Molecular correlates of gefitinib responsiveness in human bladder cancer cells

Progression-associated molecular changes in basal/squamous and sarcomatoid bladder carcinogenesis

The aggressive basal/squamous (Ba/Sq) bladder cancer (BLCA) subtype is often diagnosed at the muscle-invasive stage and can progress to the sarcomatoid variant. Identification of molecular changes occurring during progression from non-muscle-invasive BLCA (NMIBC) to Ba/Sq muscle-invasive BLCA (MIBC) is thus challenging in human disease. We used the N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) mouse model of Ba/Sq MIBC to study longitudinally the molecular changes leading to the Ba/Sq phenotype and to the sarcomatoid variant using IHC and microdissection followed by RNA-seq at all stages of progression. A shift to the Ba/Sq phenotype started in early progression stages. Pathway analysis of gene clusters with coordinated expression changes revealed Shh signaling loss and a shift from fatty acid metabolism to glycolysis. An upregulated cluster, appearing early in carcinogenesis, showed relevance to human disease, identifying NMIBC patients at risk of progression. Similar to the human counterpart, sarcomatoid BBN tumors displayed a Ba/Sq phenotype and epithelial-mesenchymal transition (EMT) features. An EGFR/FGFR1 signaling switch occurred with sarcomatoid dedifferentiation and correlated with EMT. BLCA cell lines with high EMT were the most sensitive to FGFR1 knockout and resistant to EGFR knockout. Taken together, these findings provide insights into the underlying biology of Ba/Sq BLCA progression and sarcomatoid dedifferentiation with potential clinical implications. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Hypoxia-Driven Effects in Cancer: Characterization, Mechanisms, and Therapeutic Implications

Hypoxia, a common feature of solid tumors, greatly hinders the efficacy of conventional cancer treatments such as chemo-, radio-, and immunotherapy. The depletion of oxygen in proliferating and advanced tumors causes an array of genetic, transcriptional, and metabolic adaptations that promote survival, metastasis, and a clinically malignant phenotype. At the nexus of these interconnected pathways are hypoxia-inducible factors (HIFs) which orchestrate transcriptional responses under hypoxia. The following review summarizes current literature regarding effects of hypoxia on DNA repair, metastasis, epithelial-to-mesenchymal transition, the cancer stem cell phenotype, and therapy resistance. We also discuss mechanisms and pathways, such as HIF signaling, mitochondrial dynamics, exosomes, and the unfolded protein response, that contribute to hypoxia-induced phenotypic changes. Finally, novel therapeutics that target the hypoxic tumor microenvironment or interfere with hypoxia-induced pathways are reviewed.

Crosstalk between Epidermal Growth Factor Receptors (EGFR) and integrins in resistance to EGFR tyrosine kinase inhibitors (TKIs) in solid tumors

Cell adhesion to the extracellular matrix (ECM) is important in a variety of physiological and pathologic processes, including development, tumor invasion, and metastasis. Integrin-mediated attachment to ECM proteins has emerged to cue events primitively important for the transformed phenotype of human cancer cells. Cross-talk between integrins and growth factor receptors takes an increasingly prominent role in defining adhesion, motility, and cell growth. This functional interaction has expanded beyond to link integrins with resistance to Tyrosine kinase inhibitors (TKIs) of Epidermal Growth Factor Receptors (EGFRs). In this regard, integrin-mediated adhesion has two separate functions one as a clear collaborator with growth factor receptor signaling and the second as a basic mechanism contributing in Epithelial to Mesenchymal Transition (EMT) which affects response to chemotherapy. This review provides an overview of these mechanisms and describes treatment options for selectively targeting and disrupting integrin interaction to EGFR for cancer therapy.

Clinical and molecular characteristics of bladder urothelial carcinoma subtypes

Bladder urothelial carcinoma (BLCA) is a common malignancy with high heterogeneity. A reasonable molecular subtyping can facilitate biological study and personalized therapy of BLCA. In this study, unsupervised consensus clustering was used to acquire the molecular subtypes of BLCA based on messenger RNA (mRNA) and microRNA (miRNA) data. Gene signature markers and canonical signaling pathways were compared between different subtypes. The Database for Annotation, Visualization and Integrated Discovery (DAVID) was used for the functional annotation of overexpressed genes in different subtypes for Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Three molecular subtypes were identified including C1 (luminal-P53 like), C2 (luminal-other), and C3 (basal-immune-squamous). C2 was different from C1 and C3 in clinical characteristics, including younger, better prognosis, and a higher proportion of papillary, Asian, low-grade, early-stage, lymph node negative, and complete remission patients (P < 0.05). Three molecular subtypes also showed distinct mRNA and miRNA expression patterns. luminal and P53-like markers were highly expressed in subtype C1, luminal markers were highly expressed in subtype C2, and basal, EMT/claudin-low, immune and squamous-differentiation markers were highly expressed in subtype C3. In addition, highly expressed genes in C1 were involved in extracellular signal transduction and cell-cell interaction, highly expressed genes in C2 were associated with oxygen transport, energy and steroid metabolism, and highly expressed genes in C3 were related with inflammatory, immune, cytokine, and signal transduction. BLCA in different molecular subtypes showed different clinical and molecular characteristics and personalized therapy needed to be adopted according to the molecular subtypes.

Epithelial-to-mesenchymal transition correlates with gefitinib resistance in NSCLC cells and the liver X receptor ligand GW3965 reverses gefitinib resistance through inhibition of vimentin

The role of epithelial-to-mesenchymal transition in cancer drug resistance is increasingly acknowledged. We examined whether epithelial-to-mesenchymal transition affects gefitinib resistance in non-small cell lung cancer (NSCLC) cells. Cell viability was detected by CCK-8 assay, VIM expression levels were determined by quantitative real-time polymerase chain reaction. Western blot and immunocytochemistry were performed to determine the protein expression level of vimentin. We observed morphologic differences between gefitinib-sensitive and -insensitive cells. Compared with the sensitive parental cell line, HCC827, vimentin expression levels were increased in HCC827 cells with acquired gefitinib resistance. Vimentin expression was also markedly upregulated in cells with intrinsic gefitinib resistance, and upregulated vimentin expression was correlated with gefitinib sensitivity. Our previous study demonstrated that coadministration of gefitinib and GW3965 resulted in decreased cell proliferation and induced apoptosis. Therefore, we investigated the relationship among GW3965, vimentin, and gefitinib resistance in NSCLC cells by analysis of the expression of vimentin in cells treated with a combination of gefitinib and GW3965. Gefitinib treatment led to increased levels of intracellular vimentin, while combined treatment with gefitinib and GW3965 resulted in decreased vimentin expression levels through reduction of gefitinib drug resistance in NSCLC cells. Overall, these findings suggest that vimentin expression is associated with sensitivity to gefitinib, and our study highlights the potential usefulness of the drug, GW3965, for reversal of gefitinib resistance through inhibition of vimentin expression.

Biomarkers for predicting response to tyrosine kinase inhibitors in drug-sensitive and drug-resistant human bladder cancer cells

The epidermal growth factor receptor (EGFR) family is reportedly overexpressed in bladder cancer, and tyrosine kinase inhibitors (TKIs) have been suggested as treatment. Gefitinib (Iressa®) is a selective inhibitor of the EGFR and lapatinib is a dual inhibitor of both the EGFR and HER2 (human EGFR type 2 receptor). Both compounds compete with the binding of ATP to the tyrosine kinase domain of the respective receptors to inhibit receptor autophosphorylation causing suppression of signal transduction. Unfortunately, resistance to these inhibitors is a major clinical issue. The purpose of the present study was to use protein array analysis to compare the signaling pathway(s) induced by gefitinib and lapatinib, in UM-UC-5 (drug-sensitive) and UM-UC-14 (drug-resistant) bladder cancer cells and to identify molecular markers that may be useful predictors of their efficacy. The results revealed that phosphorylation of EGFR, HER3, Met and ERK1/2 was markedly overexpressed in the sensitive cell line (UM-UC-5) and was strongly inhibited by the TKIs. Other notable differences included decreased phosphorylation of RSK, GSK3, AMPK, Akt and c-Jun by TKIs in the sensitive cells. In contrast, phosphorylated p53 was highly expressed in the resistant cell line (UM-UC-14) and TKIs had no effect in the resistant cells. Overall results suggest that phosphorylated HER3, ERK1/2 and p53 may be used as biomarkers to determine the sensitivity of bladder cancers to TKIs. In particular, a combination of these markers may be more likely to predict the sensitivity to TKIs.

Intrinsic basal and luminal subtypes of muscle-invasive bladder cancer

Whole-genome analyses have revealed that muscle-invasive bladder cancers (MIBCs) are heterogeneous and can be grouped into basal and luminal subtypes that are highly reminiscent of those found in breast cancer. Basal MIBCs are enriched with squamous and sarcomatoid features and are associated with advanced stage and metastatic disease at presentation. Like basal breast cancers, basal bladder tumours contain a claudin-low subtype that is enriched with biomarkers characteristic of epithelial-to-mesenchymal transition. The stem cell transcription factor ΔNp63α controls basal MIBC gene expression, just as it does in basal breast cancers. Luminal MIBCs are enriched with activating FGFR3 and ERBB3 mutations and ERBB2 amplifications, and their gene expression profiles are controlled by peroxisome proliferator activator receptor γ (PPARγ) and possibly also by oestrogen receptor activation. Luminal bladder cancers can be further subdivided into two subtypes, p53-like and luminal, which can be distinguished from one another by different levels of biomarkers that are characteristic of stromal infiltration, cell cycle progression, and proliferation. Importantly, basal bladder cancers are intrinsically aggressive, but are highly sensitive to cisplatin-based combination chemotherapy. Although the luminal subtypes are not as intrinsically aggressive as basal cancers, p53-like tumours are resistant to chemotherapy and might, therefore, represent a problem for treated patients.

Expression signature defined by FOXM1-CCNB1 activation predicts disease recurrence in non-muscle-invasive bladder cancer

PURPOSE

Although standard treatment with transurethral resection and intravesical therapy (IVT) is known to be effective to address the clinical behavior of non-muscle-invasive bladder cancer (NMIBC), many patients fail to respond to the treatment and frequently experience disease recurrence. Here, we aim to identify a prognostic molecular signature that predicts the NMIBC heterogeneity and response to IVT.

EXPERIMENTAL DESIGN

We analyzed the genomic profiles of 102 patients with NMIBC to identify a signature associated with disease recurrence. The validity of the signature was verified in three independent patient cohorts (n = 658). Various statistical methods, including a leave-one-out cross-validation and multivariate Cox regression analyses, were applied to identify a signature. We confirmed an association between the signature and tumor aggressiveness with experimental assays using bladder cancer cell lines.

RESULTS

Gene expression profiling in 102 patients with NMIBC identified a CCNB1 signature associated with disease recurrence, which was validated in another three independent cohorts of 658 patients. The CCNB1 signature was shown to be an independent risk factor by a multivariate analysis and subset stratification according to stage and grade [HR, 2.93; 95% confidence intervals (CI), 1.302-6.594; P = 0.009]. The subset analysis also revealed that the signature could identify patients who would benefit from IVT. Finally, gene network analyses and experimental assays indicated that NMIBC recurrence could be mediated by FOXM1-CCNB1-Fanconi anemia pathways.

CONCLUSIONS

The CCNB1 signature represents a promising diagnostic tool to identify patients with NMIBC who have a high risk of recurrence and to predict response to IVT.

Epithelial mesenchymal transition status is associated with anti-cancer responses towards receptor tyrosine-kinase inhibition by dovitinib in human bladder cancer cells

Background

Dovitinib (TKI-258) is a receptor tyrosine kinase (RTK) inhibitor targeting fibroblast growth factor receptor (FGFR) and further related RTKs. TKI-258 is under investigation as anticancer drug for the treatment of various cancers including bladder cancer with aberrant RTK signaling. Here, we analyzed the responses of ten human bladder cancer cell lines towards TKI-258 treatment in relation to the epithelial mesenchymal transition (EMT) status of the cells.

Methods

Expression of epithelial marker E-cadherin as well as mesenchymal markers N-cadherin and vimentin was determined by quantitative RT-PCR and Western-blot in RNA and protein extracts from the cultured cell lines. The cell responses were analyzed upon addition of TKI-258 by viability/proliferation (XTT assay) and colony formation assay for measurement of cell contact independent growth.

Results

The investigated bladder cancer cell lines turned out to display quite different EMT patterns as indicated by the abundance of E-cadherin or N-cadherin and vimentin. Protein and mRNA levels of the respective components strongly correlated. Based on E-cadherin and N-cadherin mRNA levels that were expressed approximately mutual exclusively, an EMT-score was calculated for each cell line. A high EMT-score indicated mesenchymal-like cells and a low EMT-score epithelial-like cells. Then, we determined the IC₅₀ values for TKI-258 by dose response curves (0-12 μM TKI-258) in XTT assays for each cell line. Also, we measured the clonogenic survival fraction after adding TKI-258 (1 μM) by colony formation assay. We observed significant correlations between EMT-score and IC₅₀ values (r = 0.637, p = 0.0474) and between EMT-score and clonogenic survival fraction (r = 0.635, p = 0.0483) as analyzed by linear regression analyses.

Conclusions

In sum, we demonstrated that the EMT status based on E-cadherin and N-cadherin mRNA levels may be useful to predict responses towards TKI-258 treatment in bladder cancer.

ERK1/2 blockade prevents epithelial-mesenchymal transition in lung cancer cells and promotes their sensitivity to EGFR inhibition

Overcoming cellular mechanisms of de novo and acquired resistance to drug therapy remains a central challenge in the clinical management of many cancers, including non-small cell lung cancer (NSCLC). Although much work has linked the epithelial-mesenchymal transition (EMT) in cancer cells to the emergence of drug resistance, it is less clear where tractable routes may exist to reverse or inhibit EMT as a strategy for drug sensitization. Here, we demonstrate that extracellular signal-regulated kinase (ERK) 1/2 (mitogen-activated protein kinase 3/1, MAPK3/1) signaling plays a key role in directing the mesenchymal character of NSCLC cells and that blocking ERK signaling is sufficient to heighten therapeutic responses to EGF receptor (EGFR) inhibitors. MEK1/2 (MAPKK1/2) inhibition promoted an epithelial phenotype in NSCLC cells, preventing induction of EMT by exogenous TGF-β. Moreover, in cells exhibiting de novo or acquired resistance to the EGFR inhibitor gefitinib, MEK inhibition enhanced the sensitivity to gefitinib and slowed cell migration. These effects only occurred, however, if MEK was inhibited for a period sufficient to trigger changes in EMT marker expression. Consistent with these findings, changes in EMT phenotypes and markers were also induced by the expression of mutant KRAS in a MEK-dependent manner. Our results suggest that prolonged exposure to MEK or ERK inhibitors may not only restrain EMT but also overcome naïve or acquired resistance of NSCLC to EGFR-targeted therapy in the clinic.

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.

Targeted agents in second-line bladder cancer therapy

The treatment of metastasized urothelial cancer has been evolving in recent years. In particular, in the second-line setting after the failure of platinum-containing therapy, options are few and besides vinflunine, the recently approved standard in Europe, well-designed highly selective clinical trials may be possible alternatives for patients in this palliative situation. However, targeted therapy approaches have not achieved the same results in urothelial cancer as for instance in renal cell carcinoma. Many of the new targeted drugs have been investigated as single agents in phase II clinical trials without convincing oncologic outcome. This review aims to highlight the most relevant clinical studies examining targeted agents in the second-line setting of metastasized transitional carcinoma of the urothelium.

Fibroblast growth factor receptors-1 and -3 play distinct roles in the regulation of bladder cancer growth and metastasis: implications for therapeutic targeting

Fibroblast growth factor receptors (FGFRs) are activated by mutation and overexpressed in bladder cancers (BCs), and FGFR inhibitors are currently being evaluated in clinical trials in BC patients. However, BC cells display marked heterogeneity in their responses to FGFR inhibitors, and the biological mechanisms underlying this heterogeneity are not well defined. Here we used a novel inhibitor of FGFRs 1–3 and RNAi to determine the effects of inhibiting FGFR1 or FGFR3 in a panel of human BC cell lines. We observed that FGFR1 was expressed in BC cells that also expressed the “mesenchymal” markers ZEB1 and vimentin, whereas FGFR3 expression was restricted to the E-cadherin- and p63-positive “epithelial” subset. Sensitivity to the growth-inhibitory effects of BGJ-398 was also restricted to the “epithelial” BC cells and it correlated directly with FGFR3 mRNA levels but not with the presence of activating FGFR3 mutations. In contrast, BGJ-398 did not strongly inhibit proliferation but did block invasion in the “mesenchymal” BC cells in vitro. Similarly, BGJ-398 did not inhibit primary tumor growth but blocked the production of circulating tumor cells (CTCs) and the formation of lymph node and distant metastases in mice bearing orthotopically implanted “mesenchymal” UM-UC3 cells. Together, our data demonstrate that FGFR1 and FGFR3 have largely non-overlapping roles in regulating invasion/metastasis and proliferation in distinct “mesenchymal” and “epithelial” subsets of human BC cells. The results suggest that the tumor EMT phenotype will be an important determinant of the biological effects of FGFR inhibitors in patients.

A novel mechanism of PPAR gamma induction via EGFR signalling constitutes rational for combination therapy in bladder cancer

Background

Two signalling molecules that are attractive for targeted therapy are the epidermal growth factor receptor (EGFR) and the peroxisome proliferator-activated receptor gamma (PPARγ). We investigated possible crosstalk between these 2 pathways, particularly in light of the recent evidence implicating PPARγ for anticancer therapy.

Principal Findings

As evaluated by MTT assays, gefitinib (EGFR inhibitor) and DIM-C (PPARγ agonist) inhibited growth of 9 bladder cancer cell lines in a dose-dependent manner but with variable sensitivity. In addition, combination of gefitinib and DIM-C demonstrated maximal inhibition of cell proliferation compared to each drug alone. These findings were confirmed in vivo, where combination therapy maximally inhibited tumor growth in contrast to each treatment alone when compared to control (p<0.04). Induction of PPARγ expression along with nuclear accumulation was observed in response to increasing concentrations of gefitinib via activation of the transcription factor CCAT/enhancer-binding protein-β (CEBP-β). In these cell lines, DIM-C significantly sensitized bladder cancer cell lines that were resistant to EGFR inhibition in a schedule-specific manner.

Conclusion

These results suggest that PPARγ agonist DIM-C can be an excellent alternative to bladder tumors resistant to EGFR inhibition and combination efficacy might be achieved in a schedule-specific manner.

Current preclinical models for the advancement of translational bladder cancer research

Bladder cancer is a common disease representing the fifth most diagnosed solid tumor in the United States. Despite this, advances in our understanding of the molecular etiology and treatment of bladder cancer have been relatively lacking. This is especially apparent when recent advances in other cancers, such as breast and prostate, are taken into consideration. The field of bladder cancer research is ready and poised for a series of paradigm-shifting discoveries that will greatly impact the way this disease is clinically managed. Future preclinical discoveries with translational potential will require investigators to take full advantage of recent advances in molecular and animal modeling methodologies. We present an overview of current preclinical models and their potential roles in advancing our understanding of this deadly disease and for advancing care.

Epithelial-mesenchymal transition, a novel target of sulforaphane via COX-2/MMP2, 9/Snail, ZEB1 and miR-200c/ZEB1 pathways in human bladder cancer cells

Metastasis and recurrence of bladder cancer are the main reasons for its poor prognosis and high mortality rates. Because of its biological activity and high metabolic accumulation in urine, sulforaphane, a phytochemical exclusively occurring in cruciferous vegetables, has a powerful and specific potential for preventing bladder cancer. In this paper, sulforaphane is shown to significantly suppress a variety of biochemical pathways including the attachment, invasion, migration and chemotaxis motion in malignant transitional bladder cancer T24 cells. Transfection with cyclooxygenase-2 (COX-2) overexpression plasmid largely abolished inhibition of MMP2/9 expression as well as cell invasive capability by sulforaphane. Moreover, sulforaphane inhibited the epithelial-to-mesenchymal transition (EMT) process which underlies tumor cell invasion and migration mediated by E-cadherin induction through reducing transcriptional repressors, such as ZEB1 and Snail. Under conditions of over-expression of COX-2 and/or MMP2/9, sulforaphane was still able to induce E-cadherin or reduce Snail/ZEB1 expression, suggesting that additional pathways might be involved. Further studies indicated that miR-200c played a role in the regulation of E-cadherin via the ZEB1 repressor but not by the Snail repressor. In conclusion, the EMT and two recognized signaling pathways (COX-2/MMP2,9/ ZEB1, Snail and miR-200c/ZEB1) are all targets for sulforaphane. This study indicated that sulforaphane may possess therapeutic potential in preventing recurrence of human bladder cancer.

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.

The major vault protein mediates resistance to epidermal growth factor receptor inhibition in human hepatoma cells

To better understand the response of HCC to EGFR inhibition, we analyzed factors connected to the resistance of HCC cells against gefitinib. Sensitive HCC3 cells co-expressed EGFR and ErbB3 but lacked kinase-domain mutations in EGFR. Interestingly, expression of MVP was restricted to resistant cell lines, whereas ABCB1 and ABCC1 showed no association with gefitinib resistance. Moreover, ectopic MVP expression in HCC3 cells decreased gefitinib sensitivity, increased AKT phosphorylation and reduced the expression of inflammatory pathway-associated genes, whereas silencing of MVP in Hep3B and HepG2 cells increased sensitivity. These findings suggest MVP as a novel player in resistance against EGFR inhibition.

p63 expression defines a lethal subset of muscle-invasive bladder cancers

Background

p63 is a member of the p53 family that has been implicated in maintenance of epithelial stem cell compartments. Previous studies demonstrated that p63 is downregulated in muscle-invasive bladder cancers, but the relationship between p63 expression and survival is not clear.

Methodology/Principal Findings

We used real-time PCR to characterize p63 expression and several genes implicated in epithelial-to-mesenchymal transition (EMT) in human bladder cancer cell lines (n = 15) and primary tumors (n = 101). We correlated tumor marker expression with stage, disease-specific (DSS), and overall survival (OS). Expression of E-cadherin and p63 correlated directly with one another and inversely with expression of the mesenchymal markers Zeb-1, Zeb-2, and vimentin. Non-muscle-invasive (Ta and T1) bladder cancers uniformly expressed high levels of E-cadherin and p63 and low levels of the mesenchymal markers. Interestingly, a subset of muscle-invasive (T2–T4) tumors maintained high levels of E-cadherin and p63 expression. As expected, there was a strongly significant correlation between EMT marker expression and muscle invasion (p<0.0001). However, OS was shorter in patients with muscle-invasive tumors that retained p63 (p = 0.007).

Conclusions/Significance

Our data confirm that molecular markers of EMT are elevated in muscle-invasive bladder cancers, but interestingly, retention of the “epithelial” marker p63 in muscle-invasive tumors is associated with a worse outcome.

Double-blind, randomized trial of docetaxel plus vandetanib versus docetaxel plus placebo in platinum-pretreated metastatic urothelial cancer

PURPOSE

Vandetanib is an oral once-daily tyrosine kinase inhibitor with activity against vascular endothelial growth factor receptor 2 and epidermal growth factor receptor. Vandetanib in combination with docetaxel was assessed in patients with advanced urothelial cancer (UC) who progressed on prior platinum-based chemotherapy.

PATIENTS AND METHODS

The primary objective was to determine whether vandetanib 100 mg plus docetaxel 75 mg/m(2) intravenously every 21 days prolonged progression-free survival (PFS) versus placebo plus docetaxel. The study was designed to detect a 60% improvement in median PFS with 80% power and one-sided α at 5%. Patients receiving docetaxel plus placebo had the option to cross over to single-agent vandetanib at progression. Overall survival (OS), overall response rate (ORR), and safety were secondary objectives.

RESULTS

In all, 142 patients were randomly assigned and received at least one dose of therapy. Median PFS was 2.56 months for the docetaxel plus vandetanib arm versus 1.58 months for the docetaxel plus placebo arm, and the hazard ratio for PFS was 1.02 (95% CI, 0.69 to 1.49; P = .9). ORR and OS were not different between both arms. Grade 3 or higher toxicities were more commonly seen in the docetaxel plus vandetanib arm and included rash/photosensitivity (11% v 0%) and diarrhea (7% v 0%). Among 37 patients who crossed over to single-agent vandetanib, ORR was 3% and OS was 5.2 months.

CONCLUSION

In this platinum-pretreated population of advanced UC, the addition of vandetanib to docetaxel did not result in a significant improvement in PFS, ORR, or OS. The toxicity of vandetanib plus docetaxel was greater than that for vendetanib plus placebo. Single-agent vandetanib activity was minimal.

Antitumour efficacy of MEK inhibitors in human lung cancer cells and their derivatives with acquired resistance to different tyrosine kinase inhibitors

Background:

To study the molecular mechanisms regulating cancer cell resistance to four different tyrosine kinase inhibitors (TKIs): erlotinib, gefitinib, vandetanib and sorafenib.

Methods:

An in vitro model of acquired resistance to these TKIs was developed by continuously treating the human lung adenocarcinoma cell line CALU-3 with escalating doses of each drug. Transcriptional profiling was performed with Agilent whole genome microarrays. Western blot analysis, enzyme-linked immunosorbent (ELISA), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation, migration, invasion and anchorage-independent colony growth assays were conducted in vitro and experiments with established xenografts in athymic nude mice were performed in vivo in parental (P) and TKI-resistant (R) CALU-3 cell lines.

Results:

As compared with P-CALU-3 cells, in TKI-R CALU-3 cell lines a significant increase in the expression of activated, phosphorylated MET, IGF-1R, AKT, MEK, MAPK and of survivin was observed. Downregulation of E-cadherin and amphiregulin mRNAs and upregulation of vimentin, VE-cadherin, HIF-1α and vascular endothelial growth factor receptor-1 mRNAs were observed in all four TKI-R CALU-3 cell lines. All four TKI-R CALU-3 cells showed increased invasion, migration and anchorage-independent growth. Together, these data suggest epithelial to mesenchymal transition (EMT) in TKI-R CALU-3 cells. Treatment with several agents that target AKT, MET or IGF-1R did not affect TKI-R CALU-3 cell proliferation. In contrast, treatment with MSC19363669B and selumetinib, two selective MEK inhibitors, caused inhibition of cell proliferation, invasion, migration, anchorage-independent growth in vitro and of tumour growth in vivo of all four TKI-R CALU-3 cell lines.

Conclusion:

These data suggest that resistance to four different TKIs is characterised by EMT, which is MEK-inhibitor sensitive in human CALU-3 lung adenocarcinoma.

A systems view of epithelial-mesenchymal transition signaling states

Epithelial–mesenchymal transition (EMT) is an important contributor to the invasion and metastasis of epithelial-derived cancers. While considerable effort has focused in the regulators involved in the transition process, we have focused on consequences of EMT to prosurvival signaling. Changes in distinct metastable and ‘epigentically-fixed’ EMT states were measured by correlation of protein, phosphoprotein, phosphopeptide and RNA transcript abundance. The assembly of 1167 modulated components into functional systems or machines simplified biological understanding and increased prediction confidence highlighting four functional groups: cell adhesion and migration, metabolism, transcription nodes and proliferation/survival networks. A coordinate metabolic reduction in a cluster of 17 free-radical stress pathway components was observed and correlated with reduced glycolytic and increased oxidative phosphorylation enzyme capacity, consistent with reduced cell cycling and reduced need for macromolecular biosynthesis in the mesenchymal state. An attenuation of EGFR autophosphorylation and a switch from autocrine to paracrine-competent EGFR signaling was implicated in the enablement of tumor cell chemotaxis. A similar attenuation of IGF1R, MET and RON signaling with EMT was observed. In contrast, EMT increased prosurvival autocrine IL11/IL6-JAK2-STAT signaling, autocrine fibronectin-integrin α5β1 activation, autocrine Axl/Tyro3/PDGFR/FGFR RTK signaling and autocrine TGFβR signaling. A relatively uniform loss of polarity and cell–cell junction linkages to actin cytoskeleton and intermediate filaments was measured at a systems level. A more heterogeneous gain of ECM remodeling and associated with invasion and migration was observed. Correlation to stem cell, EMT, invasion and metastasis datasets revealed the greatest similarity with normal and cancerous breast stem cell populations, CD49f^hi/EpCAM^-/lo and CD44^hi/CD24^lo, respectively.

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.

Evidence for mesenchymal-like sub-populations within squamous cell carcinomas possessing chemoresistance and phenotypic plasticity

Variable drug responses among malignant cells within individual tumors may represent a barrier to their eradication using chemotherapy. Carcinoma cells expressing mesenchymal markers resist conventional and epidermal growth factor receptor (EGFR)-targeted chemotherapy. Here we evaluated whether mesenchymal-like subpopulations within human squamous cell carcinomas (SCCs) with predominantly epithelial features contribute to overall therapy resistance. We identified a mesenchymal-like subset expressing low E-cadherin (Ecad-lo) and high vimentin (Vim-hi) within upper aerodigestive tract SCCs. This subset was both isolated from cell lines and identified in xenografts and primary clinical specimens. The Ecad-lo subset contained more low-turnover cells, correlating with resistance to the conventional chemotherapeutic paclitaxel in vitro. Epidermal growth factor (EGF) induced less stimulation of the MAP kinase and PI3-kinase pathways in Ecad-lo cells, which was likely due to lower EGFR expression in this subset and correlated with in vivo resistance to the EGFR-targeted antibody cetuximab. The Ecad-lo and high E-cadherin (Ecad-hi) subsets were dynamic in phenotype, showing the capacity to repopulate each other from single cell clones. Taken together, these results provide evidence for a low-turnover, mesenchymal-like subpopulation in SCCs with diminished EGFR pathway function and intrinsic resistance to conventional and EGFR-targeted chemotherapies.

Drugs that target specificity proteins downregulate epidermal growth factor receptor in bladder cancer cells

The epidermal growth factor receptor (EGFR) is an important chemotherapeutic target for tyrosine kinase inhibitors and antibodies that block the extracellular domain of EGFR. Betulinic acid (BA) and curcumin inhibited bladder cancer cell growth and downregulated specificity protein (Sp) transcription factors, and this was accompanied by decreased expression of EGFR mRNA and protein levels. EGFR, a putative Sp-regulated gene, was also decreased in cells transfected with a cocktail (iSp) containing small inhibitory RNAs for Sp1, Sp3, and Sp4, and RNA interference with individual Sp knockdown indicated that EGFR expression was primarily regulated by Sp1 and Sp3. BA, curcumin, and iSp also decreased phosphorylation of Akt in these cells, and downregulation of EGFR by BA, curcumin, and iSp was accompanied by induction of LC3 and autophagy, which is consistent with recent studies showing that EGFR suppresses autophagic cell death. The results show that EGFR is an Sp-regulated gene in bladder cancer, and drugs such as BA and curcumin that repress Sp proteins also ablate EGFR expression. Thus, compounds such as curcumin and BA that downregulate Sp transcription factors represent a novel class of anticancer drugs that target EGFR in bladder cancer cells and tumors by inhibiting receptor expression.

Role of epithelial-to-mesenchymal transition (EMT) in drug sensitivity and metastasis in bladder cancer

Epithelial-to-mesenchymal transition (EMT) is a process that plays essential roles in development and wound healing that is characterized by loss of homotypic adhesion and cell polarity and increased invasion and migration. At the molecular level, EMT is characterized by loss of E-cadherin and increased expression of several transcriptional repressors of E-cadherin expression (Zeb-1, Zeb-2, Twist, Snail, and Slug). Early work established that loss of E-cadherin and increased expression of MMP-9 was associated with a poor clinical outcome in patients with urothelial tumors, suggesting that EMT might also be associated with bladder cancer progression and metastasis. More recently, we have used global gene expression profiling to characterize the molecular heterogeneity in human urothelial cancer cell lines (n = 20) and primary patient tumors, and unsupervised clustering analyses revealed that the cells naturally segregate into two discrete "epithelial" and "mesenchymal" subsets, the latter consisting entirely of muscle-invasive tumors. Importantly, sensitivity to inhibitors of the epidermal growth factor receptor (EGFR) or type-3 fibroblast growth factor receptor (FGFR3) was confined to the "epithelial" subset, and sensitivity to EGFR inhibitors could be reestablished by micro-RNA-mediated molecular reversal of EMT. The results suggest that EMT coordinately regulates drug resistance and muscle invasion/metastasis in urothelial cancer and is a dominant feature of overall cancer biology.

[Tumors of the urinary system. Current and old problems]

Principally there are two different types of bladder cancer. Non-invasive papillary low grade tumors (pTa G1-G2) are genetically stable, recur frequently but show a low risk of progression. On the other hand there are high grade tumors (pT1-4, carcinoma in situ), which are genetically unstable, show biologically aggressive behaviour and progress. The distinction between non-invasive (pTa) and minimal-invasive (pT1) is one of the most challenging areas in bladder pathology. Due to the lack of appropriate auxiliary analysis the diagnosis is based entirely on histopathology. P53 immunohistochemistry can be helpful in the assessment of recurring high grade neoplasia. Targeted therapy in bladder cancer is particularly interesting, since a high number of oncogenes are activated and overexpressed (e.g. HER2 and EGFR).

Epithelial-mesenchymal transitions in development and disease

The epithelial to mesenchymal transition (EMT) plays crucial roles in the formation of the body plan and in the differentiation of multiple tissues and organs. EMT also contributes to tissue repair, but it can adversely cause organ fibrosis and promote carcinoma progression through a variety of mechanisms. EMT endows cells with migratory and invasive properties, induces stem cell properties, prevents apoptosis and senescence, and contributes to immunosuppression. Thus, the mesenchymal state is associated with the capacity of cells to migrate to distant organs and maintain stemness, allowing their subsequent differentiation into multiple cell types during development and the initiation of metastasis.

miR-200 expression regulates epithelial-to-mesenchymal transition in bladder cancer cells and reverses resistance to epidermal growth factor receptor therapy

PURPOSE

The epithelial-to-mesenchymal transition (EMT) is a cell development-regulated process in which noncoding RNAs act as crucial modulators. Recent studies have implied that EMT may contribute to resistance to epidermal growth factor receptor (EGFR)-directed therapy. The aims of this study were to determine the potential role of microRNAs (miRNA) in controlling EMT and the role of EMT in inducing the sensitivity of human bladder cancer cells to the inhibitory effects of the anti-EGFR therapy.

EXPERIMENTAL DESIGN

miRNA array screening and real-time reverse transcription-PCR were used to identify and validate the differential expression of miRNAs involved in EMT in nine bladder cancer cell lines. A list of potential miR-200 direct targets was identified through the TargetScan database. The precursor of miR-200b and miR-200c was expressed in UMUC3 and T24 cells using a retrovirus or a lentivirus construct, respectively. Protein expression and signaling pathway modulation, as well as intracellular distribution of EGFR and ERRFI-1, were validated through Western blot analysis and confocal microscopy, whereas ERRFI-1 direct target of miR-200 members was validated by using the wild-type and mutant 3'-untranslated region/ERRFI-1/luciferse reporters.

RESULTS

We identified a tight association between the expression of miRNAs of the miR-200 family, epithelial phenotype, and sensitivity to EGFR inhibitors-induced growth inhibition in bladder carcinoma cell lines. Stable expression of miR-200 in mesenchymal UMUC3 cells increased E-cadherin levels, decreased expression of ZEB1, ZEB2, ERRFI-1, and cell migration, and increased sensitivity to EGFR-blocking agents. The changes in EGFR sensitivity by silencing or forced expression of ERRFI-1 or by miR-200 expression have also been validated in additional cell lines, UMUC5 and T24. Finally, luciferase assays using 3'-untranslated region/ERRFI-1/luciferase and miR-200 cotransfections showed that the direct down-regulation of ERRFI-1 was miR-200-dependent because mutations in the two putative miR-200-binding sites have rescued the inhibitory effect.

CONCLUSIONS

Members of the miR-200 family appear to control the EMT process and sensitivity to EGFR therapy in bladder cancer cells and the expression of miR-200 is sufficient to restore EGFR dependency at least in some of the mesenchymal bladder cancer cells. The targets of miR-200 include ERRFI-1, which is a novel regulator of EGFR-independent growth.

miR-200 expression regulates epithelial-to-mesenchymal transition in bladder cancer cells and reverses resistance to epidermal growth factor receptor therapy

PURPOSE

The epithelial-to-mesenchymal transition (EMT) is a cell development-regulated process in which noncoding RNAs act as crucial modulators. Recent studies have implied that EMT may contribute to resistance to epidermal growth factor receptor (EGFR)-directed therapy. The aims of this study were to determine the potential role of microRNAs (miRNA) in controlling EMT and the role of EMT in inducing the sensitivity of human bladder cancer cells to the inhibitory effects of the anti-EGFR therapy.

EXPERIMENTAL DESIGN

miRNA array screening and real-time reverse transcription-PCR were used to identify and validate the differential expression of miRNAs involved in EMT in nine bladder cancer cell lines. A list of potential miR-200 direct targets was identified through the TargetScan database. The precursor of miR-200b and miR-200c was expressed in UMUC3 and T24 cells using a retrovirus or a lentivirus construct, respectively. Protein expression and signaling pathway modulation, as well as intracellular distribution of EGFR and ERRFI-1, were validated through Western blot analysis and confocal microscopy, whereas ERRFI-1 direct target of miR-200 members was validated by using the wild-type and mutant 3'-untranslated region/ERRFI-1/luciferse reporters.

RESULTS

We identified a tight association between the expression of miRNAs of the miR-200 family, epithelial phenotype, and sensitivity to EGFR inhibitors-induced growth inhibition in bladder carcinoma cell lines. Stable expression of miR-200 in mesenchymal UMUC3 cells increased E-cadherin levels, decreased expression of ZEB1, ZEB2, ERRFI-1, and cell migration, and increased sensitivity to EGFR-blocking agents. The changes in EGFR sensitivity by silencing or forced expression of ERRFI-1 or by miR-200 expression have also been validated in additional cell lines, UMUC5 and T24. Finally, luciferase assays using 3'-untranslated region/ERRFI-1/luciferase and miR-200 cotransfections showed that the direct down-regulation of ERRFI-1 was miR-200-dependent because mutations in the two putative miR-200-binding sites have rescued the inhibitory effect.

CONCLUSIONS

Members of the miR-200 family appear to control the EMT process and sensitivity to EGFR therapy in bladder cancer cells and the expression of miR-200 is sufficient to restore EGFR dependency at least in some of the mesenchymal bladder cancer cells. The targets of miR-200 include ERRFI-1, which is a novel regulator of EGFR-independent growth.

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

PURPOSE

Although the epidermal growth factor receptor (EGFR) is overexpressed in a majority of head and neck squamous cell carcinomas (HNSCC), only a minority of patients derive substantial clinical benefit from EGFR inhibitors. We initiated the present study to identify the mechanisms underlying erlotinib resistance in a panel of HNSCC cell lines.

METHODS

We used [(3)H]thymidine incorporation to characterize the heterogeneity of responsiveness to erlotinib-mediated growth inhibition in a panel of 27 human HNSCC cells. We characterized the molecular mechanisms involved in resistance using a representative subset of six erlotinib-sensitive and erlotinib-resistant HNSCC lines.

RESULTS

Erlotinib had heterogeneous effects on DNA synthesis in HNSCC cells that correlated closely with molecular markers of epithelial to mesenchymal transition (EMT). Specifically, the drug-sensitive lines expressed high levels of E-cadherin and showed limited invasion and migration capabilities. In contrast, the erlotinib-resistant HNSCC lines expressed high levels of the E-cadherin repressor delta-crystallin enhancer binding factor 1 (deltaEF1; Zeb-1) and other mesenchymal markers and low levels of E-cadherin, and they were highly invasive and migratory. Small interfering RNA-mediated knockdown of deltaEF1 in the erlotinib-resistant cell lines (1386LN and UMSCC1) resulted in up-regulation of E-cadherin and increased sensitivity to erlotinib in an E-cadherin-dependent manner.

CONCLUSIONS

DeltaEF1 controls the mesenchymal phenotype and drives erlotinib resistance in HNSCC cells. E-cadherin and deltaEF1 may prove to be useful markers in predicting EGFR inhibitor responsiveness.

Quantum dot-based quantification revealed differences in subcellular localization of EGFR and E-cadherin between EGFR-TKI sensitive and insensitive cancer cells

Nanoparticle quantum dots (QDs) provide sharper and more photostable fluorescent signals than organic dyes, allowing quantification of multiple biomarkers simultaneously. In this study, we quantified the expression of epidermal growth factor receptor (EGFR) and E-cadherin (E-cad) in the same cells simultaneously by using secondary antibody-conjugated QDs with two different emission wavelengths (QD605 and QD565) and compared the cellular distribution of EGFR and E-cad between EGFR-tyrosine kinase inhibitor (TKI)-insensitive and -sensitive lung and head and neck cancer cell lines. Relocalization of EGFR and E-cad upon treatment with the EGFR-TKI erlotinib in the presence of EGF was visualized and analyzed quantitatively. Our results showed that QD-immunocytochemistry (ICC)-based technology can not only quantify basal levels of multiple biomarkers but also track the localization of the biomarkers upon biostimulation. With this new technology we found that in EGFR-TKI-insensitive cells, EGFR and E-cad were located mainly in the cytoplasm; while in sensitive cells, they were found mainly on the cell membrane. After induction with EGF, both EGFR and E-cad internalized to the cytoplasm, but the internalization capability in sensitive cells was greater than that in insensitive cells. Quantification also showed that inhibition of EGF-induced EGFR and E-cad internalization by erlotinib in the sensitive cells was stronger than that in the insensitive cells. These studies demonstrate substantial differences between EGFR-TKI-insensitive and -sensitive cancer cells in EGFR and E-cad expression and localization both at the basal level and in response to EGF and erlotinib. QD-based analysis facilitates the understanding of the features of EGFR-TKI-insensitive versus -sensitive cancer cells and may be used in the prediction of patient response to EGFR-targeted therapy.

Chemoresistant tumor cell lines display altered epidermal growth factor receptor and HER3 signaling and enhanced sensitivity to gefitinib

Deregulated signaling through the epidermal growth factor receptor (EGFR) is involved in chemoresistance. To identify the molecular determinants of sensitivity to the EGFR inhibitor gefitinib (Iressa, ZD1839) in chemoresistance, we compared the response of matched chemosensitive and chemoresistant glioma and ovarian cancer cell lines. We found that chemoresistant cell lines were 2- to 3-fold more sensitive to gefitinib growth-inhibitory effects, because of decreased proliferation rather than survival. Sensitivity to gefitinib correlated with overexpression and constitutive phosphorylation of HER2 and HER3, but not EGFR, altered HER ligand expression, and enhanced activation of EGF-triggered EGFR pathway. No activating mutations were found in EGFR. Gefitinib fully inhibited EGF-induced and constitutive Akt activation only in chemoresistant cells. In parallel, gefitinib downregulated constitutively phosphorylated HER2 and HER3, and activated GSK3beta with a concomitant degradation of cyclin D1. Ectopically overexpressed HER2 on its own was insufficient to sensitize chemonaive cells to gefitinib. pHER3 coimmunoprecipitated with p85-PI3K in chemoresistant cells and gefitinib dissociated these complexes. siRNA-mediated inhibition of HER3 decreased constitutive activation of Akt and sensitivity to gefitinib in chemoresistant cells. Our study indicates that in chemoresistant cells gefitinib inhibits both an enhanced EGF-triggered pathway and a constitutive HER3-mediated Akt activation, indicating that inhibition of HER3 together with that of EGFR could be relevant in chemorefractory tumors. Furthermore, in combination experiments gefitinib enhanced the effects of coadministered drugs more in chemoresistant than chemosensitive ovarian cancer cells. Combined treatment might be therapeutically beneficial in chemoresistant tumors from ovary and likely from other tissues.

Feedback mechanisms promote cooperativity for small molecule inhibitors of epidermal and insulin-like growth factor receptors

Epidermal growth factor receptor (EGFR) and insulin-like growth factor-I receptor (IGF-IR) can cooperate to regulate tumor growth and survival, and synergistic growth inhibition has been reported for combined blockade of EGFR and IGF-IR. However, in preclinical models, only a subset of tumors exhibit high sensitivity to this combination, highlighting the potential need for patient selection to optimize clinical efficacy. Herein, we have characterized the molecular basis for cooperative growth inhibition upon dual EGFR and IGF-IR blockade and provide biomarkers that seem to differentiate response. We find for epithelial, but not for mesenchymal-like, tumor cells that Akt is controlled cooperatively by EGFR and IGF-IR. This correlates with synergistic apoptosis and growth inhibition in vitro and growth regression in vivo upon combined blockade of both receptors. We identified two molecular aspects contributing to synergy: (a) inhibition of EGFR or IGF-IR individually promotes activation of the reciprocal receptor; (b) inhibition of EGFR-directed mitogen-activated protein kinase (MAPK) shifts regulation of Akt from EGFR toward IGF-IR. Targeting the MAPK pathway through downstream MAPK/extracellular signal-regulated kinase kinase (MEK) antagonism similarly promoted IGF-driven pAkt and synergism with IGF-IR inhibition. Mechanistically, we find that inhibition of the MAPK pathway circumvents a negative feedback loop imposed on the IGF-IR- insulin receptor substrate 1 (IRS-1) signaling complex, a molecular scenario that parallels the negative feedback loop between mTOR-p70S6K and IRS-1 that mediates rapamycin-directed IGF-IR signaling. Collectively, these data show that resistance to inhibition of MEK, mTOR, and EGFR is associated with enhanced IGF-IR-directed Akt signaling, where all affect feedback loops converging at the level of IRS-1.

Human Mena+11a isoform serves as a marker of epithelial phenotype and sensitivity to epidermal growth factor receptor inhibition in human pancreatic cancer cell lines

PURPOSE

hMena, member of the enabled/vasodilator-stimulated phosphoprotein family, is a cytoskeletal protein that is involved in the regulation of cell motility and adhesion. The aim of this study was to determine whether or not the expression of hMena isoforms correlated with sensitivity to EGFR tyrosine kinase inhibitors and could serve as markers with potential clinical use.

EXPERIMENTAL DESIGN

Human pancreatic ductal adenocarcinoma cell lines were characterized for in vitro sensitivity to erlotinib, expression of HER family receptors, markers of epithelial to mesenchymal transition, and expression of hMena and its isoform hMena(+11a). The effects of epidermal growth factor (EGF) and erlotinib on hMena expression as well as the effect of hMena knockdown on cell proliferation were also evaluated.

RESULTS

hMena was detected in all of the pancreatic tumor cell lines tested as well as in the majority of the human tumor samples [primary (92%) and metastatic (86%)]. Intriguingly, in vitro hMena(+11a) isoform was specifically associated with an epithelial phenotype, EGFR dependency, and sensitivity to erlotinib. In epithelial BxPC3 cells, epidermal growth factor up-regulated hMena/hMena(+11a) and erlotinib down-regulated expression. hMena knockdown reduced cell proliferation and mitogen-activated protein kinase and AKT activation in BxPC3 cells, and promoted the growth inhibitory effects of erlotinib.

CONCLUSIONS

Collectively, our data indicate that the hMena(+11a) isoform is associated with an epithelial phenotype and identifies EGFR-dependent cell lines that are sensitive to the EGFR inhibitor erlotinib. The availability of anti-hMena(+11a)-specific probes may offer a new tool in pancreatic cancer management if these results can be verified prospectively in cancer patients.

Molecular signature and therapeutic perspective of the epithelial-to-mesenchymal transitions in epithelial cancers

The mechanisms involved in the epithelial to mesenchymal transition (EMT) are integrated in concert with master developmental and oncogenic pathways regulating in tumor growth, angiogenesis, metastasis, as well as the reprogrammation of specific gene repertoires ascribed to both epithelial and mesenchymal cells. Consequently, it is not unexpected that EMT has profound impacts on the neoplastic progression, patient survival, as well as the resistance of cancers to therapeutics (taxol, vincristine, oxaliplatin, EGF-R targeted therapy and radiotherapy), independent of the "classical" resistance mechanisms linked to genotoxic drugs. New therapeutic combinations using genotoxic agents and/or EMT signaling inhibitors are therefore expected to circumvent the chemotherapeutic resistance of cancers characterized by transient or sustained EMT signatures. Thus, targeting critical orchestrators at the convergence of several EMT pathways, such as the transcription pathways NF-kappaB, AKT/mTOR axis, MAPK, beta-catenin, PKC and the AP-1/SMAD factors provide a realistic strategy to control EMT and the progression of human epithelial cancers. Several inhibitors targeting these signaling platforms are already tested in preclinical and clinical oncology. In addition, upstream EMT signaling pathways induced by receptor and nonreceptor tyrosine kinases (e.g. EGF-R, IGF-R, VEGF-R, integrins/FAK, Src) and G-protein-coupled receptors (GPCR) constitute practical options under preclinical research, clinical trials or are currently used in the clinic for cancer treatment: e.g. small molecule inhibitors (Iressa: targeting selectively the EGF-R; CP-751,871, AMG479, NVP-AEW541, BMS-536924, PQIP, AG1024: IGF-R; AZD2171, ZD6474: VEGF-R; AZD0530, BMS-354825, SKI606: Src; BIM-46174: GPCR; rapamycin, CCI-779, RAD-001: mTOR) and humanized function blocking antibodies (Herceptin: ErbB2; Avastin: VEGF-A; Erbitux: EGF-R; Abegrin: alphavbeta3 integrins). We can assume that silencing RNA and adenovirus-based gene transfer of therapeutic miR and dominant interferring expression vectors targeting EMT pathways and signaling elements will bring additional ways for the treatment of epithelial cancers. Identification of the factors that initiate, modulate and effectuate EMT signatures and their underlying upstream oncogenic pathways should provide the basis of more efficient strategies to fight cancer progression as well as genetic and epigenetic forms of drug resistance. This goal can be accomplished using global screening of human clinical tumors by EMT-associated cDNA, proteome, miRome, and tissue arrays.

Kinase switching in mesenchymal-like non-small cell lung cancer lines contributes to EGFR inhibitor resistance through pathway redundancy

NSCLC cells with a mesenchymal phenotype have shown a marked reduction in sensitivity to EGFR inhibitors, though the molecular rationale has remained obscure. Here we find that in mesenchymal-like tumor cells both tyrosine phosphorylation of EGFR, ErbB2, and ErbB3 signaling networks and expression of EGFR family ligands were decreased. While chronic activation of EGFR can promote an EMT-like transition, once having occurred EGFR family signaling was attenuated. We investigated the mechanisms by which mesenchymal-like cells bypass EGFR signaling and acquire alternative routes of proliferative and survival signaling. Mesenchymal-like NSCLC cells exhibit aberrant PDGFR and FGFR expression and autocrine signaling through these receptors can activate the MEK-ERK and PI3K pathways. Selective pharmacological inhibition of PDGFR or FGFR receptor tyrosine kinases reduced cell proliferation in mesenchymal-like but not epithelial NSCLC cell lines. A metastable, reversible EMT-like transition in the NSCLC line H358 was achieved by exogenous TGFbeta, which served as a model EMT system. The H358/TGFbeta cells showed many of the attributes of established mesenchymal-like NSCLC cells including a loss of cell-cell junctions, a loss of EGF-family ligand expression, a loss of ErbB3 expression, increased EGFR-independent Mek-Erk pathway activation and reduced sensitivity to EGFR inhibition. Notably an EMT-dependent acquisition of PDGFR, FGFR and TGFbeta receptors in H358/TGFbeta cells was also observed. In H358/TGFbeta cells both PDGFR and FGFR showed functional ligand stimulation of their intrinsic tyrosine kinase activities. The findings of kinase switching and acquired PDGFR and FGFR signaling suggest investigation of new inhibitor combinations to target NSCLC metastases.

Epithelial to mesenchymal transition derived from repeated exposure to gefitinib determines the sensitivity to EGFR inhibitors in A549, a non-small cell lung cancer cell line

Epithelial to mesenchymal transition (EMT) has been reported to be related with reduced sensitivity to EGFR tyrosine kinase (EGFR-TK) inhibitors. We performed this study to investigate whether this phenomenon would play a role in acquired resistance to gefitinib. In this study, we established a gefitinib-resistant subline (A549/GR), which was derived from the parental A549 cell line by chronic, repeated exposure to gefitinib. Compared with the A549 cells, the A549/GR cells were approximately 7.7-fold more resistant to gefitinib and they showed the cross-resistance against other EGFR-TK inhibitors, including CL-387,758, erlotinib and ZD6478. Phenotypic changes such as a spindle-cell shape and increased pseudopodia formation suggesting EMT was present in the A549/GR cells. These changes were accompanied by a decrease of E-cadherin and an increase of vimentin, which is a mesenchymal marker. In addition, the ability of invasion and migration was increased in the A549/GR cells. TGF-beta1 treatment for 72 h also induced EMT in the A549 cells and this transition led to resistance to gefitinib. Conversely, this was reversed through the removal of TGF-beta1. In conclusion, induction of EMT may contribute to the decreased efficacy of therapy in primary and acquired resistance to gefitinib.

Sensitivity to epidermal growth factor receptor inhibitor requires E-cadherin expression in urothelial carcinoma cells

PURPOSE

Epidermal growth factor receptor (EGFR) is an attractive target for the treatment of urothelial carcinoma, but a clinical response can be expected in only a small proportion of patients. The aim of this study was to define molecular markers of response to cetuximab therapy in a panel of urothelial carcinoma cell lines.

EXPERIMENTAL DESIGN

Eleven cell lines were investigated for antiproliferative response to cetuximab based on [(3)H]thymidine incorporation. A variety of markers, including EGFR expression, phosphorylation, and gene amplification, as well as the expression of other growth factor receptors, their ligands, and markers of epithelial-to-mesenchymal transition were investigated. Cohen's kappa statistic was used to estimate the agreement between response and expression of these markers. E-cadherin was silenced by small interfering RNA in two sensitive cell lines, and the effect on the response to cetuximab was measured.

RESULTS

We were able to identify a panel of relevant markers pertaining especially to alternate growth factor receptor expression and epithelial-to-mesenchymal transition that predicted response to cetuximab. The data suggested that expression of intact HER-4 (kappa, 1.00; P = 0.008), E-cadherin (kappa, 0.81; P = 0.015), and beta-catenin (kappa, 0.81; P = 0.015) and loss of expression of platelet-derived growth factor receptor beta (kappa, 0.57; P = 0.167) were associated with response to cetuximab therapy. Silencing E-cadherin in two sensitive cell lines reduced responsiveness to cetuximab in both (P < 0.001).

CONCLUSIONS

A panel of predictive markers for cetuximab response has been established in vitro and is currently being evaluated in a prospective clinical trial of neoadjuvant EGFR-targeted therapy. Most importantly, E-cadherin seems to play a central role in modulation of EGFR response in urothelial carcinoma.

Epithelial-to-mesenchymal transition and integrin-linked kinase mediate sensitivity to epidermal growth factor receptor inhibition in human hepatoma cells

Hepatocellular carcinoma (HCC) is associated with a poor prognosis due to late diagnoses and a lack of effective treatment options. Epidermal growth factor receptor (EGFR)-targeted therapies have been effective in other cancers. However, erlotinib and cetuximab have shown only modest efficacy in clinical trials of HCC. We examined epithelial-to-mesenchymal transition (EMT) as a determinant of sensitivity of HCC to EGFR inhibitors. A panel of 12 human hepatoma cell lines were classified as epithelial or mesenchymal based on their expression of E-cadherin and vimentin. The resulting classification correlated with a previous microarray analysis of human hepatoma cell lines whereby the mesenchymal cell lines were shown to have increased expression of genes involved in metastasis and invasion. Sensitivity to erlotinib, gefitinib, and cetuximab was assessed and the epithelial cell lines were found to be significantly more susceptible to all three agents. Analysis of the EGFR pathway showed that EMT status was independent of EGFR expression or downstream extracellular signal-regulated kinase activation and only the epithelial cell lines expressed ErbB3. Interestingly, mesenchymal cells resistant to EGFR inhibitors had increased AKT and signal transducer and activator of transcription-3 activation through elevated expression of integrin-linked kinase (ILK). Mesenchymal cell lines were therefore experimentally transformed with kinase-inactive ILK (KI-ILK) with a resulting decrease in ILK activity and activation of AKT. KI-ILK transformants showed increased sensitivity to EGFR inhibitors both in vitro and in an in vivo xenograft model. These data suggest that EMT predicts HCC sensitivity to EGFR-targeted therapies and that ILK is a novel target to overcome HCC resistance to EGFR inhibition.

Bypassing cellular EGF receptor dependence through epithelial-to-mesenchymal-like transitions

Over 90% of all cancers are carcinomas, malignancies derived from cells of epithelial origin. As carcinomas progress, these tumors may lose epithelial morphology and acquire mesenchymal characteristics which contribute to metastatic potential. An epithelial-to-mesenchymal transition (EMT) similar to the process critical for embryonic development is thought to be an important mechanism for promoting cancer invasion and metastasis. Epithelial-to-mesenchymal transitions have been induced in vitro by transient or unregulated activation of receptor tyrosine kinase signaling pathways, oncogene signaling and disruption of homotypic cell adhesion. These cellular models attempt to mimic the complexity of human carcinomas which respond to autocrine and paracrine signals from both the tumor and its microenvironment. Activation of the epidermal growth factor receptor (EGFR) has been implicated in the neoplastic transformation of solid tumors and overexpression of EGFR has been shown to correlate with poor survival. Notably, epithelial tumor cells have been shown to be significantly more sensitive to EGFR inhibitors than tumor cells which have undergone an EMT-like transition and acquired mesenchymal characteristics, including non-small cell lung (NSCLC), head and neck (HN), bladder, colorectal, pancreas and breast carcinomas. EGFR blockade has also been shown to inhibit cellular migration, suggesting a role for EGFR inhibitors in the control of metastasis. The interaction between EGFR and the multiple signaling nodes which regulate EMT suggest that the combination of an EGFR inhibitor and other molecular targeted agents may offer a novel approach to controlling metastasis.

Bladder cancer angiogenesis and metastasis--translation from murine model to clinical trial

In the majority of cases, death from bladder cancer results from metastatic disease. Understanding the closely linked mechanisms of invasion, metastasis and angiogenesis in bladder cancer has allowed us to develop new therapeutic strategies that harbor the promise of decisive improvements in patient survival. The essential link between cell based experiments and the translation of novel agents into human patients with bladder cancer is the animal model. With emphasis on the orthotopic xenograft model, this review outlines some key mechanisms relevant to angiogenesis and the development of metastasis in bladder cancer. We highlight especially pathways related to MMP-9, IL-8, VEGF and EGFR. Most commonly, expression patterns of these markers in patients have correlated to disease progression and patient survival, which has led to laboratory investigations of these markers and eventually novel targeted therapies that are translated back into the clinic by means of clinical trials. Although imperfect in their translatability into clinical efficacy, animal models remain a critical tool in bladder cancer research.

Targeted therapies in bladder cancer--an update

Intravesical immuno- and chemotherapy, surgery, and systemic chemotherapy are all critical elements in our management of patients with bladder cancer. Despite our advances with these modalities, we continue to seek newer treatment paradigms to improve patient outcome. Targeted therapy with novel agents directed at specific molecular pathways is a promising avenue to achieve such progress. This manuscript is based on a talk given at the Spring Session of the Society of Urologic Oncology in May 2006. Here, we focus on targeting growth factors and their receptors in bladder cancer. In particular, we summarize our own and others' ongoing basic science, translational, and clinical research in this field. Foremost in this line of study is the epidermal growth factor receptor (EGFR)-targeted therapy with small molecule inhibitors and monoclonal antibodies. We discuss the rationale for EGFR-directed therapy in bladder cancer. The clinical efficacy has been disappointing, and extensive work has been done to characterize molecular markers for predicting response. Some of our own preclinical findings related to platelet derived growth factor-beta (PDGFR-beta) and some background on ongoing clinical trials targeting human EGF receptor 2 (HER2) are summarized. Fibroblast growth factor 3 (FGFR3) offers promise as a potential target for therapy of both superficial and invasive disease. The role of FGFR3 mutations in bladder cancer is reviewed. Finally, we discuss the targeting of VEGF. Ultimately, it may be the use of multi-kinase inhibitors or the combination of different inhibitors to various targets that yields the best results.

Emerging drugs for targeted therapy of bladder cancer

Although chemotherapy has improved the treatment of metastatic bladder cancer, resection and continual surveillance remain the modalities used for treatment of organ-confined disease. More targeted therapies are needed to address the shortcomings of existing treatments. The authors recently became aware of the overexpression of tyrosine kinase growth factor receptors in a variety of malignancies. These receptor tyrosine kinases are coupled to several proliferative and antiapoptotic pathways that drive cancer cell growth. Targeted small-molecule therapies, including monoclonal antibodies and tyrosine kinase inhibitors, directed at these receptors have proven effective against a variety of tumor models. In this report, the authors summarize the results of several such studies and discuss the rationale and potential use of novel targeted drugs in the treatment of bladder cancer.