Role of the integrin alphaVbeta3 in mediating increased smooth muscle cell responsiveness to IGF-I in response to hyperglycemic stress

Is Diabetes Mellitus a Predisposing Factor for Helicobacter pylori Infections?

PURPOSE OF REVIEW

This review aims to analyse the consistency of reports suggesting the role of Diabetes Mellitus in the pathogenesis of Helicobacter pylori (H. pylori).

RECENT FINDINGS

There have been numerous controversies citing the prevalence of H. pylori infections in patients suffering from type 2 diabetes mellitus (T2DM). This review investigates the possible crosstalk between H. pylori infections and T2DM and also designs a meta-analysis to quantify the association. Subgroup analyses have also been conducted to deduce factors like geography and testing techniques, in playing a role in stratification analysis. Based on a scientific literature survey and meta-analysis of databases from 1996 to 2022, a trend towards more frequent H. pylori infections in patients with diabetes mellitus was observed. The highly diversified nature of H. pylori infections across age, gender, and geographical regions requires large interventional studies to evaluate its long-term association with diabetes mellitus. Further possible linkage of the prevalence of diabetes mellitus concomitant with that of H. pylori infected patients has also been delineated in the review.

Cancer and diabetes: the interlinking metabolic pathways and repurposing actions of antidiabetic drugs

Cancers are regarded as one of the main causes of death and result in high health burden worldwide. The management of cancer include chemotherapy, surgery and radiotherapy. The chemotherapy, which involves the use of chemical agents with cytotoxic actions is utilised as a single treatment or combined treatment. However, these managements of cancer such as chemotherapy poses some setbacks such as cytotoxicity on normal cells and the problem of anticancer drug resistance. Therefore, the use of other therapeutic agents such as antidiabetic drugs is one of the alternative interventions used in addressing some of the limitations in the use of anticancer agents. Antidiabetic drugs such as sulfonylureas, biguanides and thiazolidinediones showed beneficial and repurposing actions in the management of cancer, thus, the activities of these drugs against cancer is attributed to some of the metabolic links between the two disorders and these includes hyperglycaemia, hyperinsulinemia, inflammation, and oxidative stress as well as obesity. Furthermore, some studies showed that the use of antidiabetic drugs could serve as risk factors for the development of cancerous cells particularly pancreatic cancer. However, the beneficial role of these chemical agents overweighs their detrimental actions in cancer management. Hence, the present review indicates the metabolic links between cancer and diabetes and the mechanistic actions of antidiabetic drugs in the management of cancers.

Adipose-PAS interactions in the context of its localised bio-engineering potential (Review)

Adipocytes are a known source of stem cells. They are easy to harvest, and are a suitable candidate for autogenous grafts. Adipose derived stem cells (ADSCs) have multiple target tissues which they can differentiate into, including bone and cartilage. In adipose tissue, ADSCs are able to differentiate, as well as providing energy and a supply of cytokines/hormones to manage the hypoxic and lipid/hormone saturated adipose environment. The plasminogen activation system (PAS) controls the majority of proteolytic activities in both adipose and wound healing environments, allowing for rapid cellular migration and tissue remodelling. While the primary activation pathway for PAS occurs through the urokinase plasminogen activator (uPA), which is highly expressed by endothelial cells, its function is not limited to enabling revascularisation. Proteolytic activity is dependent on protease activation, localisation, recycling mechanisms and substrate availability. uPA and uPA activated plasminogen allows pluripotent cells to arrive to new local environments and fulfil the niche demands. However, overstimulation, the acquisition of a migratory phenotype and constant protein turnover can be unconducive to the formation of structured hard and soft tissues. To maintain a suitable healing pattern, the proteolytic activity stimulated by uPA is modulated by plasminogen activator inhibitor 1. Depending on the physiological settings, different parts of the remodelling mechanism are activated with varying results. Utilising the differences within each microenvironment to recreate a desired niche is a valid therapeutic bio-engineering approach. By controlling the rate of protein turnover combined with a receptive stem cell lineage, such as ADSC, a novel avenue on the therapeutic opportunities may be identified, which can overcome limitations, such as scarcity of stem cells, low angiogenic potential or poor host tissue adaptation.

Insulin-like growth factors: Ligands, binding proteins, and receptors

BACKGROUND

The insulin-like growth factor family of ligands (IGF-I, IGF-II, and insulin), receptors (IGF-IR, M6P/IGF-IIR, and insulin receptor [IR]), and IGF-binding proteins (IGFBP-1-6) play critical roles in normal human physiology and disease states.

SCOPE OF REVIEW

Insulin and insulin receptors are the focus of other chapters in this series and will therefore not be discussed further. Here we review the basic components of the IGF system, their role in normal physiology and in critical pathology's. While this review concentrates on the role of IGFs in human physiology, animal models have been essential in providing understanding of the IGF system, and its regulation, and are briefly described.

MAJOR CONCLUSIONS

IGF-I has effects via the circulation and locally within tissues to regulate cellular growth, differentiation, and survival, thereby controlling overall body growth. IGF-II levels are highest prenatally when it has important effects on growth. In adults, IGF-II plays important tissue-specific roles, including the maintenance of stem cell populations. Although the IGF-IR is closely related to the IR it has distinct physiological roles both on the cell surface and in the nucleus. The M6P/IGF-IIR, in contrast, is distinct and acts as a scavenger by mediating internalization and degradation of IGF-II. The IGFBPs bind IGF-I and IGF-II in the circulation to prolong their half-lives and modulate tissue access, thereby controlling IGF function. IGFBPs also have IGF ligand-independent cell effects.

Inhibition by Thyroid Hormones of Cell Migration Activated by IGF-1 and MCP-1 in THP-1 Monocytes: Focus on Signal Transduction Events Proximal to Integrin αvβ3

Interaction between thyroid hormones and the immune system is reported in the literature. Thyroid hormones, thyroxine, T₄, but also T₃, act non-genomically through mechanisms that involve a plasma membrane receptor αvβ3 integrin, a co-receptor for insulin-like growth factor-1 (IGF-1). Previous data from our laboratory show a crosstalk between thyroid hormones and IGF-1 because thyroid hormones inhibit the IGF-1-stimulated glucose uptake and cell proliferation in L-6 myoblasts, and the effects are mediated by integrin αvβ3. IGF-1 also behaves as a chemokine, being an important factor for tissue regeneration after damage. In the present study, using THP-1 human leukemic monocytes, expressing αvβ3 integrin in their cell membrane, we focused on the crosstalk between thyroid hormones and either IGF-1 or monocyte chemoattractant protein-1 (MCP-1), studying cell migration and proliferation stimulated by the two chemokines, and the role of αvβ3 integrin, using inhibitors of αvβ3 integrin and downstream pathways. Our results show that IGF-1 is a potent chemoattractant in THP-1 monocytes, stimulating cell migration, and thyroid hormone inhibits the effect through αvβ3 integrin. Thyroid hormone also inhibits IGF-1-stimulated cell proliferation through αvβ3 integrin, an example of a crosstalk between genomic and non-genomic effects. We also studied the effects of thyroid hormone on cell migration and proliferation induced by MCP-1, together with the pathways involved, by a pharmacological approach and docking simulation. Our findings show a different downstream signaling for IGF-1 and MCP-1 in THP-1 monocytes mediated by the plasma membrane receptor of thyroid hormones, integrin αvβ3.

Effect of αvβ3 Integrin Expression and Activity on Intraocular Pressure

Purpose

To determine the effects of αvβ3 integrin expression and activation on intraocular pressure (IOP).

Methods

Cre^+/−β3^flox/flox mice were treated with topical tamoxifen eye drops for 5 days to activate Cre and excise the β3 integrin gene from the anterior segment. IOP was measured weekly for 11 weeks using rebound tonometry. Mice were then killed and changes in expression of the β3 integrin subunit in Cre^+/− β3^flox/flox mice were determined using Western blotting analysis and immunofluorescence microscopy. To determine the effect of αvβ3 integrin activation on outflow facility, porcine organ culture anterior segments (POCAS) were perfused with the αvβ3 integrin-activating antibody AP5 or an isotype IgG control for 21 hours. The effect of αvβ3 integrin activation on IOP was measured over 7 days in C57BL/6J mice intracamerally infused with AP5, AP3, IgG, or PBS.

Results

Deletion of the β3 integrin subunit using the tamoxifen-inducible Cre-loxP system resulted in a decrease in expression of the β3 integrin subunit in the trabecular meshwork and ciliary muscle. Morphologically no gross changes in the anterior segment were detected. Deletion of the β3 integrin subunit resulted in a significantly (P < 0.05) lower IOP in mice within 2 weeks following the tamoxifen treatment and persisted for 11 weeks. Activating the αvβ3 integrin with the AP5 antibody resulted in a significant (P < 0.05) increase in IOP in C57BL/6J mice and a decrease in outflow facility in 42% of the POCAS.

Conclusions

These studies demonstrate a role for αvβ3 integrin signaling in the regulation of IOP.

HbA1c showed a positive association with carcinoembryonic antigen (CEA) level in only diabetes, not prediabetic or normal individuals

Background

This study was conducted to investigate the association of carcinoembryonic antigen (CEA) and glycated hemoglobin (HbA1c) in normal, prediabetic, and diabetic subjects.

Methods

A total of 2,911 participants who underwent general health checkups were enrolled and categorized into the normal, prediabetes, and diabetes groups. Demographic, anthropological, and clinical variables were investigated, and correlations with CEA were analyzed. For 28 diabetic subjects with CEA levels above the upper limit, the follow‐up CEA and HbA1c data were analyzed.

Results

Carcinoembryonic antigen levels were significantly different among the normal, prediabetes, and diabetes groups (1.7 ± 1.1 vs 2.0 ± 1.1 vs 2.5 ± 1.5; P < 0.001), and men had higher CEA levels than women in all three groups. Correlation analysis identified a significant positive correlation between serum CEA and HbA1c in the diabetes group using unadjusted and adjusted models (r = 0.189, P < 0.001 and r = 0.218, P < 0.001), and multiple linear regression analysis also revealed that HbA1c was independently and positively correlated with CEA in the diabetes group (β = 0.275, P < 0.001). However, these relationships were inconsistent in the normal and prediabetes groups. The changes in CEA and HbA1c from baseline to follow‐up (delta CEA and delta HbA1c) showed a significant positive correlation (P = 0.021).

Conclusions

In diabetes, the CEA level was independently and positively correlated with glycemic control status. Additionally, the change in CEA level (delta CEA) showed a positive correlation with the change in HbA1c level (delta HbA1c) in the follow‐up data analysis.

IGF-1 and cardiovascular disease

Atherosclerosis is an inflammatory arterial pathogenic condition, which leads to ischemic cardiovascular diseases, such as coronary artery disease and myocardial infarction, stroke, and peripheral arterial disease. Atherosclerosis is a multifactorial disorder and its pathophysiology is highly complex. Changes in expression of multiple genes coupled with environmental and lifestyle factors initiate cascades of adverse events involving multiple types of cells (e.g. vascular endothelial cells, smooth muscle cells, and macrophages). IGF-1 is a pleiotropic factor, which is found in the circulation (endocrine IGF-1) and is also produced locally in arteries (endothelial cells and smooth muscle cells). IGF-1 exerts a variety of effects on these cell types in the context of the pathogenesis of atherosclerosis. In fact, there is an increasing body of evidence suggesting that IGF-1 has beneficial effects on the biology of atherosclerosis. This review will discuss recent findings relating to clinical investigations on the relation between IGF-1 and cardiovascular disease and basic research using animal models of atherosclerosis that have elucidated some of the mechanisms underlying atheroprotective effects of IGF-1.

A longitudinal study of serum insulin-like growth factor-I levels over 6 years in a large cohort of children and adolescents with type 1 diabetes mellitus: A marker reflecting diabetic retinopathy

OBJECTIVE

To evaluate longitudinal serum insulin-like growth factor-I (IGF-I) in a large cohort of children and adolescents with type 1 diabetes in relation to hemoglobin A1c (HbA1c), age, diabetes duration, and body mass index (BMI), its association to height and retinopathy, and in comparison with healthy subject references.

METHODS

A total of 2683 serum IGF-I values were obtained from 806 children and adolescents with T1DM, from annual blood samples for up to 6 consecutive years.

RESULTS

In a multiple regression analysis IGF-I values were negatively correlated to HbA1c and diabetes duration, and positively correlated to BMI (P < .001, P < .001, and P < .001, respectively, adjusted r²  = 0.102). Children and adolescents with T1DM had lower mean IGF-I levels and reference interval limits compared to healthy subjects. In boys, mean (SD) IGF-I SD score (SDS) levels were -1.04 (±1.3) calculated from the healthy reference. IGF-I peaked at 15 years of age, similarly to healthy controls, but with markedly lower levels in late puberty. Girls were more affected at later stages of puberty but with a slightly less depressed overall mean IGF-I SDS of -0.69 (±1.2). In a subgroup of 746 subjects with fundus photography, a negative correlation was seen between individual mean IGF-I SDS and preproliferative retinopathy (P = .004, adjusted r²  = 0.021). In another subgroup of 84 adolescents, no correlation was seen between individual mean IGF-I SDS and target height SDS or distance to target height SDS.

CONCLUSION

Poor metabolic control and diabetes duration impact negatively on serum IGF-I levels. A low individual mean IGF-I level was associated with progression of retinopathy independently of HbA1c, age, gender, and diabetes duration. Disease, sex and age related IGF-I SDS may become clinical helpful as a supplement to HbA1c in predicting the long-term outcome for children and adolescents with T1DM.

Targeting Insulin-Like Growth Factor-I and Extracellular Matrix Interactions in Melanoma Progression

Insulin-like growth factor (IGF)-I binds to the ECM protein vitronectin (VN) through IGF binding proteins (IGFBPs) to enhance proliferation and migration of skin keratinocytes and fibroblasts. Although evidence exists for the role of individual components of the complex (IGF-I, IGFBP-3 and VN), the cellular functions stimulated by these proteins together as a complex remains un-investigated in melanoma cells. We report here that the IGF-I:IGFBP-3:VN trimeric complex stimulates a dose-dependent increase in the proliferation and migration of WM35 and Sk-MEL28 melanoma cells. In 3D Matrigel^™ and hydrogel cultures, both cell lines formed primary tumor-like spheroids, which increased in size in a dose-dependent manner in response to the trimeric complex. Furthermore, we reveal IGFBP-3:VN protein complexes in malignant melanoma and squamous cell carcinoma patient tissues, where the IGFBP-3:VN complex was seen to be predominantly tumor cell-associated. Peptide antagonists designed to target the binding of IGF-I:IGFBP-3 to VN were demonstrated to inhibit IGF-I:IGFBP-3:VN-stimulated cell migration, invasion and 3D tumor cell growth of melanoma cells. Overall, this study provides new data on IGF:ECM interactions in skin malignancies and demonstrates the potential usefulness of a growth factor:ECM-disrupting strategy for abrogating tumor progression.

New insight for metformin against bladder cancer

International Agency for Research on Cancer (IARC) estimated that bladder cancer is the ninth most common cancer in the world, with 430,000 new cases and 165,000 deaths in 2012. Bladder cancer represents the fourth most common cancer in men and ninth most common cancer in women. It is the second most prevalent cancer in men 60 years of age or older in United States. Looking further down, continuing advancements in cancer research could potentially offer more choices for clinician and patient with longer survival and better quality of life. Although, bladder cancer represents an ideal tumor model to test and apply cancer prevention strategies; there are limited studies about application of metformin in the management of bladder cancer. Here, I will shed light on the proposed mechanisms of anti-carcinogenic effects of metformin and cohort of these mechanisms with the novel application of metformin as therapy of bladder cancer.

Metformin targets multiple signaling pathways in cancer

Metformin, an inexpensive and well-tolerated oral agent commonly used in the first-line treatment of type 2 diabetes, has become the focus of intense research as a candidate anticancer agent. Here, we discuss the potential of metformin in cancer therapeutics, particularly its functions in multiple signaling pathways, including AMP-activated protein kinase, mammalian target of rapamycin, insulin-like growth factor, c-Jun N-terminal kinase/mitogen-activated protein kinase (p38 MAPK), human epidermal growth factor receptor-2, and nuclear factor kappaB pathways. In addition, cutting-edge targeting of cancer stem cells by metformin is summarized.

A review for clinicians: Prostate cancer and the antineoplastic properties of metformin

OBJECTIVES

Metformin has numerous antineoplastic effects including an AMP-activated protein kinase-dependent mechanism, AMP-activated protein kinase-independent mechanisms, alteration of insulin and insulin-like growth factor signaling pathways, and suppression of androgen signaling pathways that trigger prostate cancer growth and proliferation. In contrast to other malignancies that are associated with increased incidence among patients with obesity and type II diabetes mellitus (T2DM), epidemiological studies suggest that obesity and T2DM may impart a protective effect on prostate cancer incidence by creating a set of metabolic conditions that lower androgen levels.

METHODS AND MATERIALS

The PubMed and Web of Science databases were searched using the terms "prostate cancer," "metformin," "antineoplastic," "antitumorigenic," and "diabetes" up to the first week of August 2016. Articles regarding metformin's antineoplastic properties on prostate cancer were reviewed.

RESULTS

Treating T2DM with metformin may reverse the metabolic conditions that suppress androgen levels, thereby enabling higher levels of androgens to stimulate prostate growth, proliferation, and tumorigenesis. Thus, the antineoplastic properties of metformin may not be appreciable in the early stages of prostate cancer development because metformin corrects for the metabolic conditions of T2DM that impart a protective effect on prostate cancer. These findings, although inconclusive, do not support the use of metformin as a preventive agent for prostate cancer. However, the future appears bright for metformin as either a monotherapy or an adjunct to androgen deprivation therapy, external-beam radiation therapy, prostatectomy, or chemotherapy. Support for this includes meta-analyses that suggest a mortality benefit to patients with prostate cancer on metformin, a clinical trial that demonstrates metformin leads to significant improvement in metabolic syndrome parameters for patients with prostate cancer on androgen deprivation therapy, and a clinical trial that shows metformin has modest activity in the treatment of some patients with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer.

CONCLUSIONS

This review summarizes the literature regarding the antineoplastic mechanisms, clinical implications, and future trajectory of clinical research for metformin in prostate cancer.

Type 2 Diabetes Mellitus and Its Association with the Risk of Pancreatic Carcinogenesis: A Review

The prevalence of diabetes mellitus (DM) and associated diseases such as cancers are substantially increasing worldwide. About 80% of the patients with pancreatic cancer have glucose metabolism alterations. This suggests an association between type 2 DM and pancreatic cancer risk and progression. There are hypotheses that show metabolic links between the diseases, due to insulin resistance, hyperglycemia, hyperinsulinemia, low grade chronic inflammation, and alteration in the insulin-insulin-like growth factor axis. The use of diabetes medications can influence the extent of carcinogenesis of the pancreas. This study briefly reviews recent literature on investigation of metabolic link of type 2 DM, risk of carcinogenesis of the pancreas and their association, as well as the current understanding of metabolic pathways implicated in metabolism and cellular growth. The main finding of this review, although there are discrepancies, is that according to most research long-term DM does not raise the risk of pancreatic cancer. The longest duration of DM may reflect hypoinsulinemia due to treatment for hyperglycemia, but recent onset diabetes was associated with increased risk for pancreatic cancer due to hyperinsulinemia and hyperglycemia. In conclusion, the review demonstrates that type 2 DM and the duration of diabetes pose a risk for pancreatic carcinogenesis, and that there is biological link between the diseases.

Integrin αvβ3 mediates the synergetic regulation of core-binding factor α1 transcriptional activity by gravity and insulin-like growth factor-1 through phosphoinositide 3-kinase signaling

Mechanical stimulation and biological factors coordinately regulate bone development and regeneration; however, the underlying mechanisms are poorly understood. Microgravity induces bone loss, which may be partly related to the development of resistance to local cytokines, including insulin-like growth factor 1 (IGF-1). Here, we report the involvement of integrin αvβ3 in microgravity-associated bone loss. An established OSE-3T3 cell model was stably transfected with a 6OSE2 (Osteoblast-Specific Element 2)-luciferase reporter and cultured under simulated microgravity (SMG) and hypergravity (HG) conditions in the presence or absence of IGF-1, the disintegrin echistatin, the phosphoinositide 3-kinase (PI3K) inhibitor LY294002, or combinations of these agents. Activity of core-binding factor α1 (Cbfa1), an essential transcription factor for osteoblastic differentiation and osteogenesis, was reflected by luciferase activity. Different gravity conditions affected the induction of IGF-1 and subsequent effects on Cbfa1 transcription activity. SMG and HG influenced the expression and activity of integrin αvβ3 and phosphorylation level of p85. LY294002 inhibited the effects of HG or IGF-1 on Cbfa1 activity, indicating that HG and IGF-1 could increase Cbfa1 activity via PI3K signaling. Inhibition of integrin αvβ3 by echistatin attenuated the induction of IGF-1 and thus its effect on Cbfa1 activity under normal and HG conditions. Co-immunoprecipitation demonstrated that integrin β3 interacted with insulin receptor substrate 1, and that this interaction was decreased under SMG and increased under HG conditions. These results suggest that integrin αvβ3 mediates the synergetic regulation of Cbfa1 transcription activity by gravity and IGF-1 via PI3K signaling.

IGFBP-3: a cell fate pivot in cancer and disease

One of the hallmarks in the advancement of cancer cells is an ability to overcome and acquire resistance to adverse conditions. There has been a large amount of cancer research on IGFBP-3 as a pro-apoptotic molecule in vitro. These pro-apoptotic properties, however, do not correlate with several studies linking high IGFBP-3 levels in breast cancer tissue to rapid growth and poor prognosis. Evidence is emerging that IGFBP-3 also exhibits pro-survival and growth-promoting properties in vitro. How IGFBP-3 pivots cell fate to either death or survival, it seems, comes down to a complex interplay between cells' microenvironments and the presence of cellular IGFBP-3 binding partners and growth factor receptors. The cytoprotective actions of IGFBP-3 are not restricted to cancer but are also observed in other disease states, such as retinopathy and brain ischaemia. Here we review the literature on this paradoxical nature of IGFBP-3, its pro-apoptotic and growth-inhibitory actions versus its cytoprotective and growth-potentiating properties, and discuss the implications of targeting IGFBP-3 for treatment of disease.

High glucose alters retinal astrocytes phenotype through increased production of inflammatory cytokines and oxidative stress

Astrocytes are macroglial cells that have a crucial role in development of the retinal vasculature and maintenance of the blood-retina-barrier (BRB). Diabetes affects the physiology and function of retinal vascular cells including astrocytes (AC) leading to breakdown of BRB. However, the detailed cellular mechanisms leading to retinal AC dysfunction under high glucose conditions remain unclear. Here we show that high glucose conditions did not induce the apoptosis of retinal AC, but instead increased their rate of DNA synthesis and adhesion to extracellular matrix proteins. These alterations were associated with changes in intracellular signaling pathways involved in cell survival, migration and proliferation. High glucose conditions also affected the expression of inflammatory cytokines in retinal AC, activated NF-κB, and prevented their network formation on Matrigel. In addition, we showed that the attenuation of retinal AC migration under high glucose conditions, and capillary morphogenesis of retinal endothelial cells on Matrigel, was mediated through increased oxidative stress. Antioxidant proteins including heme oxygenase-1 and peroxiredoxin-2 levels were also increased in retinal AC under high glucose conditions through nuclear localization of transcription factor nuclear factor-erythroid 2-related factor-2. Together our results demonstrated that high glucose conditions alter the function of retinal AC by increased production of inflammatory cytokines and oxidative stress with significant impact on their proliferation, adhesion, and migration.

Dexamethasone increases αvβ3 integrin expression and affinity through a calcineurin/NFAT pathway

The purpose of this study was to determine how dexamethasone (DEX) regulates the expression and activity of αvβ3 integrin. FACS analysis showed that DEX treatment induced expression of an activated αvβ3 integrin. Its expression remained high as long as DEX was present and continued following DEX removal. FACS analysis showed that the upregulation of αvβ3 integrin was the result of an increase in the expression of the β3 integrin subunit. By real time qPCR, DEX treatment induced a 6.2-fold increase (p<0.04) in β3 integrin mRNA by day 2 compared to control and remained elevated for 6days of treatment and then an additional 10days once the DEX was removed. The increase in β3 integrin mRNA levels required only 1day of DEX treatment to increase levels for 4days in the absence of DEX. In contrast, DEX did not alter β1 integrin mRNA or protein levels. The DEX-induced upregulation of β3 integrin mRNA was partly due to an increase in its half-life to 60.7h from 22.5h in control cultures (p<0.05) and could be inhibited by RU486 and cycloheximide, suggesting that DEX-induced de novo protein synthesis of an activation factor was needed. The calcineurin inhibitors cyclosporin A (CsA) and FK506 inhibited the DEX induced increase in β3 integrin mRNA. In summary, the DEX-induced increase in β3 integrin is a secondary glucocorticoid response that results in prolonged expression of αvβ3 integrin and the upregulation of the β3 integrin subunit through the calcineurin/NFAT pathway.

An integrin binding-defective mutant of insulin-like growth factor-1 (R36E/R37E IGF1) acts as a dominant-negative antagonist of the IGF1 receptor (IGF1R) and suppresses tumorigenesis but still binds to IGF1R

Insulin-like growth factor-1 (IGF1) is a major therapeutic target for cancer. We recently reported that IGF1 directly binds to integrins (αvβ3 and α6β4) and induces ternary complex formation (integrin-IGF1-IGF1 receptor (IGF1R)) and that the integrin binding-defective mutant of IGF1 (R36E/R37E) is defective in signaling and ternary complex formation. These findings predict that R36E/R37E competes with WT IGF1 for binding to IGF1R and inhibits IGF signaling. Here, we described that excess R36E/R37E suppressed cell viability increased by WT IGF1 in vitro in non-transformed cells. We studied the effect of R36E/R37E on viability and tumorigenesis in cancer cell lines. We did not detect an effect of WT IGF1 or R36E/R37E in cancer cells under anchorage-dependent conditions. However, under anchorage-independent conditions, WT IGF1 enhanced cell viability and induced signals, whereas R36E/R37E did not. Notably, excess R36E/R37E suppressed cell viability and signaling induced by WT IGF1 under anchorage-independent conditions. Using cancer cells stably expressing WT IGF1 or R36E/R37E, we determined that R36E/R37E suppressed tumorigenesis in vivo, whereas WT IGF1 markedly enhanced it. R36E/R37E suppressed the binding of WT IGF1 to the cell surface and the subsequent ternary complex formation induced by WT IGF1. R36E/R37E suppressed activation of IGF1R by insulin. WT IGF1, but not R36E/R37E, induced ternary complex formation with the IGF1R/insulin receptor hybrid. These findings suggest that 1) IGF1 induces signals under anchorage-independent conditions and that 2) R36E/R37E acts as a dominant-negative inhibitor of IGF1R (IGF1 decoy). Our results are consistent with a model in which ternary complex formation is critical for IGF signaling.

Increased risk of gastrointestinal malignancy in patients with diabetes mellitus and correlations with anti-diabetes drugs: a nationwide population-based study in Taiwan

OBJECTIVE

Although the major cause of morbidity and mortality in patients with diabetes mellitus (DM) is cardiovascular disease, DM is also associated with certain site-specific cancers. However, whether DM is associated with an increased risk of cancer of the digestive tract remains undetermined. A nationwide, population-based database in Taiwan was analyzed to explore the relationship between DM and cancer of the digestive organs.

METHODS

From 2000 to 2007, a study cohort consisting of 39,515 patients with newly diagnosed diabetes without a previous diagnosis of gastrointestinal (GI) cancer was identified from the National Health Insurance Research Database in Taiwan. A control cohort of 79,030 age- and sex-matched non-diabetic subjects was selected to compare the occurrence of GI malignancies between the two groups. The association between the incidence of GI cancers and the use of glucose-lowering therapies was also investigated.

RESULTS

During the 7-year follow-up period, GI cancers developed in 929 diabetic patients (2.35%) and 1,126 subjects (1.42%) in the comparison cohort. DM was associated with a 2.75-fold (95% confidence interval (CI), 2.51-3.02) higher risk of developing GI malignancy. Among GI cancers, the incidences of stomach (adjusted hazard ratio (HR), 1.49; 95% CI, 1.16-1.92), liver (adjusted HR, 2.65; 95% CI, 2.29-3.07), colon (adjusted HR, 1.58; 95% CI, 1.28-1.94) and pancreatic cancers (adjusted HR, 4.35; 95% CI, 2.93-6.47) were significantly increased in the patients with DM. An analysis of the effects of various glucose-lowering therapies in the diabetic patients revealed the use of α-glucosidase inhibitors to be associated with a lower risk of hepatic cancer (adjusted HR, 0.62; 95% CI, 0.4-0.94). Thiazolidinedione (TZD) treatment was associated with lower stomach (adjusted HR, 0.11; 95% CI, 0.02-0.82) and hepatic cancer risks (adjusted HR, 0.46; 95% CI, 0.29-0.73), while sulfonylurea use was associated with a lower colon cancer risk (adjusted HR, 0.74; 95% CI, 0.51-1.09) and a higher pancreatic cancer risk (adjusted HR, 2.36; 95% CI, 1.21-4.61).

CONCLUSION

Patients with DM have an increased risk of GI malignancy that may be affected by the use of different categories of glucose-lowering therapies.

Insulin-like growth factor (IGF) signaling requires αvβ3-IGF1-IGF type 1 receptor (IGF1R) ternary complex formation in anchorage independence, and the complex formation does not require IGF1R and Src activation

Integrin αvβ3 plays a role in insulin-like growth factor 1 (IGF1) signaling (integrin-IGF1 receptor (IGF1R) cross-talk) in non-transformed cells in anchorage-dependent conditions. We reported previously that IGF1 directly binds to αvβ3 and induces αvβ3-IGF1-IGF1R ternary complex formation in these conditions. The integrin-binding defective IGF1 mutant (R36E/R37E) is defective in inducing ternary complex formation and IGF signaling, whereas it still binds to IGF1R. We studied if IGF1 can induce signaling in anchorage-independent conditions in transformed Chinese hamster ovary cells that express αvβ3 (β3-CHO) cells. Here we describe that IGF1 signals were more clearly detectable in anchorage-independent conditions (polyHEMA-coated plates) than in anchorage-dependent conditions. This suggests that IGF signaling is masked by signals from cell-matrix interaction in anchorage-dependent conditions. IGF signaling required αvβ3 expression, and R36E/R37E was defective in inducing signals in polyHEMA-coated plates. These results suggest that αvβ3-IGF1 interaction, not αvβ3-extracellular matrix interaction, is essential for IGF signaling. Inhibitors of IGF1R, Src, AKT, and ERK1/2 did not suppress αvβ3-IGF-IGF1R ternary complex formation, suggesting that activation of these kinases are not required for ternary complex formation. Also, mutations of the β3 cytoplasmic tail (Y747F and Y759F) that block β3 tyrosine phosphorylation did not affect IGF1R phosphorylation or AKT activation. We propose a model in which IGF1 binding to IGF1R induces recruitment of integrin αvβ3 to the IGF-IGF1R complex and then β3 and IGF1R are phosphorylated. It is likely that αvβ3 should be together with the IGF1-IGF1R complex for triggering IGF signaling.

Periostin promotes chronic allergic inflammation in response to Th2 cytokines

Allergic inflammation triggered by exposure of an allergen frequently leads to the onset of chronic inflammatory diseases such as atopic dermatitis (AD) and bronchial asthma. The mechanisms underlying chronicity in allergic inflammation remain unresolved. Periostin, a recently characterized matricellular protein, interacts with several cell surface integrin molecules, providing signals for tissue development and remodeling. Here we show that periostin is a critical mediator for the amplification and persistence of allergic inflammation using a mouse model of skin inflammation. Th2 cytokines IL-4 and IL-13 stimulated fibroblasts to produce periostin, which interacted with αv integrin, a functional periostin receptor on keratinocytes, inducing production of proinflammatory cytokines, which consequently accelerated Th2-type immune responses. Accordingly, inhibition of periostin or αv integrin prevented the development or progression of allergen-induced skin inflammation. Thus, periostin sets up a vicious circle that links Th2-type immune responses to keratinocyte activation and plays a critical role in the amplification and chronicity of allergic skin inflammation.

Effect of vitronectin bound to insulin-like growth factor-I and insulin-like growth factor binding protein-3 on porcine enamel organ-derived epithelial cells

The aim of this paper was to determine whether the interaction between IGF, IGFBP, and VN modulates the functions of porcine EOE cells. Enamel organs from 6-month-old porcine third molars were dissociated into single epithelial cells and subcultured on culture dishes pretreated with VN, IGF-I, and IGFBP-3 (IGF-IGFBP-VN complex). The subcultured EOE cells retained their capacity for ameloblast-related gene expression, as shown by semiquantitative reverse transcription-polymerase chain reaction. Amelogenin expression was detected in the subcultured EOE cells by immunostaining. The subcultured EOE cells were then seeded onto collagen sponge scaffolds in combination with fresh dental mesenchymal cells and transplanted into athymic rats. After 4 weeks, enamel-dentin-like complex structures were present in the implanted constructs. These results show that EOE cells cultured on IGF-IGFBP-VN complex differentiated into ameloblasts-like cells that were able to secrete amelogenin proteins and form enamel-like tissues in vivo. Functional assays demonstrated that the IGF/IGFBP/VN complex significantly enhanced porcine EOE cell proliferation and tissue forming capacity for enamel. This is the first study to demonstrate a functional role of the IGF-IGFBP-VN complex in EOE cells. This application of the subculturing technique provides a foundation for further tooth-tissue engineering and for improving our understanding of ameloblast biology.

Molecular basis of signaling specificity of insulin and IGF receptors: neglected corners and recent advances

Insulin and insulin-like growth factor (IGF) receptors utilize common phosphoinositide 3-kinase/Akt and Ras/extracellular signal-regulated kinase signaling pathways to mediate a broad spectrum of "metabolic" and "mitogenic" responses. Specificity of insulin and IGF action in vivo must in part reflect expression of receptors and responsive pathways in different tissues but it is widely assumed that it is also determined by the ligand binding and signaling mechanisms of the receptors. This review focuses on receptor-proximal events in insulin/IGF signaling and examines their contribution to specificity of downstream responses. Insulin and IGF receptors may differ subtly in the efficiency with which they recruit their major substrates (IRS-1 and IRS-2 and Shc) and this could influence effectiveness of signaling to "metabolic" and "mitogenic" responses. Other substrates (Grb2-associated binder, downstream of kinases, SH2Bs, Crk), scaffolds (RACK1, β-arrestins, cytohesins), and pathways (non-receptor tyrosine kinases, phosphoinositide kinases, reactive oxygen species) have been less widely studied. Some of these components appear to be specifically involved in "metabolic" or "mitogenic" signaling but it has not been shown that this reflects receptor-preferential interaction. Very few receptor-specific interactions have been characterized, and their roles in signaling are unclear. Signaling specificity might also be imparted by differences in intracellular trafficking or feedback regulation of receptors, but few studies have directly addressed this possibility. Although published data are not wholly conclusive, no evidence has yet emerged for signaling mechanisms that are specifically engaged by insulin receptors but not IGF receptors or vice versa, and there is only limited evidence for differential activation of signaling mechanisms that are common to both receptors. Cellular context, rather than intrinsic receptor activity, therefore appears to be the major determinant of whether responses to insulin and IGFs are perceived as "metabolic" or "mitogenic."

The role of pre-existing diabetes mellitus on hepatocellular carcinoma occurrence and prognosis: a meta-analysis of prospective cohort studies

Background

The impact of pre-existing diabetes mellitus (DM) on hepatocellular carcinoma (HCC) occurrence and prognosis is complex and unclear. The aim of this meta-analysis is to evaluate the association between pre-existing diabetes mellitus and hepatocellular carcinoma occurrence and prognosis.

Methods

We searched PubMed, Embase and the Cochrane Library from their inception to January, 2011 for prospective epidemiological studies assessing the effect of pre-existing diabetes mellitus on hepatocellular carcinoma occurrence, mortality outcomes, cancer recurrence, and treatment-related complications. Study-specific risk estimates were combined by using fixed effect or random effect models.

Results

The database search generated a total of 28 prospective studies that met the inclusion criteria. Among these studies, 14 reported the risk of HCC incidence and 6 studies reported risk of HCC specific mortality. Six studies provided a total of 8 results for all-cause mortality in HCC patients. Four studies documented HCC recurrence risks and 2 studies reported risks for hepatic decomposition occurrence in HCC patients. Meta-analysis indicated that pre-existing diabetes mellitus (DM) was significantly associated with increased risk of HCC incidence [meta-relative risk (RR) = 1.87, 95% confidence interval (CI): 1.15–2.27] and HCC-specific mortality (meta-RR = 1.88, 95%CI: 1.39–2.55) compared with their non-DM counterparts. HCC patients with pre-existing DM had a 38% increased (95% CI: 1.13–1.48) risk of death from all-causes and 91% increased (95%CI: 1.41–2.57) risk of hepatic decomposition occurrence compared to those without DM. In DM patients, the meta-RR for HCC recurrence-free survival was 1.93(95%CI: 1.12–3.33) compared with non-diabetic patients.

Conclusion

The findings from the current meta-analysis suggest that DM may be both associated with elevated risks of both HCC incidence and mortality. Furthermore, HCC patients with pre-existing diabetes have a poorer prognosis relative to their non-diabetic counterparts.

Syndecan-1 couples the insulin-like growth factor-1 receptor to inside-out integrin activation

Syndecan-1 (Sdc1) engages and activates the αvβ3 (and/or αvβ5) integrin when clustered in human carcinoma and endothelial cells. Although the engagement is extracellular, the activation mechanism is cytoplasmic. This talin-dependent, inside-out signaling pathway is activated downstream of the insulin-like growth factor-1 receptor (IGF1R), whose kinase activity is triggered by Sdc1 clustering. In vitro binding assays using purified receptors suggest that association of the Sdc1 ectodomain with the integrin provides a 'docking face' for IGF1R. IGF1R docking and activation of the associated integrin is blocked by synstatin (SSTN(92-119)), a peptide derived from the integrin engagement site in Sdc1. IGF1R colocalizes with αvβ3 integrin and Sdc1 in focal contacts, but fails to associate with or activate the integrin in cells either lacking Sdc1 or expressing Sdc1(Δ67-121), a mutant that is unable to form the Sdc1-integrin-IGF1R ternary complex. Integrin activation is also blocked by IGF1R inhibitors or by silencing IGF1R or talin expression with small-interfering RNAs (siRNAs). In both cases, expression of the constitutively active talin F23 head domain rescues integrin activation. We recently reported that SSTN(92-119) blocks angiogenesis and impairs tumor growth in mice, therefore this Sdc1-mediated integrin regulatory mechanism might be a crucial regulator of disease processes known to rely on these integrins, including tumor cell metastasis and tumor-induced angiogenesis.

The role of β3-integrins in tumor angiogenesis: context is everything

Integrins are a family of cell-extracellular matrix adhesion molecules that play important roles in tumor angiogenesis. αvβ3-Integrin has received much attention as a potential anti-angiogenic target because it is upregulated in tumor-associated blood vessels. Agents targeting αvβ3-integrin are now showing some success in phase III clinical trails for the treatment of glioblastoma, but the exact function of this integrin in tumor angiogenesis is still relatively unknown. This review highlights some of the recent data illustrating that β3-integrins play both pro-angiogenic and anti-angiogenic roles in tumor angiogenesis depending on the context. Specifically we will discuss how the following differentially influence β3-integrin's role in tumor angiogenesis: first, cell-matrix interactions, second, β3-integrin inhibitor doses, third, cell type, and fourth, other interacting molecules.

Metformin and cancer: new applications for an old drug

Metformin, one of most widely prescribed oral hypoglycemic agents, has recently received increased attention because of its potential antitumorigenic effects that are thought to be independent of its hypoglycemic effects. Several potential mechanisms have been suggested for the ability of metformin to suppress cancer growth in vitro and vivo: (1) activation of LKB1/AMPK pathway, (2) induction of cell cycle arrest and/or apoptosis, (3) inhibition of protein synthesis, (4) reduction in circulating insulin levels, (5) inhibition of the unfolded protein response (UPR), (6) activation of the immune system, and (7) eradication of cancer stem cells. There is also a growing number of evidence, mostly in the form of retrospective clinical studies that suggest that metformin may be associated with a decreased risk of developing cancer and with a better response to chemotherapy. There are currently several ongoing randomized clinical trials that incorporate metformin as an adjuvant to classic chemotherapy and aim to evaluate its potential benefits in this setting. This review highlights basic aspects of the molecular biology of metformin and summarizes new advances in basic science as well as intriguing results from recent clinical studies.

Will targeting insulin growth factor help us or hurt us?: An oncologist's perspective

The insulin/insulin growth factor (IGF) pathway is a critical mediator of longevity and aging. Efforts to extend longevity by altering the insulin/IGF pathway may have varying effects on other physiological processes. Reduced insulin/IGF levels may decrease the incidence of certain cancers as well as the risk of developing metastatic disease. However, it may also increase the risk of developing cardiovascular disease as well as cardiovascular related mortality. Pursuing the right insulin/IGF pathway targets will require striking a balance between inhibiting cancer cell development and progression and avoiding damage to tissues under normal insulin/IGF-mediated control. This review will discuss the roles of the insulin/IGF pathway in aging and longevity and the development of cancer cell metastasis and considerations in taking insulin/IGF directed targets to the oncology clinic.

Diabetes and cancer: a consensus report

Epidemiologic evidence suggests that cancer incidence is associated with diabetes as well as certain diabetes risk factors and diabetes treatments. This consensus statement of experts assembled jointly by the American Diabetes Association and the American Cancer Society reviews the state of science concerning 1) the association between diabetes and cancer incidence or prognosis, 2) risk factors common to both diabetes and cancer, 3) possible biologic links between diabetes and cancer risk, and 4) whether diabetes treatments influence risk of cancer or cancer prognosis. In addition, key unanswered questions for future research are posed.

Bone and wound healing augmentation with platelet-rich plasma

Over the past two decades, autologous platelets that have been sequestered, concentrated, and mixed with thrombin to generate growth factor-concentrated platelet-rich plasma for application to bone and wounds to aide healing have been a subject of great interest. This article reviews the literature related to the use of autologous platelet-rich plasma in bone and wound healing, and reviews the processes necessary to secure a high concentration of viable platelets. Although not yet definitive, autologous platelet-rich plasma has been shown to be safe, reproducible, and effective in mimicking the natural process of bone and wound healing.

The direct binding of insulin-like growth factor-1 (IGF-1) to integrin alphavbeta3 is involved in IGF-1 signaling

It has been proposed that ligand occupancy of integrin alphavbeta3 with extracellular matrix ligands (e.g. vitronectin) plays a critical role in insulin-like growth factor-1 (IGF-1) signaling. We found that expression of alphavbeta3 enhanced IGF-1-induced proliferation of Chinese hamster ovary cells in serum-free conditions (in the absence of vitronectin). We hypothesized that the direct integrin binding to IGF-1 may play a role in IGF-1 signaling. We demonstrated that alphavbeta3 specifically and directly bound to IGF-1 in cell adhesion, enzyme-linked immunosorbent assay-type binding, and surface plasmon resonance studies. We localized the amino acid residues of IGF-1 that are critical for integrin binding by docking simulation and mutagenesis. We found that mutating two Arg residues at positions 36 and 37 in the C-domain of IGF-1 to Glu (the R36E/R37E mutation) effectively reduced integrin binding. Interestingly, although the mutant still bound to IGF1R, it was defective in inducing IGF1R phosphorylation, AKT and ERK1/2 activation, and cell proliferation. Furthermore wild type IGF-1 mediated co-precipitation of alphavbeta3 and IGF1R, whereas the R36E/R37E mutant did not, suggesting that IGF-1 mediates the interaction between alphavbeta3 and IGF1R. These results suggest that the direct binding to IGF-1 to integrin alphavbeta3 plays a role in IGF-1 signaling through ternary complex formation (alphavbeta3-IGF-IGF1R), and integrin-IGF-1 interaction is a novel target for drug discovery.

Cooperation between integrin alphavbeta3 and VEGFR2 in angiogenesis

The cross-talk between receptor tyrosine kinases and integrin receptors are known to be crucial for a number of cellular functions. On endothelial cells, an interaction between integrin alphavbeta3 and VEGFR2 seems to be particularly important process during vascularization. Importantly, the functional association between VEGFR2 and integrin alphavbeta3 is of reciprocal nature since each receptor is able to promote activation of its counterpart. This mutually beneficial relationship regulates a number of cellular activities involved in angiogenesis, including endothelial cell migration, survival and tube formation, and hematopoietic cell functions within vasculature. This article discusses several possible mechanisms reported by different labs which mediate formation of the complex between VEGFR-2 and alphavbeta3 on endothelial cells. The pathological consequences and regulatory events involved in this receptor cross-talk are also presented.

IGF-I secreted by osteoblasts acts as a potent chemotactic factor for osteoblasts

Osteoblast recruitment to the site of future bone formation is essential for skeletal development, bone remodeling and fracture healing. A number of factors associated with bone tissue have been reported to induce directional migration of osteoblasts but the mechanism remains to be clarified. In this study, to explore a major chemotactic factor(s) for osteoblasts, we examined the serum-free medium conditioned by MC3T3-E1 osteoblast-like cells for its ability to induce osteoblast migration. Employing sequential chromatography and tandem mass spectrometry analysis, we purified and identified IGF-I as a potent chemotactic factor from the conditioned medium. IGF-I induced cell migration of both MC3T3-E1 cells and primary mouse osteoblasts, and checkerboard analysis revealed that IGF-I markedly induced directional migration (chemotaxis) of osteoblasts. Neutralization of mouse IGF-I with monoclonal antibodies resulted in delayed osteoblast monolayer wound healing and cellular polarization but addition of human IGF-I reversed these effects. IGF-I also promoted cell spreading on fibronectin in an integrin beta1-dependent manner. IGF-I induced Akt and Rac activation and localized accumulation of phosphatidylinositol 3,4,5-triphosphate (PtdIns (3,4,5)P3) at the membrane in osteoblasts. The phosphatidyl inositol 3 kinase (PI3K) inhibitor LY294002 inhibited IGF-I-induced cell migration and wound healing. Together, the results suggest that IGF-I secreted from osteoblasts in the bone tissue is a potent chemotactic factor that may play a major role in recruitment of osteoblasts during bone formation.

Arterial smooth muscle cells dysfunction in hyperglycaemia and hyperglycaemia associated with hyperlipidaemia: from causes to effects

Given the important role of smooth muscle cells in arterial wall dysfunction in diabetes, as well as in diabetes associated with accelerated atherosclerosis, we provide a brief review of the recent achievements in identification of signalling molecules underlying their altered cellular responses, and examine the consequences of these pathological insults on smooth muscle cells properties. The original results emerging from the Golden Syrian hamster model (rendered diabetic or simultaneously hyperlipidaemic-diabetic) and from human aortic smooth muscle cells cultured in 25 mM glucose (to mimic diabetic condition) or sera of obese type 2 diabetic patients (to mimic the metabolic syndrome condition) are presented in this context. We conclude this review with several open issues disclosed by the most recent literature that deserve essential attention for targeting the translational medicine.

Substrate-bound insulin-like growth factor (IGF)-I-IGF binding protein-vitronectin-stimulated breast cell migration is enhanced by coactivation of the phosphatidylinositide 3-Kinase/AKT pathway by alphav-integrins and the IGF-I receptor

IGF-I can bind to the extracellular matrix protein vitronectin (VN) through the involvement of IGF-binding proteins-2, -3, -4, and -5. Because IGF-I and VN have established roles in tumor cell dissemination, we were keen to investigate the functional consequences of the interaction of IGF-I, IGF binding proteins (IGFBPs), and VN in tumor cell biology. Hence, functional responses of MCF-7 breast carcinoma cells and normal nontumorgenic MCF-10A mammary epithelial cells were investigated to allow side-by-side comparisons of these complexes in both cancerous and normal breast cells. We demonstrate that substrate-bound IGF-I-IGFBP-VN complexes stimulate synergistic increases in cellular migration in both cell types. Studies using IGF-I analogs determined this stimulation to be dependent on both heterotrimeric IGF-I-IGFBP-VN complex formation and the involvement of the IGF-I receptor (IGF-IR). Furthermore, the enhanced cellular migration was abolished on incubation of MCF-7 and MCF-10A cells with function blocking antibodies directed at VN-binding integrins and the IGF-IR. Analysis of the signal transduction pathways underlying the enhanced cell migration revealed that the complexes stimulate a transient activation of the ERK/MAPK signaling pathway while simultaneously producing a sustained activation of the phosphatidylinositide 3-kinase/AKT pathway. Experiments using pharmacological inhibitors of these pathways determined a requirement for phosphatidylinositide 3-kinase/AKT activation in the observed response. Overexpression of wild type and activated AKT further increases substrate-bound IGF-I-IGFBP-VN-stimulated migration. This study provides the first mechanistic insights into the action of IGF-I-IGFBP-VN complexes and adds further evidence to support the involvement of VN-binding integrins and their cooperativity with the IGF-IR in the promotion of tumor cell migration.