The IGF system in thyroid cancer: new concepts

High prevalence of papillary thyroid cancer in Korean women with insulin resistance

BACKGROUND

The purpose of this study was to determine if hyperinsulinemia and/or insulin resistance are/is associated with the prevalence of papillary thyroid cancer (PTC) in Korean women.

METHODS

This study included 735 female patients with PTC and 537 female non-PTC control subjects. Multiple logistic regression analysis was performed to evaluate the associations between hyperinsulinemia/insulin resistance and the occurrence of PTC.

RESULTS

The prevalence of PTC was significantly correlated with increased insulin, glucose levels, and a high homeostasis model of assessment-insulin resistance (HOMA-IR). The multivariate adjusted odds ratios for the prevalence of PTC in the highest quartile groups for insulin, glucose, and HOMA-IR were 2.88, 9.32, and 4.07 (all p < .001), respectively, compared with the lowest quartile groups. Pathological analyses revealed that increased serum glucose, insulin levels, and a higher HOMA-IR were associated with the multifocality of PTC.

CONCLUSION

Hyperinsulinemia and/or insulin resistance may be associated with the development of PTC, but not disease severity in Korean women.

Insulin resistance is another factor that increases the risk of recurrence in patients with thyroid cancer

The objective of this study was to evaluate the initial response to treatment and the long-term outcome of patients with papillary thyroid cancer (PTC), according to the modified 2014 risk of recurrence classification of the American Thyroid Association and the presence or absence of insulin resistance (IR). We retrospectively reviewed our database of 636 records and selected 171 patients in whom we had previously validated the ATA risk of recurrence (RR) classification. From these patients, 38 non-diabetic subjects were included for analysis according to the following criteria: age older than 18 years, classic papillary thyroid carcinoma, stable body mass index 5 years previous to PTC diagnosis and during the entire time of follow-up, low and intermediate RR, follow-up after initial treatment at least for 3 years, and absence of any drug treatment for the metabolic syndrome. The IR was evaluated through the homeostasis model assessment (HOMA) index. When equal or higher than 2.5, patients were considered as harboring IR. The initial response to treatment was classified as remission or persistent disease (biochemical and/or structural). The clinical status at final follow-up was defined as no evidence of disease, biochemical persistent disease, structural persistent disease, or recurrence (biochemical or structural disease identified after a period of no evidence of disease). RR was as follows: low: n=15, intermediate: n=23. The median follow-up of this patient cohort was 5.5 years (range 3-22 years). We found no statistically significant differences when the response to initial treatment was considered in low-risk patients with or without IR. However, remission was more frequently found in those patients without IR when the intermediate RR was considered (36 vs. 11%, p=0.01). When considering the status at final follow-up, we found more frequency of structural persistent disease in both, low and intermediate RR patients with IR (10 vs. 0%, p=0.02 and 45 vs.7%, p=0.01, respectively). In this series of patients with PTC, the state of IR was associated with increased frequency of structural persistent disease at final follow-up. The IR could have a deleterious effect on the outcome of patients with PTC.

The Novel Functions of High-Molecular-Mass Complexes Containing Insulin Receptor Substrates in Mediation and Modulation of Insulin-Like Activities: Emerging Concept of Diverse Functions by IRS-Associated Proteins

Insulin-like peptides, such as insulin-like growth factors (IGFs) and insulin, induce a variety of bioactivities, such as growth, differentiation, survival, increased anabolism, and decreased catabolism in many cell types and in vivo. In general, IGFs or insulin bind to IGF-I receptor (IGF-IR) or insulin receptor (IR), activating the receptor tyrosine kinase. Insulin receptor substrates (IRSs) are known to be major substrates of receptor kinases, mediating IGF/insulin signals to direct bioactivities. Recently, we discovered that IRSs form high-molecular-mass complexes (referred to here as IRSomes) even without IGF/insulin stimulation. These complexes contain proteins (referred to here as IRSAPs; IRS-associated proteins), which modulate tyrosine phosphorylation of IRSs by receptor kinases, control IRS stability, and determine intracellular localization of IRSs. In addition, in these complexes, we found not only proteins that are involved in RNA metabolism but also RNAs themselves. Thus, IRSAPs possibly contribute to modulation of IGF/insulin bioactivities. Since it is established that disorder of modulation of insulin-like activities causes various age-related diseases including cancer, we could propose that the IRSome is an important target for treatment of these diseases.

Novel Aspects Concerning the Functional Cross-Talk between the Insulin/IGF-I System and Estrogen Signaling in Cancer Cells

The insulin/IGF system plays an important role in cancer progression. Accordingly, elevated levels of circulating insulin have been associated with an increased cancer risk as well as with aggressive and metastatic cancer phenotypes. Numerous studies have documented that estrogens cooperate with the insulin/IGF system in multiple pathophysiological conditions. The biological responses to estrogens are mainly mediated by the estrogen receptors (ER)α and ERβ, which act as transcription factors; however, several studies have recently demonstrated that a member of the G protein-coupled receptors, named GPR30/G-protein estrogen receptor (GPER), is also involved in the estrogen signaling in normal and malignant cells as well as in cancer-associated fibroblasts (CAFs). In this regard, novel mechanisms linking the action of estrogens through GPER with the insulin/IGF system have been recently demonstrated. This review recapitulates the relevant aspects of this functional cross-talk between the insulin/IGF and the estrogenic GPER transduction pathways, which occurs in various cell types and may account for cancer progression.

Obesity and thyroid cancer

Many studies have provided observational data on the association of obesity and thyroid cancers, but only few of them propose mechanisms that would permit a better understanding of the causal molecular mechanisms of this association. Considering that there is an increasing incidence of both obesity and thyroid cancers, we need to summarize and link recent studies in order to characterize and understand the contribution of obesity-related factors that might affect thyroid cancer development and progression. Adipose tissue is involved in many vital processes, including insulin sensitivity, angiogenesis, regulation of energy balance, activation of the complement system, and responses such as inflammation. Although these processes have their own molecular pathways, they involve the same molecules through which obesity and adipose tissue might exert their roles in carcinogenesis, not only affecting MAPK and PI3K or even insulin pathways, but also recruiting local inflammatory responses that could result in disease formation and progression. This review describes five important issues that might explain the link between excessive weight and thyroid cancer: thyroid hormones, insulin resistance, adipokines, inflammation, and sexual hormones.

Treatment with human insulin does not increase thyroid cancer risk in patients with type 2 diabetes

BACKGROUND

Whether human insulin therapy may increase thyroid cancer risk in patients with type 2 diabetes mellitus (T2DM) has not been investigated.

MATERIALS AND METHODS

The reimbursement databases of all Taiwanese diabetic patients from 1996 to 2009 were retrieved from the Bureau of National Health Insurance. The entry date was set at 1 January 2004, and 968,384 patients with T2DM were followed up for thyroid cancer incidence until the end of 2009. Ever-users, never-users and subgroups of human insulin exposure (using tertile cut-offs of time since starting insulin, duration of therapy and cumulative dose) at entry date were calculated for thyroid cancer incidence. Insulin glargine was not marketed until after the entry date. Therefore, to exclude the potential contamination of insulin glargine, patients who happened to use insulin glargine were censored at the time of its initiation when calculating the period of follow-up. Hazard ratios were estimated by Cox regression.

RESULTS

There were 111,121 ever-users and 857,263 never-users of human insulin, with respective numbers of incident thyroid cancer of 118 (0·11%) and 1047 (0·12%), and respective incidences of 23·9 and 23·8 per 100,000 person-years. The overall hazard ratios (95% confidence intervals) did not show a significant association with human insulin in either the age-sex-adjusted or the fully adjusted model: 0·942 (0·778-1·141) and 1·096 (0·888-1·353), respectively. When categorized into tertiles of the dose-response parameters, none of the hazard ratios was significant.

CONCLUSIONS

This study does not support the role of human insulin therapy in increasing the risk of thyroid cancer in patients with T2DM.

The prevalence of thyroid nodules and its relationship with metabolic parameters in a Chinese community-based population aged over 40 years

To investigate the prevalence of thyroid nodules (TN) among a community population aged >40 years and to explore the association between TN and its metabolic risk factors. Data from 9,533 adults aged over 40 years who participated in the epidemiological investigation of thyroid nodules in a Chinese community-based population from June to December 2011 were included in the analyses. We compared the levels of metabolic indices between the TN group and healthy controls. The prevalence of TN was 46.6% (39.7%, men; 50.3%, women) and it increased significantly with increasing age (P < 0.001). It was significantly higher in the group with hypertension than in that with normotension (P < 0.001) and was 43.0% in the normal blood glucose group, 49.4% in the prediabetes group, and 50.9% in the diabetes group (P < 0.001). Logistic regression analysis indicated that hypertension [odds ratio (OR) = 1.121 (1.025-1.225)] as well as prediabetes and diabetes [OR = 1.130 (1.036-1.233)] were all independent risk factors for TN after adjustment for sex, age, body mass index, blood lipid levels, smoking status, and alcohol consumption. The elderly population had a high prevalence of TN. Hypertension as well as prediabetes and diabetes might be independent risk factors for TN.

The epidemic of thyroid cancer in the United States: the role of endocrinologists and ultrasounds

BACKGROUND

The incidence of thyroid cancer has increased at an alarming rate in both men and women in the United States. The etiology of this epidemic is unclear. We tested the hypothesis that a significant component of this epidemic is due to increased detection of occult disease. We examined whether the density of endocrinologists and general surgeons as well as employment of cervical ultrasonography were factors associated with this epidemic.

METHODS

Thyroid cancer incidence rates by states were obtained from the United States Cancer Statistics 1999-2009 reported by the National Program of Cancer Registries. The densities of endocrinologists and general surgeons and the employment of cervical ultrasonography were calculated on a statewide basis and correlated with the incidence of thyroid cancer.

RESULTS

Age-standardized incidence rates of thyroid cancer have increased in every state in the United States. Significant regional variations were noted, with the highest incidence rates in the northeast and the lowest in the south. The incidence rates were significantly correlated with the density of endocrinologists (r = 0.58, p<0.0001 for males; r = 0.44, p = 0.0031 for females) and the employment of cervical ultrasonography (r = 0.40, p = 0.0091 for males; r = 0.36, p = 0.0197 for females). Both the density of endocrinologists and general surgeons and employment of cervical ultrasonography could explain 57% of the variability in state-level incidence for males and 49% for females.

CONCLUSIONS

These data offer evidence to suggest that the epidemic of thyroid cancer is due to increased detection of a reservoir of previously occult disease. The increased detection of thyroid cancer results in therapeutic interventions including surgery and radioactive thyroid treatment that may be of limited benefit.

An analysis of the relative risk for goitre in euthyroid patients with type 2 diabetes

AIM

To assess the relative risk for goitre in a cohort of euthyroid patients with type 2 diabetes with special reference to the use of metformin and insulin therapy.

PATIENTS AND METHODS

Eight hundred euthyroid patients with type 2 diabetes (433 women, mean age 65·8 ± 12·5 years) and 671 euthyroid subjects without diabetes were retrospectively evaluated. There were 250 patients on metformin and 455 patients on insulin treatment.

RESULTS

The gender-, age-, body mass index- and thyrotropin (TSH)-adjusted relative risk for goitre occurring among diabetic patients relative to controls was 3·01 (1·61-5·64) (P < 0·01). This odds ratio was significant in females, patients with and without metformin therapy, patients without insulin therapy and without micro- and macrovascular complications of diabetes. However, male pateints, patients on insulin therapy or with micro- or macroangiopathy did not exhibit an increase in the risk of goitre. Patients on metformin therapy showed a significant increase in the risk of goitre only in the absence of insulin therapy. Multi-adjusted logistic regression analysis showed that goitre was significantly related to gender, TSH and haemoglobin A1c levels. Metformin and insulin therapy were nonsignificant variables in this model.

CONCLUSION

This is the first survey analysing the relationship between the presence of palpable goitre and clinical parameters in a large cohort of patients with type 2 diabetes. Our data suggest a significant relationship between goitre and glycaemic control, but do not support the presence of independent and significant relationships between goitre and metformin or insulin treatment in euthyroid patients with type 2 diabetes.

Non-islet cell tumor-induced hypoglycemia associated with macronodular pulmonary metastases from poorly differentiated thyroid carcinoma

BACKGROUND

Non-islet cell tumor-induced hypoglycemia (NICTH), a major cause of fasting hypoglycemia, is caused by the overproduction of incompletely processed, high molecular-weight insulin-like growth factor-II (IGF-II), termed "big" IGF-II. To the best of our knowledge, only two cases of thyroid carcinoma associated with NICTH have been documented.

PATIENT FINDINGS

We report the case of a 72-year-old woman who was brought to the emergency department with impaired consciousness. The patient had a history of pulmonary metastases from poorly differentiated thyroid carcinoma (PDTC), spanning 12 years since initial treatment. Laboratory tests showed decreased plasma glucose levels even though immunoreactive insulin, IGF-I, and growth hormone (GH) were undetectable. Computed tomography (CT) scan revealed macronodular pulmonary metastases the estimated volume of which was 456 mL. Both the biochemical data and imaging results suggested NICTH. The results of Western blot analysis performed on a fractionated serum sample showed an increased expression of big IGF-II, an important indicator in the diagnosis of NICTH. Because the massive pulmonary metastases were considered inoperable, immunohistochemical analysis of stored formalin-fixed, paraffin-embedded tissues was performed. The analysis revealed that the tumor cells were positive for both IGF-II and thyroglobulin. A whole-body CT excluded extrapulmonary metastatic lesions. A retrospective review revealed a gradual decrease in glycohemoglobin levels accompanied by an increase in the estimated volume of pulmonary metastases. These findings suggested that NICTH had been caused by pulmonary metastases from PDTC.

CONCLUSIONS

We describe here the third reported case of NICTH associated with thyroid carcinoma. This is also the first case reporting big IGF-II in the serum of a patient with thyroid carcinoma.

Insulin receptor (IR) and insulin-like growth factor receptor 1 (IGF-1R) signaling systems: novel treatment strategies for cancer

Insulin and insulin-like growth factor (IGF) signaling system, commonly known for fine-tuning numerous biological processes, has lately made its mark as a much sought-after therapeutic targets for diabetes and cancer. These receptors make an attractive anticancer target owing to their overexpression in variety of cancer especially in prostate and breast cancer. Inhibitors of IGF signaling were subjected to clinical cancer trials with the main objective to confirm the effectiveness of these receptors as a therapeutic target. However, the results that these trials produced proved to be disappointing as the role played by the cross talk between IGF and insulin receptor (IR) signaling pathways at the receptor level or at downstream signaling level became more lucid. Therapeutic strategy for IGF-1R and IR inhibition mainly encompasses three main approaches namely receptor blockade with monoclonal antibodies, tyrosine kinase inhibition (ATP antagonist and non-ATP antagonist), and ligand neutralization via monoclonal antibodies targeted to ligand or recombinant IGF-binding proteins. Other drug-discovery approaches are employed to target IGF-1R, and IR includes antisense oligonucleotides and recombinant IGF-binding proteins. However, therapies with monoclonal antibodies and tyrosine kinase inhibition targeting the IGF-1R are not evidenced to be satisfactory as expected. Factors that are duly held responsible for the unsuccessfulness of these therapies include (a) the existence of the IR isoform A overexpressed on a variety of cancers, enhancing the mitogenic signals to the nucleus leading to the endorsement of cell growth, (b) IGF-1R and IR that form hybrid receptors sensitive to the stimulation of all three IGF axis ligands, and (c) IGF-1R and IR that also have the potential to form hybrid receptors with other tyrosine kinase to potentiate the cellular transformation, tumorigenesis, and tumor vascularization. This mini review is a concerted effort to explore and fathom the well-recognized roles of the IRA signaling system in human cancer phenotype and the main strategies that have been so far evaluated to target the IR and IGF-1R.

The relationship between thyroid volume and malignant thyroid disease

The present retrospective study aimed to investigate the relationship between thyroid volume and prevalence of thyroid cancer. We investigated the data of 3,850 patients who underwent fine-needle aspiration biopsy (FNAB). Biopsy results were evaluated as diagnostic or nondiagnostic, and diagnostic results were classified as benign, malignant, and indeterminate. We included 2,672 patients who underwent FNAB firstly in our hospital and evaluated as diagnostic biopsy except subgroup of indeterminate. We obtained cytologic data, levels of serum thyroid-stimulating hormone (TSH), and thyroid volumes of those patients retrospectively. Among 2,672 patients with thyroid nodule, 2,562 (95.9 %) patients had benign cytology and 110 (%4,1) patients had malignant cytology. There was no correlation between the malignancy and gender (p = 0.935), and patients with malignant cytology were younger (52 vs 59, p < 0.001). Also, TSH levels were higher in patients with malignant than benign cytology (p = 0.017). Median volume of right part, left part, and total thyroid for patients who had malignant cytology was significantly lower than patients who had benign cytology (8.3, 7.1, 15.9 vs 10.8 ml, 9.0 mml, 20.6 ml, respectively, p ≤ 0.001 for all parameters). The results demonstrated that thyroid cancer prevalence was higher in patients with low thyroid volume. According to our results, thyroid volume should be considered as a risk factor for malignancy in the evaluation of thyroid nodules.

Obesity and thyroid cancer: epidemiologic associations and underlying mechanisms

The incidence of thyroid cancer has been rising over the past few decades along with a parallel increase in obesity. Observational studies have provided evidence for a potential association between the two. By contrast, clinical data for a link between type 2 diabetes mellitus, a condition strongly associated with obesity, and thyroid cancer are limited and largely not supportive of such an association. Obesity leads to hypoadiponectinemia, a pro-inflammatory state, and insulin resistance, which, in turn, leads to high circulating insulin and insulin-like growth factor-1 levels, thereby possibly increasing the risk for thyroid cancer. Thus, insulin resistance possibly plays a pivotal role in underlying the observed association between obesity and thyroid cancer, potentially leading to the development and/or progression of thyroid cancer, through its interconnections with other factors including insulin-like growth factor-1, adipocytokines/cytokines and thyroid-stimulating hormone. In this review, epidemiological and clinical evidence and potential mechanisms underlying the proposed association between obesity and thyroid cancer risk are reviewed. If the association between obesity and thyroid cancer demonstrated in observational studies proves to be causal, targeting obesity (and/or downstream mediators of risk) could be of importance in the prevention and management of thyroid cancer.

Diabetes and cancer relationships

Diabetes and cancer are both heterogeneous and multifactorial diseases with tremendous impact on health worldwide. Epidemiologic evidence suggests that certain malignancies may be associated with diabetes, as well as with diabetes risk factors and, perhaps, with certain diabetes treatments. Numerous biological mechanisms could account for these relationships. Insulin-like growth factor (IGF)-1, IGF-2, IGF-1 receptors, insulin, and the insulin receptor play roles in the development and progression of cancers. Although evidence from randomized controlled trials does not support or refute associations of diabetes and its treatments with either increased or reduced risk of cancer incidence or prognosis, consideration of malignancy incidence rates and the magnitude of the trials that would be required to address these issues explains why such studies may not be readily undertaken.

The impact of low-dose insulin on peripheral nerve insulin receptor signaling in streptozotocin-induced diabetic rats

BACKGROUND

The precise mechanisms of the neuroprotective effects of insulin in streptozotocin (STZ)-induced diabetic animals remain unknown, but altered peripheral nerve insulin receptor signaling due to insulin deficiency might be one cause.

METHODOLOGY AND PRINCIPAL FINDINGS

Diabetes was induced in 10-week-old, male Wistar rats by injecting them with STZ (45 mg/kg). They were assigned to one group that received half of an insulin implant (∼1 U/day; I-group, n = 11) or another that remained untreated (U-group, n = 10) for 6 weeks. The controls were age- and sex-matched, non-diabetic Wistar rats (C-group, n = 12). Low-dose insulin did not change haemoglobin A1c, which increased by 136% in the U-group compared with the C-group. Thermal hypoalgesia and mechanical hyperalgesia developed in the U-group, but not in the I-group. Sensory and motor nerve conduction velocities decreased in the U-group, whereas sensory nerve conduction velocity increased by 7% (p = 0.0351) in the I-group compared with the U-group. Western blots showed unaltered total insulin receptor (IR), but a 31% decrease and 3.1- and 4.0-fold increases in phosphorylated IR, p44, and p42 MAPK protein levels, respectively, in sciatic nerves from the U-group compared with the C-group. Phosphorylated p44/42 MAPK protein decreased to control levels in the I-group (p<0.0001).

CONCLUSIONS AND SIGNIFICANCE

Low-dose insulin deactivated p44/42 MAPK and ameliorated peripheral sensory nerve dysfunction in rats with STZ-induced diabetes. These findings support the notion that insulin deficiency per se introduces impaired insulin receptor signaling in type 1 diabetic neuropathy.

A twenty-first century cancer epidemic caused by obesity: the involvement of insulin, diabetes, and insulin-like growth factors

Obesity has reached epidemic proportions in the developed world. The progression from obesity to diabetes mellitus type 2, via metabolic syndrome, is recognised, and the significant associated increase in the risk of major human cancers acknowledged. We review the molecular basis of the involvement of morbidly high concentrations of endogenous or therapeutic insulin and of insulin-like growth factors in the progression from obesity to diabetes and finally to cancer. Epidemiological and biochemical studies establish the role of insulin and hyperinsulinaemia in cancer risk and progression. Insulin-like growth factors, IGF-1 and IGF-2, secreted by visceral or mammary adipose tissue have significant paracrine and endocrine effects. These effects can be exacerbated by increased steroid hormone production. Structural studies elucidate how each of the three ligands, insulin, IGF-1, and IGF-2, interacts differently with isoforms A and B of the insulin receptor and with type I IGF receptor and explain how these protagonists contribute to diabetes-associated cancer. The above should inform appropriate treatment of cancers that arise in obese individuals and in those with diabetes mellitus type 2. Novel drugs that target the insulin and insulin-like growth factor signal transduction pathways are in clinical trial and should be effective if appropriate biomarker-informed patient stratification is implemented.

The role of insulin and IGF system in pancreatic cancer

The importance of the IGF system in carcinogenesis has been established for many solid cancers. It is well known that individuals with higher circulating levels of the IGF1 ligand present an increased risk of cancer. However, therapies with monoclonal antibodies targeting the IGF1 receptor (IGF1R) have been largely unsuccessful. One of the potential reasons for this failure is the existence of the highly homologous insulin receptor (IR), which appears to be at least equally efficient as the IGF1R in the transition of mitogenic signals to the nucleus and promotion of cell growth. Furthermore, IGF1 and insulin receptors can form hybrid receptors sensitive to stimulation of all three ligands of the system: insulin, IGF1, and IGF2. Although the connection between insulin, diabetes, and cancer has been established for years now, clear evidence that demonstrate the redundancy of insulin and insulin receptors and insulin-like growth factors and their receptors in cancer is missing. In this review, we focus on the contribution of insulin and IGFs to carcinogenesis in the insulin-producing organ, the pancreas. We give a short summary on the complexity of insulin and the IGF system in the pancreas and their potential roles in pancreatic cancer, especially pancreatic ductal adenocarcinoma. Finally, we discuss drug-targeting options of this system and the rationale of simultaneous targeting of both the insulin and the IGF systems.

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.

Insulin and insulin like growth factor II endocytosis and signaling via insulin receptor B

Background

Insulin and insulin-like growth factors (IGFs) act on tetrameric tyrosine kinase receptors controlling essential functions including growth, metabolism, reproduction and longevity. The insulin receptor (IR) binds insulin and IGFs with different affinities triggering different cell responses.

Results

We showed that IGF-II induces cell proliferation and gene transcription when IR-B is over-expressed. We combined biotinylated ligands with streptavidin conjugated quantum dots and visible fluorescent proteins to visualize the binding of IGF-II and insulin to IR-B and their ensuing internalization. By confocal microscopy and flow cytometry in living cells, we studied the internalization kinetic through the IR-B of both IGF-II, known to elicit proliferative responses, and insulin, a regulator of metabolism.

Conclusions

IGF-II promotes a faster internalization of IR-B than insulin. We propose that IGF-II differentially activates mitogenic responses through endosomes, while insulin-activated IR-B remains at the plasma membrane. This fact could facilitate the interaction with key effector molecules involved in metabolism regulation.

Prevalence of goiter and thyroid nodular disease in patients with class III obesity

OBJECTIVES: To evaluate the prevalence of goiter and nodular disease in patients with class III obesity, and to correlate results with serum leptin levels and insulin resistance (IR) parameters. SUBJECTS AND METHODS: A cross-sectional study was performed to assess thyroid ultrasound (US) patterns, HOMA-IR, serum leptin, and TSH levels in obese patients and controls. RESULTS: Thyroid volume was positively correlated with body mass index (BMI) (r = 0.240, p = 0.039) and with HOMA-IR (r = 0.329; p < 0.01). Thyroid US patterns were similar between groups. However, when data from the male group was considered, greater thyroid volume was detected in the obese group compared with controls (10.8 vs. 8.5 cm³; p = 0.04). Also, nodules were more frequently detected (67% vs. 18%), as were nodules requiring FNAB (33.3% vs. 0%, p ≥ 0.05-0.09), in this group. CONCLUSION: Although IR did not correlate directly with the presence of nodules, the results support the hypothesis of a direct association between insulin resistance and thyroid volume.

Metabolic changes enhance the cardiovascular risk with differentiated thyroid carcinoma--a case control study from Manipal Teaching Hospital of Nepal

OBJECTIVE

To evaluate several metabolic changes in patients with differentiated thyroid carcinoma (DTC ) which enhance cardiovascular risk in the western region of Nepal.

MATERIALS AND METHODS

This hospital based case control study was carried out using data retrieved from the register maintained in the Department of Biochemistry of the Manipal Teaching Hospital, Pokhara, Nepal between 1st January, 2009 and 31st December, 2011. The variables collected were age, gender, BMI, glucose, insulin, HbA1C, CRP, fibrinogen, total cholesterol, triglycerides, HDL, LDL, VLDL, f-T3, f-T4, TSH. One way ANOVA was used to examine statistical significance of differences between groups, along with the Post Hoc test LSD for comparison of means.

RESULTS

fT3 values were markedly raised in DTC cases (5.7±SD1.4) when compared to controls (2.2±SD0.9). Similarly, fT4 values were also moderately raised in cases of DTC (4.9±SD1.3 and 1.7 ±SD0.9). In contrast, TSH values were lowered in DTC cases (0.39±SD0.4) when compared to controls (4.2 ±SD 1.4). Mean blood glucose levels were decreased while insulin was increased and HDL reduced (39.5±SD4.7 as compared to the control 43.1±SD2.2).

CONCLUSION

Cardiovascular risk may be aggravated by insulin resistance, a hypercoagulable state, and an atherogenic lipid profile in patients with differentiated thyroid cancer.

Recreational physical activity and risk of papillary thyroid cancer among women in the California Teachers Study

PURPOSE

Little is known about the relationship between physical activity and thyroid cancer risk, and few cohort data on this association exist. Thus, the present study aimed to prospectively examine long-term activity and risk of papillary thyroid cancer among women.

METHODS

116,939 women in the California Teachers Study, aged 22-79 years with no history of thyroid cancer at cohort entry, were followed from 1995-1996 through 2009; 275 were diagnosed with invasive papillary thyroid cancer. Cox proportional-hazards regression provided relative risk (RR) estimates and 95% confidence intervals (CI) for associations between thyroid cancer and combined strenuous and moderate recreational physical activity both in the long-term (high school through age 54 years or current age if younger than 54 years) and recently (during the three years prior to joining the cohort).

RESULTS

Overall, women whose long-term recreational physical activity averaged at least 5.5 MET-hours/week (i.e. were active) had a non-significant 23% lower risk of papillary thyroid cancer than inactive women (RR = 0.77, 95% CI: 0.57, 1.04). RR estimates were stronger among normal weight or underweight women (body mass index, BMI<25.0 kg/m(2), trend p = 0.03) than among overweight or obese women (trend p = 0.35; homogeneity-of-trends p = 0.03). A similar pattern of risk was observed for recent activity (BMI<25 kg/m(2), trend p = 0.11; BMI≥25 kg/m(2), trend p = 0.16; homogeneity-of-trends p = 0.04). Associations for long-term activity did not appear to be driven by activity in any particular life period (e.g. youth, adulthood).

CONCLUSIONS

Long-term physical activity may reduce papillary thyroid cancer risk among normal weight and underweight women.

The insulin and igf-I pathway in endocrine glands carcinogenesis

Endocrine cancers are a heterogeneous group of diseases that may arise from endocrine cells in any gland of the endocrine system. These malignancies may show an aggressive behavior and resistance to the common anticancer therapies. The etiopathogenesis of these tumors remains mostly unknown. The normal embryological development and differentiation of several endocrine glands are regulated by specific pituitary tropins, which, in adult life, control the function and trophism of the endocrine gland. Pituitary tropins act in concert with peptide growth factors, including the insulin-like growth factors (IGFs), which are considered key regulators of cell growth, proliferation, and apoptosis. While pituitary TSH is regarded as tumor-promoting factor for metastatic thyroid cancer, the role of other pituitary hormones in endocrine cancers is uncertain. However, multiple molecular abnormalities of the IGF system frequently occur in endocrine cancers and may have a role in tumorigenesis as well as in tumor progression and resistance to therapies. Herein, we will review studies indicating a role of IGF system dysregulation in endocrine cancers and will discuss the possible implications of these findings for tumor prevention and treatment, with a major focus on cancers from the thyroid, adrenal, and ovary, which are the most extensively studied.

The relationship between glucose metabolism disorders and malignant thyroid disease

BACKGROUND

Previous studies have shown a positive relationship between insulin resistance and several common adult cancers. The present retrospective study aimed to investigate the association between glucose metabolism disorders (GMDs) and the prevalence of thyroid cancer.

METHODS

We investigated the data of 4272 patients who had undergone fine-needle aspiration biopsy (FNAB) of thyroid nodules. The biopsy results were evaluated as diagnostic or non-diagnostic and the diagnostic results were classified as benign, malignant, and indeterminate. In this study, we included 2234 of the above patients who had undergone FNAB at our hospital and whose biopsy results were evaluated as diagnostic and were classified as either benign or malignant. We obtained the cytologic data and the glucose metabolism status of these patients retrospectively.

RESULTS

Of the 2234 patients, 629 (28.1 %) had GMD (impaired fasting glucose, impaired glucose tolerance). Malignant cytology was determined in 106 (4.7 %) patients overall. Of the 629 patients with GMD, 582 (92.5 %) patients had benign cytology and 47 (7.5 %) patients had malignant cytology. Fifty-nine (3.7 %) of the 1605 normoglycemic patients had malignant cytology. Malignant cytology was determined more frequently ın the patients who had GMDs (p < 0.001).

CONCLUSION

The results demonstrated that thyroid cancer prevalence was higher in patients with GMD. According to our results, GMD should be considered as a risk factor for malignancy in the evaluation of thyroid nodules.

Heterodimerization of glycosylated insulin-like growth factor-1 receptors and insulin receptors in cancer cells sensitive to anti-IGF1R antibody

BACKGROUND

Identification of predictive biomarkers is essential for the successful development of targeted therapy. Insulin-like growth factor 1 receptor (IGF1R) has been examined as a potential therapeutic target for various cancers. However, recent clinical trials showed that anti-IGF1R antibody and chemotherapy are not effective for treating lung cancer.

METHODOLOGY/PRINCIPAL FINDINGS

In order to define biomarkers for predicting successful IGF1R targeted therapy, we evaluated the anti-proliferation effect of figitumumab (CP-751,871), a humanized anti-IGF1R antibody, against nine gastric and eight hepatocellular cancer cell lines. Out of 17 cancer cell lines, figitumumab effectively inhibited the growth of three cell lines (SNU719, HepG2, and SNU368), decreased p-AKT and p-STAT3 levels, and induced G 1 arrest in a dose-dependent manner. Interestingly, these cells showed co-overexpression and altered mobility of the IGF1R and insulin receptor (IR). Immunoprecipitaion (IP) assays and ELISA confirmed the presence of IGF1R/IR heterodimeric receptors in figitumumab-sensitive cells. Treatment with figitumumab led to the dissociation of IGF1-dependent heterodimeric receptors and inhibited tumor growth with decreased levels of heterodimeric receptors in a mouse xenograft model. We next found that both IGF1R and IR were N-linked glyosylated in figitumumab-sensitive cells. In particular, mass spectrometry showed that IGF1R had N-linked glycans at N913 in three figitumumab-sensitive cell lines. We observed that an absence of N-linked glycosylation at N913 led to a lack of membranous localization of IGF1R and figitumumab insensitivity.

CONCLUSION AND SIGNIFICANCE

The data suggest that the level of N-linked glycosylated IGF1R/IR heterodimeric receptor is highly associated with sensitivity to anti-IGF1R antibody in cancer cells.

Functional polymorphisms in the insulin-like binding protein-3 gene may modulate susceptibility to differentiated thyroid carcinoma in Caucasian Americans

The insulin-like growth factor (IGF) pathway is believed to play a pivotal role in thyroid carcinogenesis. Polymorphisms of IGF-1 and IGF binding protein-3 (IGFBP-3) have been associated with modulation of risk for the emergence of assorted common malignancies, but studies of the influence of such polymorphisms on risk of differentiated thyroid carcinoma (DTC) are lacking. In a case-control study of 173 DTC patients, 101 patients with benign thyroid disease, and 401 controls, an unconditional logistical regression model adjusted for age and sex was applied to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between polymorphisms of IGF-1 and IGFBP-3 and DTC risk. IGFBP-3 rs2132572 GA/AA genotypes were associated with a decreased risk of DTC (adjusted OR = 0.6, 95% CI: 0.4-0.9), particularly multifocal DTC (adjusted OR = 0.3, 95% CI: 0.1-0.7). The association with DTC was more evident in subjects with a first-degree family history of cancer (adjusted OR = 0.4, 95% CI: 0.2-0.7, P(interaction)  = 0.013) and non-drinkers (adjusted OR = 0.4, 95% CI: 0.2-0.7, P(interaction)  = 0.028). A four single nucleotide polymorphism haplotype of IGFBP-3 was associated with a decreased risk of DTC (adjusted OR = 0.7, 95% CI: 0.5-1.0, P = 0.030). Our study suggests that polymorphic IGFBP-3 may be involved in susceptibility to DTC.

Altered expression of insulin receptor isoforms in breast cancer

Purpose

Insulin-like growth factor (IGF) signaling through human insulin receptor isoform A (IR-A) contributes to tumorigenesis and intrinsic resistance to anti-IGF1R therapy. In the present study, we (a) developed quantitative TaqMan real time-PCR-based assays (qRT-PCR) to measure human insulin receptor isoforms with high specificity, (b) evaluated isoform expression levels in molecularly-defined breast cancer subtypes, and (c) identified the IR-A:IR-B mRNA ratio as a potential biomarker guiding patient stratification for anti-IGF therapies.

Experimental Design

mRNA expression levels of IR-A and IR-B were measured in 42 primary breast cancers and 19 matched adjacent normal tissues with TaqMan qRT-PCR assays. The results were further confirmed in 165 breast cancers. The tumor samples were profiled using whole genome microarrays and subsequently subtyped using the PAM50 breast cancer gene signature. The relationship between the IR-A:IR-B ratio and cancer subtype, as well as markers of proliferation were characterized.

Results

The mRNA expression levels of IR-A in the breast tumors were similar to those observed in the adjacent normal tissues, while the mRNA levels of IR-B were significantly decreased in tumors. The IR-A:IR-B ratio was significantly higher in luminal B breast cancer than in luminal A. Strong concordance between the IR-A:IR-B ratio and the composite Oncotype DX proliferation score was observed for stratifying the latter two breast cancer subtypes.

Conclusions

The reduction in IR-B expression is the key to the altered IR-A:IR-B ratio observed in breast cancer. The IR-A:IR-B ratio may have biomarker utility in guiding a patient stratification strategy for an anti-IGF therapeutic.

TSH compensates thyroid-specific IGF-I receptor knockout and causes papillary thyroid hyperplasia

Although TSH stimulates all aspects of thyroid physiology IGF-I signaling through a tyrosine kinase-containing transmembrane receptor exhibits a permissive impact on TSH action. To better understand the importance of the IGF-I receptor in the thyroid in vivo, we inactivated the Igf1r with a Tg promoter-driven Cre-lox system in mice. We studied male and female mice with thyroidal wild-type, Igf1r(+/-), and Igf1r(-/-) genotypes. Targeted Igf1r inactivation did transiently reduce thyroid hormone levels and significantly increased TSH levels in both heterozygous and homozygous mice without affecting thyroid weight. Histological analysis of thyroid tissue with Igf1r inactivation revealed hyperplasia and heterogeneous follicle structure. From 4 months of age, we detected papillary thyroid architecture in heterozygous and homozygous mice. We also noted increased body weight of male mice with a homozygous thyroidal null mutation in the Igf1r locus, compared with wild-type mice, respectively. A decrease of mRNA and protein for thyroid peroxidase and increased mRNA and protein for IGF-II receptor but no significant mRNA changes for the insulin receptor, the TSH receptor, and the sodium-iodide-symporter in both Igf1r(+/-) and Igf1r(-/-) mice were detected. Our results suggest that the strong increase of TSH benefits papillary thyroid hyperplasia and completely compensates the loss of IGF-I receptor signaling at the level of thyroid hormones without significant increase in thyroid weight. This could indicate that the IGF-I receptor signaling is less essential for thyroid hormone synthesis but maintains homeostasis and normal thyroid morphogenesis.

Relative associations of polycystic ovarian syndrome vs metabolic syndrome with thyroid function, volume, nodularity and autoimmunity

BACKGROUND

The relative associations of polycystic ovarian syndrome (PCOS) and metabolic syndrome (MS) with the risk for thyroid disease (thyroid function, volume, nodularity and autoimmunity) are unknown.We compared thyroid features and function in patients with PCOS and control subjects by the presence of MS.

METHODS

We recruited 84 women with PCOS and 81 age-matched healthy controls. PCOS was defined according to the Rotterdam criteria. Thyroid ultrasound and function tests were performed in all.

RESULTS

Although thyroid disease was more prevalent in women with PCOS, ovarian disease was not significantly associated with the risk for thyroid disease. Thyroid volume did not differ between women with PCOS and control subjects (13.7±8.6 vs 12.4±4.4 ml, respectively; p=0.2); however, it differed significantly between subjects with and without MS (regardless of PCOS status): 19.1±14.8 vs 12.4±4.9 ml, respectively; p=0.001). Antithyroglobulin and antithyroid peroxidase antibody levels also were significantly higher in subjects with MS, but not in participants with PCOS vs control subjects. Overall, TSH level correlated significantly with body mass index (BMI), weight, waist circumference, diastolic blood pressure, and levels of LDL cholesterol, triglycerides, and HDL cholesterol. Thyroid volume correlated significantly with age, weight, BMI, waist circumference, systolic blood pressure, 120-min postprandial glucose and HDL level.

CONCLUSIONS

PCOS alone was not associated with thyroid disease in our population. However, MS and some of its components appear to be related to thyroid volume, function, and antithyroid antibody levels.

Diabetes and thyroid cancer risk in the National Institutes of Health-AARP Diet and Health Study

BACKGROUND

We hypothesized that diabetes may play a role in thyroid cancer risk due to the parallel secular rise in diabetes prevalence and morbidity in the United States, the higher prevalence of thyroid disorders among diabetics compared with the general population, and the potential roles of metabolic syndrome, obesity, and diabetes as precipitating factors in cancer development.

METHODS

We assessed the association between self-reported diabetes and the risk of differentiated thyroid cancer in the NIH-AARP Diet and Health Study, a prospective cohort of 200,556 women and 295,992 men, 50-71 years of age, in 1995-1996. Diabetes status and information on potential confounders was ascertained using a self-administered questionnaire. During an average of 10 years of follow-up, 585 thyroid cancer cases were identified. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for thyroid cancer and thyroid cancer subtypes in men and women according to diabetes status.

RESULTS

Nine percent of the total baseline cohort reported a history of diabetes (7% of women, 10% of men). A nonsignificant 25% increase in thyroid cancer risk (HR = 1.25; 95% CI: 0.95-1.64) was associated with diabetes. Among women, the risk was significantly increased (HR = 1.46, 95% CI: 1.01-2.10). The risk was not elevated among men (HR = 1.04, 95% CI: 0.69-1.58). In this cohort, diabetic women with differentiated thyroid cancer were at somewhat higher risk of follicular thyroid cancer (HR = 1.92; 95% CI: 0.86-4.27) than papillary thyroid cancer (HR = 1.25; 95% CI: 0.80-1.97).

CONCLUSION

This study lends support to the hypothesis that diabetes increases the risk of differentiated thyroid cancer.

Insulin receptor and cancer

The widespread epidemic of obesity and type 2 diabetes has raised concern for the impact of these disorders as risk factors for cancer and has renewed the interest for studies regarding the involvement of hyperinsulinemia and insulin receptor (IR) in cancer progression. Overexpression of IR in cancer cells may explain their increased sensitivity to hyperinsulinemia. Moreover, IR isoform A (IR-A) together with autocrine production of its ligand IGF2 is emerging as an important mechanism of normal and cancer stem cell expansion and is a feature of several malignancies. De novo activation of the IR-A/IGF2 autocrine loop also represents a mechanism of resistance to anticancer therapies. Increasing knowledge of the IR role in cancer has important implications for cancer prevention, which should include control of insulin resistance and hyperinsulinemia in the population and meticulous evaluation of new antidiabetic drugs for their metabolic:mitogenic ratio. We are now aware that several anticancer treatments may induce or worsen insulin resistance that may limit therapy efficacy. Future anticancer therapies need to target the IR-A pathway in order to inhibit the tumor promoting effect of IR without impairing the metabolic effect of insulin.

Insulin receptor isoforms and insulin-like growth factor receptor in human follicular cell precursors from papillary thyroid cancer and normal thyroid

CONTEXT

Factors involved in the biology of normal and cancer stem/precursor cells from the thyroid are unknown. Thyroid cancer cells are responsive to insulin and IGF-I and IGF-II and often overexpress the insulin receptor (IR) and the IGF-I receptor (IGF-IR).

OBJECTIVE

We investigated the role of IR isoforms (IR-A and IR-B), IGF-IR, and their ligands in thyroid follicular cell precursors both normal and malignant.

DESIGN

We established cultures of follicular cell precursors as thyrospheres from three papillary thyroid cancers and the corresponding nonaffected tissues. The expression of IR, IGF-IR, and their ligands was evaluated by quantitative RT-PCR and, in one case, also by Western blot. The effects of insulin and IGFs on thyrosphere growth and self-renewal were evaluated.

RESULTS

Thyrospheres were characterized by the expression of stem cell markers and low/absent thyroid specific markers. Thyrospheres from normal tissue, but not from cancer tissue, could be induced to differentiate. Both IR isoforms, IGF-IR, IGF-I and IGF-II, were expressed at high levels in thyrospheres and markedly decreased in differentiating cells. IR-A was the predominant isoform in thyrospheres, especially from cancer, while IR-B was predominant in differentiating cells. Cancer thyrosphere growth was stimulated by insulin and IGFs.

CONCLUSIONS

Our data suggest that IR isoforms and IGF-IR play a role in the biology of follicular thyroid precursors. Cell differentiation is associated with marked changes in the expression of these receptors and cognate ligands. These data may provide insight for future differentiation therapies in thyroid cancer.

Insulin resistance in nodular thyroid disease

BACKGROUND

Insulin had been shown to have a mitogenic effect on thyroid cell cultures. The aim of this study was to investigate insulin resistance in patients with euthyroid nodular goiter.

METHODS

Sixty-three patients with nodular thyroid disease and 83 healthy controls were included in the study. Both the patient and the control group were euthyroid, euglycemic and normotensive. None of the study subjects had risk factors for insulin resistance. All the study subjects were evaluated by serum insulin levels and biochemical parameters and thyroid ultrasound. All subjects with thyroid nodules greater than 1cm (n = 36) were offered to undergo thyroid fine needle aspiration biopsy.

RESULTS

The two groups were similar with respect to age, gender, BMI, waist circumference, serum lipid levels, serum fT3, fT4 and TSH levels. But HOMA was found to be significantly higher in the patient group (p: 0.007) and thyroid volume was significantly greater in the patient group (p = 0.03). In the patient group there was a significant correlation between HOMA and nodule volume (p < 0.001) while there was not a significant correlation between HOMA and number of thyroid nodules. Thyroid cancer was diagnosed in 3 of the 36 patients (8.33 %).

CONCLUSIONS

Insulin resistance may induce increased thyroid proliferation and nodule volume and nodule formation. Therefore, insulin resistance may be a risk factor for euthyoid nodular goiter.

Compensatory insulin receptor (IR) activation on inhibition of insulin-like growth factor-1 receptor (IGF-1R): rationale for cotargeting IGF-1R and IR in cancer

Insulin-like growth factor-1 receptor (IGF-1R) is a receptor tyrosine kinase (RTK) and critical activator of the phosphatidylinositol 3-kinase-AKT pathway. IGF-1R is required for oncogenic transformation and tumorigenesis. These observations have spurred anticancer drug discovery and development efforts for both biological and small-molecule IGF-1R inhibitors. The ability for one RTK to compensate for another to maintain tumor cell viability is emerging as a common resistance mechanism to antitumor agents targeting individual RTKs. As IGF-1R is structurally and functionally related to the insulin receptor (IR), we asked whether IR is tumorigenic and whether IR-AKT signaling contributes to resistance to IGF-1R inhibition. Both IGF-1R and IR(A) are tumorigenic in a mouse mammary tumor model. In human tumor cells coexpressing IGF-1R and IR, bidirectional cross talk was observed following either knockdown of IR expression or treatment with a selective anti-IGF-1R antibody, MAB391. MAB391 treatment resulted in a compensatory increase in phospho-IR, which was associated with resistance to inhibition of IRS1 and AKT. In contrast, treatment with OSI-906, a small-molecule dual inhibitor of IGF-1R/IR, resulted in enhanced reduction in phospho-IRS1/phospho-AKT relative to MAB391. Insulin or IGF-2 activated the IR-AKT pathway and decreased sensitivity to MAB391 but not to OSI-906. In tumor cells with an autocrine IGF-2 loop, both OSI-906 and an anti-IGF-2 antibody reduced phospho-IR/phospho-AKT, whereas MAB391 was ineffective. Finally, OSI-906 showed superior efficacy compared with MAB391 in human tumor xenograft models in which both IGF-1R and IR were phosphorylated. Collectively, these data indicate that cotargeting IGF-1R and IR may provide superior antitumor efficacy compared with targeting IGF-1R alone.

Silencing of the insulin receptor isoform A favors formation of type 1 insulin-like growth factor receptor (IGF-IR) homodimers and enhances ligand-induced IGF-IR activation and viability of human colon carcinoma cells

Insulin receptor (IR) overexpression is common in cancers, with expression of the A isoform (IR-A, exon 11-) predominating over the B isoform. The IR-A signals a proliferative, antiapoptotic response to IGF-II, which itself can be secreted by tumors to establish an autocrine proliferative loop. Therefore, IGF-II signaling via the IR-A could mediate resistance to type 1 IGF receptor (IGF-IR) inhibitory drugs that are currently in development. This study addressed the role of the IR-A, using a small interfering RNA-based approach in SW480 human colon adenocarcinoma cells that coexpress the IGF-IR. Clonogenic survival was inhibited by depletion of the IGF-IR but not the IR-A, and dual receptor depletion had no greater effect than IGF-IR knockdown alone, suggesting that the IR-A could not compensate for IGF-IR loss. IGF-IR knockdown also resulted in a decrease in viability, whereas IR-A depletion resulted in increased viability. Consistent with this, upon IR-A depletion, we found a concomitant enhancement of IGF-IR activation by IGF-I and IGF-II, reduced formation of IGF-IR:IR-A hybrid receptors and increased IGF-IR homodimer formation. Together, these results suggest that IGF bioactivity is mediated more effectively by the IGF-IR than by the IR-A or receptor hybrids and that signaling via the IGF-IR is dominant to the IR-A in colon cancer cells that express both receptors.

Latin American Thyroid Society recommendations for the management of thyroid nodules

Several guidelines on diagnosis and treatment of thyroid nodules and cancer have recently been published. However, recommended practices are not always appropriate to different settings or countries. The aim of this consensus was to develop Clinical Guidelines for evaluation and management of patients with thyroid nodules applicable to Latin American countries. The panel was composed by 13 members of the Latin American Thyroid Society involved with research and management of thyroid nodules and cancer from different medical centers in Latin America. The consensus was produced based on the expert opinion of the panel with use of principles of evidence-based medicine. Following a group meeting, a first draft based on the expert opinion of the panel was elaborated and later circulated among panel members for further revision. After revision, this document was submitted to all LATS members for commentaries and considerations and finally revised and refined by the authors. The final recommendations represent state of the art on management of thyroid nodules applied to all Latin American countries.

Insulin receptor isoforms and insulin receptor/insulin-like growth factor receptor hybrids in physiology and disease

In mammals, the insulin receptor (IR) gene has acquired an additional exon, exon 11. This exon may be skipped in a developmental and tissue-specific manner. The IR, therefore, occurs in two isoforms (exon 11 minus IR-A and exon 11 plus IR-B). The most relevant functional difference between these two isoforms is the high affinity of IR-A for IGF-II. IR-A is predominantly expressed during prenatal life. It enhances the effects of IGF-II during embryogenesis and fetal development. It is also significantly expressed in adult tissues, especially in the brain. Conversely, IR-B is predominantly expressed in adult, well-differentiated tissues, including the liver, where it enhances the metabolic effects of insulin. Dysregulation of IR splicing in insulin target tissues may occur in patients with insulin resistance; however, its role in type 2 diabetes is unclear. IR-A is often aberrantly expressed in cancer cells, thus increasing their responsiveness to IGF-II and to insulin and explaining the cancer-promoting effect of hyperinsulinemia observed in obese and type 2 diabetic patients. Aberrant IR-A expression may favor cancer resistance to both conventional and targeted therapies by a variety of mechanisms. Finally, IR isoforms form heterodimers, IR-A/IR-B, and hybrid IR/IGF-IR receptors (HR-A and HR-B). The functional characteristics of such hybrid receptors and their role in physiology, in diabetes, and in malignant cells are not yet fully understood. These receptors seem to enhance cell responsiveness to IGFs.

Phosphorylated Insulin Like Growth Factor-I Receptor Expression and Its Clinico-Pathological Significance in Histologic Subtypes of Human Thyroid Cancer

Overexpression of insulin-like growth factor-I receptor (IGF-IR) is seen in a multitude of human thyroid cancers and correlates with poor prognosis. However, recent studies suggest that low phospho-IGF-IR (pIGF-IR) expression rather than its overexpression may be an indicator of poorly differentiated disease. No previous study has evaluated the expression of pIGF-IR to determine if activation or loss of expression of this receptor is associated with thyroid tumor progression. Accordingly, a quantitative immunohistochemical (IHC) method was used to evaluate the clinico-pathological significance of pIGF-IR expression in archival samples of human thyroid carcinomas. Quantitative analysis of pIGF-IR levels revealed a significant difference in the median index of pIGF-IR between different histological subtypes of thyroid cancer ( P < 0.001). Specifically, the median pIGF-IR index of differentiated thyroid cancers was significantly higher than the median index of other poorly differentiated thyroid cancer ( P < 0.001). This was further confirmed in individual tumor sections of thyroid carcinoma where anaplastic and differentiated components co-existed. No significant difference was noted in the pIGF-IR index of tumors grouped by size or stage but a trend towards lower mean pIGF-IR index was noted in older patients. Our data indicates that pIGF-IR is upregulated in a majority of follicular thyroid carcinomas, suggesting it may be a potential target for therapy for patients with this disease. In addition, since low pIGF-IR expression was found to correlate with aggressive human thyroid carcinoma, it also suggests that IGF-IR may not be needed for progression of anaplastic thyroid carcinoma possibly because other cell signaling pathways are activated, obviating the need for IGF-IR signaling. However, more mechanistic studies would be necessary to substantiate the possibility that pIGF-IR may be important for differentiation of thyroid tissues and is lost with disease progression.

Risk factors for thyroid cancer: an epidemiological review focused on nutritional factors

OBJECTIVES

The present review summarizes epidemiological evidence on risk factors for thyroid cancer (TC), in particular, nutritional factors.

METHODS

Searches of articles on the issue were conducted using MEDLINE.

RESULTS

Exposure to ionizing radiation, particularly during childhood, is the best-established risk factor for TC. There is also a strong association with history of benign nodules/adenoma or goiter. Iodine deficiency may induce an increasing incidence of benign thyroid conditions, but very high iodine intake also affects thyroid function and, possibly, TC risk. Among dietary factors, fish-the major natural source of iodine in human diet-is not consistently related to TC risk. High intake of cruciferous vegetables shows a weak inverse association with TC. Among other food groups, vegetables other than cruciferous are the only food group showing a favorable effect on TC, with an approximate 20% reduction in risk for subjects with the highest consumption. No effect on TC risk of alcohol, coffee, or other food-groups/nutrients emerged. Height and weight at diagnosis show a moderate positive association with TC risk.

CONCLUSION

At present, the only recognized measures for reducing TC risk is to avoid ionizing radiation and iodine deficiency, particularly in childhood and young women, and to increase vegetable consumption.

Introducing the thyroid gland as another victim of the insulin resistance syndrome

BACKGROUND

Insulin is a thyroid growth factor that stimulates proliferation of thyroid cells in culture. In order to evaluate the effects of insulin resistance (IR) on the thyroid gland, we developed a prospective study in euthyroid women.

METHODS

One hundred eleven women (mean age 32.2 +/- 7 years) were evaluated by a thyroid ultrasound (US) and basal and postprandial serum insulin. Subjects were divided into four groups as follows: G1 (n = 42), subjects with IR and obesity; G2 (n = 21), subjects with obesity without IR; G3 (n = 17), subjects with IR and normal weight; and G4 (n = 31) control group (without IR and obesity).

RESULTS

The thyroid volume (TV), measured by US, showed the following values: G1, 17 +/- 3 mL; G2, 13.8 +/- 2.8 mL; G3, 16.2 +/- 2.1 mL; and G4,12.1 +/- 2.4 mL. There was no significant difference in TV between G1 and G3, but differences between G1 and G2, and between G3 and G4 were significant at p < 0.05. The percentage of nodular thyroid glands observed by US in each group was as follows: G1, 50%; G2, 23.8%; G3, 61%; G4, 16.1%. Again, the differences between G1 and G2 and between G3 and G4 were statistically significant (p < 0.005 and p < 0.001, respectively, for each comparison).

CONCLUSIONS

It is concluded that the higher circulating levels of insulin cause increased thyroid proliferation. The clinical manifestations are the larger thyroid volume and the formation of nodules. Thus, the thyroid gland appears to be another victim of the insulin resistance syndrome.

Acromegaly: re-thinking the cancer risk

Acromegaly is characterized by sustained elevation of circulating growth hormone (GH) and insulin-like growth factor I (IGF-I), and is clearly associated with increased morbidity and overall mortality mainly due to cardiovascular, metabolic, and respiratory diseases. Although cancer-related mortality varies widely amongst retroperspective studies, it appears to be consistently elevated mainly in patients with uncontrolled disease. We review individual tumor types including neoplasms of the colon, breast, prostate, and thyroid where in vitro, animal studies, and studies in non-acromegalic cancer patients have established a role for the GH/IGF-I axis in tumor progression and possibly initiation. We highlight deficiencies in data in acromegalic patients where the evidence is less convincing. Instead, we explore the hypothesis that acromegaly, independent of hormone secretion, is a disease that heralds genetic and/or epigenetic alterations predisposing to cancer risk elsewhere.

The role of insulin receptors and IGF-I receptors in cancer and other diseases

There is evidence, both in vitro and in vivo, that receptor tyrosine kinases play a key role in the formation and progression of human cancer. In particular, the insulin-like growth factor receptor (IGF-IR), a tyrosine kinase receptor for IGF-I and IGF-II, has been well documented in cell culture, animal studies, and humans to play a role in malignant transformation, progression, protection from apoptosis, and metastasis. In addition, the hormone insulin (which is very closely related to the IGFs) and its tyrosine kinase receptor (the IR, which is very closely related to the IGR-IR) have been documented both in vitro and in vivo to play a key role in cancer biology. Indeed, several epidemiological studies have shown that insulin resistance status, characterized by hyperinsulinaemia, is associated with an increased risk for a number of malignancies, including carcinomas of the breast, prostate, colon and kidney. Recent data have elucidated some molecular mechanisms by which IR is involved in cancer. IR is over-expressed in several human malignancies. Interestingly, one of the two IR isoform (IR-A) is especially over-expressed in cancer. IR-A is the IR foetal isoform and has the peculiar characteristic to bind not only insulin but also IGF-II. In addition, the IR contributes to formation of hybrid receptors with the IGF-IR (HR). By binding to hybrid receptors, insulin may stimulate specific IGF-IR signalling pathways. Over-expression of IR-A is, therefore, a major mechanism of IGF system over-activation in cancer. In this respect, IR-A isoform and hybrid receptors should be regarded as potential molecular targets, in addition to IGF-IR, for novel anti-cancer therapy. These findings may have important implications for both the prevention and treatment of common human malignancies. They underline the concept that hyperinsulinaemia, associated with insulin resistance and obesity, should be treated by changes in life style and/or pharmacological approaches to avoid an increased risk for cancer. Moreover, native insulin and insulin analogue administration should be carefully evaluated in terms of the possible increase in cancer risk.

Cell lineage-specific signaling of insulin and insulin-like growth factor I in rabbit blastocysts

The insulin/IGF system plays a critical role in embryo growth and development. We have investigated the expression of insulin receptor (IR) and IGF-I receptor (IGF-IR) and the activation of their downstream pathways in rabbit 6-d-old blastocysts. IR was expressed in embryoblast (Em, inner cell mass) and trophoblast (Tr) cells, whereas IGF-IR was localized mainly in Em. Isoform A (IR-A) represents the main insulin isoform in blastocysts and was found in Em and Tr cells. IR-B was detectable only in Tr. IR/IGF-IR signaling pathways were analyzed after stimulation with insulin (17 nm) or IGF-I (1.3 nm) in cultured blastocysts. Insulin stimulated Erk1/2 in Em and Tr and Akt in Tr but not in Em. IGF-I activated both kinases exclusively in Em. The target genes c-fos (for MAPK kinase-1/Erk signaling) and phosphoenolpyruvate carboxykinase (PEPCK, for PI3K/Akt signaling) were also specifically regulated. Insulin down-regulated PEPCK RNA amounts in Tr by activation of the phosphatidylinositol 3-kinase/Akt pathway. Expression of c-fos by insulin and IGF-I was different with respect to time and fortitude of expression, mirroring again the specific IR and IGF-IR expression patterns in Em and Tr. Taken together, we show that IGF-I acts primarily mitogenic, an effect that is cell lineage-specifically restricted to the Em. By contrast, insulin is the growth factor of the Tr stimulating mitogenesis and down-regulating metabolic responses. As soon as blastocyst differentiation in Em and Tr has been accomplished, insulin and IGF-I signaling is different in both cell lineages, implying a different developmental impact of both growth factors.

Growth-inhibitory effects of human anti-insulin-like growth factor-I receptor antibody (A12) in an orthotopic nude mouse model of anaplastic thyroid carcinoma

PURPOSE

The insulin-like growth factor-I receptor (IGF-IR) and its ligands have been implicated in the pathogenesis and progression of various cancers, including those arising in the thyroid gland. We therefore evaluated whether the IGF-IR could serve as a potential target for therapy of anaplastic thyroid carcinoma (ATC).

EXPERIMENTAL DESIGN

The expression and activation of the IGF-IR and some of its downstream signaling pathway components were evaluated in both human thyroid cancer specimens and thyroid cancer cell lines. The therapeutic potential of a humanized monoclonal antibody (A12) directed against IGF-IR was assessed in vitro and in vivo in an orthotopic model of ATC. Tumor volume and overall survival time were analyzed to evaluate the efficacy of A12 in vivo.

RESULTS

IGF-IR was overexpressed in 94% of the thyroid cancers. Blockade of IGF-IR with A12 was effective in attenuating IGF-IR signaling both in vitro and in vivo. However, the inhibitory effects of A12 on cell proliferation were cell line dependent, as those ATC cell lines that had detectable levels of pIGF-IR were more sensitive to A12 treatment. A12 was equally effective in vivo, where it brought approximately 57% (P = 0.041) inhibition in tumor volume. The concomitant use of A12 and irinotecan produced additive effects and resulted in a 93% (P < 0.001) reduction in tumor volume. Blocking IGF-IR blocked Akt phosphorylation and decreased proliferation and microvessel density but increased apoptosis within the tumor xenografts. Our results also highlighted a previously undefined IGF-IR-mediated antiangiogenic effect on tumor-associated endothelium in thyroid cancers.

CONCLUSION

Blocking the IGF-IR with A12 seems to be a potential avenue for treating patients with ATC by its direct antitumor effects and its effects on the tumor vasculature.

Functional responses and in vivo anti-tumour activity of h7C10: A humanised monoclonal antibody with neutralising activity against the insulin-like growth factor-1 (IGF-1) receptor and insulin/IGF-1 hybrid receptors

A novel humanised monoclonal antibody (Mab, h7C10) was raised against the human insulin-like growth factor-1 receptor (IGF-1R); it exhibited potent inhibition of tumour growth in animal models. Further evaluation of its inhibitory activity at hybrid receptors (Hybrid-Rs) composed of the association between IGF-1R and insulin receptor (IR) was performed. Selective, potent and efficacious inhibition of [(125)I]IGF-1 binding as well as IGF-1- and IGF-2-mediated receptor phosphorylation was demonstrated at both IGF-1R and Hybrid-Rs, without activity at IR. Ligand-independent down-regulation of both IGF-1R and Hybrid-Rs was obtained upon long-term association with h7C10. In vivo evaluation was performed in a MDA-MB-231 xenograft mouse model, showing a 14-fold higher level of Hybrid-Rs as compared to IGF-1R. A more potent anti-tumoural response was obtained for h7C10 as compared to Mabs targeting solely IGF-1R or Hybrid-Rs. The herewith described neutralising properties of h7C10 as potent inhibitor of both IGF-1R and Hybrid-Rs are likely to participate in its anti-tumoural activities and maybe of interest for therapeutic applications.

The use of bioluminescence resonance energy transfer for the study of therapeutic targets: application to tyrosine kinase receptors

During recent years, the bioluminescence resonance energy transfer (BRET) methodology has emerged as a powerful technique for the study of protein-protein interactions. This review focuses on recent work demonstrating the power of BRET for the study of tyrosine kinase receptors, using insulin and IGF-1 receptors as models. The authors show that BRET can be used to monitor ligand-induced conformational changes within homodimeric insulin and IGF-1 receptors, as well as heterodimeric insulin/IGF-1 hybrid receptors. BRET can also be used to study, in real time and in living cells, the interaction of tyrosine kinase receptors with cellular partners negatively or positively involved in the regulation of intracellular signalling (protein tyrosine phosphatases, molecular adaptors). In addition, BRET can be used to develop high-throughput screening assays for the search of molecules with therapeutic interest and could, therefore, constitute a valuable tool for laboratories involved in drug discovery.

Anaplastic Thyroid Carcinoma: Expression Profile of Targets for Therapy Offers New Insights for Disease Treatment

BACKGROUND

Anaplastic thyroid cancer is an endocrine malignancy. Its rare and rapidly lethal disease course has made it challenging to study. Little is known regarding the expression by anaplastic tumors of molecular targets for new human anticancer agents that have been studied in the preclinical or clinical setting. The objective of this work was to evaluate the expression profile of anaplastic thyroid tumors for molecular targets for treatment.

METHODS

Of the 94 cases of anaplastic thyroid cancers diagnosed and treated in British Columbia, Canada over a 20-year period (1984-2004), 32 cases (34%) had adequate archival tissue available for evaluation. A tissue microarray was constructed from these anaplastic thyroid tumors and immunohistochemistry was utilized to evaluate expression of 31 molecular markers. The markers evaluated were: epidermal growth factor receptor (EGFR), HER2, HER3, HER4, ER, PR, uPA-R, clusterin, E-cadherin, beta-catenin, AMF-R, c-kit, VEGF, ILK, aurora A, aurora B, aurora C, RET, CA-IX, IGF1-R, p53, MDM2, p21, Bcl-2, cyclin D1, cyclin E, p27, calcitonin, MIB-1, TTF-1, and thyroglobulin.

RESULTS

A single tumor with strong calcitonin expression was identified as a poorly differentiated medullary carcinoma and excluded from the study cohort. The mean age of the anaplastic cohort was 66 years; 16 patients (51%) were females, and the median patient survival was 23 weeks. A wide range in molecular marker expression was observed by the anaplastic thyroid cancer tumors (0-100%). The therapeutic targets most frequently and most strongly overexpressed by the anaplastic tumors were: beta-catenin (41%), aurora A (41%), cyclin E (67%), cyclin D1 (77%), and EGFR (84%).

CONCLUSIONS

Anaplastic thyroid tumors exhibit considerable derangement of their cell cycle and multiple signal transduction pathways that leads to uncontrolled cellular proliferation and the development of genomic instability. This report is the first to comprehensively evaluate a panel of molecular targets for therapy of anaplastic thyroid cancer and supports the development of clinical trials with agents such as cetuximab, small-molecule tyrosine kinase inhibitors, and aurora kinase inhibitors, which may offer new hope for individuals diagnosed with this fatal thyroid malignancy.