Role of the wnt signaling pathway and lung cancer

Natural compounds: Wnt pathway inhibitors with therapeutic potential in lung cancer

The Wnt/β-catenin pathway is abnormally activated in most lung cancer tissues and considered to be an accelerator of carcinogenesis and lung cancer progression, which is closely related to increased morbidity rates, malignant progression, and treatment resistance. Although targeting the canonical Wnt/β-catenin pathway shows significant potential for lung cancer therapy, it still faces challenges owing to its complexity, tumor heterogeneity and wide physiological activity. Therefore, it is necessary to elucidate the role of the abnormal activation of the Wnt/β-catenin pathway in lung cancer progression. Moreover, Wnt inhibitors used in lung cancer clinical trials are expected to break existing therapeutic patterns, although their adverse effects limit the treatment window. This is the first study to summarize the research progress on various compounds, including natural products and derivatives, that target the canonical Wnt pathway in lung cancer to develop safer and more targeted drugs or alternatives. Various natural products have been found to inhibit Wnt/β-catenin in various ways, such as through upstream and downstream intervention pathways, and have shown encouraging preclinical anti-tumor efficacy. Their diversity and low toxicity make them a popular research topic, laying the foundation for further combination therapies and drug development.

Therapeutic Targeting of Regulated Signaling Pathways of Non-Small Cell Lung Carcinoma

Non-small cell lung carcinoma (NSCLC) is the most common cancer globally. Phytochemicals and small molecule inhibitors significantly prevent varying types of cancers, including NSCLC. These therapeutic molecules serve as important sources for new drugs that interfere with cellular proliferation, apoptosis, metastasis, and angiogenesis by regulating signaling pathways. These molecules affect several cellular signaling cascades, including p53, NF-κB, STAT3, RAS, MAPK/ERK, Wnt, and AKT/PI3K, and are thus implicated in the therapeutic management of cancers. This review aims to describe the bioactive compounds and small-molecule inhibitors, their anticancer action, and targeting cellular signaling cascades in NSCLC. We highlighted the therapeutic potential of Epigallocatechin gallate (EGCG), Perifosine, ABT-737, Thymoquinine, Quercetin, Venetoclax, Gefitinib, and Genistein. These compounds are implicated in the therapeutic management of NSCLC. This review further offers deeper mechanistic insights into different signaling pathways that could be targeted for NSCLC therapy by phytochemicals and small-molecule inhibitors.

Investigating regulated signaling pathways in therapeutic targeting of non-small cell lung carcinoma

Non-small cell lung carcinoma (NSCLC) is the most common malignancy worldwide. The signaling cascades are stimulated via genetic modifications in upstream signaling molecules, which affect apoptotic, proliferative, and differentiation pathways. Dysregulation of these signaling cascades causes cancer-initiating cell proliferation, cancer development, and drug resistance. Numerous efforts in the treatment of NSCLC have been undertaken in the past few decades, enhancing our understanding of the mechanisms of cancer development and moving forward to develop effective therapeutic approaches. Modifications of transcription factors and connected pathways are utilized to develop new treatment options for NSCLC. Developing designed inhibitors targeting specific cellular signaling pathways in tumor progression has been recommended for the therapeutic management of NSCLC. This comprehensive review provided deeper mechanistic insights into the molecular mechanism of action of various signaling molecules and their targeting in the clinical management of NSCLC.

Clinical utility of cerebrospinal fluid-derived circular RNAs in lung adenocarcinoma patients with brain metastases

Background

Free circular RNAs(circRNAs) escaping from primary lesion of cancer to brain are strictly regulated by blood–brain barrier and therefore cerebrospinal fluid (CSF) circRNAs have potential advantage in exploring biomarkers and mechanism of brain metastasis in lung cancer.

Methods

We collected paired cerebrospinal fluid, plasma and tumor tissues from 21 lung adenocarcinoma (ADC) patients with brain metastases (BM) and performed RNA sequencing.

Results

Compared to tumor tissue and plasma, circRNAs in CSF were characterized by lower number of spieces but higher abundance. Notably, CSF-circRNAs displayed high heterogeneity among different BM lung ADC patients. A total of 60 CSF-circRNAs was identified and associated with shorten overall survival. The circRNA-miRNA-mRNA network analysis revealed that the 60 CSF-circRNAs involved in cancer-associated pathways, and five of them showed strong association with WNT signaling pathway. Validation by RT-PCR of CSF and in vitro experiments of the five candidate circRNAs support their potential roles in cell proliferation and invasion.

Conclusions

In summary, our results depicted the heterogenous CSF-circRNAs profiles among BM lung ADC and implied that CSF-circRNAs may be promising prognosis-related biomarkers.

Tumor Endothelial Marker 8 Promotes Proliferation and Metastasis via the Wnt/β-Catenin Signaling Pathway in Lung Adenocarcinoma

Tumor endothelial marker 8 (TEM8), also known as ANTXR1, was highly expressed in cancers, and was identified as a biomarker for early diagnosis and prognosis in some cancers. However, the clinical role and molecular mechanisms of TEM8 in lung adenocarcinoma (LUAD) are still unclear. The present study aimed to explore its clinical value and the molecular mechanisms of TEM8 underlying the progression of LUAD. Our study found the elevation of TEM8 in LUAD cell lines and tissues. What’s more, we observed that the TEM8 expression level was associated with tumor size, primary tumor, and AJCC stage, and LUAD patients with high TEM8 expression usually have a poor prognosis. Then, we conducted a series of experiments by the strategy of loss-of-function and gain-of-function, and our results suggested that the knockdown of TEM8 suppressed proliferation, migration, and invasion and induced apoptosis in LUAD whereas overexpression of TEM8 had the opposite effect. Molecular mechanistic investigation showed that TEM8 exerted its promoting effects mainly through activating the Wnt/β-catenin signaling pathway. In short, our findings suggested that TEM8 played a crucial role in the progression of LUAD by activating the Wnt/β-catenin signaling pathway and could serve as a potential therapeutic target for LUAD.

Clinicopathological and prognostic significance of circRNAs in lung cancer: A systematic review and meta-analysis

BACKGROUND

Circular RNAs (circRNAs) regulate multiple pathways during lung cancer pathogenesis. Apart from functional significance, many circRNAs have been shown to be associated with clinicopathological characteristics and predict lung cancer prognosis. Our aim is to summarize the expanding knowledge of clinical roles of circRNAs in lung cancer.

METHODS

A thorough search of literature was conducted to identify articles about the correlation between circRNA expression and its prognostic and clinicopathological values. Biological mechanisms were summarized.

RESULTS

This study included 35 original articles and 32 circRNAs with prognostic roles for lung cancer. Increased expression of 25 circRNAs and decreased expression of 7 circRNAs predicted poor prognosis. For non-small cell lung cancer, changes of circRNAs were correlated with tumor size, lymph node metastasis, distant metastasis, tumor node metastasis (TNM) stage, and differentiation, indicating the major function of circRNAs is to promote lung cancer invasion and migration. Particularly, meta-analysis of ciRS-7, hsa_circ_0020123, hsa_circ_0067934 showed increase of the 3 circRNAs was associated with positive lymph node metastasis. Increase of ciRS-7 and hsa_circ_0067934 was also related with advanced TNM stage. The biological effects depend on the general function of circRNA as microRNA sponge.

CONCLUSIONS

CircRNAs have the potential to function as prognostic markers and are associated with lung cancer progression and metastasis.

Expression profiles and prognostic significance of WNT family members in glioma via bioinformatic analysis

AIMS

The dysregulation and essential role of WNTs in glioma have been widely implicated. However, there is a paucity of literature on the expression status of all the 19 WNTs in glioma. Our study was aimed to evaluate the expression and prognostic values of the 19 WNTs in glioma.

METHODS

mRNA expression and clinical data were retrieved from the Cancer Genome Atlas (TCGA) database, Chinese Glioma Genome Atlas (CGGA), GTEx and ONCOMINE databases. The 50 frequent neighbor genes of WNT5A and WNT10B were shown with PPI network, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses.

RESULTS

We found that the mRNA expression of WNT5A was significantly higher in glioma; however, the WNT10B expression was significantly lower in glioma. Furthermore, the expression of WNT5A and WNT10B was associated with the clinicopathology of glioma. The survival analysis revealed that the higher expressions of WNT5A and WNT16 were associated poor overall survival (OS) in patients with glioma. Conversely, overexpression of WNT3, WNT5B, and WNT10B was associated with better OS. Finally, Go and KEGG analysis revealed WNT5A was associated with multiple signal translations, and crucial oncogenes (EGFR and MDM2) and 2 important tumor suppressors (PTEN and IKN4a/ARF) were found closely correlated with WNT5A in glioma.

CONCLUSION

Among 19WNTs, WNT5A can serve as a candidate to diagnose and therapy glioma, while WNT10B might be valuable for anti-glioma research. The presumed direction was provided to explore the relation of WNTs signal and multiple pathways in glioma.

Identification of novel transcription factor-microRNA-mRNA co-regulatory networks in pulmonary large-cell neuroendocrine carcinoma

Background

Large cell neuroendocrine carcinoma (LCNEC) of the lung is a rare neuroendocrine neoplasm. Previous studies have shown that microRNAs (miRNAs) are widely involved in tumor regulation through targeting critical genes. However, it is unclear which miRNAs play vital roles in the pathogenesis of LCNEC, and how they interact with transcription factors (TFs) to regulate cancer-related genes.

Methods

To determine the novel TF-miRNA-target gene feed-forward loop (FFL) model of LCNEC, we integrated multi-omics data from Gene Expression Omnibus (GEO), Transcriptional Regulatory Relationships Unraveled by Sentence-Based Text Mining (TRRUST), Transcriptional Regulatory Element Database (TRED), and The experimentally validated microRNA-target interactions database (miRTarBase database). First, expression profile datasets for mRNAs (GSE1037) and miRNAs (GSE19945) were downloaded from the GEO database. Overlapping differentially expressed genes (DEGs) and differentially expressed miRNAs (DEMs) were identified through integrative analysis. The target genes of the FFL were obtained from the miRTarBase database, and the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses were performed on the target genes. Then, we screened for key miRNAs in the FFL and performed gene regulatory network analysis based on key miRNAs. Finally, the TF-miRNA-target gene FFLs were constructed by the hypergeometric test.

Results

A total of 343 DEGs and 60 DEMs were identified in LCNEC tissues compared to normal tissues, including 210 down-regulated and 133 up-regulated genes, and 29 down-regulated and 31 up-regulated miRNAs. Finally, the regulatory network of TF-miRNA-target gene was established. The key regulatory network modules included ETS1-miR195-CD36, TAOK1-miR7-1-3P-GRIA1, E2F3-miR195-CD36, and TEAD1-miR30A-CTHRC1.

Conclusions

We constructed the TF-miRNA-target gene regulatory network, which is helpful for understanding the complex LCNEC regulatory mechanisms.

Genetic Variants in the Wingless Antagonist Genes (sFRP, DKK, and Axin2) Predict the Overall Survival and Prognosis of North Indian Lung Cancer Patients Treated with Platinum-Based Doublet Chemotherapy

Background: To investigate the prognostic implication of genetic variants within the wingless (Wnt) antagonist genes (DKK, sFRP, and Axin2) in North Indian lung cancer patients. Materials and Methods: A total of 212 subjects were genotyped using polymerase chain reaction-restriction fragment length polymorphism technique for 18 polymorphic sites in DKK4, DKK3, DKK2, sFRP3, sFRP4, and Axin2. Overall survival (OS) was estimated using the Kaplan-Meier survival analysis, and adjusted hazard ratio (HR) was obtained using the Cox regression method. Results: It was observed that the unfavorable genotypes of the three DKK2 variants collectively (rs447372, rs419558, and rs17037102) exhibited a highly decreased rate of death (adjusted HR = 0.37, p = 0.03). Adenocarcinoma (ADCC) patients carrying the heterozygous (CT) genotype for DKK4 rs2073664 showed a better OS compared with wild genotype (log rank p = 0.01). The two exonic variants (148 and 1386) of Axin2 gene showed contrasting results, where the ADCC subjects having TT genotype for Axin2 148 showed a better prognosis (adjusted HR = 0.48, p = 0.003) and those with TT genotype for Axin2 1386 showed a poor prognosis in small-cell lung carcinoma patients (adjusted HR = 2.33, p = 0.02). The intronic Axin2 1712 + 19 variant on the other hand indicated a highly increased death risk in ADCC patients with GG genotype. Survival tree analysis depicted DKK4 rs2073664 as the major contributor in predicting the survival of the lung cancer patients. Node 3 exhibited the lowest death rate (HR = 0.04, p = 0.008) and better median survival time (9 months vs. 3 months) when compared with reference node. Conclusions: A cumulative effect of three variants of DKK2 gene along with DKK4 rs2073664 can jointly predict the survival as shown by tree analysis.

Down-regulation of FOXR2 inhibits non-small cell lung cancer cell proliferation and invasion through the Wnt/β-catenin signaling pathway

Forkhead box R2 (FOXR2), a new member of the FOX family, is an important player in a wide range of cellular processes such as proliferation, migration, differentiation and apoptosis. Recently, FOXR2 has been reported to be implicated in cancer development. However, the biological functions of FOXR2 in non-small cell lung cancer (NSCLC) remain unclear. In this study, we investigated the specific role of FOXR2 in NSCLC. The results showed that down-regulation of FOXR2 significantly inhibited NSCLC cell proliferation and invasion in vitro and suppressed NSCLC cell growth and metastasis in vivo. In addition, the decrease in FOXR2 expression markedly reduced the protein levels of β-catenin, cyclinD1 and c-Myc and hence inactivated the Wnt/β-catenin pathway in NSCLC cells. Taken together, we concluded that FOXR2 might be considered as a promising therapeutic target for NSCLC treatment.

Phosphodiesterase 10A is overexpressed in lung tumor cells and inhibitors selectively suppress growth by blocking β-catenin and MAPK signaling

Phosphodiesterase 10A (PDE10) is a cyclic nucleotide (e.g. cGMP) degrading enzyme highly expressed in the brain striatum where it plays an important role in dopaminergic neurotransmission, but has limited expression and no known physiological function outside the central nervous system. Here we report that PDE10 mRNA and protein levels are strongly elevated in human non-small cell lung cancer cells and lung tumors compared with normal human airway epithelial cells and lung tissue, respectively. Genetic silencing of PDE10 or inhibition by small molecules such as PQ10 was found to selectively inhibit the growth and colony formation of lung tumor cells. PQ10 treatment of lung tumor cells rapidly increased intracellular cGMP levels and activated cGMP-dependent protein kinase (PKG) at concentrations that inhibit lung tumor cell growth. PQ10 also increased the phosphorylation of β-catenin and reduced its levels, which paralleled the suppression of cyclin D1 and survivin but preceded the activation of PARP and caspase cleavage. PQ10 also suppressed RAS-activated RAF/MAPK signaling within the same concentration range and treatment period as required for cGMP elevation and PKG activation. These results show that PDE10 is overexpressed during lung cancer development and essential for lung tumor cell growth in which inhibitors can selectively induce apoptosis by increasing intracellular cGMP levels and activating PKG to suppress oncogenic β-catenin and MAPK signaling.

'WNT-er is coming': WNT signalling in chronic lung diseases

Chronic lung diseases represent a major public health problem with only limited therapeutic options. An important unmet need is to identify compounds and drugs that target key molecular pathways involved in the pathogenesis of chronic lung diseases. Over the last decade, there has been extensive interest in investigating Wingless/integrase-1 (WNT) signalling pathways; and WNT signal alterations have been linked to pulmonary disease pathogenesis and progression. Here, we comprehensively review the cumulative evidence for WNT pathway alterations in chronic lung pathologies, including idiopathic pulmonary fibrosis, pulmonary arterial hypertension, asthma and COPD. While many studies have focused on the canonical WNT/β-catenin signalling pathway, recent reports highlight that non-canonical WNT signalling may also significantly contribute to chronic lung pathologies; these studies will be particularly featured in this review. We further discuss recent advances uncovering the role of WNT signalling early in life, the potential of pharmaceutically modulating WNT signalling pathways and highlight (pre)clinical studies describing promising new therapies for chronic lung diseases.

Knockdown of CUL4B Suppresses the Proliferation and Invasion in Non-Small Cell Lung Cancer Cells

Cullin 4B (CUL4B), a scaffold protein that assembles CRL4B ubiquitin ligase complexes, was found to be overexpressed in many types of tumors. However, the expression pattern and role of CUL4B in non-small cell lung cancer (NSCLC) remain largely unknown. Therefore, in the present study, we investigated the role of CUL4B in NSCLC, and the underlying mechanism was also explored. Our results showed that CUL4B was highly expressed in NSCLC cell lines. Silencing CUL4B obviously inhibited proliferation and migration/invasion of NSCLC cells, and it also suppressed the epithelial–mesenchymal transition (EMT) progress in NSCLC cells. Furthermore, knockdown of CUL4B significantly inhibited the expression of β-catenin, cyclin D1, and c-Myc in NSCLC cells. Taken together, these results suggest that knockdown of CUL4B inhibited the proliferation and invasion through suppressing the Wnt/β-catenin signaling pathway in NSCLC cells. Therefore, CUL4B may represent a novel therapeutic target for the treatment of NSCLC.

Immune Modulation of the T Cell Response in Asthma through Wnt10b

Asthma is a chronic inflammatory disease, which is characterized by activation of CD4(+) T helper 2 cells orchestrating an allergic airway response. Whereas the role of Wnt family members in regulating T cell maintenance and maturation is established, their contribution to T cell activation in allergic asthma is not known. We hypothesized that Wnt10b plays a role in the modulation of the allergic airway response and affects T cell activation and polarization. Using an in vivo house dust mite asthma model, Wnt10b-deficient (Wnt10b(-/-)) mice were allergen-sensitized and inflammation, as well as T cell activation, was studied in vivo and in vitro. Wnt10b(-/-) mice exhibited an augmented inflammatory phenotype with an increase in eosinophils in the bronchoalveolar lavage and IL-4 and IL-13 in the lungs when compared with wild-type mice. In vitro studies confirmed an increased T helper type 2 polarization and increased T cell activation of Wnt10b(-/-) cells. Accordingly, the percentage of naive T cells was elevated by the addition of recombinant Wnt10b protein. Finally, Wnt10b(-/-) mice exhibited an increase in the percentage of effector T cells in the lungs after house dust mite sensitization, which indicated a heightened activation state, measured by an increased percentage of CD69(hi)CD11a(hi) cells. These findings suggest that Wnt10b plays an important role in regulating asthmatic airway inflammation through modification of the T cell response and is a prospective target in the disease process.

A Small-Molecule Antagonist of the β-Catenin/TCF4 Interaction Blocks the Self-Renewal of Cancer Stem Cells and Suppresses Tumorigenesis

Wnt/β-catenin signaling is a highly conserved pathway essential for embryogenesis and tissue homeostasis. However, deregulation of this pathway can initiate and promote human malignancies, especially of the colon and head and neck. Therefore, Wnt/β-catenin signaling represents an attractive target for cancer therapy. We performed high-throughput screening using AlphaScreen and ELISA techniques to identify small molecules that disrupt the critical interaction between β-catenin and the transcription factor TCF4 required for signal transduction. We found that compound LF3, a 4-thioureido-benzenesulfonamide derivative, robustly inhibited this interaction. Biochemical assays revealed clues that the core structure of LF3 was essential for inhibition. LF3 inhibited Wnt/β-catenin signals in cells with exogenous reporters and in colon cancer cells with endogenously high Wnt activity. LF3 also suppressed features of cancer cells related to Wnt signaling, including high cell motility, cell-cycle progression, and the overexpression of Wnt target genes. However, LF3 did not cause cell death or interfere with cadherin-mediated cell-cell adhesion. Remarkably, the self-renewal capacity of cancer stem cells was blocked by LF3 in concentration-dependent manners, as examined by sphere formation of colon and head and neck cancer stem cells under nonadherent conditions. Finally, LF3 reduced tumor growth and induced differentiation in a mouse xenograft model of colon cancer. Collectively, our results strongly suggest that LF3 is a specific inhibitor of canonical Wnt signaling with anticancer activity that warrants further development for preclinical and clinical studies as a novel cancer therapy.

Expression of WNT genes in cervical cancer-derived cells: Implication of WNT7A in cell proliferation and migration

According to the multifactorial model of cervical cancer (CC) causation, it is now recognized that other modifications, in addition to Human papillomavirus (HPV) infection, are necessary for the development of this neoplasia. Among these, it has been proposed that a dysregulation of the WNT pathway might favor malignant progression of HPV-immortalized keratinocytes. The aim of this study was to identify components of the WNT pathway differentially expressed in CC vs. non-tumorigenic, but immortalized human keratinocytes. Interestingly, WNT7A expression was found strongly downregulated in cell lines and biopsies derived from CC. Restoration of WNT7A in CC-derived cell lines using a lentiviral gene delivery system or after adding a recombinant human protein decreases cell proliferation. Likewise, WNT7A silencing in non-tumorigenic cells markedly accelerates proliferation. Decreased WNT7A expression was due to hypermethylation at particular CpG sites. To our knowledge, this is the first study reporting reduced WNT7A levels in CC-derived cells and that ectopic WNT7A restoration negatively affects cell proliferation and migration.

Myeloid cell RelA/p65 promotes lung cancer proliferation through Wnt/β-catenin signaling in murine and human tumor cells

Smoking is the most important risk factor for both lung cancer (LC) and chronic obstructive pulmonary disease. The aim of this study was to investigate the role of myeloid cell nuclear factor-κB in the regulation of tumor cell growth signaling. We subjected mice lacking myeloid RelA/p65 (rela(Δ-/-)) to a metastatic LC model. Cigarette smoke (CS) exposure significantly increased the proliferation of Lewis lung carcinoma cell tumors in wild-type mice. In CS-exposed rela(Δ-/-) mice, the tumor growth was largely inhibited. Transcriptome and pathway analysis of cancer tissue revealed a fundamental impact of myeloid cells on various growth signaling pathways, including the Wnt/β-catenin pathway. In conclusion, myeloid RelA/p65 is necessary to link smoke-induced inflammation with LC growth and has a role in the activation of Wnt/β-catenin signaling in tumor cells.

Non-small-cell lung cancer: molecular targeted therapy and personalized medicine - drug resistance, mechanisms, and strategies

Targeted therapies for cancer bring the hope of specific treatment, providing high efficacy and in some cases lower toxicity than conventional treatment. Although targeted therapeutics have helped immensely in the treatment of several cancers, like chronic myelogenous leukemia, colon cancer, and breast cancer, the benefit of these agents in the treatment of lung cancer remains limited, in part due to the development of drug resistance. In this review, we discuss the mechanisms of drug resistance and the current strategies used to treat lung cancer. A better understanding of these drug-resistance mechanisms could potentially benefit from the development of a more robust personalized medicine approach for the treatment of lung cancer.

Wnt signaling in lung organogenesis

Reporter transgene, knockout, and misexpression studies support the notion that Wnt/beta-catenin signaling regulates aspects of branching morphogenesis, regional specialization of the epithelium and mesenchyme, and establishment of progenitor cell pools. As demonstrated for other foregut endoderm-derived organs, beta-catenin and the Wnt/beta-catenin signaling pathway contribute to control of cellular proliferation, differentiation and migration. However, the contribution of Wnt/beta-catenin signaling to these processes is shaped by other signals impinging on target tissues. In this review, we will concentrate on roles for Wnt/beta-catenin in respiratory system development, including segregation of the conducting airway and alveolar compartments, specialization of the mesenchyme, and establishment of tracheal asymmetries and tracheal glands.

[The research progress about Wnt pathway of lung cancer stem cells]

Being the most critical signaling molecule in the Wnt pathway, the Wnt/β-catenin signaling pathway plays an important role in the maintenance of the cell proliferation and clone formation of lung cancer stem cells. Since it is closely related to the WNT pathway, the proliferation of lung cancer stem cells can be restrained by blocking the WNT pathway or influencing its key protein. Such method provides a new method for the treatment of lung cancer. By summarizing the state of-the-art research of lung cancer stem cells and the Wnt pathway from 2005 to 2010, their relationship is investigated.

Heterogeneous expression of Wnt signal molecules in parental HepG2 cells and HepG2 colony-forming cells

AIM: To investigate the heterogeneous expression of Wnt signal molecules in HepG2 cells with different proliferative ability.

METHODS: The soft agar colony formation assay was used to separate HepG2 colony-forming cells. The mRNA expression and protein expression and distribution of β-catenin and COX-2 in parental HepG2 cells and HepG2 colony-forming cells were detected by RT-PCR, Western blotting and immunochemistry, respectively.

RESULTS: The expression levels of β-catenin mRNA and protein in HepG2 colony-forming cells were significantly higher than those in parental HepG2 cells (0.905 vs 0.549; 1.021 vs 0.700; both P < 0.05). β-catenin was mainly localized in the cytoplasm in parental HepG2 cells and in the nucleus in HepG2 colony-forming cells. The expression levels of COX-2 mRNA and protein in parental HepG2 cells were significantly higher than those in HepG2 colony-forming cells (0.857 vs 0.527; 0.731 vs 0.434; both P < 0.05). Immunochemistry analysis showed that most HepG2 cells were positive for COX-2.

CONCLUSION: β-catenin and COX-2 may be closely related to the degree of differentiation of hepatocellular carcinoma. The expression patterns of β-catenin and COX-2 in parental HepG2 cells and HepG2 colony-forming cells imply that HepG2 colony-forming cells have the characteristics of liver cancer stem cells.

Gene Expression Studies Demonstrate that the K-ras/Erk MAP Kinase Signal Transduction Pathway and Other Novel Pathways Contribute to the Pathogenesis of Cumene-induced Lung Tumors

National Toxicology Program (NTP) inhalation studies demonstrated that cumene significantly increased the incidence of alveolar/bronchiolar adenomas and carcinomas in B6C3F1 mice. Cumene or isopropylbenzene is a component of crude oil used primarily in the production of phenol and acetone. The authors performed global gene expression analysis to distinguish patterns of gene regulation between cumene-induced tumors and normal lung tissue and to look for patterns based on the presence or absence of K- ras and p53 mutations in the tumors. Principal component analysis segregated the carcinomas into groups with and without K- ras mutations, but failed to separate the tumors based on p53 mutation status. Expression of genes associated with the Erk MAP kinase signaling pathway was significantly altered in carcinomas with K- ras mutations compared to tumors without K- ras mutations or normal lung. Gene expression analysis also suggested that cumene-induced carcinomas with K- ras mutations have greater malignant potential than those without mutations. In addition, significance analysis of function and expression (SAFE) demonstrated expression changes of genes regulated by histone modification in carcinomas with K- ras mutations. The gene expression analysis suggested the formation of alveolar/bronchiolar carcinomas in cumene-exposed mice typically involves mutation of K- ras, which results in increased Erk MAP kinase signaling and modification of histones.