cancer cells. These results suggest that anoikis assay could be used as an alternative method for in vitro assessment of CSCs that involves dysregulated adhesion proteins. Our data also suggest that agents that restore E-cadherin expression may be used as therapeutic agents for metastatic cancers.

Epithelial-to-Mesenchymal Transition and MicroRNAs in Lung Cancer

Despite major advances, non-small cell lung cancer (NSCLC) remains the major cause of cancer-related death in developed countries. Metastasis and drug resistance are the main factors contributing to relapse and death. Epithelial-to-mesenchymal transition (EMT) is a complex molecular and cellular process involved in tissue remodelling that was extensively studied as an actor of tumour progression, metastasis and drug resistance in many cancer types and in lung cancers. Here we described with an emphasis on NSCLC how the changes in signalling pathways, transcription factors expression or microRNAs that occur in cancer promote EMT. Understanding the biology of EMT will help to define reversing process and treatment strategies. We will see that this complex mechanism is related to inflammation, cell mobility and stem cell features and that it is a dynamic process. The existence of intermediate phenotypes and tumour heterogeneity may be debated in the literature concerning EMT markers, EMT signatures and clinical consequences in NSCLC. However, given the role of EMT in metastasis and in drug resistance the development of EMT inhibitors is an interesting approach to counteract tumour progression and drug resistance. This review describes EMT involvement in cancer with an emphasis on NSCLC and microRNA regulation.

Interleukin-6 identified as an important factor in hypoxia- and aldehyde dehydrogenase-based gefitinib adaptive resistance in non-small cell lung cancer cells

Gefitinib resistance and relapse of the disease were the greatest challenges facing clinical therapy of non-small-cell lung cancer (NSCLC). Of note, regarding the hypoxia condition in solid tumor tissues in vivo, roles of hypoxia in gefitinib adaptive resistance and its association with lung cancer stem cells (LCSCs) have not been fully elucidated. In the present study, the role of hypoxia in gefitinib adaptive resistance and its association with aldehyde dehydrogenase (ALDH)-based LCSC gefitinib resistance were comparatively studied using RNA-sequencing (RNA-seq) technology. Co-treatment of PC9 cells with gefitinib and hypoxia (1% O₂) significantly enhanced adaptive resistance compared with gefitinib or hypoxia treatment alone. An ALDEFLUOR assay demonstrated that there was a significant increase of ALDH expression level in hypoxia and gefitinib co-treated PC9 cells, in addition to a higher ratio of G₀/G₁ quiescent cell enrichment and acquisition of epithelial-mesenchymal transition. RNA-seq analysis revealed that interleukin-6 (IL-6) is an important common factor in hypoxia and ALDH-based gefitinib resistance, supported by inflammation-associated tumor necrosis factor, nuclear factor-κB and Janus kinase-signal transducer and activator of transcription signaling pathway enrichment. Furthermore, exposure of PC9 and HCC827 cells to IL-6 increased gefitinib adaptive resistance. Consequently, IL-6 expression level was a poor prognostic marker for patients with NSCLC and adenocarcinoma. Thus, targeting IL-6 combined with tyrosine kinase inhibitor treatment may be promising in NSCLC clinical therapy in the future.

5T4-specific chimeric antigen receptor modification promotes the immune efficacy of cytokine-induced killer cells against nasopharyngeal carcinoma stem cell-like cells

Relapse and metastasis of nasopharyngeal carcinoma (NPC) are presumably attributed to cancer stem cells (CSCs). In recent years, chimeric antigen receptor (CAR)-modified immune effector cells have been shown to have impressive antitumour efficacy. In this study, we aimed to identify appropriate tumour-associated antigens predominantly expressed on NPC stem cells (NPCSCs) and determine their suitability for CAR-engineered cytokine-induced killer (CIK) cell therapy against NPC. By investigating the expression patterns of potential target antigens (ROR1, 5T4 and CAIX) in NPC, we found that the oncofetal antigen 5T4 was predominately expressed in NPC cell lines and tissues but absent in non-cancerous nasopharyngeal tissues. Moreover, significantly enhanced expression of 5T4 in NPC spheroids revealed its relationship with putative NPCSCs. Hence, we designed a CAR construct (5T4-28Z) specific for 5T4 and generated CAR-transduced CIK cells. Our results showed that the artificial CAR was efficiently expressed on the surface of CIK cells and that no native phenotypes were altered by the gene transduction. Functional assays revealed that 5T4-28Z-CIK cells possessed both CAR-mediated and CAR-independent anti-NPC activity and were capable of efficiently attacking NPC cells, especially NPCSC-like cells in vitro, suggesting that they might serve as an attractive tool for developing efficient therapies against NPC.

The role of hypoxia on the acquisition of epithelial-mesenchymal transition and cancer stemness: a possible link to epigenetic regulation

A hypoxic microenvironment leads to cancer progression and increases the metastatic potential of cancer cells within tumors via epithelial-mesenchymal transition (EMT) and cancer stemness acquisition. The hypoxic response pathway can occur under oxygen tensions of < 40 mmHg through hypoxia-inducible factors (HIFs), which are considered key mediators in the adaptation to hypoxia. Previous studies have shown that cellular responses to hypoxia are required for EMT and cancer stemness maintenance through HIF-1α and HIF-2α. The principal transcription factors of EMT include Twist, Snail, Slug, Sip1 (Smad interacting protein 1), and ZEB1 (zinc finger E-box-binding homeobox 1). HIFs bind to hypoxia response elements within the promoter region of these genes and also target cancer stem cell-associated genes and mediate transcriptional responses to hypoxia during stem cell differentiation. Acquisition of stemness characteristics in epithelial cells can be induced by activation of the EMT process. The mechanism of these phenotypic changes includes epigenetic alterations, such as DNA methylation, histone modification, chromatin remodeling, and microRNAs. Increased expression of EMT and pluripotent genes also play a role through demethylation of their promoters. In this review, we summarize the role of hypoxia on the acquisition of EMT and cancer stemness and the possible association with epigenetic regulation, as well as their therapeutic applications.

Target Therapies for Uterine Carcinosarcomas: Current Evidence and Future Perspectives

Carcinosarcomas (CS) in gynecology are very infrequent and represent only 2-5% of uterine cancers. Despite surgical cytoreduction and subsequent chemotherapy being the primary treatment for uterine CS, the overall five-year survival rate is 30 ± 9% and recurrence is extremely common (50-80%). Due to the poor prognosis of CS, new strategies have been developed in the last few decades, targeting known dysfunctional molecular pathways for immunotherapy. In this paper, we aimed to gather the available evidence on the latest therapies for the treatment of CS. We performed a systematic review using the terms "uterine carcinosarcoma", "uterine Malignant Mixed Müllerian Tumors", "target therapies", "angiogenesis therapy", "cancer stem cell therapy", "prognostic biomarker", and "novel antibody-drug". Based on our results, the differential expression and accessibility of epithelial cell adhesion molecule-1 on metastatic/chemotherapy-resistant CS cells in comparison to normal tissues and Human Epidermal Growth Factor Receptor 2 (HER2) open up new possibilities in the field of target therapy. Nevertheless, future investigations are needed to clarify the impact of these new therapies on survival rate and medium-/long-term outcomes.

Engineering cancer stem-like cells from normal human lung epithelial cells

It has been proposed that a subpopulation of tumour cells with stem cell-like characteristics, known as cancer stem cells (CSCs), drives tumour initiation and generates tumour heterogeneity, thus leading to cancer metastasis, recurrence, and drug resistance. Although there has been substantial progress in CSC research into many solid tumour types, an understanding of the biology of CSCs in lung cancer remains elusive, mainly because of their heterogeneous origins and high plasticity. Here, we demonstrate that engineered lung cancer cells derived from normal human airway basal epithelial cells possessed CSC-like characteristics in terms of multilineage differentiation potential and strong tumour-initiating ability. Moreover, we established an in vitro 3D culture system that allowed the in vivo differentiation process of the CSC-like cells to be recapitulated. This engineered CSC model provides valuable opportunities for studying the biology of CSCs and for exploring and evaluating novel therapeutic approaches and targets in lung CSCs.

Chemoresistance of Lung and Breast Cancer Cells Growing Under Prolonged Periods of Serum Starvation

The efficacy of chemotherapy is hindered by both tumor heterogeneity and acquired or intrinsic multi-drug resistance caused by the contribution of multidrug resistance proteins and stemness-associated prosurvival markers. Therefore, targeting multi-drug resistant cells would be much more effective against cancer. In this study, we characterized the chemoresistance properties of adherent (anchorage-dependent) lung H460 and breast MCF-7 cancer cells growing under prolonged periods of serum starvation (PPSS). We found that under PPSS, both cell lines were highly resistant to Paclitaxel, Colchicine, Hydroxyurea, Obatoclax, Wortmannin, and LY294002. Levels of several proteins associated with increased stemness such as Sox2, MDR1, ABCG2, and Bcl-2 were found to be elevated in H460 cells but not in MCF-7 cells. While pharmacological inhibition of either MDR1, ABCG2, Bcl-2 with Verapamil, Sorafenib, or Obatoclax, respectively decreased the levels of their target proteins under routine culture conditions as expected, such inhibition did not reverse PX resistance in PPSS conditions. Paradoxically, treatment with inhibitors in serum-starved conditions produced an elevation of their respective target proteins. In addition, we found that Digitoxin, an FDA approved drug that decrease the viability of cancer cells growing under PPSS, downregulates the expression of Sox2, MDR1, phospho- AKT, Wnt5a/b, and β-catenin. Our data suggest that PPSS-induced chemoresistance is the result of extensive rewiring of intracellular signaling networks and that multi-resistance can be effectively overcome by simultaneously targeting multiple targets of the rewired network. Furthermore, our PPSS model provides a simple and useful tool to screen drugs for their ability to target multiple pathways of cancer resistance. J. Cell. Physiol. 232: 2033-2043, 2017. © 2016 Wiley Periodicals, Inc.

CMTM1_v17 is associated with chemotherapy resistance and poor prognosis in non-small cell lung cancer

Background

Considering neoadjuvant chemotherapy (NAC) prior to surgery could shrink and reduce the primary tumor and distant micro-metastases to reduce the high relapses rates, NAC has been an accepted therapeutic management for patients with non-small cell lung cancer (NSCLC). CMTM1_v17 is highly expressed in human testis tissues and solid tumor tissues but relatively low expression was obtained in the corresponding normal tissues. This study aims to investigate the significance of CMTM1_v17 in NSCLC and its association with platinum-based NAC efficacy.

Methods

31 pairs of tumor tissues before and after NAC and 78 resected tumor tissues after NAC were utilized for immunohistochemistry (IHC) staining of CMTM1_v17 protein. The correlation between CMTM1_v17 expression and chemotherapy efficacy was analyzed. The prognostic value of CMTM1_v17 index for disease-free survival (DFS) and overall survival (OS) was analyzed using Kaplan-Meier survival and multivariable Cox regression.

Results

CMTM1_v17 expression was related to treatment effect and outcome in tumor tissues after NAC not before NAC from 31 cases of NSCLC. We identified that high CMTM1_v17 expression was associated with low objective remission rate (ORR) (P = 0.008) and poor prognosis (the median OS: 35.1 months vs 65.6 months, P = 0.0045; the median DFS: 17.27 months vs 35.54 months, P = 0.0207) in the 31 patients. Next, we detected CMTM1_v17 expression to confirm correlation between this protein status and clinical characteristics in 78 NSCLC patients with NAC treatment. The upregulation of CMTM1_v17 had a higher SD rate (P = 0.007) and worse outcome (the median OS: 41.0 months vs 80.6 months, P = 0.0028; the median DFS: 33.4 vs 64.8 months, P = 0.0032). COX multivariate analysis indicated that CMTM1_v17 is an independent prognostic risk factor on patients who have received NAC (OS: HR = 3.642, P = 0.002; DFS:HR = 3.094, P = 0.002).

Conclusions

CMTM1_v17 expression is significantly associated with chemoresistance and poor prognosis of the early stage NSCLC patients who have received NAC.

Emerging roles of RAC1 in treating lung cancer patients

The Ras-related C3 botulinum toxin substrate 1 (RAC1), a member of the Rho family of small guanosine triphosphatases, is critical for many cellular activities, such as phagocytosis, adhesion, migration, motility, cell proliferation, and axonal growth. In addition, RAC1 plays an important role in cancer angiogenesis, invasion, and migration, and it has been reported to be related to most cancers, such as breast cancer, gastric cancer, testicular germ cell cancer, and lung cancer. Recently, the therapeutic target of RAC1 in cancer has been investigated. In addition, some investigations have shown that inhibition of RAC1 can reverse drug-resistance in non-small cell lung cancer. In this review, we summarize the recent advances in understanding the role of RAC1 in lung cancer and the underlying mechanisms and discuss its value in clinical therapy.

Kinetic Modeling of ABCG2 Transporter Heterogeneity: A Quantitative, Single-Cell Analysis of the Side Population Assay

The side population (SP) assay, a technique used in cancer and stem cell research, assesses the activity of ABC transporters on Hoechst staining in the presence and absence of transporter inhibition, identifying SP and non-SP cell (NSP) subpopulations by differential staining intensity. The interpretation of the assay is complicated because the transporter-mediated mechanisms fail to account for cell-to-cell variability within a population or adequately control the direct role of transporter activity on staining intensity. We hypothesized that differences in dye kinetics at the single-cell level, such as ABCG2 transporter-mediated efflux and DNA binding, are responsible for the differential cell staining that demarcates SP/NSP identity. We report changes in A549 phenotype during time in culture and with TGFβ treatment that correlate with SP size. Clonal expansion of individually sorted cells re-established both SP and NSPs, indicating that SP membership is dynamic. To assess the validity of a purely kinetics-based interpretation of SP/NSP identity, we developed a computational approach that simulated cell staining within a heterogeneous cell population; this exercise allowed for the direct inference of the role of transporter activity and inhibition on cell staining. Our simulated SP assay yielded appropriate SP responses for kinetic scenarios in which high transporter activity existed in a portion of the cells and little differential staining occurred in the majority of the population. With our approach for single-cell analysis, we observed SP and NSP cells at both ends of a transporter activity continuum, demonstrating that features of transporter activity as well as DNA content are determinants of SP/NSP identity.

Prolonged pemetrexed pretreatment augments persistence of cisplatin-induced DNA damage and eliminates resistant lung cancer stem-like cells associated with EMT

Background

Lung cancer is the leading cause of cancer-related mortality, and new therapeutic options are urgently needed. Non-small cell lung cancer (NSCLC) accounts for approximately 85 % of all lung cancers, with the current standard regimen of care for NSCLC including chemotherapy with pemetrexed as a single agent or in combination with platinum-based agents, e.g. cisplatin. Pemetrexed is a folic acid antagonist that inhibits the synthesis of precursor nucleotides, whereas cisplatin directly induces DNA adducts, the repair of which is dependent on sufficiently high nucleotide levels. In the clinical setting, the pemetrexed-cisplatin combination therapy is administered concomitantly. We hypothesized that prolonged pretreatment with pemetrexed could be beneficial, as prior depletion of nucleotide pools could sensitize cancer cells to subsequent treatment with cisplatin.

Methods

NSCLC A549 and H460 cells were treated with pemetrexed for 72 h. In addition, 24 h of cisplatin treatment was initiated at day 1, 2 or 3 resulting in either simultaneous pemetrexed application or pemetrexed pretreatment for 24 or 48 h, respectively. Cell growth and colony formation as well as senescence induction were quantified after treatment. Cell cycle distribution and phosphorylation of histone variant H2AX as a surrogate marker for DNA damage was quantified by flow cytometry. Relative changes in gene expression were determined by quantitative real time PCR.

Results

Prolonged pemetrexed pretreatment for 48 h prior to cisplatin treatment maximally delayed long-term cell growth and significantly reduced the number of recovering clones. Moreover, apoptosis and senescence were augmented and recovery from treatment-induced DNA damage was delayed. Interestingly, a cell population was identified that displayed an epithelial-to-mesenchymal transition (EMT) and which had a stem cell phenotype. This population was highly resistant to concomitant pemetrexed-cisplatin treatment but was sensitized by pemetrexed pretreatment.

Conclusions

Adaptation of the standard treatment schedule to include pretreatment with pemetrexed optimizes the anticancer efficiency of pemetrexed-cisplatin combination therapy, which correlates with a persistence of treatment-induced DNA damage. Therefore, this study warrants further investigations to elucidate whether such an adaptation could enhance the effectiveness of the standard clinical treatment regimen. In addition, a subpopulation of therapy resistant cells with EMT and cancer stem cell features was identified that was resistant to the standard treatment regimen but sensitive to pemetrexed pretreatment combined with cisplatin.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2117-4) contains supplementary material, which is available to authorized users.

Enhancement of tumor initiation and expression of KCNMA1, MORF4L2 and ASPM genes in the adenocarcinoma of lung xenograft after vorinostat treatment

Cancer stem cells (CSCs) are usually tolerant to chemotherapy and radiotherapy and associated with tumor relapse. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor (HDACI), is currently being used in clinical trials of lung cancer. However, SAHA facilitates the formation of induced pluripotent stem cells from somatic cells. We hypothesized that SAHA would mediate the CSCs properties and subsequently confer a more malignant phenotype in lung cancer. Transfected H1299 lung cancer cells, which stably expresses a triple fused reporter gene (DsRedm-Fluc-tTKsr39) under the control of CMV promoter was used to establish a xenograft mouse model. After the treatment of SAHA, H1299 cell line and tumor xenografts were sorted by fluorescence-activated cell sorting (FACS) based on aldehyde dehydrogenase (ALDH) activity. We found that SAHA could suppress the growth of xenografted H1299 tumors with decreased proportion of ALDH^br lung cancer cells indicating that SAHA may target CSCs. However, SAHA significantly enhanced the tumor initiating capacity and the expression of malignant genes such as KCNMA1, MORF4L2 and ASPM in the remaining living ALDH^br cells. These findings suggested that SAHA treatment created a more drug-resistant state in residual ALDH^br cells. The in vivo imaging technique may facilitate searching and characterization of CSCs.

Hypoxia and TGF-β1 lead to endostatin resistance by cooperatively increasing cancer stem cells in A549 transplantation tumors

BACKGROUND

Lung cancer is the leading cause of cancer-related deaths worldwide, and treatments for lung cancer have a high failure rate. Anti-angiogenic therapy is also often ineffective because of refractory disease. Endostatin (ES) is one of the most widely-used anti-angiogenic drugs for lung cancer in China, and resistance to it is a barrier that needs to be resolved. It has been shown that myeloid-derived suppressor cells (MDSCs) are involved in resistance to ES. Whether other cells and/or cell factors in the tumor microenvironment that have been shown to be related to resistance to other anti-cancer drugs are also involved in ES resistance is unknown.

RESULTS

In this study, we showed that after continuously treatment with ES for 12 days, volumes of A549 transplantation tumors of mice reached the sizes of tumors which were borne by mice that were treated with normal saline and this meant that resistance to ES appeared. Cancer stem cells (CSCs), which have been widely accepted as one of reasons responsible for resistance to many anti-tumor drugs were also being discovered increased proportionally in A549 transplantation tumors after ES treatment for 12 days. During further exploration of reasons for this increase, we discovered that after ES treatment, microvessel density and vascular endothelial growth factor level was decreased in tumors, whereas transforming growth factor (TGF)-β1 level was elevated, and MDSCs, one of the sources of TGF-β1, were also increased. We speculate that hypoxia and TGF-β1 are responsible for the increased CSC number in A549 transplantation tumors. By using cobalt chloride to mimic hypoxia and human recombinant TGF-β1 in vitro, we found that hypoxia and TGF-β1can indeed enhance the stemness of A549 cells. In addition, the inductive effect of hypoxia is stronger than TGF-β1, and the combination of both is stronger than either alone, which is first report of such a finding, to our knowledge.

CONCLUSIONS

Increased TGF-β1 and strengthened hypoxia in A549 transplantation tumors, as a result of ES therapy, cooperatively increase proportion of CSCs that are involved in ES resistance which was revealed by failure of tumor volume repression after continuously treatment with ES for 12 days.