Epithelial-mesenchymal-transition induced by EGFR activation interferes with cell migration and response to irradiation and cetuximab in head and neck cancer cells

Current role of EGF receptor monoclonal antibodies and tyrosine kinase inhibitors in the management of head and neck squamous cell carcinoma

New agents and treatment strategies that can be safely and effectively integrated into current treatment paradigms for head and neck squamous cell carcinoma (HNSCC) are urgently needed. To date, the anti-EGF receptor (EGFR) monoclonal antibody, cetuximab, is the first and only molecularly targeted therapy to demonstrate a survival benefit for patients with recurrent or metastatic disease. Other anti-EGFR-targeted therapies, including monoclonal antibodies (e.g., panitumumab and zalutumumab) and reversible and irreversible ErbB family tyrosine kinase inhibitors (e.g., lapatinib, afatinib and dacomitinib) are being actively investigated in Phase II and Phase III clinical trials. In addition, validated biomarkers are needed to predict clinical benefit and resistance to anti-EGFR therapy in HNSCC. This review will compare and contrast the mechanisms of action of anti-EGFR monoclonal antibodies and tyrosine kinase inhibitors and also discuss their role in the management of HNSCC and the potential impact of human papillomavirus status in the development of these targeted agents.

Epithelial to mesenchymal transition in head and neck squamous cell carcinoma

Epithelial to mesenchymal transition (EMT) is a dynamic cellular process that is essential for the development of metastatic disease. During EMT, a tumor cell with epithelial characteristics transitions to a tumor cell with mesenchymal characteristics through modulation of cell polarity and adhesion. Two hallmark EMT proteins, E-Cadherin and Vimentin, are tightly controlled during EMT through multiple signal transduction pathways. Epidermal growth factor (EGF) and transforming growth factorβ (TGFβ) promote EMT by regulating a distinct set of transcription factors, including Snail and Twist. Snail, Twist, and Slug are integral to the induction of EMT through direct regulation of genes involved in cellular adhesion, migration, and invasion. This review highlights the current literature on EMT in HNSCC. Understanding the role of EMT will provide insight to the pathogenesis of disease progression and may lead to the development of novel anti-cancer therapeutics for metastatic HNSCC.

Reversion of the ErbB malignant phenotype and the DNA damage response

The ErbB or HER family is a group of membrane bound tyrosine kinase receptors that initiate signal transduction cascades, which are critical to a wide range of biological processes. When over-expressed or mutated, members of this kinase family form homomeric or heteromeric kinase assemblies that are involved in certain human malignancies. Targeted therapy evolved from studies showing that monoclonal antibodies to the ectodomain of ErbB2/neu would reverse the malignant phenotype. Unfortunately, tumors develop resistance to targeted therapies even when coupled with genotoxic insults such as radiation. Radiation treatment predominantly induces double strand DNA breaks, which, if not repaired, are potentially lethal to the cell. Some tumors are resistant to radiation treatment because they effectively repair double strand breaks. We and others have shown that even in the presence of ionizing radiation, active ErbB kinase signaling apparently enhances the repair process, such that transformed cells resist genotoxic signal induced cell death. We review here the current understanding of ErbB signaling and DNA double strand break repair. Some studies have identified a mechanism by which DNA damage is coordinated to assemblies of proteins that associate with SUN domain containing proteins. These assemblies represent a new target for therapy of resistant tumor cells.

A CD44high/EGFRlow subpopulation within head and neck cancer cell lines shows an epithelial-mesenchymal transition phenotype and resistance to treatment

Mortality in head and neck squamous cell carcinoma (HNSCC) is high due to emergence of therapy resistance which results in local and regional recurrences that may have their origin in resistant cancer stem cells (CSCs) or cells with an epithelial-mesenchymal transition (EMT) phenotype. In the present study, we investigate the possibility of using the cell surface expression of CD44 and epidermal growth factor receptor (EGFR), both of which have been used as stem cell markers, to identify subpopulations within HNSCC cell lines that differ with respect to phenotype and treatment sensitivity. Three subpopulations, consisting of CD44^high/EGFR^low, CD44^high/EGFR^high and CD44^low cells, respectively, were collected by fluorescence-activated cell sorting. The CD44^high/EGFR^low population showed a spindle-shaped EMT-like morphology, while the CD44^low population was dominated by cobblestone-shaped cells. The CD44^high/EGFR^low population was enriched with cells in G0/G1 and showed a relatively low proliferation rate and a high plating efficiency. Using a real time PCR array, 27 genes, of which 14 were related to an EMT phenotype and two with stemness, were found to be differentially expressed in CD44^high/EGFR^low cells in comparison to CD44^low cells. Moreover, CD44^high/EGFR^low cells showed a low sensitivity to radiation, cisplatin, cetuximab and gefitinib, and a high sensitivity to dasatinib relative to its CD44^high/EGFR^high and CD44^low counterparts. In conclusion, our results show that the combination of CD44 (high) and EGFR (low) cell surface expression can be used to identify a treatment resistant subpopulation with an EMT phenotype in HNSCC cell lines.

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 ubiquitin-proteasome system and signal transduction pathways regulating Epithelial Mesenchymal transition of cancer

Epithelial to Mesenchymal transition (EMT) in cancer, a process permitting cancer cells to become mobile and metastatic, has a signaling hardwire forged from development. Multiple signaling pathways that regulate carcinogenesis enabling characteristics in neoplastic cells such as proliferation, resistance to apoptosis and angiogenesis are also the main players in EMT. These pathways, as almost all cellular processes, are in their turn regulated by ubiquitination and the Ubiquitin-Proteasome System (UPS). Ubiquitination is the covalent link of target proteins with the small protein ubiquitin and serves as a signal to target protein degradation by the proteasome or to other outcomes such as endocytosis, degradation by the lysosome or specification of cellular localization. This paper reviews signal transduction pathways regulating EMT and being regulated by ubiquitination.

Impaired degradation followed by enhanced recycling of epidermal growth factor receptor caused by hypo-phosphorylation of tyrosine 1045 in RBE cells

Background

Since cholangiocarcinoma has a poor prognosis, several epidermal growth factor receptor (EGFR)-targeted therapies with antibody or small molecule inhibitor treatment have been proposed. However, their effect remains limited. The present study sought to understand the molecular genetic characteristics of cholangiocarcinoma related to EGFR, with emphasis on its degradation and recycling.

Methods

We evaluated EGFR expression and colocalization by immunoblotting and immunofluorescence, cell surface EGFR expression by fluorescence-activated cell sorting (FACS), and EGFR ubiquitination and protein binding by immunoprecipitation in the human cholangiocarcinoma RBE and immortalized cholangiocyte MMNK-1 cell lines. Monensin treatment and Rab11a depletion by siRNA were adopted for inhibition of EGFR recycling.

Results

Upon stimulation with EGF, ligand-induced EGFR degradation was impaired and the expression of phospho-tyrosine 1068 and phospho-p44/42 MAPK was sustained in RBE cells as compared with MMNK-1 cells. In RBE cells, the process of EGFR sorting for lysosomal degradation was blocked at the early endosome stage, and non-degradated EGFR was recycled to the cell surface. A disrupted association between EGFR and the E3 ubiquitin ligase c-Cbl, as well as hypo-phosphorylation of EGFR at tyrosine 1045 (Tyr1045), were also observed in RBE cells.

Conclusion

In RBE cells, up-regulation of EGFR Tyr1045 phosphorylation is a potentially useful molecular alteration in EGFR-targeted therapy. The combination of molecular-targeted therapy determined by the characteristics of individual EGFR phosphorylation events and EGFR recycling inhibition show promise in future treatments of cholangiocarcinoma.

Monitoring of circulating tumor cells and their expression of EGFR/phospho-EGFR during combined radiotherapy regimens in locally advanced squamous cell carcinoma of the head and neck

PURPOSE

The numbers of circulating tumor cells (CTCs) and their expression/activation of epidermal growth factor receptor (EGFR) during the course of combined chemo- or bioradiotherapy regimens as potential biomarkers of treatment efficacy in squamous cell carcinoma of the head and neck (SCCHN) were determined.

METHODS AND MATERIALS

Peripheral blood samples from SCCHN patients with locally advanced stage IVA/B disease who were treated with concurrent radiochemotherapy or induction chemotherapy followed by bioradiation with cetuximab were included in this study. Using flow cytometry, the absolute number of CTCs per defined blood volume as well as their expression of EGFR and its phosphorylated form (pEGFR) during the course of treatment were assessed.

RESULTS

Before treatment, we detected ≥1 CTC per 3.75 mL blood in 9 of 31 patients (29%). Basal expression of EGFR was detected in 100% and pEGFR in 55% of the CTC+ cases. The frequency of CTC detection was not influenced by induction chemotherapy. However, the number of CTC+ samples significantly increased after radiotherapy. This radiation-induced increase in CTC numbers was less pronounced when radiotherapy was combined with cetuximab compared to its combination with cisplatin/5-fluorouracil. The former treatment regimen was also more effective in reducing pEGFR expression in CTCs.

CONCLUSIONS

Definitive radiotherapy regimens of locally advanced SCCHN can increase the number of CTCs and might thus contribute to a systemic spread of tumor cells. Further studies are needed to evaluate the predictive value of the radiation-induced increase in CTC numbers and the persistent activation of the EGFR signalling pathway in individual CTC+ cases.

A simple multicolor flow cytometry protocol for detection and molecular characterization of circulating tumor cells in epithelial cancers

Circulating tumor cells (CTCs) might not only serve as prognostic marker but could also be useful for monitoring treatment efficacy. A multicolor flow cytometry protocol for their detection and molecular characterization in peripheral blood was developed which consisted of erythrocyte lysis followed by staining of cells with fluorochrome-labeled antibodies against CD45 and the epithelial markers EpCam and cytokeratin 7/8. For reducing the number of events acquired by flow cytometry, an electronic threshold for the fluorescent signals from the epithelial markers was applied. After establishment of the protocol by using spiking experiments, its suitability to determine the absolute number of CTCs as well as their expression of epidermal growth factor receptor (EGFR) and its phosphorylated form (phospho-EGFR) in blood samples from patients with squamous cell carcinoma of the head and neck (SCCHN) was validated. Spiking experiments demonstrated an excellent recovery (mean 85%) and a linear performance (R(2) = 0.98) of the protocol. Sensitivity and specificity were comparable to our former protocol using immunomagnetic CTC pre-enrichment. The analysis of 33 SCCHN patient samples revealed the presence of CTCs in 33.3% of cases with a mean ± SD of 1.5 ± 0.5 CTCs per 3.75 ml blood. EGFR was expressed in 100% and phospho-EGFR in 36.4% of the CTC+ cases. We have established a simple and sensitive multicolor flow cytometry protocol for detection of CTCs in patients with epithelial cancers including SCCHN which will allow their detailed molecular characterization.

Radiochemotherapy induces a favourable tumour infiltrating inflammatory cell profile in head and neck cancer

Head and neck squamous cell cancers (HNSSC) generate an immune-suppressive micro-environment by a specific pattern of tumour infiltrating inflammatory cells. The aim of our study was to evaluate the impact of radiochemotherapy on the numbers and composition of inflammatory cells and its influence on outcome. Fifty-eight patients suffering from oral cavity cancer were studied, whose therapy consisted of concurrent radiochemotherapy followed by surgery. Numbers and ratios of tumour infiltrating inflammatory cells were compared prior to and after radiochemotherapy. Intraepithelial and stromal location of tumour infiltrating inflammatory cells was analysed separately. Infiltration of CD3(+), CD4(+), CD25(+), FoxP3(+), CD8(+), Granzyme B(+), CD20(+) and CD68(+) cells predominated in the peritumoural stromal compartment, whereas CD1a(+) dendritic cells were found more frequently in the intraepithelial compartment. Neoadjuvant treatment was associated with a general decrease of tumour infiltrating inflammatory cells in both compartments. The CD8(+) and Granzyme B(+) cytotoxic cells decreased only slightly after RCT. In contrast, the decrease of FoxP3(+) regulatory T cells was more pronounced and the cytotoxic T-cell/FoxP3(+) ratio increased 2- to 3-fold in both compartments, respectively. Patients with high cytotoxic cell numbers, high dendritic cell numbers and a high ratio of cytotoxic cells to regulatory T cells had a better disease free survival. Concurrent radiochemotherapy of oral squamous cell carcinoma was shown to drive the composition of inflammatory cells in a direction which is supposed to be prognostically favourable.