Nuclear EGFR as novel therapeutic target: insights into nuclear translocation and function

Ultrastructural Changes in Hippocampal Region CA1 Neurons After Exposure to Permissive Hypercapnia and/or Normobaric Hypoxia

Isolated exposure to intermittent hypoxia and permissive hypercapnia activates signaling mechanisms that induce ultrastructural changes in mitochondria and endoplasmic reticulum, accompanied by the development of maximal ischemic tolerance in neurons under the combined influence of these factors. However, there are a lack of data on the combined impact of these factors on the ultrastructure of neuronal organelles. The present study aims to comparatively assess the ultrastructural changes in neurons following isolated and combined exposure to hypoxia and hypercapnia, as well as to correlate these changes with the neuroprotective potential previously observed for these factors. Following a 15-session course of 30-min exposures to permissive hypercapnia (PCO2 ≈ 50 mmHg) and/or normobaric hypoxia (PO2 ≈ 150 mmHg), morphometric assessment was conducted to evaluate the extent of ultrastructural changes in hippocampal neurons (mitochondria, perinuclear space, and granular endoplasmic reticulum). It was found that in hippocampal neurons from the CA1 region, permissive hypercapnia resulted in increased mitochondrial size, expansion of membranous compartments of the granular endoplasmic reticulum, and perinuclear space. Normobaric hypoxia affected only mitochondrial size, while hypercapnic hypoxia specifically widened the perinuclear space. These ultrastructural changes objectively reflect varying degrees of the influence of hypoxia and hypercapnia on organelles responsible for energy metabolism, anti-apoptotic, and synthetic functions of neurons. This confirms the effect of potentiation of their neuroprotective effects under combined exposure and highlights the dominant role of the hypercapnic component in this mechanism.

Targeting Epidermal Growth Factor Receptor in Head and Neck Cancer

ABSTRACT

Head and neck squamous cell carcinomas are rising in incidence worldwide, and despite the advent of improved surgical and radiation techniques, a substantial proportion of patients have disease recurrence, where systemic therapies are the mainstay of management. Recent advances in systemic therapy include the development of epidermal growth factor receptor- and programmed death 1-targeting drugs, which have produced incremental improvements in disease outcomes. However, for most patients, responses to treatment remain elusive because of primary or acquired resistance. Novel drugs and rational drug combinations need to be tested based on biomarker identification and preclinical science that will ultimately advance outcomes for our patients. This review focuses on efforts untaken for epidermal growth factor receptor targeting in head and neck squamous cell carcinoma to date.

RNA-binding protein p54nrb/NONO potentiates nuclear EGFR-mediated tumorigenesis of triple-negative breast cancer

Nuclear-localized epidermal growth factor receptor (EGFR) highly correlates with the malignant progression and may be a promising therapeutic target for breast cancer. However, molecular mechanisms of nuclear EGFR in triple-negative breast cancer (TNBC) have not been fully elucidated. Here, we performed gene-annotation enrichment analysis for the interactors of nuclear EGFR and found that RNA-binding proteins (RBPs) were closely associated with nuclear EGFR. We further demonstrated p54^nrb/NONO, one of the RBPs, significantly interacted with nuclear EGFR. NONO was upregulated in 80 paired TNBC tissues and indicated a poor prognosis. Furthermore, NONO knockout significantly inhibited TNBC proliferation in vitro and in vivo. Mechanistically, NONO increased the stability of nuclear EGFR and recruited CREB binding protein (CBP) and its accompanying E1A binding protein p300, thereby enhancing the transcriptional activity of EGFR. In turn, EGFR positively regulated the affinity of NONO to mRNAs of nuclear EGFR downstream genes. Furthermore, the results indicated that the nuclear EGFR/NONO complex played a critical role in tumorigenesis and chemotherapy resistance. Taken together, our findings indicate that NONO enhances nuclear EGFR-mediated tumorigenesis and may be a potential therapeutic target for TNBC patients with nuclear EGFR expression.

The new fate of internalized membrane receptors: Internalized activation

Classically, the fate of internalized membrane receptors includes receptor degradation and receptor recycling. However, recent findings have begun to challenge these views. Much research demonstrated that many internalized membrane receptors can trigger distinct signal activation rather than being desensitized inside the cell. Here, we introduce the concept of "internalized activation" which not only represents a new mode of receptor activation, but also endows the new fate for receptor internalization (from death to life). The new activation mode and fate of membrane receptor are ubiquitous and have unique theoretical significance. We systematically put forward the features, process, and regulation of "internalized activation" and its significance in signal transduction and diseases. "Internalized activation" will provide a completely new understanding for the theory of receptor activation, internalization and novel drug targets for precision medicine.

Oxygen Deprivation Modulates EGFR and PD-L1 in Squamous Cell Carcinomas of the Head and Neck

Abundance and signaling of the epidermal growth factor receptor (EGFR) and programmed cell death protein ligand 1 (PD-L1) in head and neck squamous cell carcinoma (HNSCC) are not only genetically determined but are also subject to the traits of the tumor microenvironment, which has hitherto not been clarified completely. We investigated the impact of hypoxia on the EGFR system and on PD-L1 in six HPV negative HNSCC cell lines in vitro and in FaDu xenografts in vivo. Protein levels of EGFR, AKT, pAKT, ERK1/2, pERK1/2, CA IX, cleaved PARP (apoptosis), LC3B (autophagy), and PD-L1 were quantified by western blot after oxygen deprivation or CoCl₂, staurosporine, and erlotinib treatment. In FaDu xenograft tumors the expression of EGFR, CA IX andCD34 staining were analyzed. Reduced oxygen supply strongly downregulated EGFR protein levels and signaling in FaDu cells in vitro and in vivo, and a transient downregulation of EGFR signaling was found in three other HNSCC cell lines. PD-L1 was affected by oxygen deprivation in only one HNSCC cell line showing increased protein amounts. The results of this study indicate a significant impact of the traits of the tumor microenvironment on crucial molecular targets of cancer therapies with high clinical relevance for therapy resistance and response in HNSCC.

Combining PARP and DNA-PK Inhibitors With Irradiation Inhibits HPV-Negative Head and Neck Cancer Squamous Carcinoma Growth

Novel targeted agents to inhibit DNA repair pathways to sensitize tumors to irradiation (IR) are being investigated as an alternative to chemoradiation for locally advanced human papilloma virus negative (HPV-negative) head and neck squamous cell carcinoma (HNSCC). Two well-characterized targets that, when inhibited, exhibit potent IR sensitization are PARP1 and DNA-PKcs. However, their cooperation in sensitizing HPV-negative HNSCC to IR remains to be explored given that PARP1 and DNA-Pk_CS bind to unresected stalled DNA replication forks and cooperate to recruit XRCC1 to facilitate double-strand break repair. Here, we show that the combination of the DNA-PK inhibitor NU7441 and the PARP inhibitor olaparib significantly decrease proliferation (61–78%) compared to no reduction with either agent alone (p < 0.001) in both SCC1 and SCC6 cell lines. Adding IR to the combination further decreased cell proliferation (91–92%, p < 0.001) in SCC1 and SCC6. Similar results were observed using long-term colony formation assays [dose enhancement ratio (DER) 2.3–3.2 at 4Gy, p < 0.05]. Reduced cell survival was attributed to increased apoptosis and G2/M cell cycle arrest. Kinomic analysis using tyrosine (PTK) and serine/threonine (STK) arrays reveals that combination treatment results in the most potent inhibition of kinases involved in the CDK and ERK pathways compared to either agent alone. In vivo, a significant delay of tumor growth was observed in UM-SCC1 xenografts receiving IR with olaparib and/or NU7441, which was similar to the cisplatin-IR group. Both regimens were less toxic than cisplatin-IR as assessed by loss of mouse body weight. Taken together, these results demonstrate that the combination of NU7441 and olaparib with IR enhances HPV-negative HNSCC inhibition in both cell culture and in mice, suggesting a potential innovative combination for effectively treating patients with HPV-negative HNSCC.

COPI-Mediated Nuclear Translocation of EGFRvIII Promotes STAT3 Phosphorylation and PKM2 Nuclear Localization

As a non-ligand-dependent activation protein, EGFRvIII is the most common mutant of EGFR, and its existence or especially its nuclear translocation in tumors can exacerbate the malignancy. Compared with the nuclear translocation of EGFR, which has been studied extensively, the specific mechanism by which EGFRvIII undergoes nuclear translocation has not yet been reported. Here, we found that EGFRvIII eventually reached the nucleus with the involvement of the Golgi and endoplasmic reticulum (ER) in glioma cells. In this process, syntaxin-6 was responsible for the identification and transport of EGFRvIII on Golgi. We also demonstrated that COPI mediated the reverse transport of EGFRvIII from the Golgi to ER, which process was also important for EGFRvIII's nuclear accumulation. EGFRvIII's nuclear translocation can significantly promote STAT3 phosphorylation and PKM2 nuclear localization. Finally, we showed that EGFRvIII's nuclear translocation obviously induced the growth of gliomas in an intracranial xenotransplantation experiment. These data suggested that searching methods that inhibit EGFRvIII entry into the nucleus will be effective glioma treatments.

Cetuximab-radiotherapy combination in the management of locally advanced cutaneous squamous cell carcinoma

INTRODUCTION

We report the outcomes of using a combination of cetuximab with radiation therapy (Cetux-RT) to treat a selected group of patients with locally advanced (unresectable) cutaneous squamous cell carcinoma (LA-cSCC). This study presents two-year efficacy and safety data for 8 patients with LA-cSCC treated within a single institution.

METHODS

Between 2014 and 2017 a total of eight patients (seven males, one female) with LA-cSCC received curative intent treatment with Cetux-RT. All patients received an initial loading dose of cetuximab at 400 mg/m² seven days prior to radiotherapy, followed by weekly treatment with 250 mg/m² , continuing through the end of radiotherapy. Radiation doses were 6600 cGy/30 fr (n = 2), 6300 cGy/30fr (n = 2) and 5500 cGy/22 fr (n = 4).

RESULTS

The median age was 81 years (range, 55-87). The ECOG performance status of all patients was between 0 and 2. With a median duration of follow-up of 25 months (range 10-48 months), five patients remain in a complete response. After a partial response, another patient has relapsed and is receiving palliative chemotherapy, while two patients have died during the period of follow up (one of whom died following progression of disease, the other of an unrelated cause). Treatment in this group of patients was well tolerated, with most toxicities ≤ grade 2, and no toxicities of grade 4/5 reported.

CONCLUSIONS

Cetux-RT was well tolerated and provided durable disease control within this patient sample. Our data support the use of the Cetux-RT regimen for selected patients with inoperable LA-cSCC and adequate performance status.

Advances in targeting epidermal growth factor receptor signaling pathway in mammary cancer

Breast cancer is the most common malignancy among women worldwide. The role of epidermal growth factor receptor (EGFR) in many epithelial malignancies has been established, since it is dysregulated, overexpressed or mutated. Its overexpression has been associated with increased aggressiveness and metastatic potential in breast cancer. The well-established interplay between EGFR signaling pathway and estrogen receptors (ERs) as well as major extracellular matrix (ECM) mediators is crucial for regulating basic functional properties of breast cancer cells, including migration, proliferation, adhesion and invasion. EGFR activation leads to endocytosis of the receptor with implications in the regulation of downstream signaling effectors, the modulation of autophagy and cell survival. Therefore, EGFR is considered as a promising therapeutic target in breast cancer. Several anti-EGFR therapies (i.e. monoclonal antibodies and tyrosine kinase inhibitors) have been evaluated both in vitro and in vivo, making their way to clinical trials. However, the response rates of anti-EGFR therapies in the clinical trials is low mainly due to chemoresistance. Novel drug design, phytochemicals and microRNAs (miRNAs) are assessed as new therapeutic approaches against EGFR. The main goal of this review is to highlight the importance of targeting EGFR signaling pathway in terms of its crosstalk with ERs, the involvement of ECM effectors and epigenetics. Moreover, recent insights into the design of specialized delivery systems contributing in the development of novel diagnostic and therapeutic approaches in breast cancer are addressed.

Oxymatrine inhibits non-small cell lung cancer via suppression of EGFR signaling pathway

Epidermal growth factor receptor (EGFR) plays a crucial role in human non–small cell lung cancer (NSCLC) tumorigenesis. In this study, oxymatrine was identified as an EGFR signaling pathway inhibitor in NSCLC. Oxymatrine inhibited anchorage‐dependent and independent growth of NSCLC cell lines but had no cytotoxicity in normal lung cells. We found that exposure to oxymatrine not only suppressed the activity of wild‐type EGFR but also inhibited the activation of exon 19 deletion and L858R/T790M mutated EGFR. Flow cytometry analysis suggested that oxymatrine‐induced cell cycle G0/G1 arrest was dependent on EGFR‐Akt signaling. Exogenous overexpression of Myr‐Akt rescued cyclin D1 expression in HCC827 cells. Moreover, oxymatrine prominently suppressed tumor growth in a xenograft mouse model. Thus, oxymatrine appears to be a novel therapeutic agent for NSCLC treatment.

A Small Organic Molecule Blocks EGFR Transport into the Nucleus by the Nonclassical Pathway Resulting in Repression of Cancer Invasion

In addition to the traditional epidermal growth factor receptor (EGFR) signaling pathways, nuclear EGFR has been shown to control multiple cellular functions, including cell proliferation and invasion. It has been reported that EGFR is transported into the nucleus after forming a complex with KPNA/KPNB1 or KPNB1. Herein, it is shown that EGFR can interact with both KP and KPNA, but EGF-activated EGFR mostly binds with KPNB1 through the pull-down assay. Also, a small organic molecule (1), an effective binder of KPNB1, inhibits the interaction between EGFR and KPNB1 in the nonclassical transport pathway, but not KPNA. Furthermore, treatment of cancer cells with 1 noticeably blocks the nuclear entry of EGFR, which results in significant suppression of invasion by lung cancer H1299 cells. These findings show that 1 is an effective inhibitor of EGFR/KPNB1 interactions in vitro, it may be used in cellular studies as a tool to determine the role of nuclear EGFR, and it is a drug candidate.

Models of human adamantinomatous craniopharyngioma tissue: Steps toward an effective adjuvant treatment

Even though ACP is a benign tumor, treatment is challenging because of the tumor's eloquent location. Today, with the exception of surgical intervention and irradiation, further treatment options are limited. However, ongoing molecular research in this field provides insights into the pathways involved in ACP pathogenesis and reveal a plethora of druggable targets. In the next step, appropriate models are essential to identify the most suitable and effective substances for clinical practice. Primary cell cultures in low passages provide a proper and rapid tool for initial drug potency testing. The patient-derived xenograft (PDX) model accommodates ACP complexity in that it shows respect to the preserved architecture and similar histological appearance to human tumors and therefore provides the most appropriate means for analyzing pharmacological efficacy. Nevertheless, further research is needed to understand in more detail the biological background of ACP pathogenesis, which provides the identification of the best targets in the hierarchy of signaling cascades. ACP models are also important for the continuous testing of new targeting drugs, to establish precision medicine.

Localisation Microscopy of Breast Epithelial ErbB-2 Receptors and Gap Junctions: Trafficking after γ-Irradiation, Neuregulin-1β, and Trastuzumab Application

In cancer, vulnerable breast epithelium malignance tendency correlates with number and activation of ErbB receptor tyrosine kinases. In the presented work, we observe ErbB receptors activated by irradiation-induced DNA injury or neuregulin-1β application, or alternatively, attenuated by a therapeutic antibody using high resolution fluorescence localization microscopy. The gap junction turnover coinciding with ErbB receptor activation and co-transport is simultaneously recorded. DNA injury caused by 4 Gray of 6 MeV photon γ-irradiation or alternatively neuregulin-1β application mobilized ErbB receptors in a nucleograde fashion—a process attenuated by trastuzumab antibody application. This was accompanied by increased receptor density, indicating packing into transport units. Factors mobilizing ErbB receptors also mobilized plasma membrane resident gap junction channels. The time course of ErbB receptor activation and gap junction mobilization recapitulates the time course of non-homologous end-joining DNA repair. We explain our findings under terms of DNA injury-induced membrane receptor tyrosine kinase activation and retrograde trafficking. In addition, we interpret the phenomenon of retrograde co-trafficking of gap junction connexons stimulated by ErbB receptor activation.

Identification of the zinc finger 216 (ZNF216) in human carcinoma cells: a potential regulator of EGFR activity

Epidermal Growth Factor Receptor (EGFR), a member of the ErbB family of receptor tyrosine kinase (RTK) proteins, is aberrantly expressed or deregulated in tumors and plays pivotal roles in cancer onset and metastatic progression. ZNF216 gene has been identified as one of Immediate Early Genes (IEGs) induced by RTKs. Overexpression of ZNF216 protein sensitizes 293 cell line to TNF-α induced apoptosis. However, ZNF216 overexpression has been reported in medulloblastomas and metastatic nasopharyngeal carcinomas. Thus, the role of this protein is still not clearly understood. In this study, the inverse correlation between EGFR and ZNF216 expression was confirmed in various human cancer cell lines differently expressing EGFR. EGF treatment of NIH3T3 cells overexpressing both EGFR and ZNF216 (NIH3T3-EGFR/ZNF216), induced a long lasting activation of EGFR in the cytosolic fraction and an accumulation of phosphorylated EGFR (pEGFR) more in the nuclear than in the cytosolic fraction compared to NIH3T3-EGFR cells. Moreover, EGF was able to stimulate an increased expression of ZNF216 in the cytosolic compartment and its nuclear translocation in a time-dependent manner in NIH3T3-EGFR/ZNF216. A similar trend was observed in A431 cells endogenously expressing the EGFR and transfected with Znf216. The increased levels of pEGFR and ZNF216 in the nuclear fraction of NIH3T3-EGFR/ZNF216 cells were paralleled by increased levels of phospho-MAPK and phospho-Akt. Surprisingly, EGF treatment of NIH3T3-EGFR/ZNF216 cells induced a significant increase of apoptosis thus indicating that ZNF216 could sensitize cells to EGF-induced apoptosis and suggesting that it may be involved in the regulation and effects of EGFR signaling.

HER2-siRNA delivered by EGFR-specific single chain antibody inhibits NSCLC cell proliferation and tumor growth

Overexpression of human epidermal growth factor receptor type2 (HER2) is closely associated with aggressive progression and poor prognosis in non-small cell lung cancer (NSCLC). Here, we generated an EGFR-scFv-arginine nonamer peptide fusion protein (scFv-9R) as a cargo to deliver HER2 specific siRNA into HER2-positive NSCLC cells both in vitro and in vivo. HER2-siRNAs delivered by scFv-9R effeciently silenced HER2 expression in EGFR-positive NSCLC cells, and consequently resulted in G1 arrest and cell growth inhibition. Importantly, intravenous injection of scFv-9R/HER2-siRNA complex markedly suppressed growth of EGFR-positive NSCLC xenograft in nude mice, resulting from downregulated HER2 expression, reduced cell proliferation and enhanced cell apoptosis. Collectively, our study provides a novel therapeutic strategy for the treatment of EGFR-positive, HER2-overexpressed NSCLC.

A genetic view of laryngeal cancer heterogeneity

During the recent decades significant improvements in the understanding of laryngeal molecular biology allowed a better characterization of the tumor. However, despite increased molecular knowledge and clinical efforts, survival of patients with laryngeal cancer remains the same as 30 years ago. Although this result may not make major conclusions as preservation approaches were not broadly used until the time of database collection, it seems to be clear that there is still window for improvement. Although the cornerstone for laryngeal cancer eradication is to implement smoking cessation programs, survival progresses will be hopefully seen in the future. Introducing molecular biomarkers as predictive factors to determine which patients will benefit of preservation treatments may become one of the next steps to improve survival. Furthermore, the development of new therapeutic modalities joint to biomarkers to selectively apply such new therapy in these patients may help to define new modalities with improved survival. New inhibitors against Notch pathway, EGFR, VRK1 or DNA damage repair may become gold standard if we are able to identify patients that may benefit from them, either on survival or functional larynx preservation. It is the moment for an inflexion point on the way laryngeal cancer is clinically managed.

Cellular Pathways in Response to Ionizing Radiation and Their Targetability for Tumor Radiosensitization

During the last few decades, improvements in the planning and application of radiotherapy in combination with surgery and chemotherapy resulted in increased survival rates of tumor patients. However, the success of radiotherapy is impaired by two reasons: firstly, the radioresistance of tumor cells and, secondly, the radiation-induced damage of normal tissue cells located in the field of ionizing radiation. These limitations demand the development of drugs for either radiosensitization of tumor cells or radioprotection of normal tissue cells. In order to identify potential targets, a detailed understanding of the cellular pathways involved in radiation response is an absolute requirement. This review describes the most important pathways of radioresponse and several key target proteins for radiosensitization.

Potential crosstalk between cofilin-1 and EGFR pathways in cisplatin resistance of non-small-cell lung cancer

Current challenge in oncology is to establish the concept of personalized medicine in clinical practice. In this context, non-small-cell lung cancer (NSCLC) presents clinical, histological and molecular heterogeneity, being one of the most genomically diverse of all cancers. Recent advances added Epidermal Growth Factor Receptor (EGFR) as a predictive biomarker for patients with advanced NSCLC. In tumors with activating EGFR mutations, tyrosine kinase inhibitors (TKI) are indicated as first-line treatment, although restricted to a very small target population. In this context, cofilin-1 (a cytosolic protein involved with actin dynamics) has been widely studied as a biomarker of an aggressive phenotype in tumors, and overexpression of cofilin-1 is associated with cisplatin resistance and poor prognosis in NSCLC. Here, we gather information about the predictive potential of cofilin-1 and reviewed the crosstalk between cofilin-1/EGFR pathways. We aimed to highlight new perspectives of how these interactions might affect cisplatin resistance in NSCLC. We propose that cofilin-1 quantification in clinical samples in combination with presence/absence of EGFR mutation could be used to select patients that would benefit from TKI's treatment. This information is of paramount importance and could result in a possibility of guiding more effective treatments to NSCLC patients.

Opportunities and challenges of radiotherapy for treating cancer

The past 20 years have seen dramatic changes in the delivery of radiation therapy, but the impact of radiobiology on the clinic has been far less substantial. A major consideration in the use of radiotherapy has been on how best to exploit differences between the tumour and host tissue characteristics, which in the past has been achieved empirically by radiation-dose fractionation. New advances are uncovering some of the mechanistic processes that underlie this success story. In this Review, we focus on how these processes might be targeted to improve the outcome of radiotherapy at the individual patient level. This approach would seem a more productive avenue of treatment than simply trying to increase the radiation dose delivered to the tumour.

Nimotuzumab suppresses epithelial-mesenchymal transition and enhances apoptosis in low-dose UV-C treated salivary adenoid cystic carcinoma cell lines in vitro

Salivary adenoid cystic carcinoma (SACC), which is one of the most common malignant tumors of the salivary glands, is associated with a poor long-term outcome. There are currently few therapeutic options for patients with SACC. Recent studies have shown the potential of the application of ultraviolet-C (UV-C) irradiation for the treatment of human cancer. In the present study, we investigated the effects of UV-C in the SACC cell lines SACC-83 and SACC-LM. High-dose UV-C (200 J/m) induced apoptosis and inhibited colony formation significantly. However, low-dose UV-C (10 J/m), which had little effect on apoptosis and colony formation, increased the ability of migration in SACC cells accompanied by a decrease in E-cadherin and an increase in vimentin, suggesting the occurrence of epithelial-mesenchymal transition (EMT). Low-dose UV-C (10 J/m) also resulted in upregulation of the phosphorylated forms of epidermal growth factor receptor (EGFR) and Akt (p-EGFR and p-Akt, respectively). Pretreatment with Nimotuzumab, an anti-EGFR monoclonal antibody, reversed the EMT as well as upregulation of p-EGFR/p-Akt induced by UV-C. Moreover, Nimotuzumab enhanced UV-C induced apoptosis and inhibition of colony formation. Our results indicate that EMT exerts a protective effect against apoptosis induced by low-dose UV-C. Thus, the combined application of Nimotuzumab and low-dose UV-C in vitro has an advantageous antitumor effect in SACC compared with the application of UV-C alone.

A putative pH-dependent nuclear localization signal in the juxtamembrane region of c-Met

The C-terminal fragment of the c-Met receptor tyrosine kinase is present in the nuclei of some cells irrespective of ligand stimulation, but the responsible nuclear localization signal (NLS) has not been previously reported. Here, we report that two histidine residues separated by a 10-amino-acid spacer (H1068-H1079) located in the juxtamembrane region of c-Met function as a putative novel NLS. Deletion of these sequences significantly abolished the nuclear translocation of c-Met, as did substitution of the histidines with alanines. This substitution also decreased the association of c-Met fragment with importin β. The putative NLS of c-Met is unique in that it relies on histidines, whose positive charge changes depending on pH, rather than the lysines or arginines, commonly found in classical bipartite NLSs, suggesting the possible 'pH-dependency' of this NLS. Indeed, decreasing the cytosolic pH either with nigericin, an Na(+)/H(+) exchanger or pH 6.5 KRB buffer significantly increased the level of nuclear c-Met and the interaction of the c-Met fragment with importin β, indicating that low pH itself enhanced nuclear translocation. Consistent with this, nigericin treatment also increased the nuclear level of endogenous c-Met in HeLa cells. The putative aberrant bipartite NLS of c-Met seems to be the first example of what we call a 'pH-dependent' NLS.

Possible mechanisms and function of nuclear trafficking of the colony-stimulating factor-1 receptor

Receptor tyrosine kinases (RTK) have long being studied with respect to the "canonical" signaling. This includes ligand-induced activation of a receptor tyrosine kinase at the cell surface that leads to receptor dimerization, followed by its phosphorylation in the intracellular domain and activation. The activated receptor then recruits cytoplasmic signaling molecules including other kinases. Activation of the downstream signaling cascade frequently leads to changes in gene expression following nuclear translocation of downstream targets. However, RTK themselves may localize within the nucleus, as either full-length molecules or cleaved fragments, with or without their ligands. Significant differences in this mechanism have been reported depending on the individual RTK, cellular context or disease. Accumulating evidences indicate that the colony-stimulating factor-1 receptor (CSF-1R) may localize within the nucleus. To date, however, little is known about the mechanism of CSF-1R nuclear shuttling, as well as the functional role of nuclear CSF-1R.

Tomotherapy concomitant with cetuximab, followed by cetuximab as single-agent therapy for unresectable squamous cell carcinoma of the skin: a case report

BACKGROUND

Cutaneous squamous cell carcinoma (SCC) is the second most frequency of all skin tumors. Incidence of SCC has risen significantly due to an increased sun exposure and the number of immunodeficient patients. Cutaneous SCC is characterized by high Epidermal growth factor receptor (EGFR) expression with low frequency of RAS mutations. Generally, locoregional surgery is curative and systemic therapy is not indicated. We evaluated the activity and toxicity profile of tomotherapy concomitant with Cetuximab, followed by Cetuximab as single agent therapy in a patient affected by unresectable, locally advanced cutaneous SCC.

CASE PRESENTATION

At our institution, on March 2012 we treated a 45 years-old patient affected by locally advanced, unresectable G1 SCC of the lumbar region. At our first observation, the patient was asthenic, with severe pain and functional limitations. There was also a superinfection due to Pseudomonas Aeruginosa resistant to antibiotics, and a G3 anemia secondary to the bleeding lesion. ECOG Performance Status was 2. Tomotherapy has been performed concomitant with the Cetuximab (400 mg/m2, followed by weekly doses of 250 mg/m2) at the total dose of 60 Gy (2 Gy/fx), followed by Cetuximab monotherapy.The lesion reduced progressively until disappear even after the suspension of the treatment and the patient achieved complete response. Toxicity resulted in G1 cutaneous rash and G2 toxicity to the nails, appeared after 5 months of treatment, typical toxicity profile of the anti-EGFR therapies. After one month of therapy the Pseudomonas Aeruginosa superinfection totally disappeared. Quality of life resulted significantly improved with reduction until discontinuation of the anti-pain drugs, and progressive increase of the hemoglobin levels. At follow up of 15 months there was no evidence of active disease and the ECOG Performance Status was 0 (zero).

CONCLUSION

The treatment was effective and feasible. Considering these excellent results, further studies about concomitant tomotherapy with Cetuximab for advanced/inoperable SCC of the skin are needed.

Prognostic and predictive value of p-Akt, EGFR, and p-mTOR in early breast cancer

BACKGROUND AND PURPOSE

There are scarce data available on the prognostic/predictive value of p-Akt and p-mTOR protein expression in patients with high-risk early breast cancer.

PATIENTS AND METHODS

Formalin-fixed paraffin-embedded (FFPE) tumor tissue samples from 997 patients participating in two adjuvant phase III trials were assessed for EGFR, PTEN, p-Akt, p-mTOR protein expression, and PIK3CA mutational status. These markers were evaluated for associations with each other and with selected patient and tumor characteristics, immunohistochemical subtypes, disease-free survival (DFS), and overall survival (OS).

RESULTS

p-mTOR protein expression was negatively associated with EGFR and positively associated with PTEN, with p-Akt473, and with the presence of PIK3CA mutations. EGFR expression was positively associated with p-Akt473, p-Akt308, and PIK3CA wild-type tumors. Finally, p-Akt308 was positively associated with p-Akt473 expression. In univariate analysis, EGFR (p = 0.016) and the coexpression of EGFR and p-mTOR (p = 0.015) were associated with poor OS. Among patients with p-Akt308-negative or low-expressing tumors, those treated with hormonal therapy were associated with decreased risk for both relapse and death (p = 0.013 and p < 0.001, respectively). In the subgroup of patients with locoregional relapse, positive EGFR and mTOR protein expression was found to be associated with increased (p = 0.034) and decreased (p < 0.001) risk for earlier relapse, respectively. In multivariate analysis, low levels of p-Akt308 and the coexpression of EGFR and p-mTOR retained their prognostic value.

CONCLUSION

Low protein expression of p-Akt308 was associated with improved DFS and OS among patients treated with hormonal therapy following adjuvant chemotherapy. Coexpression of EGFR and p-mTOR was associated with worse OS.

Protein mislocalization: mechanisms, functions and clinical applications in cancer

The changes from normal cells to cancer cells are primarily regulated by genome instability, which foster hallmark functions of cancer through multiple mechanisms including protein mislocalization. Mislocalization of these proteins, including oncoproteins, tumor suppressors, and other cancer-related proteins, can interfere with normal cellular function and cooperatively drive tumor development and metastasis. This review describes the cancer-related effects of protein subcellular mislocalization, the related mislocalization mechanisms, and the potential application of this knowledge to cancer diagnosis, prognosis, and therapy.

Mutation analysis of genes in the EGFR pathway in Head and Neck cancer patients: implications for anti-EGFR treatment response

Background

Targeted therapy against the Epidermal Growth Factor Receptor (EGFR) is among the most promising molecular therapeutics for Head and Neck Squamous Cell Carcinoma (HNSCC). However, drug resistance limits the clinical efficacy of anti-EGFR monoclonal antibodies and no predictive biomarker has entered the clinic yet.

Methods

A retrospective clinical study was performed utilizing pathological specimens from 52 newly diagnosed HNSCC patients. These patients were screened for mutations in EGFR and KRAS. Tyrosine kinase mutations in EGFR and KRAS mutations were evaluated by high resolution melting analysis (HRMA), whereas EGFRvIII was determined using one-step real-time PCR. Finally, patient samples were screened for HPV-DNA by GP5+/6+ PCR. Survival analysis was performed using Kaplan-Meier analysis and significance was calculated using log-rank statistic.

Results

In our study population no EGFRvIII mutations were present. However, two silent mutations were found; T785T in exon 20 and R836R in exon 21 of the EGFR gene. Additionally, HRMA revealed an abnormal KRAS melting pattern in 7.0% of the samples. However, the KRAS StripAssay could confirm only one sample with a G12S mutation and none of these samples could be confirmed by direct sequencing. HPV DNA was present in 3/25 larynx and 9/27 oropharynx tumors.

Conclusion

The low rate of EGFR and KRAS mutations in this Belgian HNSCC population suggests that these genes will probably not play a major role in predicting response to anti-EGFR therapy in HNSCC. Hence, other predictive markers need to be discovered in order to optimize EGFR targeting therapy.

Chromatin-associated CSF-1R binds to the promoter of proliferation-related genes in breast cancer cells

The colony-stimulating factor-1 (CSF-1) and its receptor CSF-1R physiologically regulate the monocyte/macrophage system, trophoblast implantation and breast development. An abnormal CSF-1R expression has been documented in several human epithelial tumors, including breast carcinomas. We recently demonstrated that CSF-1/CSF-1R signaling drives proliferation of breast cancer cells via ‘classical' receptor tyrosine kinase signaling, including activation of the extracellular signal-regulated kinase 1/2. In this paper, we show that CSF-1R can also localize within the nucleus of breast cancer cells, either cell lines or tissue specimens, irrespectively of their intrinsic molecular subtype. We found that the majority of nuclear CSF-1R is located in the chromatin-bound subcellular compartment. Chromatin immunoprecipitation revealed that CSF-1R, once in the nucleus, binds to the promoters of the proliferation-related genes CCND1, c-JUN and c-MYC. CSF-1R also binds the promoter of its ligand CSF-1 and positively regulates CSF-1 expression. The existence of such a receptor/ligand regulatory loop is a novel aspect of CSF-1R signaling. Moreover, our results provided the first evidence of a novel localization site of CSF-1R in breast cancer cells, suggesting that CSF-1R could act as a transcriptional regulator on proliferation-related genes.

Mitigation of radiation-induced damage by targeting EGFR in noncancerous human epithelial cells

Methyl-2-cyano-3,12 dioxoolean-1,9 diene-28-oate (CDDO-Me) is an antioxidative, anti-inflammatory modulator, which activates the nuclear factor-erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway. While CDDO-Me has radioprotective activity through Nrf2 activation in vitro and in vivo, its ability to mitigate radiation-induced damage when provided after irradiation has not been studied. Here we investigated whether CDDO-Me mitigates ionizing radiation (IR)-induced DNA damage in immortalized normal human colonic epithelial cells (HCECs) and bronchial epithelial cells (HBECs). DNA damage and clonogenic survival were assessed after treatment with CDDO-Me postirradiation. We observed that treatment with CDDO-Me within 30 min after irradiation improved both DNA damage repair and clonogenic survival independently of Nrf2. CDDO-Me activates the epidermal growth factor receptor (EGFR) related DNA repair responses. In the presence of CDDO-Me, EGFR is phosphorylated and translocates into the nucleus where it interacts with DNA-PKcs. CDDO-Me-mediated mitigation activity can be abrogated through depletion of EGFR, ectopic overexpression of mutant EGFR or inhibition of DNA-PKcs. While post-treatment of CDDO-Me protected noncancerous HCECs and HBECs against IR, cancer cells (HCT116 and MCF7) were not protected by CDDO-Me. These results suggest that targeting EGFR using CDDO-Me is a promising radiation mitigator with potential utility for first responders to nuclear accidents.

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.

Interaction of EGFR with the tumour microenvironment: implications for radiation treatment

Treatment failure through radioresistance of tumours is associated with activation of the epidermal growth factor receptor (EGFR). Tumour cell proliferation, DNA-repair, hypoxia and metastases-formation are four mechanisms in which EGFR signalling has an important role. In clinical trials, a correlation has been demonstrated between high EGFR expression in tumours and poor outcome after radiotherapy. Inhibition of EGFR signalling pathways improves the effectiveness of radiotherapy of head and neck cancers by overcoming these main mechanisms of radioresistance. The fact that only a minority of the patients respond to EGFR inhibitors reflects the complexity of interactions between EGFR-dependent signalling pathways and the tumour microenvironment. Furthermore, many components of the microenvironment are potential targets for therapeutic interventions. Characterisation of the interaction of EGFR signalling and the tumour microenvironment is therefore necessary to improve the effectiveness of combined modality treatment with radiotherapy and targeted agents. Here, the current status of knowledge is reviewed and directions for future research are discussed.

DNA double-strand break repair as determinant of cellular radiosensitivity to killing and target in radiation therapy

Radiation therapy plays an important role in the management of a wide range of cancers. Besides innovations in the physical application of radiation dose, radiation therapy is likely to benefit from novel approaches exploiting differences in radiation response between normal and tumor cells. While ionizing radiation induces a variety of DNA lesions, including base damages and single-strand breaks, the DNA double-strand break (DSB) is widely considered as the lesion responsible not only for the aimed cell killing of tumor cells, but also for the general genomic instability that leads to the development of secondary cancers among normal cells. Homologous recombination repair (HRR), non-homologous end-joining (NHEJ), and alternative NHEJ, operating as a backup, are the major pathways utilized by cells for the processing of DSBs. Therefore, their function represents a major mechanism of radiation resistance in tumor cells. HRR is also required to overcome replication stress – a potent contributor to genomic instability that fuels cancer development. HRR and alternative NHEJ show strong cell-cycle dependency and are likely to benefit from radiation therapy mediated redistribution of tumor cells throughout the cell-cycle. Moreover, the synthetic lethality phenotype documented between HRR deficiency and PARP inhibition has opened new avenues for targeted therapies. These observations make HRR a particularly intriguing target for treatments aiming to improve the efficacy of radiation therapy. Here, we briefly describe the major pathways of DSB repair and review their possible contribution to cancer cell radioresistance. Finally, we discuss promising alternatives for targeting DSB repair to improve radiation therapy and cancer treatment.

Syntaxin 6-mediated Golgi translocation plays an important role in nuclear functions of EGFR through microtubule-dependent trafficking

Receptor tyrosine kinases (RTKs) are cell surface receptors that initiate signal cascades in response to ligand stimulation. Abnormal expression and dysregulated intracellular trafficking of RTKs have been shown to be involved in tumorigenesis. Recent evidence shows that these cell surface receptors translocate from cell surface to different cellular compartments, including the Golgi, mitochondria, endoplasmic reticulum (ER) and the nucleus, to regulate physiological and pathological functions. Although some trafficking mechanisms have been resolved, the mechanism of intracellular trafficking from cell surface to the Golgi is not yet completely understood. Here we report a mechanism of Golgi translocation of epidermal growth factor receptor (EGFR) in which EGF-induced EGFR travels to the Golgi via microtubule-dependent movement by interacting with dynein and fuses with the Golgi through syntaxin 6-mediated membrane fusion. We also demonstrate that the microtubule- and syntaxin 6-mediated Golgi translocation of EGFR is necessary for its consequent nuclear translocation and nuclear functions. Thus, together with previous studies, the microtubule- and syntaxin 6-mediated trafficking pathway from cell surface to the Golgi, ER and the nucleus defines a comprehensive trafficking route for EGFR to travel from cell surface to the Golgi and the nucleus.

Cis-9,trans-11-conjugated linoleic acid affects lipid raft composition and sensitizes human colorectal adenocarcinoma HT-29 cells to X-radiation

BACKGROUND

Investigations concerned the mechanism of HT-29 cells radiosensitization by cis-9,trans-11-conjugated linoleic acid (c9,t11-CLA), a natural component of human diet with proven antitumor activity.

METHODS

The cells were incubated for 24h with 70μM c9,t11-CLA and then X-irradiated. The following methods were used: gas chromatography (incorporation of the CLA isomer), flow cytometry (cell cycle), cloning (survival), Western blotting (protein distribution in membrane fractions), and pulse-field gel electrophoresis (rejoining of DNA double-strand breaks). In parallel, DNA-PK activity, γ-H2AX foci numbers and chromatid fragmentation were estimated. Gene expression was analysed by RT-PCR and chromosomal aberrations by the mFISH method. Nuclear accumulation of the EGF receptor (EGFR) was monitored by ELISA.

RESULTS AND CONCLUSIONS

C9,t11-CLA sensitized HT-29 cells to X-radiation. This effect was not due to changes in cell cycle progression or DNA-repair-related gene expression. Post-irradiation DSB rejoining was delayed, corresponding with the insufficient DNA-PK activation, although chromosomal aberration frequencies did not increase. Distributions of cholesterol and caveolin-1 in cellular membrane fractions changed. The nuclear EGFR translocation, necessary to increase the DNA-PK activity in response to oxidative stress, was blocked. We suppose that c9,t11-CLA modified the membrane structure, thus disturbing the intracellular EGFR transport and the EGFR-dependent pro-survival signalling, both functionally associated with lipid raft properties.

GENERAL SIGNIFICANCE

The results point to the importance of the cell membrane interactions with the nucleus after injury inflicted by X -rays. Compounds like c9,t11-CLA, that specifically alter membrane properties, could be used to develop new anticancer strategies.

Nuclear epidermal growth factor receptor and p16 expression in head and neck squamous cell carcinoma

OBJECTIVES/HYPOTHESIS

Epidermal growth factor receptor (EGFR) and p16 (a surrogate marker of human papillomavirus [HPV] infection) expression are strong prognostic factors in patients with head and neck squamous cell carcinoma (HNSCC).

STUDY DESIGN

We examined expression levels of total and nuclear EGFR as well as p16 status based on evidence that nuclear EGFR may have a role in DNA damage repair.

METHODS

An HPV-negative (SQ20B) and an HPV-positive (UMSCC47) HNSCC cell line were examined for EGFR and γH2AX expression. A tissue microarray containing 123 cores obtained from 101 HNSCC tumors was analyzed for EGFR expression by automated quantitative analysis and p16 expression by immunohistochemical staining, and these results were correlated with available clinical data.

RESULTS

SQ20B had higher EGFR expression than UMSCC47. Nuclear localization of EGFR on activation with transforming growth factor-α was observed in SQ20B, but not in UMSCC47. SQ20B also had increased γH2AX foci compared to UMSCC47, suggesting that SQ20B has more DNA damage compared to UMSCC47. Total and nuclear EGFR was reliably obtained from 80 of 101 patients. p16 levels were determined in 87 of 101 patients. p16 levels were strongly associated with the oropharyngeal subsite and poorly differentiated histology. Expression of total and nuclear EGFR was higher in p16-negative tumors compared to p16-positive tumors (Wilcoxon rank test, P = .038 and P = .014, respectively).

CONCLUSIONS

Further studies are required to determine a mechanistic link between these two prognostic factors and the significance of EGFR localization to nucleus in DNA damage repair pathway activation.

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.

Nuclear functions and subcellular trafficking mechanisms of the epidermal growth factor receptor family

Accumulating evidence suggests that various diseases, including many types of cancer, result from alteration of subcellular protein localization and compartmentalization. Therefore, it is worthwhile to expand our knowledge in subcellular trafficking of proteins, such as epidermal growth factor receptor (EGFR) and ErbB-2 of the receptor tyrosine kinases, which are highly expressed and activated in human malignancies and frequently correlated with poor prognosis. The well-characterized trafficking of cell surface EGFR is routed, via endocytosis and endosomal sorting, to either the lysosomes for degradation or back to the plasma membrane for recycling. A novel nuclear mode of EGFR signaling pathway has been gradually deciphered in which EGFR is shuttled from the cell surface to the nucleus after endocytosis, and there, it acts as a transcriptional regulator, transmits signals, and is involved in multiple biological functions, including cell proliferation, tumor progression, DNA repair and replication, and chemo- and radio-resistance. Internalized EGFR can also be transported from the cell surface to several intracellular compartments, such as the Golgi apparatus, the endoplasmic reticulum, and the mitochondria, in addition to the nucleus. In this review, we will summarize the functions of nuclear EGFR family and the potential pathways by which EGFR is trafficked from the cell surface to a variety of cellular organelles. A better understanding of the molecular mechanism of EGFR trafficking will shed light on both the receptor biology and potential therapeutic targets of anti-EGFR therapies for clinical application.

Targeting DNA damage and repair: embracing the pharmacological era for successful cancer therapy

DNA is under constant assault from genotoxic agents which creates different kinds of DNA damage. The precise replication of the genome and the continuous surveillance of its integrity are critical for survival and the avoidance of carcinogenesis. Cells have evolved an arsenal of repair pathways and cell cycle checkpoints to detect and repair DNA damage. When repair fails, typically cell cycle progression is halted and apoptosis is initiated. Here, we review the different sources and types of DNA damage including DNA replication stress and oxidative stress, the repair pathways that cells utilize to repair damaged DNA, and discuss their biological significance, especially with reference to cancer induction and cancer therapy. We also describe the main methodologies currently used for the detection of DNA damage with their strengths and limitations. We conclude with an outline as to how this information can be used to identify novel pharmacological targets for DNA repair pathways or enhancers of DNA damage to develop improved treatment strategies that will benefit cancer patients.

Molecular markers for cancer prognosis and treatment: have we struck gold?

The last decade has witnessed an emerging role for molecular or biochemical markers indicating a specific cellular mechanism or tissue function, often called 'biomarkers'. Biomarkers such as altered DNA, proteins and inflammatory cytokines are critical in cancer research and strategizing treatment in the clinic. In this review we look at the application of biological indicators to cancer research and highlight their roles in cancer detection and treatment. With technological advances in gene expression, genomic and proteomic analysis, biomarker discovery is expanding fast. We focus on some of the predominantly used markers in different types of malignancies, their advantages, and their limitations. Finally we conclude by looking at the future of biomarkers, their utility in the tumorigenic studies, and the progress towards personalized treatment strategies.