Dual IGF-1R/InsR inhibitor BMS-754807 synergizes with hormonal agents in treatment of estrogen-dependent breast cancer

Quantitative phosphoproteomic analysis identifies activation of the RET and IGF-1R/IR signaling pathways in neuroblastoma

Neuroblastoma is an embryonal tumor of childhood with a heterogenous clinical presentation that reflects differences in activation of complex biological signaling pathways. Protein phosphorylation is a key component of cellular signal transduction and plays a critical role in processes that control cancer cell growth and survival. We used shotgun LC/MS to compare phosphorylation between a human MYCN amplified neuroblastoma cell line (NB10), modeling a resistant tumor, and a human neural precursor cell line (NPC), modeling a normal baseline neural crest cell. 2181 unique phosphorylation sites representing 1171 proteins and 2598 phosphopeptides were found. Protein kinases accounted for 6% of the proteome, with a predominance of tyrosine kinases, supporting their prominent role in oncogenic signaling pathways. Highly abundant receptor tyrosine kinase (RTK) phosphopeptides in the NB10 cell line relative to the NPC cell line included RET, insulin-like growth factor 1 receptor/insulin receptor (IGF-1R/IR), and fibroblast growth factor receptor 1 (FGFR1). Multiple phosphorylated peptides from downstream mediators of the PI3K/AKT/mTOR and RAS pathways were also highly abundant in NB10 relative to NPC. Our analysis highlights the importance of RET, IGF-1R/IR and FGFR1 as RTKs in neuroblastoma and suggests a methodology that can be used to identify potential novel biological therapeutic targets. Furthermore, application of this previously unexploited technology in the clinic opens the possibility of providing a new wide-scale molecular signature to assess disease progression and prognosis.

Synthesis and in vitro evaluation of [18F]BMS-754807: a potential PET ligand for IGF-1R

Radiosynthesis and in vitro evaluation of [(18)F](S)-1-(4-((5-cyclopropyl-1H-pyrazol-3-yl)amino)pyrrolo[2,1-f][1,2,4]triazin-2-yl)-N-(6-fluoropyridin-3-yl)-2-methylpyrrolidine-2-carboxamide ([(18)F]BMS-754807 or [(18)F]1) a specific IGF-1R inhibitor was performed. [(18)F]1 demonstrated specific binding in vitro to human cancer tissues. Synthesis of reference standard 1 and corresponding bromo derivative (1a), the precursor for radiolabeling were achieved from 2,4-dichloropyrrolo[2,1-f][1,2,4]triazine (4) in three steps with 50% overall yield. The radioproduct was obtained in 8% yield by reacting 1a with [(18)F]TBAF in DMSO at 170°C at high radiochemical purity and specific activity (1-2Ci/μmol, N=10). The proof of concept of IGF-IR imaging with [(18)F]1 was demonstrated by in vitro autoradiography studies using pathologically identified surgically removed grade IV glioblastoma, breast cancer and pancreatic tumor tissues. These studies indicate that [(18)F]1 can be a potential PET tracer for monitoring IGF-1R.

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 and musculoskeletal pain among breast cancer patients on aromatase inhibitor therapy and women without a history of cancer

PURPOSE

Musculoskeletal pain is a common side effect of aromatase inhibitors (AIs), the adjuvant hormonal treatment of choice for postmenopausal estrogen-receptor-positive breast cancer. Although the pain is usually attributed to the estrogen depletion associated with AIs, not all women on AIs experience these symptoms. Thus, the goal of this study was to examine whether changes in the insulin-like growth factor (IGF) axis were associated with pain among women initiating AI therapy or a comparison group of women without a history of cancer.

METHODS

Data were analyzed from a cohort study of 52 breast cancer patients for whom AI therapy was planned and 88 women without a history of cancer. Questionnaire data on pain symptoms were collected, and blood was drawn at baseline (prior to AI therapy for patients) and 6 months after baseline. The blood samples were assayed for IGF-1 and IGF-binding protein-3 (IGFBP-3).

RESULTS

While results showed no statistically significant changes in any of the measures across time for either the breast cancer or the comparison group, increases in both IGF-1 concentrations and the IGF-1/IGFBP-3 ratio over the first 6 months of AI treatment were significantly associated with the onset or increase in musculoskeletal pain among the breast cancer patients. Associations between IGF-1, IGFBP-3, and the IGF-1/IGFBP-3 ratio and pain were not observed in the comparison group.

CONCLUSIONS

Although preliminary, findings from this study implicate the IGF axis in the development of AI-associated musculoskeletal pain and represent a first step in developing effective interventions to alleviate this side effect.

New and emerging treatments for estrogen receptor-positive breast cancer: focus on everolimus

Management of patients with metastatic hormone receptor-positive breast cancer poses a challenge due to the inevitable development of endocrine resistance. Hormone resistance is associated with a complex interaction of the estrogen receptor with growth factors, transmembrane receptors, and intracellular growth cascades. The PI3K/Akt/mTOR pathway plays a major role in hormone resistance and proliferation of breast cancer. Preclinical and clinical data indicate that inhibitors of human epidermal growth factor receptor-2, epidermal growth factor receptor, insulin-like growth factor-1 receptor, and the mammalian target of rapamycin pathway may act synergistically with hormone therapy to circumvent endocrine resistance. Everolimus is currently approved for combination with exemestane in postmenopausal women with advanced hormone receptor-positive breast cancer. However, we still need to unfold the full potential of targeted agents in the hormone-refractory setting and to identify the subsets of patients who will benefit from combination hormonal therapy using targeted agents.

Targeting insulin and insulin-like growth factor signaling in breast cancer

The insulin and insulin like growth factor (IGF) signaling systems are implicated in breast cancer biology. Thus, disrupting IGF/insulin signaling has been shown to have promise in a number of preclinical models. However, human clinical trials have been less promising. Despite evidence of some activity in early phase trials, randomized phase III studies have thus far been unable to show a benefit of blocking IGF signaling in combination with conventional strategies. In breast cancer, combination anti IGF/insulin signaling agents with hormone therapy has not yet proven to have benefit. This inability to translate the preclinical findings into useful clinical strategies calls attention to the need for a deeper understanding of this complex pathway. Development of predictive biomarkers and optimal inhibitory strategies of the IGF/insulin system should yield better clinical strategies. Furthermore, unraveling the interaction between the IGF/insulin pathway and other critical signaling pathways in breast cancer biology, namely estrogen receptor-α (ERα) and epidermal growth factor receptor (EGFR) pathways, provides additional new concepts in designing combination therapies. In this review, we will briefly summarize the current strategies targeting the IGF/insulin system, discuss the possible reasons of success or failure of the existing therapies, and provide potential future directions for research and clinical trials.

Trichosanthin inhibits breast cancer cell proliferation in both cell lines and nude mice by promotion of apoptosis

Breast cancer ranks as a common and severe neoplasia in women with increasing incidence as well as high risk of metastasis and relapse. Translational and laboratory-based clinical investigations of new/novel drugs are in progress. Medicinal plants are rich sources of biologically active natural products for drug development. The 27-kDa trichosanthin (TCS) is a ribosome inactivating protein purified from tubers of the Chinese herbal plant Trichosanthes kirilowii Maximowicz (common name Tian Hua Fen). In this study, we extended the potential medicinal applications of TCS from HIV, ferticide, hydatidiform moles, invasive moles, to breast cancer. We found that TCS manifested anti-proliferative and apoptosis-inducing activities in both estrogen-dependent human MCF-7 cells and estrogen-independent MDA-MB-231 cells. Flow cytometric analysis disclosed that TCS induced cell cycle arrest. Further studies revealed that TCS-induced tumor cell apoptosis was attributed to activation of both caspase-8 and caspase-9 regulated pathways. The subsequent events including caspase-3 activation, and increased PARP cleavage. With regard to cell morphology, stereotypical apoptotic features were observed. Moreover, in comparison with control, TCS- treated nude mice bearing MDA-MB-231 xenograft tumors exhibited significantly reduced tumor volume and tumor weight, due to the potent effect of TCS on tumor cell apoptosis as determined by the increase of caspase-3 activation, PARP cleavage, and DNA fragmentation using immunohistochemistry. Considering the clinical efficacy and relative safety of TCS on other human diseases, this work opens up new therapeutic avenues for patients with estrogen-dependent and/or estrogen-independent breast cancers.

Quantifying insulin receptor isoform expression in FFPE breast tumors

BACKGROUND

The development of predictive biomarkers for IGF targeted anti-cancer therapeutics remains a critical unmet need. The insulin receptor A isoform (InsR-A) has been identified as a possible biomarker candidate but quantification of InsR-A in widely available formalin fixed paraffin embedded (FFPE) tissues is complicated by its similarities with the metabolic signaling insulin receptor isoform B (InsR-B). In the present study, qPCR based assays specific for InsR-A, InsR-B and IGF-1R were developed for use in FFPE tissues and tested for feasible use in clinical archived FFPE estrogen receptor (ER)+and ER- breast cancer tumors.

DESIGN

FFPE compatible primer sets were designed with amplicon sizes of less than 60 base pairs and validated for target specificity, assay repeatability and amplification efficiency. FFPE tumors from ER+ (n=83) and ER-(n=64) primary untreated breast cancers, and ER+ hormone refractory (HR ER+) (n=61) breast cancers were identified for feasibility testing. The feasible use of InsR-A and InsR-B qPCRs were tested using all tumor groups and the feasibility of IGF-1R qPCR was determined using HR ER+ tumors.

RESULTS

All qPCR assays were highly reproducible with amplification efficiencies between 96-104% over a 6 log range with limits of detection of 4 or 5 copies per reaction. Greater than 90% of samples were successfully amplified using InsR-A, InsR-B or IGF-1R qPCR primer sets and greater than 88% of samples tested amplified both InsR isoforms or both isoforms and IGF-1R. InsR-A was the predominant isoform in 82% ER+, 68% ER- and 100% HR ER+ breast cancer. Exploratory analyses demonstrated significantly more InsR-A expression in ER+ and HR ER+ groups compared to InsR-B (ER+ p<0.05, HR ER+ p<0.0005) and both groups had greater InsR-A expression when compared to ER- tumors (ER+ p<0.0005, HR ER+ p<0.05). IGF-1R expression of HR ER+ tumors was lower than InsR-A (p<0.0005) but higher than InsR-B (p<0.0005). The InsR-B expression of HR ER+ tumors was significantly reduced compared other tumor subgroups (ER+ and ER-, p<0.0005) and lead to a significant elevation of HR ER+ InsR-A: InsR-B ratios (ER+ and ER-, p<0.0005).

CONCLUSIONS

The validated, highly sensitive InsR-A and InsR-B qPCR based assays presented here are the first to demonstrate the feasible amplification of InsR isoforms in FFPE tissues. Quantification data generated from this feasibility study indicating InsR-A is more predominant than InsR-B in breast cancer support the use of these assays for further investigation of InsR-A and InsR-B as predictive biomarkers for IGF targeted therapeutics.

The insulin receptor/insulin-like growth factor receptor family as a therapeutic target in oncology

Over the past decade, encouraging preclinical and early clinical data concerning the relevance of the insulin receptor/insulin-like growth factor (IGF) receptor family to neoplasia led to ambitious clinical trial programs of more than a dozen drug candidates that target these receptors. These candidates include antireceptor antibodies, antiligand antibodies, receptor-specific tyrosine kinase inhibitors, and agents such as picropodophyllin and metformin that have novel mechanisms of action. Several recently reported phase III clinical trials of anti-IGF-I receptor antibodies have been disappointing and are sufficient to disprove the hypothesis that the antibodies tested have large favorable impacts on unselected patients with cancer. However, many of these trials were designed prior to recent insights concerning pathophysiology and predictive biomarkers. Future studies are required, but it will be important to optimize their design rather than simply repeat the approaches taken to date.

Targeting insulin-like growth factor in breast cancer therapeutics

The insulin-like growth factor (IGF) pathway holds crucial role in cell growth, differentiation and proliferation. Aberrant regulation of the IGF system has been attributed to the pathogenesis of breast cancer and has been shown to contribute to various stages of breast carcinogenesis. Therefore, targeting the IGF-related axis represents a promising strategy, mainly aiming to bypass the resistance of currently employed treatment options in breast cancer patients. Nevertheless, major limitations have aroused despite the early stage of clinical development of various IGF-system modulators. The present review highlights the current status and considers the future perspectives of IGF-system targeting in breast cancer therapeutics.