Delta-crystallin enhancer binding factor 1 controls the epithelial to mesenchymal transition phenotype and resistance to the epidermal growth factor receptor inhibitor erlotinib in human head and neck squamous cell carcinoma lines

SE-lncRNAs in Cancer: Classification, Subcellular Localisation, Function and Corresponding TFs

Emerging evidence highlights certain long noncoding RNAs (lncRNAs) transcribed from or interacting with super-enhancer (SE) regulatory elements. These lncRNAs, known as SE-lncRNAs, are strongly linked to cancer and regulate cancer progression through multiple interactions with downstream targets. The expression of SE-lncRNAs is controlled by various transcription factors (TFs), and dysregulation of these TFs can contribute to cancer development. In this review, we discuss the characteristics, classification and subcellular distribution of SE-lncRNAs and summarise the role of key TFs in the transcription and regulation of SE-lncRNAs. Moreover, we examine the distinct functions and potential mechanisms of SE-lncRNAs in cancer progression.

Transcription Factors and Markers Related to Epithelial-Mesenchymal Transition and Their Role in Resistance to Therapies in Head and Neck Cancers

Head and neck cancers (HNCs) are heterogeneous and aggressive tumors of the upper aerodigestive tract. Although various histological types exist, the most common is squamous cell carcinoma (HNSCC). The incidence of HNSCC is increasing, making it an important public health concern. Tumor resistance to contemporary treatments, namely, chemo- and radiotherapy, and the recurrence of the primary tumor after its surgical removal cause huge problems for patients. Despite recent improvements in these treatments, the 5-year survival rate is still relatively low. HNSCCs may develop local lymph node metastases and, in the most advanced cases, also distant metastases. A key process associated with tumor progression and metastasis is epithelial-mesenchymal transition (EMT), when poorly motile epithelial tumor cells acquire motile mesenchymal characteristics. These transition cells can invade different adjacent tissues and finally form metastases. EMT is governed by various transcription factors, including the best-characterized TWIST1 and TWIST2, SNAIL, SLUG, ZEB1, and ZEB2. Here, we highlight the current knowledge of the process of EMT in HNSCC and present the main protein markers associated with it. This review focuses on the transcription factors related to EMT and emphasizes their role in the resistance of HNSCC to current chemo- and radiotherapies. Understanding the role of EMT and the precise molecular mechanisms involved in this process may help with the development of novel anti-cancer therapies for this type of tumor.

Multi-kinase compensation rescues EGFR knockout in a cell line model of head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is a debilitating disease with poor survival rates. While the epidermal growth factor receptor (EGFR)-targeting antibody Cetuximab is approved for treatment, responses are limited and the molecular mechanisms driving resistance remain incompletely understood.

METHODS

To better understand how cells survive without EGFR activity, we developed an EGFR knockout derivative of the UM-SCC-92 cell line using CRISPR/Cas9 technology. We then characterized changes to the transcriptome with RNAseq and changes in response to kinase inhibitors with resazurin cell viability assays. Finally, we tested if inhibitors with activity in the EGFR knockout model also had synergistic activity in combination with EGFR inhibitors in either wild type UM-SCC-92 cells or a known Cetuximab-resistant model.

RESULTS

Functional and molecular analysis showed that knockout cells had decreased cell proliferation, upregulation of FGFR1 expression, and an enhanced mesenchymal phenotype. In fact, expression of common EMT genes including VIM, SNAIL1, ZEB1 and TWIST1 were all upregulated in the EGFR knockout. Surprisingly, EGFR knockout cells were resistant to FGFR inhibitor monotherapies, but sensitive to combinations of FGFR and either XIAP or IGF-1R inhibitors. Accordingly, both wild type UM-SCC-92 and Cetuximab-resistant UM-SCC-104 cells with were sensitive to combined inhibition of EGFR, FGFR and either XIAP or IGF-1R.

CONCLUSIONS

These data offer insights into EGFR inhibitor resistance and show that resistance to EGFR knockout likely occurs through a complex network of kinases. Future studies of cetuximab-resistant HNSCC tumors are warranted to determine if this EMT phenotype and/or multi-kinase resistance is observed in patients.

Comprehensive Analysis of N6-Methyladenosine-Related lncRNA Signature for Predicting Prognosis and Immune Cell Infiltration in Patients with Colorectal Cancer

Background

Colorectal cancer (CRC) is the third most common tumor worldwide. Aberrant N6-methyladenosine (m6A) modification can influence the progress of the CRC. Additionally, long noncoding RNA (lncRNA) plays a critical role in CRC and has a close relationship with m6A modification. However, the prognostic potential of m6A-related lncRNAs in CRC patients still remains to be clarified.

Methods

We use “limma” R package, “glmnet” R package, and “survival” R package to screen m6A-related-lncRNAs with prognostic potential. Then, we comprehensively analysed and integrated the related lncRNAs in different TNM stages from TCGA database using the LASSO Cox regression. Meanwhile, the relationship between functional enrichment of m6A-related lncRNAs and immune microenvironment in CRC was also investigated using the TCGA database. A prognostic model was constructed and validated to determine the association between m6A-related lncRNAs in different TNM stages and the prognosis of CRC.

Result

We demonstrated that three related m6A lncRNAs in different TNM stages were associated with the prognosis of CRC patients. Patients from the TCGA database were classified into the low-risk and the high-risk groups based on the expression of these lncRNAs. The patients in the low-risk group had longer overall survival than the patients in the high-risk group (P < 0.001). We further constructed and validated a prognostic nomogram based on these genes with a C-index of 0.80. The receiver operating characteristic curves confirmed the predictive capacity of the model. Meanwhile, we also found that the low-risk group has the correlation with the dendritic cell (DC). Finally, we discovered the relationship between the m6A regulators and the three lncRNAs.

Conclusion

The prognostic model based on three m6A-related lncRNAs exhibits superior predictive performance, providing a novel prognostic model for the clinical evaluation of CRC patients.

Oncogenic functions of ZEB1 in pediatric solid cancers: interplays with microRNAs and long noncoding RNAs

The transcription factor Zinc finger E-box binding 1 (ZEB1) displays a range of regulatory activities in cell function and embryonic development, including driving epithelial-mesenchymal transition. Several aspects of ZEB1 function can be regulated by its functional interactions with noncoding RNA types, namely microRNAs (miRNAs) and long noncoding RNAs (lncRNAs). Increasing evidence indicates that ZEB1 importantly influences cancer initiation, tumor progression, metastasis, and resistance to treatment. Cancer is the main disease-related cause of death in children and adolescents. Although the role of ZEB1 in pediatric cancer is still poorly understood, emerging findings have shown that it is expressed and regulates childhood solid tumors including osteosarcoma, retinoblastoma, neuroblastoma, and central nervous system tumors. Here, we review the evidence supporting a role for ZEB1, and its interplays with miRNAs and lncRNAs, in pediatric cancers.

Predictive Value of EGFR-PI3K-AKT-mTOR-Pathway Inhibitor Biomarkers for Head and Neck Squamous Cell Carcinoma: A Systematic Review

BACKGROUND

Understanding molecular pathogenesis of head and neck squamous cell carcinomas (HNSCC) has considerably improved in the last decades. As a result, novel therapeutic strategies have evolved, amongst which are epidermal growth factor receptor (EGFR)-targeted therapies. With the exception of cetuximab, targeted therapies for HNSCC have not yet been introduced into clinical practice. One important aspect of new treatment regimes in clinical practice is presence of robust biomarkers predictive for therapy response.

METHODS

We performed a systematic search in PubMed, Embase and the Cochrane library. Articles were included if they investigated a biomarker for targeted therapy in the EGFR-PI3K-AKT-mTOR-pathway.

RESULTS

Of 83 included articles, 52 were preclinical and 33 were clinical studies (two studies contained both a preclinical and a clinical part). We classified EGFR pathway inhibitor types and investigated the type of biomarker (biomarker on epigenetic, DNA, mRNA or protein level).

CONCLUSION

Several EGFR-PI3K-AKT-mTOR-pathway inhibitor biomarkers have been researched for HNSCC but few of the investigated biomarkers have been adequately confirmed in clinical trials. A more systematic approach is needed to discover proper biomarkers as stratifying patients is essential to prevent unnecessary costs and side effects.

A chemical genetic screen identifies Aurora kinases as a therapeutic target in EGFR T790M negative, gefitinib-resistant head and neck squamous cell carcinoma (HNSCC)

BACKGROUND

Overexpression of epidermal growth factor receptor (EGFR), and downstream pathway activation appears to be a common oncogenic driver in the majority of head and neck squamous cell cancers (HNSCCs); yet targeting EGFR for the treatment of HNSCC has met with limited success. Apart from the anti-EGFR antibody cetuximab, no small molecule EGFR/tyrosine kinase inhibitors (TKIs) have progressed to routine clinical use. The aim of this study was to determine factors contributing to the lack of response to TKIs and identify alternative therapeutic vulnerabilities.

METHODS

Genomic and transcriptomic sequencing, high-throughput compound screens, overexpression and siRNA knockdown, western blot, in vivo xenograft studies.

FINDINGS

We derived three pairs of isogenic gefitinib (TKI)-sensitive and resistant patient-derived HNSCC cell lines. Genomic sequencing of gefitinib-resistant cell lines identified a lack of activating and resistance-associated EGFR mutations. Instead, transcriptomic sequencing showed upregulated EMT gene signature in the gefitinib-resistant cells with a corresponding increase in their migratory phenotype. Additionally, the resistant cell displayed reduced growth rate. Surprisingly, while gefitinib-resistant cells were independent of EGFR for survival, they nonetheless displayed activation of downstream ERK and AKT signalling. High-throughput screening (HTS) of druggable, small molecule libraries revealed that the gefitinib-resistant cells were particularly sensitive to inhibitors of genes involved in cell cycle and mitosis, such as Aurora kinase inhibitors (AKIs), cyclin-dependent kinase (CDK) inhibitors, and microtubule inhibitors. Notably our results showed that in the EGFR inhibited state, Aurora kinases are essential for cell survival.

INTERPRETATION

Our study demonstrates that in the absence of activating EGFR mutations, HNSCCs may gain resistance to gefitinib through decreased cell proliferation, which makes them exceptionally vulnerable to cell-cycle inhibitors.

FUNDING

Agency for Science, Technology, and Research (A*STAR), National Medical Research Council (NMRC), and the National Institutes of Health (NIH)/National Cancer Institute (NCI).

An update: emerging drugs to treat squamous cell carcinomas of the head and neck

Introduction: Subsequent to the 2006 FDA approval of cetuximab, a variety of molecular targeting agents have been evaluated in head and neck squamous cell carcinoma (HNSCC). The treatment outcomes of recurrent and/or metastatic (R/M) HNSCC, in particular, remain dismal. The 2016 FDA approval of PD-1 immune checkpoint inhibitors has expanded the treatment options for R/M HNSCC and highlights the potential for immune-based therapies. Areas covered: We will review the clinical application of EGFR-targeted agents, alone and in combination with other drugs. Molecular targeting agents directed against the IL6/PI3K/STAT3 signaling pathway will be covered. In addition, evaluation of immune checkpoint inhibitors in HNSCC, along with ongoing combination trials incorporating these agents, will be discussed. The expanded indications of emerging drugs and the potential clinical benefit of new drugs and treatment combinations will be summarized. Expert opinion: In recent years, there has been a major shift toward immunotherapy-based approaches for the treatment of HNSCC, leading to significant improvements in outcomes for a subset of patients. Leveraging the increased understanding of the genetic alterations that characterize individual HNSCC tumors will facilitate precision medicine approaches using targeted agents, immunotherapies, as well as standard chemotherapy and radiation.

EGFR overexpression is not common in patients with head and neck cancer. Cell lines are not representative for the clinical situation in this indication

Background

Based on expression data, Epidermal Growth Factor Receptor (EGFR) emerged as therapeutic target in Head and Neck Cancer but clinical efficacy of EGFR inhibitors was very limited. We reinvestigated the EGFR expression and activation status necessary for response in cell lines and compared that to clinical samples.

Methods

Clinical samples of head and neck squamous cell carcinoma (HNSCC, n=63), mostly from late stage (IV) and poorly or undifferentiated character and cultured cell lines (n=14) were tested by immunohistochemistry (IHC) (n=55) and sandwich immunoassays (n=63) for expression and phosphorylation of EGFR (Tyrosine-1173). Response of 14 different HNSCC cell lines to Erlotinib was tested in proliferation assays.

Results

Most HNSCC cell lines respond to Erlotinib. EGFR is phosphorylated in these cell lines. Resistant cell lines display very low level EGFR expression and phosphorylation. EGFR activity in clinical samples is significantly below that observed in cell lines. In clinical samples, EGFR is not overexpressed on the single cellular level. We show similar levels of EGFR expression in growing keratinocytes and tumor cells.

Conclusions

Cell lines are not representative of the clinical situation in HNSCC. Larger studies should investigate whether patient subgroups with activating EGFR mutations or overexpression can be identified.

Long noncoding RNA ZEB1-AS1 epigenetically regulates the expressions of ZEB1 and downstream molecules in prostate cancer

Background

Emerging studies show that long noncoding RNAs (lncRNAs) play important roles in carcinogenesis and cancer progression. The lncRNA ZEB1 antisense 1 (ZEB1-AS1) derives from the promoter region of ZEB1 and we still know little about its expressions, roles and mechanisms.

Methods

RACE was used to obtain the sequence of ZEB1-AS1. RNA interference was used to decrease ZEB1-AS1 expression. Adenovirus expression vector was used to increase ZEB1-AS1 expression. CHIP and RIP were used to detect the epigenetic mechanisms by which ZEB1-AS1 regulated ZEB1. CCK8 assay, wound healing assay and transwell assay were used to measure proliferation and migration of prostate cancer cells.

Results

In this study, in prostate cancer cells, we found that RNAi-mediated downregulation of ZEB1-AS1 induced significant ZEB1 inhibition while artificial overexpression of ZEB1-AS1 rescued ZEB1 expression, which means that ZEB1-AS1 promotes ZEB1 expression. Also, ZEB1-AS1 indirectly inhibited miR200c, the well-known target of ZEB1, and upregulated miR200c’s target BMI1. Mechanistically, ZEB1-AS1 bound and recruited histone methyltransferase MLL1 to the promoter region of ZEB1, induced H3K4me3 modification therein, and activated ZEB1 transcription. Biologically, ZEB1-AS1 promoted proliferation and migration of prostate cancer cells.

Conclusions

Collectively, ZEB1-AS1 functions as an oncogene in prostate cancer via epigenetically activating ZEB1 and indirectly regulating downstream molecules of ZEB1.

Epithelial-mesenchymal plasticity and circulating tumor cells: Travel companions to metastases

Epithelial-mesenchymal transitions (EMTs) associated with metastatic progression may contribute to the generation of hybrid phenotypes capable of plasticity. This cellular plasticity would provide tumor cells with an increased potential to adapt to the different microenvironments encountered during metastatic spread. Understanding how EMT may functionally equip circulating tumor cells (CTCs) with an enhanced competence to survive in the bloodstream and niche in the colonized organs has thus become a major cancer research axis. We summarize here clinical data with CTC endpoints involving EMT. We then review the work functionally linking EMT programs to CTC biology and deciphering molecular EMT-driven mechanisms supporting their metastatic competence. Developmental Dynamics 247:432-450, 2018. © 2017 Wiley Periodicals, Inc.

Clinicopathological significance of ZEB-1 and E-cadherin proteins in patients with oral cavity squamous cell carcinoma

Background

Zinc-finger E-box binding homeobox 1 (ZEB-1), a member of the ZFH family, plays a key role in epithelial–mesenchymal transition during tumor progression in various cancers. However, little information is available on ZEB-1 expression in oral cavity squamous cell carcinoma (OSCC).

Methods

The expression levels of ZEB-1 and E-cadherin were assessed by immunohistochemistry in a cohort of 120 patients with OSCC treated by curative operation, and then the correlations between ZEB-1 and E-cadherin expression and clinical factors were evaluated, including patient prognosis. Quantitative real-time polymerase chain reaction (qRT-PCR) assays were performed to assess mRNA levels of ZEB-1 and E-cadherin in 20 matched OSCC specimens.

Results

Patients were followed up for a median period of 66 months (range 8−116 months), and 5-year overall survival was 68.3%. Positive ZEB-1 and E-cadherin immunostaining reactivity was detected in 64 (53.3%) and 53 (44.2%) patients, respectively. There was a negative correlation between ZEB-1 expression and E-cadherin expression. In addition, overexpression of ZEB-1 was significantly associated with recurrence, lymph node metastasis, and pathologic grading of patients, loss of E-cadherin was significantly associated with lymph node metastasis and pathologic grading of patients. Univariate analysis showed that increased ZEB-1 expression, loss of E-cadherin expression, lymph node metastasis, recurrence, and pathology grade were prognostic factors. In multivariate analysis, increased ZEB-1 expression and recurrence remained independent prognostic factors. In particular, patients with both ZEB-1 positivity and loss of E-cadherin expression had a poorer prognosis. qRT-PCR showed that ZEB-1 mRNA expression was higher in OSCC compared to the adjacent nontumorous tissues, while E-cadherin mRNA expression was lower in tumor tissues.

Conclusion

This study shows that overexpression of ZEB-1 and loss of E-cadherin expression are significantly correlated with poor survival in OSCC patients, and ZEB-1 expression might serve as an independent prognostic biomarker of OSCC.

Roles and epigenetic regulation of epithelial-mesenchymal transition and its transcription factors in cancer initiation and progression

The epithelial-mesenchymal transition (EMT) is a crucial developmental process by which epithelial cells undergo a mesenchymal phenotypic change. During EMT, epigenetic mechanisms including DNA methylation and histone modifications are involved in the regulation of EMT-related genes. The epigenetic gene silencing of the epithelial marker E-cadherin has been well characterized. In particular, three major transcriptional repressors of E-cadherin, Snail, ZEB, and Twist families, also known as EMT-inducing transcription factors (EMT-TFs), play a crucial role in this process by cooperating with multiple epigenetic modifiers. Furthermore, recent studies have identified the novel epigenetic modifiers that control the expression of EMT-TFs, and these modifiers have emerged as critical regulators of cancer development and as novel therapeutic targets for human cancer. In this review, the diverse functions of EMT-TFs in cancer progression, the cooperative mechanisms of EMT-TFs with epigenetic modifiers, and epigenetic regulatory roles for the expression of EMT-TFs will be discussed.

Targeting pathways mediating resistance to anti-EGFR therapy in squamous cell carcinoma of the head and neck

INTRODUCTION

As epidermal growth factor receptor (EGFR) is overexpressed in approximately 90% of squamous cell carcinomas of the head and neck (SCCHN), several therapeutic agents that target EGFR have been evaluated for the treatment of SCCHN. Although patients with SCCHN derive clinical benefit from anti-EGFR agents, most notably the EGFR monoclonal antibody cetuximab, these patients eventually become resistant to EGFR-based therapies; preclinical studies have shown activation of secondary signaling pathways that lead to resistance to EGFR inhibition and, as such, serve as potential therapeutic targets to overcome resistance to EGFR inhibitors.

AREAS COVERED

This review summarizes the results of recently completed trials of anti-EGFR agents in SCCHN, highlights the various mechanisms that drive resistance to EGFR inhibitors in SCCHN, and focuses on several novel targeted agents that could potentially help overcome resistance to EGFR-based therapies in SCCHN. Expert commentary: Due to the development of resistance to EGFR-targeted therapies, novel treatment approaches to overcome resistance are a key unmet need for SCCHN.

Orchestrating the Tumor Microenvironment to Improve Survival for Patients With Pancreatic Cancer: Normalization, Not Destruction

Pancreatic cancer is the fourth leading cause of cancer death in the United States. The microenvironment of pancreatic cancer could be one of the "perfect storms" that support the growth of a cancer. Indeed, pancreatic cancer may be the poster child of a problem with the microenvironment. In this article, we review the rationale and attempts to date on modifying or targeting structural proteins in the microenvironment including hyaluronan (HA) (in primary and metastases), collagen, and SPARC (secreted protein, acidic, and rich in cysteine). Indeed, working in this area has produced a regimen that improves survival for patients with advanced pancreatic cancer (nab-paclitaxel + gemcitabine). In addition, in initial clinical trials, PEGylated hyaluronidase appears promising. We also review a new approach that is different than targeting/destroying the microenvironment and that is orchestrating, reengineering, reprogramming, or normalizing the microenvironment (including normalizing structural proteins, normalizing an immunologically tumor-friendly environment to a less friendly environment, reversing epithelial-to-mesenchymal transition, and so on). We believe this will be most effectively done by agents that have global effects on transcription. There is initial evidence that this can be done by agents such as vitamin D derivatives and other new agents. There is no doubt these opportunities can now be tried in the clinic with hopefully beneficial effects.

ZEB1: at the crossroads of epithelial-mesenchymal transition, metastasis and therapy resistance

Zinc finger E-box binding homeobox 1 (ZEB1) is a transcription factor that promotes tumor invasion and metastasis by inducing epithelial-mesenchymal transition (EMT) in carcinoma cells. EMT not only plays an important role in embryonic development and malignant progression, but is also implicated in cancer therapy resistance. It has been hypothesized that carcinoma cells that have undergone EMT acquire cancer stem cell properties including self-renewal, chemoresistance and radioresistance. However, our recent data indicate that ZEB1 regulates radioresistance in breast cancer cells through an EMT-independent mechanism. In this Perspective, we review different mechanisms by which ZEB1 regulates tumor progression and treatment resistance. Based on studies by us and others, we propose that it is specific EMT inducers like ZEB1, but not the epithelial or mesenchymal state itself, that dictate cancer stem cell properties.

Establishment and characterization of cetuximab resistant head and neck squamous cell carcinoma cell lines: focus on the contribution of the AP-1 transcription factor

BACKGROUND

After an initial response to EGFR targeted therapy, secondary resistance almost invariably ensues, thereby limiting the clinical benefit of the drug. Hence, it has been recognized that the successful implementation of targeted therapy in the treatment of HNSCC cancer is very much dependent on predictive biomarkers for patient selection.

METHODS

We generated an in vitro model of acquired cetuximab resistance by chronically exposing three HNSCC cell lines to increasing cetuximab doses. Gene expression profiles of sensitive parental cells and resistant daughter cells were compared using microarray analysis. Growth inhibitory experiments were performed with an HB-EGF antibody and the MMP inhibitor, both in combination with cetuximab. Characteristics of EMT were analyzed using migration and invasion assays, immunofluorescent vimentin staining and qRT-PCR for several genes involved in this process. The function of the transcription factor AP-1 was investigated using qRT-PCR for several genes upregulated or downregulated in cetuximab resistant cells. Furthermore, anchorage-independent growth was investigated using the soft agar assay.

RESULTS

Gene expression profiling shows that cetuximab resistant cells upregulate several genes, including interleukin 8, the EGFR ligand HB-EGF and the metalloproteinase ADAM19. Cytotoxicity experiments with neutralizing HB-EGF antibody could not induce any growth inhibition, whereas an MMP inhibitor inhibited cell growth in cetuximab resistant cells. However, no synergetic effects combined with cetuximab could be observed. Cetuximab resistant cells showed traits of EMT, as witnessed by increased migratory potential, increased invasive potential, increased vimentine expression and increased expression of several genes involved in EMT. Furthermore, expression of upregulated genes could be repressed by the treatment with apigenin. The cetuximab resistant LICR-HN2 R10.3 cells tend to behave differently in cell culture, forming spheres. Therefore, soft agar assay was performed and showed more and larger colonies when challenged with cetuximab compared to PBS challenged cells.

CONCLUSIONS

In summary, our results indicate that increased expression of the ligand HB-EGF could contribute to resistance towards cetuximab in our cetuximab resistant HNSCC cells. Furthermore, several genes upregulated or downregulated in cetuximab resistant cells are under control of the AP-1 transcription factor. However, more studies are warranted to further unravel the role of AP-1 in cetuximab resistance.

The emerging molecular machinery and therapeutic targets of metastasis

Metastasis is a 100-year-old research topic. Technological advances during the past few decades have led to significant progress in our understanding of metastatic disease. However, metastasis remains the leading cause of cancer-related mortalities. The lack of appropriate clinical trials for metastasis preventive drugs and incomplete understanding of the molecular machinery are major obstacles in metastasis prevention and treatment. Numerous processes, factors, and signaling pathways are involved in regulating metastasis. Here we discuss recent progress in metastasis research, including epithelial-mesenchymal plasticity, cancer stem cells, emerging molecular determinants and therapeutic targets, and the link between metastasis and therapy resistance.

Clinicopathological analysis of pleomorphic carcinoma of the lung: diffuse ZEB1 expression predicts poor survival

OBJECTIVES

Pleomorphic carcinoma (PC) of the lung is a rare epithelial tumor. The clinicopathological characteristics and prognostic factors of PC are controversial. The information on the ZEB1 gene, which crucially impacts survival of patients with other malignant tumors, is limited for PC.

MATERIALS AND METHODS

Clinicopathological characteristics of 62 patients with PC were investigated in this study. Associations between immunohistochemical expression of ZEB1 and clinical factors, including patient prognosis, were examined. The patient population consisted of 51 (82.2%) men and 11 (17.8%) women, with a mean age of 65.5 years (range, 31-81 years).

RESULTS

The overall survival rate of the 42 patients, for whom follow-up was available, was 68.3% at 5 years. Using TNM criteria, 7 (11.3%), 11 (17.7%), 3 (4.8%), 21 (33.8%), 15 (24.2%), 2 (3.2%), and 3 (4.8%) patients were classified under pathological stage IA, IB, IIA, IIB, IIIA, IIIB and IV carcinomas, respectively. Fifteen (24.1%) patients had tumors consisting entirely of spindle and giant cells (PC component). The other 47 (75.8%) cancers contained additional carcinoma components (i.e., adenocarcinoma (34/62, 54.8%), squamous cell carcinoma (7/62, 11.3%), adenosquamous carcinoma (4/62, 6.5%) and large cell carcinoma (2/62, 3.2%)). Four of 7 (57.1%) stage IA (<20mm) tumors consisted only of spindle and giant cells. ZEB1 expression was observed only in the PC component. Diffuse expression of ZEB1, was defined as positive nuclear staining in ≥75% of cancer cells, and was found in the PC component in 12 patients. Multivariate analysis revealed that lymph node metastasis, pleural invasion, and diffuse ZEB1 expression in the PC component predicted poorer disease-specific survival (p=0.007, 0.022, and 0.016, respectively).

CONCLUSION

This is the first report to indicate that ZEB1 may be used as an immunohistochemical prognosticator of PC, which may be useful for histological assessment of PC in biopsy and surgical specimens.

ErbB targeting inhibitors repress cell migration of esophageal squamous cell carcinoma and adenocarcinoma cells by distinct signaling pathways

ErbB family receptor tyrosine kinases (ErbBs) play a role in cell adhesion and migration and are frequently overexpressed in esophageal squamous cell carcinomas (ESCCs) or esophageal adenocarcinomas (EACs). Targeting ErbBs by tyrosine kinase inhibitors (TKIs) may therefore limit esophageal cancer cell migration. Here, we studied the impact of TKIs on ErbB dimerization, cell signaling pathways, and cell migration in three esophageal cell lines: OE21 (ESCC), OE33 (EAC), and Het-1A (non-neoplastic esophageal epithelium). In OE21 cells, the TKIs erlotinib, gefitinib, and lapatinib slightly affected epidermal growth factor receptor EGFR/EGFR, but not EGFR/HER2 dimerization as detected by in situ proximity ligation assay (in situ PLA). Still, TKIs inhibited ERK1/2, Akt, STAT3, and RhoA activity in OE21 cells, as assessed by Western blot, antibody arrays, and Rho GTPase effector pull-down assays. This was accompanied by reduced OE21 cell migration, induction of focal adhesions, and actin cytoskeleton reorganization, as shown by Oris™ migration assay and focal adhesion kinase (FAK)/phalloidin staining. In contrast, in OE33 cells, only lapatinib decreased STAT5, Src family kinase (SFK), and FAK activity as well as β-catenin expression. This impeded cell migration and induced morphological changes in OE33 cells. No alterations were seen for the non-neoplastic Het-1A cells. Thus, we identified the ErbB signaling network as regulator of esophageal cancer cell's actin cytoskeleton, focal adhesions, and cell migration. ErbB targeted TKIs therefore also limit ESCC and EAC cell motility and migration.

KEY MESSAGE

Clinical tyrosine kinase inhibitors (TKIs) reduce esophageal cancer cell migration. Loss of cell migration is linked to reduced Akt, ERK1/2, STAT (3 or 5), FAK, SFKs, and RhoA activity. Clinical TKIs act via distinct signaling in the two main histotypes of esophageal cancer.

Downregulation of GRHL2 inhibits the proliferation of colorectal cancer cells by targeting ZEB1

Previous reports have associated GRHL2 with tumor progression. However, the biological role of GRHL2 in human colorectal cancer (CRC) has not been explored. We examined the expression of GRHL2 in 75 CRC samples, as well as the paired non-tumor tissues, by immunohistochemistry, qRT-PCR, and western blot analysis. The association between GRHL2 expression and various clinicopathological parameters including Ki-67, a marker of proliferative activity, was also evaluated. We performed lentivirus-mediated shRNA transfection to knock down GRHL2 gene expression in HT29 and HCT116 CRC cells. Cell proliferation was examined by the CCK-8 (Cell Counting Kit-8) assay, colony formation, and cell cycle assay in vitro. Tumorigenesis in vivo was assessed using a mouse xenograft model. Moreover, we transiently silenced ZEB1 expression in GRHL2-knockdown CRC cells using specific shRNA, and then examined the effects on GRHL2 and E-cadherin expression, as well as cell proliferation. Herein, we demonstrated that enhanced GRHL2 expression was detected in CRC, and correlated with higher levels of Ki-67 staining, larger tumor size, and advanced clinical stage. Knocking down GRHL2 in HT29 and HCT116 CRC cells significantly inhibited cell proliferation by decreasing the number of cells in S phase and increasing that in the G 0/G 1 phaseof the cell cycle. This resulted in inhibition of tumorigenesis in vivo, as well as increased expression of ZEB1. Furthermore, transient ZEB1 knockdown dramatically enhanced cell proliferation and increased GRHL2 and E-cadherin expression. Collectively, our study has identified ZEB1 as a target of GRHL2 and suggested a reciprocal GRHL2-ZEB1 repressive relationship, providing a novel mechanism through which proliferation may be modulated in CRC cells.

Proteomic analysis identifies differentially expressed proteins after red propolis treatment in Hep-2 cells

Here we investigated alterations in the protein profile of Hep-2 treated with red propolis using two-dimensional electrophoresis associated to mass spectrometry and apoptotic rates of cells treated with and without red propolis extracts through TUNEL and Annexin-V assays. A total of 325 spots were manually excised from the two-dimensional gel electrophoresis and 177 proteins were identified using LC-MS-MS. Among all proteins identified that presented differential expression, most were down-regulated in presence of red propolis extract at a concentration of 120 μg/mL (IC50): GRP78, PRDX2, LDHB, VIM and TUBA1A. Only two up-regulated proteins were identified in this study in the non-cytotoxic (6 μg/mL) red propolis treated group: RPLP0 and RAD23B. TUNEL staining assay showed a markedly increase in the mid- to late-stage apoptosis of Hep-2 cells induced by red propolis at concentrations of 60 and 120 μg/mL when compared with non-treated cells. The increase of late apoptosis was confirmed by in situ Annexin-V analysis in which red propolis extract induced late apoptosis in a dose-dependent manner. The differences in tumor cell protein profiles warrant further investigations including isolation of major bioactive compounds of red propolis in different cell lines using proteomics and molecular tests to validate the protein expression here observed.

Axl mediates acquired resistance of head and neck cancer cells to the epidermal growth factor receptor inhibitor erlotinib

Elevated expression and activity of the epidermal growth factor receptor (EGFR) is associated with development and progression of head and neck cancer (HNC) and a poor prognosis. Clinical trials with EGFR tyrosine kinase inhibitors (e.g., erlotinib) have been disappointing in HNC. To investigate the mechanisms mediating resistance to these agents, we developed an HNC cell line (HN5-ER) with acquired erlotinib resistance. In contrast to parental HN5 HNC cells, HN5-ER cells exhibited an epithelial-mesenchymal (EMT) phenotype with increased migratory potential, reduced E-cadherin and epithelial-associated microRNAs (miRNA), and elevated vimentin expression. Phosphorylated receptor tyrosine kinase profiling identified Axl activation in HN5-ER cells. Growth and migration of HN5-ER cells were blocked with a specific Axl inhibitor, R428, and R428 resensitized HN5-ER cells to erlotinib. Microarray analysis of HN5-ER cells confirmed the EMT phenotype associated with acquired erlotinib resistance, and identified activation of gene expression associated with cell migration and inflammation pathways. Moreover, increased expression and secretion of interleukin (IL)-6 and IL-8 in HN5-ER cells suggested a role for inflammatory cytokine signaling in EMT and erlotinib resistance. Expression of the tumor suppressor miR-34a was reduced in HN5-ER cells and increasing its expression abrogated Axl expression and reversed erlotinib resistance. Finally, analysis of 302 HNC patients revealed that high tumor Axl mRNA expression was associated with poorer survival (HR = 1.66, P = 0.007). In summary, our results identify Axl as a key mediator of acquired erlotinib resistance in HNC and suggest that therapeutic inhibition of Axl by small molecule drugs or specific miRNAs might overcome anti-EGFR therapy resistance.

EGFR inhibition promotes an aggressive invasion pattern mediated by mesenchymal-like tumor cells within squamous cell carcinomas

Squamous cell carcinomas (SCC) with an infiltrative invasion pattern carry a higher risk of treatment failure. Such infiltrative invasion may be mediated by a mesenchymal-like subpopulation of malignant cells that we have previously shown to arise from epithelial-mesenchymal transition (EMT) and resist epidermal growth factor receptor (EGFR) targeting. Here, we show that SCCs with infiltrative, high-risk invasion patterns contain abundant mesenchymal-like cells, which are rare in tumors with low-risk patterns. This cellular heterogeneity was modeled accurately in three-dimensional culture using collagen-embedded SCC spheroids, which revealed distinct invasive fronts created by collective migration of E-cadherin-positive cells versus infiltrative migration of individual mesenchymal-like cells. Because EGFR expression by mesenchymal-like cells was diminished in the spheroid model and in human SCCs, we hypothesized that SCCs shift toward infiltrative invasion mediated by this subpopulation during anti-EGFR therapy. Anti-EGFR treatment of spheroids using erlotinib or cetuximab enhanced infiltrative invasion by targeting collective migration by E-cadherin-positive cells while sparing mesenchymal-like cells; by contrast, spheroid invasion in absence of mesenchymal-like cells was abrogated by erlotinib. Similarly, cetuximab treatment of xenografts containing mesenchymal-like cells created an infiltrative invasive front composed of this subpopulation, whereas no such shift was observed upon treating xenografts lacking these cells. These results implicate mesenchymal-like SCC cells as key mediators of the infiltrative invasion seen in tumors with locally aggressive behavior. They further show that EGFR inhibition can promote an infiltrative invasion front composed of mesenchymal-like cells preferentially in tumors where they are abundant before therapy.

Anti-epidermal growth factor receptor therapy in head and neck squamous cell carcinoma: focus on potential molecular mechanisms of drug resistance

Targeted therapy against the epidermal growth factor receptor (EGFR) is one of the most promising molecular therapeutics for head and neck squamous cell carcinoma (HNSCC). EGFR is overexpressed in a wide range of malignancies, including HNSCC, and initiates important signal transduction pathways in HNSCC carcinogenesis. However, primary and acquired resistance are serious problems and are responsible for low single-agent response rate and tumor recurrence. Therefore, an improved understanding of the molecular mechanisms of resistance to EGFR inhibitors may provide valuable indications to identify biomarkers that can be used clinically to predict response to EGFR blockade and to establish new treatment options to overcome resistance. To date, no predictive biomarker for HNSCC is available in the clinic. Therapeutic resistance to anti-EGFR therapy may arise from mechanisms that can compensate for reduced EGFR signaling and/or mechanisms that can modulate EGFR-dependent signaling. In this review, we will summarize some of these molecular mechanisms and describe strategies to overcome that resistance.

Gain-of-function mutant p53 downregulates miR-223 contributing to chemoresistance of cultured tumor cells

Mutant p53 proteins are expressed at high frequency in human tumors and are associated with poor clinical prognosis and resistance to chemotherapeutic treatments. Here we show that mutant p53 proteins downregulate micro-RNA (miR)-223 expression in breast and colon cancer cell lines. Mutant p53 binds the miR-223 promoter and reduces its transcriptional activity. This requires the transcriptional repressor ZEB-1. We found that miR-223 exogenous expression sensitizes breast and colon cancer cell lines expressing mutant p53 to treatment with DNA-damaging drugs. Among the putative miR-223 targets, we focused on stathmin-1 (STMN-1), an oncoprotein known to confer resistance to chemotherapeutic drugs associated with poor clinical prognosis. Mutant p53 silencing or miR-223 exogenous expression lowers the levels of STMN-1 and knockdown of STMN-1 by small interfering RNA increases cell death of mutant p53-expressing cell lines. On the basis of these findings, we propose that one of the pathways affected by mutant p53 to increase cellular resistance to chemotherapeutic agents involves miR-223 downregulation and the consequent upregulation of STMN-1.

Potential advantages of CUDC-101, a multitargeted HDAC, EGFR, and HER2 inhibitor, in treating drug resistance and preventing cancer cell migration and invasion

CUDC-101 is a novel, small-molecule, anticancer agent targeting histone deacetylase (HDAC), EGF receptor (EGFR), and HER2. It is currently in phase I clinical development in patients with solid tumors. Previously, we reported that CUDC-101 has potent antiproliferative and proapoptotic activity in cultured tumor cells and in vivo xenograft models. We now show that cancer cells that have acquired resistance to single-target EGFR inhibitors through upregulation of AXL or loss of E-cadherin remain sensitive to CUDC-101, which inhibits MET- and AXL-mediated signaling, restores E-cadherin expression, and reduces cell migration. CUDC-101 also efficiently inhibited the proliferation of MET-overexpressing non-small cell lung cancer and gastric cancer cell lines and inhibited the migration and invasion of invasive tumor cells. Taken together, these results suggest that coupling HDAC and HER2 inhibitory activities to an EGFR inhibitor may potentially be effective in overcoming drug resistance and preventing cancer cell migration.

Sheep, wolf, or werewolf: cancer stem cells and the epithelial-to-mesenchymal transition

Multiple cancers contain subpopulations that exhibit characteristics of cancer stem cells (CSCs), the ability to self-renew and seed heterogeneous tumors. Recent evidence suggests two potentially overlapping models for these phenotypes: one where stem cells arise from multipotent progenitor cells, and another where they are created via an epithelial to mesenchymal transition. Unraveling this issue is critical, as it underlies phenomena such as metastasis and therapeutic resistance. Therefore, there is intense interest in understanding these two types of CSSs, how they differ from differentiated cancer cells, the mechanisms that drive their phenotypes, and how that knowledge can be incorporated into therapeutics.

Tumor-stromal interactions in pancreatic cancer

The tumor associated stroma has been described in recent years as being complicit in tumor growth in pancreatic cancer. The stroma hosts a variety of components of both cellular and molecular makeup. In normal tissues, the stroma provides nutrients and regulatory signals for proper cellular polarity and function. However, following oncogenic transformation, the stromal compartment is conscripted to provide stimulatory signals and protection to tumor cells. It is these tumor-stromal interactions that are currently of great therapeutic interest. Several key reports have suggested that therapeutic targeting of the tumor-stromal interactions in pancreatic cancer has the potential to offer survival benefit. In this review, we will discuss the tumor-stromal interactions that contribute to tumor growth and progression, and ways in which we might counter these interactions.

δEF1 down-regulates ER-α expression and confers tamoxifen resistance in breast cancer

Resistance to tamoxifen therapy represents a major barrier to the successful treatment of breast cancer, where a loss of or reduced ER-α level is considered a primary mechanism. Understanding how ER-α expression is regulated would provide insights into new intervention points to overcome tamoxifen resistance. In this study, we report that the expression of δEF1 is up-regulated by 17β-estradiol (E2) in MCF-7 cells in an ER-α-dependent manner, through either PI3K or NF-κB pathway. Ectopic expression of δEF1 in turn repressed ER-α transcription by binding to the E(2)-box on the ER-α promoter. At the tissue level of breast cancer, there is a strong and inverse correlation between the expression levels of δEF1 and ER-α. In MCF-7 cells, an elevated expression of δEF1 made the cells less sensitive to tamoxifen treatment, whereas overexpression of ER-α compromised the effects of δEF1 and restored the sensitivity. Also, depletion of δEF1 by RNA interference in MDA-MB-231 cells restored the expression of ER-α and tamoxifen sensitivity. In conclusion, we have identified an important role of δEF1 in the development of tamoxifen resistance in breast cancer. Inhibiting δEF1 to restore ER-α expression might represent a potential therapeutic strategy for overcoming endocrine resistance in breast cancer.

EMT-activating transcription factors in cancer: beyond EMT and tumor invasiveness

Cancer is a complex multistep process involving genetic and epigenetic changes that eventually result in the activation of oncogenic pathways and/or inactivation of tumor suppressor signals. During cancer progression, cancer cells acquire a number of hallmarks that promote tumor growth and invasion. A crucial mechanism by which carcinoma cells enhance their invasive capacity is the dissolution of intercellular adhesions and the acquisition of a more motile mesenchymal phenotype as part of an epithelial-to-mesenchymal transition (EMT). Although many transcription factors can trigger it, the full molecular reprogramming occurring during an EMT is mainly orchestrated by three major groups of transcription factors: the ZEB, Snail and Twist families. Upregulated expression of these EMT-activating transcription factors (EMT-ATFs) promotes tumor invasiveness in cell lines and xenograft mice models and has been associated with poor clinical prognosis in human cancers. Evidence accumulated in the last few years indicates that EMT-ATFs also regulate an expanding set of cancer cell capabilities beyond tumor invasion. Thus, EMT-ATFs have been shown to cooperate in oncogenic transformation, regulate cancer cell stemness, override safeguard programs against cancer like apoptosis and senescence, determine resistance to chemotherapy and promote tumor angiogenesis. This article reviews the expanding portfolio of functions played by EMT-ATFs in cancer progression.

Preclinical modeling of EGFR inhibitor resistance in head and neck cancer

The epidermal growth factor receptor (EGFR) is widely expressed in head and neck squamous cell carcinomas (HNSCC) and can activate many growth and survival pathways within tumor cells. Despite ubiquitous EGFR expression, therapies targeting the receptor are only modestly effective in the treatment of HNSCC. A consistent mechanism of resistance to EGFR targeting agents has not yet been identified in HNSCC likely due, in part, to the paucity of preclinical models. We assessed the in vitro and in vivo responses of a panel of 10 genotypically validated HNSCC cell lines to the EGFR inhibitors erlotinib and cetuximab to determine their validity as models of resistance to these agents. We defined a narrow range of response to erlotinib in HNSCC cells in vitro and found a positive correlation between EGFR protein expression and erlotinib response. We observed cross-sensitivity in one HNSCC cell line, 686LN, between erlotinib and cetuximab in vivo. We attempted to generate models of cetuximab resistance in HNSCC cell line-derived xenografts and heterotopic tumorgrafts generated directly from primary patient tumors. While all 10 HNSCC cell line xenografts tested were sensitive to cetuximab in vivo, heterotopic patient tumorgrafts varied in response to cetuximab indicating that these models may be more representative of clinical responses. These studies demonstrate the limitations of using HNSCC cell lines to reflect the heterogeneous clinical responses to erlotinib and cetuximab, and suggest that different approaches including heterotopic tumorgrafts may prove more valuable to elucidate mechanisms of clinical resistance to EGFR inhibitors in HNSCC.

A comparison of epithelial-to-mesenchymal transition and re-epithelialization

Wound healing and cancer metastasis share a common starting point, namely, a change in the phenotype of some cells from stationary to motile. The term, epithelial-to-mesenchymal transition (EMT) describes the changes in molecular biology and cellular physiology that allow a cell to transition from a sedentary cell to a motile cell, a process that is relevant not only for cancer and regeneration, but also for normal development of multicellular organisms. The present review compares the similarities and differences in cellular response at the molecular level as tumor cells enter EMT or as keratinocytes begin the process of re-epithelialization of a wound. Looking toward clinical interventions that might modulate these processes, the mechanisms and outcomes of current and potential therapies are reviewed for both anti-cancer and pro-wound healing treatments related to the pathways that are central to EMT. Taken together, the comparison of re-epithelialization and tumor EMT serves as a starting point for the development of therapies that can selectively modulate different forms of EMT.

Caveolin-1 overexpression is associated with simultaneous abnormal expression of the E-cadherin/α-β catenins complex and multiple ErbB receptors and with lymph nodes metastasis in head and neck squamous cell carcinomas

The presence of lymph node metastases is one of the most important prognostic indicators in head and neck squamous cell carcinomas (HNSCCs). An alteration of the E-cadherin-catenins complex and EGFR is essential for the invasiveness of cancer cells. Caveolin-1, the major structural protein of the caveolae, represents a scaffolding molecule for several signaling proteins including EGFR. Although caveolin-1 has been shown to play a role in inducing the invasive phenotype of cancer cells, its role appears to be cell-type specific and for some tumors it has not been defined yet. In this study we used 57 HNSCC specimens to investigate whether the abnormal expression of caveolin-1 was associated with the derangement of the E-cadherin-catenins complex and with the overexpression of ErbB receptors. We demonstrate that in HNSCCs caveolin-1 overexpression is associated with the simultaneous abnormal expression of at least one member of the E-cadherin/α-β catenins complex and multiple ErbB receptors as well as with lymph node metastases. We also demonstrate that chronic stimulation of a human hypopharyngeal carcinoma cell line (FaDu) with EGF induced the internalization of β-catenin and caveolin-1 and their co-localization with EGFR. Moreover, EGF treatment induced an increased physical interaction between EGFR/β-catenin/caveolin-1 and between E-cadherin/β-catenin/caveolin-1. These molecular events were associated with an increased directional motility of FaDu cells in vitro. These findings may provide new insight into the biology of HNSCC progression and help to identify subgroups of primary HNSCCs with a more aggressive behavior.

Apricoxib upregulates 15-PGDH and PGT in tobacco-related epithelial malignancies

Background:

Despite focused research in conventional therapies and considerable advances in the understanding of the molecular carcinogenesis of head and neck squamous cell carcinoma (HNSCC), the 5-year survival rate for patients with advanced disease remains ∼15–20%. The major causes of HNSCC-related deaths are cervical node and distant metastasis. E-cadherin has a key role in epithelial intercellular adhesion and its downregulation is a hallmark of epithelial–mesenchymal transition (EMT), which is associated with invasion, metastasis, and poor prognosis. Epithelial–mesenchymal transition is the major mechanism responsible for mediating invasiveness and metastasis of epithelial cancers. Recently, we reported the role of E-cadherin transcriptional repressors in the inflammation-induced promotion of EMT in HNSCC, which is mediated by COX-2. These findings suggest that therapies targeting the cyclooxygenase pathway may diminish the propensity for tumour metastasis in HNSCC by blocking the PGE2-mediated induction of E-cadherin transcriptional repressors.

Methods:

Herein, we evaluate the efficacy of the COX-2 inhibitor, apricoxib, in HNSCC cell lines. Apricoxib is effective in preventing tumour cell growth in three-dimensional, and anchorage-independent growth assays, as well as decreasing the capacity for tumour cell migration.

Results:

Herein, we evaluate the efficacy of the COX-2 inhibitor, apricoxib, in HNSCC cell lines. Apricoxib is effective in preventing tumour cell growth in three-dimensional, and anchorage-independent growth assays, as well as decreasing the capacity for tumour cell migration. Treatment of HNSCC cells with apricoxib also causes greater upregulation of E-cadherin and Muc1 expression and downregulation of vimentin, as compared with celecoxib treatment. This has significant implications for targeted chemoprevention and anti-cancer therapy because E-cadherin expression has been implicated as a marker of sensitivity to epidermal growth factor receptor tyrosine kinase inhibitor and other therapies. We show for the first time the molecular mechanisms underlying the efficacy of apricoxib in HNSCC cells.

Conclusion:

In addition to reversing EMT via inhibition of COX-2, apricoxib upregulates 15-prostaglandin dehydrogenase and the prostaglandin transporter, thereby reducing the levels of active PGE2 by both suppressing its synthesis and increasing its catabolism. These findings have significant implications for metastasis and tumour progression in HNSCC.

To differentiate or not--routes towards metastasis

Why are many metastases differentiated? Invading and disseminating carcinoma cells can undergo an epithelial-mesenchymal transition (EMT), which is associated with a gain of stem cell-like behaviour. Therefore, EMT has been linked to the cancer stem cell concept. However, it is a matter of debate how subsequent mesenchymal-epithelial transition (MET) fits into the metastatic process and whether a MET is essential. In this Opinion article, I propose two principle types of metastatic progression: phenotypic plasticity involving transient EMT-MET processes and intrinsic genetic alterations keeping cells in an EMT and stemness state. This simplified classification integrates clinically relevant aspects of dormancy, metastatic tropism and therapy resistance, and implies perspectives on treatment strategies against metastasis.

Epidermal to Mesenchymal Transition and Failure of EGFR-Targeted Therapy in Glioblastoma

Glioblastoma multiforme (GBM), the most common primary brain tumor in adults, is almost never curable with the current standard treatment consisting of surgical resection, irradiation and temozolomide. The prognosis remains poor despite undisputable advances in the understanding of this tumor’s molecular biology and pathophysiology, which unfortunately has so far failed to translate into a meaningful clinical benefit. Dysregulation and a resulting prominent pathophysiological role of the epidermal growth factor receptor (EGFR) have been identified in several different malignant tumor entities, GBM among them. The EGFR is overexpressed in about 40% of GBM cases, and half of these coexpress a mutant, constitutively activated subtype, EGFRvIII. Unfortunately, recent trials studying with therapeutic approaches targeted against the EGFR and EGFRvIII have failed to meet expectations, with only a minority of patients responding despite evidence of good in vitro and rodent model activity. Having potentially high relevance within this context, epithelial to mesenchymal transition (EMT) is a phenomenon associated with early stages of carcinogenesis, cancer invasion and recurrence. During EMT, epithelial cells lose many of their epithelial characteristics, prominently E-cadherin expression, and acquire properties that are typical for mesenchymal cells such as the expression of vimentin. Epithelial to mesenchymal transition has been specifically demonstrated in GBM. In this review, we summarize the evidence that EMT may precipitate GBM resistance to EGFR-targeted therapy, and may thus be among the principal factors contributing to the clinical failure of targeted therapy against EGFR and EGFRvIII.

Identification of tumour initiating cells in feline head and neck squamous cell carcinoma and evidence for gefitinib induced epithelial to mesenchymal transition

Feline oral squamous cell carcinoma is considered a highly invasive cancer that carries a high level of morbidity. Despite aggressive surgery, patients often succumb to disease, the tumour having inherent insensitivity to radiation and chemotherapy. In this study we sought to identify cells within the feline SCC1 line that have stem cell properties, including inherent resistance mechanisms. When feline cells were subjected to harsh growth conditions, they formed sphere colonies consistent with a stem cell phenotype. Utilising CD133, we were able to identify a small fraction of cells within the population that had enhanced sphere-forming ability, reduced sensitivity to radiation and conventional chemotherapy and demonstrated resistance to the EGFR-targeting drug, gefitinib. In addition, long-term culture of feline SSC1 cells in gefitinib caused a change in cell morphology and gene expression reminiscent of an epithelial to mesenchymal transition. Taken together, these results suggest that feline SCC may be driven by small subset of cancer stem cells.

Proteomic analysis identifies differentially expressed proteins after HDAC vorinostat and EGFR inhibitor gefitinib treatments in Hep-2 cancer cells

Several solid tumors are characterized by poor prognosis and few effective treatment options, other than palliative chemotherapy in the recurrent/metastatic setting. Epidermal growth factor receptor (EGFR) has been considered an important anticancer target because it is involved in the development and progression of several solid tumors; however, only a subset of patients show a clinically meaningful response to EGFR inhibition, particularly to EGFR tyrosine kinase inhibitors such as gefitinib. We have recently demonstrated synergistic antitumor effect of the histone deacetylase inhibitor vorinostat combined with gefitinib. To further characterize the interaction between these two agents, cellular extracts from Hep-2 cancer cells that were untreated or treated for 24 h with either vorinostat or gefitinib alone or with a vorinostat/gefitinib combination were analyzed using 2-D DIGE. Software analysis using DeCyder was performed, and numerous differentially expressed protein spots were visualized between the four examined settings. Using MALDI-TOF MS and ESI-Ion trap MS/MS, several differentially expressed proteins were identified; some of these were validated by Western blotting. Finally, a pathway analysis of experimental data performed using MetaCore highlighted a relevant relationship between the identified proteins and additional potential effectors. In conclusion, we performed a comprehensive analysis of proteins regulated by vorinostat and gefitinib, alone and in combination, providing a useful insight into their mechanisms of action as well as their synergistic interaction.

A microRNA gene expression signature predicts response to erlotinib in epithelial cancer cell lines and targets EMT

Background:

Treatment with epidermal growth factor receptor (EGFR) inhibitors can result in clinical response in non-small-cell lung cancer (NSCLC) and pancreatic ductal adenocarcinoma (PDAC) for some unselected patients. EGFR and KRAS mutation status, amplification of EGFR, or gene expression predictors of response can forecast sensitivity to EGFR inhibition.

Methods:

Using an NSCLC cell line model system, we identified and characterised microRNA (miRNA) gene expression that predicts response to EGFR inhibition.

Results:

Expression of 13 miRNA genes predicts response to EGFR inhibition in cancer cell lines and tumours, and discriminates primary from metastatic tumours. Signature genes target proteins that are enriched for epithelial-to-mesenchymal transition (EMT) genes. Epithelial-to-mesenchymal transition predicts EGFR inhibitor resistance and metastatic behaviour. The EMT transcription factor, ZEB1, shows altered expression in erlotinib-sensitive NSCLC and PDAC, where many signature miRNA genes are upregulated. Ectopic expression of mir-200c alters expression of EMT proteins, sensitivity to erlotinib, and migration in lung cells. Treatment with TGFβ1 changes expression of signature miRNA and EMT proteins and modulates migration in lung cells.

Conclusion:

From these data, we hypothesise that the tumour microenvironment elicits TGFβ1 and stimulates a miRNA gene expression program that induces resistance to anti-EGFR therapy and drives lung tumour cells to EMT, invasion, and metastasis.

Expanding roles of ZEB factors in tumorigenesis and tumor progression

The ZEB family of transcription factors regulates key factors during embryonic development and cell differentiation but their role in cancer biology has only more recently begun to be recognized. Early evidence showed that ZEB proteins induce an epithelial-to-mesenchymal transition linking their expression with increased aggressiveness and metastasis in mice models and a wide range of primary human carcinomas. Reports over the last few years have found that ZEB proteins also play critical roles in the maintenance of cancer cell stemness, control of replicative senescence, tumor angiogenesis, overcoming of oncogenic addiction and resistance to chemotherapy. These expanding roles in tumorigenesis and tumor progression set ZEB proteins as potential diagnostic, prognostic and therapeutic targets.

HDAC inhibitor vorinostat enhances the antitumor effect of gefitinib in squamous cell carcinoma of head and neck by modulating ErbB receptor expression and reverting EMT

Potentiation of epidermal growth factor receptor (EGFR) inhibitors is required in squamous cell carcinoma of head and neck (SCCHN) to improve their therapeutic index. We demonstrated that the histone deacetylase inhibitor vorinostat in combination with the EGFR tyrosine kinase inhibitor gefitinib induced synergistic inhibition of proliferation, migration, and invasion as well as induction of apoptosis in SCCHN cells, including cells resistant to gefitinib. We provided evidence suggesting that differential modulation of ErbB receptors together with reversion of epithelial-to-mesenchymal transition (EMT) by vorinostat represent mechanistic bases for the observed synergism. We demonstrated in epithelial CAL27 cells expressing EGFR, ErbB2, and ErbB3 that vorinostat downregulated the expression and signaling of all three receptors. In gefitinib-resistant KB and Hep-2 cells, both of which had undergone EMT and expressed very low levels of ErbB3, vorinostat reverted the mesenchymal phenotype by inducing both E-cadherin and ErbB3 and downregulating vimentin as well as EGFR and ErbB2. Both transcriptional and post-translational mechanisms were involved in the modulation of ErbB receptors by vorinostat. Attenuation of all ErbB transcripts in CAL27 cells as well as induction of ErbB3 transcript in Hep-2 and KB cells was seen upon vorinostat treatment. We showed that vorinostat induced ubiquitination of EGFR and ErbB2 and targeted them predominantly to lysosome-degradation in all cell lines, while the induction of ErbB3-ubiquitination in CAL27 cells led to proteasomes-degradation. Overall, this study suggests that the vorinostat/gefitinib combination represents a promising therapeutic strategy that warrants further clinical evaluation in SCCHN, including tumors intrinsically resistant to EGFR-inhibitors.

Identification of DeltaEF1 as a novel target that is negatively regulated by LMO2 in T-cell leukemia

The lmo2 gene is a specific oncogene in T-cell leukemia, for its ectopic expression causes both increased pro-T-cell proliferation and differentiation arrest, leading to the onset of leukemia. Notably, DeltaEF1 (also known as ZEB1), a member of zinc finger-homeodomain family transcription factor, also exhibits crucial function in promoting T-cell differentiation. In this study, we found that DeltaEF1 was positively regulated by T-lineage-specific transcriptional regulator GATA3, while ectopically expressed LMO2 targeted to DeltaEF1 promoter by interaction with GATA3 and inhibited DeltaEF1 expression in transcriptional level. Moreover, LMO2 interacted with the N-terminal zinc finger domain of DeltaEF1 protein and inhibited its positive transcriptional regulatory function by this interaction. Taken together, our findings revealed that ectopically expressed LMO2 impaired the function of DeltaEF1 in both transcriptional and protein levels and identified DeltaEF1 as a novel pathogenic target of LMO2 in T-cell leukemia.

Molecular genetics of bladder cancer: Emerging mechanisms of tumor initiation and progression

Urothelial cancer has served as one of the most important sources of information about the mutational events that underlie the development of human solid malignancies. Although "field effects" that affect the entire bladder mucosa appear to initiate disease, tumors develop along 2 distinct biological "tracks" that present vastly different challenges for clinical management. Recent whole genome methodologies have facilitated even more rapid progress in the identification of the molecular mechanisms involved in bladder cancer initiation and progression. Specifically, whole organ mapping combined with high resolution, high throughput SNP analyses have identified a novel class of candidate tumor suppressors ("forerunner genes") that localize near more familiar tumor suppressors but are disrupted at an earlier stage of cancer development. Furthermore, whole genome comparative genomic hybridization (CGH) and mRNA expression profiling have demonstrated that the 2 major subtypes of urothelial cancer (papillary/superficial and non-papillary/muscle-invasive) are truly distinct molecular entities, and in recent work our group has discovered that muscle-invasive tumors express molecular markers characteristic of a developmental process known as "epithelial-to-mesenchymal transition" (EMT). Emerging evidence indicates that urothelial cancers contain subpopulations of tumor-initiating cells ("cancer stem cells") but the phenotypes of these cells in different tumors are heterogeneous, raising questions about whether or not the 2 major subtypes of cancer share a common precursor. This review will provide an overview of these new insights and discuss priorities for future investigation.