Insulin-like growth factor-I receptor signalling and acquired resistance to gefitinib (ZD1839; Iressa) in human breast and prostate cancer cells

The status of targeted agents in the setting of neoadjuvant radiation therapy in locally advanced rectal cancers

Radiotherapy has a longstanding and well-defined role in the treatment of resectable rectal cancer to reduce the historically high risk of local recurrence. In more advanced borderline or unresectable cases, where the circumferential resection margin (CRM) is breached or threatened according to magnetic resonance imaging (MRI), despite optimized local multimodality treatment and the gains achieved by modern high quality total mesorectal excision (TME), at least half the patients fail to achieve sufficient downstaging with current schedules. Many do not achieve an R0 resection. In less locally advanced cases, even if local control is achieved, this confers only a small impact on distant metastases and a significant proportion of patients (30-40%) still subsequently develop metastatic disease. In fact, distant metastases have now become the predominant cause of failure in rectal cancer. Therefore, increasing the intensity and efficacy of chemotherapy and chemoradiotherapy by integrating additional cytotoxics and biologically targetted agents seems an appealing strategy to explore-with the aim of enhancing curative resection rates and improving distant control and survival. However, to date, we lack validated biomarkers for these biological agents apart from wild-type KRAS. For cetuximab, the appearance of an acneiform rash is associated with response, but low levels of magnesium appear more controversial. There are no molecular biomarkers for bevacizumab. Although some less invasive clinical markers have been proposed for bevacizumab, such as circulating endothelial cells (CECS), circulating levels of VEGF and the development of overt hypertension, these biomarkers have not been validated and are observed to emerge only after a trial of the agent. We also lack a simple method of ongoing monitoring of 'on target' effects of these biological agents, which could determine and pre-empt the development of resistance, prior to radiological and clinical assessessments or even molecular imaging. These shortcomings probably explain our current relative lack of success in the arena of combining these agents with chemoradiation.

Acquired resistance of non-small cell lung cancer to epidermal growth factor receptor tyrosine kinase inhibitors

Activation of epidermal growth factor receptor (EGFR) triggers anti-apoptotic signaling, proliferation, angiogenesis, invasion, metastasis, and drug resistance, which leads to development and progression of human epithelial cancers, including non-small cell lung cancer (NSCLC). Inhibition of EGFR by tyrosine kinase inhibitors such as gefitinib and erlotinib has provided a new hope for the cure of NSCLC patients. However, acquired resistance to gefitinib and erlotinib via EGFR-mutant NSCLC has occurred through various molecular mechanisms such as T790M secondary mutation, MET amplification, hepatocyte growth factor (HGF) overexpression, PTEN downregulation, epithelial-mesenchymal transition (EMT), and other mechanisms. This review will discuss the biology of receptor tyrosine kinase inhibition and focus on the molecular mechanisms of acquired resistance to tyrosine kinase inhibitors of EGFR-mutant NSCLC.

Phosphorylated insulin-like growth factor-1 receptor (pIGF1R) is a poor prognostic factor in brain metastases from lung adenocarcinomas

A greater understanding of brain metastases is imperative for developing novel therapeutic strategies. Our previous study showed that insulin-like growth factor (IGF) signaling pathway was activated in brain-tropic cancer cells. In this study, we investigated the clinical relevance of activated (phosphorylated) IGF-1 receptor (pIGF1R) expression in brain metastases originating from lung adenocarcinomas. All pathologically confirmed brain metastases from lung adenocarcinomas, with available archived specimens from January 1998 to December 2009 at National Taiwan University Hospital, were assessed immunohistochemically for pIGF1R expression using H-score criteria. A median H-score was used as a cutoff point to define high or low pIGF1R expression. The mutation status in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) was examined using direct sequencing. The prognostic significance of pIGF1R expression, its correlations with clinicopathological characteristics, and EGFR status were evaluated. In the 86 cases, high membranous/cytoplasmic pIGF1R expression in brain metastases correlated with a shorter median survival (10.8 vs 27.8 mo, P = 0.003). This correlation was more significant in patients with EGFR mutations [hazard ratio (HR) 2.38, 95 % confidence interval (CI) 1.19-4.77 for EGFR mutations; HR 1.99, 95 % CI 0.95-4.15 for EGFR wild type] and remained statistically significant in multivariate analysis after adjusting for the effects of other potential prognostic factors, including the graded prognostic assessment score, solitary brain metastasis, extracranial metastatic status, EGFR mutations, and treatment using EGFR tyrosine kinase inhibitors. Although we also identified nuclear pIGF1R expression, this result was prognostically non-significant. Our study results showed that high membranous/cytoplasmic pIGF1R expression in brain metastases was a poor prognostic factor, more significantly in patients with EGFR mutations than in those with wild-type EGFRs.

Potentiating the efficacy of molecular targeted therapy for hepatocellular carcinoma by inhibiting the insulin-like growth factor pathway

Insulin-like growth factor (IGF) signaling pathway is an important regulatory mechanism of tumorigenesis and drug resistance in many cancers. The present study explored the potential synergistic effects between IGF receptor (IGFR) inhibition and other molecular targeted agents (MTA) in HCC cells. HCC cell lines (Hep3B, PLC5, and SK-Hep1) and HUVECs were tested. The MTA tested included sorafenib, sunitinib, and the IGFR kinase inhibitor NVP-AEW541. The potential synergistic antitumor effects were tested by median dose effect analysis and apoptosis assay in vitro and by xenograft models in vivo. The activity and functional significance of pertinent signaling pathways and expression of apoptosis-related proteins were measured by RNA interference and Western blotting. We found that IGF can activate IGFR and downstream AKT signaling activities in all the HCC cells tested, but the growth-stimulating effect of IGF was most prominent in Hep3B cells. NVP-AEW541 can abrogate IGF-induced activation of IGFR and AKT signaling in HCC cells. IGF can increase the resistance of HCC cells to sunitinib. The apoptosis-inducing effects of sunitinib, but not sorafenib, were enhanced when IGFR signaling activity was inhibited by NVP-AEW541 or IGFR knockdown. Chk2 kinase activation was found contributory to the synergistic anti-tumor effects between sunitinib and IGFR inhibition. Our data indicate that the apoptosis-potentiating effects of IGFR inhibition for HCC may be drug-specific. Combination therapy of IGFR inhibitors with other MTA may improve the therapeutic efficacy in HCC.

Stromal EGF and igf-I together modulate plasticity of disseminated triple-negative breast tumors

The causes for malignant progression of disseminated tumors and the reasons recurrence rates differ in women with different breast cancer subtypes are unknown. Here, we report novel mechanisms of tumor plasticity that are mandated by microenvironmental factors and show that recurrence rates are not strictly due to cell-intrinsic properties. Specifically, outgrowth of the same population of incipient tumors is accelerated in mice with triple-negative breast cancer (TNBC) relative to those with luminal breast cancer. Systemic signals provided by overt TNBCs cause the formation of a tumor-supportive microenvironment enriched for EGF and insulin-like growth factor-I (IGF-I) at distant indolent tumor sites. Bioavailability of EGF and IGF-I enhances the expression of transcription factors associated with pluripotency, proliferation, and epithelial-mesenchymal transition. Combinatorial therapy with EGF receptor and IGF-I receptor inhibitors prevents malignant progression. These results suggest that plasticity and recurrence rates can be dictated by host systemic factors and offer novel therapeutic potential for patients with TNBC.

Therapeutic destruction of insulin receptor substrates for cancer treatment

Insulin receptor substrates 1 and 2 (IRS1/2) mediate mitogenic and antiapoptotic signaling from insulin-like growth factor 1 receptor (IGF-IR), insulin receptor (IR), and other oncoproteins. IRS1 plays a central role in cancer cell proliferation, its expression is increased in many human malignancies, and its upregulation mediates resistance to anticancer drugs. IRS2 is associated with cancer cell motility and metastasis. Currently, there are no anticancer agents that target IRS1/2. We present new IGF-IR/IRS-targeted agents (NT compounds) that promote inhibitory Ser-phosphorylation and degradation of IRS1 and IRS2. Elimination of IRS1/2 results in long-term inhibition of IRS1/2-mediated signaling. The therapeutic significance of this inhibition in cancer cells was shown while unraveling a novel mechanism of resistance to B-RAF(V600E/K) inhibitors. We found that IRS1 is upregulated in PLX4032-resistant melanoma cells and in cell lines derived from patients whose tumors developed PLX4032 resistance. In both settings, NT compounds led to the elimination of IRS proteins and evoked cell death. Treatment with NT compounds in vivo significantly inhibited the growth of PLX4032-resistant tumors and displayed potent antitumor effects in ovarian and prostate cancers. Our findings offer preclinical proof-of-concept for IRS1/2 inhibitors as cancer therapeutics including PLX4032-resistant melanoma. By the elimination of IRS proteins, such agents should prevent acquisition of resistance to mutated-B-RAF inhibitors and possibly restore drug sensitivity in resistant tumors.

Biological agents alone or in combination as second-line therapy in advanced non-small-cell lung cancer: systematic review of randomized studies

The only approved agents for second-line therapy in unselected non-small-cell lung cancer are docetaxel and pemetrexed (chemotherapies) and erlotinib (targeted therapies). Several new molecular drugs have now entered clinical trials and are being compared with approved agents (e.g., vandetanib). Alternative pathways are also being explored to overcome resistance to established agents (c-MET and ALK inhibitors), and predictive factors are now crucial for the selection of drug and of patients (e.g., EGFR mutations). Better patient selection permits second-line treatment to be tailored according to disease identity, which confers a particular benefit in certain subgroups of patients. In this review, the authors examine existing trials comparing targeted therapies with the standard of care as second-line therapy for advanced non-small-cell lung cancer.

Concomitant high gene copy number and protein overexpression of IGF1R and EGFR negatively affect disease-free survival of surgically resected non-small-cell-lung cancer patients

BACKGROUND

Insulin-like growth factor 1 receptor (IGF1R) represents a novel molecular target in non-small-cell-lung cancer (NSCLC). IGF1R and epidermal growth factor receptor (EGFR) activation are essential to mediate tumor cell survival, proliferation, and invasion. This study investigates the prognostic role of IGF1R and EGFR in surgically resected NSCLC.

MATERIALS AND METHODS

IGF1R and EGFR copy number gain (CNG) were tested by fluorescence in situ hybridization (FISH) and protein expression by immunohistochemistry (IHC) in 125 stage I-II-IIIA NSCLC patients.

RESULTS

Fourty-six tumors (40.3%) were IGF1R FISH-positive (FISH+), and 76 (67.2%) were EGFR FISH+. Tumors with concomitant IGF1R/EGFR FISH+ were observed in 34 cases (30.1%). IGF1R and EGFR FISH+ were associated with SCC histology (p = 0.01 and p = 0.04, respectively). IGF1R and EGFR protein over-expression (IHC+) were detected in 45 (36.0%) and 69 (55.2%) cases, respectively. Tumors with concomitant IGF1R/EGFR IHC+ were detected in 31 (24.8%) patients. IGF1R/EGFR FISH+ and IGF1R/EGFR IHC+ were significantly associated (χ(2) = 4.02, p = 0.04). Patients with IGF1R/EGFR FISH+ and IGF1R/EGFR IHC+ were associated with shorter disease-free survival (DFS) (p = 0.05 and p = 0.05, respectively). Patients with concomitant IGF1R/EGFR FISH+/IHC+ had a worse DFS and overall survival (p = 0.005 and p = 0.01, respectively). The multivariate model confirmed that IGF1R/EGFR FISH+/IHC+ (hazard ratio (HR), 4.08; p = 0.01) and tumor stage (II-III vs I) (HR, 4.77; p = 0.003) were significantly associated with worse DFS.

CONCLUSIONS

IGF1R/EGFR FISH+ correlates with IGF1R/EGFR IHC+. IGF1R/EGFR FISH+/IHC+ is an independent negative prognostic factor for DFS in early NSCLC. These features may have important implications for future anti-IGF1R therapeutic approaches.

Design and conduct of early clinical studies of two or more targeted anticancer therapies: recommendations from the task force on Methodology for the Development of Innovative Cancer Therapies

The Methodology for the Development of Innovative Cancer Therapies (MDICT) task force considered aspects of the design and conduct of early (phase I and II) studies of combinations of molecular targeted agents during their 2012 meeting. The task force defined necessary non-clinical data, such as evidence of additive or synergistic effects in multiple molecularly credentialed and validated models, and appropriate pharmacodynamic marker development. A robust hypothesis was considered critical while non-clinical pharmacokinetic studies were also considered valuable. Clinical trials should include clear objectives that will prove or disprove the hypothesis. Predictive biomarkers/classifiers should be explored in phase I studies, rather than used to select patients. Trial design should be efficient and flexible rather than based on a strict progression from phase I to II to III; researchers could consider phase I studies with an expansion cohort, Phase I/II designs or phase II studies with a safety run in. Pharmacokinetics are recommended when interactions or overlapping toxicity is expected. Pharmacodynamic evaluations should be considered especially in a subset of patients closest to the recommended dose; an attempt should be made to validate surrogate tissues to enable inclusion for all patients. Schedule and or dose should be formally explored for e.g. with a randomised or an adaptive design. Data and knowledge sharing was strongly recommended, including the creation of formal or informal consortia of laboratories with individual expertise in pathway or target based models, collaboration between companies to ensure that agents which are 'best in class' are combined, and the development of databases which will be able to inform the development of future recommendations/guidelines.

Ganitumab with either exemestane or fulvestrant for postmenopausal women with advanced, hormone-receptor-positive breast cancer: a randomised, controlled, double-blind, phase 2 trial

BACKGROUND

Insulin-like growth factors (IGF-1 and IGF-2) bind to the IGF-1 receptor (IGF-1R), increasing cell proliferation and survival. Ganitumab is a monoclonal IgG1 antibody that blocks IGF-1R. We tested the efficacy and safety of adding ganitumab to endocrine treatment for patients with hormone-receptor-positive breast cancer.

METHODS

We did this phase 2 trial in outpatient clinics and hospitals. We enrolled postmenopausal women with hormone-receptor-positive, locally advanced or metastatic breast cancer previously treated with endocrine treatment. They were randomly assigned (2:1) with a central randomisation schedule to receive intravenous ganitumab 12 mg per kg bodyweight or placebo in combination with open-label intramuscular fulvestrant (500 mg on day 1, then 250 mg on days 15, 29, and every 28 days) or oral exemestane (25 mg once daily) on a 28-day cycle. Patients, investigators, study monitors, and the sponsor staff were masked to treatment allocation. Response was assessed every 8 weeks. The primary endpoint was median progression-free survival in the intention-to-treat population. We analysed overall survival as one of our secondary endpoints. The study is registered at ClinicalTrials.gov, number NCT00626106.

FINDINGS

We screened 189 patients and enrolled 156 (106 in the ganitumab group and 50 in the placebo group). Median progression-free survival did not differ significantly between the ganitumab and placebo groups (3·9 months, 80% CI 3·6-5·3 vs 5·7 months, 4·4-7·4; hazard ratio [HR] 1·17, 80% CI 0·91-1·50; p=0·44). However, overall survival was worse in the the ganitumab group than in the placebo group (HR 1·78, 80% CI 1·27-2·50; p=0·025). With the exception of hyperglycaemia, adverse events were generally similar between groups. The most common grade 3 or higher adverse event was neutropenia-reported by six of 106 (6%) patients in the ganitumab group and one of 49 (2%) in the placebo group. Hyperglycaemia was reported by 12 of 106 (11%) patients in the ganitumab group (with six patients having grade 3 or 4 hyperglycaemia) and none of 49 in the placebo group. Serious adverse events were reported by 27 of 106 (25%) patients in the ganitumab group and nine of 49 (18%) patients in the placebo group.

INTERPRETATION

Addition of ganitumab to endocrine treatment in women with previously treated hormone-receptor-positive locally advanced or metastatic breast cancer did not improve outcomes. Our results do not support further study of ganitumab in this subgroup of patients.

FUNDING

Amgen.

Molecular mapping the presence of druggable targets in preinvasive and precursor breast lesions: a comprehensive review of biomarkers related to therapeutic interventions

The analysis of clinical breast samples using biomarkers is integral to current breast cancer management. Currently, a limited number of targeted therapies are standard of care in breast cancer treatment. However, these targeted therapies are only suitable for a subset of patients and resistance may occur. Strategies to prevent the occurrence of invasive lesions are required to reduce the morbidity and mortality associated with the development of cancer. In theory, application of targeted therapies to pre-invasive lesions will prevent their progression to invasive lesions with full malignant potential. The diagnostic challenge for pathologists is to make interpretative decisions on early detected pre-invasive lesions. Overall, only a small proportion of these pre-invasive lesions will progress to invasive carcinoma and morphological assessment is an imprecise and subjective means to differentiate histologically identical lesions with varying malignant potential. Therefore differential biomarker analysis in pre-invasive lesions may prevent overtreatment with surgery and provide a predictive indicator of response to therapy. There follows a review of established and emerging potential druggable targets in pre-invasive lesions and correlation with lesion morphology.

Treatment with a combination of the ErbB (HER) family blocker afatinib and the IGF-IR inhibitor, NVP-AEW541 induces synergistic growth inhibition of human pancreatic cancer cells

Background

Aberrant expression and activation of the IGF-IR have been reported in a variety of human cancers and have been associated with resistance to HER targeted therapy. In this study, we investigated the effect of simultaneous targeting of IGF-IR and HER (erbB) family, with NVP-AEW541 and afatinib, on proliferation of pancreatic cancer cells.

Methods

The sensitivity of a panel of human pancreatic cancer cell lines to treatment with NVP-AEW541 used alone or in combination with afatinib, anti-EGFR antibody ICR62, and cytotoxic agents was determined using the Sulforhodamine B colorimetric assay. Growth factor receptor expression, cell-cycle distribution and cell signalling were determined using flow cytometry and western blot analysis.

Results

All pancreatic cancer cell lines were found to be IGF-IR positive and NVP-AEW541 treatment inhibited the growth of the pancreatic cancer cell lines with IC50 values ranging from 342 nM (FA6) to 2.73 μM (PT45). Interestingly, of the various combinations examined, treatment with a combination of NVP-AEW541 and afatinib was superior in inducing synergistic growth inhibition of the majority of pancreatic cancer cells.

Conclusion

Our results indicate that co-targeting of the erbB (HER) family and IGF-IR, with a combination of afatinib and NVP-AEW541, is superior to treatment with a single agent and encourages further investigation in vivo on their therapeutic potential in IGF-IR and HER positive pancreatic cancers.

Clinical development of insulin-like growth factor receptor--1 (IGF-1R) inhibitors: at the crossroad?

Insulin like growth factor receptor (IGF-1R) targeting became one of the most investigated areas in anticancer drug development during the last decade. Strategies aiming to block IGF-1R activity include monoclonal antibodies, tyrosine kinase inhibitors and anti-ligands antibodies. Initial enthusiasm quickly encountered challenges. Unfortunately the validation of the efficacy of IGF-1R targeted agents in large clinical trials failed, however anecdotal single agent activity was seen in early studies. Consequently, questions regarding the selection of right target population and the appropriate trial design are arising. Despite the plethora of clinical trials conducted no predictive biomarker has been validated so far and resistance mechanisms to IGF-1R inhibitors remain unclear. The other issue to be addressed is how to best combine IGF-1R inhibitors with other therapeutic approaches. This review highlights the most relevant clinical data emphasizing the main tumor types where IGF-1R inhibition showed potential interest. We also tried to extract based on clinical and translational data some candidate biomarkers that could help better to select patient population who potentially could benefit most from this therapeutic approach.

Development of antibody therapeutics for small cell lung cancer

INTRODUCTION

Small cell lung cancer (SCLC) is one of most aggressive cancers and only modest improvements have been achieved in overall survival over last 30 years. In recent years, antibody therapeutics has been actively studied and shown promise in treatment of SCLC.

AREAS COVERED

A comprehensive literature search through Medline and the registry database of clinical trials (ClinicalTrials.gov) was performed to collect all relevant preclinical and clinical data. The diverse antibody therapeutics which target against different antigens including VEGE-A, CEA, IGF-1R, CD56, EpCAM, CTLA-4, gangliosides GD2 and GD3, Lewis Y and tenascin-C are now under clinical investigation for therapeutic effects in SCLC.

EXPERT OPINION

During the last few decades, progresses have been made in antibody therapy for SCLC, however great challenges still remain. The major reasons are the complexity of SCLC and a lack of understanding of cancer immunology. The profound studies of signaling pathways involved in carcinogenesis, proliferation, metastasis and apoptosis in SCLC are crucial for the identification of new therapeutic targets and biomarkers. Moreover, a better understanding of the interplay between cancer and the immune system is a new direction for the design of more effective antibody therapeutics.

Research progress on criteria for discontinuation of EGFR inhibitor therapy

The clinical success of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) as therapeutic agents has prompted great interest in their further development and clinical testing for a wide variety of malignancies. However, most studies have focused on the efficacy of TKI, and few studies have been done on the criteria for their discontinuation. The current standard for drug discontinuation is “until progression”, based on change in tumor size. However, tumor size is not related to the gene expression which determines the efficacy of TKI in the final analysis, and it is also difficult to make a thorough and correct prediction based on tumor size when the TKI is discontinued. Nevertheless, clinical evaluation of the criteria for TKI discontinuation is still in its early days. Some promising findings have started to emerge. With the improving knowledge of EGFR and its inhibitors, it is expected that the criteria for discontinuation of EGFR inhibitor therapy will become clearer.

The epidermal growth factor receptor as a therapeutic target in epithelial ovarian cancer

A majority of patients with ovarian carcinoma who receive conventional treatment of surgical staging and platinum-based chemotherapy recur and ultimately succumb to their diseases. Novel therapies that target specific pathways involved in ovarian tumorigenesis are rapidly emerging. The epidermal growth factor receptor (EGFR) is overexpressed in 30-98% of epithelial ovarian carcinoma (EOC), and the signaling cascades activated are related with cell proliferation, migration and invasion, and angiogenesis, as well as resistance to cell apoptosis. Various trials are ongoing focusing on EGFR as an attractive target in treatment of EOC. Anti-EGFR monoclonal antibodies (MAbs), cetuximab and panitumumab, and tyrosine kinase inhibitors (TKIs), erlotinib and gefitinib, are the most advanced in clinical development. The available data suggests that MAbs and TKIs only show marginal activity when they are used alone, but combination with platinum-based chemotherapy can induce elevated overall response rate in recurrent EOC patients. Consequently, mechanisms for intrinsic and extrinsic resistance have been explored due to the poor clinical response to EGFR-targeted therapy. Careful consideration of these clinical studies and the possible mechanisms involved in resistance can provide evidence for improvements in subsequent research. Identification of responder profiles and development of rational regimen of combination therapy of EGFR-targeted therapy with other effective treatment modalities may eventually bring about substantial progress in the treatment of epithelial ovarian cancers.

Optimization of IGF-1R SPECT/CT imaging using 111In-labeled F(ab')2 and Fab fragments of the monoclonal antibody R1507

The insulin-like growth factor 1 receptor (IGF-1R) is a potential new target for the treatment of breast cancer. Patients with breast cancer lesions that express IGF-1R may benefit from treatment with anti-IGF-1R antibodies. IGF-1R expression can be visualized using radiolabeled R1507, a monoclonal antibody directed against IGF-1R. However, antibodies clear slowly from the circulation, resulting in low tumor-to-background ratios early after injection. Therefore, we aimed to accelerate targeting of IGF-1R using radiolabeled R1507 F(ab')2 and Fab fragments. In vitro, immunoreactivity, binding affinity and internalization of R1507 IgG, F(ab')2 and Fab were determined using the triple negative IGF-1R-expressing breast cancer cell line SUM149. In vivo, pharmacokinetics of (111)In-labeled R1507 IgG, F(ab')2 and Fab were studied in mice bearing subcutaneous SUM149 xenografts. SPECT/CT images were acquired and the biodistribution was measured ex vivo. The in vitro binding characteristics of radiolabeled R1507 IgG and F(ab')2 were comparable, whereas the affinity of Fab fragments was significantly lower (Kd: 0.6 nM, 0.7 nM and 3.0 nM for R1507 IgG, F(ab')2 and Fab, respectively). Biodistribution studies showed that the maximum tumor uptake of (111)In-R1507 IgG, F(ab')2 and Fab was 31.8% ID/g (72 h p.i.), 10.0% ID/g (6 h p.i.), and 1.8% ID/g (1 h p.i.), respectively. However, maximal tumor-to-blood ratios for F(ab')2 (24 h p.i.: 7.5) were more than twice as high as those obtained with R1507 (72 h p.i.: 2.8) and Fab (6 h p.i.: 2.8). Injection of an excess of unlabeled R1507 significantly reduced tumor uptake, suggesting that the uptake of R1507 IgG and F(ab')2 was specific for IGF-1R, while the major fraction of the tumor uptake of Fab was nonspecific. IGF-1R-expressing xenografts were visualized with (111)In-F(ab')2 SPECT/CT as early as 6 h p.i., while with R1507 IgG, the tumor could be visualized after 24 h. No specific targeting was observed with (111)In-Fab. (111)In-F(ab')2 fragments showed improved targeting of IGF-1R expressing tumors. Tumor-to-blood ratios were twice as high as those obtained with (111)In-R1507, and adequate tumor targeting on SPECT/CT images was observed as early as 6 h p.i. For individualization and optimization of IGF-1R targeted therapy, (111)In-F(ab')2 may be the tracer of choice.

PET of EGFR expression with an 18F-labeled affibody molecule

Epidermal growth factor receptor (EGFR) is often overexpressed in a variety of human cancers, and its expression is associated with poor prognosis for many cancer types. However, an accurate technique to noninvasively image EGFR expression in vivo is not available in the clinical setting. In this research, an Affibody analog, anti-EGFR Ac-Cys-Z(EGFR:1907), was successfully site-specifically (18)F-labeled for PET of EGFR expression.

METHODS

The prosthetic group N-[2-(4-(18)F-fluorobenzamido) ethyl] maleimide ((18)F-FBEM) was conjugated to Ac-Cys-Z(EGFR:1907) under mild conditions (pH 7) to produce the probe (18)F-FBEM-Cys-Z(EGFR:1907). The binding affinity and specificity tests of (18)F-FBEM-Cys-Z(EGFR:1907) to EGFR were conducted using A431 cancer cells. Small-animal PET and biodistribution studies were conducted on various mice tumor xenograft models with EGFR overexpression (6 types) after injection of approximately 2.0 MBq of (18)F-FBEM-Cys-Z(EGFR:1907) with or without coinjection of unlabeled Ac-Cys-Z(EGFR:1907) for up to 3 h after injection. A correlation study between (18)F-FBEM-Cys-Z(EGFR:1907) small- animal PET quantification and ex vivo Western blot analysis of tumor EGFR expression was conducted in those 6 types of tumor models.

RESULTS

(18)F-FBEM-Cys-Z(EGFR:1907) binds to EGFR with low nanomolar affinity (37 nM) in A431 cells. (18)F-FBEM-Cys-Z(EGFR:1907) rapidly accumulated in the tumor and cleared from most of the normal organs except the liver and kidneys at 3 h after injection, allowing excellent tumor-to-normal tissue contrast to be obtained. In the A431 tumor xenograft model, coinjection of the PET probe with 45 μg of Ac-Cys-Z(EGFR:1907) was able to improve the tumor uptake (3.9 vs. 8.1 percentage of the injected radioactive dose per gram of tissue, at 3 h after injection) and tumor imaging contrast, whereas coinjection with 500 μg of Ac-Cys-Z(EGFR:1907) successfully blocked the tumor uptake significantly (8.1 vs. 1.0 percentage of the injected radioactive dose per gram of tissue, at 3 h after injection, 88% inhibition, P < 0.05). Moderate correlation was found between the tumor tracer uptake at 3 h after injection quantified by PET and EGFR expression levels measured by Western blot assay (P = 0.007, R = 0.59).

CONCLUSION

(18)F-FBEM-Cys-Z(EGFR:1907) is a novel protein scaffold-based PET probe for imaging EGFR overexpression of tumors, and its ability to differentiate tumors with high and low EGFR expression in vivo holds promise for future clinical translation.

Evaluation of four affibody-based near-infrared fluorescent probes for optical imaging of epidermal growth factor receptor positive tumors

The epidermal growth factor receptor 1 (EGFR) has become an attractive target for cancer molecular imaging and therapy. An Affibody protein with strong binding affinity for EGFR, ZEGFR:1907, has been reported. We are interested in translating Affibody molecules to potential clinical optical imaging of EGFR positive cancers. In this study, four anti-EGFR Affibody based near-infrared (NIR) fluorescent probes were thus prepared, and their in vivo performance was evaluated in the mice bearing EGFR positive subcutaneous A431 tumors.

METHODS

The Affibody analogue, Ac-Cys-ZEGFR:1907, was synthesized using solid-phase peptide synthesis method. The purified small protein was then site-specifically conjugated with four NIR fluorescent dyes, Cy5.5-monomaleimide, Alex-Fluor-680-maleimide, SRfluor680-maleimide, or IRDye-800CW-maleimide, to produce four optical probes-Cy5.5-ZEGFR:1907, Alexa680-ZEGFR:1907, SR680-ZEGFR:1907, and 800CW-ZEGFR:1907. The EGFR binding property and specificity of the four NIR fluorescent Affibody probes were studied by fluorescence microscopy using high EGFR expressing A431 cells and low expressing MCF7 cells. The binding affinities of the probes (KD) to EGFR were further determined by flow cytometry. In vivo optical imaging of the four probes was performed in the mice bearing subcutaneous A431 tumors.

RESULTS

The four NIR optical probes were prepared in high purity. In vitro cell imaging studies demonstrated that all of them could specifically bind to EGFR positive A431 cells while showing minimum uptake in low EGFR expressing MCF7 cells. Flow cytometry showed that Cy5.5-ZEGFR:1907 and Alexa680-ZEGFR:1907 possessed high binding affinity in low nanomolar range (43.6 ± 8.4 and 28.3 ± 4.9, respectively). In vivo optical imaging of the four probes revealed that they all showed fast tumor targeting ability and good tumor-to-normal tissue contrast as early as 0.5 h postinjection (p.i.). The tumor-to-normal tissue ratio reached a peak at 2 to 4 h p.i. by regional of interest (ROI) analysis of images. Ex vivo studies further demonstrated that the four probes had high tumor uptakes. Particularly, Cy5.5-ZEGFR:1907 and Alex680-ZEGFR:1907 displayed higher tumor-to-normal tissue ratios than those of the other two probes.

CONCLUSION

This work demonstrates that Affibody proteins can be modified with different NIR fluorescent dyes and used for imaging of EGFR expressing tumors. Different NIR fluorescent dyes have variable impact on the in vitro binding and in vivo performance of the resulting Affibody based probes. Therefore, selection of an appropriate NIRF label is important for optical probe development. The probes developed are promising for further tumor imaging applications and clinical translation. Particularly, Alex680-ZEGFR:1907 and Cy5.5-ZEGFR:1907 are excellent candidates as EGFR-targeted probes for optical imaging.

Proteomic analysis of Terminalia chebula extract-dependent changes in human lymphoblastic T cell protein expression

Terminalia chebula is a native plant from southern Asia to southwestern China that is used in traditional medicine for the treatment of malignant tumors and diabetes. This plant also has antibacterial and immunomodulatory properties. The present study assessed T. chebula extract-dependent protein expression changes in Jurkat cells. Matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry and Ingenuity Pathways Analysis (IPA) were performed to assess protein expression and networks, respectively. A comparative proteomic profile was determined in T. chebula extract (50 μg/mL)-treated and control cells; the expressions of β-tubulin, ring finger and CHY zinc finger domain containing 1, and insulin-like growth factor 1 receptor kinase were significantly down-regulated in T. chebula extract-treated Jurkat cells. Moreover, the molecular basis for the T. chebula extract-dependent protein expression changes in Jurkat cells was determined by IPA. Treatment with the T. chebula extract significantly inhibited nuclear factor-κB activity and affected the proteomic profile of Jurkat cells. The molecular network signatures and functional proteomics obtained in this study may facilitate the evaluation of potential antitumor therapeutic targets and elucidate the molecular mechanism of T. chebula extract-dependent effects in Jurkat cells.

Receptor tyrosine kinases and targeted cancer therapeutics

The majority of growth factor receptors are composed of extracellular, transmembrane, and cytoplasmic tyrosine kinase (TK) domains. Receptor tyrosine kinase (RTK) activation regulates many key processes including cell growth and survival. However, dysregulation of RTK has been found in a wide range of cancers, and it has been shown to correlate with the development and progression of numerous cancers. Therefore, RTK has become an attractive therapeutic target. One way to effectively block signaling from RTK is inhibition of its catalytic activity with small-molecule inhibitors. Low-molecular-weight TK inhibitors (TKIs), such as imatinib, targeting tumors with mutant c-Kit, and gefitinib, targeting non-small cell lung cancer with mutant epidermal growth factor receptor (EGFR), have received marketing approval in Japan. MET, fibroblast growth factor receptor (FGFR), and insulin-like growth factor-I receptor (IGF-IR) are frequently genetically altered in advanced cancers. TKIs of these receptors have not yet appeared on the market, but many anticancer drug candidates are currently undergoing clinical trials. Most of these TKIs were designed to compete with ATP at the ATP-binding site within the TK domain. This review will focus on small-molecule TKIs targeting MET, FGFR, and IGF-IR and discuss the merits and demerits of two types of agents, i.e., those with only one or a few targets and those directed at multiple targets. Targeting agents specifically inhibiting the target kinase were previously searched for based on the hypothesis that a narrow target window might reduce unexpected side effects, but agents with multiple targets have been recently developed to overcome tumors resistant against a single-targeting agent.

Present and Future of EGFR Inhibitors for Head and Neck Squamous Cell Cancer

Although EGFR is expressed at high levels in head and neck squamous cell carcinomas (HNSCCs) and mutations are extremely rare, monotherapy with EGFR inhibitors has shown limited success. The PI3kinase/Akt pathway is responsible for cellular survival, and inhibition of phosphatidylinositol (PI) synthesis has antiproliferative, anti-invasive, and antiangiogenesis effects on HNSCC. Molecular crosstalk has been observed between EGFR and IGF1R signaling through the PI3kinase/Akt pathway in HNSCC, as has molecular crosstalk between the NFκB and STAT3 signaling pathways. Therefore, the combination of an EGFR antagonist with an agent that inhibits the activation of both Akt and NFκB may overcome resistance to EGFR antagonists in HNSCC.

A phase I/II study of erlotinib in combination with the anti-insulin-like growth factor-1 receptor monoclonal antibody IMC-A12 (cixutumumab) in patients with advanced non-small cell lung cancer

INTRODUCTION

This phase I/II study evaluated the safety and antitumor effect of the combination of erlotinib with cixutumumab, a recombinant fully humanized anti-insulin-like growth factor-1 receptor IgG1 monoclonal antibody, in advanced non-small cell lung cancer (NSCLC).

METHODS

Patients with advanced NSCLC were treated in an initial safety-lead and drop-down cohorts using erlotinib 150 mg/d with cixutumumab 6 or 5 mg/kg on days 1, 8, 15, and 22 in 28-day cycles (cohorts 1 and 2). Emerging pharmacokinetic data led to an additional cohort (3 + 3 design) with cixutumumab at 15 mg/kg on day 1 in 21-day cycles (cohort 3).

RESULTS

Eighteen patients entered the study (6 at 6 mg/kg, 8 at 5 mg/kg, and 4 at 15 mg/kg), with median age of 65 years. Four of six patients at 6 mg/kg experienced dose-limiting toxicities (DLTs), whereas at 5 mg/kg, one of eight patients experienced DLT but three of eight patients still required a dose delay during cycle 1. At 15 mg/kg every 21 days, two of four patients experienced DLTs. In all cohorts, DLTs were either G3 rash or fatigue. Five patients had stable disease as best response and 14 patients had progressive disease. The median progression-free survival was 39 days (range 21-432+ days). Biomarkers analyses showed a trend toward better progression-free survival seen with higher free baseline insulin-like growth factor-1 levels as seen with other insulin-like growth factor-1R inhibitors.

CONCLUSIONS

The combinations of cixutumumab at 6 mg/kg every 7 days and 15 mg/kg every 21 days and full-dose erlotinib are not tolerable in unselected patients with NSCLC, as measured by DLT. Cixutumumab at 5 mg/kg every 7 days was tolerable per DLT, but dose delays were common. Efficacy in unselected patients with NSCLC seems to be low.

Randomized phase II study of erlotinib in combination with placebo or R1507, a monoclonal antibody to insulin-like growth factor-1 receptor, for advanced-stage non-small-cell lung cancer

PURPOSE

R1507 is a selective, fully human, recombinant monoclonal antibody (immunoglobulin G1 subclass) against insulin-like growth factor-1 receptor (IGF-1R). The strong preclinical evidence supporting coinhibition of IGF-1R and epidermal growth factor receptor (EGFR) as anticancer therapy prompted this study.

PATIENTS AND METHODS

Patients with advanced-stage non-small-cell lung cancer (NSCLC) with progression following one or two prior regimens, Eastern Cooperative Oncology Group (ECOG) performance status 0 to 2, and measurable disease were eligible. Patients were randomly assigned to receive erlotinib (150 mg orally once a day) in combination with either placebo, R1507 9 mg/kg weekly, or R1507 16 mg/kg intravenously once every 3 weeks. Treatment cycles were repeated every 3 weeks. The primary end point was comparison of the 12-week progression-free survival (PFS) rate.

RESULTS

In all, 172 patients were enrolled: median age, 61 years; female, 33%; never-smokers, 12%; and performance status 0 or 1, 88%. The median number of R1507 doses was six for the weekly arm and 3.5 for the every-3-weeks arm. Grades 3 to 4 adverse events occurred in 37%, 44%, and 48% of patients with placebo, R1507 weekly, and R1507 every 3 weeks, respectively. The 12-week PFS rates were 39%, 37%, and 44%, and the median overall survival was 8.1, 8.1, and 12.1 months for the three groups, respectively, with statistically nonsignificant hazard ratios. The 12-week PFS rate in patients with KRAS mutation was 36% with R1507 compared with 0% with placebo.

CONCLUSION

The combination of R1507 with erlotinib did not provide PFS or survival advantage over erlotinib alone in an unselected group of patients with advanced NSCLC. Predictive biomarkers are essential for further development of combined inhibition of IGF-1R and EGFR.

In vitro and in vivo assessment of targeting lipid-based nanoparticles to the epidermal growth factor-receptor (EGFR) using a novel Heptameric ZEGFR domain

Lipid-based oil-filled nanoparticles (NPs) with a high concentration of surface-chelated nickel (Ni-NPs) were successfully prepared using a Brij 78-NTA-Ni conjugate synthesized with Brij 78 (Polyoxyethylene (20) stearyl ether) and nitrilotriacetic acid (NTA). The facile incorporation of the Brij 78-NTA-Ni conjugate into the NP formulation allowed up to 90% Ni incorporation, which was a significant improvement over the previously used standard agent DOGS-NTA-Ni which led to ~6% Ni incorporation. The Ni-NPs were targeted to the highly epidermal growth factor receptor (EGFR)-overexpressing epidermoid carcinoma cells A431. This was accomplished using a novel high affinity histidine×6-tagged EGFR-binding Z domain (heptameric Z(EGFR) domain). In vitro cell uptake studies showed enhanced internalization (up to 90%) of the targeted Ni-NPs in A431 cells with only ≤10% internalization of the untargeted Ni-NPs. ICP-MS analysis used to quantify the amount of Ni in the cells were in close agreement with flow cytometry studies, which showed a dose dependent increase in the amount of Ni with the targeted Ni-NPs. Cell uptake competition studies showed that internalization of the targeted Ni-NPs within the cells was competed off with free heptameric Z(EGFR) domain at concentrations of 8.75ng/mL or higher. In vivo studies were carried out in nude mice bearing A431 tumors to determine the biodistribution and intracellular delivery. Near Infrared (NIR) optical imaging studies using Alexa750-labeled heptameric Z(EGFR) domain showed localization of 19% of the total detected fluorescence intensity in the tumor tissue, 28% in the liver and 42% in the kidneys 16h post i.v. injection. ICP-MS analysis showed almost a two-fold increase in the amount of intracellular Ni with the targeted Ni-NPs. These new Ni-NPs could be a very useful tool for targeting and drug delivery to a wide range of EGFR positive cancers.

Antitumor effects of carnertinib in castration resistant prostate cancer models: a comparative study with erlotinib

BACKGROUND AND PURPOSE

Although preclinical results suggest that the inhibition of erb-B1 or erb-B2 can be an useful tool to castration resistant prostate cancer (CRPC), neither inhibitor demonstrated to provide benefit in this category of patient. Here, we compared the effects of erlotinib, a specific EGFR inhibitor, with those observed with Carnertinib, an orally available pan-erbB receptor inhibitor, in a wide panel of hormone sensitive and independent prostate cancer cell lines.

MATERIALS AND METHODS

Variation in proliferation rate, cell cycle, and apoptosis after erlotinib and carnertinib treatments will be evaluated in vitro. In vivo experiments were performed using two models of CRPC, 22rv1 (AR expressing), and PC3 (AR negative) cell lines grown in nude mice. Intact nude mice bearing 22rv1 cells also received bicalutamide (BCLT) in combination with anti-target agents.

RESULTS

Here, we found that Erlotinib and carnertinib effectiveness was positively related to expression and activation levels of Her2, whereas erlotinib effectiveness was influenced to the EGFR/Her2 ratio resulting more effective when EGFR levels were significantly higher of Her2. Overall, in vitro carnertinib efficacy was higher than those observed with erlotinib. The combination between erlotinib and androgen deprivation therapy or BCLT showed no significant effects when compared to single treatments whereas carnertinib was active in presence of any anti-hormone manipulation.

CONCLUSIONS

Erlotinib efficacy was higher in androgen-sensitive PCa cells when we compare to the effects evident in CRPC cells, whereas the carnertinib efficacy may have therapeutical significance in Her2 overexpressing AR+ CRPC models in combination with hormone manipulation.

The role of the insulin-like growth factor signaling pathway in non-small cell lung cancer and other solid tumors

The type 1 insulin-like growth factor receptor (IGF-1R) and its downstream signaling components have become increasingly recognized as having a driving role in the development of malignancy, and consequently IGF-1R has become a potential target for cancer therapy. Several inhibitors of IGF-1R are in clinical development for the treatment of solid tumors, including non-small cell lung cancer (NSCLC). These IGF-1R-targeted agents include monoclonal antibodies such as cixutumumab (IMC-A12), AMG-479, AVE1642, BIIB022, dalotuzumab (MK-0646), and robatumumab (Sch717454), the ligand neutralizing antibody Medi-573, and the small molecule inhibitors BMS-754807, linsitinib (OSI-906), XL228, and AXL1717. Two phase III trials of the anti-IGF-1R monoclonal antibody, figitumumab (CP-751,871), were discontinued in 2010 as it was considered unlikely either trial would meet their primary endpoints. In light of disappointing clinical data with figitumumab and other targeted agents, it is likely that the use of molecular markers will become important in predicting response to treatment. This review outlines the role of IGF-1R signaling in solid tumors with a particular focus on NSCLC, and provides an overview of clinical data.

Activation of the insulin-like growth factor-1 receptor induces resistance to epidermal growth factor receptor antagonism in head and neck squamous carcinoma cells

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) have poor efficacy in head and neck squamous carcinoma cells (HNSCC). Because the IGF-1 receptor (IGF1R) generates potent prosurvival signals and has been implicated in therapeutic resistance, its ability to induce resistance to EGFR-TKIs was studied in vitro. Five HNSCC cell lines showed reduced sensitivity to the EGFR-TKI gefitinib when the IGF1R was activated. In SCC-25 and Cal27 cells, gefitinib inhibited basal and EGF-stimulated EGFR, extracellular signal-regulated kinase (Erk), and Akt phosphorylation and reduced cell number. This correlated with initiation of apoptosis based on a 4-fold increase in PARP cleavage and a 2.5-fold increase in Annexin V positivity. The apoptotic response and reduction in cell number were blocked by IGF1R activation, which resulted in phosphorylation of both Erk and Akt. In both the cell lines, IGF1R-induced Erk, but not Akt, activation was eliminated by gefitinib. IGF1R-induced gefitinib resistance was unaffected by MAP/Erk kinase inhibition with U0126 but was partially impaired by inhibition of phosphoinositide-3-kinase with LY294002. The IGF1R-TKI PQ401 inhibited growth of SCC-25 and Cal27 cells alone and also acted synergistically with gefitinib. Thus, the IGF1R can make HNSCC cells resistant to EGFR-TKI treatment via a prosurvival mechanism. Of the 8 HNSCC tumor samples studied, all samples expressed the IGF1R and 5 showed detectable IGF1R phosphorylation, suggesting that this receptor may be relevant in vivo, and thus, combined EGFR/IGF1R inhibition may be necessary in some patients for effective targeted molecular therapy.

LIP expression is regulated by IGF-1R signaling and participates in suppression of anoikis

Background

The transcription factor, CCAAT enhancer binding protein-β (C/EBPβ), is expressed as several distinct protein isoforms (LAP1, LAP2 and LIP) that have opposing actions in cellular proliferation and differentiation. Increases in the ratio of LIP/LAP are associated with aggressive, metastatic breast cancer; however, little is known regarding the molecular mechanisms that regulate LIP expression or the biological actions of an increase in the LIP/LAP ratio. Metastasis is highly dependent upon the suppression of anoikis and the role of C/EBPβ and LIP in this anchorage-independent, survival process is currently not known in mammary epithelial cells. IGF-1R signaling is important for the survival of breast cancer cells and crosstalk between IGF-1R and EGFR signaling pathways have been implicated in the development of more aggressive disease. We therefore evaluated in mammary epithelial cells whether IGF-1R signaling regulates the LIP/LAP ratio, analyzed the potential interplay between EGFR and IGF-1R signaling and addressed the biological significance of increased LIP expression in cellular survival and suppression of anoikis.

Results

Our data provide the first evidence that IGF-1R signaling regulates LIP expression in an EGFR independent manner to increase the LIP/LAP ratio in mammary epithelial cells. Although crosstalk between IGF-1R signaling and EGFR signaling is detectable in MCF10A cells, this crosstalk is not required for the IGF-1 mediated regulation of LIP expression. Rather, the critical regulator of IGF-1 induced LIP expression appears to be EGFR-independent, Akt activity. Our data also demonstrate that increases in LIP expression promote cell survival via suppression of anoikis. Likewise, knockdown of total C/EBPβ leads to increased cell death and suggest that C/EBPβ expression is important for survival and resistance to anoikis. IGF-1 treatment can partially rescue vector control cells from anoikis; however, cells with reduced C/EBPβ expression do not survive anoikis.

Conclusions

Taken together, our data demonstrate that IGF-1R signaling regulates LIP expression in an EGFR independent manner to increase the LIP/LAP ratio in mammary epithelial cells. C/EBPβ expression and elevations in LIP play an important role in regulating cellular survival via suppression of anoikis, in an IGF-1R mediated context or in a manner independent of IGF-1R signaling.

Dual inhibition of epidermal growth factor and insulin-like 1 growth factor receptors reduce intestinal adenoma burden in the Apc(min/+) mouse

Background:

Identification of early molecular pathway changes may be useful as biomarkers for tumour response/resistance prediction, and here we provide direct in vivo proof of this concept. The type 1 insulin-like growth factor receptor (IGF1R) has been implicated in various aspects of adenoma development and metastasis. We show here that, in murine intestinal adenomas acutely exposed to a small molecular inhibitor of EGFR (gefitinib), there is concurrent suppression of EGFR downstream signalling and induction of IGF signalling. We therefore tested the hypothesis that blockade of EGFR signalling was being tempered by compensatory activation of the IGF pathway by examining the effect of chronic suppression of IGF1R using AZ12253801, a small molecular tyrosine kinase inhibitor of IGF1R.

Methods:

Male Apc^min/+ mice with an intestinal tumour burden were exposed to a single dose of an inhibitor against EGFR (gefitinib), IGF1R (AZ12253801), 0.5% Tween 80 or combined EGFR/IGF1R inhibitor and culled 4 h post dosing. Tumour tissue was analysed to detect the early molecular pathways induced and anti-tumour phenotypic changes. Cohorts of male Apc^min/+ mice (n=15–17) were subsequently treated with gefitinib for a period of 8 weeks and subsequently exposed to single (either gefitinib or AZ12253801) or combined (gefitinib and AZ12253801) therapy. We also included a vehicle-treated cohort, which was never exposed to gefitinib and became symptomatic of the disease by day 150.

Results:

Both single treatments delayed the onset of disease symptoms. Combined dosing with gefitinib and AZ12253801 similarly delayed the onset of symptoms, and at 200 days suppressed small intestinal tumourigenesis more effectively than either treatment alone (median small intestinal adenoma volume (47 mm³ (comb) vs 248 mm³ (AZ12253801), P=0.0003 and 47 mm³ (comb) vs 123 mm³ (gefitinib), P=0.0042, Mann–Whitney (two-sided) test).

Conclusion:

Our data provide evidence in support of the use of combinatorial therapy, and establishes the need to further define the precise benefit in vivo.

Dual targeting of the insulin-like growth factor and collateral pathways in cancer: combating drug resistance

The insulin-like growth factor pathway, regulated by a complex interplay of growth factors, cognate receptors, and binding proteins, is critically important for many of the hallmarks of cancer such as oncogenesis, cell division, growth, and antineoplastic resistance. Naturally, a number of clinical trials have sought to directly abrogate insulin-like growth factor receptor 1 (IGF-1R) function and/or indirectly mitigate its downstream mediators such as mTOR, PI3K, MAPK, and others under the assumption that such therapeutic interventions would provide clinical benefit, demonstrable by impaired tumor growth as well as prolonged progression-free and overall survival for patients. Though a small subset of patients enrolled within phase I or II clinical trials revealed dramatic clinical response to IGF-1R targeted therapies (most using monoclonal antibodies to IGF-1R), in toto, the anticancer effect has been underwhelming and unsustained, as even those with marked clinical responses seem to rapidly acquire resistance to IGF-1R targeted agents when used alone through yet to be identified mechanisms. As the IGF-1R receptor is just one of many that converge upon common intracellular signaling cascades, it is likely that effective IGF-1R targeting must occur in parallel with blockade of redundant signaling paths. Herein, we present the rationale for dual targeting of IGF-1R and other signaling molecules as an effective strategy to combat acquired drug resistance by carcinomas and sarcomas.

Targeting insulin-like growth factor axis in hepatocellular carcinoma

The insulin-like growth factor (IGF) axis contains ligands, receptors, substrates, and ligand binding proteins. The essential role of IGF axis in hepatocellular carcinoma (HCC) has been illustrated in HCC cell lines and in animal xenograft models. Preclinical evidence provides ample indication that all four components of IGF axis are crucial in the carcinogenic and metastatic potential of HCC. Several strategies targeting this system including monoclonal antibodies against the IGF 1 receptor (IGF-1R) and small molecule inhibitors of the tyrosine kinase function of IGF-1R are under active investigation. This review describes the most up-to-date understanding of this complex axis in HCC, and provides relevant information on clinical trials targeting the IGF axis in HCC with a focus on anti-IGF-1R approach. IGF axis is increasingly recognized as one of the most relevant pathways in HCC and agents targeting this axis can potentially play an important role in the treatment of HCC.

Targeting insulin-like growth factor axis in hepatocellular carcinoma

The insulin-like growth factor (IGF) axis contains ligands, receptors, substrates, and ligand binding proteins. The essential role of IGF axis in hepatocellular carcinoma (HCC) has been illustrated in HCC cell lines and in animal xenograft models. Preclinical evidence provides ample indication that all four components of IGF axis are crucial in the carcinogenic and metastatic potential of HCC. Several strategies targeting this system including monoclonal antibodies against the IGF 1 receptor (IGF-1R) and small molecule inhibitors of the tyrosine kinase function of IGF-1R are under active investigation. This review describes the most up-to-date understanding of this complex axis in HCC, and provides relevant information on clinical trials targeting the IGF axis in HCC with a focus on anti-IGF-1R approach. IGF axis is increasingly recognized as one of the most relevant pathways in HCC and agents targeting this axis can potentially play an important role in the treatment of HCC.

Discovery of OSI-906: a selective and orally efficacious dual inhibitor of the IGF-1 receptor and insulin receptor

BACKGROUND

The IGF-1 receptor (IGF-1R) has been implicated in the promotion of tumorigenesis, metastasis and resistance to cancer therapies. Therefore, this receptor has become a major focus for the development of anticancer agents.

RESULTS

Our lead optimization efforts that blended structure-based design and empirical medicinal chemistry led to the discovery of OSI-906, a novel small-molecule dual IGF-1R/insulin receptor (IR) kinase inhibitor. OSI-906 potently and selectively inhibits autophosphorylation of both human IGF-1R and IR, displays in vitro antiproliferative effects in a variety of tumor cell lines and shows robust in vivo anti-tumor efficacy in an IGF-1R-driven xenograft model when administered orally once daily.

CONCLUSION

OSI-906 is a novel, potent, selective and orally bioavailable dual IGF-1R/IR kinase inhibitor with favorable preclinical drug-like properties, which has demonstrated in vivo efficacy in tumor models and is currently in clinical testing.

Inhibition of cytohesin-1 by siRNA leads to reduced IGFR signaling in prostate cancer

To explore how cytohesin-1 (CYTH-1) small interfering RNA (siRNA) influences the insulin-like growth factor receptor (IGFR)-associated signal transduction in prostate cancer, we transfected human prostate cancer PC-3 cell lines with liposome-encapsulated CYTH-1 siRNA in serum-free medium and exposed the cells to 100 nM IGF-1. The mRNA and protein levels of the signal molecules involved in the IGFR signaling pathways were determined by real-time PCR and detected by Western blotting. The relative mRNA levels of CYTH-1, c-Myc, cyclinD1 and IGF-1R (CYTH-1 siRNA group vs scrambled siRNA group) were 0.26 vs 0.97, 0.34 vs 1.06, 0.10 vs 0.95, and 0.27 vs 0.41 (P < 0.05 for all), respectively. The relative protein levels of CYTH-1, pIGF-1R, pIRS1, pAkt1, pErk1, c-Myc, and cyclinD1 (CYTH-1 siRNA group vs scrambled siRNA group) were 0.10 vs 1.00 (30 min), 0.10 vs 0.98 (30 min), 0.04 vs 0.50 (30 min), 0.10 vs 1.00 (30 min), 0.10 vs 1.00 (30 min), 0.13 vs 0.85 (5 h), and 0.08 vs 0.80 (7 h), respectively. The tyrosine kinase activity of IGF-1R was associated with CYTH-1. The proliferative activity of PC-3 cells transfected with CYTH-1 siRNA was significantly lower than that of cells transfected with scrambled siRNA at 48 h (40.5 vs 87.6%, P < 0.05) and at 72 h (34.5 vs 93.5%, P < 0.05). In conclusion, the interference of siRNA with cytohesin-1 leads to reduced IGFR signaling in prostate cancer; therefore, CYTH-1 might serve as a new molecular target for the treatment of prostate cancer.

Targeting GPCR-mediated p70S6K activity may improve head and neck cancer response to cetuximab

PURPOSE

Epidermal growth factor receptor (EGFR) overexpression is correlated with decreased survival in head and neck cancer (HNC) where the addition of EGFR inhibition to standard chemoradiation approaches has improved treatment responses. However, the basis for the limited efficacy of EGFR inhibitors in HNC is incompletely understood. G-protein-coupled receptors (GPCR) have been shown to be overexpressed in HNC where GPCR activation induces HNC growth via both EGFR-dependent and -independent pathways. We hypothesized that targeting GPCR-induced EGFR-independent signaling would improve the efficacy of EGFR inhibition.

EXPERIMENTAL DESIGN

Using a high-throughput phosphoproteome array, we identified proteins that were phosphorylated in HNC cells where EGFR expression was downmodulated by RNA interference (RNAi) in the presence or absence of a GPCR ligand. We confirmed the findings from the array by Western blotting followed by in vitro and in vivo phenotypic assays.

RESULTS

p70S6K phosphorylation was elevated approximately sixfold in EGFR siRNA-transfected cells treated with a GPCR ligand. In addition to RNAi-mediated EGFR downmodulation, GPCR-mediated phosphorylation of p70S6K was modestly increased by EGFR inhibitor cetuximab approved by the Food and Drug Administration. Biopsies from cetuximab-treated patients also displayed increased phospho-p70S6K staining compared with pretreatment biopsies. HNC cells were growth inhibited by both genetic and pharmacologic p70S6K targeting strategies. Furthermore, p70S6K targeting in combination with cetuximab resulted in enhanced antitumor effects in both in vitro and in vivo HNC models.

CONCLUSIONS

These results indicate that increased phosphorylation of p70S6K in cetuximab-treated patients may be due to increased GPCR signaling. Therefore, the addition of p70S6K targeting strategies may improve treatment responses to EGFR inhibition.

Receptor-tyrosine-kinase-targeted therapies for head and neck cancer

Molecular therapeutics for treating epidermal growth factor receptor-(EGFR-) expressing cancers are a specific method for treating cancers compared to general cell loss with standard cytotoxic therapeutics. However, the finding that resistance to such therapy is common in clinical trials now dampens the initial enthusiasm over this targeted treatment. Yet an improved molecular understanding of other receptor tyrosine kinases known to be active in cancer has revealed a rich network of cross-talk between receptor pathways with a key finding of common downstream signaling pathways. Such cross talk may represent a key mechanism for resistance to EGFR-directed therapy. Here we review the interplay between EGFR and Met and the type 1 insulin-like growth factor receptor (IGF-1R) tyrosine kinases, as well as their contribution to anti-EGFR therapeutic resistance in the context of squamous cell cancer of the head and neck, a tumor known to be primarily driven by EGFR-related oncogenic signals.

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.

Insulin-like growth factor-1 receptor inhibition overcomes gefitinib resistance in mucinous lung adenocarcinoma

The appropriate selection of patients is a major challenge in the treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs). Prospective trials in adenocarcinoma demonstrated that the mucinous subtype presents a poorer outcome under EGFR-TKI treatment than the non-mucinous subtype. Our aim was to determine the molecular characteristics associated with resistance to EGFR-TKIs in mucinous and non-mucinous adenocarcinoma. Eighty adenocarcinoma samples, including 34 tumours from patients treated with gefitinib in a phase II clinical trial (IFCT0401), were classified as mucinous (n = 32) or non-mucinous (n = 48) adenocarcinoma. We demonstrated that four biological markers were differentially expressed between the two subtypes: mucinous tumours that overexpressed IGF1R (p < 0.0001) and amphiregulin (p = 0.004) with a tendency for more frequent KRAS mutations, in contrast to non-mucinous tumours that overexpressed EGFR (p < 0.0001) and TTF-1 (p < 0.0001) with more frequent EGFR mutations (p = 0.037). Higher IGF1R (p = 0.02) and lower TTF-1 (p = 0.02) expression was associated with disease progression under gefitinib treatment. We observed in vitro cross-talk between EGFR and IGF1R signalling pathways in gefitinib-resistant H358 mucinous cells. Anti-amphiregulin siRNAs and anti-IGF1R treatments sensitized the H358 cells to gefitinib-induced apoptosis with additive effects, suggesting that these treatments could overcome the resistance of mucinous tumours to EGFR-TKIs, including those with KRAS mutation. Our results highlighted that mucinous and non-mucinous adenocarcinoma subtypes are different entities with different therapeutic responses to EGFR-TKIs. These data will foster the development of therapeutic strategies for treating adenocarcinoma with mucinous component.

Specific targeting of insulin-like growth factor 1 receptor signaling in human estrogen dependent breast cancer cell by a novel tyrosine-based benzoxazepine derivative

The present study sought to investigate the in vitro and in vivo effects of a tyrosine-based benzoxazepine, 4-[4-(toluene-4-sulfonyl)-2,3,4,5-tetrahydro-benzo[f][1,4]oxazepin-3-ylmethyl]-phenol) [THBP] in human breast cancer cells, with a focus on determining its molecular target. THBP had growth inhibitory effect on MCF-7 and MDA-MD-231 cells. At IC(50) value (∼20 μM), THBP resulted in G1 arrest, decrease in cyclin D1 levels and induction of apoptosis of MCF-7 cells. Mechanistically, activation of caspase 8 contributes critically to the induction of apoptotic cell death as copresence of selective inhibition of caspase 8 effectively abrogates the cytotoxic effect of THBP in MCF-7 cells. Further, THBP increased pro-apoptotic protein, Bax; decreased anti-apoptotic protein, Bcl-2; and decreased mitochondrial membrane potential in MCF-7 cells, indicating involvement of an intrinsic pathway of apoptosis following caspase 8 activation. Out of the various growth factors/hormones, THBP selectively abrogated increased viability of MCF-7 cells by insulin-like growth factor 1 (IGF-1). Molecular docking studies revealed that THBP occupied the ATP binding pocket of IGF-1 receptor (IGF-1R). Accordingly THBP was found to inhibit IGF-1-induced phosphorylation of IGF-1R and insulin receptor substrate-1 (IRS-1) without inhibiting insulin signaling in MCF-7 cells. In athymic nude mice, compared with vehicle, THBP treatment significantly reduced the growth of MCF-7 xenograft tumors through inhibition of cancer cell proliferation as well as promotion of cell death that correlated with reduced phospho-IGF-1R levels. We suggest that interfering with the IGF-1R signaling by the benzoxazepine THBP offers a novel and selective therapeutic strategy for estrogen receptor-positive, postmenopausal breast cancer patients.

A stable IgG-like bispecific antibody targeting the epidermal growth factor receptor and the type I insulin-like growth factor receptor demonstrates superior anti-tumor activity

The epidermal growth factor receptor (EGFR) and the type I insulin-like growth factor receptor (IGF-1R) are two cell surface receptor tyrosine kinases known to cooperate to promote tumor progression and drug resistance. Combined blockade of EGFR and IGF-1R has shown improved anti-tumor activity in preclinical models. Here, we report the characterization of a stable IgG-like bispecific antibody (BsAb) dual-targeting EGFR and IGF-1R that was developed for cancer therapy. The BsAb molecule (EI-04), constructed with a stability-engineered single chain variable fragment (scFv) against IGF-1R attached to the carboxyl-terminus of an IgG against EGFR, displays favorable biophysical properties for biopharmaceutical development. Biochemically, EI-04 bound to human EGFR and IGF-1R with sub nanomolar affinity, co-engaged the two receptors simultaneously, and blocked the binding of their respective ligands with similar potency compared to the parental monoclonal antibodies (mAbs). In tumor cells, EI-04 effectively inhibited EGFR and IGF-1R phosphorylation, and concurrently blocked downstream AKT and ERK activation, resulting in greater inhibition of tumor cell growth and cell cycle progression than the single mAbs. EI-04, likely due to its tetravalent bispecific format, exhibited high avidity binding to BxPC3 tumor cells co-expressing EGFR and IGF-1R, and consequently improved potency at inhibiting IGF-driven cell growth over the mAb combination. Importantly, EI-04 demonstrated enhanced in vivo anti-tumor efficacy over the parental mAbs in two xenograft models, and even over the mAb combination in the BxPC3 model. Our data support the clinical investigation of EI-04 as a superior cancer therapeutic in treating EGFR and IGF-1R pathway responsive tumors.

Advanced computational biology methods identify molecular switches for malignancy in an EGF mouse model of liver cancer

The molecular causes by which the epidermal growth factor receptor tyrosine kinase induces malignant transformation are largely unknown. To better understand EGFs' transforming capacity whole genome scans were applied to a transgenic mouse model of liver cancer and subjected to advanced methods of computational analysis to construct de novo gene regulatory networks based on a combination of sequence analysis and entrained graph-topological algorithms. Here we identified transcription factors, processes, key nodes and molecules to connect as yet unknown interacting partners at the level of protein-DNA interaction. Many of those could be confirmed by electromobility band shift assay at recognition sites of gene specific promoters and by western blotting of nuclear proteins. A novel cellular regulatory circuitry could therefore be proposed that connects cell cycle regulated genes with components of the EGF signaling pathway. Promoter analysis of differentially expressed genes suggested the majority of regulated transcription factors to display specificity to either the pre-tumor or the tumor state. Subsequent search for signal transduction key nodes upstream of the identified transcription factors and their targets suggested the insulin-like growth factor pathway to render the tumor cells independent of EGF receptor activity. Notably, expression of IGF2 in addition to many components of this pathway was highly upregulated in tumors. Together, we propose a switch in autocrine signaling to foster tumor growth that was initially triggered by EGF and demonstrate the knowledge gain form promoter analysis combined with upstream key node identification.

Molecular targets of phytochemicals for cancer prevention

Although successful for a limited number of tumour types, the efficacy of cancer therapies, especially for late-stage disease, remains poor overall. Many have argued that this could be avoided by focusing on cancer prevention, which has now entered the arena of targeted therapies. During the process of identifying preventive agents, dietary phytochemicals, which are thought to be safe for human use, have emerged as modulators of key cellular signalling pathways. The task now is to understand how these chemicals perturb these pathways by modelling their interactions with their target proteins.