Antixenograft tumor activity of a humanized anti-insulin-like growth factor-I receptor monoclonal antibody is associated with decreased AKT activation and glucose uptake

IGF-1R anti-idiotypic antibody antagonist exhibited anti-ovarian cancer bioactivity and reduced cisplatin resistance

Ovarian cancer is the most deadly gynecological malignant tumor in the world today. Previous studies have shown that insulin-like growth factor-1 receptor (IGF-1R) is closely related to the occurrence and development of ovarian cancer, and ovarian cancer cells endogenously express high IGF-1R. Therefore, IGF-1R could be used as a target for ovarian cancer treatment. In the past, the strategy for preparing IGF-1R antagonists was to use IGF-1R antibody and small-molecule inhibitor. In the current research, we use a new method to prepare IGF-1R antagonists. We prepared a series of IGF-1 internal imaging anti-idiotypic antibodies by anti-idiotypic antibody strategy. After a series of screening and identification, one of the anti-idiotypic antibodies (B003-2A) was selected for further evaluation, and the results showed that B003-2A could not only inhibit the binding of IGF-1 to IGF-1R but also inhibit the signaling mediated by IGF-1R. Further work showed that B003-2A inhibited the proliferation of ovarian cancer cells in vivo and in vitro. In addition, the current study also indicates that B003-2A could enhance the sensitivity of cisplatin in cisplatin-resistant ovarian cancer cell lines. In summary, our research shows that B003-2A can be used to treat ovarian cancer. The current study also laid the foundation for the development of IGF-1R antagonist.

Disruption of FOXO3a-miRNA feedback inhibition of IGF2/IGF-1R/IRS1 signaling confers Herceptin resistance in HER2-positive breast cancer

Resistance to Herceptin represents a significant challenge for successful treatment of HER2-positive breast cancer. Here, we show that in Herceptin-sensitive cells, FOXO3a regulates specific miRNAs to control IGF2 and IRS1 expression, retaining basic IGF2/IGF-1R/IRS1 signaling. The basic activity maintains expression of PPP3CB, a subunit of the serine/threonine-protein phosphatase 2B, to restrict FOXO3a phosphorylation (p-FOXO3a), inducing IGF2- and IRS1-targeting miRNAs. However, in Herceptin-resistant cells, p-FOXO3a levels are elevated due to transcriptional suppression of PPP3CB, disrupting the negative feedback inhibition loop formed by FOXO3a and the miRNAs, thereby upregulating IGF2 and IRS1. Moreover, we detect significantly increased IGF2 in blood and IRS1 in the tumors of breast cancer patients with poor response to Herceptin-containing regimens. Collectively, we demonstrate that the IGF2/IGF-1R/IRS1 signaling is aberrantly activated in Herceptin-resistant breast cancer via disruption of the FOXO3a-miRNA negative feedback inhibition. Such insights provide avenues to identify predictive biomarkers and effective strategies overcoming Herceptin resistance.

Insulin/IGF signaling and discoidin domain receptors: An emerging functional connection

The insulin/insulin-like growth factor system (IIGFs) plays a fundamental role in the regulation of prenatal and postnatal growth, metabolism and homeostasis. As a consequence, dysregulation of this axis is associated with growth disturbance, type 2 diabetes, chronic inflammation and tumor progression. A functional crosstalk between IIGFs and discoidin domain receptors (DDRs) has been recently discovered. DDRs are non-integrin collagen receptors that canonically undergo slow and long-lasting autophosphorylation after binding to fibrillar collagen. While both DDR1 and DDR2 functionally interact with IIGFs, the crosstalk with DDR1 is so far better characterized. Notably, the IIGFs-DDR1 crosstalk presents a feed-forward mechanism, which does not require collagen binding, thus identifying novel non-canonical action of DDR1. Further studies are needed to fully explore the role of this IIGFs-DDRs functional loop as potential target in the treatment of inflammatory and neoplastic disorders.

Mechanisms of Acquired Resistance to Trastuzumab Emtansine in Breast Cancer Cells

The receptor tyrosine kinase HER2 is overexpressed in approximately 20% of breast cancer, and its amplification is associated with reduced survival. Trastuzumab emtansine (Kadcyla, T-DM1), an antibody-drug conjugate that is comprised of trastuzumab covalently linked to the antimitotic agent DM1 through a stable linker, was designed to selectively deliver DM1 to HER2-overexpressing tumor cells. T-DM1 is approved for the treatment of patients with HER2-positive metastatic breast cancer following progression on trastuzumab and a taxane. Despite the improvement in clinical outcome, many patients who initially respond to T-DM1 treatment eventually develop progressive disease. The mechanisms that contribute to T-DM1 resistance are not fully understood. To this end, we developed T-DM1-resistant in vitro models to examine the mechanisms of acquired T-DM1 resistance. We demonstrate that decreased HER2 and upregulation of MDR1 contribute to T-DM1 resistance in KPL-4 T-DM1-resistant cells. In contrast, both loss of SLC46A3 and PTEN deficiency play a role in conferring resistance in BT-474M1 T-DM1-resistant cells. Our data suggest that these two cell lines acquire resistance through distinct mechanisms. Furthermore, we show that the KPL-4 T-DM1 resistance can be overcome by treatment with an inhibitor of MDR1, whereas a PI3K inhibitor can rescue PTEN loss-induced resistance in T-DM1-resistant BT-474M1 cells. Our results provide a rationale for developing therapeutic strategies to enhance T-DM1 clinical efficacy by combining T-DM1 and other inhibitors that target signaling transduction or resistance pathways. Mol Cancer Ther; 17(7); 1441-53. ©2018 AACR.

GLUT1 expression in pediatric adrenocortical tumors: a promising candidate to predict clinical behavior

Background

Discrimination between benign and malignant tumors is a challenging process in pediatric adrenocortical tumors. New insights in the metabolic profile of pediatric adrenocortical tumors may contribute to this distinction, predict prognosis, as well as identify new molecular targets for therapy. The aim of this work is to characterize the expression of the metabolism-related proteins MCT1, MCT2, MCT4, CD147, CD44, GLUT1 and CAIX in a series of pediatric adrenocortical tumors.

Methods

A total of 50 pediatric patients presenting adrenocortical tumors, including 41 clinically benign and 9 clinically malignant tumors, were included. Protein expression was evaluated using immunohistochemistry in samples arranged in tissue microarrays.

Results

The immunohistochemical analysis showed a significant increase in plasma membrane expression of GLUT1 in malignant lesions, when compared to benign lesions (p=0.004), being the expression of this protein associated with shorter overall and disease-free survival (p=0.004 and p=0.001, respectively). Although significant differences were not observed for proteins other than GLUT1, MCT1, MCT4 and CD147 were highly expressed in pediatric adrenocortical neoplasias (around 90%).

Conclusion

GLUT1 expression was differentially expressed in pediatric adrenocortical tumors, with higher expression in clinically malignant tumors, and associated with shorter survival, suggesting a metabolic remodeling towards a hyperglycolytic phenotype in this malignancy.

Clinical studies in humans targeting the various components of the IGF system show lack of efficacy in the treatment of cancer

The insulin-like growth factors (IGFs) system regulates cell growth, differentiation and energy metabolism and plays crucial role in the regulation of key aspects of tumor biology, such as cancer cell growth, survival, transformation and invasion. The current focus for cancer therapeutic approaches have shifted from the conventional treatments towards the targeted therapies and the IGF system has gained a great interest as anti-cancer therapy. The proliferative, anti-apoptotic and transformation effects of IGFs are mainly triggered by the ligation of the type I IGF receptor (IGF-IR). Thus, aiming at developing novel and effective cancer therapies, different strategies have been employed to target IGF system in human malignancies, including but not limited to ligand or receptor neutralizing antibodies and IGF-IR signaling inhibitors. In this review, we have focused on the clinical studies that have been conducted targeting the various components of the IGF system for the treatment of different types of cancer, providing a description and the challenges of each targeting strategy and the degree of success.

Antiproliferative and apoptotic effects of a specific anti-insulin-like growth factor I receptor single chain antibody on breast cancer cells

Insulin-like growth factor I receptor (IGF-IR) is expressed on breast cancer cells and involves in metastasis, survival, and proliferation. Currently, application of IGF-IR-targeting monoclonal antibodies (mAbs), alone or in combination with other drugs, is a promising strategy for breast cancer therapy. Single-chain fragment variable (scFv) antibodies have been introduced as appropriate tools for tumor-targeting purposes because of their advantages over whole antibodies. In the present study, we employed a naïve phage library and isolated scFvs against a specific epitope from extracellular domain of IGF-IR by panning process. The selected scFvs were further characterized using polyclonal and monoclonal phage ELISA, soluble monoclonal ELISA, and colony PCR and sequencing. Antiproliferative and apoptotic effects of selected scFv antibodies on breast cancer cell lines were also evaluated by MTT and Annexin V/PI assays. The results of ELISA indicated specific reactions of the isolated scFvs against the IGF-IR peptide, and analyses of PCR product and sequencing confirmed the presence of full length V_H and Vκ inserts. Treatment of MCF7 and SKBR3 cells with anti-IGF-IR scFv led to a significant growth inhibition. The results also showed that scFv treatment significantly augmented trastuzumab growth inhibitory effects on SKBR3 cells. The percentage of the apoptotic MCF7 and SKBR3 cells after 24-h treatment with scFv was 39 and 30.70 %, respectively. Twenty-four-hour treatment with scFv in combination with trastuzumab resulted in 44.75 % apoptosis of SKBR3 cells. Taken together, our results demonstrate that the targeting of IGF-IR by scFv can be an effective strategy in the treatment of breast cancer and provide further evidence for effectiveness of dual targeting of HER2 and IGF-IR in breast cancer therapy.

Focal adhesion kinase-promoted tumor glucose metabolism is associated with a shift of mitochondrial respiration to glycolysis

Cancer cells often gains a growth advantage by taking up glucose at a high rate and undergoing aerobic glycolysis through intrinsic cellular factors that reprogram glucose metabolism. Focal adhesion kinase (FAK), a key transmitter of growth factor and anchorage stimulation, is aberrantly overexpressed or activated in most solid tumors, including pancreatic ductal adenocarcinomas (PDACs). We determined whether FAK can act as an intrinsic driver to promote aerobic glycolysis and tumorigenesis. FAK inhibition decreases and overexpression increases intracellular glucose levels during unfavorable conditions, including growth factor deficiency and cell detachment. Amplex glucose assay, fluorescence and carbon-13 tracing studies demonstrate that FAK promotes glucose consumption and glucose-to-lactate conversion. Extracellular flux analysis indicates that FAK enhances glycolysis and decreases mitochondrial respiration. FAK increases key glycolytic proteins, including enolase, pyruvate kinase M2 (PKM2), lactate dehydrogenase and monocarboxylate transporter. Furthermore, active/tyrosine-phosphorylated FAK directly binds to PKM2 and promotes PKM2-mediated glycolysis. On the other hand, FAK-decreased levels of mitochondrial complex I can result in reduced oxidative phosphorylation (OXPHOS). Attenuation of FAK-enhanced glycolysis re-sensitizes cancer cells to growth factor withdrawal, decreases cell viability and reduces growth of tumor xenografts. These observations, for the first time, establish a vital role of FAK in cancer glucose metabolism through alterations in the OXPHOS-to-glycolysis balance. Broadly targeting the common phenotype of aerobic glycolysis and more specifically FAK-reprogrammed glucose metabolism will disrupt the bioenergetic and biosynthetic supply for uncontrolled growth of tumors, particularly glycolytic PDAC.

Role of IGF1R in Breast Cancer Subtypes, Stemness, and Lineage Differentiation

Insulin-like growth factor (IGF) signaling is fundamental for growth and survival. A large body of evidence (laboratory, epidemiological, and clinical) implicates the exploitation of this pathway in cancer. Up to 50% of breast tumors express the activated form of the type 1 insulin-like growth factor receptor (IGF1R). Breast cancers are categorized into subtypes based upon hormone and ERRB2 receptor expression and/or gene expression profiling. Even though IGF1R influences tumorigenic phenotypes and drug resistance across all breast cancer subtypes, it has specific expression and function in each. In some subtypes, IGF1R levels correlate with a favorable prognosis, while in others it is associated with recurrence and poor prognosis, suggesting different actions based upon cellular and molecular contexts. In this review, we examine IGF1R expression and function as it relates to breast cancer subtype and therapy-acquired resistance. Additionally, we discuss the role of IGF1R in stem cell maintenance and lineage differentiation and how these cell fate influences may alter the differentiation potential and cellular composition of breast tumors.

An antimesothelin-monomethyl auristatin e conjugate with potent antitumor activity in ovarian, pancreatic, and mesothelioma models

Mesothelin (MSLN) is an attractive target for antibody-drug conjugate therapy because it is highly expressed in various epithelial cancers, with normal expression limited to nondividing mesothelia. We generated novel antimesothelin antibodies and conjugated an internalizing one (7D9) to the microtubule-disrupting drugs monomethyl auristatin E (MMAE) and MMAF, finding the most effective to be MMAE with a lysosomal protease-cleavable valine-citrulline linker. The humanized (h7D9.v3) version, αMSLN-MMAE, specifically targeted mesothelin-expressing cells and inhibited their proliferation with an IC50 of 0.3 nmol/L. Because the antitumor activity of an antimesothelin immunotoxin (SS1P) in transfected mesothelin models did not translate to the clinic, we carefully selected in vivo efficacy models endogenously expressing clinically relevant levels of mesothelin, after scoring mesothelin levels in ovarian, pancreatic, and mesothelioma tumors by immunohistochemistry. We found that endogenous mesothelin in cancer cells is upregulated in vivo and identified two suitable xenograft models for each of these three indications. A single dose of αMSLN-MMAE profoundly inhibited or regressed tumor growth in a dose-dependent manner in all six models, including two patient-derived tumor xenografts. The robust and durable efficacy of αMSLN-MMAE in preclinical models of ovarian, mesothelioma, and pancreatic cancers justifies the ongoing phase I clinical trial.

Phase 2 trial of cixutumumab in children, adolescents, and young adults with refractory solid tumors: a report from the Children's Oncology Group

PURPOSE

This phase 2 study was designed to assess the efficacy of single agent cixutumumab (IMC-A12) and gain further information about associated toxicities and pharmacodynamics in children, adolescents, and young adults with recurrent or refractory solid tumors.

PATIENTS AND METHODS

Patients with relapsed or refractory solid tumors were treated with 9 mg/kg of cixutumumab as a 1-hour IV infusion once weekly. Strata included: osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, neuroblastoma (evaluable disease), neuroblastoma (measurable disease), Wilms tumor, adrenocortical carcinoma, synovial sarcoma, hepatoblastoma, and retinoblastoma. Correlative studies in consenting patients included an assessment of c-peptide, IGFBP-3, IGF-1, IGF-2, hGH, and insulin in consenting patients.

RESULTS

One hundred sixteen patients with 114 eligible having a median age of 12 years (range, 2-30) were enrolled. Five patients achieved a partial response: 4/20 with neuroblastoma (evaluable only) and 1/20 with rhabdomyosarcoma. Fourteen patients had stable disease for a median of 10 cycles. Hematologic and non-hematologic toxicities were generally mild and infrequent. Serum IGF-1 and IGFBP-3 increased in response to therapy with cixutumumab.

CONCLUSION

Cixutumumab is well tolerated in children with refractory solid tumors. Limited objective single-agent activity of cixutumumab was observed; however, prolonged stable disease was observed in 15% of patients. Ongoing studies are evaluating the toxicity and benefit of cixutumumab in combination with other agents that inhibit the IGF pathway.

The role of FAK in tumor metabolism and therapy

Focal adhesion kinase (FAK) plays a vital role in tumor cell proliferation, survival and migration. Altered metabolic pathways fuel rapid tumor growth by accelerating glucose, lipid and glutamine processing. Besides the mitogenic effects of FAK, evidence is accumulating supporting the association between hyper-activated FAK and aberrant metabolism in tumorigenesis. FAK can promote glucose consumption, lipogenesis, and glutamine dependency to promote cancer cell proliferation, motility, and survival. Clinical studies demonstrate that FAK-related alterations of tumor metabolism are associated with increased risk of developing solid tumors. Since FAK contributes to the malignant phenotype, small molecule inhibition of FAK-stimulated bioenergetic and biosynthetic processes can provide a novel approach for therapeutic intervention in tumor growth and invasion.

In vivo analysis of insulin-like growth factor type 1 receptor humanized monoclonal antibody MK-0646 and small molecule kinase inhibitor OSI-906 in colorectal cancer

The development and characterization of effective anticancer drugs against colorectal cancer (CRC) is of urgent need since it is the second most common cause of cancer death. The study was designed to evaluate the effects of two IGF-1R antagonists, MK-0646, a recombinant fully humanized monoclonal antibody and OSI-906, a small molecule tyrosine kinase inhibitor on CRC cells. Xenograft study was performed on IGF-1R-dependent CRC cell lines for analyzing the antitumor activity of MK-0646 and OSI-906. Tumor proliferation and apoptosis were assessed using Ki67 and TUNEL assays, respectively. We also performed in vitro characterization of MK-0646 and OSI-906 treatment on CRC cells to identify mechanisms associated with drug-induced cell death. Exposure of the GEO and CBS tumor xenografts to MK-0646 or OSI-906 led to a decrease in tumor growth. TUNEL analysis showed an increase of approximately 45-55% in apoptotic cells in both MK-0646 and OSI-906 treated tumor samples. We report the novel finding that treatment with IGF-1R antagonists led to downregulation of X-linked inhibitor of apoptosis (XIAP) protein involved in cell survival and inhibition of cell death. In conclusion, IGF-1R antagonists (MK-0646 and OSI-906) demonstrated single agent inhibition of subcutaneous CRC xenograft growth. This was coupled to pro-apoptotic effects resulting in downregulation of XIAP and inhibition of cell survival. We report a novel mechanism by which MK-0646 and OSI-906 elicits cell death in vivo and in vitro. Moreover, these results indicate that MK-0646 and OSI-906 may be potential anticancer candidates for the treatment of patients with IGF-1R-dependent CRC.

Identification of an inhibitory mechanism of luteolin on the insulin-like growth factor-1 ligand-receptor interaction

Using single-molecule force measurement and fluorescence imaging, we have demonstrated that luteolin has an inhibitory effect on IGF-1 ligand-receptor binding, the initial step in IGF-1 signaling. This inhibition mechanism, which was confirmed by flow cytometry and molecular docking, could play a role in cancer therapy.

Evaluation of a novel hexavalent humanized anti-IGF-1R antibody and its bivalent parental IgG in diverse cancer cell lines

A major mechanism of monoclonal antibodies that selectively target the insulin-like growth factor type 1 receptor (IGF-1R) to inhibit tumor growth is by downregulating the receptor, regardless whether they are capable (antagonistic) or incapable (agonistic) of blocking the binding of cognate ligands. We have developed and characterized a novel agonistic anti-IGF-1R humanized antibody, hR1, and used the Dock-and-Lock (DNL) method to construct Hex-hR1, the first multivalent antibody comprising 6 functional Fabs of hR1, with the aim of enhancing potency of hR1. Based on cross-blocking experiments, hR1 recognizes a region of cysteine-rich domain on the α-subunit, different from the epitopes mapped for existing anti-IGF-1R antibodies, yet hR1 is similar to other anti-IGF-1R antibodies in downregulating IGF-1R and inhibiting proliferation, colony formation, or invasion of selected cancer cell lines in vitro, as well as suppressing growth of the RH-30 rhabdomyosarcoma xenograft in nude mice when combined with the mTOR inhibitor, rapamycin. Hex-hR1 and hR1 are generally comparable in their bioactivities under the in-intro and in-vivo conditions investigated. Nevertheless, in selective experiments involving a direct comparison of potency, Hex-hR1 demonstrated a stronger effect on inhibiting cell proliferation stimulated by IGF-1 and could effectively downregulate IGF-1R at a concentration as low as 20 pM.

Phase I/II trial and pharmacokinetic study of cixutumumab in pediatric patients with refractory solid tumors and Ewing sarcoma: a report from the Children's Oncology Group

PURPOSE

A phase I/II study of cixutumumab (IMC-A12) in children with refractory solid tumors was conducted. This study was designed to assess the toxicities, pharmacokinetics, and pharmacodynamics of cixutumumab in children to determine a recommended phase II dose and to assess antitumor activity in Ewing sarcoma (ES).

PATIENTS AND METHODS

Pediatric patients with relapsed or refractory solid tumors were treated with cixutumumab as a 1-hour intravenous infusion once per week. Two dose levels-6 and 9 mg/kg-were evaluated using a standard three-plus-three cohort design. Patients with refractory ES were treated in an expanded phase II cohort at each dose level.

RESULTS

Forty-seven eligible patients with a median age of 15 years (range, 4 to 28 years) were enrolled. Twelve patients were treated in the dose-finding phase. Hematologic and nonhematologic toxicities were generally mild and infrequent. Dose-limiting toxicities included grade 4 thrombocytopenia at 6 mg/kg and grade 3 dehydration at 9 mg/kg. Mean trough concentration (± standard deviation) at 9 mg/kg was 106 ± 57 μg/mL, which exceeded the effective trough concentration of 60 μg/mL observed in xenograft models. Three patients with ES had confirmed partial responses: one of 10 at 6 mg/kg and two of 20 at 9 mg/kg. Serum insulin-like growth factor I (IGF-I) levels consistently increased after one dose of cixutumumab. Tumor IGF-I receptor expression by immunohistochemistry did not correlate with response in patients with ES.

CONCLUSION

Cixutumumab is well tolerated in children with refractory solid tumors. The recommended phase II dose is 9 mg/kg. Limited single-agent activity of cixutumumab was seen in ES.

Polyubiquitination of insulin-like growth factor I receptor (IGF-IR) activation loop promotes antibody-induced receptor internalization and down-regulation

Ubiquitination has been implicated in negatively regulating insulin-like growth factor I receptor (IGF-IR) activity. Because of the relative stability of IGF-IR in the presence of ligand stimulation, IGF-IR ubiquitination sites have yet to be mapped and characterized, thus preventing a direct demonstration of how the receptor ubiquitination contributes to downstream molecular cascades. We took advantage of an anti-IGF-IR antibody (h10H5) that induces more efficient receptor down-regulation to show that IGF-IR is promptly and robustly ubiquitinated. The ubiquitination sites were mapped to the two lysine residues in the IGF-IR activation loop (Lys-1138 and Lys-1141) and consisted of polyubiquitin chains formed through both Lys-48 and Lys-29 linkages. Mutation of these ubiquitinated lysine residues resulted in decreased h10H5-induced IGF-IR internalization and down-regulation as well as a reduced cellular response to h10H5 treatment. We have therefore demonstrated that IGF-IR ubiquitination contributes critically to the down-regulating and antiproliferative activity of h10H5. This finding is physiologically relevant because insulin-like growth factor I appears to mediate ubiquitination of the same major sites as h10H5 (albeit to a lesser extent), and ubiquitination is facilitated by pre-existing phosphorylation of the receptor in both cases. Furthermore, identification of a breast cancer cell line with a defect in IGF-IR ubiquitination suggests that this could be an important tumor resistance mechanism to evade down-regulation-mediated negative regulation of IGF-IR activity in cancer.

High IGF-IR activity in triple-negative breast cancer cell lines and tumorgrafts correlates with sensitivity to anti-IGF-IR therapy

PURPOSE

We previously reported an insulin-like growth factor (IGF) gene expression signature, based on genes induced or repressed by IGF-I, which correlated with poor prognosis in breast cancer. We tested whether the IGF signature was affected by anti-IGF-I receptor (IGF-IR) inhibitors and whether the IGF signature correlated with response to a dual anti-IGF-IR/insulin receptor (InsR) inhibitor, BMS-754807.

EXPERIMENTAL DESIGN

An IGF gene expression signature was examined in human breast tumors and cell lines and changes were noted following treatment of cell lines or xenografts with anti-IGF-IR antibodies or tyrosine kinase inhibitors. Sensitivity of cells to BMS-754807 was correlated with levels of the IGF signature. Human primary tumorgrafts were analyzed for the IGF signature and IGF-IR levels and activity, and MC1 tumorgrafts were treated with BMS-754807 and chemotherapy.

RESULTS

The IGF gene expression signature was reversed in three different models (cancer cell lines or xenografts) treated with three different anti-IGF-IR therapies. The IGF signature was present in triple-negative breast cancers (TNBC) and TNBC cell lines, which were especially sensitive to BMS-754807, and sensitivity was significantly correlated to the expression of the IGF gene signature. The TNBC primary human tumorgraft MC1 showed high levels of both expression and activity of IGF-IR and IGF gene signature score. Treatment of MC1 with BMS-754807 showed growth inhibition and, in combination with docetaxel, tumor regression occurred until no tumor was palpable. Regression was associated with reduced proliferation, increased apoptosis, and mitotic catastrophe.

CONCLUSIONS

These studies provide a clear biological rationale to test anti-IGF-IR/InsR therapy in combination with chemotherapy in patients with TNBC.

Multiple signaling pathways induced by hexavalent, monospecific, anti-CD20 and hexavalent, bispecific, anti-CD20/CD22 humanized antibodies correlate with enhanced toxicity to B-cell lymphomas and leukemias

We have generated hexavalent antibodies (HexAbs) comprising 6 Fabs tethered to one Fc of human IgG1. Three such constructs, 20-20, a monospecific HexAb comprising 6 Fabs of veltuzumab (humanized anti-CD20 immunoglobulin G1κ [IgG1κ]), 20-22, a bispecific HexAb comprising veltuzumab and 4 Fabs of epratuzumab (humanized anti-CD22 IgG1κ), and 22-20, a bispecific HexAb comprising epratuzumab and 4 Fabs of veltuzumab, were previously shown to inhibit pro-liferation of several lymphoma cell lines at nanomolar concentrations in the absence of a crosslinking antibody. We now report an in-depth analysis of the apoptotic and survival signals induced by the 3 HexAbs in Burkitt lymphomas and provide in vitro cytotoxicity data for additional lymphoma cell lines and also chronic lymphocytic leukemia patient specimens. Among the key findings are the significant increase in the levels of phosphorylated p38 and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) by all 3 HexAbs and the notable differences in the signaling events triggered by the HexAbs from those incurred by crosslinking veltuzumab or rituximab with a secondary antibody. Thus, the greatly enhanced direct toxicity of these HexAbs correlates with their ability to alter the basal expression of various intracellular proteins involved in regulating cell growth, survival, and apoptosis, with the net outcome leading to cell death.

Anti-insulin-like growth factor 1 receptor antibody EM164 (murine AVE1642) exhibits anti-tumour activity alone and in combination with temozolomide against neuroblastoma

Insulin-like growth factor 1 receptor (IGF-1R) is overexpressed in many tumours and contributes to tumourigenicity, cell proliferation, metastasis and resistance, thus representing a promising therapeutic target. The human IGF-1R antagonistic monoclonal antibody EM164 (murine AVE1642) has shown activity in adult cancers and is being evaluated in patients with advanced malignancies. We investigated the EM164 for its therapeutic potential against childhood neuroblastoma. EM164 at 0.07, 0.7 and 7 μg/mL exhibited anti-proliferative activity against all nine cell lines tested in (3)H-thymidine incorporation assay in vitro. Cell proliferation after EM164 exposure ranged between 24% and 80% compared to controls. Sensitivity was independent from culture serum conditions, intensity of IGF-1R expression and IGF-II secretion, although associated with inhibition of AKT activation. In vivo, EM164 administered intravenously at 40 mg/kg twice weekly for 4 weeks yielded significant tumour growth delays (TGD) of 13.4d in advanced stage IGR-N91 and 12.9 d in SK-N-AS tumours compared to controls (p = 0.02 and p = 0.0059, respectively). Simultaneous treatment of EM164 0.7 μg/mL and temozolomide resulted in enhanced activity in vitro. In vivo, treatment with temozolomide at the maximum tolerated dose (100mg/kg/d for 5 consecutive days) and EM164 yielded a significantly greater TGD of 29.1d (p<0.01) and two complete tumour regressions (CR) compared to 18.1d (p = ns) and one CR for EM164 alone and 16.1d (p = ns) for temozolomide alone. Our results demonstrate the potential of the anti-IGF-1R antibody alone and in combination with alkylating agents and support the therapeutic development of the AVE1642 for aggressive neuroblastoma.

Targeting the insulin-like growth factor receptor-1R pathway for cancer therapy

Signaling through the insulin-like growth factor receptor (IGF-1R) is required for neoplastic transformation by a number of oncogenes, and preclinical validation studies have suggested IGF-1R is an attractive target for anticancer therapy. A number of small molecules and antibodies targeting IGF-1R have entered clinical development, and early results have suggested that these agents have generally acceptable safety profiles as single agents. Some evidence of antitumor activity has also been reported. This review highlights key aspects of the IGF-1R signaling pathway that implicate it as an attractive therapeutic target in the management of cancer, as well as some key lessons that have emerged from early clinical development of anti-IGF-1R targeting agents. In addition, we consider the importance of selecting indications characterized by pathological alterations in the signaling pathway, rational selection of combinations based on signaling pathway interactions, and strategies for patient selection based on analysis of predictive biomarkers.

Grading the commercial optical biosensor literature-Class of 2008: 'The Mighty Binders'

Optical biosensor technology continues to be the method of choice for label-free, real-time interaction analysis. But when it comes to improving the quality of the biosensor literature, education should be fundamental. Of the 1413 articles published in 2008, less than 30% would pass the requirements for high-school chemistry. To teach by example, we spotlight 10 papers that illustrate how to implement the technology properly. Then we grade every paper published in 2008 on a scale from A to F and outline what features make a biosensor article fabulous, middling or abysmal. To help improve the quality of published data, we focus on a few experimental, analysis and presentation mistakes that are alarmingly common. With the literature as a guide, we want to ensure that no user is left behind.

Reversal of oncogene transformation and suppression of tumor growth by the novel IGF1R kinase inhibitor A-928605

Background

The insulin-like growth factor (IGF) axis is an important signaling pathway in the growth and survival of many cell and tissue types. This pathway has also been implicated in many aspects of cancer progression from tumorigenesis to metastasis. The multiple roles of IGF signaling in cancer suggest that inhibition of the pathway might yield clinically effective therapeutics.

Methods

We describe A-928605, a novel pyrazolo [3,4-d]pyrimidine small molecule inhibitor of the receptor tyrosine kinases (IGF1R and IR) responsible for IGF signal transduction. This compound was first tested for its activity and selectivity via conventional in vitro kinome profiling and cellular IGF1R autophosphorylation. Additionally, cellular selectivity and efficacy of A-928605 were analyzed in an IGF1R oncogene-addicted cell line by proliferation, signaling and microarray studies. Finally, in vivo efficacy of A-928605 was assessed in the oncogene-addicted cell line and in a neuroblastoma model as a single agent as well as in combination with clinically approved therapeutics targeting EGFR in models of pancreatic and non-small cell lung cancers.

Results

A-928605 is a selective IGF1R inhibitor that is able to abrogate activation of the pathway both in vitro and in vivo. This novel compound dosed as a single agent is able to produce significant growth inhibition of neuroblastoma xenografts in vivo. A-928605 is also able to provide additive effects when used in combination with clinically approved agents directed against EGFR in non-small cell lung and human pancreatic tumor models.

Conclusion

These results suggest that a selective IGF1R inhibitor such as A-928605 may provide a useful clinical therapeutic for IGF pathway affected tumors and warrants further investigation.

Molecular predictors of response to a humanized anti-insulin-like growth factor-I receptor monoclonal antibody in breast and colorectal cancer

The insulin-like growth factor-I receptor (IGF-IR) pathway is required for the maintenance of the transformed phenotype in neoplastic cells and hence has been the subject of intensive drug discovery efforts. A key aspect of successful clinical development of targeted therapies directed against IGF-IR will be identification of responsive patient populations. Toward that end, we have endeavored to identify predictive biomarkers of response to an anti-IGF-IR-targeting monoclonal antibody in preclinical models of breast and colorectal cancer. We find that levels of the IGF-IR itself may have predictive value in these tumor types and identify other gene expression predictors of in vitro response. Studies in breast cancer models suggest that IGF-IR expression is both correlated and functionally linked with estrogen receptor signaling and provide a basis for both patient stratification and rational combination therapy with antiestrogen-targeting agents. In addition, we find that levels of other components of the signaling pathway such as the adaptor proteins IRS1 and IRS2, as well as the ligand IGF-II, have predictive value and report on the development of a pathway-focused panel of diagnostic biomarkers that could be used to test these hypotheses during clinical development of IGF-IR-targeting therapies.

Characterization of inhibitory anti-insulin-like growth factor receptor antibodies with different epitope specificity and ligand-blocking properties: implications for mechanism of action in vivo

Therapeutic antibodies directed against the type 1 insulin-like growth factor receptor (IGF-1R) have recently gained significant momentum in the clinic because of preliminary data generated in human patients with cancer. These antibodies inhibit ligand-mediated activation of IGF-1R and the resulting down-stream signaling cascade. Here we generated a panel of antibodies against IGF-1R and screened them for their ability to block the binding of both IGF-1 and IGF-2 at escalating ligand concentrations (>1 microm) to investigate allosteric versus competitive blocking mechanisms. Four distinct inhibitory classes were found as follows: 1) allosteric IGF-1 blockers, 2) allosteric IGF-2 blockers, 3) allosteric IGF-1 and IGF-2 blockers, and 4) competitive IGF-1 and IGF-2 blockers. The epitopes of representative antibodies from each of these classes were mapped using a purified IGF-1R library containing 64 mutations. Most of these antibodies bound overlapping surfaces on the cysteine-rich repeat and L2 domains. One class of allosteric IGF-1 and IGF-2 blocker was identified that bound a separate epitope on the outer surface of the FnIII-1 domain. Using various biophysical techniques, we show that the dual IGF blockers inhibit ligand binding using a spectrum of mechanisms ranging from highly allosteric to purely competitive. Binding of IGF-1 or the inhibitory antibodies was associated with conformational changes in IGF-1R, linked to the ordering of dynamic or unstructured regions of the receptor. These results suggest IGF-1R uses disorder/order within its polypeptide sequence to regulate its activity. Interestingly, the activity of representative allosteric and competitive inhibitors on H322M tumor cell growth in vitro was reflective of their individual ligand-blocking properties. Many of the antibodies in the clinic likely adopt one of the inhibitory mechanisms described here, and the outcome of future clinical studies may reveal whether a particular inhibitory mechanism leads to optimal clinical efficacy.

Insulin and insulin-like growth factor signalling in neoplasia

Insulin and insulin-like growth factors (IGFs) are well known as key regulators of energy metabolism and growth. There is now considerable evidence that these hormones and the signal transduction networks they regulate have important roles in neoplasia. Epidermiological, clinical and laboratory research methods are being used to investigate novel cancer prevention and treatment strategies related to insulin and IGF signalling. Pharmacological strategies under study include the use of novel receptor-specific antibodies, receptor kinase inhibitors and AMP-activated protein kinase activators such as metformin. There is evidence that insulin and IGF signalling may also be relevant to dietary and lifestyle factors that influence cancer risk and cancer prognosis. Recent results are encouraging and have justified the expansion of many translational research programmes.