Nuclear Epidermal Growth Factor Receptor Research Articles

Nuclear epidermal growth factor receptor interacts with transcriptional intermediary factor 2 to activate cyclin D1 gene expression triggered by the oncoprotein latent membrane protein 1

The epidermal growth factor receptor (EGFR), a ubiquitously expressed receptor tyrosine kinase, is an important factor in carcinogenesis. Transcriptional intermediary factor 2 (TIF2), a member of the p160 nuclear receptor co-activator gene family, is linked to the proliferation of cancer cells. However, the direct interplay between the EGFR and the nuclear receptors remains unclear. Our previous study demonstrated that nuclear EGFR could directly bind to the cyclin D1 promoter under the regulation of the oncoprotein latent membrane protein 1 (LMP1), but it also indicated that other factors are involved in the activation of target genes. In this study, we found that LMP1 upregulated the expression of TIF2 and promoted the interaction of EGFR with TIF2 in nasopharyngeal carcinoma. Furthermore, we demonstrated that the intact complex was linked with cyclin D1 promoter activity in an LMP1-dependent manner. The physiological functions of the intact complex were associated with cell proliferation and cell cycle progression. These findings suggest that TIF2 is a novel binding partner for nuclear EGFR and is involved in regulating its target gene expression.

The prognostic value of expression of HIF1α, EGFR and VEGF-A, in localized prostate cancer for intermediate- and high-risk patients treated with radiation therapy with or without androgen deprivation therapy

PurposeAndrogens stimulate the production of hypoxia-inducible factor (HIF1α) and ultimately vascular endothelial growth factor (VEGF-A). Additionally, epithelial growth factor (EGF) mediates HIF1α production. Carbonic anhydrase IX (CAIX) expression is associated with tumor cell hypoxia in a variety of malignancies. This study assesses the prognostic relation between HIF1α, VEGF-A, EGF Receptor and CAIX expression by immunochemistry in diagnostic samples of patients with intermediate- and high-risk localized prostate cancer treated with radiation therapy, with or without androgen deprivation therapy (ADT).Materials and methodsBetween 1994 and 2004, 103 prostate cancer patients (mean age, 68.7 ± 6.2), with prostate cancer (mean PSA, 13.3 ± 3.7), were treated with radiation therapy (RT, median dose, 74 Gy). Fifty seven (55.3%) patients received ADT (median duration, 6 months; range, 0 – 24). Median follow-up was 97.6 months (range, 5.9 – 206.8).ResultsHigher EGFR expression was significantly (p = 0.04) correlated with higher Gleason scores. On univariate analysis, HIF1α nuclear expression was a significant (p = 0.02) prognostic factor for biological progression-free survival (bPFS). A trend towards significance (p = 0.05) was observed with EGFR expression and bPFS. On multivariate analysis, low HIF1α nuclear (p = 0.01) and high EGFR (p = 0.04) expression remained significant adverse prognostic factors.ConclusionsOur study suggests that high nuclear expression of HIF1α and low EGFR expression in diagnostic biopsies of prostate cancer patients treated with RT ± ADT is associated with a good prognosis.

Knockdown of aberrantly expressed nuclear localized decorin attenuates tumour angiogenesis related mediators in oral cancer progression model in vitro

BackgroundOral cancer accounts for roughly 3% of cancer cases in the world with about 350,000 newly reported cases annually and a 5-year survival rate of only 50%. Majority of oral cancers are squamous cell carcinomas that originate in the oral mucosal epithelial linings. We have previously shown that in human malignant squamous cells carcinoma (SCC-25) as well as in dysplastic oral keratinocytes (DOK), a small leucine-rich multifunctional proteoglycan decorin is aberrantly expressed and localized in the nucleus where it interacts with nuclear epidermal growth factor receptor (EGFR). Post-transcriptional silencing of nuclear decorin significantly reduced IL-8 and IL8-dependent migration and invasion in these dysplastic and malignant oral epithelia. The objective of this study was to further examine the effects of nuclear decorin silencing on angiogenesis and angiogenesis related mediators in this oral cancer progression cell line model.MethodsWe have used multiplex PCR, western blotting, and in vitro endothelial tube formation assay to study angiogenesis and related pathways in nuclear decorin silenced (stable knockdown) DOK and SCC-25 cells.ResultsNuclear decorin knockdown resulted in significant down regulation of IL-8 expression, however IL-10, and TGF-β expression was not affected in either DOK or SCC25 cells as measured by multiplex RT PCR. IL-8 receptor CXCR 1 and 2 expression was slightly lower in nuclear decorin silenced cells indicating a contributing mechanism in previously shown reduced IL-8 mediated migration and invasion phenotype in these cells. IL-8 is known to induce Matrix metalloproteinase 9 (MMP9) which not only plays a role in tumour migration and invasion but also induces angiogenic switch. We found MMP9 to be significantly reduced in nuclear decorin silenced dysplastic and malignant oral epithelia. Other potent angiogenic mediators, VEGF189 and ANG-1 were either significantly reduced or completely abrogated in these cells. Angiogenesis as measured by endothelial tube-like formations of HUVEC cells was reduced by almost 50 percent when HUVECs were incubated in the presence of conditioned medium form nuclear decorin silenced dysplastic and malignant cell lines as compared to respective controls.ConclusionsTogether these results indicate that aberrantly expressed nuclear localized decorin strongly influences angiogenic potential of dysplastic and malignant oral epithelial cells.

Yes and Lyn play a role in nuclear translocation of the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) is a central regulator of tumor progression in human cancers. Cetuximab is an anti-EGFR antibody that has been approved for use in oncology. Previously we investigated mechanisms of resistance to cetuximab using a model derived from the non-small cell lung cancer line NCI-H226. We demonstrated that cetuximab-resistant clones (CtxR) had increased nuclear localization of the EGFR. This process was mediated by Src family kinases (SFK), and nuclear EGFR played a role in resistance to cetuximab. To better understand SFK mediated nuclear translocation of EGFR, we investigated which SFK member(s) controlled this process as well as the EGFR tyrosine residues that are involved. Analyses of mRNA and protein expression indicated up-regulation of the SFK members Yes and Lyn in all CtxR clones. Further, immunoprecipitation analysis revealed that EGFR interacts with Yes and Lyn in CtxR clones, but not in cetuximab-sensitive (CtxS) parental cells. Using RNAi interference, we found that knockdown of either Yes or Lyn led to loss of EGFR translocation to the nucleus. Conversely, overexpression of Yes or Lyn in low nuclear EGFR expressing CtxS parental cells led to increased nuclear EGFR. Chromatin immunoprecipitation (ChIP) assays confirmed nuclear EGFR complexes associated with the promoter of the known EGFR target genes B-Myb and iNOS. Further, all CtxR clones exhibited up-regulation of B-Myb and iNOS at the mRNA and protein levels. siRNAs directed at Yes or Lyn led to decreased binding of EGFR complexes to the B-Myb and iNOS promoters based on ChIP analyses. SFKs have been shown to phosphorylate EGFR on tyrosines 845 and 1101 (Y845 and Y1101) and mutation of Y1101, but not Y845, impaired nuclear entry of the EGFR. Taken together, our findings demonstrate that Yes and Lyn phosphorylate EGFR at Y1101 which influences EGFR nuclear translocation in this model of cetuximab resistance.

Nuclear Translocation of β-catenin is Essential for Glioma Cell Survival

Identification of molecular pathways that are essential for cancer cell survival is vital for understanding the underlying biology, as well as to design effective cancer therapeutics. β-catenin, a multifunctional oncogenic protein, participates in cell development. Its multifaceted functions primarily lie to the subcellular distribution. The present study demonstrated that β-catenin accumulated in the nucleus to a greater extent in high-grade gliomas compared with low-grade gliomas. In addition, nuclear localization correlated with a worse prognosis for patients, as determined by immunohistochemical analysis of 74 glioma samples. Nuclear expression of β-catenin was down-regulated in LN229 and U87 glioma cells by a small molecule inhibitor of β-catenin/TCF4 signaling, demonstrating strongly inhibited β-catenin/TCF4 transcriptional activity and STAT3 luciferase activity, as well as decreased mRNA and protein levels of nuclear β-catenin, TCF4, EGFR, AKT1, AKT2 and STAT3. Furthermore, repressed nuclear translocation of β-catenin resulted in inhibition of proliferation and invasiveness, and also induced apoptosis of glioma cells. Similar results were also observed in vivo; intratumoral injection of such small molecule inhibitor downregulated expression of nuclear β-catenin, TCF4, and components of the EGFR pathway, and also delayed tumor growth in nude mice harboring subcutaneous U87 xenografts. Results from the present study provided evidence that nuclear accumulation of β-catenin participated in malignant progression of gliomas and implicated poor prognosis, highlighting it as a potential therapeutic target for gliomas.

EGFR and myosin II inhibitors cooperate to suppress EGFR-T790M-mutant NSCLC cells

An acquired mutation (T790M) in the epidermal growth factor receptor (EGFR) accounts for half of all relapses in non-small cell lung cancer (NSCLC) patients who initially respond to EGFR kinase inhibitors. In this study, we demonstrated for the first time that EGFR-T790M interacts with the cytoskeletal components, myosin heavy chain 9 (MYH9) and β-actin, in the nucleus of H1975 cells carrying the T790M-mutant EGFR. The interactions of EGFR with MYH9 and β-actin were reduced in the presence of blebbistatin, a specific inhibitor for the MYH9-β-actin interaction, suggesting that the EGFR interaction with MYH9 and β-actin is affected by the integrity of the cytoskeleton. These physical interactions among MYH9, β-actin, and EGFR were also impaired by CL-387,785, a kinase inhibitor for EGFR-T790M. Furthermore, CL-387,785 and blebbistatin interacted in a synergistic fashion to suppress cell proliferation and induce apoptosis in H1975 cells. The combination of CL-387,785 and blebbistatin enhanced the down-regulation of cyclooxygenase-2 (COX-2), a transcriptional target of nuclear EGFR. Overall, our findings demonstrate that disrupting EGFR interactions with the cytoskeletal components enhanced the anti-cancer effects of CL-387,785 against H1975 cells, suggesting a novel therapeutic approach for NSCLC cells that express the drug-resistant EGFR-T790M.

Association of Nuclear YB-1 Localization With Lung Resistance-related Protein and Epidermal Growth Factor Receptor Expression in Lung Cancer

BackgroundY-box binding protein 1 (YB-1) is an oncogenic transcription factor that is activated in response to various genotoxic stresses. The purpose of this study was to elucidate whether YB-1 correlates with the expression of lung resistance–related protein (LRP) and epidermal growth factor receptor (EGFR) in primary lung cancer. Patients and MethodsOne hundred and five non–small-cell lung cancer (NSCLC) specimens were analyzed by immunohistochemistry. Knockdown of YB-1 messenger RNA by small interfering RNA(siRNA) was tested for the lung cancer cell lines A549 and Calu-3. ResultsNuclear YB-1 expression significantly correlated with positive LRP and EGFR expression (P < .001). Nuclear YB-1 expression and positive LRP and EGFR expression were independent adverse prognostic factors in patients with NSCLC. Furthermore, patients with tumors positive for nuclear YB-1 and LRP had a significantly worse prognosis than those negative for nuclear YB-1 and LRP (P < .001). In addition, patients with tumors positive for nuclear YB-1 and EGFR had a significantly worse prognosis than those negative for nuclear YB-1 and EGFR (P < .001). In in vitro analyses that use the NSCLC cell lines A549 and Calu-3, the downregulation of YB-1 with siRNAs drastically decreased the expression of EGFR. However, downregulation of YB-1 remarkably decreased the expression of LRP in A549 cells; however, a slight decrease in LRP was induced by the downregulation of YB-1 in Calu-3 cells. ConclusionOur data demonstrate that nuclear YB-1 localization is associated with LRP and EGFR expression in NSCLC, and nuclear YB-1 localization and LRP and EGFR expression are of prognostic significance in NSCLC.

Landscape of EGFR signaling network in human cancers: Biology and therapeutic response in relation to receptor subcellular locations

The epidermal growth factor receptor (EGFR) pathway is one of the most dysregulated molecular pathways in human cancers. Despite its well-established importance in tumor growth, progression and drug-resistant phenotype over the past several decades, targeted therapy designed to circumvent EGFR has yielded only modest clinical success in cancer patients, except those with non-small cell lung cancer (NSCLC) carrying EGFR activation mutations. However, almost all of these NSCLC patients eventually developed resistance to small molecule EGFR kinase inhibitors. These disappointing outcomes are, in part, due to the high complexity and the interactive nature of the EGFR signaling network. More recent compelling evidence further indicates that EGFR functionality can be dependent on its subcellular location. In this regard, EGFR undergoes translocation into different organelles where it elicits distinctly different functions than its best known activity as a plasma membrane-bound receptor tyrosine kinase. EGFR can be shuttled into the cell nucleus and mitochondrion upon ligand binding, radiation, EGFR-targeted therapy and other stimuli. Nuclear EGFR behaves as transcriptional regulator, tyrosine kinase, and mediator of other physiological processes. The role of mitochondrial EGFR remains poorly understood but it appears to regulate apoptosis and autophagy. While studies using patient tumors have shown nuclear EGFR to be an indicator for poor clinical outcomes in cancer patients, the impact of mitochondrial EGFR on tumor behavior and patient prognosis remains to be defined. Most recently, several lines of evidence suggest that mislocated EGFR may regulate tumor response to therapy and that plasma membrane-bound EGFR elicits survival signals independent of its kinase activity. In light of these recent progresses and discoveries, we will outline in this minireview an emerging line of research that uncovers and functionally characterizes several novel modes of EGFR signaling that take center stage in the cell nucleus, mitochondrion and other subcellular compartments. We will also discuss the clinical implications of these findings in the rationale design for therapeutic strategy that overcomes tumor drug resistance.

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.

EGFR as a therapeutic target for human, canine, and mouse ACTH-secreting pituitary adenomas

Cushing disease is a condition in which the pituitary gland releases excessive adrenocorticotropic hormone (ACTH) as a result of an adenoma arising from the ACTH-secreting cells in the anterior pituitary. ACTH-secreting pituitary adenomas lead to hypercortisolemia and cause significant morbidity and mortality. Pituitary-directed medications are mostly ineffective, and new treatment options are needed. As these tumors express EGFR, we tested whether EGFR might provide a therapeutic target for Cushing disease. Here, we show that in surgically resected human and canine corticotroph cultured tumors, blocking EGFR suppressed expression of proopiomelanocortin (POMC), the ACTH precursor. In mouse corticotroph EGFR transfectants, ACTH secretion was enhanced, and EGF increased Pomc promoter activity, an effect that was dependent on MAPK. Blocking EGFR activity with gefitinib, an EGFR tyrosine kinase inhibitor, attenuated Pomc expression, inhibited corticotroph tumor cell proliferation, and induced apoptosis. As predominantly nuclear EGFR expression was observed in canine and human corticotroph tumors, we preferentially targeted EGFR to mouse corticotroph cell nuclei, which resulted in higher Pomc expression and ACTH secretion, both of which were inhibited by gefitinib. In athymic nude mice, EGFR overexpression enhanced the growth of explanted ACTH-secreting tumors and further elevated serum corticosterone levels. Gefitinib treatment decreased both tumor size and corticosterone levels; it also reversed signs of hypercortisolemia, including elevated glucose levels and excess omental fat. These results indicate that inhibiting EGFR signaling may be a novel strategy for treating Cushing disease.

Effection and mechanism of radiosensitivity of non-small cell lung cancer cell line H358 following gefitinib treatment

背景与目的表皮生长因子受体（epidermal growth factor receptor, EGFR）是决定放疗效应的重要因素，它的过表达或激活常与包括非小细胞肺癌在内的肿瘤放疗抵抗相关，因而阻断EGFR的信号通路是增强放疗敏感性很有潜力的治疗策略。本研究旨在观察小分子EGFR酪氨酸激酶抑制剂吉非替尼与放疗联合是否有提高非小细胞肺癌细胞株H358放疗敏感性的作用以及探索其分子机制。方法将非小细胞肺癌细胞株H358分为X线组和X线+吉非替尼组，前者采用单纯X线照射，后者经1 μmol/L吉非替尼作用24 h后再行X线照射。克隆形成实验比较两组细胞放射敏感性，免疫荧光激光共聚焦显微镜观察X线照射后各时间点细胞核中磷酸化γ-H2AX及EGFR焦点在细胞中的定位情况，Western blot法检测放疗后核蛋白中EGFR的表达。结果克隆形成实验中X线+吉非替尼组各个剂量点的细胞存活率均少于X线组，可见X线+吉非替尼组对放疗更敏感。免疫荧光激光共聚焦显示，X线+吉非替尼组比X线组各时段细胞核内γ-H2AX焦点数增加，持续的时间也更长。EGFR免疫荧光及Western blot结果显示，X线组EGFR在放疗后1 h内入核，而X线+吉非替尼组EGFR不在核内表达，仍位于细胞浆内。对Western blot结果用SPSS 13.0进行统计学分析，其差异有统计学意义（P=0.042）。结论吉非替尼可能是通过抑制EGFR放疗后入核进行损伤后DNA双链断裂修复，而起到对NSCLC细胞株H358放疗增敏的作用。

Strong nuclear EGFR expression in colorectal carcinomas is associated with cyclin-D1 but not with gene EGFR amplification

BackgroundPrognostic and predictive significance of epidermal growth factor receptor (EGFR) in colorectal carcinomas (CRCs) is still controversial. The aim of the present study was to explore and correlate membrane and nuclear EGFR and cyclin-D1 protein expression with EGFR gene status of tumor cells.MethodsImmunohistochemical and FISH analysis was performed on 135 archival formalin fixed and paraffin embedded CRCs.ResultsStrong membrane and strong nuclear EGFR staining was detected in 16% and 57% of cases, respectively, and strong cyclin-D1 expression in 57% samples. Gene EGFR amplification was identified in 5.9% and polysomy in 7.4% of cases, while 87% showed no EGFR gene changes. A statistically significant difference was only found between tumor grade and expression of membrane EGFR, while nuclear EGFR and cyclin-D1 expression was not associated with the clinicopathologic characteristics analyzed. Tumor cells displaying gene amplification and strong protein membrane EGFR expression overlapped, while EGFR gene status showed no correlation with nuclear EGFR and cyclin-D1. There was no association between membrane EGFR and cyclin-D1, whereas nuclear EGFR expression was strongly related to cyclin-D1 expression.ConclusionsStudy results revealed heterogeneity among CRCs, which could have a predictive value by identifying biologically and probably clinically different subsets of tumors with the possibly diverse response to anti-EGFR therapies.

Nuclear Epidermal Growth Factor Receptor as a Prognostic Factor for Rectal Cancers Patients Treated with Neoadjuvant Therapy

Results:Medianagewas63years(range,22–88years).Ofthepatients,initialStageI,II,andIIIwere41.9%,29.9%,and28.1%, respectively. We found 20.9% and 23.3% of the cohort with N-EGFR and C-EGFR, respectively. N-EGFR was found on the patients with advanced Pre-Tx tumor status (p = 0.017) and advanced Post-Tx tumor status (p\0.001). Patients with advanced Pre-Tx tumor and nodal status (p = 0.013 and p = 0.004, respectively), vascular invasion (p = 0.025) and perineural invasion (p = 0.048) have C-EGFR. N-EGFR was not correlated with C-EGFR (p = 0.54). Median follow-up was 48 months (range, 6 – 131 months). With the univariate analysis, N-EGFR revealed strong inverse correlation with local free survival (LFS), disease free survival (DFS) and metastases free survival (MFS) (p = 0.0014, 0.0005, and 0.0182, respectively). But the phenomena were not found on the patients with C-EGFR. Furthermore, with multivariate analysis, N-EGFR only showed adverse LFR (p = 0.016) and DFS (p = 0.006), but it was not revealed in MFS (p = 0.12). Conclusions:The overexpression of nuclear EGFR, instead of C-EGFR, in rectal cancers could contribute to the identification of patients who have an increased risk of local recurrences after neoadjuvant therapy and radical surgery.

EGFR Nuclear Import in Gallbladder Carcinoma: Nuclear Phosphorylated EGFR Upregulates iNOS Expression and Confers Independent Prognostic Impact

The understanding of epidermal growth factor receptor (EGFR) deregulation in carcinogenesis remains incomplete. We investigated the implications of EGFR gene status and EGFR nuclear translocation in gallbladder carcinoma (GBCA). Subcellular localization of EGFR and phosphorylated EGFR (pEGFR) was analyzed by fractional immunoblotting and confocal immunofluorescence in GBCA cell lines. pEGFR binding to iNOS promoter was assessed by chromatin immunoprecipitation with iNOS promoter activity evaluated by luciferase assay. EGFR, pEGFR, and iNOS were immunohistochemically assessable for localization and level in the training set of 104 GBCAs on tissue microarrays, with 76 cases analyzed for EGFR gene by chromogenic in situ hybridization (CISH) and mutant-enriched PCR targeting exons 19 and 21. The prognostic impact of nuclear pEGFR (N-pEGFR) immunoexpression was reaffirmed on whole sections of 58 GBCAs in the test set. Nuclear expression of EGFR and pEGFR was substantiated in vitro with augmented activity of iNOS promoter elicited by pEGFR binding upon EGF treatment. Despite no mutation, EGFR amplification, identified in 11 cases (15%) by CISH, strongly correlated with cytoplasmic EGFR expression (P < 0.001) but not with disease-specific survival (DSS). Immunoexpression of nuclear EGFR (N-EGFR), cytoplasmic pEGFR, and N-pEGFR was strongly related to that of iNOS (all ≤0.005). N-pEGFR independently predicted worse DSS in both training (P = 0.0468, HR = 2.024) and test sets (P = 0.0223, HR = 5.573). N-EGFR and N-pEGFR express in GBCA, conferring clinical aggressiveness partly through iNOS transactivation. Lacking response-predicting mutation, EGFR gene status, albeit amplified in 15% of GBCA, is neither related to nuclear EGFR translocation nor prognostically useful.

The poly(ADP-Ribose) polymerase inhibitor ABT-888 reduces radiation-induced nuclear EGFR and augments head and neck tumor response to radiotherapy

Background and purposeCurrent therapies for head and neck cancer frequently are not curative, necessitating novel therapeutic strategies. Thus, we studied whether inhibition of poly(ADP-Ribose) polymerase (PARP), a key DNA repair enzyme, could improve efficacy of radiotherapy in human head and neck cancer. Materials and methodsUM-SCC1, UM-SCC5, UM-SCC6, and FaDu human head and neck cancer cellular susceptibility to the PARP inhibitor (PARPi) ABT-888 and/or radiation (IR) was assessed using colony formation assays. DNA damage was evaluated using the alkaline comet assay and immunostaining for γ-H2AX foci. Non-homologous end-joining (NHEJ) mediated repair was measured using phospho-DNA-Pk foci. Epidermal growth factor receptor (EGFR) location was assessed by immunostaining. Poly ADP-Ribose polymerization (PAR) levels were assessed using immunoblotting. ResultsHuman head and neck cancer cells exhibited enhanced cytotoxicity with IR and ABT-888 compared to either agent alone. This increased susceptibility correlated with reduced nuclear EGFR, attenuation of NHEJ, and persistence of DNA damage following IR. Interestingly, a subset of head and neck cancer cells which had elevated basal PAR levels was susceptible to PARPi alone. ConclusionsCombining radiotherapy and PARP inhibition may improve outcomes and quality of life for head and neck cancer patients treated with radiotherapy. Furthermore, this novel strategy may also be feasible in other tumor types. Moreover, PAR levels should be investigated as a potential biomarker for tumor susceptibility to PARP inhibition.

Nuclear epidermal growth factor receptor modulates cellular radio-sensitivity by regulation of chromatin access

PurposeNuclear EGFR is involved in cellular stress management and regulation of cellular radio-sensitivity. The aim of this study was to elucidate the molecular mode of nuclear EGFR action. MethodsRadiation induced nuclear EGFR-shuttling and EGFR-foci formation was analyzed with immunohistochemistry and confocal microscopy. Composition of γH2AX–protein complexes was analyzed by western-blotting after immuno-precipitation. Functional relevance of nuclear EGFR was analyzed after siRNA mediated depletion of EGFR with respect to activation of ATM, histone H3 acetylation, residual DNA-damage and cell survival after irradiation. ResultsFollowing radiation nuclear EGFR was localized in foci similar to γH2AX. EGFR co-localized in a sub-fraction of γH2AX-foci. Analysis of composition of γH2AX-complexes revealed presence of EGFR, ATM, promyelocytic leukemia protein (PML), histone H3 and hetero-chromatin binding protein (HP1) in response to radiation. Depletion of EGFR protein inhibited ATM activation due to inhibition of acetylase TIP60 activity following irradiation. Consequently, histone H3 acetylation and phosphorylation was blocked and chromatin could not be opened for repair. Thus, residual DNA-damage was increased 24h after irradiation and cells were radio-sensitized. Comparable results were obtained when cells were treated with EGFR-NLS-peptide, which blocks EGFR nuclear shuttling specifically. ConclusionsNuclear EGFR is part of DNA-damage repair complex and is involved in regulation of TIP60-acetylase activity. TIP60 is essential for ATM activation and chromatin relaxation which is a prerequisite for DNA-repair in heterochromatic DNA. Thus interventional EGFR strategies during tumor treatment may also interact with DNA-repair by blocking access to damaged DNA.

Nuclear Translocation of Epidermal Growth Factor Receptor by Akt-dependent Phosphorylation Enhances Breast Cancer-resistant Protein Expression in Gefitinib-resistant Cells

Epidermal growth factor receptor (EGFR), an aberrantly overexpressed or activated receptor-tyrosine kinase in many cancers, plays a pivotal role in cancer progression and has been an attractive target for cancer therapy. Gefitinib and erlotinib, two EGFR-tyrosine kinase inhibitors, have been approved for non-small cell lung cancer. However, durable clinical efficacy of these EGFR inhibitors is severely limited by the emergence of acquired resistance. For example, the expression of breast cancer-resistant protein (BCRP/ABCG2) has been shown to confer acquired resistance of wild-type EGFR (wtEGFR)-expressing cancer cells to gefitinib. However, the underlying molecular mechanisms still remain unclear. Here, we show that wtEGFR expression is elevated in the nucleus of acquired gefitinib-resistant cancer cells. Moreover, nuclear translocation of EGFR requires phosphorylation at Ser-229 by Akt. In the nucleus, EGFR then targets the proximal promoter of BCRP/ABCG2 and thereby enhances its gene transcription. The nuclear EGFR-mediated BCRP/ABCG2 expression may contribute at least in part to the acquired resistance of wtEGFR-expressing cancer cells to gefitinib. Our findings shed light on the role of nuclear EGFR in the sensitivity of wtEGFR-expressing cancer cells to EGFR tyrosine kinase inhibitors and also deciphered a putative molecular mechanism contributing to gefitinib resistance through BCRP/ABCG2 expression.

A Functional Nuclear Epidermal Growth Factor Receptor, Src and Stat3 Heteromeric Complex in Pancreatic Cancer Cells

Evidence is presented for the nuclear presence of a functional heteromeric complex of epidermal growth factor (EGFR), Src and the Signal Transducer and Activator of Transcription (Stat)3 proteins in pancreatic cancer cells. Stat3 remains nuclear and associated with Src or EGFR, respectively, upon the siRNA knockdown of EGFR or Src, demonstrating the resistance of the complex to the modulation of EGFR or Src alone. Significantly, chromatin immunoprecipitation (ChIP) analyses reveal the nuclear EGFR, Src and Stat3 complex is bound to the c-Myc promoter. The siRNA knockdown of EGFR or Src, or the pharmacological inhibition of Stat3 activity only marginally suppressed c-Myc expression. By contrast, the concurrent modulation of Stat3 and EGFR, or Stat3 and Src, or EGFR and Src strongly suppressed c-Myc expression, demonstrating that the novel nuclear heteromeric complex intricately regulates the c-Myc gene. The prevalence of the transcriptionally functional EGFR, Src, and Stat3 nuclear complex provides an additional and novel mechanism for supporting the pancreatic cancer phenotype and explains in part the insensitivity of pancreatic cancer cells to the inhibition of EGFR, Src or Stat3 alone.

Abstract 2254: Nuclear and cytoplasmic epidermal growth factor receptor and p16 expression as prognostic biomarkers in head and neck squamous cell carcinoma

Abstract Introduction: Epidermal growth factor receptor (EGFR) and p16 staining have demonstrated to be strong prognostic factors in patients with head and neck squamous cell carcinoma (HNSCC). Patients with higher expression of EGFR in their tumors have been correlated with decreased survival and shorter time to recurrence. Patients with p16-positive (+) tumors [a surrogate marker of human papillomavirus (HPV) infection] have improved survival compared to p16-negative (−) tumors. We examined the interaction between the expression levels of total EGFR and p16 status, and further examined the association between nuclear EGFR and p16 status based on evidence that nuclear EGFR may have a distinct role in DNA damage repair and may function as a transcription factor. Methods: A tissue microarray (TMA) containing 123 cores obtained from 101 HNSCC tumors was analyzed for EGFR expression (clone H11; DAKO, Carpinteria, CA) using an automated quantitative analysis (AQUA), and for p16 expression (clone E6H4; MTM Laboratories Inc., Westbrough, MA) using immunohistochemical (IHC) staining. Duplicate cores from a patient were averaged for analyses. The EGFR and p16 data were correlated with clinical data including demographics, primary subsite, disease stage, and survival. Results: The total and nuclear EGFR data could be reliably obtained from 80 of 101 patients. The p16 data could be obtained from 87 of 101 patients [p16 (+), n=29; p16 (−), n=58]. The p16 staining was strongly associated with the oropharyngeal subsite (Chi2, p=&amp;lt;0.0001) and poorly differentiated histology (Cochran-Armitage Trend Test, p=0.01). The expression of total and nuclear EGFR was higher in p16 (−) tumors compared to p16 (+) tumors (Wilcoxon Rank Test, p=0.038 and p=0.014, respectively). Interestingly, the higher expression of non-nuclear EGFR (combined cytoplasmic and membranous) staining did not associate significantly with p16 (−) tumors. Statistically significant differences in recurrence-free survival or overall survival were not detectable based on the EGFR and p16 expression, likely due to the small sample size and heterogeneity in the patient population. Conclusions: The total and nuclear EGFR expression levels were higher in p16 (−) tumors compared to p16 (+); this may relate to recurrence and poor survival. Additionally, localization of EGFR may be a significant factor in its association with clinical outcomes. Further studies are indicated to determine the mechanistic link between these two prognostic factors and define the significance of EGFR localization to nucleus upon activation of the pathway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2254. doi:10.1158/1538-7445.AM2011-2254

Abstract 2031: A functional nuclear epidermal growth factor receptor, Src and Stat3 heteromeric complex in pancreatic cancer cells

Abstract Pancreatic cancer is an extremely lethal malignancy whose prognosis has not improved appreciably in the last decade. The disease is usually diagnosed only after it has reached an advanced or metastatic state but even local, surgically resectable, tumors have a fairly poor prognosis. This is further complicated by the fact that little is known about the underlying mechanisms of pancreatic cancer, as evidenced by a lack of any efficacious targeted therapies. While hyperactive epidermal growth factor receptor (EGFR), Src tyrosine kinase and Signal Transducer and Activator of Transcription (Stat)3 have been detected in pancreatic cancer and implicated in the disease, the exact mechanisms by which they promote the disease phenotype are not well understood. We present evidence of a functional heteromeric complex of EGFR, c-Src and Stat3 that is detected at the plasma membrane and cytoplasm, and inside the nucleus of pancreatic cancer cells. The inhibition of c-Src, but not EGFR kinase, reduced the level of nuclear EGFR levels. Furthermore, the inhibition of Src or EGFR kinase alone decreased nuclear Stat3 levels, while the greatest decrease occurred upon the combined inhibition of EGFR and Src kinase activities. Significantly, evidence shows that the nuclear EGFR, Src and Stat3 complex functions as a transcriptional complex. Thus, the siRNA knockdown of EGFR or Src, or the pharmacological inhibition of aberrant Stat3 activity only moderately decreased c-Myc, iNOS, and VEGF expression. By contrast, the knockdown of EGFR or Src together with the inhibition of Stat3 activity strongly suppressed c-Myc expression in Panc-1 and Colo-357 cells. Chromatin immunoprecipitation (ChIP) studies further validated these findings and showed that the nuclear EGFR, Src, and Stat3 complex is bound to the c-Myc promoter. Taken together, these data identify a novel and functional heteromeric EGFR, Src, and Stat3 complex that promotes the induction of c-Myc in pancreatic cancer cells. Our study provides additional insight into the mechanisms by which hyperactive EGFR, Src and Stat3 pathway promotes the pancreatic cancer phenotype. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2031. doi:10.1158/1538-7445.AM2011-2031