In vivo effects of the human type I insulin-like growth factor receptor antibody A12 on androgen-dependent and androgen-independent xenograft human prostate tumors

Interactions between androgen and IGF1 axes in prostate tumorigenesis

Androgen signalling through the androgen receptor (AR) is essential for prostate tumorigenesis. However, androgen signalling pathways also interact with other growth factor-mediated signalling pathways to regulate the prostatic cell cycle, differentiation, apoptosis and proliferation in the initiation and progression of prostate cancer. Insulin-like growth factor 1 (IGF1) is one of the most prominent growth factors in prostate tumorigenesis. Clinical and experimental evidence has demonstrated that IGF1 signalling supports both androgen-dependent and androgen-independent prostate tumorigenesis, suggesting that improved understanding of the interactions between the IGF1 and androgen axes might aid the development of new therapeutic strategies. Available data have shown a dynamic role of androgen-AR signalling in the activation of IGF1-signalling pathways by augmenting transcription of the IGF1 receptor in prostatic basal epithelial cells and by increasing IGF1 secretion through the suppression of IGF-binding protein 3 expression in prostatic stromal cells. In turn, IGF1 stimulates Wnt-β-catenin signalling in prostatic basal progenitors to promote prostatic oncogenic transformation and prostate cancer development. These findings highlight the cooperative, autocrine and paracrine interactions that underlie the oncogenic effects of androgens and IGF1 and open up new opportunities for therapeutic targeting.

Emerging Role of IGF-1 in Prostate Cancer: A Promising Biomarker and Therapeutic Target

Prostate cancer (PCa) is a highly heterogeneous disease driven by gene alterations and microenvironmental influences. Not only enhanced serum IGF-1 but also the activation of IGF-1R and its downstream signaling components has been increasingly recognized to have a vital driving role in the development of PCa. A better understanding of IGF-1/IGF-1R activity and regulation has therefore emerged as an important subject of PCa research. IGF-1/IGF-1R signaling affects diverse biological processes in cancer cells, including promoting survival and renewal, inducing migration and spread, and promoting resistance to radiation and castration. Consequently, inhibitory reagents targeting IGF-1/IGF-1R have been developed to limit cancer development. Multiple agents targeting IGF-1/IGF-1R signaling have shown effects against tumor growth in tumor xenograft models, but further verification of their effectiveness in PCa patients in clinical trials is still needed. Combining androgen deprivation therapy or cytotoxic chemotherapeutics with IGF-1R antagonists based on reliable predictive biomarkers and developing and applying novel agents may provide more desirable outcomes. This review will summarize the contribution of IGF-1 signaling to the development of PCa and highlight the relevance of this signaling axis in potential strategies for cancer therapy.

Systematic review of antitumour efficacy and mechanism of metformin activity in prostate cancer models

Metformin, the first line pharmacotherapy for type 2 diabetes has demonstrated favourable effects in prostate cancer (PCa) across a range of studies evaluating PCa patient outcomes amongst metformin users. However, a lack of rigorously conducted prospective studies has stalled clinical use in this setting. Despite multiple studies evaluating the mechanisms underpinning antitumour effects of metformin in PCa, to date, no reviews have compared these findings. This systematic review and meta-analysis consolidates the mechanisms accounting for the antitumour effect of metformin in PCa and evaluates the antitumour efficacy of metformin in preclinical PCa studies. Data were obtained through Medline and EMBASE, extracted by two independent assessors. Risk of bias was assessed using the TOXR tool. Meta-analysis compared in vivo reductions of PCa tumour volume with metformin. In total, 447 articles were identified with 80 duplicates, and 261 articles excluded based on eligibility criteria. The remaining 106 articles were assessed and 71 excluded, with 35 articles included for systematic review, and eight included for meta-analysis. The mechanisms of action of metformin regarding tumour growth, viability, migration, invasion, cell metabolism, and activation of signalling cascades are individually discussed. The mechanisms by which metformin inhibits PCa cell growth are multimodal. Metformin regulates expression of multiple proteins/genes to inhibit cellular proliferation, cell cycle progression, and cellular invasion and migration. Published in vivo studies also conclusively demonstrate that metformin inhibits PCa growth. This highlights the potential of metformin to be repurposed as an anticancer agent, warranting further investigation of metformin in the setting of PCa.

A phase II study of the insulin-like growth factor type I receptor inhibitor IMC-A12 in patients with metastatic uveal melanoma

Uveal melanoma is a rare and aggressive malignancy and up to half of all patients will develop metastatic disease despite the effective treatment of the primary tumor. Insulin-like growth factors I/II play a fundamental role in the cell migration, proliferation, and apoptosis. IMC-A12, a mAb specifically targets insulin-like growth factor type I receptor, has shown promise in preclinical studies. We performed a multicenter phase II study for patients with metastatic uveal melanoma administered IMC-A12 10 mg/kg IV every two weeks until disease progression or unacceptable toxicity. The primary endpoint was objective response (proportion of patients with complete or partial response), and secondary endpoints were disease control rate, progression-free survival, and overall survival. A total of 18 patients enrolled in this study (10 males and eight females) with a median age. Ten patients (55%) had stable disease, seven patients (38%) had progression as best overall response. No partial response or complete response was observed; however, the disease control rate, defined as complete response + partial response + stable disease ≥3 months, was 50%. Median progression-free survival was 3.1 months, and median overall survival was 13.8 months. Adverse events of any grade occurred in 13 patients (72.2%). Treatment-related grade 3 adverse events were rare, and there were no grade 4 or 5 related adverse events. IMC-A12 was very well tolerated, however, showed limited clinical activity in uveal melanoma as a single agent. Due to its low toxicity profile it could be studied in combination with other pathway-specific agents.

Survival outcomes and risk group validation from SWOG S0925: a randomized phase II study of cixutumumab in new metastatic hormone-sensitive prostate cancer

BACKGROUND

Cixutumumab, a monoclonal antibody targeting insulin-like growth factor I receptor, did not improve undetectable prostate-specific antigen (PSA) rate at 28 weeks when combined with androgen deprivation in the randomized phase II SWOG S0925 trial for patients with new metastatic hormone-sensitive prostate cancer. We now present mature survival analyses, along with pre-specified secondary and exploratory endpoints.

METHODS

We randomized 210 patients to androgen deprivation with or without cixutumumab, 105 per treatment arm. We used Kaplan-Meier curves to analyze overall survival, radiographic progression-free survival, and castration resistance-free survival by treatment arm, disease volume, and risk group. We explored differences in survival by treatment arm via covariate-adjusted Cox proportional hazards models adjusted for disease volume and risk.

RESULTS

No difference was seen between treatment arms in overall survival (HR 1.01 [0.70-1.45]; p = 0.97), radiographic progression-free survival (HR 1.17 [0.85-1.60]; p = 0.35), or castration resistance-free survival (HR 1.02 [0.75-1.41]; p = 0.88). At baseline, 105/198 (53.0%) patients had high-risk features and 119/210 (56.7%) had high-volume disease; 16.7% of patients had discordant classifications of high or low category for risk and volume. Adjusting for risk or volume yielded no differences in overall survival between arms. Inferior survival was observed in high-risk (HR 1.89 [1.29-2.80]; p = 0.001) and high-volume (HR 2.75 [1.84-4.10]; p < 0.0001) disease. Disease volume was a better fit to survival data than risk group (AIC 878.3 vs. 889.2). Compared to patients achieving undetectable PSA at 28 weeks, inferior survival was observed in patients whose PSA was >0.2 to ≤4.0 ng/mL (HR 3.72 [1.99-6.95]; p < 0.0001) or >4.0 ng/mL (HR 7.13 [4.24-11.9]; p < 0.0001).

CONCLUSIONS

In new metastatic hormone-sensitive prostate cancer, addition of cixutumumab to androgen deprivation did not improve survival. Baseline risk and disease volume carried prognostic value for this distinct trial population, although disease volume added more prognostic information. PSA treatment response was a strong intermediate endpoint for survival.

The role of insulin-like growth factors in the development of prostate cancer

INTRODUCTION

Preclinical, clinical, and population studies have provided robust evidence for an important role for the insulin-like growth factor (IGF) system in the development of prostate cancer.

AREAS COVERED

An overview of the IGF system is provided. The evidence implicating the IGF system in the development of prostate cancer is summarized. The compelling evidence culminated in a number of clinical trials of agents targeting the system; the reasons for the failure of these trials are discussed.

EXPERT OPINION

Clinical trials of agents targeting the IGF system in prostate cancer were terminated due to limited objective clinical responses and are unlikely to be resumed unless a convincing predictive biomarker is identified that would enable the selection of likely responders. The aging population and increased screening will lead to greater diagnosis of prostate cancer. Although the vast majority will be indolent disease, the epidemics of obesity and diabetes will increase the proportion that progress to clinical disease. The increased population of worried men will result in more trials aimed to reduce the risk of disease progression; actual clinical endpoints will be challenging and the IGFs remain the best intermediate biomarkers to indicate a response that could alter the course of disease.

Therapeutic Targeting of the IGF Axis

The insulin like growth factor (IGF) axis plays a fundamental role in normal growth and development, and when deregulated makes an important contribution to disease. Here, we review the functions mediated by ligand-induced IGF axis activation, and discuss the evidence for the involvement of IGF signaling in the pathogenesis of cancer, endocrine disorders including acromegaly, diabetes and thyroid eye disease, skin diseases such as acne and psoriasis, and the frailty that accompanies aging. We discuss the use of IGF axis inhibitors, focusing on the different approaches that have been taken to develop effective and tolerable ways to block this important signaling pathway. We outline the advantages and disadvantages of each approach, and discuss progress in evaluating these agents, including factors that contributed to the failure of many of these novel therapeutics in early phase cancer trials. Finally, we summarize grounds for cautious optimism for ongoing and future studies of IGF blockade in cancer and non-malignant disorders including thyroid eye disease and aging.

Effect of docetaxel on the regulation of proliferation and apoptosis of human prostate cancer cells

Prostate cancer is a common type of malignancy. Given the complexity of prostate cancer and the pressing challenge of chemoresistance, the current study was conducted to investigate the effect of docetaxel (Doc) on androgen receptor (AR)‑dependent and AR‑independent prostate cancers cells. Subsequent experiments were designed to explore the mechanism underlying the Doc‑induced apoptosis. Three different human prostate cancer cell lines, namely PC‑3, LNCaP and DU‑145, were exposed to various concentrations of Doc. The cytotoxic effects of Doc were evaluated by an MTT assay, while apoptosis and cell cycle distribution were determined by flow cytometric analysis of cells stained with Annexin V‑FITC and propidium iodide. Western blot assay was also used to measure the protein levels of B‑cell lymphoma 2 (Bcl‑2), Bcl‑2‑associated death promoter (Bad), total protein kinase B (Akt), phospho‑Akt and caspase‑3/9. Doc induced cytotoxicity in all three cell lines in a dose‑dependent manner. The half maximal inhibitory concentration values for the effect of Doc on PC‑3, DU‑145 and LNCaP cells were 3.72, 4.46 and 1.13 nM, respectively. Furthermore, the results indicated a significant difference in Doc sensitivity between AR‑dependent and AR‑independent prostate cancer cells. Evaluation of key gene expression at protein levels revealed a notable decrease in antiapoptotic Bcl‑2 and p‑Akt levels, along with a significant increase in pro‑apoptotic Bad, caspase‑3 and caspase‑9 levels. Therefore, Doc may induce cell apoptosis in prostate cancer via various pathways.

Dietary Carcinogens and DNA Adducts in Prostate Cancer

Prostate cancer (PC) is the most commonly diagnosed non-cutaneous cancer and the second leading cause of cancer-related to death in men. The major risk factors for PC are age, family history, and African American ethnicity. Epidemiological studies have reported large geographical variations in PC incidence and mortality, and thus lifestyle and dietary factors influence PC risk. High fat diet, dairy products, alcohol and red meats, are considered as risk factors for PC. This book chapter provides a comprehensive, literature-based review on dietary factors and their molecular mechanisms of prostate carcinogenesis. A large portion of our knowledge is based on epidemiological studies where dietary factors such as cancer promoting agents, including high-fat, dairy products, alcohol, and cancer-initiating genotoxicants formed in cooked meats have been evaluated for PC risk. However, the precise mechanisms in the etiology of PC development remain uncertain. Additional animal and human cell-based studies are required to further our understandings of risk factors involved in PC etiology. Specific biomarkers of chemical exposures and DNA damage in the prostate can provide evidence of cancer-causing agents in the prostate. Collectively, these studies can improve public health research, nutritional education and chemoprevention strategies.

Phase II randomized trial of carboplatin, paclitaxel, bevacizumab with or without cixutumumab (IMC-A12) in patients with advanced non-squamous, non-small-cell lung cancer: a trial of the ECOG-ACRIN Cancer Research Group (E3508)

Background

Cixutumumab is a fully human IgG1 monoclonal antibody to the insulin-like growth factor type I receptor that can potentially reverse resistance and enhance the efficacy of chemotherapy.

Methods

Bevacizumab-eligible patients with stage IV or recurrent non-squamous, non-small-cell lung cancer and good performance status were randomized to receive standard doses of paclitaxel, carboplatin, and bevacizumab to a maximum of six cycles followed by bevacizumab maintenance (CPB) until progression (arm A) or CPB plus cixutumumab 6 mg/kg i.v. weekly (arm B).

Results

Of 175 patients randomized, 153 were eligible and treated (78 in arm A; 75 in arm B). The median progression-free survival was 5.8 months (95% CI 5.4-7.1) in arm A versus 7 months (95% CI 5.7-7.6) in arm B (P = 0.33); hazard ratio 0.92 (95% CI 0.65-1.31). Objective response was 46.2% versus 58.7% in arm A versus arm B (P = 0.15). The median overall survival was 16.2 months in arm A versus 16.1 months in arm B (P = 0.95). Grade 3/4 neutropenia and febrile neutropenia, thrombocytopenia, fatigue, and hyperglycemia were increased with cixutumumab.

Conclusions

The addition of cixutumumab to CPB increased toxicity without improving efficacy and is not recommended for further development in non-small-cell lung cancer. Both treatment groups had longer OS than historical controls which may be attributed to several factors, and emphasizes the value of a comparator arm in phase II trials.

ClinicalTrials.gov Identifier

NCT00955305.

Does milk intake promote prostate cancer initiation or progression via effects on insulin-like growth factors (IGFs)? A systematic review and meta-analysis

PURPOSE

To establish whether the association between milk intake and prostate cancer operates via the insulin-like growth factor (IGF) pathway (including IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3).

METHODS

Systematic review, collating data from all relevant studies examining associations of milk with IGF, and those examining associations of IGF with prostate cancer risk and progression. Data were extracted from experimental and observational studies conducted in either humans or animals, and analyzed using meta-analysis where possible, with summary data presented otherwise.

RESULTS

One hundred and seventy-two studies met the inclusion criteria: 31 examining the milk-IGF relationship; 132 examining the IGF-prostate cancer relationship in humans; and 10 animal studies examining the IGF-prostate cancer relationship. There was moderate evidence that circulating IGF-I and IGFBP-3 increase with milk (and dairy protein) intake (an estimated standardized effect size of 0.10 SD increase in IGF-I and 0.05 SD in IGFBP-3 per 1 SD increase in milk intake). There was moderate evidence that prostate cancer risk increased with IGF-I (Random effects meta-analysis OR per SD increase in IGF-I 1.09; 95% CI 1.03, 1.16; n = 51 studies) and decreased with IGFBP-3 (OR 0.90; 0.83, 0.98; n = 39 studies), but not with other growth factors. The IGFBP-3 -202A/C single nucleotide polymorphism was positively associated with prostate cancer (pooled OR for A/C vs. AA = 1.22; 95% CI 0.84, 1.79; OR for C/C vs. AA = 1.51; 1.03, 2.21, n = 8 studies). No strong associations were observed for IGF-II, IGFBP-1 or IGFBP-2 with either milk intake or prostate cancer risk. There was little consistency within the data extracted from the small number of animal studies. There was additional evidence to suggest that the suppression of IGF-II can reduce tumor size, and contradictory evidence with regards to the effect of IGFBP-3 suppression on tumor progression.

CONCLUSION

IGF-I is a potential mechanism underlying the observed associations between milk intake and prostate cancer risk.

Crk II silencing down-regulates IGF-IR and inhibits migration and invasion of prostate cancer cells

Crk (C10 regulator of kinase) adaptor proteins are highly expressed in many types of human cancers and often contribute to aggressive cancer phenotypes. Crk II, a member of CRK family, has been reported to regulate cell migration and metastasis in breast cancer cells. However, its role in other cancer types has not been reported. In this study, we investigated the molecular function of Crk II in prostate cancer (PCa) cells (CWR-22rv1) in vitro and using a mouse tumor model. Results showed that Crk II knockdown by shRNA-mediated silencing (Crk II-shRNA) in the PCa cells significantly inhibited both cancer cell migration and invasion in cell culture study. Crk II-shRNA cancer cells also significantly decreased colony formation in vitro, but had no significant reduction of tumor volume after 4 weeks of cancer cell xenografting in vivo when compared to the scramble control. Interestingly, Crk II-shRNA cancer cells showed a greatly reduced level of insulin-like growth factor 1 receptor (IGF-1R) and decreased signaling of the IGF-1R/PI3K/Akt axis upon IGF-1 ligand stimulation. A close interaction between Crk II and IGF-1R was demonstrated upon co-immunoprecipitation of IGF-1R with Crk II protein. Further, treatment of cells with either proteosomal degradation or protein synthesis inhibitor showed higher proportion of ubiquitin-associated IGF-1R and faster degradation of IGF-1R in Crk II-shRNA cells in comparison with that in the control cancer cells. Taken together, these data suggest that Crk II plays an important role in the regulation of IGF-1R protein stability and affects downstream of IGF-1R signaling pathways. Therefore, targeting Crk-II can block IGF-1R growth signaling and suppress cancer cell invasion and progression.

•

Blocking Crk II inhibited cancer cell migration, invasion, and colony formation.

•

Knockdown Crk II decreased IGF-1R protein and its downstream signaling.

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Crk II knockdown increased ubiquitination and degradation of IGF-1R.

A humanized anti-CD26 monoclonal antibody inhibits cell growth of malignant mesothelioma via retarded G2/M cell cycle transition

Background

Malignant Mesothelioma (MM) is a highly aggressive tumor with poor prognosis. Multimodal treatments and novel molecular targeted therapies against MM are in high demand in order treat this disease effectively. We have developed a humanized monoclonal antibody YS110 against CD26 expressed in 85 % of MM cases. CD26 is thought to be involved in tumor growth and invasion by interacting with collagen and fibronectin, or affecting signal transduction processes.

Methods

We evaluated the direct anti-tumor effect of YS110 against MM cell lines, NCI-H2452 and JMN, and investigated its effects on cell cycle and on the cell cycle regulator molecules. In addition, we investigated synergistic effects of YS110 and anti-tumor agent pemetrexed (PMX) against MM cell line both in vitro and in vivo.

Results

YS110 suppressed the proliferation of NCI-H2452 cells by approximately 20 % in 48 h. Based on cell cycle analysis, percentage of cells in G2/M phase increased 8.0 % on the average after YS110 treatment; in addition, cell cycle regulator p21 cip/waf1 was increased and cyclin B1 was decreased after YS110 treatment. Inhibitory phosphorylation of both cdc2 (Tyr15) and cdc25C (Ser216) were elevated. Furthermore, activating phosphorylation of p38 MAPK (Thr180/Tyr182) and ERK1/2 (Thr202/Tyr204) were augmented at 24 h after YS110 treatment. PMX rapidly induced CD26 expression on cell surface and the treatment with both YS110 and PMX inhibited in vivo tumor growth accompanied by a synergistic reduction in the MIB-1 index.

Conclusion

This is a first report of a novel anti-proliferative mechanism of the humanized anti-CD26 monoclonal antibody YS110, which resulted in G2/M cell cycle delay through regulation of quantity and activity of various cell cycle regulating molecules.

Risk of prostate cancer-specific death in men with baseline metabolic aberrations treated with androgen deprivation therapy for biochemical recurrence

OBJECTIVES

To investigate the associations of host metabolic factors and metabolic syndrome on prostate cancer-specific death (PCSD) and overall survival (OS) in patients treated with androgen deprivation therapy (ADT) for biochemically recurrent disease.

PATIENTS AND METHODS

The analysis included 273 patients with prostate cancer treated with ADT for rising prostate-specific antigen level after surgery or radiotherapy. Patients were assessed for the presence of diabetes, hypertension, dyslipidaemia and obesity before commencing ADT, and Adult Treatment Panel III criteria were used to assess the presence of the composite diagnosis of metabolic syndrome. A competing risks regression model was used to assess associations of time to PCSD with the metabolic conditions, while a multivariable Cox regression model was used to assess associations of OS with metabolic syndrome and metabolic conditions.

RESULTS

During a median follow-up of 11.6 years, 157 patients (58%) died, of whom 58 (21%) died from prostate cancer. At the start of ADT the median (range) patient age was 74 (46-92) years and the median PSA level was 3.0 ng/mL. Metabolic syndrome was observed in 31% of patients; hypertension (68%) and dyslipidaemia (47%) were the most common metabolic conditions. No association of PCSD and metabolic syndrome status was observed. Patients with hypertension tended to have a higher cumulative incidence of PCSD than those without hypertension (sub-distribution hazard ratio [HR] 1.59, 95% confidence interval [CI] 0.89, 2.84; P = 0.11) although the difference was not statistically significant. Patients with metabolic syndrome had an increased risk of death from all causes (HR 1.56, 95% CI 1.07, 2.29; P = 0.02) when compared with patients without metabolic syndrome, as did patients with hypertension (HR 1.72, 95% CI 1.18, 2.49; P = 0.004).

CONCLUSIONS

No association of PCSD and metabolic syndrome was observed in this cohort of men receiving ADT for biochemically recurrent prostate cancer. Metabolic syndrome was associated with an increased risk of death from all causes and a similar effect was also observed for patients with prostate cancer with hypertension alone.

A randomised non-comparative phase II trial of cixutumumab (IMC-A12) or ramucirumab (IMC-1121B) plus mitoxantrone and prednisone in men with metastatic docetaxel-pretreated castration-resistant prostate cancer

BACKGROUND

Cixutumumab, a human monoclonal antibody (HuMAb), targets the insulin-like growth factor receptor. Ramucirumab is a recombinant HuMAb that binds to vascular endothelial growth factor receptor-2. A non-comparative randomised phase II study evaluated cixutumumab or ramucirumab plus mitoxantrone and prednisone (MP) in metastatic castration-resistant prostate cancer (mCRPC).

PATIENTS AND METHODS

Men with progressive mCRPC during or after docetaxel therapy received mitoxantrone 12 mg/m(2) on day 1 and prednisone 5mg twice daily and were randomised 1:1 to receive either cixutumumab or ramucirumab 6 mg/kg intravenously weekly in a 21-day cycle. Primary end-point was composite progression-free survival (cPFS). Secondary end-points included safety, response, radiographic progression-free survival (PFS) and overall survival (OS). Sample size was based on a 50% increase in median cPFS from 2.6 (MP) to 3.9 months (either combination).

RESULTS

132 men were treated (66 per arm). Median cPFS was 4.1 months (95% confidence interval (CI), 2.2-5.6) for cixutumumab and 6.7 months (95% CI, 4.5-8.3) for ramucirumab. Median time to radiographic progression was 7.5 months for cixutumumab and 10.2 months for ramucirumab, with a median OS of 10.8 and 13.0 months, respectively. Fatigue was the most frequent adverse event (AE). Incidence of most non-haematologic grade 3-4 AEs was <10% on both arms. Grade 3 cardiac dysfunction occurred in 7.6% of patients on ramucirumab.

CONCLUSION

Combinations of cixutumumab or ramucirumab plus MP were feasible and associated with moderate toxicities in docetaxel-pretreated men with mCRPC. Of the two regimens, the ramucirumab regimen is worthy of further testing based on the observed cPFS relative to the historical control.

Clinical and Translational Results of a Phase II, Randomized Trial of an Anti-IGF-1R (Cixutumumab) in Women with Breast Cancer That Progressed on Endocrine Therapy

PURPOSE

This phase II trial evaluated the efficacy and safety of cixutumumab, a human anti-insulin-like growth factor receptor 1 (IGF-1R) monoclonal IgG1 antibody, and explored potential biomarkers in postmenopausal women with hormone receptor-positive breast cancer.

EXPERIMENTAL DESIGN

Patients with hormone receptor-positive breast cancer that progressed on antiestrogen therapy received (2:1 randomization) cixutumumab 10 mg/kg and the same antiestrogen (arm A) or cixutumumab alone (arm B) every 2 weeks (q2w). Primary endpoint was progression-free survival (PFS); secondary endpoints included overall survival (OS) and safety. Correlative analyses of IGF-1R, total insulin receptor (IR), and IR isoforms A (IR-A) and B (IR-B) expression in tumor tissue were explored.

RESULTS

Ninety-three patients were randomized (arm A, n = 62; arm B, n = 31). Median PFS was 2.0 and 3.1 months for arm A and arm B, respectively. Secondary efficacy measures were similar between the arms. Overall, cixutumumab was well tolerated. IGF-1R expression was not associated with clinical outcomes. Regardless of the treatment, lower IR-A, IR-B, and total IR mRNA expression in tumor tissue was significantly associated with longer PFS [IR-A: HR, 2.62 (P = 0.0062); IR-B: HR, 2.21 (P = 0.0202); and total IR: HR, 2.18 (P = 0.0230)] and OS [IR-A: HR, 2.94 (P = 0.0156); IR-B: HR, 2.69 (P = 0.0245); and total IR: HR, 2.72 (P = 0.0231)].

CONCLUSIONS

Cixutumumab (10 mg/kg) with or without antiestrogen q2w had an acceptable safety profile, but no significant clinical efficacy. Patients with low total IR, IR-A, and IR-B mRNA expression levels had significantly longer PFS and OS, independent of the treatment. The prognostic or predictive value of IR as a biomarker for IGF-1R-targeted therapies requires further validation.

A novel calcium-dependent mechanism of acquired resistance to IGF-1 receptor inhibition in prostate cancer cells

Inhibition of the mitogenic insulin-like growth factor receptor 1 (IGF-1R) signaling axis is a compelling treatment strategy for prostate cancer. Combining the IGF-1R inhibitor ganitumab (formerly AMG 479) with standard of care androgen-deprivation therapy greatly delays prostate cancer recurrence in xenograft models; however, a significant proportion of these tumors ultimately acquire resistance to ganitumab. Here we describe the development of a stable and reproducible ganitumab-resistant VCaP human prostate cancer cell derivative termed VCaP/GanR to investigate the mechanism of acquired resistance to IGF-1R inhibition. Unlike parental VCaP, VCaP/GanR did not undergo apoptosis following ganitumab treatment. VCaP/GanR did not express increased levels of IGF-1R, insulin receptor, or phospho-AKT compared to parental VCaP. VCaP/GanR exhibited increased levels of phospho-S6 indicative of increased mTOR activity. However, acquired resistance to ganitumab was not dependent on increased mTOR activity in VCaP/GanR. Phospho-proteomic arrays revealed alterations in several calcium-regulated signaling components in VCaP/GanR compared to VCaP. Reduction of intracellular calcium using cell-permeable calcium-specific chelators restored ganitumab sensitivity to VCaP/GanR through inhibition of cell-cycle progression. These data suggest a new mechanism of resistance to IGF-1R inhibition involving calcium-mediated proliferation effects. Such pathways should be considered in future clinical studies of IGF-1R inhibitors in prostate cancer.

Chemotherapy and target therapy for hepatocellular carcinoma: New advances and challenges

Primary liver cancer is one of the commonest causes of death. Hepatocellular carcinoma (HCC) accounts for 90% of primary liver cancers. For patients with unresectable or metastatic HCC, conventional chemotherapy is of limited or no benefit. Sorafenib is the only systemic treatment to demonstrate a statistically significant but modest overall survival benefit, leading to an era of targeted agents. Many clinical trials of targeted drugs have been carried out with many more in progress. Some drugs like PTK787 showed potential benefits in the treatment of HCC. Despite these promising breakthroughs, patients with HCC still have a dismal prognosis. Recently, both a phase III trial of everolimus and a phase II clinical trial of trebananib failed to demonstrate effective antitumor activity in advanced HCC. Sorafenib still plays a pivotal role in advanced HCC, leading to further explorations to exert its maximum efficacy. Combinations targeted with chemotherapy or transarterial chemoembolization is now being tested and might bring about advances. New targeted agents such as mammalian target of rapamycin inhibitors are under investigation, as well as further exploration of the mechanism of hepatocarcinogenesis.

GSK1838705A, an insulin-like growth factor-1 receptor/insulin receptor inhibitor, induces apoptosis and reduces viability of docetaxel-resistant prostate cancer cells both in vitro and in vivo

Prostate cancer is the leading malignancy and the second most common cause of cancer-related death in men. Despite high cure rates with surgery and/or radiation, 30%-40% of patients eventually develop advanced cancer. Docetaxel is one of the most effective and well established chemotherapeutic agents for prostate cancer. However, docetaxel resistance often develops within months. Combination therapies have been proposed to improve the therapeutic efficacy of docetaxel in prostate cancer, and there is an urgent need to identify agents that are effective for treatment of the disease, especially docetaxel-resistant prostate cancer. In this work, we investigated the activity of GSK1838705A, a potent insulin-like growth factor-1 receptor (IGF1R)/insulin receptor (IR) inhibitor, in prostate cancer, especially docetaxel-resistant prostate cancer. We found that GSK1838705A could effectively reduce the viability of both docetaxel-sensitive and docetaxel-resistant prostate cancer cells. GSK1838705A induced marked apoptosis in docetaxel-resistant cells, and also dramatically inhibited migration of these cells. Further, GSK1838705A significantly inhibited phosphorylation of IGF1R/IR. Importantly, GSK1838705A significantly suppressed docetaxel-resistant PC-3R tumor growth in vivo. This is the first study of GSK1838705A in prostate cancer. Our results indicate that GSK1838705A is a promising compound for the treatment of prostate cancer, especially for those who develop resistance to docetaxel, and might shed new light on treatment for prostate cancer.

Metformin inhibits the proliferation of human prostate cancer PC-3 cells via the downregulation of insulin-like growth factor 1 receptor

Metformin is a biguanide drug that is widely used for the treatment of type 2 diabetes. Recent studies have shown that metformin inhibits cancer cell proliferation and tumor growth both in vitro and in vivo. The anti-tumor mechanisms of metformin include activation of the AMP-activated protein kinase/mTOR pathway and direct inhibition of insulin/insulin-like growth factor (IGF)-mediated cellular proliferation. However, the anti-tumor mechanism in prostate cancer remains unclear. Because activation of the IGF-1 receptor (IGF-1R) is required for prostate cell proliferation, IGF-1R inhibitors may be of therapeutic value. Accordingly, we examined the effects of metformin on IGF-1R signaling in prostate cancer cells. Metformin significantly inhibited PC-3 cell proliferation, migration, and invasion. IGF-1R mRNA expression decreased significantly after 48 h of treatment, and IGF-1R protein expression decreased in a similar manner. IGF-1R knockdown by siRNA transfection led to inhibited proliferation, migration and invasion of PC-3 cells. IGF-1 activated both ERK1/2 and Akt, but these effects were attenuated by metformin treatment. In addition, intraperitoneal treatment with metformin significantly reduced tumor growth and IGF-1R mRNA expression in PC-3 xenografts. Our results suggest that metformin is a potent inhibitor of the IGF-1/IGF-1R system and may be beneficial in prostate cancer treatment.

SWOG S0925: A Randomized Phase II Study of Androgen Deprivation Combined With Cixutumumab Versus Androgen Deprivation Alone in Patients With New Metastatic Hormone-Sensitive Prostate Cancer

PURPOSE

Cixutumumab, formerly IMC-A12, is a recombinant human monoclonal immunoglobulin G1 antibody that targets insulin-like growth factor I receptor (IGF-IR). Cixutumumab was synergistic with castration in a hormone-sensitive prostate cancer xenograft model.

PATIENTS AND METHODS

Patients with new metastatic prostate cancer were randomly assigned within 30 days of initiating androgen deprivation (AD) to cixutumumab added to a luteinizing hormone-releasing hormone agonist with bicalutamide versus AD alone. With 180 patients and one-sided alpha of 0.10, there would be 90% power to detect an absolute 20% difference in undetectable prostate-specific antigen (PSA; ≤ 0.2 ng/mL) rate at 28 weeks (relative risk, 1.44); this end point was previously strongly correlated with survival. Secondary end points included the proportion of patients with PSA > 4.0 ng/mL, safety and tolerability, circulating tumor cell (CTC) levels, and seven plasma IGF-IR biomarkers. Fisher's exact test was used for the primary end point, and extended Mantel-Haenszel χ(2) test was used for three PSA response categories.

RESULTS

The trial accrued 210 eligible patients (105 randomly assigned to each arm). Patient characteristics were similar in both arms. Undetectable PSA rate was 42 (40.0%) of 105 for cixutumumab plus AD and 34 (32.3%) of 105 for AD alone (relative risk, 1.24; one-sided P = .16). Lower baseline CTCs (0 v 1 to 4 v ≥ 5/7.5 mL whole blood) were associated with higher rate of PSA response (three categories; P = .036) in 39 evaluable patients. IGF-IR biomarkers were not correlated with PSA outcome, and cixutumumab did not significantly change these biomarker levels.

CONCLUSION

Cixutumumab plus AD did not significantly increase the undetectable PSA rate in men with new metastatic hormone-sensitive prostate cancer. CTCs at baseline may carry prognostic value.

Insulin-like growth factor receptor-1 (IGF-IR) as a target for prostate cancer therapy

Prostate cancer is the most commonly diagnosed cancer in men and is the second leading cause of cancer-related deaths in men each year. Androgen deprivation therapy is and has been the gold standard of care for advanced or metastatic prostate cancer for decades. While this treatment strategy initially shows benefit, eventually tumors recur as castration-resistant prostate cancer for which there are limited treatment options with only modest survival benefit. Upregulation of the insulin-like growth factor receptor type I (IGF-IR) signaling axis has been shown to drive the survival of prostate cancer cells in many studies. As many IGF-IR blockades have been developed, few have been tested preclinically and even fewer have entered clinical trials for prostate cancer therapy. In this review, we will update the most recent preclinical and clinical studies of IGF-IR therapy for prostate cancer. We will also discuss the challenges for IGF-IR targeted therapies to achieve clinical benefit for prostate cancer.

Targeting the insulin-like growth factor pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide. Only 30%-40% of the patients with HCC are eligible for curative treatments, which include surgical resection as the first option, liver transplantation and percutaneous ablation. Unfortunately, there is a high frequency of tumor recurrence after surgical resection and most HCC seem resistant to conventional chemotherapy and radiotherapy. Sorafenib, a multi-tyrosine kinase inhibitor, is the only chemotherapeutic option for patients with advanced hepatocellular carcinoma. Patients treated with Sorafenib have a significant increase in overall survival of about three months. Therefore, there is an urgent need to develop alternative treatments. Due to its role in cell growth and development, the insulin-like growth factor system is commonly deregulated in many cancers. Indeed, the insulin-like growth factor (IGF) axis has recently emerged as a potential target for hepatocellular carcinoma treatment. To this aim, several inhibitors of the pathway have been developed such as monoclonal antibodies, small molecules, antisense oligonucleotides or small interfering RNAs. However recent studies suggest that, unlike most tumors, HCC development requires increased signaling through insulin growth factor II rather than insulin growth factor I. This may have great implications in the future treatment of HCC. This review summarizes the role of the IGF axis in liver carcinogenesis and the current status of the strategies designed to target the IGF-I signaling pathway for hepatocellular carcinoma treatment.

Ganitumab for the treatment of small-cell lung cancer

INTRODUCTION

Small-cell lung cancer (SCLC) accounts for 15 - 20% of all lung cancer cases with few advances made in the systemic treatment and outcomes for extensive-stage SCLC. Many strategies have been evaluated over the past 15 years but none of these approaches has resulted in improved survival rates for patients with SCLC. The IGF receptor (IGF-R) pathway represents a potential actionable target in SCLC patients. Indeed, the IGF-R pathway is involved in cancer development and progression and regulates different vital processes including fetal development, growth and metabolism.

AREAS COVERED

This review provides an overview of insulin inhibitors and the strategies undertaken in recent years with SCLC. Specifically, the article discusses ganitumab and its applicability to SCLC patients.

EXPERT OPINION

At present, there is a lack of therapeutic choices for patients with advanced SCLC. Unfortunately, ganitumab, administered in combination with chemotherapy, demonstrated no clinical activity in patients with SCLC, although it could have utility with other cancers. Furthermore, insulin inhibitors may have some utility in the treatment of SCLC and further studies are required to identify subsets of patients most likely to benefit from their use. The authors also believe that it is important to determine the exact role of the IGF pathway in the pathogenesis and propagation of SCLC.

Growth factor and signaling pathways and their relevance to prostate cancer therapeutics

Treatments that target the androgen axis represent an effective strategy for patients with advanced prostate cancer, but the disease remains incurable and new therapeutic approaches are necessary. Significant advances have recently occurred in our understanding of the growth factor and signaling pathways that are active in prostate cancer. In conjunction with this, many new targeted therapies with sound preclinical rationale have entered clinical development and are being tested in men with castration-resistant prostate cancer. Some of the most relevant pathways currently being exploited for therapeutic gain are HGF/c-Met signaling, the PI3K/AKT/mTOR pathway, Hedgehog signaling, the endothelin axis, Src kinase signaling, the IGF pathway, and angiogenesis. Here, we summarize the biological basis for the use of selected targeted agents and the results from available clinical trials of these drugs in men with prostate cancer.

Insulin-like growth factor 2 silencing restores taxol sensitivity in drug resistant ovarian cancer

Drug resistance is an obstacle to the effective treatment of ovarian cancer. We and others have shown that the insulin-like growth factor (IGF) signaling pathway is a novel potential target to overcome drug resistance. The purpose of this study was to validate IGF2 as a potential therapeutic target in drug resistant ovarian cancer and to determine the efficacy of targeting IGF2 in vivo. An analysis of The Cancer Genome Atlas (TCGA) data in the serous ovarian cancer cohort showed that high IGF2 mRNA expression is significantly associated with shortened interval to disease progression and death, clinical indicators of drug resistance. In a genetically diverse panel of ovarian cancer cell lines, the IGF2 mRNA levels measured in cell lines resistant to various microtubule-stabilizing agents including Taxol were found to be significantly elevated compared to the drug sensitive cell lines. The effect of IGF2 knockdown on Taxol resistance was investigated in vitro and in vivo. Transient IGF2 knockdown significantly sensitized drug resistant cells to Taxol treatment. A Taxol-resistant ovarian cancer xenograft model, developed from HEY-T30 cells, exhibited extreme drug resistance, wherein the maximal tolerated dose of Taxol did not delay tumor growth in mice. Blocking the IGF1R (a transmembrane receptor that transmits signals from IGF1 and IGF2) using a monoclonal antibody did not alter the response to Taxol. However, stable IGF2 knockdown using short-hairpin RNA in HEY-T30 effectively restored Taxol sensitivity. These findings validate IGF2 as a potential therapeutic target in drug resistant ovarian cancer and show that directly targeting IGF2 may be a preferable strategy compared with targeting IGF1R alone.

Phase II randomized study of figitumumab plus docetaxel and docetaxel alone with crossover for metastatic castration-resistant prostate cancer

PURPOSE

Figitumumab is a human IgG2 monoclonal antibody targeting insulin-like growth factor 1 receptor (IGF-1R), with antitumor activity in prostate cancer. This phase II trial randomized chemotherapy-naïve men with progressing castration-resistant prostate cancer to receive figitumumab every 3 weeks with docetaxel/prednisone (Arm A) or docetaxel/prednisone alone (Arm B1). At progression on Arm B1, patients could cross over to the combination (Arm B2).

EXPERIMENTAL DESIGN

Prostate-specific antigen (PSA) response was the primary endpoint; response assessment on the two arms was noncomparative and tested separately; H0 = 0.45 versus HA = 0.60 (α = 0.05; β = 0.09) for Arm A; H0 = 0.05 versus HA = 0.20 (α = 0.05, β = 0.10) for Arm B2. A comparison of progression-free survival (PFS) on Arms A and B1 was planned.

RESULTS

A total of 204 patients were randomized and 199 treated (Arm A: 97; Arm B1: 102); 37 patients crossed over to Arm B2 (median number of cycles started: Arm A = 8; B1 = 8; B2 = 4). PSA responses occurred in 52% and 60% of Arms A and B1, respectively; the primary PSA response objective in Arm A was not met. Median PFS was 4.9 and 7.9 months, respectively (HR = 1.44; 95% confidence interval, 1.06-1.96). PSA response rate was 28% in Arm B2. The figitumumab combination appeared more toxic, with more treatment-related grade 3/4 adverse events (75% vs. 56%), particularly hyperglycemia, diarrhea, and asthenia, as well as treatment-related serious adverse events (41% vs. 15%), and all-causality grade 5 adverse events (18% vs. 8%).

CONCLUSION

IGF-1R targeting may merit further evaluation in this disease in selected populations, but combination with docetaxel is not recommended.

A phase II study of cixutumumab (IMC-A12, NSC742460) in advanced hepatocellular carcinoma

BACKGROUND & AIMS

IGF-IR is implicated in hepatic carcinogenesis. This and preliminary evidence of biological activity of anti-IGF-1R monoclonal antibody cixutumumab in phase I trials prompted this phase II study.

METHODS

Patients with advanced HCC, Child-Pugh A-B8, received cixutumumab 6mg/kg weekly, in a Simon two-stage design study, with the primary endpoints being 4-month PFS and RECIST-defined response rate. Tissue and circulating markers plus different HCC scoring systems were evaluated for correlation with PFS and OS.

RESULTS

As a result of pre-specified futility criteria, only stage 1 was accrued: N=24: median age 67.5 years (range 49-83), KPS 80% (70-90%), 20 males (83%), 9 stage III (37%)/15 stage IV (63%), 18 Child-Pugh A (75%), 11 HBV (46%)/10 HCV (42%)/11 alcoholic cirrhosis (46%)/2 NASH (8%), 11 (46%) diabetic. Median number of doses: 7 (range 1-140). Grade 3/4 toxicities >10% included: diabetes, elevated liver function tests, hyponatremia, and lymphopenia. Four-month PFS was 30% (95% CI 13-48), and there were no objective responses. Median overall survival was 8 months (95% CI 5.8-14). IGF-R1 staining did not correlate with outcome. Elevated IGFBP-1 correlated with improved PFS (1.2 [95% CI 1-1.4]; p 0.009) and OS (1.2 [95% CI 1.1-1.4]; p 0.003).

CONCLUSIONS

Cixutumumab monotherapy did not have clinically meaningful activity in this unselected HCC population. Grade 3-4 hyperglycemia occurred in 46% of patients. Elevated IGFBP-1 correlated with improved PFS and OS.

Preclinical efficacy of growth hormone-releasing hormone antagonists for androgen-dependent and castration-resistant human prostate cancer

Advanced hormone-sensitive prostate cancer responds to androgen-deprivation therapy (ADT); however, therapeutic options for recurrent castration-resistant disease are limited. Because growth hormone-releasing hormone (GHRH) and GHRH receptor (GHRH-R) are regulated in an autocrine fashion in prostate cancer, inhibition of GHRH-R represents a compelling approach to treatment. We investigated the effects of the latest series of improved, highly potent GHRH antagonists--MIA-602, MIA-606, and MIA-690--on the growth of androgen-dependent as well as castration-resistant prostate cancer (CRPC) cells in vitro and in vivo. GHRH-R and its splice variant, SV1, were present in 22Rv1, LNCaP, and VCaP human prostate cancer cell lines. Androgen-dependent LNCaP and VCaP cells expressed higher levels of GHRH-R protein compared with castration-resistant 22Rv1 cells; however, 22Rv1 expressed higher levels of SV1. In vitro, MIA-602 decreased cell proliferation of 22Rv1, LNCaP, and VCaP prostate cancer cell lines by 70%, 61%, and 20%, respectively (all P < 0.05), indicating direct effects of MIA-602. In vivo, MIA-602 was more effective than MIA-606 and MIA-690 and decreased 22Rv1 xenograft tumor volumes in mice by 63% after 3 wk (P < 0.05). No noticeable untoward effects or changes in body weight occurred. In vitro, the VCaP cell line was minimally inhibited by MIA-602, but in vivo, this line showed a substantial reduction in growth of xenografts in response to MIA-602, indicating both direct and systemic inhibitory effects. MIA-602 also further inhibited VCaP xenografts when combined with ADT. This study demonstrates the preclinical efficacy of the GHRH antagonist MIA-602 for treatment of both androgen-dependent and CRPC.

Insulin receptor (IR) and insulin-like growth factor receptor 1 (IGF-1R) signaling systems: novel treatment strategies for cancer

Insulin and insulin-like growth factor (IGF) signaling system, commonly known for fine-tuning numerous biological processes, has lately made its mark as a much sought-after therapeutic targets for diabetes and cancer. These receptors make an attractive anticancer target owing to their overexpression in variety of cancer especially in prostate and breast cancer. Inhibitors of IGF signaling were subjected to clinical cancer trials with the main objective to confirm the effectiveness of these receptors as a therapeutic target. However, the results that these trials produced proved to be disappointing as the role played by the cross talk between IGF and insulin receptor (IR) signaling pathways at the receptor level or at downstream signaling level became more lucid. Therapeutic strategy for IGF-1R and IR inhibition mainly encompasses three main approaches namely receptor blockade with monoclonal antibodies, tyrosine kinase inhibition (ATP antagonist and non-ATP antagonist), and ligand neutralization via monoclonal antibodies targeted to ligand or recombinant IGF-binding proteins. Other drug-discovery approaches are employed to target IGF-1R, and IR includes antisense oligonucleotides and recombinant IGF-binding proteins. However, therapies with monoclonal antibodies and tyrosine kinase inhibition targeting the IGF-1R are not evidenced to be satisfactory as expected. Factors that are duly held responsible for the unsuccessfulness of these therapies include (a) the existence of the IR isoform A overexpressed on a variety of cancers, enhancing the mitogenic signals to the nucleus leading to the endorsement of cell growth, (b) IGF-1R and IR that form hybrid receptors sensitive to the stimulation of all three IGF axis ligands, and (c) IGF-1R and IR that also have the potential to form hybrid receptors with other tyrosine kinase to potentiate the cellular transformation, tumorigenesis, and tumor vascularization. This mini review is a concerted effort to explore and fathom the well-recognized roles of the IRA signaling system in human cancer phenotype and the main strategies that have been so far evaluated to target the IR and IGF-1R.

IGF-1R inhibition enhances radiosensitivity and delays double-strand break repair by both non-homologous end-joining and homologous recombination

Inhibition of type 1 insulin-like growth factor receptor (IGF-1R) enhances tumor cell sensitivity to ionizing radiation. It is not clear how this effect is mediated, nor whether this approach can be applied effectively in the clinic. We previously showed that IGF-1R depletion delays repair of radiation-induced DNA double-strand breaks (DSBs), unlikely to be explained entirely by reduction in homologous recombination (HR) repair. The current study tested the hypothesis that IGF-1R inhibition induces a repair defect that involves non-homologous end joining (NHEJ). IGF-1R inhibitor AZ12253801 blocked cell survival and radiosensitized IGF-1R-overexpressing murine fibroblasts but not isogenic IGF-1R-null cells, supporting specificity for IGF-1R. IGF-1R inhibition enhanced radiosensitivity in DU145, PC3 and 22Rv1 prostate cancer cells, comparable to effects of Ataxia Telangiectasia Mutated inhibition. AZ12253801-treated DU145 cells showed delayed resolution of γH2AX foci, apparent within 1 h of irradiation and persisting for 24 h. In contrast, IGF-1R inhibition did not influence radiosensitivity or γH2AX focus resolution in LNCaP-LN3 cells, suggesting that radiosensitization tracks with the ability of IGF-1R to influence DSB repair. To differentiate effects on repair from growth and cell-survival responses, we tested AZ12253801 in DU145 cells at sub-SF50 concentrations that had no early (⩽48 h) effects on cell cycle distribution or apoptosis induction. Irradiated cultures contained abnormal mitoses, and after 5 days IGF-1R-inhibited cells showed enhanced radiation-induced polyploidy and nuclear fragmentation, consistent with the consequences of entry into mitosis with incompletely repaired DNA. AZ12253801 radiosensitized DNA-dependent protein kinase (DNA-PK)-proficient but not DNA-PK-deficient glioblastoma cells, and did not radiosensitize DNA-PK-inhibited DU145 cells, suggesting that in the context of DSB repair, IGF-1R functions in the same pathway as DNA-PK. Finally, IGF-1R inhibition attenuated repair by both NHEJ and HR in HEK293 reporter assays. These data indicate that IGF-1R influences DSB repair by both major DSB repair pathways, findings that may inform clinical application of this approach.

Role of IGF-1 pathway in lung fibroblast activation

Background

IGF-1 is elevated in pulmonary fibrosis and acute lung injury, where fibroblast activation is a prominent feature. We previously demonstrated that blockade of IGF pathway in murine model of lung fibrosis improved outcome and decreased fibrosis. We now expand that study to examine effects of IGF pathway on lung fibroblast behaviors that could contribute to fibrosis.

Methods

We first examined mice that express αSMA promoter upstream of GFP reporter treated with A12, a blocking antibody to IGF-1 receptor, after bleomycin induced lung injury. We then examined the effect of IGF-1 alone, or in combination with the pro-fibrotic cytokine TGFβ on expression of markers of myofibroblast activation in vitro, including αSMA, collagen α1, type 1, collagen α1, type III, and TGFβ expression.

Results

After bleomycin injury, we found decreased number of αSMA-GFP + cells in A12 treated mice, validated by αSMA immunofluorescent staining. We found that IGF-1, alone or in combination with TGF-β, did not affect αSMA RNA expression, promoter activity, or protein levels when fibroblasts were cultured on stiff substrate. IGF-1 stimulated Col1a1 and Col3a1 expression on stiff substrate. In contrast, IGF-1 treatment on soft substrate resulted in upregulation of αSMA gene and protein expression, as well as Col1a1 and Col3a1 transcripts. In conclusion, IGF-1 stimulates differentiation of fibroblasts into a myofibroblast phenotype in a soft matrix environment and has a modest effect on αSMA stress fiber organization in mouse lung fibroblasts.

Management of hormone-sensitive metastatic prostate cancer

Targeting gonadal androgen synthesis (often in conjunction with blockade of androgen receptor) is the cornerstone of treatment of hormone-sensitive metastatic prostate cancer (HSPC). Despite the failure of androgen deprivation therapy, most tumors maintain some dependence on androgen or androgen receptor signaling for proliferation. This article reviews the current standard of care for metastatic HSPC, mechanisms of treatment resistance, novel drugs targeting the androgen signaling pathway, biomarkers predicting response to treatment and survival, future directions, and ongoing clinical trials in HSPC.

The effect of IGF-I receptor blockade for human esophageal squamous cell carcinoma and adenocarcinoma

Insulin-like growth factor-I receptor (IGF-IR) signaling is required for carcinogenicity and tumor development, and this pathway has not been well studied in human esophageal carcinomas. Esophageal cancer is one of the human cancers with the worst prognosis and has two main histologies: squamous cell carcinomas (ESCC) and adenocarcinoma (EAC). Previously, we have reported that detection of the IGF axis may be useful for the prediction of recurrence and poor prognosis of ESCC. We have also shown the successful therapy for several gastrointestinal cancers using recombinant adenoviruses expressing dominant negative IGF-IR (ad-IGF-IR/dn). The aim of this study is to develop potential targeted therapeutics to IGF-IR and to assess the effect of IGF-IR blockade in both of these types of esophageal cancer. We determined immunohistochemical expression of IGF-IR in a tissue microarray. We then assessed the effect of IGF-IR blockade on signal transduction, proliferation, apoptosis, and motility. Ad-IGF-IR/dn, a tyrosine kinase inhibitor, BMS-536924, and adenovirus expressing shRNA for IGF-IR were used. IGF-IR expression was common in both tumor types but not in normal tissues. IGF-IR was detected in metastatic sites at similar levels compared to the primary site. IGF-IR inhibition suppressed proliferation and colony formation in both cancers. IGF-IR blockades up-regulated both stress- and chemotherapy-induced apoptosis and reduced migration. Although IGF-IR/dn blocked ligand-induced activation of Akt-1 mainly, BMS-536924 effectively blocked both activation of Akt and MAPK. The IGF axis might play a key role in tumor progression of esophageal carcinomas. The IGF-IR targeting strategies might thus be useful anticancer therapeutics for human esophageal malignancies.

Effects of calorie restriction and IGF-1 receptor blockade on the progression of 22Rv1 prostate cancer xenografts

Calorie restriction (CR) inhibits prostate cancer progression, partially through modulation of the IGF axis. IGF-1 receptor (IGF-1R) blockade reduces prostate cancer xenograft growth. We hypothesized that combining calorie restriction with IGF-1R blockade would have an additive effect on prostate cancer growth. Severe combined immunodeficient mice were subcutaneously injected with 22Rv1 cells and randomized to: (1) Ad libitum feeding/intraperitoneal saline (Ad-lib); (2) Ad-lib/20 mg/kg twice weekly, intraperitoneal ganitumab [anti-IGF-1R antibody (Ad-lib/Ab)]; (3) 40% calorie restriction/intraperitoneal saline (CR); (4) CR/ intraperitoneal ganitumab, (CR/Ab). CR and ganitumab treatment were initiated one week after tumor injection. Euthanasia occurred 19 days post treatment. Results showed that CR alone decreased final tumor weight, plasma insulin and IGF-1 levels, and increased apoptosis. Ganitumab therapy alone reduced tumor growth but had no effect on final tumor weight. The combination therapy (CR/Ab) further decreased final tumor weight and proliferation, increased apoptosis in comparison to the Ad-lib group, and lowered plasma insulin levels relative to the Ad-lib and Ad-lib/Ab groups. Tumor AKT activation directly correlated with plasma IGF-1 levels. In conclusion, whereas ganitumab therapy modestly affected 22Rv1 tumor growth, combining IGF-1R blockade with calorie restriction resulted in a significant decrease in final tumor weight and improved metabolic profile.

Response of the insulin-like growth factor (IGF) system to IGF-IR inhibition and androgen deprivation in a neoadjuvant prostate cancer trial: effects of obesity and androgen deprivation

CONTEXT

Prostate cancer patients at increased risk for relapse after prostatectomy were treated in a neoadjuvant study with androgen deprivation therapy (ADT) in combination with cixutumumab, an inhibitory fully human monoclonal antibody against IGF receptor 1 (IGF-IR).

OBJECTIVE

A clinical trial with prospective collection of serum and tissue was designed to test the potential clinical efficacy of neoadjuvant IGF-IR blockade combined with ADT in these patients. The effect of body mass index (BMI) on response of IGF-IR/insulin components to IGF-IR blockade was also examined.

DESIGN

Eligibility for the trial required the presence of high-risk prostate adenocarcinoma. Treatment consisted of bicalutamide, goserelin, and cixutumumab for 13 weeks before prostatectomy. Here we report on an analysis of serum samples from 29 enrolled patients. Changes in IGF and glucose homeostasis pathways were compared to control samples from patients in a concurrent clinical trial of neoadjuvant ADT alone.

RESULTS

Significant increases were seen in GH (P = .001), IGF-I (P < .0001), IGF-II (P = .003), IGF binding protein (IGFBP)-3 (P < .0001), C-peptide (P = .0038), and insulin (P = .05) compared to patients treated with ADT alone. IGFBP-1 levels were significantly lower in the cixutumumab plus ADT cohort (P = .001). No significant changes in blood glucose were evident. Patients with BMIs in the normal range had significantly higher GH (P < .05) and IGFBP-1 (P < 0.5) levels compared to overweight and obese patients.

CONCLUSIONS

Patients with IGF-IR blockade in combination with ADT demonstrated significant changes in IGF and glucose homeostasis pathway factors compared to patients receiving ADT alone. In the patients receiving combination therapy, patients with normal BMI had serum levels of glucose homeostasis components similar to individuals in the ADT-alone cohort, whereas patients with overweight and obese BMIs had serum levels that differed from the ADT cohort.

A phase I trial of the IGF-1R antibody Cixutumumab in combination with temsirolimus in patients with metastatic breast cancer

The mammalian target of rapamycin (mTOR) plays a critical role in promoting tumor cell growth and is frequently activated in breast cancer. In preclinical studies, the antitumor activity of mTOR inhibitors is attenuated by feedback up-regulation of AKT mediated in part by Insulin-like growth factor type 1 receptor (IGF-1R). We designed a phase I trial to determine the maximum-tolerated dose (MTD) and pharmacodynamic effects of the IGF-1R antibody Cixutumumab in combination with temsirolimus in patients with metastatic breast cancer refractory to standard therapies. A 3 + 3 Phase I design was chosen. Temsirolimus and Cixutumumab were administered intravenously on days 1, 8, 15, and 22 of a 4-week cycle. Of the 26 patients enrolled, four did not complete cycle 1 because of disease progression (n = 3) or comorbid condition (n = 1) and were replaced. The MTD was determined from the remaining 22 patients, aged 34-72 (median 48) years. Most patients (86 %) had estrogen receptor positive cancer. The median number of prior chemotherapy regimens for metastatic disease was 3. The MTD was determined to be Cixutumumab 4 mg/kg and temsirolimus 15 mg weekly. Dose-limiting toxicities (DLTs) included mucositis, neutropenia, and thrombocytopenia. Other adverse events included grade 1/2 fatigue, anemia, and hyperglycemia. No objective responses were observed, but four patients experienced stable disease that lasted for at least 4 months. Compared with baseline, there was a significant increase in the serum levels of IGF-1 (p < 0.001) and IGFBP-3 (p = 0.019) on day 2. Compared with day 2, there were significant increases in the serum levels of IGF-1 (p < 0.001), IGF-2 (p = 0.001), and IGFBP-3 (p = 0.019) on day 8. A phase II study in women with metastatic breast cancer is ongoing.

Insulin-like growth factor-1 genotypes and haplotypes influence the survival of prostate cancer patients with bone metastasis at initial diagnosis

Background

The insulin-like growth factor-1 (IGF-1) plays an important role in growth of prostate cancer (PCa) cells and facilitating the development and progression of PCa. This study aimed to evaluate the association of polymorphisms in three linkage disequilibrium (LD) blocks of the IGF-1 on the survival of metastatic PCa patients.

Methods

A total of 215 patients with bone metastases at initial presentation were included in this study. The cytosine-adenine (CA) repeat polymorphism and rs12423791 were selected as representative polymorphisms in the LD blocks 1 and 2, respectively. Haplotype in the LD block 3 was analyzed using two tag single nucleotide polymorphisms (SNPs), rs6220 and rs7136446. Cancer-specific survival rate was estimated from the Kaplan-Meier curve, and the survival data were compared using the log-rank test.

Results

Cancer-specific survival was significantly associated with the CA repeat polymorphism, rs12423791, and rs6220 (P = 0.013, 0.014, and 0.014, respectively). Although rs7136446 had no significant association with survival, the haplotype in the LD block 3 was significantly associated with cancer-specific survival (P = 0.0003). When the sum of the risk genetic factors in each LD block (19-repeat allele, C allele of rs12423791, or C-T haplotype) was considered, patients with all the risk factors had significantly shorter cancer specific-survival than those with 0–2 risk factors (P = 0.0003).

Conclusions

Polymorphisms in the IGF-1, especially a haplotype in the LD block 3, are assumed to be genetic markers predicting the outcome of metastatic PCa.

Targeting IGF-IR with ganitumab inhibits tumorigenesis and increases durability of response to androgen-deprivation therapy in VCaP prostate cancer xenografts

Prostate cancer is the most commonly diagnosed malignancy in men. While tumors initially respond to androgen-deprivation therapy, the standard care for advanced or metastatic disease, tumors eventually recur as castration-resistant prostate cancer (CRPC). Upregulation of the insulin-like growth factor receptor type I (IGF-IR) signaling axis drives growth and progression of prostate cancer by promoting proliferation, survival, and angiogenesis. Ganitumab (formerly AMG 479) is a fully human antibody that inhibits binding of IGF-I and IGF-II to IGF-IR. We evaluated the therapeutic value of ganitumab in several preclinical settings including androgen-dependent prostate cancer, CRPC, and in combination with androgen-deprivation therapy. Ganitumab inhibited IGF-I-induced phosphorylation of the downstream effector AKT and reduced proliferation of multiple androgen-dependent and castration-resistant human prostate cancer cell lines in vitro. Ganitumab inhibited androgen-dependent VCaP xenograft growth and increased tumor-doubling time from 2.3 ± 0.4 weeks to 6.4 ± 0.4 weeks. Ganitumab blocked growth of castration-resistant VCaP xenografts for over 11.5 weeks of treatment. In contrast, ganitumab did not have appreciable effects on the castration-resistant CWR-22Rv1 xenograft model. Ganitumab was most potent against VCaP xenografts when combined with complete androgen-deprivation therapy (castration). Tumor volume was reduced by 72% after 4 weeks of treatment and growth suppression was maintained over 16 weeks of treatment. These data suggest that judicious use of ganitumab particularly in conjunction with androgen-deprivation therapy may be beneficial in the treatment of prostate cancer.

Targeting IGF-1 signaling pathways in gynecologic malignancies

INTRODUCTION

The signaling pathways of the insulin-like growth factors (IGF) have been implicated in the etiology of a number of epithelial neoplasms including prostate, breast, colon and more recently, gynecologic cancers. The insulin-like growth factor-1 receptor (IGF-1R) is expressed in most transformed cells, where it displays potent anti-apoptotic, cell-survival and potentially, transforming activities. IGF-1R expression and activation are typical hallmarks associated with tumor initiation and progression. Multiple approaches have been used to abrogate IGF-1R signaling for targeted cancer therapy including antibodies and small molecule tyrosine kinase inhibitors. These novel IGF-1R targeting agents have produced significant experimental and clinical results in many cancers and generated considerable optimism in the field of cancer therapy.

AREAS COVERED

The authors will review important research advances regarding the role of the IGF axis in cancer, particularly preclinical and clinical studies in cervical, uterine and ovarian cancers. The significance of tumor expression and circulating levels of the IGF pathway as well as targeting therapies of the IGF axis in the gynecologic cancers will be discussed.

EXPERT OPINION

Accumulating data confirm that the IGF-1R pathway has an important role in gynecologic cancers and in vivo and in vitro studies have shown a significant impact of IGF-1R targeted therapies in these malignancies, mainly ovarian and endometrial cancers. Currently, ongoing preclinical and clinical trials are evaluating the efficacy of IGF-1R targeting. A better understanding of the complex mechanisms underlying the regulation of the IGF system will improve the ability to develop effective treatment modalities for these malignancies.

Combined Inhibition of IGF-1R/IR and Src family kinases enhances antitumor effects in prostate cancer by decreasing activated survival pathways

Background

Treatment of metastatic prostate cancer (PCa) with single agents has shown only modest efficacy. We hypothesized dual inhibition of different pathways in PCa results in improved tumor inhibition. The Src family kinases (SFK) and insulin-like growth factor-1 (IGF-1) signaling axes are aberrantly activated in both primary PCa and bone metastases and regulate distinct and overlapping functions in PCa progression. We examined the antitumor effects of combined inhibition of these pathways.

Materials and Methods

Src andIGF-1 receptor (IGF-1R) inhibition was achieved in vitro by short hairpin (sh)RNA and in vitro and in vivo by small molecule inhibitors (dasatinib and BMS-754807, against SFK and IGF-1R/Insulin Receptor(IR), respectively).

Results

In vitro, inhibition of IGF-1 signaling affected cell survival and proliferation. SFK blockade alone had modest effects on proliferation, but significantly enhanced the IGF-1R blockade. These findings correlated with a robust inhibition of IGF-1-induced Akt1 phophorylation by dasatinib, whereas Akt2 phosphorylation was SFK independent and only inhibited by BMS-754807. Thus, complete inhibition of both Akt genes, not seen by either drug alone, is likely a major mechanism for the decreased survival of PCa cells. Furthermore, dasatinib and BMS-754807 inhibited in vivo growth of the primary human xenograft MDA PCa 133, with corresponding inhibition of Akt in tumors. Also, both orthotopic and intratibial tumor growth of PC-3 cells were more potently inhibited by dual SFK and IGF-1R/IR blockade compared to either pathway alone, with a corresponding decrease in bone turnover markers.

Conclusions

Dual IGF-1R/IR and SFK inhibition may be a rational therapeutic approach in PCa by blocking both independent and complementary processes critical to tumor growth.

Diverse functions of IGF/insulin signaling in malignant and noncancerous prostate cells: proliferation in cancer cells and differentiation in noncancerous cells

The insulin-like growth factor (IGF) pathway represents one of the most studied molecular regulatory networks in oncology. Clinical trials investigating the therapeutic value of anti-IGF1 receptor (IGF1R) therapies in cancer, including prostate cancer, are ongoing. However, the multiple functions of the IGF network in the prostate are not entirely known. To elucidate the effects of IGF and insulin (INS) on prostate cells, we stimulated prostate cancer (PC3, DU145, LNCaP, DUCaP) and noncancerous prostate cells (EP156T, RWPE-1) and observed differing responses: whereas cancer cells responded to IGF and INS exposure by way of enhanced cell proliferation and glucose consumption, basal to luminal differentiation was induced in noncancerous cells. The same diverse responses were observed when the growth factor receptors IGF1R or INSR were overexpressed. Down-regulation of IGF1R or INSR isoform A (INSRA) also inhibited only proliferation of cancer cells. The proliferative response induced by the INSR in cancer cells was mediated solely by the INSRA. Moreover we observed that the receptors of the IGF network mutually influence their expression and exert redundant functions, thus underscoring the functional molecular network formed by IGF, INS, IGF1R, and INSR. Collectively we found that both IGF1R and INSRA have oncogenic effects in prostate cancer, but the IGF network also has important physiological functions in the noncancerous prostate. These data provide new insights into the biology of the IGF network in the prostate, thereby facilitating the design and interpretation of clinical studies investigating IGF1R targeting agents.

Advanced clinical states in prostate cancer

The classification of clinical disease states within advanced prostate cancer is set apart from other solid tumors largely through measurement of prostate-specific antigen in the blood. This testing has allowed the distinction between the castration-sensitive and the castration-resistant states, to complement radiographic distinction within advanced prostate cancer. This has paved the way for advances in prognostication and treatment of patients within a heterogeneous disease group. Currently used clinical classifications have limitations and continue to evolve. The authors define the current disease states and discuss implications for prognosis and treatment decisions, as well as the limitations of existing classifications and emerging discoveries.

VEGF/neuropilin-2 regulation of Bmi-1 and consequent repression of IGF-IR define a novel mechanism of aggressive prostate cancer

We show that the VEGF receptor neuropilin-2 (NRP2) is associated with high-grade, PTEN-null prostate cancer and that its expression in tumor cells is induced by PTEN loss as a consequence of c-Jun activation. VEGF/NRP2 signaling represses insulin-like growth factor-1 receptor (IGF-IR) expression and signaling, and the mechanism involves Bmi-1-mediated transcriptional repression of the IGF-IR. This mechanism has significant functional and therapeutic implications that were evaluated. IGF-IR expression positively correlates with PTEN and inversely correlates with NRP2 in prostate tumors. NRP2 is a robust biomarker for predicting response to IGF-IR therapy because prostate carcinomas that express NRP2 exhibit low levels of IGF-IR. Conversely, targeting NRP2 is only modestly effective because NRP2 inhibition induces compensatory IGF-IR signaling. Inhibition of both NRP2 and IGF-IR, however, completely blocks tumor growth in vivo.

Effect of a low-fat diet combined with IGF-1 receptor blockade on 22Rv1 prostate cancer xenografts

In preclinical models, both dietary fat reduction and insulin-like growth factor I receptor (IGF-1R) blockade individually inhibit prostate cancer xenograft growth. We hypothesized that a low-fat diet combined with IGF-1R blockade would cause additive inhibition of prostate cancer growth and offset possible untoward metabolic effects of IGF-1R blockade antibody therapy. Fifty severe combined immunodeficient mice were injected with 22Rv1 cells subcutaneously. Ten days postinjection, the animals were randomized to four groups: (i) high-fat diet + saline (HF); (ii) high-fat diet + IGF-1R blocking antibody, ganitumab (HF/Ab); (iii) low-fat diet + saline (LF); and (iv) low-fat diet + ganitumab (LF/Ab). After 19 days of treatment, the animals were euthanized, serum was collected, and tumors were weighed. Tumor Ki67, Akt and extracellular signal-regulated kinase (ERK) activation, serum insulin, IGF-I and TNF-α were measured. In vitro, ganitumab treatment inhibited growth and induced apoptosis in several prostate cancer cell lines. In vivo, tumor weights and volumes were unaffected by the different treatments. The LF/Ab therapy significantly reduced proliferation (Ki67) and ERK activation in tumors. The HF/Ab group had significantly higher serum insulin levels than the HF group. However, LF/Ab combination significantly reduced serum insulin back to normal levels as well as normalizing serum TNF-α level. Whereas the combination of low-fat diet and IGF-1R blockade did not have additive inhibitory effects on tumor weight, it led to reduced tumor cell proliferation and a reduction in serum insulin and TNF-α levels.