Itay Bentov

Similarities and differences between insulin and IGF-I: Structures, receptors, and signalling pathways

Abstract Insulin and the insulin-like growth factors (IGF-I, IGF-II) are pleiotropic hormones that have multiple roles in regulating vital metabolic and developmental processes. Although most early data suggested that insulin is mainly involved in metabolic activities (e.g. control of sugar levels) and IGF-I/II control growth and differentiation events (e.g. bone elongation, cell division), today, it is clear that there is cross-talk between the various ligands and receptors of the IGF family. As a result of these complex interactions, the spectrum of activities that were classically assigned to insulin or IGF-I/II has greatly expanded, and the signalling events mediated by the insulin and IGF receptors is the subject of intensive research. This review provides a comparative analysis of the structures, receptors, and signalling pathways of insulin and IGF-I.

Anesthesia, microcirculation, and wound repair in aging.

Age-related changes in skin contribute to impaired wound healing after surgical procedures. Changes in skin with age include decline in thickness and composition, a decrease in the number of most cell types, and diminished microcirculation. The microcirculation provides tissue perfusion, fluid homeostasis, and delivery of oxygen and other nutrients. It also controls temperature and the inflammatory response. Surgical incisions cause further disruption of the microvasculature of aged skin. Perioperative management can be modified to minimize insults to aged tissues. Judicious use of fluids, maintenance of normal body temperature, pain control, and increased tissue oxygen tension are examples of adjustable variables that support the microcirculation. Anesthetic agents influence the microcirculation of a combination of effects on cardiac output, arterial pressure, and local microvascular changes. The authors examined the role of anesthetic management in optimizing the microcirculation and potentially improving postoperative wound repair in older persons.

p53 Regulates insulin-like growth factor-I receptor gene expression in uterine serous carcinoma and predicts responsiveness to an insulin-like growth factor-I receptor-directed targeted therapy.

The role of the insulin-like growth factors (IGF) in endometrial cancer has been well established. The IGF-I receptor (IGF-IR), which mediates the biological actions of IGF-I, is usually overexpressed in endometrial tumours. Uterine serous carcinoma (USC) constitutes a defined histological category among endometrial cancers. Mutation of the p53 gene appears early in the course of the disease and is considered a key event in the initiation of USC. The aim of the present study was to evaluate the potential interactions between p53 and the IGF-IR in USC. In addition, we investigated the role of p53 as a biomarker in IGF-IR targeted therapies. Immunohistochemical analysis in a collection of 35 USC specimens revealed that IGF-IR is highly expressed in primary and metastatic USC. Likewise, p53 was expressed in 85.7% of primary tumours and 100% of metastases. A significant negative correlation between p53 expression and survival was noticed. In addition, using USC-derived cell lines we provide evidence that p53 regulates IGF-IR gene expression via a mechanism that involves repression of the IGF-IR promoter. We show that the mechanism of action of p53 involves interaction with zinc finger protein Sp1, a potent transactivator of the IGF-IR gene. Finally, we demonstrate that USC tumours overexpressing p53 are more likely to benefit from anti-IGF-IR therapies. In summary, we provide evidence that p53 regulates IGF-IR gene expression in USC cells via a mechanism that involves repression of the IGF-IR promoter. The interplay between the p53 and IGF-I signalling pathways is of major basic and translational relevance.

Insulin-like growth factor-I receptor (IGF-IR) targeting with monoclonal antibody cixutumumab (IMC-A12) inhibits IGF-I action in endometrial cancer cells

Specific insulin-like growth factor-I receptor (IGF-IR) targeting emerged in recent years as a promising therapeutic strategy in cancer. Endometrial cancer is the most common gynaecological cancer in the Western world. The aim of this study was to evaluate the potential of cixutumumab (IMC-A12, ImClone Systems), a fully human monoclonal antibody against the IGF-IR, to inhibit IGF-I-mediated biological actions and cell signalling events in four endometrial carcinoma-derived cell lines (ECC-1, Ishikawa, USPC-1 and USPC-2). Our results demonstrate that cixutumumab was able to block the IGF-I-induced autophosphorylation of the IGF-IR. In addition, the PI3K and MAPK downstream signalling pathways were also inactivated by cixutumumab in part of the cell lines. Prolonged (24h and 48h) exposures to cixutumumab reduced IGF-IR expression. Furthermore, confocal microscopy of GFP-tagged receptors shows that cixutumumab treatment led to IGF-IR redistribution from the cell membrane to the cytoplasm. Antiapoptotic effects were evaluated by cleavage of caspase 3 and PARP, and mitogenicity and transformation by proliferation and cell cycle assays. Results obtained showed that cixutumumab abrogated the IGF-I-stimulated increase in proliferation rate, and increased caspase-3 and PARP cleavage, two markers of apoptosis. Of importance, cixutumumab had no effect neither on insulin receptor (IR) expression nor on IGF-I activation of IR. In summary, in a cellular model of endometrial cancer cixutumumab was able to inhibit the IGF-I-induced activation of intracellular cascades, apoptosis and proliferation.

The effect of aging on the cutaneous microvasculature.

Aging is associated with a progressive loss of function in all organs. Under normal conditions the physiologic compensation for age-related deficits is sufficient, but during times of stress the limitations of this reserve become evident. Explanations for this reduction in reserve include the changes in the microcirculation that occur during the normal aging process. The microcirculation is defined as the blood flow through arterioles, capillaries and venules, which are the smallest vessels in the vasculature and are embedded within organs and tissues. Optimal strategies to maintain the microvasculature following surgery and other stressors must use multifactorial approaches. Using skin as the model organ, we will review the anatomical and functional changes in the microcirculation with aging, and some of the available clinical strategies to potentially mitigate the effect of these changes on important clinical outcomes.

Insulin-like growth factor-I receptor inhibition by specific tyrosine kinase inhibitor NVP-AEW541 in endometrioid and serous papillary endometrial cancer cell lines

PURPOSE The role of the insulin-like growth factor (IGF) system in endometrial cancer has been well established. The IGF-I receptor (IGF-IR) emerged as a promising therapeutic target in a number of cancers. NVP-AEW541 (Novartis Pharma) is a pyrrolo(2,3-d)pyrimidine derivative with specific IGF-IR tyrosine kinase inhibitory activity. NVP-AEW541 has been shown to abrogate IGF-I-mediated IGF-IR autophosphorylation and to reduce activation of the IGF-IR signaling pathways. The aim of the present study was to investigate the anti-proliferative activity of NVP-AEW541 in Type I (endometrioid) and Type II (uterine serous papillary endometrial carcinoma, USPC) endometrial cancer cell lines. METHODS Type I (ECC-1, Ishikawa) and Type II (USPC-1, USPC-2) endometrial cancer cell lines were treated with NVP-AEW541 in the presence of IGF-I, and the following parameters were measured: IGF-IR, AKT and ERK phosphorylation, apoptosis, proliferation, cell cycle progression and IGF-IR internalization. RESULTS Results obtained showed that NVP-AEW541 abolished the IGF-I stimulated IGF-IR phosphorylation in all of the cell lines investigated, whereas it abolished AKT and ERK phosphorylation preferentially in ECC-1 and USPC-1 cells. Furthermore, the inhibitor prevented from IGF-I from exerting its antiapoptotic effect in ECC-1, USPC-1 and USPC-2 cells. In addition, proliferation assays showed that NVP-AEW541 caused a decrease in proliferation rate in all of the cell lines. NVP-AEW541 had no major effect on the insulin receptor. CONCLUSION Our results suggest that specific IGF-IR inhibition by NVP-AEW541 might be a promising therapeutic tool in endometrial cancer.

Transcription factor E2F1 is a potent transactivator of the insulin-like growth factor-I receptor (IGF-IR) gene.

OBJECTIVES The insulin-like growth factor-I receptor (IGF-IR) plays an important role in cancer development. The E2F1 transcription factor activates S-phase promoting genes and mediates apoptosis. Microarray analyses of E2F1-induced genes revealed that genes associated with proliferation as well as apoptosis are upregulated by E2F1. Among other candidate genes, DNA microarrays identified the IGF-IR gene as a putative E2F1 target. The aim of this study was to investigate the involvement of E2F1 in regulation of IGF-IR gene transcription. METHODS To examine the potential regulation of IGF-IR gene expression by E2F1, an E2F1 expression vector was transfected into P69 and M12 prostate cancer cell lines, after which IGF-IR levels were measured by Western blots. Transient transfections were used to evaluate IGF-IR promoter activity and chromatin immunoprecipitation (ChIP) assays were employed to assess E2F1-binding to the IGF-IR promoter. RESULTS Results obtained showed that E2F1 expression induced a significant increment in endogenous IGF-IR levels. ChIP assays showed enhanced E2F1-binding to the IGF-IR promoter in E2F1-expressing cells. Transient coexpression of an E2F1 vector along with an IGF-IR promoter-luciferase reporter resulted in a approximately 140-fold increase in IGF-IR promoter activity. Furthermore, deletion and bioinformatic analyses indicate that the ability of E2F1 to stimulate IGF-IR promoter activity was correlated with the number of E2F1 sites in the promoter region. CONCLUSIONS In summary, we provide evidence that E2F1 regulates IGF-IR gene transcription in prostate cancer cells via a mechanism that involves direct binding to specific elements in the proximal IGF-IR promoter.

Insulin-Like Growth Factor-I Regulates Krüppel-Like Factor-6 Gene Expression in a p53-Dependent Manner

High-circulating IGF-I concentrations are associated with an increased risk for breast, prostate, and colorectal cancer. Krüppel-like factor-6 (KLF6) is a zinc finger tumor suppressor inactivated in prostate and other types of cancer. We have previously demonstrated that KLF6 is a potent transactivator of the IGF-I receptor promoter. The aim of the present study was to examine the potential regulation of KLF6 gene expression by IGF-I. The human colon cancer cell lines HCT116 +/+ and -/- (with normal and disrupted p53, respectively) were treated with IGF-I. Western blots, quantitative RT-PCR, and transfection assays were used to evaluate the effect of IGF-I on KLF-6 production. Signaling pathway inhibitors were used to identify the mechanisms responsible for regulation of KLF6 expression. Small interfering RNA against p53 and KLF6 was used to assess the role of p53 in regulation of KLF6 expression by IGF-I and to evaluate KLF6 involvement in cell cycle control. Results obtained showed that IGF-I stimulated KLF-6 transcription in cells with normal, but not disrupted, p53, suggesting that KLF6 is a downstream target for IGF-I action. Stimulation of KLF6 expression by IGF-I in a p53-dependent manner may constitute a novel mechanism of action of IGF-I, with implications in normal cell cycle progression and cancer biology.

Hyaluronan enhances wound repair and increases collagen III in aged dermal wounds

Age‐related changes in the extracellular matrix contribute to delayed wound repair in aging. Hyaluronan, a linear nonsulfated glycosaminoglycan, promotes synthesis and assembly of key extracellular matrix components, such as the interstitial collagens, during wound healing. The biological effects of hyaluronan are mediated, in part, by hyaluronan size. We have previously determined that dermal wounds in aged mice, relative to young mice, have deficits in the generation of lower molecular weight hyaluronan (defined as <300 kDa). Here, we tested the effect of exogenous hyaluronan of 2, 250, or 1,000 kDa sizes on full‐thickness excisional wounds in aged mice. Only wounds treated with 250 kDa hyaluronan (HA250) were significantly improved over wounds that received carrier (water) alone. Treatment with HA250 was associated with increased expression of transcripts for the hyaluronan receptors CD44 and RHAMM, as well as collagens III and I. Analyses of dermal protein content by mass spectrometry and Western blotting confirmed significantly increased expression of collagen III in wounds treated with HA250 relative to control wounds. In summary, we find that HA250 improves wound repair and increases the synthesis of collagen III in aged dermal wounds.

Association of Radiologic Indicators of Frailty With 1-Year Mortality in Older Trauma Patients: Opportunistic Screening for Sarcopenia and Osteopenia

Importance Assessment of physical frailty in older trauma patients admitted to the intensive care unit is often not feasible using traditional frailty assessment instruments. The use of opportunistic computed tomography (CT) scans to assess sarcopenia and osteopenia as indicators of underlying frailty may provide complementary prognostic information on long-term outcomes. Objective To determine whether sarcopenia and/or osteopenia are associated with 1-year mortality in an older trauma patient population. Design, Setting, and Participants A retrospective cohort constructed from a state trauma registry was linked to the statewide death registry and Comprehensive Hospital Abstract Reporting System for readmission data analyses. Admission abdominopelvic CT scans from patients 65 years and older admitted to the intensive care unit of a single level I trauma center between January 2011 and May 2014 were analyzed to identify patients with sarcopenia and/or osteopenia. Patients with a head Injury Severity Score of 3 or greater, an out-of-state address, or inadequate CT imaging or who died within 24 hours of admission were excluded. Exposures Sarcopenia and/or osteopenia, assessed via total cross-sectional muscle area and bone density at the L3 vertebral level, compared with a group with no sarcopenia or osteopenia. Main Outcomes and Measures One-year all-cause mortality. Secondary outcomes included 30-day all-cause mortality, 30-day readmission, hospital length of stay, hospital cost, and discharge disposition. Results Of the 450 patients included in the study, 269 (59.8%) were male and 394 (87.6%) were white. The cohort was split into 4 groups: 74 were retrospectively diagnosed with both sarcopenia and osteopenia, 167 with sarcopenia only, 48 with osteopenia only, and 161 with no radiologic indicators. Among the 408 who survived to discharge, sarcopenia and osteopenia were associated with higher risks of 1-year mortality alone and in combination. After adjustment, the hazard ratio was 9.4 (95% CI, 1.2-75.4; P = .03) for sarcopenia and osteopenia, 10.3 (95% CI, 1.3-78.8; P = .03) for sarcopenia, and 11.9 (95% CI, 1.3-107.4; P = .03) for osteopenia. Conclusions and Relevance More than half of older trauma patients in this study had sarcopenia, osteopenia, or both. Each factor was independently associated with increased 1-year mortality. Given the prevalent use of abdominopelvic CT in trauma centers, opportunistic screening for radiologic indicators of frailty provides an additional tool for early identification of older trauma patients at high risk for poor outcomes, with the potential for targeted interventions.