Responses of human colorectal tumor cells to treatment with the anti-epidermal growth factor receptor monoclonal antibody ICR62 used alone and in combination with the EGFR tyrosine kinase inhibitor gefitinib

Novel 2-(5-Aryl-4,5-Dihydropyrazol-1-yl)thiazol-4-One as EGFR Inhibitors: Synthesis, Biological Assessment and Molecular Docking Insights

Introduction

Epidermal growth factor receptor (EGFR) regulates several cell functions which include cell growth, survival, multiplication, differentiation, and apoptosis. Currently, EGFR kinase inhibitors are of increasing interest as promising targeted antitumor therapeutic agents.

Methods

Different thiazolyl-pyrazoline derivatives (7a-o) were synthesized and were first tested for anti-proliferative effect towards the A549 lung cancer cell line and the T-47D breast cancer cell line in MTT assay. Thereafter, thiazolyl-pyrazolines (7b, 7g, 7l, and 7m) were subsequently evaluated for their PK inhibition for EGFR. Moreover, representative promising derivatives (7g and 7m) in cytotoxic and PK inhibition assays were tested to investigate their impact on the apoptosis and cell cycle phases in T-47D cells in order to explore more insights into the antitumor actions of the target thiazolyl-pyrazolines. Furthermore, docking studies were accomplished to evaluate the patterns of binding of thiazolyl-pyrazolines 7b, 7g, 7l, and 7m in the EGFR active pocket (PDB ID: 1M17).

Results

Testing the thiazolyl pyrazoline compounds 7a-o on A549 and T-47D cell lines showed IC₅₀ arrays between 3.92 and 89.03 µM, and between 0.75 and 77.10 µM, respectively. Also, the tested thiazolyl-pyrazolines (7b, 7g, 7l, and 7m) demonstrated significant sub-micromolar EGFR inhibitory actions with IC₅₀ values 83, 262, 171 and 305 nM, respectively, in comparison to erlotinib (IC₅₀ =57 nM).

Discussion

Generally, it was observed that the tested thiazolyl pyrazolines showed more potent antiproliferative activity toward breast cancer cells T-47D than toward lung cancer cell lines A549. In particular, thiazolyl pyrazolines 7g and 7m showed the best activity against A549 cells (IC₅₀ = 3.92 and 6.53 µM) and T-47D cells (IC₅₀ = 0.88 and 0.75 µM). Compounds 7g and 7m provoked a sub-G1 phase arrest and cell apoptosis which are in agreement with the expected outcome of EGFR inhibition. Finally, the molecular docking of 7g and 7m in the active site of EGFR revealed a common binding pattern similar to that of erlotinib which involves the accommodation of the 1,3 thiazol-4-one ring and pyrazoline ring of target compounds in the binding region of erlotinib’s quinazoline ring and anilino moiety.

Synergistic activity of agents targeting growth factor receptors, CDKs and downstream signaling molecules in a panel of pancreatic cancer cell lines and the identification of antagonistic combinations: Implications for future clinical trials in pancreatic cancer

Pancreatic cancer is one of the most aggressive, heterogeneous and fatal type of human cancers for which more effective therapeutic agents are urgently needed. Here, we investigated the sensitivity of a panel of seven human pancreatic cancer cell lines (HPCCLs) to treatment with various tyrosine kinase inhibitors (TKIs), cyclin-dependent kinase (CDK) inhibitors, an inhibitor of STAT3 stattic, and a cytotoxic agent gemcitabine both as single agents and in combination. The membranous expression of various receptors and the effect of selected agents on cell cycle distribution, cell signaling pathways and migration was determined using flow cytometry, western blot analysis and scratch wound healing assays, respectively. While the expression of both HER-3 and HER-4 was low or negative, the expression of EGFR and HER2 was high or intermediate in all HPCCLs. Of all the agents examined, the CDK1/2/5/9 inhibitor, dinacicilib, was the most potent agent which inhibited the proliferation of all seven HPCCLs with IC₅₀ values of ≤10 nM, followed by SRC targeting TKI dasatinib (IC₅₀ of ≤258 nM), gemcitabine (IC₅₀ of ≤330 nM), stattic (IC₅₀ of ≤2 µM) and the irreversible pan-HER TKI afatinib (IC₅₀ of ≤2.95 µM). Treatment with afatinib and dasatinib inhibited the ligand-induced phosphorylation of EGFR and SRC respectively. Statistically significant associations were found between HER2 expression and response to treatment with the ALK/IGF-IR/InsR inhibitor ceritinib and fibroblast growth factor receptor (FGFR)1/2/3 inhibitor AZD4547, HER3 and IGF-IR expression and their response to treatment with TKIs targeting HER family members (erlotinib and afatinib), and c-MET and ALK7 expression and their response to treatment with stattic. Interestingly, treatment with a combination of afatinib with dasatinib and gemcitabine with dasatinib resulted in synergistic tumor growth inhibition in all HPCCLs examined. In contrast, the combination of afatinib with dinaciclib was found to be antagonistic. Finally, the treatment with afatinib, dasatinib and dinaciclib strongly inhibited the migration of all HPCCLs examined. In conclusion, the CDK1/2/5/9 inhibitor dinaciclib, irreversible pan-HER TKI afatinib and SRC targeting TKI dasatinib were most effective at inhibiting the proliferation and migration of HPCCLs and the combination of afatinib with dasatinib and gemcitabine with dasatinib led to synergistic tumor growth inhibition in all HPCCLs examined. Our results support further investigation on the therapeutic potential of these combinations in future clinical trials in pancreatic cancer.

Co-expression and prognostic significance of putative CSC markers CD44, CD133, wild-type EGFR and EGFRvIII in metastatic colorectal cancer

The presence of colorectal cancer stem cells (CSCs) have been associated with tumour initiation and resistance to therapy. This study investigated the co-expression and prognostic significance of the CSCs biomarkers CD44 and CD133 with wild-type EGFR (wtEGFR) and EGFRvIII in colorectal cancer (CRC). The expression of these biomarkers were determined in tumours from 70 patients with metastatic CRC by immunohistochemistry, and in a panel of human CRC cell lines, and their variants with acquired-resistance to EGFR inhibitors, by flow cytometry. The expression of CD44, CD133, wtEGFR and EGFRvIII were present in 17%, 23%, 26% and 13% of cases and the co-expression of CD44/CD133 with wtEGFR and EGFRvIII were present in 9% and 3% of the cases respectively. Only co-expression of CSCs/EGFRvIII (P = 0.037), and amphiregulin (P = 0.017) were associated with worse overall survival. Interestingly, disease-free survival was improved in BTC expressing patients (P = 0.025). In vitro CD133 expression and its co-expression with CD44 were associated with primary-resistance to irinotecan and acquired-resistance to anti-EGFR inhibitors respectively. Our results suggest co-expression of CSCs and EGFRvIII could be potential biomarkers of worse overall survival and resistance to therapy in patients with mCRC and warrants further validation in a larger cohort.

Membrane expression of thymidine kinase 1 and potential clinical relevance in lung, breast, and colorectal malignancies

Background

Lung, breast, and colorectal malignancies are the leading cause of cancer-related deaths in the world causing over 2.8 million cancer-related deaths yearly. Despite efforts to improve prevention methods, early detection, and treatments, survival rates for advanced stage lung, breast, and colon cancer remain low, indicating a critical need to identify cancer-specific biomarkers for early detection and treatment. Thymidine kinase 1 (TK1) is a nucleotide salvage pathway enzyme involved in cellular proliferation and considered an important tumor proliferation biomarker in the serum. In this study, we further characterized TK1’s potential as a tumor biomarker and immunotherapeutic target and clinical relevance.

Methods

We assessed TK1 surface localization by flow cytometry and confocal microscopy in lung (NCI-H460, A549), breast (MDA-MB-231, MCF7), and colorectal (HT-29, SW620) cancer cell lines. We also isolated cell surface proteins from HT-29 cells and performed a western blot confirming the presence of TK1 on cell membrane protein fractions. To evaluate TK1’s clinical relevance, we compared TK1 expression levels in normal and malignant tissue through flow cytometry and immunohistochemistry. We also analyzed RNA-Seq data from The Cancer Genome Atlas (TCGA) to assess differential expression of the TK1 gene in lung, breast, and colorectal cancer patients.

Results

We found significant expression of TK1 on the surface of NCI-H460, A549, MDA-MB-231, MCF7, and HT-29 cell lines and a strong association between TK1’s localization with the membrane through confocal microscopy and Western blot. We found negligible TK1 surface expression in normal healthy tissue and significantly higher TK1 expression in malignant tissues. Patient data from TCGA revealed that the TK1 gene expression is upregulated in cancer patients compared to normal healthy patients.

Conclusions

Our results show that TK1 localizes on the surface of lung, breast, and colorectal cell lines and is upregulated in malignant tissues and patients compared to healthy tissues and patients. We conclude that TK1 is a potential clinical biomarker for the treatment of lung, breast, and colorectal cancer.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0633-9) contains supplementary material, which is available to authorized users.

Inhibition of pro-HGF activation by SRI31215, a novel approach to block oncogenic HGF/MET signaling

The binding of hepatocyte growth factor (HGF) to its receptor MET activates a signaling cascade that promotes cell survival, proliferation, cell scattering, migration and invasion of malignant cells. HGF is secreted by cancer cells or by tumor-associated fibroblasts as pro-HGF, an inactive precursor. A key step in the regulation of HGF/MET signaling is proteolytic processing of pro-HGF to its active form by one of the three serine proteases, matriptase, hepsin or HGF activator (HGFA).We developed SRI 31215, a small molecule that acts as a triplex inhibitor of matriptase, hepsin and HGFA and mimics the activity of HAI-1/2, endogenous inhibitors of HGF activation. We demonstrated that SRI 31215 inhibits fibroblast-induced MET activation, epithelial-mesenchymal transition and migration of cancer cells. SRI 31215 overcomes primary resistance to cetuximab and gefitinib in HGF-producing colon cancer cells and prevents fibroblast-mediated resistance to EGFR inhibitors. Thus, SRI 31215 blocks signaling between cancer cells and fibroblasts and inhibits the tumor-promoting activity of cancer-associated fibroblasts.Aberrant HGF/MET signaling supports cell survival, proliferation, angiogenesis, invasion and metastatic spread of cancer cells, establishing HGF and MET as valid therapeutic targets. Our data demonstrate that inhibitors of HGF activation, such as SRI 31215, merit investigation as potential therapeutics in tumors that are addicted to HGF/MET signaling. The findings reported here also indicate that inhibitors of HGF activation overcome primary and acquired resistance to anti-EGFR therapy, providing a rationale for concurrent inhibition of EGFR and HGF to prevent therapeutic resistance and to improve the outcome of cancer patients.

Impact of the putative cancer stem cell markers and growth factor receptor expression on the sensitivity of ovarian cancer cells to treatment with various forms of small molecule tyrosine kinase inhibitors and cytotoxic drugs

Increased expression and activation of human epidermal growth factor receptor (EGFR) and HER-2 have been reported in numerous cancers. The aim of this study was to determine the sensitivity of a large panel of human ovarian cancer cell lines (OCCLs) to treatment with various forms of small molecule tyrosine kinase inhibitors (TKIs) and cytotoxic drugs. The aim was to see if there was any association between the protein expression of various biomarkers including three putative ovarian cancer stem cell (CSC) markers (CD24, CD44, CD117/c-Kit), P-glycoprotein (P-gp), and HER family members and response to treatment with these agents. The sensitivity of 10 ovarian tumour cell lines to the treatment with various forms of HER TKIs (gefitinib, erlotinib, lapatinib, sapitinib, afatinib, canertinib, neratinib), as well as other TKIs (dasatinib, imatinib, NVP-AEW541, crizotinib) and cytotoxic agents (paclitaxel, cisplatin and doxorubicin), as single agents or in combination, was determined by SRB assay. The effect on these agents on the cell cycle distribution, and downstream signaling molecules and tumour migration were determined using flow cytometry, western blotting, and the IncuCyte Clear View cell migration assay respectively. Of the HER inhibitors, the irreversible pan-TKIs (canertinib, neratinib and afatinib) were the most effective TKIs for inhibiting the growth of all ovarian cancer cells, and for blocking the phosphorylation of EGFR, HER-2, AKT and MAPK in SKOV3 cells. Interestingly, while the majority of cancer cells were highly sensitive to treatment with dasatinib, they were relatively resistant to treatment with imatinib (i.e., IC50 >10 µM). Of the cytotoxic agents, paclitaxel was the most effective for inhibiting the growth of OCCLs, and of various combinations of these drugs, only treatment with a combination of NVP-AEW541 and paclitaxel produced a synergistic or additive anti-proliferative effect in all three cell lines examined (i.e., SKOV3, Caov3, ES2). Finally, of the TKIs, only treatment with afatinib, neratinib and dasatinib were able to reduce the migration of HER-2 overexpressing SKOV3 cells. We did not find any significant association between the expression of putative ovarian CSC marker, HER family members, c-MET, ALK, and IGF-IR and the response to the irreversible HER TKIs. Our results support the need for further investigations of the therapeutic potential of these irreversible HER family blockers in ovarian cancer, and the therapeutic potential of dasatinib when used in combination with the inhibitors of the HER family members in ovarian cancer.

Preclinical and clinical studies on afatinib in monotherapy and in combination regimens: Potential impact in colorectal cancer

Targeting the epidermal growth factor receptor (EGFR) with monoclonal antibodies (mAbs) or tyrosine kinase inhibitors (TKI) has been an interesting therapeutic strategy because aberrant activation of this receptor plays an important role in the tumorgenesis of many cancer types, including colorectal cancer (CRC). After the initial promising results of EGFR-targeted therapies, therapeutic resistance is a major clinical problem. In order to overcome resistance to these EGFR-targeted therapies, new treatment options are necessary. In contrast to first generation EGFR inhibitors, afatinib (BIBW2992) is a second-generation irreversible ErbB family blocker that inhibits EGFR as well as HER2 and HER4. Consequently, treatment with afatinib may result in a distinct and more pronounced therapeutic benefit. Preclinical studies have reported promising results for afatinib in monotherapy as well as in combination with other drugs in CRC model systems. Furthermore, clinical studies examining afatinib as single agent and in combination therapy demonstrated manageable safety profile. Nevertheless, only limited antitumor activity has been observed in CRC patients. Although several combination treatments with afatinib have already been investigated, no optimal combination has been identified for CRC patients yet. As molecular tumor characteristics have gained increased importance in the choice of treatment, additional studies with biomarker-driven patient recruitment are required to further explore afatinib efficacy in CRC.

Acquired resistance of pancreatic cancer cells to treatment with gemcitabine and HER-inhibitors is accompanied by increased sensitivity to STAT3 inhibition

Drug-resistance is a major contributing factor for the poor prognosis in patients with pancreatic cancer. We have shown previously that the irreversible ErbB family blocker afatinib, is more effective than the reversible EGFR tyrosine kinase inhibitor erlotinib in inhibiting the growth of human pancreatic cancer cells. The aim of this study was to develop human pancreatic cancer cell (BxPc3) variants with acquired resistance to treatment with gemcitabine, afatinib, or erlotinib, and to investigate the molecular changes that accompany the acquisition of a drug-resistant phenotype. We also investigated the therapeutic potential of various agents in the treatment of such drug-resistant variants. Three variant forms of BxPc3 cells with acquired resistance to gemcitabine (BxPc3GEM), afatinib (BxPc3AFR) or erlotinib (BxPc3OSIR) were developed following treatment with increasing doses of such drugs. The expression level, mutational and phosphorylation status of various growth factor receptors and downstream cell signaling molecules were determined by FACS, human phopsho-RTK array, and western blot analysis while the sulforhodamine B assay was used for determining the effect of various agents on the growth of such tumours. We found that all three BxPc3 variants with acquired resistance to gemcitabine (BxPc3GEM), afatinib (BxPc3AFR) or erlotinib (BxPc3OSIR) also become less sensitive to treatment with the two other agents. Acquisition of resistance to these agents was accompanied by upregulation of p-c-MET, p-STAT3, CD44, increased autocrine production of EGFR ligand amphiregulin and differential activation status of EGFR tyrosine residues as well as downregulation of total and p-SRC. Of all therapeutic interventions examined, including the addition of an anti-EGFR antibody ICR62, an anti-CD44 monoclonal antibody, and of STAT3 or c-MET inhibitors, only treatment with the STAT3 inhibitor Stattic produced a higher growth inhibitory effect in all three drug-resistant variants. In addition, treatment with a combination of afatinib with either c-MET inhibitor Crizotinib or Stattic resulted in an additive or synergistic growth inhibition in all three variants. Our results suggest that activation of STAT3 may play an important role in the acquisition of resistance to gemcitabine and HER inhibitors in pancreatic cancer and warrant further studies on the therapeutic potential of STAT3 inhibitors in such a setting.

Acquired resistance to anti-EGFR mAb ICR62 in cancer cells is accompanied by an increased EGFR expression, HER-2/HER-3 signalling and sensitivity to pan HER blockers

BACKGROUND

The human epidermal growth factor receptor (EGFR) is an important target for cancer treatment. Currently, only the EGFR antibodies cetuximab and panitumumab are approved for the treatment of patients with colorectal cancer. However, a major clinical challenge is a short-term response owing to development of acquired resistance during the course of the treatment.

METHODS

In this study, we investigated the molecular mechanisms underlying development of acquired resistance in DiFi colorectal cancer cells to the anti-EGFR mAb ICR62 (termed DiFi62) and to the small molecule tyrosine kinase inhibitor (TKI) gefitinib (termed DiFiG) using a range of techniques.

RESULTS

Compared with the findings from parental DiFi and DiFiG cells, development of acquired resistance to anti-EGFR mAb ICR62 in DiFi62 cells was accompanied by an increase in cell surface EGFR and increased phosphorylation of HER-2 and HER-3. Interestingly, DiFi62 cells also acquired resistance to treatment with anti-EGFR mAbs cetuximab and ICR61, which bind to other distinct epitopes on the extracellular domain of EGFR, but these cells remained equally sensitive as the parental cells to treatment with pan-HER inhibitors such as afatinib.

CONCLUSIONS

Our results provide a novel mechanistic insight into the development of acquired resistance to EGFR antibody-based therapy in colorectal cancer cells and justify further investigations on the therapeutic benefits of pan-HER family inhibitors in the treatment of colorectal cancer patients once acquired resistance to EGFR antibody-based therapy is developed.

Role of EGFR expression levels in the regulation of integrin function by EGF

Activation of β1 integrins in dormant tumor cells has been linked to metastatic progression, suggesting that therapies designed to maintain β1 integrins in an inactive state may be useful in the prevention of metastatic disease. Our earlier studies have demonstrated that EGF regulates the activation state of the α5β1 integrin in EGFR overexpressing tumor cells through an ERK/p90RSK signaling pathway. Activation of this pathway by EGF resulted in the filamin A dependent inactivation of the α5β1 integrin receptor for fibronectin. The current study was designed to address the role of EGFR overexpression in the regulation of α5β1 integrin activation state by EGF. Lentiviral knockdown of EGFR coupled with limited dilution cloning was used to develop A431 squamous carcinoma cell lines expressing high, moderate, and low levels of EGFR. Inactivation of α5β1 integrin by EGF was shown to correlate with both the level of EGFR expression and the extent of p90RSK phosphorylation, but not with the level of ERK phosphorylation, suggesting that high levels of EGFR promote α5β1 integrin inactivation through sustained activation of p90RSK. Treatment of cells with EGFR kinase inhibitor resulted in a reactivation of the integrin which could be reversed with the phosphatase inhibitor, menadione. Taken together, these findings indicate that p90RSK may function to maintain dormancy in tumor cells expressing high levels of EGFR. © 2015 Wiley Periodicals, Inc.

Epidermal growth factor mediated healing in stem cell-derived vocal fold mucosa

BACKGROUND

The goal of vocal fold wound healing is the reconstitution of functional tissue, including a structurally and functionally intact epithelium. Mechanisms underlying reepithelialization in vocal folds are not known, although it is suspected that healing involves the interplay between several growth factors. We used a three-dimensional human embryonic stem cell-derived model of vocal fold mucosa to examine the effects of one growth factor, exogenous epidermal growth factor (EGF), on wound healing.

MATERIALS AND METHODS

A scratch wound was created in the in vitro model. Rate of wound healing, epidermal growth factor receptor (EGFR) activation, and cell proliferation after injury were analyzed with and without application of both exogenous EGF and an EGFR inhibitor, gefitinib.

RESULTS

Wound repair after injury was significantly hastened by application of exogenous EGF (13.3 μm/h, ± 2.63) compared with absence of exogenous EGF (7.1 μm/h ± 2.84), but inhibited with concurrent addition of Gefitinib (5.2 μm/h, ± 2.23), indicating that EGF mediates wound healing in an EGFR-dependent manner. Immunohistochemistry revealed that EGFR activation occurred only in the presence of exogenous EGF. Although not statistically significant, increased density of Ki67 staining in the epithelium adjacent to the scratch wound was observed after treatment with EGF, suggesting a tendency for exogenous EGF to increase epithelial cell proliferation.

CONCLUSIONS

Exogenous EGF increases the rate of wound healing in an EGFR-dependent manner in a three-dimensional stem cell-derived model of vocal fold mucosa. This model of wound healing can be used to gain insight into the mechanisms that regulate vocal fold epithelial repair after injury.

Erbin interacts with c-Cbl and promotes tumourigenesis and tumour growth in colorectal cancer by preventing c-Cbl-mediated ubiquitination and down-regulation of EGFR

The epidermal growth factor receptor (EGFR) is implicated in many types of cancer, including colorectal cancer (CRC), and has become one of the most common candidates for targeted therapy. Here, we found that Erbin, a member of the leucine-rich repeat and PDZ domain (LAP) family, plays a key role in EGFR signalling. Erbin inhibited EGFR ubiquitination and stabilized the EGFR protein by interacting with c-Cbl. Moreover, the PDZ domain of Erbin was critical for the interaction between Erbin and c-Cbl and EGFR ubiquitination. Interestingly, Erbin expression was elevated in tumour samples from CRC patients, increased in advanced clinical stage disease and correlated with EGFR expression. In vivo studies using mouse xenograft models of CRC showed that Erbin promotes tumour growth, and that the effects of Erbin on tumour growth are mainly related to the regulatory effects of Erbin on EGFR. The azoxymethane (AOM)-induced colon carcinogenesis model in Erbin(ΔC) (/) (ΔC) mice, with the PDZ domain of Erbin deleted, demonstrated that the PDZ domain of Erbin and its regulation of EGFR signalling are necessary for the tumourigenesis and tumour growth of CRC. We found that Erbin promotes tumourigenesis and tumour growth in CRC by stabilizing EGFR. Our study sheds light on developing Erbin, especially its PDZ domain, as a potential target for CRC treatment.

Co-expression of HER family members in patients with Dukes' C and D colon cancer and their impacts on patient prognosis and survival

The human epidermal growth factor receptor (EGFR) is an important therapeutic target in patients with metastatic colorectal cancer and anti-EGFR antibodies cetuximab and panitumumab have been approved for the treatment of such patients. Despite these advances, the duration of response in some patients can be limited. Since, EGFR is capable of forming heterodimers with the other members of the HER (Human epidermal receptor) family, it is important to investigate the co-expression and prognostic significance of all members of the HER family in colorectal cancer patients. The expression of the HER family members were determined in tumour specimens from 86 patients with Dukes’ C and D (metastatic) colon cancer using immunohistochemistry. Sections were scored by the percentage of positive tumour cells and intensity of staining. Their associations with clinicopathological parameters, and overall survival and disease free survival were evaluated using univariate and multivariate analysis. Overall, 43%, 77%, 52% and 92% of the cases were EGFR, HER-2, HER-3 and HER-4 positive respectively. Interestingly, 35%, 24%, 43%, and 18% of the cases had co-expression of EGFR/HER-2, EGFR/HER-3, EGFR/HER-4 and all four members of the HER family respectively. Of these, only the expression of EGFR and co-expression of EGFR/HER-4 were associated with poorer disease-free survival in both univariate and multivariate analysis. Co-expression of all members of the HER family in colon cancer supports the need for further investigations on their predictive value for response to therapy with anti-EGFR mAbs and whether such sub-population of patients may benefit from therapy with the new generation of pan-HER inhibitors.

Predicting response to epidermal growth factor receptor-targeted therapy in colorectal cancer

The discovery over 20 years ago by the Nobel Laureate Stanley Cohen of epidermal growth factor and its receptor, followed by the recognition that this receptor is overexpressed in multiple cancer types, has been of phenomenal significance. From these events the 'Holy Grail' of targeted therapy has looked increasingly realistic. Over the last 5 years this work has come of age with the licensing of multiple agents targeting this important mitogenic pathway in multiple tumor types. However, these agents and the technology behind them, while impressive, have resulted in lower clinical response rates than anticipated. In this review we will focus on the epidermal growth factor receptor-targeted therapies in colorectal cancer, why our expectations from these therapies have not yet been fulfilled and how we may predict those cancers that are likely to respond or be resistant to these therapies through a greater appreciation of the intricacy, diversity and dynamism of cellular signaling mechanisms.

Direct and immune mediated antibody targeting of ERBB receptors in a colorectal cancer cell-line panel

A significant proportion of colorectal cancer (CRC) patients are resistant to anti-ERBB1 [avian erythroblastic leukemia viral (v-erb-b) oncogene homolog, receptor for EGF] monoclonal antibodies (Mabs). We evaluated both immune and nonimmune effects of cetuximab (anti-ERBB1 Mab), trastuzumab (anti-ERBB2 Mab), pertuzumab (anti-ERBB2 Mab), and lapatinib (dual ERBB1 and ERBB2 tyrosine kinase inhibitor) in a large well-characterized panel of 64 CRC cell lines to find response predictive tumor characteristics. There was a significant correlation between the direct effects of cetuximab and lapatinib. Both agents were associated (P = 0.0004) with "triple' wild-type status in KRAS, BRAF, and PIK3CA exon 20. Most cell lines were resistant to the direct effects of anti-ERBB2 Mabs, suggesting that the effects of lapatinib might mainly be through ERBB1. Microarray mRNA expression profiles of sensitive and resistant cell lines showed that although ERBB1 receptor or ligand levels did not associate with cetuximab sensitivity, high levels of ERBB2 (P = 0.036) and amphiregulin (P = 0.026) predicted sensitivity to lapatinib. However, higher ERBB1 expression predicted susceptibility to cetuximab-induced antibody-dependent cellular cytotoxicity and occurred independently of KRAS/BRAF/PIK3CA mutations (P = 0.69). Lapatinib may be an effective alternative therapy to cetuximab in triple wild-type tumors. Microarray analysis provides suggestive biomarkers for resistance. ERBB1 levels, independent of mutation status, predict immune killing. Therefore, anti-ERBB1 antibodies may be considered in CRC tumors with higher ERBB1 expression and favorable FcγR polymorphisms.

Anti-tumour activity of afatinib, an irreversible ErbB family blocker, in human pancreatic tumour cells

BACKGROUND

The combination of the reversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) erlotinib with gemcitabine obtained FDA approval for treating patients with pancreatic cancer. However, duration of response is often limited and there is currently no reliable predictive marker.

METHODS

We determined the sensitivity of a panel of human pancreatic tumour cell lines to treatment with afatinib, erlotinib, monoclonal antibody (mAb) ICR62, and gemcitabine, using the Sulforhodamine B colorimetric assay. The effect of these agents on cell signalling and cell-cycle distribution was determined by western blot and flow cytometry, respectively.

RESULTS

At 200 nM, ICR62 had no effect on growth of these tumour cells with the exception of BxPC-3 cells. BxPC-3 cells were also sensitive to treatment with afatinib and erlotinib with respective IC(50) values of 11 and 1200 nM. Compared with erlotinib, afatinib was also more effective in inhibiting the growth of the other human pancreatic tumour cell lines and in blocking the EGF-induced phosphorylation of tyrosine, EGFR, MAPK, and AKT. When tested in BxPC-3 xenografts, afatinib induced significant delay in tumour growth.

CONCLUSION

The superiority of afatinib in this study encourages further investigation on the therapeutic potential of afatinib as a single agent or in combination with gemcitabine in pancreatic cancer.

Phosphorylated insulin-like growth factor 1 receptor is implicated in resistance to the cytostatic effect of gefitinib in colorectal cancer cells

INTRODUCTION

The ability of certain cancer cells to maintain signaling via the phosphoinositide-3-kinase/Akt and/or Ras/mitogen-activated protein kinase (MAPK) pathways has been repeatedly involved in resistance to epidermal growth factor receptor (EGFR) inhibition.

DISCUSSION

We investigated the potential mechanisms of the uncoupling of EGFR from its downstream signals in colorectal cancer (CRC) cells. Alternative growth factor receptors and regulation of downstream pathways in different gefitinib-responsive cell lines were determined. Basal insulin-like growth factor receptor-1β (IGFR-1β) phosphorylation was undetectable or present at very low levels in highly gefitinib-responsive cell lines and was present at strikingly high levels in less responsive cell lines. Further analysis of cell lines representing the most sensitive (Lovo), moderately sensitive (HT29), and most resistant (HCT116) strains was treated with an IGFR-1 inhibitor (AG1024), gefitinib, or both, revealing that elevated IGFR-1β phosphorylation can compensate for the loss of EGFR signaling function. Increased insulin-like growth factor II expression induced by gefitinib or heterodimerization of EGFR and IGFR-1β may trigger IGFR-1β signal transduction via activation of Akt and MAPK. In addition, high levels of EGFR and IGFR-1β phosphorylation were detected in CRC tumor tissue. We also showed that gefitinib- and/or AG1024-induced cytostatic effects could be mediated by glycogen synthase kinase-3β (GSK-3β) activation. Our data suggest that the crosstalk between EGFR and IGFR-1β signaling are likely to contribute to resistance of CRC cells to gefitinib and that measurement of GSK-3β activation may present a potential biomarker for evaluating the antitumor efficacy of receptor tyrosine kinase inhibition.

Periadventitial delivery of anti-EGF receptor antibody inhibits neointimal macrophage accumulation after angioplasty in a hypercholesterolaemic rabbit

Monocyte recruitment and their differentiation into macrophages are both early events in native and accelerated atherosclerosis that follows angioplasty. We have investigated the putative functional role of the epidermal growth factor receptor (EGFR) present on rabbit monocytes/macrophages. The impact of periadventitial delivery of an EGFR-specific, blocking monoclonal antibody (ICR62, which inhibits EGF-binding to its receptor) was investigated in a rabbit model of accelerated atherosclerosis induced by a combination of carotid injury and 4 weeks of a 2% cholesterol-diet. Two weeks after the initiation of the diet, a balloon-catheter angioplasty of the left common carotid artery was performed and a collar placed around the injured carotid artery immediately, for the delivery of ICR62 antibody, isotype-matched antibody or saline control. Monocyte/macrophage accumulation, cell proliferation and neointimal thickening were determined 2 weeks after the delivery of the antibodies. The function of the EGFR on rabbit monocytes was also investigated in vitro, using chemotaxis assays. Treatment with ICR62 was associated with a significant reduction in macrophage accumulation and neointimal thickening and a 76% reduction in neointimal area of the vessel wall compared with controls. In vitro ICR62 inhibited macrophage and smooth muscle cell migration towards EGFR ligands including EGF and HB-EGF. These findings suggest that EGFR ligation may be important in the development of early atherosclerotic lesions following balloon-catheter angioplasty, and periadventitial delivery may provide a feasible approach for administration of the inhibitors of EGFR-binding such as ICR62.

Tumor-specific apoptosis caused by deletion of the ERBB3 pseudo-kinase in mouse intestinal epithelium

Pharmacologic blockade of EGFR or the closely related receptor ERBB2 has modest efficacy against colorectal cancers in the clinic. Although the upregulation of ERBB3, a pseudo-kinase member of the EGFR/ERBB family, is known to contribute to EGFR inhibitor resistance in other cancers, its functions in normal and malignant intestinal epithelium have not been defined. We have shown here that the intestinal epithelium of mice with intestine-specific genetic ablation of Erbb3 exhibits no cytological abnormalities but does exhibit loss of expression of ERBB4 and sensitivity to intestinal damage. By contrast, intestine-specific Erbb3 ablation resulted in almost complete absence of intestinal tumors in the ApcMin mouse model of colon cancer. Unlike nontransformed epithelium lacking ERBB3, intestinal tumors lacking ERBB3 had reduced PI3K/AKT signaling, which led to attenuation of tumorigenesis via a tumor-specific increase in caspase-3-mediated apoptosis. Consistent with the mouse data, which suggest that ERBB3-ERBB4 heterodimers contribute to colon cancer survival, experimentally induced loss of ERBB3 in a KRAS mutant human colon cancer cell line was associated with loss of ERBB4 expression, and siRNA knockdown of either ERBB3 or ERBB4 resulted in elevated levels of apoptosis. These results indicate that the ERBB3 pseudo-kinase has essential roles in supporting intestinal tumorigenesis and suggest that ERBB3 may be a promising target for the treatment of colorectal cancers.

Molecular imaging of therapeutic response to epidermal growth factor receptor blockade in colorectal cancer

PURPOSE

To evaluate noninvasive molecular imaging methods as correlative biomarkers of therapeutic efficacy of cetuximab in human colorectal cancer cell line xenografts grown in athymic nude mice. The correlation between molecular imaging and immunohistochemical analysis to quantify epidermal growth factor (EGF) binding, apoptosis, and proliferation was evaluated in treated and untreated tumor-bearing cohorts.

EXPERIMENTAL DESIGN

Optical imaging probes targeting EGF receptor (EGFR) expression (NIR800-EGF) and apoptosis (NIR700-Annexin V) were synthesized and evaluated in vitro and in vivo. Proliferation was assessed by 3'-[18F]fluoro-3'-deoxythymidine ([18F]FLT) positron emission tomography. Assessment of inhibition of EGFR signaling by cetuximab was accomplished by concomitant imaging of NIR800-EGF, NIR700-Annexin V, and [18F]FLT in cetuximab-sensitive (DiFi) and insensitive (HCT-116) human colorectal cancer cell line xenografts. Imaging results were validated by measurement of tumor size and immunohistochemical analysis of total and phosphorylated EGFR, caspase-3, and Ki-67 immediately following in vivo imaging.

RESULTS

NIR800-EGF accumulation in tumors reflected relative EGFR expression and EGFR occupancy by cetuximab. NIR700-Annexin V accumulation correlated with cetuximab-induced apoptosis as assessed by immunohistochemical staining of caspase-3. No significant difference in tumor proliferation was noted between treated and untreated animals by [18F]FLT positron emission tomography or Ki-67 immunohistochemistry.

CONCLUSIONS

Molecular imaging can accurately assess EGF binding, proliferation, and apoptosis in human colorectal cancer xenografts. These imaging approaches may prove useful for serial, noninvasive monitoring of the biological effects of EGFR inhibition in preclinical studies. It is anticipated that these assays can be adapted for clinical use.

Clinical usefulness of EGFR gene copy number as a predictive marker in colorectal cancer patients treated with cetuximab: a fluorescent in situ hybridization study

PURPOSE

To evaluate the usefulness and the pitfalls inherent to the assessment of the epidermal growth factor receptor (EGFR) gene copy number (GCN) by fluorescence in situ hybridization (FISH) for outcome prediction to cetuximab in metastatic colorectal cancer. The value of testing KRAS mutation status, in addition to EGFR GCN, was also explored.

EXPERIMENTAL DESIGN

FISH analysis of 87 metastatic colorectal cancer patients treated with cetuximab was done, recording individual GCN per cell and using different samples per tumor. Performances of published cutoff points and different summaries of EGFR GCN distribution were assessed for response prediction.

RESULTS

In our data set, two published cutoff points performed less well than in their training set, yielding positive predictive values and negative predictive values between 40.0% and 48.3% and between 81.0% and 86.5%, respectively. Among summaries of GCN distribution explored, mean and right-tailed distribution of GCN yielded the highest performances. A mean EGFR GCN > or = 2.83 provided an area under the curve of 0.71. Important heterogeneity of repeated measures of mean EGFR GCN was observed within tumors (intraclass correlation, 0.61; within-class SD, 0.40), leading to potential misclassifications of FISH status in 7 of 18 (38.8%) patients if a cutoff point were used. In multivariable analysis, EGFR GCN testing provided significant information independent of the KRAS status to predict response (P = 0.016) and overall survival (P = 0.005).

CONCLUSIONS

We confirm the association between increased EGFR GCN and outcome after cetuximab. However, because of reproducibility concerns, any decision making based on published cutoff points is not warranted.

Suppression of proHB-EGF carboxy-terminal fragment nuclear translocation: a new molecular target therapy for gastric cancer

PURPOSE

Inactivation of epidermal growth factor (EGF) receptor (EGFR) represents a promising strategy for the development of selective therapies against epithelial cancers and has been extensively studied as a molecular target for cancer therapy. However, little attention has been paid to remnant cell-associated domains created by cleavage of EGFR ligands. The present study focused on recent findings that cleavage of membrane-anchored heparin-binding EGF-like growth factor (proHB-EGF), an EGFR ligand, induces translocation of the carboxyl-terminal fragment (CTF) of HB-EGF from the plasma membrane to the nucleus and regulates cell cycle.

EXPERIMENTAL DESIGN

Two gastric cancer cell lines, MKN28 and NUGC4, were used. KB-R7785, an inhibitor of proHB-EGF shedding, was used to suppress HB-EGF-CTF nuclear translocation with cetuximab, which inhibits EGFR phosphorylation. Cell growth was analyzed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt assay, apoptosis was evaluated by assay of caspase-3 and caspase-7, and cell cycle was investigated by flow cytometry.

RESULTS

Immunofluorescence study confirmed that KB-R7785 inhibited HB-EGF-CTF nuclear translocation under conditions of proHB-EGF shedding induction by 12-O-tetradecanoylphorbol-13-acetate in gastric cancer cells. KB-R7785 inhibited cell growth in a dose-dependent manner and high-dose KB-R7785 induced apoptosis. Moreover, KB-R7785 induced cell cycle arrest and increased sub-G1 DNA content. KB-R7785 suppressed cyclin A and c-Myc expression. All effects of KB-R7785 were reinforced by combination with cetuximab.

CONCLUSIONS

These results suggest that both inhibition of EGFR phosphorylation and inhibition of HB-EGF-CTF nuclear translocation play crucial roles in inhibitory regulation of cancer cell growth. Suppression of HB-EGF-CTF nuclear translocation might offer a new strategy for treating gastric cancer.

Lapatinib resistance in HCT116 cells is mediated by elevated MCL-1 expression and decreased BAK activation and not by ERBB receptor kinase mutation

We have defined some of the mechanisms by which the kinase inhibitor lapatinib kills HCT116 cells. Lapatinib inhibited radiation-induced activation of ERBB1/2, extracellular signal-regulated kinases 1/2, and AKT, and radiosensitized HCT116 cells. Prolonged incubation of HCT116 cells with lapatinib caused cell killing followed by outgrowth of lapatinib-adapted cells. Adapted cells were resistant to serum starvation-induced cell killing and were cross-resistant to multiple therapeutic drugs. Lapatinib was competent to inhibit basal and epidermal growth factor (EGF)-stimulated ERBB1 phosphorylation in adapted cells. Coexpression of dominant-negative ERBB1 and dominant-negative ERBB2 inhibited basal and EGF-stimulated ERBB1 and ERBB2 phosphorylation in parental and adapted cells. However, in neither parental nor adapted cells did expression of dominant-negative ERBB1 and dominant-negative ERBB2 recapitulate the cell death-promoting effects of lapatinib. Adapted cells had increased expression of MCL-1, decreased expression of BAX, and decreased activation of BAX and BAK. Overexpression of BCL-XL protected parental cells from lapatinib toxicity. Knockdown of MCL-1 expression enhanced lapatinib toxicity in adapted cells that was reverted by knockdown of BAK expression. Inhibition of caspase function modestly reduced lapatinib toxicity in parental cells, whereas knockdown of apoptosis-inducing factor expression suppressed lapatinib toxicity. Thus, in HCT116 cells, lapatinib adaptation can be mediated by altered expression of pro- and antiapoptotic proteins that maintain mitochondrial function.

Gefitinib in combination with oxaliplatin and 5-fluorouracil in irinotecan-refractory patients with colorectal cancer: a phase I study of the Arbeits gemeinschaft Internistische Onkologie (AIO)

BACKGROUND

The aim of the study was to establish the recommended dose and to evaluate the safety of gefitinib plus FUFOX regimen in irinotecan-refractory colorectal carcinoma (CRC).

PATIENTS AND METHODS

Patients with advanced CRC progressing on fluoropyrimidine/irinotecan-based chemotherapy and with an ECOG performance level 0-2 were enrolled. Four dose levels with sequential dose escalation of oral gefitinib and FUFOX were tested. Each cycle consisted of 5 weeks with gefitinib given daily to weekly FUFOX x4 to be repeated at day 36.

RESULTS

Eighteen patients were enrolled. No dose-limiting toxicity (DLT) was observed at the dose levels L1-L3. At L4 diarrhea was the major DLT requiring treatment interruption in 3 patients. Other grade 3/4 toxicities were observed with skin rash, paresthesia, anemia, and nausea/vomiting (n = 1 each). Grade 1/2 toxicities consisted of diarrhea (n = 9), mucositis (8), skin rash (10), paresthesia (10), nausea (7) as well as leukopenia (2) and fever (1). Clinical benefit was seen in 11 of 16 evaluable patients (69%): 4 patients showed partial response (25%), 7 stable disease (44%). Median time to progression was 219 days (range 50-387 days).

CONCLUSION

Gefitinib at a dose of 250 mg daily in combination with weekly 5-fluorouracil at 2,000 mg/m(2) or gefitinib at a dose of 500 mg daily with 5-fluorouracil at 1,600 mg/m(2) plus oxaliplatin has an acceptable safety profile.

Current role of antibody therapy in patients with metastatic colorectal cancer

In less than 10 years, the number and importance of non-surgical treatment modalities in patients with colorectal cancer (CRC) have increased dramatically, both in the adjuvant and the advanced settings. However, despite the improvement of cytotoxic therapy in CRC, many patients still develop progressive disease and unfortunately in patients with disease resistant to 5-fluorouracil/folinic acid, irinotecan and oxaliplatin, no effective cytotoxic therapy is known. The rapidly expanding knowledge in tumor biology has encouraged optimism for the possibility to find and target tumor-specific mechanisms and thereby increase both efficacy and tolerance. A great number of 'targeted drugs' are being tested in clinical trials and some of these new drugs, like bevacizumab, cetuximab and panitumumab, are available for routine use in health care. These new targeted drugs will expand the therapeutic arsenal in CRC to a great extent, but they will also add to the complexity of treatment of CRC. In this review, we summarize the current status of antibody therapy in patients with CRC.