IGF1R blockade with ganitumab results in systemic effects on the GH-IGF axis in mice

Manipulating the tumor immune microenvironment to improve cancer immunotherapy: IGF1R, a promising target

Cancer immunotherapy has made impressive advances in improving the outcome of patients affected by malignant diseases. Nonetheless, some limitations still need to be tackled to more efficiently and safely treat patients, in particular for those affected by solid tumors. One of the limitations is related to the immunosuppressive tumor microenvironment (TME), which impairs anti-tumor immunity. Efforts to identify targets able to turn the TME into a milieu more auspicious to current immuno-oncotherapy is a real challenge due to the high redundancy of the mechanisms involved. However, the insulin-like growth factor 1 receptor (IGF1R), an attractive drug target for cancer therapy, is emerging as an important immunomodulator and regulator of key immune cell functions. Here, after briefly summarizing the IGF1R signaling pathway in cancer, we review its role in regulating immune cells function and activity, and discuss IGF1R as a promising target to improve anti-cancer immunotherapy.

Identification of gene mutations associated with type 1 diabetes by next-generation sequencing in affected Palestinian families

Introduction: Diabetes Mellitus is a group of metabolic disorders characterized by hyperglycemia secondary to insulin resistance or deficiency. It is considered a major health problem worldwide. T1DM is a result of a combination of genetics, epigenetics, and environmental factors. Several genes have been associated with T1DM, including HLA, INS, CTLA4, and PTPN22. However, none of these findings have been based on linkage analysis because it is rare to find families with several diabetic individuals. Two Palestinian families with several afflicted members with variations in the mode of inheritance were identified and selected for this study. This study aimed to identify the putative causative gene(s) responsible for T1DM development in these families to improve our understanding of the molecular genetics of the disease. Methods: One afflicted member from each family was selected for Whole-Exome Sequencing. Data were mapped to the reference of the human genome, and the resulting VCF file data were filtered. The variants with the highest phenotype correlation score were checked by Sanger sequencing for all family members. The confirmed variants were analyzed in silico by bioinformatics tools. Results: In one family, the IGF1R p.V579F variant, which follows autosomal dominant inheritance, was confirmed and segregated in the family. In another family, the NEUROD1 p.P197H variant, which follows autosomal recessive inheritance, was positively confirmed and segregated. Conclusion: IGF1R p.V579F and NEUROD1 p.P197H variants were associated with T1DM development in the two inflicted families. Further analysis and functional assays will be performed, including the generation of mutant model cell systems, to unravel their specific molecular mechanism in the disease development.

Results of TRIO-15, a multicenter, open-label, phase II study of the efficacy and safety of ganitumab in patients with recurrent platinum-sensitive ovarian cancer

BACKGROUND

IGF signaling has been implicated in the pathogenesis and progression of ovarian carcinoma (OC). Single agent activity and safety of ganitumab (AMG 479), a fully human monoclonal antibody against IGF1R that blocks binding of IGF1 and IGF2, were evaluated in patients with platinum-sensitive recurrent OC.

METHODS

Patients with CA125 progression (GCIG criteria) or measurable disease per RECIST following primary platinum-based therapy received 18 mg/kg of ganitumab q3w. The primary endpoint was objective response rate (ORR) assessed per RECIST 1.1 by an independent radiology review committee (IRC) and/or GCIG CA125 criteria. Secondary endpoints included clinical benefit rate (CBR), progression free survival (PFS) and overall survival (OS).

RESULTS

61 pts. were accrued. Objective responses were seen in 5/61 patients (ORR 8.2%, 95% CI, 3.1-18.8) with 1 partial response (PR) by RECIST and 2 complete responses (CR) as well as 2 PR by CA125 criteria. CBR was 80.3% (95% CI, 67.8-89.0%). The median PFS according to RECIST by IRC was 2.1 months (95% CI, 2.0-3.1). The median PFS per RECIST IRC and/or CA125 was 2.0 months (95% CI, 1.8-2.2). The median OS was 21 months (95% CI, 19.5-NA). The most common overall adverse events were fatigue (36.1%) and hypertension (34.4%). Grade 1/2 hyperglycemia occurred in 30.4% of patients. Hypertension (11.5%) and hypersensitivity (8.2%) were the most frequent grade 3 adverse events.

CONCLUSIONS

IGF1R inhibition with ganitumab was well-tolerated, however, our results do not support further study of ganitumab as a single agent in unselected OC patients.

The Combination of Trametinib and Ganitumab is Effective in RAS-Mutated PAX-Fusion Negative Rhabdomyosarcoma Models

PURPOSE

PAX-fusion negative rhabdomyosarcoma (FN RMS) is driven by alterations in the RAS/MAP kinase pathway and is partially responsive to MEK inhibition. Overexpression of IGF1R and its ligands is also observed in FN RMS. Preclinical and clinical studies have suggested that IGF1R is itself an important target in FN RMS. Our previous studies revealed preclinical efficacy of the MEK1/2 inhibitor, trametinib, and an IGF1R inhibitor, BMS-754807, but this combination was not pursued clinically due to intolerability in preclinical murine models. Here, we sought to identify a combination of an MEK1/2 inhibitor and IGF1R inhibitor, which would be tolerated in murine models and effective in both cell line and patient-derived xenograft models of RAS-mutant FN RMS.

EXPERIMENTAL DESIGN

Using proliferation and apoptosis assays, we studied the factorial effects of trametinib and ganitumab (AMG 479), a mAb with specificity for human and murine IGF1R, in a panel of RAS-mutant FN RMS cell lines. The molecular mechanism of the observed synergy was determined using conventional and capillary immunoassays. The efficacy and tolerability of trametinib/ganitumab was assessed using a panel of RAS-mutated cell-line and patient-derived RMS xenograft models.

RESULTS

Treatment with trametinib and ganitumab resulted in synergistic cellular growth inhibition in all cell lines tested and inhibition of tumor growth in four of six models of RAS-mutant RMS. The combination had little effect on body weight and did not produce thrombocytopenia, neutropenia, or hyperinsulinemia in tumor-bearing SCID beige mice. Mechanistically, ganitumab treatment prevented the phosphorylation of AKT induced by MEK inhibition alone. Therapeutic response to the combination was observed in models without a mutation in the PI3K/PTEN axis.

CONCLUSIONS

We demonstrate that combined trametinib and ganitumab is effective in a genomically diverse panel of RAS-mutated FN RMS preclinical models. Our data also show that the trametinib/ganitumab combination likely has a favorable tolerability profile. These data support testing this combination in a phase I/II clinical trial for pediatric patients with relapsed or refractory RAS-mutated FN RMS.

IGF1R acts as a cancer-promoting factor in the tumor microenvironment facilitating lung metastasis implantation and progression

Given the long-term ineffectiveness of current therapies and late-stage diagnoses, lung cancer is a leading cause of malignant diseases. Tumor progression is influenced by cancer cell interactions with the tumor microenvironment (TME). Insulin-like growth factor 1 receptor (IGF1R) was reported to affect the TME; however, the role of IGF1R in lung TME has not been investigated. First, we assessed IGF1R genomic alterations and expression in NSCLC patient tissue samples, as well as IGF1R serum levels. Next, we performed tumor heterotopic transplantation and pulmonary metastases in IGF1R-deficient mice using melanoma and Lewis lung carcinoma (LLC) cells. Herein we report increased amplification and mRNA expression, as well as increased protein expression (IGF1R/p-IGF1R) and IGF1R levels in tumor samples and serum from NSCLC patients, respectively. Moreover, IGF1R deficiency in mice reduced tumor growth, proliferation, inflammation and vascularization, and increased apoptosis after tumor heterotopic transplantation. Following induction of lung metastasis, IGF1R-deficient lungs also demonstrated a reduced tumor burden, and decreased expression of tumor progression markers, p-IGF1R and p-ERK1/2. Additionally, IGF1R-deficient lungs showed increased apoptosis and diminished proliferation, vascularization, EMT and fibrosis, along with attenuated inflammation and immunosuppression. Accordingly, IGF1R deficiency decreased expression of p-IGF1R in blood vessels, fibroblasts, tumor-associated macrophages and FOXP3⁺ tumor-infiltrating lymphocytes. Our results demonstrate that IGF1R promotes metastatic tumor initiation and progression in lung TME. Furthermore, our research indicates that IGF1R could be a potential biomarker for early prediction of drug response and clinical evolution in NSCLC patients.

IGF1R is a mediator of sex-specific metabolism in mice: Effects of age and high-fat diet

OBJECTIVE

We aimed to investigate the short and long-term metabolic consequences of IGF1R systemic gene deficiency in mice.

METHODS

UBC-CreERT2, Igf1r^fl/fl mutant mice were used to suppress IGF1R signaling in adult tissues by inducing postnatal generalized Igf1r deletion with tamoxifen. Animals were analyzed at two different ages: i) 13-weeks old young mice, and ii) 12-months old middle-aged mice. In addition, the effects of 10 weeks-long high-fat diet (HFD) were investigated in middle-aged mice.

RESULTS

Young IGF1R-deficient mice were insulin-resistant, with high IGF1, growth hormone (GH) and IGFBP3, as well as low IGFBP2 circulating levels. Males also presented increased triglycerides in liver. In contrast, middle-aged mice did not clearly show all of these alterations, suggesting possible compensatory effects. Middle-aged IGF1R-deficient male mice were able to counteract the negative effects induced by aging and HFD in adiposity, inflammation and glucose metabolism. A metabolic sexual dimorphism dependent on IGF1R was observed, especially in middle-aged mice.

CONCLUSIONS

These results demonstrate that IGF1R is involved in metabolic homeostasis, with effects modulated by diet-induced obesity and aging in a sex dependent manner. Thus, IGF1R deficiency in mice is proposed as a useful tool to understand metabolic alterations observed in patients with IGF1R gene deletions.

Teprotumumab Efficacy, Safety and Durability in Longer Duration Thyroid Eye Disease and Retreatment: Optic-X Study

OBJECTIVE

Evaluate teprotumumab safety and efficacy in patients with thyroid eye disease (TED) who previously did not respond or who had a disease flare.

DESIGN

OPTIC-X is an open-label (previous treatment masked) teprotumumab treatment and retreatment trial in patients from the randomized double-masked, multicenter, placebo-controlled OPTIC study.

PARTICIPANTS

OPTIC study patients who previously received placebo, 37 patients, or who previously received teprotumumab, 14 patients.

INTERVENTION

OPTIC non-responders and those who flared (≥2mm increase in proptosis, ≥2point increase in clinical activity score [CAS], or both) during follow-up were treated for the first time (previous placebo patients) or retreated with teprotumumab in OPTIC-X with 8 infusions over 24-weeks.

MAIN OUTCOME MEASURES

Proptosis responder rate and safety were examined. Secondary outcomes included proptosis, CAS, subjective diplopia, and quality of life responses.

RESULTS

Thirty-three of 37 (89.2%) placebo-treated OPTIC patients became proptosis responders (mean [standard deviation] -3.5mm [1.7]) when treated with teprotumumab in OPTIC-X. The magnitude of responses was equivalent to those in the OPTIC study. In these responders, proptosis, CAS 0 or 1, and diplopia responses were maintained in 29/32 (90.6%), 20/21 (95.2%), and 12/14 (85.7%), respectively, at week-48 of follow up. These patients had a median TED duration of 12.9 months versus 6.3 months in those treated with teprotumumab in the OPTIC study. Of the 5 OPTIC teprotumumab non-responders retreated in the OPTIC-X study, 2 responded, 1 had a proptosis reduction of 1.5mm from OPTIC baseline and 2 discontinued treatment early. Of the OPTIC teprotumumab responders who flared, 5/8 (62.5%) became responders when retreated (mean proptosis reduction of 1.9mm [1.2] from OPTIC-X baseline, 3.3mm [0.7] from OPTIC baseline). Compared to published double-masked trials and their integrated follow-up, no new safety signals were identified. Mild hearing impairment was reported with 4 events occurring during the first course of treatment and 2 events reoccurring following retreatment.

CONCLUSION

These data indicate that TED patients with longer disease duration respond similarly to those treated earlier in their disease. Patients with an insufficient initial response or flare may benefit from additional teprotumumab therapy. This analysis did not find any new safety risk; however additional post-marketing pharmacovigilance is ongoing.

Pancreatic Adenocarcinoma Therapeutics Targeting RTK and TGF Beta Receptor

Despite the improved overall survival rates in most cancers, pancreatic cancer remains one of the deadliest cancers in this decade. The rigid microenvironment, which majorly comprises cancer-associated fibroblasts (CAFs), plays an important role in the obstruction of pancreatic cancer therapy. To overcome this predicament, the signaling of receptor tyrosine kinases (RTKs) and TGF beta receptor (TGFβR) in both pancreatic cancer cell and supporting CAF should be considered as the therapeutic target. The activation of receptors has been reported to be aberrant to cell cycle regulation, and signal transduction pathways, such as growth-factor induced proliferation, and can also influence the apoptotic sensitivity of tumor cells. In this article, the regulation of RTKs/TGFβR between pancreatic ductal adenocarcinoma (PDAC) and CAFs, as well as the RTKs/TGFβR inhibitor-based clinical trials on pancreatic cancer are reviewed.

The Actions of IGF-1 in the Growth Plate and Its Role in Postnatal Bone Elongation

PURPOSE OF REVIEW

Bone elongation is a complex process driven by multiple intrinsic (hormones, growth factors) and extrinsic (nutrition, environment) variables. Bones grow in length by endochondral ossification in cartilaginous growth plates at ends of developing long bones. This review provides an updated overview of the important factors that influence this process.

RECENT FINDINGS

Insulin-like growth factor-1 (IGF-1) is the major hormone required for growth and a drug for treating pediatric skeletal disorders. Temperature is an underrecognized environmental variable that also impacts linear growth. This paper reviews the current state of knowledge regarding the interaction of IGF-1 and environmental factors on bone elongation. Understanding how internal and external variables regulate bone lengthening is essential for developing and improving treatments for an array of bone elongation disorders. Future studies may benefit from understanding how these unique relationships could offer realistic new approaches for increasing bone length in different growth-limiting conditions.

Late-life targeting of the IGF-1 receptor improves healthspan and lifespan in female mice

Diminished growth factor signaling improves longevity in laboratory models, while a reduction in the somatotropic axis is favorably linked to human aging and longevity. Given the conserved role of this pathway on lifespan, therapeutic strategies, such as insulin-like growth factor-1 receptor (IGF-1R) monoclonal antibodies (mAb), represent a promising translational tool to target human aging. To this end, we performed a preclinical study in 18-mo-old male and female mice treated with vehicle or an IGF-1R mAb (L2-Cmu, Amgen Inc), and determined effects on aging outcomes. Here we show that L2-Cmu preferentially improves female healthspan and increases median lifespan by 9% (P = 0.03) in females, along with a reduction in neoplasms and inflammation (P ≤ 0.05). Thus, consistent with other models, targeting IGF-1R signaling appears to be most beneficial to females. Importantly, these effects could be achieved at advanced ages, suggesting that IGF-1R mAbs could represent a promising therapeutic candidate to delay aging.

Loss of neutrophil polarization in colon carcinoma liver metastases of mice with an inducible, liver-specific IGF-I deficiency

The growth of cancer metastases in the liver depends on a permissive interaction with the hepatic microenvironment and neutrophils can contribute to this interaction, either positively or negatively, depending on their phenotype. Here we investigated the role of IGF-I in the control of the tumor microenvironment in the liver, using mice with a conditional, liver-specific, IGF-I deficiency (iLID) induced by a single tamoxifen injection. In mice that had a sustained (3 weeks) IGF-I deficiency prior to the intrasplenic/portal inoculation of colon carcinoma MC-38 cells, we observed an increase in neutrophil accumulation in the liver relative to controls. However, unlike controls, these neutrophils did not acquire the (anti-inflammatory) tumor-promoting phenotype, as evidenced by retention of high ICAM-1 expression and nitric oxide production and low CXCR4, CCL5, and VEGF expression and arginase production, all characteristic of the (pro-inflammatory) phenotype. This coincided with an increase in apoptotic tumor cells and reduced metastasis. Neutrophils isolated from these mice also had reduced IGF-IR expression levels. These changes were not observed in iLID mice with a short-term (2 days) IGF-I depletion, despite a 70% reduction in their circulating IGF-I levels, indicating that a sustained IGF-I deficiency was necessary to alter the neutrophil phenotype. Similar results were obtained with the highly metastatic Lewis lung carcinoma subline H-59 cells and in mice injected with an IGF-Trap that blocks IGF-IR signaling by reducing ligand bioavailability. Our results implicate the IGF axis in neutrophil polarization and the induction of a pro-metastatic microenvironment in the liver.

Function of insulin-like growth factor 1 receptor in cancer resistance to chemotherapy

Drug resistance is a primary cause of chemotherapeutic failure; however, how this resistance develops is complex. A comprehensive understanding of chemotherapeutic resistance mechanisms may aid in identifying more effective drugs and improve the survival rates of patients with cancer. Insulin-like growth factor 1 receptor (IGF1R), a member of the insulin receptor family, has been extensively assessed for biological activity, and its putative contribution to tumor cell development and progression. Furthermore, researchers have attended to drugs that target IGF1R since IGF1R functions as a membrane receptor. However, how IGF1R participates in chemotherapeutic resistance remains unclear. Therefore, the present study described the IGF1R gene and its associated signaling pathways, and offered details of IGF1R-induced tumor chemoresistance associated with promoting cell proliferation, inhibition of apoptosis, regulation of ATP-binding cassette transporter proteins and interactions with the extracellular matrix. The present study offered additional explanations for tumor chemotherapy resistance and provided a theoretical basis of IGF1R and its downstream pathways for future possible chemotherapy treatment options.

Attenuated airway hyperresponsiveness and mucus secretion in HDM-exposed Igf1r-deficient mice

BACKGROUND

Asthma is a common chronic lung disease characterized by airflow obstruction, airway hyperresponsiveness (AHR), and airway inflammation. IGFs have been reported to play a role in asthma, but little is known about how the insulin-like growth factor 1 receptor (IGF1R) affects asthma pathobiology.

METHODS

Female Igf1r-deficient and control mice were intranasally challenged with house dust mite (HDM) extract or PBS five days per week for four weeks. Lung function measurements, and bronchoalveolar lavage fluid (BALF), serum, and lungs were collected on day 28 for further cellular, histological, and molecular analysis.

RESULTS

Following HDM exposure, the control mice responded with a marked AHR and airway inflammation. The Igf1r-deficient mice exhibited an increased expression of the IGF system and surfactant genes, which were decreased in a similar manner for control and Igf1r-deficient mice after HDM exposure. On the other hand, the Igf1r-deficient mice exhibited no AHR, and a selective decrease in blood and BALF eosinophils, lung Il13 levels, collagen, and smooth muscle, as well as a significant depletion of goblet cell metaplasia and mucus secretion markers after HDM exposure. The Igf1r-deficient mice displayed a distinctly thinner epithelial layer than control mice, but this was not altered by HDM.

CONCLUSIONS

Herein, we demonstrate by the first time that the Igf1r plays an important role in murine asthma, mediating both AHR and mucus secretion after HDM exposure. Thus, our study identifies IGF1R as a potential therapeutic target, not only for asthma but also for hypersecretory airway diseases.

IGF1R deficiency attenuates acute inflammatory response in a bleomycin-induced lung injury mouse model

IGF1R (Insulin-like Growth Factor 1 Receptor) is a tyrosine kinase with pleiotropic cellular functions. IGF activity maintains human lung homeostasis and is implicated in pulmonary diseases such as cancer, ARDS, COPD, asthma and fibrosis. Here we report that lung transcriptome analysis in mice with a postnatally-induced Igf1r gene deletion showed differentially expressed genes with potentially protective roles related to epigenetics, redox and oxidative stress. After bleomycin-induced lung injury, IGF1R-deficient mice demonstrated improved survival within a week. Three days post injury, IGF1R-deficient lungs displayed changes in expression of IGF system-related genes and reduced vascular fragility and permeability. Mutant lungs presented reduced inflamed area, down-regulation of pro-inflammatory markers and up-regulation of resolution indicators. Decreased inflammatory cell presence in BALF was reflected in diminished lung infiltration mainly affecting neutrophils, also corroborated by reduced neutrophil numbers in bone marrow, as well as reduced lymphocyte and alveolar macrophage counts. Additionally, increased SFTPC expression together with hindered HIF1A expression and augmented levels of Gpx8 indicate that IGF1R deficiency protects against alveolar damage. These findings identify IGF1R as an important player in murine acute lung inflammation, suggesting that targeting IGF1R may counteract the inflammatory component of many lung diseases.

Involvement of Igf1r in Bronchiolar Epithelial Regeneration: Role during Repair Kinetics after Selective Club Cell Ablation

Regeneration of lung epithelium is vital for maintaining airway function and integrity. An imbalance between epithelial damage and repair is at the basis of numerous chronic lung diseases such as asthma, COPD, pulmonary fibrosis and lung cancer. IGF (Insulin-like Growth Factors) signaling has been associated with most of these respiratory pathologies, although their mechanisms of action in this tissue remain poorly understood. Expression profiles analyses of IGF system genes performed in mouse lung support their functional implication in pulmonary ontogeny. Immuno-localization revealed high expression levels of Igf1r (Insulin-like Growth Factor 1 Receptor) in lung epithelial cells, alveolar macrophages and smooth muscle. To further understand the role of Igf1r in pulmonary homeostasis, two distinct lung epithelial-specific Igf1r mutant mice were generated and studied. The lack of Igf1r disturbed airway epithelial differentiation in adult mice, and revealed enhanced proliferation and altered morphology in distal airway club cells. During recovery after naphthalene-induced club cell injury, the kinetics of terminal bronchiolar epithelium regeneration was hindered in Igf1r mutants, revealing increased proliferation and delayed differentiation of club and ciliated cells. Amid airway restoration, lungs of Igf1r deficient mice showed increased levels of Igf1, Insr, Igfbp3 and epithelial precursor markers, reduced amounts of Scgb1a1 protein, and alterations in IGF signaling mediators. These results support the role of Igf1r in controlling the kinetics of cell proliferation and differentiation during pulmonary airway epithelial regeneration after injury.

Insulin-like growth factor axis targeting in cancer and tumour angiogenesis - the missing link

Numerous molecular players in the process of tumour angiogenesis have been shown to offer potential for therapeutic targeting. Initially denoted to be involved in malignant transformation and tumour progression, the insulin-like growth factor (IGF) signalling axis has been subject to therapeutic interference, albeit with limited clinical success. More recently, IGFs and their receptors have received attention for their contribution to tumour angiogenesis, which offers novel therapeutic opportunities. Here we review the contribution of this signalling axis to tumour angiogenesis, the mechanisms of resistance to therapy and the interplay with other pro-angiogenic pathways, to offer insight in the renewed interest in the application of IGF axis targeting agents in anti-cancer combination therapies.

The type I insulin-like growth factor regulates the liver stromal response to metastatic colon carcinoma cells

Hepatic stellate cells (HSC) play a major role in initiating the liver fibrogenic (wounding) response of the liver and can also orchestrate a pro-metastatic microenvironment in the liver in response to invading cancer cells. Here we explored the role of the hepatic stellate cells in colon carcinoma liver metastasis with emphasis on the contribution of the insulin-like growth factor (IGF) axis to their activation and function. To this end, we used mice with a Tamoxifen inducible liver IGF-I deficiency. We found that in mice with a sustained IGF-I deficiency, recruitment and activation of HSC into tumor-infiltrated areas of the liver were markedly diminished, resulting in decreased collagen deposition and reduced tumor expansion. In addition, IGF-I could rescue HSC from apoptosis induced by pro-inflammatory factors such as TNF-α known to be upregulated in the early stages of liver metastasis. Moreover, in surgical specimens, activated IGF-IR was observed on HSC-like stromal cells surrounding colorectal carcinoma liver metastases. Finally, IGF-targeting in vivo using an IGF-Trap caused a significant reduction in HSC activation in response to metastatic colon cancer cells. Therefore, our data identify IGF as a survival factor for HSC and thereby, a promoter of the pro-metastatic microenvironment in the liver. IGF-targeting could therefore provide a strategy for curtailing the pro-metastatic host response of the liver during the early stages of liver metastasis.

Minireview: Were the IGF Signaling Inhibitors All Bad?

Preclinical studies in the 1980s defined a role for IGF signaling in the development and sustainability of the malignant process. Subsequently, antibody, tyrosine kinase, and ligand inhibitors of the IGF receptor were manufactured. In the past decade, numerous clinical trials have tested the efficacy of IGF receptor inhibitors in the treatment of advanced tumors. Early-phase trials in heavily pretreated populations showed promise with complete or partial responses in a few patients and stable disease in many more. Unfortunately, the results of the early-phase trials did not pan out to later-phase trials. The lack of use of biomarkers to define subsets of patients that may benefit from IGF receptor blockade and compensatory signaling via other growth factor receptors such as the insulin, GH, and epidermal growth factor receptors may have played a role in the lack of efficacy of IGF receptor inhibition in phase III trials. Although these trials failed to show benefit, the trials have revealed previously unknown knowledge regarding the complex nature of IGF signaling. The knowledge obtained from these trials will be useful in designing future trials studying inhibitors of growth factor signaling.

Role of IGF1-(CA)19 promoter microsatellite in the clinical presentation of acromegaly

BACKGROUND

A highly polymorphic Cytosine-Adenosine (CA) repeat sequence microsatellite has been identified in the promoter region of IGF1 gene. Several studies investigated the relationship between IGF1-(CA)n polymorphism and IGF1 levels, with conflicting results. Aim of this study was to investigate the influence of this polymorphism on clinical and biochemical characteristics of acromegalic patients.

METHODS

Eighty-eight acromegalic patients and 104 normal subjects were included in the study. Blood DNA was extracted and analysed by microsatellite technique using capillary electrophoresis. Patients and controls were subdivided in 19/19 [homozygous for the (CA)19 allele], 19/X [heterozygous for the (CA)19 allele] and X/X (any other genotype).

RESULTS

The genotype frequency was significantly different between patients and controls, the proportion of 19/19 being lower (28·4% vs. 50·0%) and 19/X and X/X higher in acromegalic patients than in controls (P = 0·004). There were no significant differences in age, gender, basal and nadir GH, IGF1-SDS, tumour size, metabolic parameters, outcome and treatment among the three groups. The different frequency of genotypes in acromegalic patients vs. controls, as well as the lack of relationship between IGF1-(CA)n polymorphism and clinical and biochemical data in acromegalic patients, was confirmed using an additional alternative genotyping considering (CA)19 and (CA)20 homozygotes and heterozygotes vs. alleles with more than 19 of 20 repeats or less.

CONCLUSIONS

Our results do not support the hypothesis that IGF-(CA)n alleles may have a significant role in determining clinical, biochemical and outcome of patients with acromegaly. The possible role of IGF1 polymorphism on susceptibility to acromegaly remains to be investigated.