Are the insulin-like growth factors relevant to cancer?

Targeting the IGF-1R in prostate and colorectal cancer: reasons behind trial failure and future directions

IGF-1Rs enact a significant part in cancer growth and its progress. IGF-1R inhibitors were encouraged in the early trials, but the patients did not benefit due to the unavailability of predictive biomarkers and IGF-1R system complexity. However, the linkage between IGF-1R and cancer was reported three decades ago. This review will shed light on the IGF-1R system, targeting IGF-1R through monoclonal antibodies, reasons behind IGF-1R trial failure and future directions. This study presented that targeting IGF-1R through monoclonal antibodies is still effective in cancer treatment, and there is a need to look for future directions. Cancer patients may benefit from using mAbs that target existing and new cancer targets, evidenced by promising results. It is also essential that the academician, trial experts and pharmaceutical companies play their role in finding a treatment for this deadly disease.

No evidence of increased risk of malignancies in patients with diabetes treated with insulin detemir: a meta-analysis

AIMS/HYPOTHESIS

Recent epidemiological studies suggest that treatment with insulin glargine (A21Gly,B31Arg,B32Arg human insulin) may promote cancer growth. The present meta-analysis was performed to assess the risk of cancer during treatment with insulin detemir (B29Lys(epsilon-tetradecanoyl),desB30 human insulin), another long-acting insulin analogue.

METHODS

This meta-analysis was performed in a population of 8,693 patients with type 1 or type 2 diabetes, who were included in Novo Nordisk-sponsored, randomised and controlled diabetes trials of at least 12 weeks in duration that compared insulin detemir with NPH insulin or insulin glargine. In a blinded manner, the adverse events with suspected treatment-emergent malignant tumours were obtained from these studies under three system-organ classes: 'Neoplasms benign, malignant and unspecified (including cysts and polyps)', 'Neoplasm' and 'Surgical and medical procedures'. Conditional ORs were estimated applying both the Mantel-Haenzel and Peto methods to ensure robustness of results.

RESULTS

Separate analyses were performed for trials comparing insulin detemir with NPH insulin and insulin detemir with insulin glargine. In the first analysis, 16 studies were included with a total of 3,983 patients treated with insulin detemir and 2,661 patients treated with NPH insulin. In the second analysis, five studies were included with a total of 1,219 patients treated with insulin detemir and 830 patients treated with insulin glargine. The estimated OR for a cancer diagnosis between NPH insulin and insulin detemir was statistically significantly >1, with the ratio favouring insulin detemir. There was a more than twofold higher cancer occurrence in the NPH insulin-treated population. For the insulin detemir comparison with insulin glargine, there was a non-significant difference in ORs in favour of insulin detemir.

CONCLUSIONS/INTERPRETATION

In these randomised controlled diabetes trials, patients treated with insulin detemir had a lower or similar occurrence of a cancer diagnosis compared with patients treated with NPH insulin or insulin glargine, respectively.

Energy balance, physical activity, and cancer risk

This chapter posits that cancer is a complex and multifactorial process as demonstrated by the expression and production of key endocrine and steroid hormones that intermesh with lifestyle factors (physical activity, body size, and diet) in combination to heighten cancer risk. Excess weight has been associated with increased mortality from all cancers combined and for cancers of several specific sites. The prevalence of obesity has reached epidemic levels in many parts of the world; more than 1 billion adults are overweight with a body mass index (BMI) exceeding 25. Overweight and obesity are clinically defined indicators of a disease process characterized by the accumulation of body fat due to an excess of energy intake (nutritional intake) relative to energy expenditure (physical activity). When energy intake exceeds energy expenditure over a prolonged period of time, the result is a positive energy balance (PEB), which leads to the development of obesity. This physical state is ideal for intervention and can be modulated by changes in energy intake, expenditure, or both. Nutritional intake is a modifiable factor in the energy balance-cancer linkage primarily tested by caloric restriction studies in animals and the effect of energy availability. Restriction of calories by 10 to 40% has been shown to decrease cell proliferation, increasing apoptosis through anti-angiogenic processes. The potent anticancer effect of caloric restriction is clear, but caloric restriction alone is not generally considered to be a feasible strategy for cancer prevention in humans. Identification and development of preventive strategies that "mimic" the anticancer effects of low energy intake are desirable. The independent effect of energy intake on cancer risk has been difficult to estimate because body size and physical activity are strong determinants of total energy expenditure. The mechanisms that account for the inhibitory effects of physical activity on the carcinogenic process are reduction in fat stores, activity related changes in sex-hormone levels, altered immune function, effects in insulin and insulin-like growth factors, reduced free radical generation, and direct effect on the tumor. Epidemiologic evidence posits that the cascade of actions linking overweight and obesity to carcinogenesis are triggered by the endocrine and metabolic system. Perturbations to these systems result in the alterations in the levels of bioavailable growth factors, steroid hormones, and inflammatory markers. Elevated serum concentrations of insulin lead to a state of hyperinsulinemia. This physiological state causes a reduction in insulin-like growth factor-binding proteins and promotes the synthesis and biological activity of insulin-like growth factor (IGF)-I, which regulates cellular growth in response to available energy and nutrients from diet and body reserves. In vitro studies have clearly established that both insulin and IGF-I act as growth factors that promote cell proliferation and inhibit apoptosis. Insulin also affects on the synthesis and biological availability of the male and female sex steroids, including androgens, progesterone, and estrogens. Experimental and clinical evidence also indicates a central role of estrogens and progesterone in regulating cellular differentiation, proliferation, and apoptosis induction. Hyperinsulinemia is also associated with alterations in molecular systems such as endogenous hormones and adipokines that regulate inflammatory responses. Obesity-related dysregulation of adipokines has the ability to contribute to tumorigenesis and tumor invasion via metastatic potential. Given the substantial level of weight gain in industrialized countries in the last two decades, there is great interest in understanding all of the mechanisms by which obesity contributes to the carcinogenic process. Continued focus must be directed to understanding the various relationships between specific nutrients and dietary components and cancer cause and prevention. A reductionist approach is not sufficient for the basic biological mechanisms underlying the effect of diet and physical activity on cancer. The joint association between energy balance and cancer risk are hypothesized to share the same underlying mechanisms, the amplification of chemical mediators that modulate cancer risk depending on the responsiveness to those hormones to the target tissue of interest. Disentangling the connection between obesity, the insulin-IGF axis, endogenous hormones, inflammatory markers, and their molecular interaction is vital.

C/EBPbeta regulates body composition, energy balance-related hormones and tumor growth

The prevalence of obesity, an established epidemiologic risk factor for many chronic diseases including cancer, has been steadily increasing in the US over several decades. The mechanisms used to regulate energy balance and adiposity and the relationship of these factors to cancer are not completely understood. Here we have used knockout mice to examine the roles of the transcription factors CCAAT/enhancer-binding protein (C/EBP) beta and C/EBPdelta in regulating body composition and systemic levels of hormones such as insulin-like growth factor-1 (IGF-1), leptin and insulin that mediate energy balance. Dual-energy X-ray absorptiometry showed that C/EBPbeta, either directly or indirectly, modulated body weight, fat content and bone density in both males and females, while the effect of C/EBPdelta was minor and only affected adiposity and body weight in female animals. Levels of IGF-1, leptin and insulin in the serum were decreased in both male and female C/EBPbeta(-/-) mice, and C/EBPbeta was associated with their promoters in vivo. Moreover, colon adenocarcinoma cells displayed reduced tumorigenic potential when transplanted into C/EBPbeta-deficient animals, especially males. Thus, C/EBPbeta contributes to endocrine expression of IGF-1, leptin and insulin, which modulate energy balance and can contribute to cancer progression by creating a favorable environment for tumor cell proliferation and survival.

Emerging drugs for mesothelioma

Malignant mesothelioma is an aggressive, but relatively rare, malignancy, affecting the pleura and peritoneum. The prognosis for malignant pleural mesothelioma (MPM) is poor, with median survival in the range of 8-14 months, depending on stage and presentation of disease. Long-term results of available treatments are disappointing not only in terms of prognosis, but also of local control of the disease. Therefore, relief of symptoms and improvement of quality of life parameters are the short-term goals of therapy. In advanced disease not amenable to any local approach, such as surgery, combination chemotherapy represents the current standard of care. At present, the regimen of cisplatin/pemetrexed is the medical treatment of choice. This review summarizes standard chemotherapy options and focuses on the molecular basis of the newest biologically targeted therapies to be implemented in the near future, in the management of MPM.

Effects of insulin-like growth factor-1 receptor inhibition in mesothelioma. Thoracic Surgery Directors Association Resident Research Award

BACKGROUND

Malignant mesothelioma is a devastating disease with a poor prognosis. Recent data have shown that insulin-like growth factor-1 receptor (IGF-1R) may play a role in oncogenic signaling. Our aim was to evaluate the effect of a novel IGF-1R inhibitor, NVP-AEW541, on cell growth and IGF associated pathways.

METHODS

Malignant mesothelioma cell lines, H2373 and H2461, previously shown to activate the IGF pathway were grown in culture. The adherent cells, initially plated at 5 x 10(5) cells/plate, were treated for 72 hours, in triplicate, with varying concentration of NVP-AEW541 (0, 1, 5, 10, 20, and 50 microM). Viable cells were counted every 24 hours. Additionally, separate cultures in serum-free medium were treated with NVP-AEW541, then stimulated with IGF and lysates collected for immunoblot analysis.

RESULTS

In both cell lines, 0, 1, 5, and 10 microM showed an inhibitory or static effect, while 20 and 50 microM were cidal. Immunoblot analysis demonstrated that phosphorylation of IGF-1R was inhibited by NVP-AEW541 at higher concentration. Phosphorylation of mitogen-activated protein kinase and Akt, downstream IGF pathway mediators, were also shown to be repressed by drug treatment.

CONCLUSIONS

NVP-AEW541 has a concentration-dependent inhibitory effect on mesothelioma cells in culture. NVP-AEW541 acts by inhibition of IGF-1R phosphorylation. Inhibition effects phosphorylation of downstream mediators in a dose-dependent fashion. Inhibition of the IGF pathway decreases viability of mesothelioma cell culture. Further evaluation of NVP-AEW541, and other selective IGF-1R inhibitors, may play an important role in multimodal treatment of malignant mesothelioma.

trans-3,4,5'-Trihydroxystibene inhibits hypoxia-inducible factor 1alpha and vascular endothelial growth factor expression in human ovarian cancer cells

trans-3,4,5'-Trihydroxystibene (resveratrol) is a natural product commonly found in the human diet and has been shown recently to have anticancer effects on various human cancer cells. However, the molecular basis for its anticancer action remains to be elucidated. In this study, we investigated the effect of resveratrol on hypoxia-inducible factor 1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) expression in human ovarian cancer cells A2780/CP70 and OVCAR-3. We found that although resveratrol did not affect HIF-1alpha mRNA levels, it did dramatically inhibit both basal-level and growth factor-induced HIF-1alpha protein expression in the cells. Resveratrol also greatly inhibited VEGF expression. Mechanistically, we demonstrated that resveratrol inhibited HIF-1alpha and VEGF expression through multiple mechanisms. First, resveratrol inhibited AKT and mitogen-activated protein kinase activation, which played a partial role in the down-regulation of HIF-1alpha expression. Second, resveratrol inhibited insulin-like growth factor 1-induced HIF-1alpha expression through the inhibition of protein translational regulators, including M(r) 70,000 ribosomal protein S6 kinase 1, S6 ribosomal protein, eukaryotic initiation factor 4E-binding protein 1, and eukaryotic initiation factor 4E. Finally, we showed that resveratrol substantially induced HIF-1alpha protein degradation through the proteasome pathway. Our data suggested that resveratrol may inhibit human ovarian cancer progression and angiogenesis by inhibiting HIF-1alpha and VEGF expression and thus provide a novel potential mechanism for the anticancer action of resveratrol.

Critical prosurvival roles for C/EBP beta and insulin-like growth factor I in macrophage tumor cells

One of the hallmarks of leukemic cells is their ability to proliferate and survive in the absence of exogenous growth factors (GFs). However, the molecular mechanisms used by myeloid tumor cells to escape apoptosis are not fully understood. Here we report that Myc/Raf-transformed macrophages require the transcription factor C/EBP beta to prevent cell death. In contrast to wild-type cells, C/EBP beta(-/-) macrophages were completely dependent on macrophage colony-stimulating factor or granulocyte-macrophage colony-stimulating factor for survival and displayed impaired tumorigenicity in vivo. Microarray analysis revealed that C/EBP beta-deficient cells expressed significantly reduced levels of the prosurvival factor insulin-like growth factor I (IGF-I). Overexpression of C/EBP beta stimulated transcription from the IGF-I promoter, indicating that IGF-I is a direct transcriptional target of C/EBP beta. Serological neutralization of IGF-I in C/EBP beta(+/+) tumor cell cultures induced apoptosis, showing that IGF-I functions as an autocrine survival factor in these cells. Macrophage tumor cells derived from IGF-I(-/-) mice were GF dependent, similar to C/EBP beta-deficient cells. Forced expression of either C/EBP beta or IGF-I in C/EBP beta(-/-) bone marrow cells restored Myc/Raf-induced transformation and permitted neoplastic growth without exogenous GFs. Thus, our findings demonstrate that C/EBP beta is essential for oncogenic transformation of macrophages and functions at least in part by regulating expression of the survival factor IGF-I.

The insulin-like growth factor-I (IGF-I) receptor kinase inhibitor NVP-ADW742, in combination with STI571, delineates a spectrum of dependence of small cell lung cancer on IGF-I and stem cell factor signaling

Stem cell factor (SCF)/Kit and insulin-like growth factor-I (IGF-I)/IGF-I receptor (IGF-IR) autocrine loops play a prominent role in the growth of small cell lung cancer (SCLC). Previous data suggested that IGF-I protects cells from apoptosis induced by STI571, an efficient inhibitor of Kit signal transduction, by activating the critical phosphatidylinositol 3-kinase-Akt pathway. To determine if inhibition of IGF-IR signaling would be therapeutically relevant in SCLC, the activity of a novel kinase inhibitor of IGF-IR, NVP-ADW742 (Novartis Pharma AG, Basel, Switzerland), was characterized. Pretreatment of the H526 cell line with NVP-ADW742 inhibited IGF-IR signaling and growth with IC50 values between 0.1 and 0.4 μm. SCF-mediated Kit phosphorylation and Akt activation were inhibited with IC50 values in the 1–5 μm range. However, NVP-ADW742 affected neither hepatocyte growth factor-mediated Akt activation nor activity of constitutively active Akt. The therapeutic potential of NVP-ADW742 was assessed by determining its effect on growth of several SCLC cell lines in serum. These studies clearly delineated two populations of cell lines as determined by differential sensitivity to NVP-ADW742. One population, which lacks active SCF/Kit autocrine loops, was inhibited with IC50 values between 0.1 and 0.5 μm. A second population, which has active SCF/Kit autocrine loops, was inhibited with IC50 values in the 4–7 μm range. When these cell lines were treated with a combination of STI571 and NVP-ADW742, no advantage was seen in the former group, whereas, in the latter group, a clearly synergistic response to the combination was seen when growth, apoptosis, or Akt activation was assessed. These data demonstrate that NVP-ADW742 is a potent and selective IGF-IR kinase inhibitor that can efficiently inhibit the growth of cells that are highly dependent on IGF-I signaling. However, for optimal growth inhibition of SCLC cells with an active SCF/Kit autocrine loop, a combination of a Kit inhibitor (STI571) and an IGF-IR inhibitor (NVP-ADW742) appears to be necessary. These observations suggest that, in tumors in which critical signal transduction pathways can be activated by alternative receptors, optimal therapy may require inhibition of multiple receptors.

Evaluation of the synergistic effect of insulin resistance and insulin-like growth factors on the risk of breast carcinoma

BACKGROUND

The purpose of the current study was to investigate the association between insulin resistance (which was measured using fasting blood C-peptide) and its joint association with insulin-like growth factors (IGF-1, IGF-2, and IGF binding protein-3 [IGFBP-3]) on the risk of breast carcinoma.

METHODS

Included in the current study were 400 case-control pairs from the Shanghai Breast Cancer Study. Pretreatment biospecimens and interview data were collected from all breast carcinoma cases and their individually matched controls.

RESULTS

Breast carcinoma risk was found to be statistically significantly increased when higher blood levels of C-peptide and IGFs were noted in a dose-response manner. There was a statistically significant twofold to threefold increased risk of breast carcinoma for women in the highest quartile of C-peptide, IGF-1, or IGFBP-3 compared with women in the lowest quartiles. Women with high levels of both C-peptide and IGF-1 or IGFBP-3 also were found to have a substantially higher risk of breast carcinoma than those women with a high level of only one of these molecules. The adjusted odds ratios (ORs) were 3.79 (95% confidence interval [95% CI], 2.03-7.08) for those with a higher level of both C-peptide and IGF-1 and 4.03 (95% CI, 2.06-7.86) for those with a higher level of both C-peptide and IGFBP-3.

CONCLUSIONS

The results of the current study suggest that insulin resistance and IGFs may synergistically increase the risk of breast carcinoma.

IGF-I stimulates IL-8 production in the promyelocytic cell line HL-60 through activation of extracellular signal-regulated protein kinase

Interleukin (IL)-8 serves as a major chemoattractant for neutrophils and has also been proposed to affect cancer progression. In the present study, we show that IGF-I stimulates IL-8 mRNA expression and IL-8 secretion in the leukemic cell line HL-60. Stimulation of IL-8 expression was completely attenuated by two inhibitors of mitogen-activated protein kinase (MAPK) kinase (MEK), which phosphorylates the MAPKs extracellular-regulated kinase (ERK)1 and ERK2, and by the c-Jun NH2-terminal kinase (JNK) inhibitor SP600125. In contrast, inhibitors of p38 MAPK and phosphatidylinositol-3 kinase (PI3K) did not abrogate the effect of IGF-I. We also show that IGF-I stimulates the activation of ERK1 and ERK2, but we could not detect any effect of IGF-I on the phosphorylation of p38, JNK(p46) or JNK(p54). Collectively, our results suggest that basal JNK activity and activation of the MEK-ERK pathway are required for upregulation of IL-8 by IGF-I in HL-60 cells.