Lung cancer-initiating cells: a novel target for cancer therapy. Target Oncol. 2013;8:159-172. [PMID: 23314952 PMCID: PMC3763165 DOI: 10.1007/s11523-012-0247-4]

Effects and mechanisms of N6-methyladenosine RNA methylation in environmental pollutant-induced carcinogenesis

Environmental pollution, including air pollution, plastic contamination, and heavy metal exposure, is a pressing global issue. This crisis contributes significantly to pollution-related diseases and is a critical risk factor for chronic health conditions, including cancer. Mounting evidence underscores the pivotal role of N6-methyladenosine (m6A) as a crucial regulatory mechanism in pathological processes and cancer progression. Governed by m6A writers, erasers, and readers, m6A orchestrates alterations in target gene expression, consequently playing a vital role in a spectrum of RNA processes, covering mRNA processing, translation, degradation, splicing, nuclear export, and folding. Thus, there is a growing need to pinpoint specific m6A-regulated targets in environmental pollutant-induced carcinogenesis, an emerging area of research in cancer prevention. This review consolidates the understanding of m6A modification in environmental pollutant-induced tumorigenesis, explicitly examining its implications in lung, skin, and bladder cancer. We also investigate the biological mechanisms that underlie carcinogenesis originating from pollution. Specific m6A methylation pathways, such as the HIF1A/METTL3/IGF2BP3/BIRC5 network, METTL3/YTHDF1-mediated m6A modification of IL 24, METTL3/YTHDF2 dynamically catalyzed m6A modification of AKT1, METTL3-mediated m6A-modified oxidative stress, METTL16-mediated m6A modification, site-specific ATG13 methylation-mediated autophagy, and the role of m6A in up-regulating ribosome biogenesis, all come into play in this intricate process. Furthermore, we discuss the direction regarding the interplay between pollutants and RNA metabolism, particularly in immune response, providing new information on RNA modifications for future exploration.

Boric Acid Affects the Expression of DNA Double-Strand Break Repair Factors in A549 Cells and A549 Cancer Stem Cells: An In Vitro Study

DNA double-strand break (DSB) repair genes interact with tumor stemness- and resistance-associated processes in cancer stem cells (CSCs). Therefore, targeting DNA DSB genes in cancer treatment is important for the CSC phenotype. Although the anti-cancer effect of boric acid (BA) has been studied, its effect on DNA DSB is unclear. Moreover, no studies investigate BA's effects on DNA DSB of lung cancer stem cells (LC-SCs). To fill the gap, we aimed to assess the effects of BA on A549 cancer stem cells. CSCs were isolated from human non-small cell lung cancer cells (A549) and characterized by flow cytometry. Different concentrations of BA (at doses ranging from 1 to 100 mM) were applied to cancer stem cells. Cytotoxic activities were determined using the cell viability assay (MTT assay) at 24 and 48 h. Expression levels of DNA DSB genes that BRCA1, BRCA2, RAD51, KU70/80, ATM, and XRCC4 were evaluated by RT-qPCR. Additionally, immunofluorescence staining analysis was exploited for caspase-3 and E-cadherin. ATM expression increased significantly (p < 0.001). No significant change was observed in the expression of other genes. Moreover, BA up-regulated caspase-3 and E-cadherin expression. Consequently, we can say that BA affects DNA DSB and the apoptotic abilities of LC-SCs.

Visualization of Metastatic Lung Cancer with TiNIR

The development of efficient biomarkers and probes for monitoring and treating cancer, specifically metastatic cancer, is a critical research area that can have a significant impact on both patient outcomes and drug discovery. In this context, TiNIR has been developed to detect tumor-initiating cells (TICs), with heme oxygenase 2 (HO2) as a promising therapeutic biomarker for tumor-initiating cells. In this study, TiNIR has demonstrated its effectiveness as an in vivo metastatic lung cancer tracker, highlighting its potential as a valuable tool in cancer research and therapy. The development of innovative approaches that selectively target metastatic cancers represents a promising avenue for improving survival rates and enhancing the quality of life of cancer patients.

Pathological analysis of hesperetin-derived small cell lung cancer by artificial intelligence technology under fiberoptic bronchoscopy

Lung cancer is one of the most common tumors. There are 1.8 million new cases worldwide each year, accounting for about 13% of all new tumors. Lung cancer is the most important cause of cancer-related deaths. 1.4 million people die of lung cancer each year. This article uses artificial intelligence technology to analyze the pathology of hesperetin-derived small cell lung cancer under fiberoptic bronchoscopy. This article takes 48 lung slice samples as the research object. Among them, 36 cases of lung small cell carcinoma have history slices from Lhasa City Institute of Biology, the patient has complete cases, and the other 12 normal lung slices come from Xinjiang Biotechnology Laboratory. In this paper, the above-mentioned 36 lung cancer slices became the study group, and 12 normal slices became the reference group. This article presents a method for hesperetin-fiber bronchoscope to study the pathological mechanism of lung small cell carcinoma (H-FBS), which is used to study slices. The above-mentioned 48 samples were taken for slice observation. First, the 48 slices were technically tested by artificial intelligence fiber bronchoscope combined with hesperetin derivatives, and then the slice observation results were verified by CTC technology. In addition, in each step, the C5orf34 in the tissue is detected separately, which is beneficial to adjust the content of C5orf34 so that the treatment of lung cancer can control the development of lung cancer under fiberoptic bronchoscopy. Experimental results show that the diagnostic accuracy rate of this method is 97.9%, which is higher than that of lung biopsy (89%); compared with multiple CTC detection, the cost is low and the time is shor.

ALDH1 and SALL4 Expression in Cell Block Samples from Patients with Lung Adenocarcinoma and Malignant Pleural Effusion

Malignant pleural effusion (MPE) can accompany advanced lung adenocarcinoma. Recent studies suggest that MPE could contain a heterogeneous subpopulation of cells with stem-like properties, such as tumorigenicity and self-renewal, indicating that they could be the source of metastasis. Although previous studies analyzed the correlation between cancer stem cell (CSC) marker expression and clinical outcomes using lung cancer tissues, investigations regarding the association of MPE with CSC marker expression are limited. We performed immunohistochemistry to examine the expression of aldehyde dehydrogenase 1 (ALDH1) and Sal-like 4 (SALL4) in 46 cell block samples of MPE from patients with lung adenocarcinoma. ALDH1-positive and SALL4-positive cancer cells in MPE were detected in 30 (65.2%) and 21 samples (45.7%), respectively. Cluster formation was detected in 26 samples (56.5%). The number of clusters was significantly higher in ALDH1-positive/SALL4-negative samples. SALL4 expression was inversely correlated with the cluster ratio (r = −0.356) and positively associated with the Ki-67 index (r = 0.326), suggesting that MPE cells with high SALL4 expression comprised the proliferative subpopulation. In conclusion, we demonstrated that MPE contains an ALDH1-positive/SALL4-negative subpopulation exhibiting cluster formation and a SALL4-positive proliferative subpopulation.

Non-Coding RNAs in Lung Tumor Initiation and Progression

Lung cancer is one of the deadliest forms of cancer affecting society today. Non-coding RNAs, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), through the transcriptional, post-transcriptional, and epigenetic changes they impose, have been found to be dysregulated to affect lung cancer tumorigenesis and metastasis. This review will briefly summarize hallmarks involved in lung cancer initiation and progression. For initiation, these hallmarks include tumor initiating cells, immortalization, activation of oncogenes and inactivation of tumor suppressors. Hallmarks involved in lung cancer progression include metastasis and drug tolerance and resistance. The targeting of these hallmarks with non-coding RNAs can affect vital metabolic and cell signaling pathways, which as a result can potentially have a role in cancerous and pathological processes. By further understanding non-coding RNAs, researchers can work towards diagnoses and treatments to improve early detection and clinical response.

Identification of Sca-1+Abcg1+ bronchioalveolar epithelial cells as the origin of lung adenocarcinoma in Gprc5a-knockout mouse model through the interaction between lung progenitor AT2 and Lgr5 cells

The reason for the reduced efficacy of lung cancer therapy is the existence of lung cancer stem cells (CSCs). Targeting CSCs results in evolved phenotypes with increased malignancy, leading to therapy failure. Here, we propose a new therapeutic strategy: investigating the “transitional” cells that represent the stage between normal lung stem cells and lung CSCs. Identifying and targeting the key molecule that drives carcinogenesis to inhibit or reverse this process would thus provide new perspectives for early diagnosis and intervention in lung cancer. We used Gprc5a-knockout (KO) mice, the first animal model of spontaneous lung adenocarcinoma established by the deletion of a single lung tumor suppressor gene. We investigated the interaction of lung progenitor cells AT2 with Lgr5 cells in the generation of CSCs and related signaling mechanism. In the present study, using Gprc5a-KO mice, we found the initiator Sca-1⁺Abcg1⁺ subset with a CSC-like phenotype within the lung progenitor AT2 cell population in mice that had not yet developed tumors. We confirmed the self-renewal and tumor initiation capacities of this subset in vitro, in vivo, and clinical samples. Mechanistically, we found that the generation of Sca-1⁺Abcg1⁺ cells was associated with an interaction between AT2 and Lgr5 cells and the subsequent activation of the ECM1-α6β4-ABCG1 axis. Importantly, Sca-1⁺Abcg1⁺ and SPA⁺ABCG1⁺ cells specifically existed in the small bronchioles of Gprc5a-KO mice and patients with pneumonia, respectively. Thus, the present study unveiled a new kind of lung cancer-initiating cells (LCICs) and provided potential markers for the early diagnosis of lung cancer.

B7-H3-targeted Radioimmunotherapy of Human Cancer

BACKGROUND

Targeted Radioimmunotherapy (RIT) is an attractive approach to selectively localize therapeutic radionuclides to malignant cells within primary and metastatic tumors while sparing normal tissues from the effects of radiation. Many human malignancies express B7-H3 on the tumor cell surface, while expression on the majority of normal tissues is limited, presenting B7-H3 as a candidate target for RIT. This review provides an overview of the general principles of targeted RIT and discusses publications that have used radiolabeled B7-H3-targeted antibodies for RIT of cancer in preclinical or clinical studies.

METHODS

Databases including PubMed, Scopus, and Google Scholar were searched for publications through June 2018 using a combination of terms including "B7-H3", "radioimmunotherapy", "targeted", "radiotherapy", and "cancer". After screening search results for relevancy, ten publications were included for discussion.

RESULTS

B7-H3-targeted RIT studies to date range from antibody development and assessment of novel Radioimmunoconjugates (RICs) in animal models of human cancer to phase II/III trials in humans. The majority of clinical studies have used B7-H3-targeted RICs for intra- compartment RIT of central nervous system malignancies. The results of these studies have indicated high tolerability and favorable efficacy outcomes, supporting further assessment of B7-H3-targeted RIT in larger trials. Preclinical B7-H3-targeted RIT studies have also shown encouraging therapeutic outcomes in a variety of solid malignancies.

CONCLUSION

B7-H3-targeted RIT studies over the last 15 years have demonstrated feasibility for clinical development and support future assessment in a broader array of human malignancies. Future directions worthy of exploration include strategies that combine B7-H3- targeted RIT with chemotherapy or immunotherapy.

Identification of a new GLDC gene alternative splicing variant and its protumorigenic roles in lung cancer

Aim: To clarify the regulatory roles of GLDCV1, the first identified truncated glycine decarboxylase (GLDC), on cancer stem cells and tumorigenesis. Materials & methods: RT-PCR or RT-qPCR, immunoblotting and immunohistochemical staining were applied to assess gene expression. MTT, BrdU incorporation and colony formation assays were used to examine cell proliferation capacity. Soft agar colony formation and in vivo transplantation were applied to evaluate cellular transformation and tumorigenesis. Results & conclusion: Expression of GLDCV1 or GLDC was enhanced in non-small-cell lung cancer cell line and clinical samples. GLDCV1 overexpression induced MRC5 cell proliferation, transformation and tumorigenesis. Additionally, GLDCV1 increased lactate production and cancer stem cell marker expression and activated ERK and P38 pathways. Our study gained deeper insight into GLDC oncogene.

A Near-Infrared Probe Tracks and Treats Lung Tumor Initiating Cells by Targeting HMOX2

Tumor initiating cells (TIC) are resistant to conventional anticancer therapy and associated with metastasis and relapse in cancer. Although various TIC markers and their antibodies have been proposed, it is limited to the use of antibodies for in vivo imaging or treatment of TIC. In this study, we discovered heme oxygenase 2 (HMOX2) as a novel biomarker for TIC and developed a selective small molecule probe TiNIR (tumor initiating cell probe with near infrared). TiNIR detects and enriches the functionally active TIC in human lung tumors, and through the photoacoustic property, TiNIR also visualizes lung TIC in the patient-derived xenograft (PDX) model. Furthermore, we demonstrate that TiNIR inhibits tumor growth by blocking the function of HMOX2, resulting in significantly increased survival rates of the cancer model mice. The novel therapeutic target HMOX2 and its fluorescent ligand TiNIR will open a new path for the molecular level of lung TIC diagnosis and treatment.

Ambient fine particulate matter inhibits 15-lipoxygenases to promote lung carcinogenesis

Background

Epidemiological observations have demonstrated that ambient fine particulate matter with d_p < 2.5 μm (PM_2.5) as the major factor responsible for the increasing incidence of lung cancer in never-smokers. However, there are very limited experimental data to support the association of PM_2.5 with lung carcinogenesis and to compare PM_2.5 with smoking carcinogens.

Methods

To study whether PM_2.5 can contribute to lung tumorigenesis in a way similar to smoking carcinogen 4-methylnitrosamino-l-3-pyridyl-butanone (NNK) via 15-lipoxygenases (15-LOXs) reduction, normal lung epithelial cells and cancer cells were treated with NNK or PM_2.5 and then epigenetically and post-translationally examined the cellular and molecular profiles of the cells. The data were verified in lung cancer samples and a mouse lung tumor model.

Results

We found that similar to smoking carcinogen NNK, PM2.5 significantly enhanced cell proliferation, migration and invasion, but reduced the levels of 15-lipoxygenases-1 (15-LOX1) and 15-lipoxygenases-2 (15-LOX2), both of which were also obviously decreased in lung cancer tissues. 15-LOX1/15-LOX2 overexpression inhibited the oncogenic cell functions induced by PM2.5/NNK. The tumor formation and growth were significantly higher/faster in mice implanted with PM2.5- or NNK-treated NCI-H23 cells, accompanied with a reduction of 15-LOX1/15-LOX2. Moreover, 15-LOX1 expression was epigenetically regulated at methylation level by PM2.5/NNK, while both 15-LOX1 and 15-LOX2 could be significantly inhibited by a set of PM2.5/NNK-mediated microRNAs.

Conclusion

Collectively, PM2.5 can function as the smoking carcinogen NNK to induce lung tumorigenesis by inhibiting 15-LOX1/15-LOX2.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1380-z) contains supplementary material, which is available to authorized users.

Spotlight on Bortezomib: potential in the treatment of hepatocellular carcinoma

INTRODUCTION

This study reviews the evidence for the use of Bortezomib (BZB), a first-in-class proteasome inhibitor in advanced Hepatocellular carcinoma (HCC). This review aims to delineate the role of BZB within the management of non-surgical and metastatic HCC, either as an alternative or as an adjunct to the current treatment paradigm.

AREAS COVERED

In addition to BZB pharmacology and mechanism of action, safety and tolerance profiles of the drug obtained from clinical trials are explored. The utility of BZB as a therapeutic agent either alone or in combination with other therapies against HCC, including its application in both preclinical and clinical settings has been reviewed. In particular, we highlight the importance of preclinical evaluation of BZB as a combinatorial agent in synergism with other therapies for the use in the management of HCC.

EXPERT OPINION

There has been much interest surrounding the use of BZB, a first-in-class proteasome inhibitor for HCC therapy. The discernment of outcomes of BZB clinical trials for HCC need to take into consideration the disease-specific factors that can affect survival outcomes including patient selection and aetiological differences. Further preclinical testing of BZB in combination with other therapeutic modalities can be important for eliciting enhanced anti-HCC effects.

A comparison between lung carcinoma and a subcutaneous malignant tumor induced in rats by a 3,4-benzopyrene injection

Lung cancer is one of the most common carcinomas worldwide. It is of value to know whether lung is more vulnerable to carcinogens than other tissues. In this study we compared the carcinogenic potential of 3,4-benzopyrene administered by intrapulmonary injection or subcutaneous injection. Ninety rats were randomly divided into three groups (n=30/group). Rats under deep anesthesia were treated with 3,4-benzopyrene by intrapulmonary injection or scapular subcutaneous injection, or with the vehicle by subcutaneous injection. The Rats were sacrificed when they developed advanced somatic sarcomas or severe dyspnea and the rats without severe phenotypes were sacrificed after 1 year. The tumors were isolated and examined with H&E staining. The expression of Bcl-2, CYP1A1, and NF-κB mRNA and protein in somatic sarcoma and lung carcinoma tissues was examined by in situ hybridization, immunohistochemistry, and Western blot. No tumor development was observed in the control rats. Fifteen of the 30 rats receiving an intrapulmonary injection of 3,4-benzopyrene developed lung carcinomas, whereas all 30 rats treated with subcutaneous injection developed a malignant neoplasm under the skin. Positive Bcl-2, CYP1A1, and NF-κB protein staining was observed in lung carcinoma and subcutaneous malignant neoplasm but Bcl-2 protein expression was much stronger in subcutaneous malignant neoplasms than in lung carcinoma. The expression pattern of Bcl-2, CYP1A1, and NF-κB mRNA in lung carcinoma and subcutaneous malignant neoplasms was consistent with its protein expression. Our results indicated that the lung is not more vulnerable to carcinogens than other tissues. The lung may acquire a protective mechanism against lung carcinogenesis through regulation of Bcl-2 expression.

Reduction of MHC-I expression limits T-lymphocyte-mediated killing of Cancer-initiating cells

Background

It has been proposed that cancer establishment, maintenance, and recurrence may be attributed to a unique population of tumor cells termed cancer-initiating cells (CICs) that may include characteristics of putative cancer stem cell-like cells. Studies in lung cancer have shown that such cells can be enriched and propagated in vitro by culturing tumor cells in serum-free suspension as tumorspheres. CICs have been characterized for their phenotype, stem cell-like qualities, and their role in establishing tumor and maintaining tumor growth. Less is known about the interaction of CICs with the immune system.

Methods

We established CIC-enriched tumorspheres from murine TC-1 lung cancer cells, expressing human papillomavirus 16 (HPV-16) E6/E7 antigens, and evaluated their susceptibility to antitumor immune responses both in vitro and in vivo.

Results

TC-1 CICs demonstrated reduced expression of surface major histocompatibility complex (MHC)-I molecules compared to non-CICs. We similarly determined decreased MHC-I expression in five of six human lung cancer cell lines cultured under conditions enriching for CICs. In vivo, TC-1 cells enriched for CICs were resistant to human papillomavirus 16 E6/E7 peptide vaccine-mediated killing. We found that vaccinated mice challenged with CIC enriched tumorspheres demonstrated shorter survivals and showed significantly fewer CD8⁺ tumor infiltrating lymphocytes compared to CIC non-enriched challenged mice. Furthermore, cultured cytotoxic T lymphocytes (CTLs) from vaccinated mice demonstrated reduced capacity to lyse TC-1 cells enriched for CICs compared to non-enriched TC-1 cells. Following treatment with IFN-γ, both CIC enriched and non-enriched TC-1 cells expressed similar levels of MHC-I, and the increased MHC-I expression on CICs resulted in greater CTL-mediated tumor lysis and improved tumor-free survival in mice.

Conclusions

These results suggest that the attenuated expression of MHC-I molecules by CICs represents a potential strategy of CICs to escape immune recognition, and that the development of successful immunotherapy strategies targeting CICs may decrease their resistance to T cell-mediated immune detection by enhancing CIC MHC-I expression.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4389-3) contains supplementary material, which is available to authorized users.

Lung cancer stem cells-origin, characteristics and therapy

Cancer stem cells (CSCs) have gained an increasing attention recently in cancer research. CSCs have ability to generate new tumor through their stem cell properties, essentially self-renewal potential and differentiation into multiple cell lineages. Extensive evidences report that CSCs are resistant to many conventional therapies and mediate tumor recurrence. CSCs of lung cancer are well recognized by their specific markers such as CD133, CD44, ABCG2 and ALDH1A1 together with the CSC characteristics including spheroid and colony formation. Targeting these surface proteins with blocking antibodies and inhibition of ABC transporters and aldehyde dehydrogenase (ALDH) enzymes with small molecules may prove useful in inhibiting tumor progression. The Hh, Notch and Wnt pathways are key signaling cascades that govern cell fate during development and have been shown to be involved in CSCs in various solid tumors. Therapeutic approaches also target these signaling pathways in repressing the tumor progression. This review will focus on stem cell origins, role of signaling pathways, stem cell markers and therapeutic approaches specific to lung cancer.

Role of MDA-7/IL-24 a Multifunction Protein in Human Diseases

Subtraction hybridization identified genes displaying differential expression as metastatic human melanoma cells terminally differentiated and lost tumorigenic properties by treatment with recombinant fibroblast interferon and mezerein. This approach permitted cloning of multiple genes displaying enhanced expression when melanoma cells terminally differentiated, called melanoma differentiation associated (mda) genes. One mda gene, mda-7, has risen to the top of the list based on its relevance to cancer and now inflammation and other pathological states, which based on presence of a secretory sequence, chromosomal location, and an IL-10 signature motif has been named interleukin-24 (MDA-7/IL-24). Discovered in the early 1990s, MDA-7/IL-24 has proven to be a potent, near ubiquitous cancer suppressor gene capable of inducing cancer cell death through apoptosis and toxic autophagy in cancer cells in vitro and in preclinical animal models in vivo. In addition, MDA-7/IL-24 embodied profound anticancer activity in a Phase I/II clinical trial following direct injection with an adenovirus (Ad.mda-7; INGN-241) in tumors in patients with advanced cancers. In multiple independent studies, MDA-7/IL-24 has been implicated in many pathological states involving inflammation and may play a role in inflammatory bowel disease, psoriasis, cardiovascular disease, rheumatoid arthritis, tuberculosis, and viral infection. This review provides an up-to-date review on the multifunctional gene mda-7/IL-24, which may hold potential for the therapy of not only cancer, but also other pathological states.

Small-cell lung cancer: what we know, what we need to know and the path forward

Small-cell lung cancer (SCLC) is a deadly tumour accounting for approximately 15% of lung cancers and is pathologically, molecularly, biologically and clinically very different from other lung cancers. While the majority of tumours express a neuroendocrine programme (integrating neural and endocrine properties), an important subset of tumours have low or absent expression of this programme. The probable initiating molecular events are inactivation of TP53 and RB1, as well as frequent disruption of several signalling networks, including Notch signalling. SCLC, when diagnosed, is usually widely metastatic and initially responds to cytotoxic therapy but nearly always rapidly relapses with resistance to further therapies. There were no important therapeutic clinical advances for 30 years, leading SCLC to be designated a 'recalcitrant cancer'. Scientific studies are hampered by a lack of tissue availability. However, over the past 5 years, there has been a worldwide resurgence of studies on SCLC, including comprehensive molecular analyses, the development of relevant genetically engineered mouse models and the establishment of patient-derived xenografts. These studies have led to the discovery of new potential therapeutic vulnerabilities for SCLC and therefore to new clinical trials. Thus, while the past has been bleak, the future offers greater promise.

Isolation of Stem-Like Cancer Cells in Primary Endometrial Cancer Using Cell Surface Markers CD133 and CXCR4

Endometrial cancer (EC) is the most common familiar gynecologic malignant tumor identified in the female reproductive system and has been increasing yearly. In this study, we will identify the surface markers and stem cell markers related with cancer stem cells (CSCs) of EC. Tissue samples were obtained from endometrial cancer patients during surgical procedures. Single cells were isolated from the tissues for culturing, transfection into nude mice, and histopathology analysis. RT-PCR demonstrated that the cultured cells strongly expressed stemness-related genes, such as c-Myc, Sox-2, Nanog, Oct 4A, ABCG2, BMI-1, CK-18, Nestin and β-actin. The expression of surface markers CD24, CD133, CD47, CD29, CD44, CXCR4, SSEA3 and SSEA4, CD24, and CD133 and chemokine markers such as CXCR4 were measured by flow cytometry. Then the double percentage of CD133+CXCR4+ cells constituted 7.2% and 9.3% in EC cells originated from two different patients, respectively. The CD133+CXCR4+ primary endometrial cancer cells grew faster, exhibited high expression of mRNA of stemness-related genes, produced more spheres, and had higher clonogenic ability than other subpopulations. They are also more resistant to anti-cancer drugs than other subpopulations. These findings indicate that CD133+CXCR4+ cells may possess some characteristics of CSCs in primary endometrial cancer. These cell surface markers may be useful for the development of drugs against CSC molecular targets or as a predictive marker for poor prognosis in primary endometrial cancer.

Murine hepatocellular carcinoma derived stem cells reveal epithelial-to-mesenchymal plasticity

AIM

To establish a model to enrich and characterize stem-like cells from murine normal liver and hepatocellular carcinoma (HCC) cell lines and to further investigate stem-like cell association with epithelial-to-mesenchymal transition (EMT).

METHODS

In this study, we utilized a stem cell conditioned serum-free medium to enrich stem-like cells from mouse HCC and normal liver cell lines, Hepa 1-6 and AML12, respectively. We isolated the 3-dimensional spheres and assessed their stemness characteristics by evaluating the RNA levels of stemness genes and a cell surface stem cell marker by quantitative reverse transcriptase-PCR (qRT-PCR). Next, we examined the relationship between stem cells and EMT using qRT-PCR.

RESULTS

Three-dimensional spheres were enriched by culturing murine HCC and normal hepatocyte cell lines in stem cell conditioned serum-free medium supplemented with epidermal growth factor, basic fibroblast growth factor and heparin sulfate. The 3-dimensional spheres had enhanced stemness markers such as Klf4 and Bmi1 and hepatic cancer stem cell (CSC) marker Cd44 compared to parental cells grown as adherent cultures. We report that epithelial markers E-cadherin and ZO-1 were downregulated, while mesenchymal markers Vimentin and Fibronectin were upregulated in 3-dimensional spheres. The 3-dimensional spheres also exhibited changes in expression of Snai, Zeb and Twist family of EMT transcription factors.

CONCLUSION

Our novel method successfully enriched stem-like cells which possessed an EMT phenotype. The isolation and characterization of murine hepatic CSCs could establish a precise target for the development of more effective therapies for HCC.

The importance of regulatory ubiquitination in cancer and metastasis

Ubiquitination serves as a degradation mechanism of proteins, but is involved in additional cellular processes such as activation of NFκB inflammatory response and DNA damage repair. We highlight the E2 ubiquitin conjugating enzymes, E3 ubiquitin ligases and Deubiquitinases that support the metastasis of a plethora of cancers. E3 ubiquitin ligases also modulate pluripotent cancer stem cells attributed to chemotherapy resistance. We further describe mutations in E3 ubiquitin ligases that support tumor proliferation and adaptation to hypoxia. Thus, this review describes how tumors exploit members of the vast ubiquitin signaling pathways to support aberrant oncogenic signaling for survival and metastasis.

Epithelial-to-mesenchymal plasticity of cancer stem cells: therapeutic targets in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains one of the most common and lethal malignancies worldwide despite the development of various therapeutic strategies. A better understanding of the mechanisms responsible for HCC initiation and progression is essential for the development of more effective therapies. The cancer stem cell (CSC) model has provided new insights into the development and progression of HCC. CSCs are specialized tumor cells that are capable of self-renewal and have long-term repopulation potential. As they are important mediators of tumor proliferation, invasion, metastasis, therapy resistance, and cancer relapse, the selective targeting of this crucial population of cells has the potential to improve HCC patient outcomes and survival. In recent years, the role of epithelial-to-mesenchymal transition (EMT) in the advancement of HCC has gained increasing attention. This multi-step reprograming process resulting in a phenotype switch from an epithelial to a mesenchymal cellular state has been closely associated with the acquisition of stem cell-like attributes in tumors. Moreover, CSC mediates tumor metastasis by maintaining plasticity to transition between epithelial or mesenchymal states. Therefore, understanding the molecular mechanisms of the reprograming switches that determine the progression through EMT and generation of CSC is essential for developing clinically relevant drug targets. This review provides an overview of the proposed roles of CSC in HCC and discusses recent results supporting the emerging role of EMT in facilitating hepatic CSC plasticity. In particular, we discuss how these important new insights may facilitate rational development of combining CSC- and EMT-targeted therapies in the future.

Anti-tumoral effect of desmethylclomipramine in lung cancer stem cells

Lung cancer is the most feared of all cancers because of its heterogeneity and resistance to available treatments. Cancer stem cells (CSCs) are the cell population responsible for lung cancer chemoresistance and are a very good model for testing new targeted therapies. Clomipramine is an FDA-approved antidepressant drug, able to inhibit in vitro the E3 ubiquitin ligase Itch and potentiate the pro-apoptotic effects of DNA damaging induced agents in several cancer cell lines. Here, we investigated the potential therapeutic effect of desmethylclomipramine (DCMI), the active metabolite of Clomipramine, on the CSCs homeostasis. We show that DCMI inhibits lung CSCs growth, decreases their stemness potential and increases the cytotoxic effect of conventional chemotherapeutic drugs. Being DCMI an inhibitor of the E3 ubiquitin ligase Itch, we also verified the effect of Itch deregulation on CSCs survival. We found that the siRNA-mediated depletion of Itch induces similar anti-proliferative effects on lung CSCs, suggesting that DCMI might exert its effect, at least in part, by inhibiting Itch. Notably, Itch expression is a negative prognostic factor in two primary lung tumors datasets, supporting the potential clinical relevance of Itch inhibition to circumvent drug resistance in the treatment of lung cancer.

Tyr1068-phosphorylated epidermal growth factor receptor (EGFR) predicts cancer stem cell targeting by erlotinib in preclinical models of wild-type EGFR lung cancer

Tyrosine kinase inhibitors (TKIs) have shown strong activity against non-small-cell lung cancer (NSCLC) patients harboring activating epidermal growth factor receptor (EGFR) mutations. However, a fraction of EGFR wild-type (WT) patients may have an improvement in terms of response rate and progression-free survival when treated with erlotinib, suggesting that factors other than EGFR mutation may lead to TKI sensitivity. However, at present, no sufficiently robust clinical or biological parameters have been defined to identify WT-EGFR patients with greater chances of response. Therapeutics validation has necessarily to focus on lung cancer stem cells (LCSCs) as they are more difficult to eradicate and represent the tumor-maintaining cell population. Here, we investigated erlotinib response of lung CSCs with WT-EGFR and identified EGFR phosphorylation at tyrosine1068 (EGFRtyr1068) as a powerful biomarker associated with erlotinib sensitivity both in vitro and in preclinical CSC-generated xenografts. In contrast to the preferential cytotoxicity of chemotherapy against the more differentiated cells, in EGFRtyr1068 cells, erlotinib was even more active against the LCSCs compared with their differentiated counterpart, acquiring potential value as CSC-directed therapeutics in the context of WT-EGFR lung cancer. Although tumor growth was inhibited to a similar extent during erlotinib or chemotherapy administration to responsive tumors, erlotinib proved superior to chemotherapy in terms of higher tolerability and reduced tumor aggressiveness after treatment suspension, substantiating the possibility of preferential LCSC targeting, both in adenocarcinoma (ADC) and squamous cell carcinoma (SCC) tumors. We conclude that EGFRtyr1068 may represent a potential candidate biomarker predicting erlotinib response at CSC-level in EGFR-WT lung cancer patients. Finally, besides its invariable association with erlotinib sensitivity in EGFR-WT lung CSCs, EGFRtyr1068 was associated with EGFR-sensitizing mutations in cell lines and patient tumors, with relevant diagnostic, clinical and therapeutic implications.

Phenotypic screening in cancer drug discovery - past, present and future

There has been a resurgence of interest in the use of phenotypic screens in drug discovery as an alternative to target-focused approaches. Given that oncology is currently the most active therapeutic area, and also one in which target-focused approaches have been particularly prominent in the past two decades, we investigated the contribution of phenotypic assays to oncology drug discovery by analysing the origins of all new small-molecule cancer drugs approved by the US Food and Drug Administration (FDA) over the past 15 years and those currently in clinical development. Although the majority of these drugs originated from target-based discovery, we identified a significant number whose discovery depended on phenotypic screening approaches. We postulate that the contribution of phenotypic screening to cancer drug discovery has been hampered by a reliance on 'classical' nonspecific drug effects such as cytotoxicity and mitotic arrest, exacerbated by a paucity of mechanistically defined cellular models for therapeutically translatable cancer phenotypes. However, technical and biological advances that enable such mechanistically informed phenotypic models have the potential to empower phenotypic drug discovery in oncology.

Cancer stem cells and cisplatin-resistant cells isolated from non-small-lung cancer cell lines constitute related cell populations

Lung cancer is the top cause of cancer-related deceases. One of the reasons is the development of resistance to the chemotherapy treatment. In particular, cancer stem cells (CSCs), can escape treatment and regenerate the bulk of the tumor. In this article, we describe a comparison between cancer cells resistant to cisplatin and CSCs, both derived from the non-small-cell lung cancer cell lines H460 and A549. Cisplatin-resistant cells were obtained after a single treatment with the drug. CSCs were isolated by culture in defined media, under nonadherent conditions. The isolated CSCs were clonogenic, could be differentiated into adherent cells and were less sensitive to cisplatin than the original cells. Cisplatin resistant and CSCs were able to generate primary tumors and to metastasize when injected into immunodeficient Nu/Nu mice, although they formed smaller tumors with a larger latency than untreated cells. Notably, under appropriated proportions, CSCs synergized with differentiated cells to form larger tumors. CSCs also showed increased capacity to induce angiogenesis in Nu/Nu mice. Conversely, H460 cisplatin-resistant cells showed increased tendency to develop bone metastasis. Gene expression analysis showed that several genes involved in tumor development and metastasis (EGR1, COX2, MALAT1, AKAP12, ADM) were similarly induced in CSC and cisplatin-resistant H460 cells, in agreement with a close similarity between these two cell populations. Cells with the characteristic growth properties of CSCs were also isolated from surgical samples of 18 out of 44 lung cancer patients. A significant correlation (P = 0.028) was found between the absence of CSCs and cisplatin sensitivity.