Understanding resistance to EGFR inhibitors-impact on future treatment strategies

Epidermal Growth Factor Receptor Cell Proliferation Signaling Pathways

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly upregulated in cancers such as in non-small-cell lung cancer, metastatic colorectal cancer, glioblastoma, head and neck cancer, pancreatic cancer, and breast cancer. Various mechanisms mediate the upregulation of EGFR activity, including common mutations and truncations to its extracellular domain, such as in the EGFRvIII truncations, as well as to its kinase domain, such as the L858R and T790M mutations, or the exon 19 truncation. These EGFR aberrations over-activate downstream pro-oncogenic signaling pathways, including the RAS-RAF-MEK-ERK MAPK and AKT-PI3K-mTOR pathways. These pathways then activate many biological outputs that are beneficial to cancer cell proliferation, including their chronic initiation and progression through the cell cycle. Here, we review the molecular mechanisms that regulate EGFR signal transduction, including the EGFR structure and its mutations, ligand binding and EGFR dimerization, as well as the signaling pathways that lead to G1 cell cycle progression. We focus on the induction of CYCLIN D expression, CDK4/6 activation, and the repression of cyclin-dependent kinase inhibitor proteins (CDKi) by EGFR signaling pathways. We also discuss the successes and challenges of EGFR-targeted therapies, and the potential for their use in combination with CDK4/6 inhibitors.

Molecular differences in the microsatellite stable phenotype between left-sided and right-sided colorectal cancer

Differences in the pathogenesis of microsatellite stable (MSS) sporadic colorectal cancers (CRCs) between left‐sided CRC (LC) and right‐sided CRC (RC) have not been clarified. To identify pathogenesis‐related genomic differences between MSS CRCs within the two locations, we performed a comprehensive molecular analysis using crypt isolation with samples from 92 sporadic CRCs. Microsatellite instability (MSI; high and low/negative) and DNA methylation status (low methylation epigenome; intermediate methylation epigenome [IME] or high methylation epigenome [HME]) were determined using polymerase chain reaction (PCR) microsatellite analysis and PCR‐bisulfite pyrosequencing, respectively. Additionally, mutations in the TP53, KRAS, BRAF and PIK3CA genes were examined using PCR‐bisulfite pyrosequencing (for KRAS and BRAF mutations) or PCR‐single conformation polymorphism (for TP53 and PIK3CA mutations), followed by sequencing of aberrant bands. Finally, a genome‐wide study using a copy number alteration (CNA)‐targeted single nucleotide polymorphism array was performed. Ninety‐two CRCs were classified into 71 MSS and 21 MSI phenotypes. We examined 71 CRCs with the MSS phenotype (LC, 56; RC, 15). Mutations in KRAS were associated with RC with the MSS phenotype, whereas mutations in TP53 were more frequently found in LC with the MSS phenotype. There were significant differences in the frequencies of KRAS and TP53 mutations in the IME between LC and RC with the MSS phenotype. Although CNA gains were associated with LC with the MSS phenotype, CNA losses were not major alterations associated with the MSS phenotype. These findings suggested that the molecular pathogenesis of the MSS phenotype in LC was different from that in RC.

What's new?

The classification of colorectal cancer (CRC) based on tumor location is simple, comprehensive, and consistent with recent attempts to characterize tumors by pathological and molecular features. Differences in the pathogenesis of microsatellite stable (MSS) sporadic CRCs between left‐sided CRC (LC) and right‐sided CRC (RC) have however not been clarified. Here, the authors found that TP53 mutations are closely associated with the development of LC whereas RC is characterized by KRAS mutations. Using an integrated genome‐wide analysis, they also show significant differences in copy number alterations. The findings suggest a different molecular pathogenesis of the MSS phenotype between LC and RC.

Discovery of N-((3R,4R)-4-Fluoro-1-(6-((3-methoxy-1-methyl-1H-pyrazol-4-yl)amino)-9-methyl-9H-purin-2-yl)pyrrolidine-3-yl)acrylamide (PF-06747775) through Structure-Based Drug Design: A High Affinity Irreversible Inhibitor Targeting Oncogenic EGFR Mutants with Selectivity over Wild-Type EGFR

Mutant epidermal growth factor receptor (EGFR) is a major driver of non-small-cell lung cancer (NSCLC). Marketed first generation inhibitors, such as erlotinib, effect a transient beneficial response in EGFR mutant NSCLC patients before resistance mechanisms render these inhibitors ineffective. Secondary oncogenic EGFR mutations account for approximately 50% of relapses, the most common being the gatekeeper T790M substitution that renders existing therapies ineffective. The discovery of PF-06459988 (1), an irreversible pyrrolopyrimidine inhibitor of EGFR T790M mutants, was recently disclosed.1 Herein, we describe our continued efforts to achieve potency across EGFR oncogenic mutations and improved kinome selectivity, resulting in the discovery of clinical candidate PF-06747775 (21), which provides potent EGFR activity against the four common mutants (exon 19 deletion (Del), L858R, and double mutants T790M/L858R and T790M/Del), selectivity over wild-type EGFR, and desirable ADME properties. Compound 21 is currently being evaluated in phase-I clinical trials of mutant EGFR driven NSCLC.

Clinical value of monoclonal antibodies and tyrosine kinase inhibitors in the treatment of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous group of malignant tumours that affects over 500,000 patients per year. Treatment failure is generally due to the heterogeneity of these tumours and to the serious adverse effects associated with treatment. Immunological system impairment, which is common in HNSCC, further contributes to treatment failure by mediating tumour escape mechanisms. To date, the only clinically approved targeted therapy agent is cetuximab, a monoclonal antibody (mAb) that binds to, and inhibits, epidermal growth factor receptor, which is widely overexpressed in HNSCC. Cetuximab has been proven to induce antibody-dependent cellular cytotoxicity, further magnifying its therapeutic effect. DNA sequencing of HNSCC cells has identified the presence of mutated genes, thus making their protein products potential targets for therapeutic inhibition. Immune mechanisms have been found to have a significant impact on carcinogenesis, thus providing the rationale to support efforts to identify anticancer compounds with immunomodulatory properties. In the context of the rapid development of novel targeted agents, the aim of the present paper is to review our current understanding of HNSCC and to review the novel anticancer agents (mAbs and TKIs) introduced in recent years, including an assessment of their efficacy and mechanisms of action.

In vivo and ex vivo cetuximab sensitivity assay using three-dimensional primary culture system to stratify KRAS mutant colorectal cancer

In clinic, cetuximab, an anti-EGFR antibody, improves treatment outcomes in colorectal cancer (CRC). KRAS-mutant CRC is generally resistant to cetuximab, although difference of the sensitivity among KRAS-mutants has not been studied in detail. We previously developed the cancer tissue-originated spheroid (CTOS) method, a primary culture method for cancer cells. We applied CTOS method to investigate whether ex vivo cetuximab sensitivity assays reflect the difference in sensitivity in the xenografts. Firstly, in vivo cetuximab treatment was performed with xenografts derived from 10 CTOS lines (3 KRAS-wildtype and 7 KRAS mutants). All two CTOS lines which exhibited tumor regression were KRAS-wildtype, meanwhile all KRAS-mutant CTOS lines grew more than the initial size: were resistant to cetuximab according to the clinical evaluation criteria, although the sensitivity was quite diverse. We divided KRAS-mutants into two groups; partially responsive group in which cetuximab had a substantial growth inhibitory effect, and resistant group which exhibited no effect. The ex vivo signaling assay with EGF stimulation revealed that the partially responsive group, but not the resistant group, exhibited suppressed ERK phosphorylation ex vivo. Furthermore, two lines from the partially responsive group, but none of the lines in the resistant group, exhibited a combinatory effect of cetuximab and trametinib, a MEK inhibitor, ex vivo and in vivo. Taken together, the results indicate that ex vivo signaling assay reflects the difference in sensitivity in vivo and stratifies KRAS mutant CTOS lines by sensitivity. Therefore, coupling the in vivo and ex vivo assays with CTOS can be a useful platform for understanding the mechanism of diversity in drug sensitivity.

Regulation of voltage-gated potassium channels attenuates resistance of side-population cells to gefitinib in the human lung cancer cell line NCI-H460

BACKGROUND

Side-population (SP) cells that exclude anti-cancer drugs have been found in various tumor cell lines. Moreover, SP cells have a higher proliferative potential and drug resistance than main population cells (Non-SP cells). Also, several ion channels are responsible for the drug resistance and proliferation of SP cells in cancer.

METHODS

To confirm the expression and function of voltage-gated potassium (Kv) channels of SP cells, these cells, as well as highly expressed ATP-binding cassette (ABC) transporters and stemness genes, were isolated from a gefitinib-resistant human lung adenocarcinoma cell line (NCI-H460), using Hoechst 33342 efflux.

RESULTS

In the present study, we found that mRNA expression of Kv channels in SP cells was different compared to Non-SP cells, and the resistance of SP cells to gefitinib was weakened with a combination treatment of gefitinib and Kv channel blockers or a Kv7 opener, compared to single-treatment gefitinib, through inhibition of the Ras-Raf signaling pathway.

CONCLUSIONS

The findings indicate that Kv channels in SP cells could be new targets for reducing the resistance to gefitinib.

Concurrent Autophagy Inhibition Overcomes the Resistance of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors in Human Bladder Cancer Cells

Despite the potential therapeutic efficacy of epithelial growth factor receptor (EGFR) inhibitors in the treatment of advanced stage bladder cancer, there currently is no clear evidence to support this hypothesis. In this study, we investigate whether the concurrent treatment of autophagy-blocking agents with EGFR inhibitors exerts synergistic anti-cancer effects in T24 and J82 human bladder cancer cells. Lapatinib and gefitinib were used as EGFR inhibitors, and bafilomycin A1 (BFA1), chloroquine (CQ) and 3-methyladenine (3-MA) were used as the pharmacologic inhibitors of autophagy activities. To assess the proliferative and self-renewal capabilities, the Cell Counting Kit-8 (CCK-8) assay and a clonogenic assay were performed, respectively. To examine apoptotic cell death, flow cytometry using annexin-V/propidium iodide (PI) was used. To measure the autophagy activities, the expression levels of LC3I and II was determined by Western blot analysis. To validate the synergistic effects of autophagy inhibition with EGFR inhibitors, we specifically blocked key autophagy regulatory gene ATG12 by transfection of small interference RNA and examined the phenotypic changes. Of note, lapatinib and gefitinib triggered autophagy activities in T24 and J82 human bladder cancer cells, as indicated by upregulation of LC3II. More importantly, inhibiting autophagy activities with pharmacologic inhibitors (BFA1, CQ or 3-MA) remarkably reduced the cell viabilities and clonal proliferation of T24 and J82 cells, compared to those treated with either of the agents alone. We also obtained similar results of the enhanced anti-cancer effects of EGFR inhibitors by suppressing the expression of ATG12. Notably, the apoptotic assay showed that synergistic anti-cancer effects were induced via the increase of apoptotic cell death. In summary, concomitant inhibition of autophagy activities potentiated the anti-cancer effects of EGFR inhibitors in human bladder cancer cells, indicating a novel therapeutic strategy to treat advanced bladder cancer.

Advances in the study of berberine and its derivatives: a focus on anti-inflammatory and anti-tumor effects in the digestive system

It has been widely recognized that inflammation, particularly chronic inflammation, can increase the risk of cancer and that the simultaneous treatment of inflammation and cancer may produce excellent therapeutic effects. Berberine, an alkaloid isolated from Rhizoma coptidis, has broad applications, particularly as an antibacterial agent in the clinic with a long history. Over the past decade, many reports have demonstrated that this natural product and its derivatives have high activity against both cancer and inflammation. In this review, we summarize the advances in studing berberine and its derivatives as anti-inflammatory and anti-tumor agents in the digestive system; we also discuss their structure-activity relationship. These data should be useful for the development of this natural product as novel anticancer drugs with anti-inflammation activity.

HER2 Amplification and Cetuximab Efficacy in Patients With Metastatic Colorectal Cancer Harboring Wild-type RAS and BRAF

BACKGROUND

Cetuximab has shown clinical benefit in patients with metastatic colorectal cancer (mCRC) harboring wild-type RAS. Human epidermal growth factor receptor 2 (HER2) amplification may be a mechanism of cetuximab resistance. We evaluated the association between HER2 amplification and cetuximab efficacy in patients with mCRC harboring wild-type RAS and BRAF.

PATIENTS AND METHODS

Between December 2003 and June 2013, we identified 142 patients with mCRC whose tumors harbored both wild-type exons 2, 3, and 4 in KRAS and NRAS, and wild-type exon 15 in BRAF using high throughput sequencing (OncoMap version 4.0). All patients received cetuximab after oxaliplatin, irinotecan, and fluoropyrimidine failure. HER2 status was determined using immunohistochemistry and silver in situ hybridization (SISH) and correlated with cetuximab efficacy.

RESULTS

Of 142 RAS and BRAF wild-type tumors, we observed 7 cases (4.9%) of HER2 amplification by SISH. After a median follow-up of 13.2 months (range, 1.4-78.1 months), median progression-free survival (PFS) was significantly different according to HER2 status: 3.1 months in patients with HER2 amplification compared with 5.6 months in those with non-amplified HER2 (hazard ratio, 2.73; 95% confidence interval, 1.18-6.31; P = .019). Overall survival (OS) was not significantly different between groups, although there was a tendency towards shorter OS in patients with HER2-amplified tumors (hazard ratio, 1.31; 95% confidence interval, 0.61-2.82; 10.1 vs. 13.5 months; P = .488).

CONCLUSIONS

HER2 amplification is predictive of shorter PFS after cetuximab treatment in patients with mCRC harboring wild-type RAS and BRAF. Further study is warranted for this patient population.

Antitumor Efficacy of SLPI Promoter-Controlled Expression of Artificial microRNA Targeting EGFR in a Squamous Cell Carcinoma Cell Line

The purpose of this study was to develop a recombinant adenovirus with secretory leukoprotease inhibitor (SLPI) promoter-controlled expression for gene therapy of squamous cell carcinoma (SCC). An artificial microRNA targeting epidermal growth factor receptor (EGFR) was designed, and used to construct a replication-defective recombinant adenovirus with SLPI promoter-controlled expression. The silencing efficiency of this vector (Ad-SLPI-EGFRamiR) was detected in Hep-2 cells. Western blotting showed that the expression of 170 kD EGFR was significantly reduced in Hep-2 cells 72 h after infection with Ad-SLPI-EGFRamiR. At a multiplicity of infection (MOI) of 200 pfu/cell, proliferation of Hep-2 cells was highly inhibited by Ad-SLPI-EGFRamiR (inhibition rate: ~70%). The apoptosis rate of Hep-2 cells at 72 h after infection with Ad-SLPI-EGFRamiR at a MOI 35 pfu/cell was 32.8%. The adenovirus constructed was able to specifically inhibit the growth of SCC cells in vitro.

Association of BIM Deletion Polymorphism and BIM-γ RNA Expression in NSCLC with EGFR Mutation

AIM

This pilot study assessed the association of BIM deletion polymorphism and BIM RNA isoform in patients with EGFR-positive non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

The study included 33 patients with EGFR-positive NSCLC treated with gefitinib. BIM deletion polymorphism and BIM RNA isoform (EL/L/S/γ) were determined by polymerase chain reaction (PCR).

RESULTS

BIM-γ expression was significantly higher in patients with BIM deletion polymorphism than among those without BIM deletion polymorphism inside tumors (p=0.038) and around tumors (p=0.0024). Relative BIM-γ expression was significantly higher in patients with BIM deletion polymorphism than among those without BIM deletion polymorphism (p=0.0017). Patients with BIM-γ had significantly shorter progression-free survival than those without BIM-γ (median: 304 vs. 732 days; p=0.023).

CONCLUSION

Expression of BIM-γ mRNA and BIM deletion polymorphism were strongly associated. BIM-γ overexpression may have a role in apoptosis related to EGFR-tyrosine kinase inhibitor.

Metabolomics analysis reveals aminoquinazolin derivative 9d-induced oxidative stress and cell cycle arrest in A549 cells

An UPLC/Q-TOF MS based metabolomics approach was established to study the probable antitumor mechanism of aminoquinazolin derivative 9d, which could induce oxidative stress and cell cycle arrest in A549 lung cancer cells.

Novel Adamantanyl-Based Thiadiazolyl Pyrazoles Targeting EGFR in Triple-Negative Breast Cancer

The epidermal growth factor receptor (EGFR) is a validated therapeutic target for triple-negative breast cancer (TNBC). In the present study, we synthesize novel adamantanyl-based thiadiazolyl pyrazoles by introducing the adamantane ring to thiazolopyrazoline. On the basis of loss of cell viability in TNBC cells, 4-(adamantan-1-yl)-2-(3-(2,4-dichlorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)thiazole (APP) was identified as a lead compound. Using a Parzen-Rosenblatt Window classifier, APP was predicted to target the EGFR protein, and the same was confirmed by surface plasmon resonance. Further analysis revealed that APP suppressed the phosphorylation of EGFR at Y992, Y1045, Y1068, Y1086, Y1148, and Y1173 in TNBC cells. APP also inhibited the phosphorylation of ERK at Y204 and of STAT3 at Y705, implying that APP downregulates the activity of EGFR downstream effectors. Small interfering RNA mediated depletion of EGFR expression prevented the effect of APP in BT549 and MDA-MB-231 cells, indicating that APP specifically targets the EGFR. Furthermore, APP modulated the expression of the proteins involved in cell proliferation and survival. In addition, APP altered the expression of epithelial-mesenchymal transition related proteins and suppressed the invasion of TNBC cells. Hence, we report a novel and specific inhibitor of the EGFR signaling cascade.

NMU signaling promotes endometrial cancer cell progression by modulating adhesion signaling

Neuromedin U (NMU) was originally named based on its strong uterine contractile activity, but little is known regarding its signaling/functions in utero. We identified that NMU and one of its receptors, NMUR2, are not only present in normal uterine endometrium but also co-expressed in endometrial cancer tissues, where the NMU level is correlated with the malignant grades and survival of patients. Cell-based assays further confirmed that NMU signaling can promote cell motility and proliferation of endometrial cancer cells derived from grade II tumors. Activation of NMU pathway in these endometrial cancer cells is required in order to sustain expression of various adhesion molecules, such as CD44 and integrin alpha1, as well as production of their corresponding extracellular matrix ligands, hyaluronan and collagen IV; it also increased the activity of SRC and its downstream proteins RHOA and RAC1. Thus, it is concluded that NMU pathway positively controls the adhesion signaling-SRC-Rho GTPase axis in the tested endometrial cancer cells and that changes in cell motility and proliferation can occur when there is manipulation of NMU signaling in these cells either in vitro or in vivo. Intriguingly, this novel mechanism also explains how NMU signaling promotes the EGFR-driven and TGFβ receptor-driven mesenchymal transitions. Through the above axis, NMU signaling not only can promote malignancy of the tested endometrial cancer cells directly, but also helps these cells to become more sensitive to niche growth factors in their microenvironment.

Cetuximab Resistance in Head and Neck Cancer Is Mediated by EGFR-K521 Polymorphism

Head and neck squamous cell carcinomas (HNSCC) exhibiting resistance to the EGFR-targeting drug cetuximab poses a challenge to their effective clinical management. Here, we report a specific mechanism of resistance in this setting based upon the presence of a single nucleotide polymorphism encoding EGFR-K₅₂₁ (K-allele), which is expressed in >40% of HNSCC cases. Patients expressing the K-allele showed significantly shorter progression-free survival upon palliative treatment with cetuximab plus chemotherapy or radiation. In several EGFR-mediated cancer models, cetuximab failed to inhibit downstream signaling or to kill cells harboring a high K-allele frequency. Cetuximab affinity for EGFR-K₅₂₁ was reduced slightly, but ligand-mediated EGFR activation was intact. We found a lack of glycan sialyation on EGFR-K₅₂₁ that associated with reduced protein stability, suggesting a structural basis for reduced cetuximab efficacy. CetuGEX, an antibody with optimized Fc glycosylation targeting the same epitope as cetuximab, restored HNSCC sensitivity in a manner associated with antibody-dependent cellular cytotoxicity rather than EGFR pathway inhibition. Overall, our results highlight EGFR-K₅₂₁ expression as a key mechanism of cetuximab resistance to evaluate prospectively as a predictive biomarker in HNSCC patients. Further, they offer a preclinical rationale for the use of ADCC-optimized antibodies to treat tumors harboring this EGFR isoform. Cancer Res; 77(5); 1188-99. ©2016 AACR.

High Intra- and Inter-Tumoral Heterogeneity of RAS Mutations in Colorectal Cancer

Approximately 30% of patients with wild type RAS metastatic colorectal cancer are non-responders to anti-epidermal growth factor receptor monoclonal antibodies (anti-EGFR mAbs), possibly due to undetected tumoral subclones harboring RAS mutations. The aim of this study was to analyze the distribution of RAS mutations in different areas of the primary tumor, metastatic lymph nodes and distant metastasis. A retrospective cohort of 18 patients with a colorectal cancer (CRC) was included in the study. Multiregion analysis was performed in 60 spatially separated tumor areas according to the pathological tumor node metastasis (pTNM) staging and KRAS, NRAS and BRAF mutations were tested using pyrosequencing. In primary tumors, intra-tumoral heterogeneity for RAS mutation was found in 33% of cases. Inter-tumoral heterogeneity for RAS mutation between primary tumors and metastatic lymph nodes or distant metastasis was found in 36% of cases. Moreover, 28% of tumors had multiple RAS mutated subclones in the same tumor. A high proportion of CRCs presented intra- and/or inter-tumoral heterogeneity, which has relevant clinical implications for anti-EGFR mAbs prescription. These results suggest the need for multiple RAS testing in different parts of the same tumor and/or more sensitive techniques.

Deregulation of the miR-16-KRAS axis promotes colorectal cancer

KRAS plays a significant role in the etiology and progression of colorectal cancer (CRC), but the mechanism underlying this process has not been fully elucidated. In this study, we found that the KRAS protein levels were higher in CRC tissues than in the normal adjacent tissues, whereas its mRNA levels varied irregularly, suggesting that a post-transcriptional mechanism is involved in the regulation of KRAS. Then, we performed bioinformatic analyses to search for miRNAs that potentially target KRAS. We predicted and experimentally validated that miR-16 directly recognizes the 3'-UTR of the KRAS transcript and regulates KRAS expression. Furthermore, the in vitro results showed that the repression of KRAS by miR-16 suppressed the proliferation and invasion and induced the apoptosis of CRC cells, and the in vivo results revealed that miR-16 exerted a tumor-suppressive effect by negatively regulating KRAS in xenograft mice. Taken together, our findings provide evidence supporting the role of miR-16 as a tumor suppressor in CRC by targeting KRAS.

Co-targeting of EGF receptor and neuropilin-1 overcomes cetuximab resistance in pancreatic ductal adenocarcinoma with integrin β1-driven Src-Akt bypass signaling

Pancreatic ductal adenocarcinoma (PDAC) cells usually overexpress the epidermal growth factor receptor (EGFR); however, most are resistant to the anti-EGFR monoclonal antibody, cetuximab. In this study, we report that the molecular mechanism of resistance to cetuximab in PDAC cells is mediated by the overexpression of active integrin β1 with downstream Src-Akt activation; this triggers an EGFR ligand-independent proliferation signaling, bypassing EGFR-blocking effect. Knockdown of integrin β1 or inhibition of Src or Akt sensitized cetuximab-resistant (Ctx^R) PDAC cells to cetuximab. We found that neuropilin-1 (NRP1) physically interacts with active integrin β1, but not inactive one, on the cell surface. To inhibit active integrin β1-driven signaling by targeting NRP1, while suppressing EGFR signaling, we generated an EGFR and NRP1 dual targeting antibody, Ctx-TPP11, by genetic fusion of the NRP1-targeting peptide, TPP11, to the C terminus of the cetuximab heavy chain (Ctx-TPP11). We demonstrate that Ctx-TPP11 efficiently inhibited the growth of Ctx^R PDAC cells, in vitro and in vivo. The sensitization mechanism involved downregulating active integrin β1 levels through NRP1-coupled internalization mediated by the TPP11 moiety, leading to the inhibition of active integrin β1-driven bypass signaling. Our findings identify aberrant active integrin β1-driven Src-Akt hyperactivation as a primary resistance mechanism to cetuximab in PDAC cells and offer an effective therapeutic strategy to overcome this resistance using an EGFR and NRP1 dual targeting antibody.

KITENIN functions as a fine regulator of ErbB4 expression level in colorectal cancer via protection of ErbB4 from E3-ligase Nrdp1-mediated degradation

Understanding the complex biological functions of E3-ubiquitin ligases may facilitate the development of mechanism-based anti-cancer drugs. We recently identified that the KITENIN/ErbB4-Dvl2-c-Jun axis works as a novel unconventional downstream signal of epidermal growth factor (EGF) in colorectal cancer (CRC) tissues. Here we addressed whether E3-ubiquitin ligases are required for operation of this axis. We found that Nrdp1, an E3-ligase for ErbB3/ErbB4, interacted with KITENIN (KAI1 C-terminal interacting tetraspanin) to form a functional KITENIN/ErbB4/Nrdp1 complex and is responsible for down-regulating Dvl2 within this complex. Interestingly, ErbB4 was resistant to degradation by Nrdp1 in KITENIN/Nrdp1-co-transfected CRC cells, and KITENIN bound to the C-terminal coiled-coil domain of Nrdp1. Chemical blockade of ErbB kinase did not block the action of EGF to increase in total/phospho-ErbB4 and phospho-ERK in KITENIN/ErbB4-cotransfected cells, whereas it blocked the action of EGF in ErbB4 alone-transfected CRC cells. In human CRC tissues, higher expressions of ErbB4 and KITENIN and lower expression of Dvl2 was observed in stage IV samples than in stage I, but a low level of Nrdp1 was expressed in both stages and it did not differ significantly by stage. These results indicated that Nrdp1 is necessary for the reduction in Dvl2 to generate c-Jun in the EGF-KITENIN/ErbB4-c-Jun axis, but more importantly, elevated KITENIN protects KITENIN-bound ErbB4 from Nrdp1-mediated degradation via physical collaboration between the KITENIN/ErbB4 complex and Nrdp1, but not via modulation of ErbB kinase activity. Thus, KITENIN functions in the maintenance of a higher expression level of ErbB4 in advanced CRC tissues, independent of ubiquitin-mediated degradation via Nrdp1. © 2016 Wiley Periodicals, Inc.

Extracellular region of epidermal growth factor receptor: a potential target for anti-EGFR drug discovery

The epidermal growth factor receptor (EGFR) is a transmembrane receptor with tyrosine kinase activity involved in regulation of cellular multiplication, survival, differentiation and metastasis. Our knowledge about function and complex management of these receptors has driving the development of specific and targeted treatment modalities for human cancers in the last 20 years. EGFR is the first receptor target against which monoclonal antibodies (mAb) have been evolved for cancer treatment. Here we review the biology of ErbB receptors, including their architecture, signaling, regulation and therapeutic strategies and the mechanisms of resistances offered by the receptors against small-molecule tyrosine kinases and resistance overcome implications of mAbs. The efficacy of EGFR-specific mAb in cancer depends on site specific extracellular region of EGFR, which has crucial role in process of dimerization and activation. This review highlights evolution of various resistance mechanisms due to consequences of current small-molecule anti-EGFR therapies.

Interleukin-1 beta transactivates epidermal growth factor receptor via the CXCL1-CXCR2 axis in oral cancer

Hyperactivation of the epidermal growth factor receptor (EGFR) pathways and chronic inflammation are common characteristics of oral squamous cell carcinoma (OSCC). Previously, we reported that OSCC cells secrete interleukin-1 beta (IL-1β), which promotes the proliferation of the oral premalignant cell line, DOK, and stimulates DOK and OSCC cells to produce the chemokine CXCL1. CXCL1 functions through CXCR2, a G protein-coupled receptor that transactivates EGFR in ovarian and lung cancers. We hypothesized that IL-1β transactivates EGFR through the CXCL1–CXCR2 axis in OSCC. In this study, we demonstrated that tyrosine phosphorylation of EGFR is crucial for the IL-1β-mediated proliferation and subsequent bromodeoxyuridine (BrdU) incorporation of DOK cells because the EGFR inhibitors AG1478 and erlotinib inhibit these abilities in a dose-dependent manner. Addition of IL-1β instantly enhanced CXCL1 expression and secretion (within 15 min) in the DOK and OSCC cell lines. Furthermore, tyrosine phosphorylation of EGFR was significantly enhanced in DOK (1 h) and OSCC (20 min) cell lines after IL-1β treatment, and both cell lines were inhibited on the addition of an IL-1 receptor antagonist (IL-1Ra). CXCL1 treatment resulted in EGFR phosphorylation, whereas the knockdown of CXCL1 expression by lentivirus-mediated shRNA or the addition of the CXCR2 antagonist SB225002 dramatically reduced IL-1β-mediated EGFR phosphorylation and proliferation of DOK cells. Neutralizing antibodies against IL-1β or CXCL1 markedly inhibited the constitutive or IL-1β-induced tyrosine phosphorylation of EGFR in OSCC cells. IL-1β transactivates EGFR through the CXCL1-CXCR2 axis, revealing a novel molecular network in OSCC that is associated with autocrine IL-1β and EGFR signaling.

Quercetin suppresses lung cancer growth by targeting Aurora B kinase

aurora B kinase is highly expressed in several cancer cells and promotes tumorigenesis and progression, and therefore, it is an important target for drug to treat tumors. Quercetin was identified to be an antitumor agent. Herein, we report for the first time that quercetin inhibited aurora B activities by directly binding with aurora B in vitro and in vivo. Ex vivo studies showed that quercetin inhibited aurora B activities in JB6 Cl41 cells and A549 lung cancer cells. Moreover, knockdown of aurora B in A549 cells decreased their sensitivities to quercetin. In vivo study demonstrated that injection of quercetin in A549 tumor‐bearing mice effectively suppressed cancer growth. The phosphorylation of histone 3 in tumor tissues was also decreased after quercetin treatment. In short, quercetin can suppress growth of lung cancer cells as an aurora B inhibitor both in vitro and in vivo.

Anti-tubulin drugs conjugated to anti-ErbB antibodies selectively radiosensitize

Tumour resistance to radiotherapy remains a barrier to improving cancer patient outcomes. To overcome radioresistance, certain drugs have been found to sensitize cells to ionizing radiation (IR). In theory, more potent radiosensitizing drugs should increase tumour kill and improve patient outcomes. In practice, clinical utility of potent radiosensitizing drugs is curtailed by off-target side effects. Here we report potent anti-tubulin drugs conjugated to anti-ErbB antibodies selectively radiosensitize to tumours based on surface receptor expression. While two classes of potent anti-tubulins, auristatins and maytansinoids, indiscriminately radiosensitize tumour cells, conjugating these potent anti-tubulins to anti-ErbB antibodies restrict their radiosensitizing capacity. Of translational significance, we report that a clinically used maytansinoid ADC, ado-trastuzumab emtansine (T-DM1), with IR prolongs tumour control in target expressing HER2+ tumours but not target negative tumours. In contrast to ErbB signal inhibition, our findings establish an alternative therapeutic paradigm for ErbB-based radiosensitization using antibodies to restrict radiosensitizer delivery.

Drugs that sensitize tumour cells to ionizing radiation are prized because they can overcome resistance to radiotherapy. Here, the authors show that anti-tubulin drugs conjugated to cetuximab or trastuzumab can radiosensitize EGFR- or HER2-expressing tumors by increasing DNA damage and cell death due to ionizing radiation.

The Role of Interleukin-1 in Inflammatory and Malignant Human Skin Diseases and the Rationale for Targeting Interleukin-1 Alpha

Inflammation plays a major role in the induction and progression of several skin diseases. Overexpression of the major epidermal proinflammatory cytokines interleukin (IL) 1 alpha (IL-1α) and 1 beta (IL-1β) is positively correlated with symptom exacerbation and disease progression in psoriasis, atopic dermatitis, neutrophilic dermatoses, skin phototoxicity, and skin cancer. IL-1β and the interleukin-1 receptor I (IL-1RI) have been used as a therapeutic target for some autoinflammatory skin diseases; yet, their system-wide effects limit their clinical usage. Based on the local effects of extracellular IL-1α and its precursor, pro-IL-1α, we hypothesize that this isoform is a promising drug target for the treatment and prevention of many skin diseases. This review provides an overview on IL-1α and IL-β functions, and their contribution to inflammatory and malignant skin diseases. We also discuss the current treatment regimens, and ongoing clinical trials, demonstrating the potential of targeting IL-1α, and not IL-1β, as a more effective strategy to prevent or treat the onset and progression of various skin diseases.

Detection of Therapeutically Targetable Driver and Resistance Mutations in Lung Cancer Patients by Next-Generation Sequencing of Cell-Free Circulating Tumor DNA

PURPOSE

The expanding number of targeted therapeutics for non-small cell lung cancer (NSCLC) necessitates real-time tumor genotyping, yet tissue biopsies are difficult to perform serially and often yield inadequate DNA for next-generation sequencing (NGS). We evaluated the feasibility of using cell-free circulating tumor DNA (ctDNA) NGS as a complement or alternative to tissue NGS.

EXPERIMENTAL DESIGN

A total of 112 plasma samples obtained from a consecutive study of 102 prospectively enrolled patients with advanced NSCLC were subjected to ultra-deep sequencing of up to 70 genes and matched with tissue samples, when possible.

RESULTS

We detected 275 alterations in 45 genes, and at least one alteration in the ctDNA for 86 of 102 patients (84%), with EGFR variants being most common. ctDNA NGS detected 50 driver and 12 resistance mutations, and mutations in 22 additional genes for which experimental therapies, including clinical trials, are available. Although ctDNA NGS was completed for 102 consecutive patients, tissue sequencing was only successful for 50 patients (49%). Actionable EGFR mutations were detected in 24 tissue and 19 ctDNA samples, yielding concordance of 79%, with a shorter time interval between tissue and blood collection associated with increased concordance (P = 0.038). ctDNA sequencing identified eight patients harboring a resistance mutation who developed progressive disease while on targeted therapy, and for whom tissue sequencing was not possible.

CONCLUSIONS

Therapeutically targetable driver and resistance mutations can be detected by ctDNA NGS, even when tissue is unavailable, thus allowing more accurate diagnosis, improved patient management, and serial sampling to monitor disease progression and clonal evolution. Clin Cancer Res; 22(23); 5772-82. ©2016 AACR.

The correlation between FDG uptake and biological molecular markers in pancreatic cancer patients

PURPOSE

We examined whether fluorine-18 fluorodeoxyglucose (FDG) uptake is related to the mammalian target of rapamycin (mTOR) signal pathway and its related proteins in pancreatic cancer patients.

METHODS

We retrospectively studied 53 pancreatic cancer patients who underwent FDG positron emission tomography (PET) or FDG PET/CT, and complete curative surgical resection. The SUV max, the tumor to nontumor activity of pancreas [T/N (P)] ratio and the T/N of liver [T/N (L)] ratio were calculated. The expressions of glucose transporter-1(Glut-1) and mTOR pathway proteins in pancreas cell lines were examined by immune blots. Excised tumor tissue was analyzed by immunohistochemistry using monoclonal antibodies for Glut-1, epidermal growth factor receptor (EGFR), mTOR, p70S6kinase (p70S6) and S6 ribosomal protein (S6).

RESULTS

The expressions of Glut-1, EGFR and p70S6 were significantly correlated with the SUV max, T/N (P) ratio and T/N (L) ratio. The expressions of mTOR and S6 were not correlated with all parameters. The expression of Glut-1 was positively correlated with the expressions of EGFR and p70S6, but not with mTOR or S6. S6 was positively correlated with p70S6.

CONCLUSIONS

Glut-1, EGFR and p70S6 expressions are associated with the FDG uptake mechanism of pancreatic cancer. FDG uptake may predict the levels of EGFR and p70S6 expressions, and FDG uptake reflects glucose metabolism and cancer progression.

Activation of Epidermal Growth Factor Receptor in Macrophages Mediates Feedback Inhibition of M2 Polarization and Gastrointestinal Tumor Cell Growth

EGF receptor (EGFR) in tumor cells serves as a tumor promoter. However, information about EGFR activation in macrophages in regulating M2 polarization and tumor development is limited. This study aimed to investigate the effects of EGFR activation in macrophages on M2 polarization and development of gastrointestinal tumors. IL-4, a cytokine to elicit M2 polarization, stimulated release of an EGFR ligand, HB-EGF, and transactivation and down-regulation of EGFR in Raw 264.7 cells and peritoneal macrophages from WT mice. Knockdown of HB-EGF in macrophages inhibited EGFR transactivation by IL-4. IL-4-stimulated STAT6 activation, Arg1 and YM1 gene expression, and HB-EGF production were further enhanced by inhibition of EGFR activity in Raw 264.7 cells using an EGFR kinase inhibitor and in peritoneal macrophages from Egfr(wa5) mice with kinase inactive EGFR and by knockdown of EGFR in peritoneal macrophages from Egfr(fl/fl) LysM-Cre mice with myeloid cell-specific EGFR deletion. Chitin induced a higher level of M2 polarization in peritoneal macrophages in Egfr(fl/fl) LysM-Cre mice than that in Egfr(fl/fl) mice. Accordingly, IL-4-conditioned medium stimulated growth and epithelial-to-mesenchymal transition in gastric epithelial and colonic tumor cells, which were suppressed by that from Raw 264.7 cells with HB-EGF knockdown but promoted by that from Egfr(wa5) and Egfr(fl/fl) LysM-Cre peritoneal macrophages. Clinical assessment revealed that the number of macrophages with EGFR expression became less, indicating decreased inhibitory effects on M2 polarization, in late stage of human gastric cancers. Thus, IL-4-stimulated HB-EGF-dependent transactivation of EGFR in macrophages may mediate inhibitory feedback for M2 polarization and HB-EGF production, thereby inhibiting gastrointestinal tumor growth.

Functional screening implicates miR-371-3p and peroxiredoxin 6 in reversible tolerance to cancer drugs

Acquired resistance to cancer drug therapies almost always occurs in advanced-stage patients even following a significant response to treatment. In addition to mutational mechanisms, various non-mutational resistance mechanisms have now been recognized. We previously described a chromatin-mediated subpopulation of reversibly drug-tolerant persisters that is dynamically maintained within a wide variety of tumour cell populations. Here we explore a potential role for microRNAs in such transient drug tolerance. Functional screening of 879 human microRNAs reveals miR-371-3p as a potent suppressor of drug tolerance. We identify PRDX6 (peroxiredoxin 6) as a key target of miR-371-3p in establishing drug tolerance by regulating PLA2/PKCα activity and reactive oxygen species. PRDX6 expression is associated with poor prognosis in cancers of multiple tissue origins. These findings implicate miR-371-3p as a suppressor of PRDX6 and suggest that co-targeting of peroxiredoxin 6 or modulating miR-371-3p expression together with targeted cancer therapies may delay or prevent acquired drug resistance.

Acquired resistance significantly limits the efficacy of cancer drug therapies. Here, the authors identify miR-371-3p as a suppressor of drug tolerance in cancer cell lines by its target gene PRDX6, which in turn regulates PLA2/PKCα signalling and ROS levels.

Gefitinib in the treatment of nonsmall cell lung cancer with activating epidermal growth factor receptor mutation

Lung cancer is still the main cause of cancer-related deaths worldwide, with most patients present with advanced disease and poor long-term prognosis. The aim of lung cancer treatment is to slow down the progression of the disease, to relieve the patients from the lung cancer symptoms and whenever possible, to increase the overall survival. The discovery of small molecule targeting tyrosine kinase of epidermal growth factor receptor opens a new way in the management of advanced nonsmall cell lung cancer (NSCLC). This review will discuss several Phase II and III trials evaluated the clinical efficacy of gefitinib as monotherapy in pretreated patients with advanced NSCLC, as well as both monotherapy and combined with chemotherapy in chemotherapy-naive patients.

ASCT2 (SLC1A5) is an EGFR-associated protein that can be co-targeted by cetuximab to sensitize cancer cells to ROS-induced apoptosis

Therapeutic targeting of ASCT2, a glutamine transporter that plays a major role in glutamine uptake in cancer cells, is challenging because ASCT2 also has a biological role in normal tissues. In this study, we report our novel finding that ASCT2 is physically associated in a molecular complex with epidermal growth factor receptor (EGFR), which is often overexpressed in human head and neck squamous cell carcinoma (HNSCC). Furthermore, we found that ASCT2 can be co-targeted by cetuximab, an EGFR antibody approved for treating metastatic HNSCC. We demonstrated that cetuximab downregulated ASCT2 in an EGFR expression-dependent manner via cetuximab-mediated EGFR endocytosis. Downregulation of ASCT2 by cetuximab led to decreased intracellular uptake of glutamine and subsequently a decreased glutathione level. Cetuximab thereby sensitized HNSCC cells to reactive oxygen species (ROS)-induced apoptosis and, importantly, it is independent of effective inhibition of EGFR downstream signaling by cetuximab. In contrast, knockdown of EGFR by siRNA or inhibition of EGFR kinase with gefitinib, an EGFR kinase inhibitor, failed to sensitize HNSCC cells to ROS-induced apoptosis. Our findings support a novel therapeutic strategy for EGFR-overexpressing and cetuximab-resistant cancers by combining cetuximab with an oxidative therapy.

Resistance of Nonmelanoma Skin Cancer to Nonsurgical Treatments. Part II: Photodynamic Therapy, Vismodegib, Cetuximab, Intralesional Methotrexate, and Radiotherapy

A wide range of treatments is now available for nonmelanoma skin cancer, including 5-fluorouracil, ingenol mebutate, imiquimod, diclofenac, photodynamic therapy, methotrexate, cetuximab, vismodegib, and radiotherapy. All are associated with high clinical and histologic response rates. However, some tumors do not respond due to resistance, which may be primary or acquired. Study of the resistance processes is a broad area of research that aims to increase our understanding of the nature of each tumor and the biologic features that make it resistant, as well as to facilitate the design of new therapies directed against these tumors. In this second article, having covered the topical treatments of nonmelanoma skin cancer, we review resistance to other nonsurgical treatments, such as monoclonal antibodies against basal and squamous cell carcinomas, intralesional chemotherapy, photodynamic therapy, and radiotherapy.

CD70 Expression and Its Correlation with Clinicopathological Variables in Squamous Cell Carcinoma of the Head and Neck

OBJECTIVE

Over the last decade, efforts have been made to get a better understanding of the tumor microenvironment and the role of the immune system in it. New insights into the CD27/CD70 signaling pathway point towards a role in tumor immunology, making CD70 an attractive target for immunotherapy. Here, we evaluate CD70 expression in squamous cell carcinoma of the head and neck (SCCHN).

METHODS

CD70 immunohistochemistry was retrospectively performed on 95 tumor samples. Tumoral CD70 expression was scored and correlated with clinicopathological variables and overall survival (OS).

RESULTS

CD70 expression in tumor cells was observed in 66 samples (69%) and was strongly associated with tumor differentiation grade (p < 0.001). CD70 expression was also observed in tumor-associated fibroblasts and endothelial cells. Additionally, the density of tumor-infiltrating lymphocytes correlated with OS (p = 0.042).

CONCLUSION

This study describes the tumoral expression of CD70 in SCCHN. Results highlight the role of CD70 in tumor biology and identify CD70 as a novel therapeutic target. Further research is warranted.

EGFR regulates the development and microarchitecture of intratumoral angiogenic vasculature capable of sustaining cancer cell intravasation

Many malignant characteristics of cancer cells are regulated through pathways induced by the tyrosine kinase activity of the epidermal growth factor receptor (EGFR). Herein, we show that besides directly affecting the biology of cancer cells per se, EGFR also regulates the primary tumor microenvironment. Specifically, our findings demonstrate that both the expression and signaling activity of EGFR are required for the induction of a distinct intratumoral vasculature capable of sustaining tumor cell intravasation, a critical rate-limiting step in the metastatic cascade. An intravasation-sustaining mode of intratumoral angiogenic vessels depends on high levels of tumor cell EGFR and the interplay between EGFR-regulated production of interleukin 8 by tumor cells, interleukin-8–induced influx of tumor-infiltrating neutrophils delivering their unique matrix metalloproteinase-9, and neutrophil matrix metalloproteinase-9–dependent release of the vascular permeability and endothelial growth factor, VEGF. Our data indicate that through VEGF-mediated disruption of endothelial layer integrity and increase of intratumoral vasculature permeability, EGFR activity significantly facilitates active intravasation of cancer cells. Therefore, this study unraveled an important but overlooked function of EGFR in cancer, namely, its ability to create an intravasation-sustaining microenvironment within the developing primary tumor by orchestrating several interrelated processes required for the initial steps of cancer metastasis through vascular routes. Our findings also suggest that EGFR-targeted therapies might be more effective when implemented in cancer patients with early-staged primary tumors containing a VEGF-dependent angiogenic vasculature. Accordingly, early EGFR inhibition combined with various anti-VEGF approaches could synergistically suppress tumor cell intravasation through inhibiting the highly permeable angiogenic vasculature induced by EGFR-overexpressing aggressive cancer cells.

Gli1-Mediated Regulation of Sox2 Facilitates Self-Renewal of Stem-Like Cells and Confers Resistance to EGFR Inhibitors in Non-Small Cell Lung Cancer

Non–small cell lung cancer (NSCLC) patients have very low survival rates because the current therapeutic strategies are not fully effective. Although EGFR tyrosine kinase inhibitors are effective for NSCLC patients harboring EGFR mutations, patients invariably develop resistance to these agents. Alterations in multiple signaling cascades have been associated with the development of resistance to EGFR inhibitors. Sonic Hedgehog and associated Gli transcription factors play a major role in embryonic development and have recently been found to be reactivated in NSCLC, and elevated Gli1 levels correlate with poor prognosis. The Hedgehog pathway has been implicated in the functions of cancer stem cells, although the underlying molecular mechanisms are not clear. In this context, we demonstrate that Gli1 is a strong regulator of embryonic stem cell transcription factor Sox2. Depletion of Gli1 or inhibition of the Hedgehog signaling significantly abrogated the self-renewal of stem-like side-population cells from NSCLCs as well as vascular mimicry of such cells. Gli1 was found to transcriptionally regulate Sox2 through its promoter region, and Gli1 could be detected on the Sox2 promoter. Inhibition of Hedgehog signaling appeared to work cooperatively with EGFR inhibitors in markedly reducing the viability of NSCLC cells as well as the self-renewal of stem-like cells. Thus, our study demonstrates a cooperative functioning of the EGFR signaling and Hedgehog pathways in governing the stem-like functions of NSCLC cancer stem cells and presents a novel therapeutic strategy to combat NSCLC harboring EGFR mutations.

Role of Reactive Oxygen Species in the Abrogation of Oxaliplatin Activity by Cetuximab in Colorectal Cancer

BACKGROUND

The antibody cetuximab, targeting epidermal growth factor receptor (EGFR), is used to treat metastatic colorectal cancer (mCRC). Clinical trials suggest reduced benefit from the combination of cetuximab with oxaliplatin. The aim of this study was to investigate potential negative interactions between cetuximab and oxaliplatin.

METHODS

Thiazolyl blue tetrazolium bromide (MTT) assay and Calcusyn software were used to characterize drug interactions. Reactive oxygen species (ROS) were measured by flow cytometry and real-time polymerase chain reaction oxidative stress arrays identified genes regulating ROS production. Chromatin immunoprecipitation (ChIP) measured signal transducer and activator of transcription 1 (STAT-1) binding to dual oxidase 2 (DUOX2) promoter. SW48, DLD-1 KRAS wild-type cell lines and DLD-1 xenograft models exposed to cetuximab, oxaliplatin, or oxaliplatin + cetuximab (control [saline]; n = 3 mice per treatment group) were used. Statistical tests were two-sided.

RESULTS

Cetuximab and oxaliplatin exhibited antagonistic effects on cellular proliferation and apoptosis (caspase 3/7 activity reduced by 1.4-fold, 95% confidence interval [CI] = 0.78 to 2.11, P = .003) as opposed to synergistic effects observed with the irinotecan metabolite 7-Ethyl-10-hydroxycamptothecin (SN-38). Although both oxaliplatin and SN-38 produced ROS, only oxaliplatin-mediated apoptosis was ROS dependent. Production of ROS by oxaliplatin was secondary to STAT1-mediated transcriptional upregulation of DUOX2 (3.1-fold, 95% CI = 1.75 to 2.41, P < .001). Inhibition of DUOX2 induction and p38 activation by cetuximab reduced oxaliplatin cytotoxicity.

CONCLUSIONS

Inhibition of STAT1 and DUOX2-mediated ROS generation by cetuximab impairs p38-dependent apoptosis by oxaliplatin in preclinical models and may contribute to reduced efficacy in clinical settings. Understanding the rationale for unexpected trial results will inform improved rationales for combining EGFR inhibitors with chemotherapeutic agents in future therapeutic use.

High EGFR and low p-Akt expression is associated with better outcome after nimotuzumab-containing treatment in esophageal cancer patients: preliminary clinical result and testable hypothesis

The epidermal growth factor receptor (EGFR) is widely overexpressed in esophageal squamous cell carcinoma (ESCC) and it results is associated with a poor prognosis. Identifying the subgroup of ESCC patients who are sensitive to EGFR-targeted therapy is a key point to facilitate its medical use.

We retrospectively analyzed 32 ESCC patients treated with the combination of nimotuzumab (h-R3) and radiotherapy (RT) or chemoradiotherapy (CRT). Expression of EGFR and phosphorylated proteins associated with EGFR signaling pathway, i.e. p-Akt and p-Erk, were assessed with immunohistochemistry (IHC) for all patients. Correlations between these proteins' expression levels and overall survival (OS) were assessed.

High expression of EGFR, p-Akt and p-Erk was detected in 53.1% (17/32), 54.8% (17/31) and 59.4% (19/32) of tumors respectively. No significant differences in OS were found between high EGFR, p-Akt and p-Erk expression groups and their respective counterparts. Of note, significantly better overall survival was observed in patients with coexistence of high EGFR expression and low p-Akt expression (p = 0.030).

Our data allowed us to put forward a hypothesis that high EGFR and low p-Akt expression may predict a clinical benefit of EGFR antagonists such as nimotuzumab combined with RT or CRT. This can be discussed in the terms of oncogene addiction and synthetic lethality concepts. This hypothesis can be further tested in larger groups of patients.

ErbB-3 activation by NRG-1β sustains growth and promotes vemurafenib resistance in BRAF-V600E colon cancer stem cells (CSCs)

Approximately 5-10% of metastatic colorectal cancers harbor a BRAF-V600E mutation, which is correlated with resistance to EGFR-targeted therapies and worse clinical outcome. Vice versa, targeted inhibition of BRAF-V600E with the selective inhibitor PLX 4032 (Vemurafenib) is severely limited due to feedback re-activation of EGFR in these tumors. Mounting evidence indicates that upregulation of the ErbB-3 signaling axis may occur in response to several targeted therapeutics, including Vemurafenib, and NRG-1β-dependent re-activation of the PI3K/AKT survival pathway has been associated with therapy resistance.

Here we show that colon CSCs express, next to EGFR and ErbB-2, also significant amounts of ErbB-3 on their membrane. This expression is functional as NRG-1β strongly induces AKT/PKB and ERK phosphorylation, cell proliferation, clonogenic growth and promotes resistance to Vemurafenib in BRAF-V600E mutant colon CSCs. This resistance was completely dependent on ErbB-3 expression, as evidenced by knockdown of ErbB-3. More importantly, resistance could be alleviated with therapeutic antibody blocking ErbB-3 activation, which impaired NRG-1β-driven AKT/PKB and ERK activation, clonogenic growth in vitro and tumor growth in xenograft models. In conclusion, our findings suggest that targeting ErbB-3 receptors could represent an effective therapeutic approach in BRAF-V600E mutant colon cancer.

Emerging role of mTOR in the response to cancer therapeutics

The movement toward precision medicine with targeted therapeutics for cancer treatment has been hindered by both innate and acquired resistance. Understanding the molecular wiring and plasticity of oncogenic signaling networks is essential to the development of therapeutic strategies to avoid or overcome resistance. The mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) represents a highly integrated signaling node that is dysregulated in the majority of human cancers. Several studies have revealed that sustained mTORC1 inhibition is essential to avoid resistance to targeted therapeutics against the driving oncogenic pathway in a given cancer. Here we discuss the role of mTORC1 in dictating the response of tumors to targeted therapeutics and review recent examples from lung cancer, breast cancer, and melanoma.

Cell-free DNA as a novel marker in cancer therapy

Advances in next-generation sequencing have provided new insights and new therapeutic options for patients with cancer. However, assessment of genomic aberrations, which is required for precision medicine, has been challenging because of the difficulties in capturing intratumoral heterogeneity and in real-time assessment of tumors. Recent advances in technology have enabled detection and analysis of cell-free DNA in cancer patients, which provides real-time assessment of tumor evolution. Here, we review the recent advances in our understanding of the clinical utility of cell-free DNA and the future directions for its use in cancer management.

Treatment of chronic myelogenous leukemia as a paradigm for solid tumors: how targeted agents in newly diagnosed disease transformed outcomes

Although chronic myelogenous leukemia (CML) is rare, with approximately 5000 new cases in the United States annually, it may be the poster child for the future of oncology. Imatinib mesylate, a selective Bcr-Abl tyrosine kinase inhibitor (TKI), transformed the course of CML from a rapidly fatal disease (median survival, 3 to 6 years) to a functionally curable, indolent disease with an estimated median survival of more than 25 years. This transformation can be attributed to several key factors: the identification of a causal and actionable molecular aberration-BCR-ABL; the development of a potent and selective Bcr-Abl TKI-imatinib; and, importantly the application of imatinib in the earliest phase of CML. In contrast, imatinib, if used in CML blastic phase, improves median survival to only about 1 year. Similar to CML blastic phase, metastatic solid malignancies have undergone genetic evolution, and their molecular aberrations are complex. As a result, resistance is common and eradication is difficult. The key to the dramatic improvement in the survival of patients with CML involved using imatinib in newly diagnosed disease, before blastic transformation. We hypothesize that metastatic solid tumors are analogous to CML blastic phase, and that to achieve improvements in solid tumor outcomes similar to those seen in CML, application of targeted agents to newly diagnosed disease may be required to prevent disease transformation (i.e., metastases). Targeting driver mutations at the time of diagnosis may be critical to the goal of markedly changing the outlook for patients with cancer.

Tyrosine dephosphorylation enhances the therapeutic target activity of epidermal growth factor receptor (EGFR) by disrupting its interaction with estrogen receptor (ER)

Protein-protein interactions can increase or decrease its therapeutic target activity and the determining factors involved, however, are largely unknown. Here, we report that tyrosine-dephosphorylation of epidermal growth factor receptor (EGFR) increases its therapeutic target activity by disrupting its interaction with estrogen receptor (ER). Protein tyrosine phosphatase H1 (PTPH1) dephosphorylates the tyrosine kinase EGFR, disrupts its interaction with the nuclear receptor ER, and increases breast cancer sensitivity to small molecule tyrosine kinase inhibitors (TKIs). These effects require PTPH1 catalytic activity and its interaction with EGFR, suggesting that the phosphatase may increase the sensitivity by dephosphorylating EGFR leading to its dissociation with ER. Consistent with this notion, a nuclear-localization defective ER has a higher EGFR-binding activity and confers the resistance to TKI-induced growth inhibition. Additional analysis show that PTPH1 stabilizes EGFR, stimulates the membranous EGFR accumulation, and enhances the growth-inhibitory activity of a combination therapy of TKIs with an anti-estrogen. Since EGFR and ER both are substrates for PTPH1 in vitro and in intact cells, these results indicate that an inhibitory EGFR-ER protein complex can be switched off through a competitive enzyme-substrate binding. Our results would have important implications for the treatment of breast cancer with targeted therapeutics.

Computer-aided design, synthesis, and biological evaluation of new indole-2-carboxamide derivatives as PI3Kα/EGFR inhibitors

Structure-based drug design and molecular modeling were employed to identify a new series of indole-2-carboxamides as potential anticancer agents. These compounds were synthesized and characterized with the aid of several spectroscopic techniques, such as FT-IR, NMR, and mass spectrometry as well as by elemental analysis. Molecular docking studies confirmed that the newly synthesized compounds accommodate PI3Kα and EGFR kinase catalytic sites and form H-bonding with the key binding residues. The antitumor activity of these new compounds against an array of cancer cell lines (human colon carcinoma (HCT116), leukemia (K562), and breast cancer (MDA231) was evaluated. Results revealed that these compounds were selective against the kinase domain, and none of them showed any inhibitory activity against K562. In addition, results showed that compound 13 exhibited high potency in HCT116 and MDA231 with IC50 values of 19 and 15μM, respectively. Our findings recommend that further optimization of this series would be beneficial for colon and breast cancer treatment.