Insulinlike growth factors and binding proteins in colon cancer

Obesity and inflammation: colorectal cancer engines

The prevalence of obesity continues to increase to the extent that it became a worldwide pandemic. An accumulating body of evidence has associated obesity with the development of different types of cancer, including colorectal cancer, which is a notorious disease with a high mortality rate. At the molecular level, colorectal cancer is a heterogenous disease characterized by a myriad of genetic and epigenetic alterations associated with various forms of genomic instability (detailed in Supplementary Materials). Recently, the microenvironment has emerged as a major factor in carcinogenesis. Our aim is to define the different molecular alterations leading to the development of colorectal cancer in obese patients with a focus on the role of the microenvironment in carcinogenesis. We also highlight all existent molecules in clinical trials that target the activated pathways in obesity-associated colorectal cancer, whether used as single treatments or in combination. Obesity predisposes to colorectal cancer via creating a state of chronic inflammation with dysregulated adipokines, inflammatory mediators, and other factors such as immune cell infiltration. A unifying theme in obesity-mediated colorectal cancer is the activation of the PI3K/AKT, mTOR/MAPK, and STAT3 signaling pathways. Different inhibitory molecules towards these pathways exist, increasing the therapeutic choice of obesity-associated colon cancer. However, obese patients are more likely to suffer from chemotherapy overdosing. Preventing obesity through maintaining a healthy and active lifestyle remains to be the best remedy.

Crossroad between Obesity and Gastrointestinal Cancers: A Review of Molecular Mechanisms and Interventions

The burden of gastrointestinal (GI) cancer is increasing worldwide, and in the past decade, cancer had entered the list of chronic debilitating diseases whose risk is substantially increased by hypernutrition. Obesity may increase the risk of cancer by the imbalance of various mechanisms including insulin and insulin-like growth factor1 (IGF-I) signaling, systemic inflammation, immune dysregulation, tumor angiogenesis, adipokines secretion, and intestinal microbiota that usually act interdependently. An increased understanding of the mechanisms underlying obesity-GI cancer link can provide multiple opportunities for cancer prevention. This review discusses various mechanisms involved molecular mechanisms linking obesity with GI cancers including esophagus, stomach, colorectal and hepatocellular. Furthermore, an optional intervention such as diet restriction and exercise is described, which may be preventive or therapeutic in GI cancer.

Alpha-Glucosidase Inhibitor Voglibose Suppresses Azoxymethane-Induced Colonic Preneoplastic Lesions in Diabetic and Obese Mice

Type 2 diabetes mellitus and its related insulin resistance are known to increase the risk of cancer. Anti-diabetic agents can improve insulin resistance and may lead to the suppression of carcinogenesis. This study aimed to investigate the preventive effects of the alpha-glucosidase inhibitor voglibose on the development of azoxymethane-induced colorectal pre-neoplastic lesions in obese and diabetic C57BL/KsJ-db/db mice. The direct effects of voglibose on the proliferation of colorectal cancer cells were also evaluated. Mice were injected with azoxymethane to induce colorectal pre-malignancy and were then administered drinking water with or without voglibose. At the end of the study, the administration of voglibose significantly suppressed the development of colorectal neoplastic lesions. In voglibose-treated mice, serum glucose levels, oxidative stress, as well as mRNA expression of the insulin-like growth factor-1 in the colon mucosa, were reduced. The proliferation of human colorectal cancer cells was not altered by voglibose. These results suggested that voglibose suppressed colorectal carcinogenesis in a diabetes- and obesity-related colorectal cancer model, presumably by improving inflammation via the reduction of oxidative stress and suppressing of the insulin-like growth factor/insulin-like growth factor-1 receptor axis in the colonic mucosa.

Cytokines and metabolic factors regulate tumoricidal T-cell function during cancer immunotherapy

Recent advances in cancer biology and genetics have fostered precision therapies targeting tumor-specific attributes. Immune-based therapies that elicit cytolytic T cells (CTL) specific for tumor antigens can provide therapeutic benefit to cancer patients, however, cure rates are typically low. This largely results from immunosuppressive mechanisms operating within the tumor microenvironment, many of which inflict metabolic stresses upon CTL. Conversely, immunotherapies can mitigate specific metabolic stressors. For instance, dual costimulation immunotherapy with CD134 (OX40) plus CD137 (4-1BB) agonists appears to mediate tumor control in part by engaging cytokine networks that enable infiltrating CTL to compete for limiting supplies of glucose. Future efforts combining modalities that endow CTL with complimentary metabolic advantages should improve therapeutic efficacies.

Diets link metabolic syndrome and colorectal cancer development (Review)

Diets have been believed to be an important factor in the development of metabolic syndrome and colorectal cancer (CRC). In recent years, many studies have shown an intimate relationship between mucosal immunity, metabolism and diets, which has led to a greater understanding of the pathophysiology of metabolic syndrome and CRC development. Although the precise effects of diets on oncogenesis have not been compl-etely elucidated, microbiota changes and inflammation are believed to be important factors that influence the development of CRC. Moreover, increased release of pro-inflammatory cytokines and alteration of adipokine levels have been observed in patients with colorectal adenoma and/or CRC, and these all have been considered as the important mechanisms that link diets to the development of metabolic syndrome and CRC. Importantly, a high-fat, low-fiber diet is associated with dysbiosis, and as the gut signature becomes more important in metabolic syndrome and CRC, an increased understanding of diets on bacterial activity in the pathogenesis of metabolic syndrome and CRC will lead to new preventive and therapeutic strategies.

The impact of BMI on early colorectal neoplastic lesions and the role of endoscopic diagnosis:. An Italian observational study

INTRODUCTION

CRC often arises from polyps: an early detection and resection are effective in decreasing both incidence and mortality rate. Relation between risk factors, adenomas and CRC have been showed, but there is little evidence for overweight association with preneoplastic lesions. This study analyzed the correlation between body mass index (BMI) and primitive site of polyps.

METHODS

We performed a retrospective study, in a period between January 2010 and October 2014. Subjects aged 50 years and older who underwent their first-time screening colonoscopy were included. Reports regarding characteristic of the polyps were collected.

RESULTS

142 patients were enrolled and they were divided into two groups: group I - patients with left sided colonic polyps, and group II - patients who right sided colonic polyps. The ANOVA test-one way, documents a difference between the BMI and the colon localization of polyps.

CONCLUSIONS

Patients with overweight had a higher risk to develop lesions in the left colon compared to patients with normal weight. Despite the fact that Italian epidemiological studies have found a prevalence of polyps of 44-53% in rectal-sigmoid segment, 32-36% in transverse segment and of 14-20% in right segment, we showed an incidence of 26.05% for right sided polyps, which maybe related with the eating habits of the territory.

Mechanisms behind the link between obesity and gastrointestinal cancers

Obesity and obesity-related disorders such as non-alcoholic fatty liver disease (NAFLD), metabolic syndrome and type 2 diabetes exhibit an increased risk of developing various gastrointestinal cancers. These malignancies include mainly esophageal, gastric, colorectal, pancreatic and hepatocellular carcinoma. Whereas underlying pathomechanisms remain unclear, chronic inflammation accompanying obesity has evolved in the last years as a crucial contributing factor. Obesity is also commonly characterized by inflammation in the organ where those cancers appear. Various pathways might participate involving rather diverse components such as innate immunity, (adipo)-cytokines such as adiponectin or leptin, insulin, insulin-like growth factors, the gut's microbiota and others. An imbalance in these systems could substantially contribute to chronic inflammation and subsequent cancer development. Future studies have to elucidate in more detail underlying mechanisms in the development of obesity-related carcinogensis and potential therapeutic strategies besides weight loss.

Mechanisms of obesity-induced gastrointestinal neoplasia

Obesity is among the fastest growing diseases worldwide; treatment is inadequate, and associated disorders, including gastrointestinal cancers, have high morbidity and mortality. An increased understanding of the mechanisms of obesity-induced carcinogenesis is required to develop methods to prevent or treat these cancers. In this report, we review the mechanisms of obesity-associated colorectal, esophageal, gastric, and pancreatic cancers and potential treatment strategies.

Nutraceutical approach for preventing obesity-related colorectal and liver carcinogenesis

Obesity and its related metabolic abnormalities, including insulin resistance, alterations in the insulin-like growth factor-1 (IGF-1)/IGF-1 receptor (IGF-1R) axis, and the state of chronic inflammation, increase the risk of colorectal cancer (CRC) and hepatocellular carcinoma (HCC). However, these findings also indicate that the metabolic disorders caused by obesity might be effective targets to prevent the development of CRC and HCC in obese individuals. Green tea catechins (GTCs) possess anticancer and chemopreventive properties against cancer in various organs, including the colorectum and liver. GTCs have also been known to exert anti-obesity, antidiabetic, and anti-inflammatory effects, indicating that GTCs might be useful for the prevention of obesity-associated colorectal and liver carcinogenesis. Further, branched-chain amino acids (BCAA), which improve protein malnutrition and prevent progressive hepatic failure in patients with chronic liver diseases, might be also effective for the suppression of obesity-related carcinogenesis because oral supplementation with BCAA reduces the risk of HCC in obese cirrhotic patients. BCAA shows these beneficial effects because they can improve insulin resistance. Here, we review the detailed relationship between metabolic abnormalities and the development of CRC and HCC. We also review evidence, especially that based on our basic and clinical research using GTCs and BCAA, which indicates that targeting metabolic abnormalities by either pharmaceutical or nutritional intervention may be an effective strategy to prevent the development of CRC and HCC in obese individuals.

C57BL/KsJ-db/db-Apc mice exhibit an increased incidence of intestinal neoplasms

The numbers of obese people and diabetic patients are ever increasing. Obesity and diabetes are high-risk conditions for chronic diseases, including certain types of cancer, such as colorectal cancer (CRC). The aim of this study was to develop a novel animal model in order to clarify the pathobiology of CRC development in obese and diabetic patients. We developed an animal model of obesity and colorectal cancer by breeding the C57BL/KsJ-db/db (db/db) mouse, an animal model of obesity and type II diabetes, and the C57BL/6J-Apc(Min/+) (Min/+) mouse, a model of familial adenomatous polyposis. At 15 weeks of age, the N9 backcross generation of C57BL/KsJ-db/db-Apc(Min/+) (db/db-Min/+) mice developed an increased incidence and multiplicity of adenomas in the intestinal tract when compared to the db/m-Min/+ and m/m-Min/+ mice. Blood biochemical profile showed significant increases in insulin (8.3-fold to 11.7-fold), cholesterol (1.2-fold to 1.7-fold), and triglyceride (1.2-fold to 1.3-fold) in the db/db-Min/+ mice, when compared to those of the db/m-Min/+ and m/m-Min/+ mice. Increases (1.4-fold to 2.6-fold) in RNA levels of insulin-like growth factor (IGF)-1, IRF-1R, and IGF-2 were also observed in the db/db- Min/+ mice. These results suggested that the IGFs, as well as hyperlipidemia and hyperinsulinemia, promoted adenoma formation in the db/db-Min/+ mice. Our results thus suggested that the db/db-Min/+ mice should be invaluable for studies on the pathogenesis of CRC in obese and diabetes patients and the therapy and prevention of CRC in these patients.

Effects of diet-induced obesity on colitis-associated colon tumor formation in A/J mice

OBJECTIVE

Studies have indicated that obesity is associated with a higher risk of colorectal cancer. This study was performed to determine the effect of diet-induced obesity on the formation of azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colon tumors and to identify adiposity-related mechanisms.

METHODS

Male A/J mice were placed on either a high-fat diet (HFD; 45% of total calories from fat) or a normal diet (ND; 15% of calories from fat) for 12 weeks. To induce colon tumors, AOM was administered at a dose of 10 mg/kg body weight, followed by two cycles of DSS supply.

RESULTS

Study results indicated that the HFD group had twofold higher numbers of colonic tumors, as compared with the ND group. The HFD group also had significantly increased body weight and epididymal fat weight, which were associated with increases of serum insulin, insulin-like growth factor-1, leptin, epididymal fat pad leptin mRNA and colonic leptin receptor (Ob-R) mRNA. Animals on HFD showed higher expressions of Ob-R, insulin receptor, phosphorylated Akt, phosphorylated extracellular signal-regulated kinases, Bcl-xL and Cyclin D1 proteins in the colon.

CONCLUSION

The results suggest that HFD-induced obesity facilitates colon tumor formation, possibly by regulating downstream targets of circulating adiposity-related factors via receptor-mediated signaling of the phosphatidylinositol 3-kinase/Akt pathway.

Insulin-like growth factors are more effective than progastrin in reversing proapoptotic effects of curcumin: critical role of p38MAPK

Progastrin and insulin-like growth factors (IGFs) stimulate hyperproliferation of intestinal epithelial cells (IECs) via endocrine/paracrine routes; hyperproliferation is a known risk factor for colon carcinogenesis. In the present study, inhibitory potency of curcumin in the presence or absence of progastrin and/or IGF-II was examined. Progastrin and IGF-II significantly increased proliferation of an immortalized IEC cell line, IEC-18, whereas curcumin decreased the proliferation in a dose-dependent manner. IGF-II was significantly more effective than progastrin in reversing antiproliferative effects of curcumin and reversed proapoptotic effects of curcumin by >80%; progastrin was relatively ineffective toward reversing proapoptotic effects of curcumin. IEC-18 clones were generated to overexpress either progastrin (IEC-PG) or hIGF-II (IEC-IGF). Proliferation of IEC-PG and IEC-IGF clones was increased, compared with that of control clones. Curcumin significantly reduced proliferation of IEC-PG, but not IEC-IGF, clones. Similarly, a human colon cancer cell line, Caco-2 (which expresses autocrine IGF-II), was relatively resistant to inhibitory effects of curcumin. However, Caco-2 cells treated with anti-IGF-II-antibodies were rendered sensitive to inhibitory effects of curcumin. Significant differences in inhibitory potency of curcumin against PG- vs. IGF-II-stimulated growth of IEC-18 cells were not reflected by differences in curcumin-mediated inhibition of activated (phosphorylated) ERKs/IKK(alpha/beta)/p65NF-kappaB and c-Src in wild-type (wt)IEC-18 cells, in response to the two growth factors. Surprisingly, curcumin was almost ineffective in reducing IGF-II-stimulated activation of p38MAPK but significantly reduced progastrin-stimulated phosphorylation of p38. Treatment with a p38MAPK inhibitor resulted in loss of protective effects of IGF-II against inhibitory effects of curcumin. These novel findings suggest that growth factor profile of patients and tumors may dictate inhibitory potency of curcumin and that combination of curcumin + p38MAPK inhibitor may be required for reducing hyperproliferative or tumorigenic response of IECs to endocrine and autocrine IGFs.

Physical activity and gastrointestinal cancer prevention

Colorectal cancer is the third most common cancer globally and is a leading cause of cancer death. Gastric cancer contributes significantly to the global cancer burden, particularly in low- and middle-income countries. We reviewed the literature for studies on physical activity or exercise and colon, rectal, and gastric cancers as well as colonic adenomatous polyps. We identified 52 studies of colon cancer, 31 studies of rectal cancer, 23 studies of colon polyps, and 16 studies of gastric cancer. Of the 52 studies of physical activity and colon cancer, 37 found a statistically significant association between increased levels of physical activity and decreased colon cancer risk in at least one comparison. Accumulated evidence suggests that physical activity is associated with a 25% reduction in colon cancer risk. In line with previous reports, we found no indication that the association was more pronounced for occupational versus recreational physical activity, with both resulting in a risk reduction of about 22%. Evidence for other domains of physical activity (i.e., transportation or household physical activity) is limited. Evidence is emerging that individuals who are consistently active across the lifetime may obtain greater risk reductions than those who are only active in recent years. Despite consistent associations with colon cancer, evidence is more limited though suggestive that physical activity reduces risk of colon adenomas or adenoma recurrence. There is clear evidence that physical activity is not associated with rectal or gastric cancers.

Obesity, the PI3K/Akt signal pathway and colon cancer

Obesity is currently reaching epidemic levels worldwide and is a major predisposing factor for a variety of life-threatening diseases including diabetes, hypertension and cardiovascular diseases. Recently, it has also been suggested to be linked with cancer. Epidemiological studies have shown that obesity increases the risk of colon cancer by 1.5-2 fold with obesity-associated colon cancer accounting for 14-35% of total incidence. Several factors, altered in obesity, may be important in cancer development including increased levels of blood insulin, insulin-like growth factor I, leptin, TNF-alpha, IL-6 as well as decreased adiponectin. A unifying characteristic of all these factors is that they increase the activity of the PI3K/Akt signal pathway. The PI3K/Akt signal pathway in turn activates signals for cell survival, cell growth and cell cycle leading to carcinogenesis. Here we review the evidence that PI3K/Akt and its downstream targets are important in obesity-associated colon cancer and thus, that targeted inhibition of this pathway could be employed for the prevention of obesity-associated colon cancer and incorporated into the therapy regime for those with irremovable colon cancers.

Supplementation with branched-chain amino acids inhibits azoxymethane-induced colonic preneoplastic lesions in male C57BL/KsJ-db/db mice

PURPOSE

Obesity and related metabolic abnormalities, including insulin resistance and activation of the insulin-like growth factor (IGF)/IGF-I receptor (IGF-IR) axis, are risk factors for colon cancer. Supplementation with branched-chain amino acids (BCAA) reduces the risk of liver cancer in cirrhotic patients who are obese, and this has been associated with an improvement of insulin resistance. The present study examined the effects of BCAA on the development of azoxymethane (AOM)-initiated colonic premalignant lesions in C57BL/KsJ-db/db (db/db) mice that were obese and had hyperinsulinemia.

EXPERIMENTAL DESIGN

Male db/db mice were given 4 weekly s.c. injections of AOM (15 mg/kg of body weight) and then they were fed a diet containing 3.0% BCAA or casein, a nitrogenc content-matched control diet, for 7 weeks.

RESULTS

Feeding with BCAA caused a significant reduction in the number of total aberrant crypt foci and beta-catenin accumulated crypts, both of which are premalignant lesions of the colon, compared with the control diet-fed groups. BCAA supplementation caused a marked decrease in the expression of IGF-IR, the phosphorylated form of IGF-IR, phosphorylated glycogen synthase kinase 3beta, phosphorylated Akt, and cyclooxygenase-2 proteins on the colonic mucosa of AOM-treated mice. The serum levels of insulin, IGF-I, IGF-II, triglyceride, total cholesterol, and leptin were also decreased by supplementation with BCAA.

CONCLUSION

BCAA supplementation in diet improves insulin resistance and inhibits the activation of the IGF/IGF-IR axis, thereby preventing the development of colonic premalignancies in an obesity-related colon cancer model that was also associated with hyperlipidemia and hyperinsulinemia. BCAA, therefore, may be a useful chemoprevention modality for colon cancer in obese people.

(-)-Epigallocatechin gallate suppresses azoxymethane-induced colonic premalignant lesions in male C57BL/KsJ-db/db mice

Obesity and diabetes mellitus are risk factors for colon cancer. The activation of the insulin-like growth factor (IGF)/IGF-IR axis plays a critical role in this carcinogenesis. (-)-Epigallocatechin gallate (EGCG), the major constituent of green tea, seems to have both antiobesity and antidiabetic effects. This study examined the effects of EGCG on the development of azoxymethane-induced colonic premalignant lesions in C57BL/KsJ-db/db (db/db) mice, which are obese and develop diabetes mellitus. Male db/db mice were given four weekly s.c. injections of azoxymethane (15 mg/kg body weight) and then they received drinking water containing 0.01% or 0.1% EGCG for 7 weeks. At sacrifice, drinking water with EGCG caused a significant decrease in the number of total aberrant crypt foci, large aberrant crypt foci, and beta-catenin accumulated crypts in these mice, all of which are premalignant lesions of the colon. The colonic mucosa of db/db mice expressed high levels of the IGF-IR, phosphorylated form of IGF-IR (p-IGF-IR), p-GSK-3beta, beta-catenin, cyclooxygenase-2, and cyclin D1 proteins, and EGCG in drinking water caused a marked decrease in the expression of these proteins. Treating these mice with EGCG also caused an increase in the serum level of IGFBP-3 while conversely decreasing the serum levels of IGF-I, insulin, triglyceride, cholesterol, and leptin. EGCG overcomes the activation of the IGF/IGF-IR axis, thereby inhibiting the development of colonic premalignant lesions in an obesity-related colon cancer model, which was also associated with hyperlipidemia, hyperinsulinemia, and hyperleptinemia. EGCG may be, therefore, useful in the chemoprevention or treatment of obesity-related colorectal cancer.

Association between BMI and metabolic syndrome and adenomatous colonic polyps in Korean men

Obesity and insulin resistance are associated with the risk of colon cancer. Adenomatous colonic polyps are precancerous lesions of colon cancer. We investigated whether BMI and the metabolic syndrome are associated with the presence of adenomatous colonic polyps in Korean men. Anthropometric measurements, metabolic risk factors, and colonoscopic pathologic findings were assessed in 1,898 men who underwent routine colonoscopy at the Health Promotion Center of Asan Medical Center in 2005. The modified National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) and International Diabetes Federation (IDF) criteria were used for the definition of the metabolic syndrome. Multiple logistic regression analysis was used to evaluate the association between BMI and the metabolic syndrome and adenomatous polyps. Compared with men in the 1st quintile of the BMI, the adjusted odds ratio (OR) and 95% confidence interval (CI) for adenomatous polyps in men in the 2nd, 3rd, 4th, and 5th quintiles of the BMI were 1.55 (1.10-2.19), 1.57 (1.10-2.24), 1.94 (1.34-2.81), and 1.99 (1.31-3.01), respectively (P for trend <0.0001). Men with triglycerides (TGs) > or = 150 mg/dl were significantly more likely to have adenomatous polyps than were men with TG <150 mg/dl (OR 1.29; 95% CI 1.03-1.62). As a function of the number of metabolic risk factors, the ORs for adenomatous polyps were 1.41 (1.03-1.93), 1.52 (1.08-2.12), 1.46 (1.01-2.12), and 1.77 (1.08-2.90) for 1, 2, 3, and > or = 4 risk factors, respectively (P for trend <0.05). Adenomatous colonic polyps were significantly associated with increased BMI levels. Subjects with even one component of the metabolic syndrome had a significantly higher risk for developing adenomatous polyps compared to those subjects without any component in Korean men.

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.

Genetic variation in IGF1, IGFBP3, IRS1, IRS2 and risk of breast cancer in women living in Southwestern United States

BACKGROUND

An insulin-related pathway to breast cancer has been hypothesized.

METHODS

We examine the 19 CA repeat of the IGF1 gene, the -202 C > A IGFBP3, the G972R IRS, and the G1057D IRS2 polymorphisms among 1,175 non-Hispanic white (NHW) and 576 Hispanic newly diagnosed breast cancer cases and 1,330 NHW and 727 Hispanic controls living in Arizona, Colorado, New Mexico, and Utah.

RESULTS

Among post-menopausal women not recently exposed to hormones, not having the 19 CA repeat of IGF1 gene was associated with breast cancer among NHW women [odds ratio (OR) 2.14, 95% confidence interval (CI) 1.21-3.79] and having an R allele of G972R IRS1 increased breast cancer risk among Hispanic women (OR 2.70, 95% CI 1.13-6.46). Among post-menopausal Hispanic women recently exposed to hormones the A allele of the -202 C > A IGFBP3 polymorphism increased risk of breast cancer (OR 1.57, 95% CI 1.06-2.33). The IGF1 19 CA repeat polymorphism interacted with hormone replacement therapy (HRT) among NHW post-menopausal women; women who had the 19/19 IGF1 genotype were at reduced risk of breast cancer (OR 0.64, 95% CI 0.47-0.88) if they did not use HRT. We also observed interaction between body mass index and IGF1 19 CA repeat (p=0.06) and between weight gain and the -202 C > A IGFBP3 polymorphism (p=0.05) in NHW post-menopausal women not recently exposed to hormones.

CONCLUSIONS

Our data suggest that associations between insulin-related genes and breast cancer risk among women living in the Southwestern United States may be dependent on estrogen exposure and may differ by ethnicity.

Visceral fat analysis at CT colonography

RATIONALE AND OBJECTIVES

Obesity is associated with increased risks for colorectal neoplasia. Few studies have examined quantitative body fat measurements as predictors of colorectal polyps. The objective is to determine whether visceral fat is associated with colorectal polyps at computed tomography (CT) colonography.

MATERIALS AND METHODS

Case (n = 25) and control (n = 25) subjects with proven large (>1 cm) colorectal adenomas or normal colons respectively were randomly selected from among an established CT colonography research study cohort. Using supine CT colonography data, the body wall was traced at three levels: top of the right kidney, iliac crest, and superior acetabulum. Total area from the three slices and each slice area were determined within the visceral fat range (-170 to -45 Hounsfield units) and recorded within the selected region. Visceral fat measures were compared between patient groups with and without polyps.

RESULTS

None of the single slice visceral fat area measures or summed measures predicted case or control status. The most informative visceral fat measure was obtained at the top of the right kidney with a maximum area under the received operator characteristic curve of 0.77 (0.05 SE). For a selected sensitivity of 75%, the maximum specificity for a large (>or=1 cm) polyp was 64%.

CONCLUSION

In this pilot study, visceral fat measures at CT colonography were not significantly associated with the presence of large colorectal adenomas. However, odd ratios were elevated by a factor of 2. This suggests that a larger study may be justified.

The Response of Human Epithelial Cells to TNF Involves an Inducible Autocrine Cascade

Tumor necrosis factor (TNF) is a proinflammatory cytokine that induces conflicting pro- and antiapoptotic signals whose relative strengths determine the extent of cell death. TNF receptor (TNFR) has been studied in considerable detail, but it is not known how crosstalk among antagonistic pro- and antiapoptotic signals is achieved. Here we report an experimental and computational analysis of crosstalk between prodeath TNF and prosurvival growth factors in human epithelial cells. By applying classifier-based regression to a cytokine-signaling compendium of approximately 8000 intracellular protein measurements, we demonstrate that cells respond to TNF both directly, via activated TNF receptor, and indirectly, via the sequential release of transforming growth factor-alpha (TGF-alpha), interleukin-1alpha (IL-1alpha), and IL-1 receptor antagonist (IL-1ra). We refer to the contingent and time-varying series of extracellular signals induced by TNF as an "autocrine cascade." Time-dependent crosstalk of synergistic and antagonistic autocrine circuits may serve to link cellular responses to the local environment.

Insulin resistance, apoptosis, and colorectal adenoma risk

Compelling evidence from epidemiologic studies indicates that elevated circulating insulin-like growth factor (IGF)-I, insulin resistance, and associated complications, such as elevated fasting plasma insulin, glucose and free fatty acids, glucose intolerance, increased body mass index, and visceral adiposity, are linked with increased risk of colorectal cancer. However, the role of insulin and markers of glucose control in the development of adenomas, precursors to colorectal cancer, has not been fully explored. We evaluated the relationship between plasma insulin, glucose, IGF-I, IGF-II, IGF-binding protein-3 (IGFBP-3), apoptosis, and colorectal adenomas in a case-control study. Participants were drawn from consenting patients undergoing colonoscopy at the University of North Carolina hospitals (Chapel Hill, NC). Participants were classified as cases or controls based on whether they had one or more colorectal adenomatous polyps. Fasting plasma insulin, IGF-I, IGF-II, and IGFBP-3 levels were assessed by ELISA. Glucose was measured by glucose hexokinase assay. Apoptosis was assessed by morphology on H&E-stained sections. Dietary and lifestyle information were obtained by telephone interview. Logistic regression was used to examine the association between adenoma status and insulin-IGF markers. Adenoma cases (n = 239) and adenoma-free controls (n = 517) provided rectal biopsies and/or blood samples and interview data. Consistent with prior findings, cases were more likely to be males, older, have higher waist-to-hip ratio, lower calcium intake, lower apoptosis, and less likely to report nonsteroidal anti-inflammatory drug use. Those in the highest quartile of insulin (adjusted odds ratio, 2.2; 95% confidence interval, 1.1-4.2) and glucose (adjusted odds ratio, 1.8; 95% confidence interval, 0.9-3.6) were more likely to have an adenoma compared with the lowest quartile. Similarly, subjects in the highest two quartiles of insulin were more likely to be in the lowest two quartiles of apoptosis. Overall, there were no significant differences between mean circulating levels of glucose, IGF-I, IGF-II, and IGFBP-3 among cases and controls and no association between these variables and apoptosis. The results provide novel evidence that elevated insulin and glucose are associated with increased adenoma risk and decreased apoptosis in normal rectal mucosa. These findings suggest that insulin may act early in the adenoma-carcinoma sequence to promote the development of colorectal adenoma by decreasing apoptosis in the normal mucosa.

Insulin-like growth factor-I and insulin are associated with the presence and advancement of adenomatous polyps

BACKGROUND & AIMS

Insulin and insulin-like growth factor-I (IGF-I) affect proliferation, differentiation, and apoptosis and are potential risk factors for colorectal cancer (CRC). Visceral obesity, possibly via hyperinsulinemia, has also been linked to CRC risk. We evaluated the relationship of insulin, IGF-I, insulin-like growth factor binding protein (IGFBP) 3, and visceral adipose tissue (VAT) in subjects with adenomatous polyps, the precursor lesion of colorectal cancer.

METHODS

Participants were asymptomatic subjects who underwent screening flexible sigmoidoscopy (FSG) within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Subjects underwent single-slice, computerized tomography scanning to measure VAT and serum fasting insulin, IGF-I, and IGFBP-3 measurements.

RESULTS

Four hundred fifty-eight subjects were enrolled, of which 202 subjects had an adenoma, 70 of which were an advanced adenoma. IGF-I (P = .02), IGF-I/IGFBP-3 ratio (P = .003), and insulin (P = .02) were significantly increased in subjects with adenomas compared with controls. In an unadjusted logistic regression analysis using sex-specific quartile cut points, subjects in quartile 4 in comparison with quartile 1 of IGF-I (odds ratio [OR] = 1.7; [95% CI: 1.0-2.9], Ptrend = .03), IGF-I/IGFBP-3 ratio (OR = 1.9 [95% CI: 1.1-3.3], Ptrend = .01), and insulin (OR = 2.1 [95% CI: 1.2-3.6], Ptrend = .04) were at increased risk of adenoma. When limiting the case group to advanced adenomas, the effect was more pronounced: IGF-I (OR = 2.8 [95% CI: 1.3-6.2], Ptrend = .006), IGF-I/IGFBP-3 ratio (OR = 2.3, [95% CI: 1.0-5.2], Ptrend = .04), and insulin (OR = 2.3 [95% CI: 1.1-4.9], Ptrend = .14). Visceral adipose tissue was not associated with adenoma risk.

CONCLUSIONS

Levels of IGF-I, ratio of IGF-I/IGFBP-3, and insulin are associated with adenomas and even more so with advanced adenomas. These data support the hypothesis that insulin and IGF-I may contribute to the development and advancement of adenomatous polyps.

Regulation of vascular endothelial growth factor expression by insulin-like growth factor-II in human keratinocytes, differential involvement of mitogen-activated protein kinases and feedback inhibition of protein kinase C

BACKGROUND

Vascular endothelial growth factor (VEGF) is overexpressed in hyperproliferative diseases such as psoriasis and cancer, which are characterized by an increased angiogenesis. It was reported that insulin-like growth factor (IGF)-II is highly expressed during hepatocarcinogenesis and is increased in psoriatic lesions. The increase in IGF-II is believed to be associated with the pathogenesis of these diseases by increasing angiogenesis.

OBJECTIVES

In order to investigate the relationship between IGF-II and angiogenesis-related VEGF, VEGF expression in the IGF-II-treated human keratinocytes was monitored and the IGF-II signalling pathways were examined with respect to VEGF expression.

METHODS

Northern blot analysis for the VEGF mRNA levels and an enzyme-linked immunosorbent assay for the VEGF protein were performed to determine if IGF-II (100 ng mL(-1)) can increase the VEGF expression levels with or without a pretreatment with protein inhibitors in primary normal human keratinocytes and HaCaT cells.

RESULTS

The mRNA and protein levels of VEGF by IGF-II were increased in a time-dependent manner and reached the maximum level 2 h and 8 h after the IGF-II treatment, respectively. However, this increase was abrogated by pretreatment with an extracellular signal-regulated kinase (ERK) inhibitor but not by a p38 inhibitor. The IGF-II-mediated VEGF induction was also effectively inhibited by a pretreatment with the tyrosine kinase inhibitor and Src inhibitor. The PI3-kinase inhibitor also inhibited the expression of VEGF by IGF-II. However, the phospholipase C (PLC) and protein kinase C (PKC) inhibitors did not block the increases of VEGF mRNA level and its protein level by IGF-II, and the PKC inhibitor instead increased VEGF expression by IGF-II.

CONCLUSIONS

These results suggest that the tyrosine kinase-Src-ERK1/2 pathway and the PI3-kinase pathway are involved in IGF-II-mediated VEGF expression, but PKC is negatively associated in the IGF-II-mediated VEGF expression.

A recombinant humanized anti-insulin-like growth factor receptor type I antibody (h7C10) enhances the antitumor activity of vinorelbine and anti-epidermal growth factor receptor therapy against human cancer xenografts

Interaction of insulin-like growth factor receptor I (IGF-IR) with its ligands has been reported to induce cell proliferation, transformation and blockade of cell apoptotic functions. IGF-IR is overexpressed on numerous tumor cell types and its blockade could be of importance for anti-cancer therapy. We have generated a humanized anti-IGF-IR antibody h7C10 that blocks in vitro IGF-I and IGF-II-induced cell proliferation of MCF-7 breast cancer cells. Analysis of the IGF-I transduction cascade demonstrated that the humanized anti-IGF-IR antibody and its murine parental form block IGF-I-induced tyrosine phosphorylation, both its beta-chain and IRS-1 tyrosine phosphorylation. This presumably leads to cell cycle arrest and, consequently, growth inhibition. Treatment of nude mice bearing either human breast cancer cells (MCF-7) or non small lung cancer cells (A549) with h7C10, or its murine parental form 7C10, inhibited significantly tumor growth. An almost complete inhibition of A549 tumor growth was observed when mice were treated with the anti-IGF-IR antibody combined with either a chemotherapeutic agent, Vinorelbine or an anti-epidermal growth factor receptor (EGFR) antibody, 225. Combined therapy prolonged significantly the life span of mice in an orthotopic in vivo model of A549; the combination of the anti-IGF-IR antibody with an anti-EGFR antibody was superior to the Vinorelbine combination. The present results indicate that the humanized anti-IGF-IR antibody h7C10 has a great potential for cancer therapy when combined with either a chemotherapeutic agent or an antibody that targets other growth factor receptors, such as the epidermal growth factor receptor.

Energy balance, insulin-related genes and risk of colon and rectal cancer

Energy balance, or the ability to maintain body weight by balancing energy intake with energy expenditure, appears to be important in the etiology of colon cancer. One possible mechanism whereby energy balance may be associated with colorectal cancer is through its association with insulin. In our study, we evaluate the interaction between polymorphisms in 4 genes thought to be involved in insulin-related functions and components of energy balance with risk of colorectal cancer. Data from 2 population-based case-control studies of colon and rectal cancer conducted in Utah and Northern California were used to evaluate associations between body mass index (BMI), physical activity, energy intake and sucrose-to-fiber ratio and a CA repeat polymorphism of the IGF1 gene, the A/C polymorphism at nucleotide -202 of the IGFBP3, the G972R polymorphism of the IRS1 gene and the G1057D polymorphism of the IRS2 gene. A total of 1,346 incident colon cancer cases and 1,544 population-based controls and 952 incident rectal cancer cases and 1,205 controls were available for analysis. Inconsistent associations were identified between BMI, physical activity, energy intake and insulin-related genes. The 192/192 IGF1 genotype was associated with significant reduction in colon cancer risk among those with high physical activity (odds ratio [OR] 0.57; 95% confidence interval [CI] 0.39-0.83; p interaction 0.01). Although there was no significant pattern of interaction between either BMI or energy intake and polymorphisms assessed, specific sources of energy did appear to be more related to colon cancer risk in the presence of specific IRS2 and IGF1 genotypes. A high sucrose-to-fiber ratio increased risk of colon cancer in men who had the IRS2 DD genotype and among men who did not have the 192/192 IGF1 genotype. In summary, these data support the importance of components of energy balance in risk of colorectal cancer. Obesity, physical activity and energy intake appear to alter risk of colorectal cancer; however, the risk appears to be minimally influenced by genetic variants evaluated.

Low Levels of Insulin-Like Growth Factor Type 1 Receptor Expression at Cancer Cell Membrane Predict Liver Metastasis in Dukes’ C Human Colorectal Cancers

PURPOSE

The aim of this study was to evaluate the prognostic significance of insulin-like growth factor type 1 receptor (IGF-1R) expression in Dukes' C human colorectal cancers (CRCs).

EXPERIMENTAL DESIGN

Immunohistochemical staining for IGF-1R was done on formalin-fixed, paraffin-embedded specimens from 161 patients with curatively resected Dukes' C CRC and at least 5-year follow-up periods. We investigated the association between the levels of IGF-1R expression and the clinicopathologic parameters. To evaluate the accurate prognostic value of IGF-1R expression, we investigated two patterns of recurrence-free survival (RFS) according to the mode of recurrence, the hepatic-RFS (H-RFS), and the nonhepatic-RFS (nH-RFS). The influence of the pattern of IGF-1R immunostaining (membranous or cytoplasmic) on RFS was also estimated.

RESULTS

High (diffuse staining) and low (focal staining) levels of IGF-1R expression were found in 45 (28%) and 116 (72%) specimens, respectively. The recurrence rate was significantly higher in the latter group (49 of 116) than the former group (9 of 45; P = 0.01). H-RFS was significantly longer for the former group than the latter group (P = 0.021), whereas no difference was found in nH-RFS between the two groups (P = 0.121). In multivariate analysis, the level of IGF-1R expression was an independent factor for H-RFS (P = 0.015) as were the depth of invasion and lymph vessel invasion (P = 0.006 and 0.022, respectively). Using a combination of the level of IGF-1R expression and these two factors, the prognostic value was further increased. When IGF-1R staining patterns (membranous or cytoplasmic) were compared, membrane staining of IGF-1R possessed prognostic significance.

CONCLUSIONS

In Dukes' C CRC, focal membrane expression of IGF-1R in the primary tumor can predict a high risk of recurrence, especially liver metastasis. Understanding the mechanisms involved could lead to new therapeutic approaches for advanced CRC.

Portal and systemic serum growth factor and acute-phase response after laparotomy or partial hepatectomy in patients with colorectal liver metastases: a prognostic role for C-reactive protein and hepatocyte growth factor

BACKGROUND

Growth factors play a role in wound healing and tumour growth. The aim of this study was to compare the effect of partial hepatectomy (PH) and laparotomy on serum levels of growth factors and acute-phase proteins in patients with colorectal liver metastases and to correlate these levels with prognosis after PH.

METHODS

Epidermal growth factor (EGF), hepatocyte growth factor (HGF), insulin like growth factor-I (IGF-I), insulin, interleukin-6 (IL-6), C-reactive protein (CRP) and serum amyloid-A (SAA) were determined in portal and systemic serum in 24 PH patients and 9 laparotomy patients.

RESULTS

No differences were found in the clinicopathological characteristics of PH and laparotomy patients with the exception of the number of metastases, blood loss and operation time. The response of SAA, CRP and IGF-I was lower in PH patients than in laparotomy patients (P < 0.02). PH was associated with a higher IL-6 (P = 0.02) and HGF (P = 0.055) response than laparotomy. A higher HGF and CRP response was associated with a poorer prognosis. Total IGF-I was negatively correlated with the resected liver volume (r = -0.48, P < 0.05).

CONCLUSIONS

PH is associated with a lower acute-phase and total IGF-I response and a higher HGF and IL-6 response compared with laparotomy. HGF and CRP responses had an influence on the prognosis.

IGF-II-mediated COX-2 gene expression in human keratinocytes through extracellular signal-regulated kinase pathway

We monitored cyclooxygenase-2 (COX-2) expression in the insulin-like growth factor-II (IGF-II) treated human keratinocytes and explored the IGF-II signaling pathways with respect to the expression of COX-2. IGF-II induced COX-2 mRNA and protein levels, and the up-regulation of COX-2 expression by IGF-II was reduced by pretreatment with inhibitors of tyrosine kinase, Src and PI3-kinase. The inhibition of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) 1 also reduced the increased expression of COX-2 by IGF-II, but the inhibition of p38 did not. To further examine the roles of these mitogen-activated protein kinases (MAPKs) in IGF-II-induced COX-2 expression, we performed COX-2 promoter analysis using dominant negative plasmids of MEK1 (DN-MEK1), p38 (DN-p38) and JNK1 (DN-JNK1). Although IGF-II increased COX-2 promoter activity approximately 2.5-fold, this increase was blocked by cotransfection with DN-MEK1 or DN-JNK1. However, DN-p38 did not block the IGF-II-induced COX-2 promoter activity. In addition, inhibition of ERK or JNK1 reduced the increase of IGF-II-induced prostaglandin E(2) synthesis or cell proliferation. These results suggest that IGF-II induces COX-2 expression through the tyrosine kinase-Src-ERK and tyrosine kinase-PI3-kinase pathways, but not via p38 MAPK pathway, and that the basal JNK activity is required for the upregulation of COX-2 by IGF-II, as well.

Associations among IRS1, IRS2, IGF1, and IGFBP3 Genetic Polymorphisms and Colorectal Cancer

Introduction: Insulin, insulin-like growth factor (IGF), and IGF binding protein (IGFBP) are involved in cell growth and proliferation and are thought to be important in the etiology of colorectal cancer. We hypothesize that genetic polymorphisms of insulin receptor substrates (IRS-1 and IRS-2), IGF-I, and IGFBP-3 alter colorectal cancer risk because of their roles in the insulin-related signaling pathway. Methods: Data from a population-based incident case-control study of 1,346 colon cancer cases and 1,544 population-based controls and 952 rectal cancer cases and 1,205 controls were used to evaluate associations. Genetic polymorphisms of four genes were investigated: an IGF1 CA repeat, the IGFBP3 −202 A &gt; C, the IRS1 G972R, and the IRS2 G1057D. Results: Having at least one R allele (GR or RR) for IRS1 G972R was associated with an increased risk of colon cancer [odds ratio 1.4, 95% confidence interval (95% CI) 1.1-1.9]. The IRS2 G972R heterozygote GD genotype significantly reduced risk of colon cancer (odds ratio 0.8, 95% CI 0.6-0.9). Neither the IGF1 nor the IGFBP3 variants was associated independently with colon cancer, but there was an association when examined with IRS1. Individuals with an IRS1 R allele and IGF1 non-192 allele were at a 2-fold increased risk of colon cancer (95% CI 1.2-4.4). There was a 70% (95% CI 1.02-2.8) increased risk of colon cancer with an IRS1 R allele and the IGFBP3 AC or CC genotype. The IRS2 GD genotype reduced risk of colon cancer, except among those with an IRS1 R allele. No significant associations were seen in analyses of main effects or interactions of these variants and rectal cancer risk. Conclusions: Both IRS1 and IRS2 variants were associated with colon cancer risk independently. Associations were slightly stronger when polymorphisms in multiple genes were evaluated in conjunction with other genes rather than individually. These data suggest that the insulin-related pathway may be important in the etiology of colon cancer but not rectal cancer.

Aspirin, NSAIDs, and Colorectal Cancer: Possible Involvement in an Insulin-Related Pathway

Introduction: Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to reduce risk of colorectal cancer. Although inhibition of cyclooxygenase (COX)-2 is generally thought to be the relevant mechanism, aspirin-like drugs apparently are involved in other pathways and mechanisms. We explore the associations between aspirin/NSAIDs, the insulin-related pathway, and the risk of colorectal cancer. Methods: Genetic polymorphisms of five genes identified as being involved in an insulin-related pathway were genotyped using data collected in a case-control study of 1346 incident colon cancer cases and 1544 population-based controls and 952 incident rectal cancer cases and 1205 controls. Genotypes assessed were the 3′ untranslated region poly(A) and the intron 8 BsmI polymorphisms of the VDR gene, a CA repeat polymorphism of the IGF1 gene, the A/C polymorphism at nucleotide −202 of the IGFBP3, the Gly972Arg polymorphism of the IRS1 gene, and the Gly1057Asp polymorphism of the IRS2 gene. Results: Use of aspirin and NSAIDs was associated with a decreased risk of colorectal cancer, with slightly greater protection from NSAIDs than aspirin for rectal cancer. We observed a significant interaction between IRS1 genotype and aspirin/NSAIDs use and risk of colorectal cancer. Relative to the GR/RR IRS1 genotype, a protective effect from the GG IRS1 genotype was seen in those who did not use NSAIDs; use of NSAIDs was protective for all genotypes. These associations were especially strong for those diagnosed prior to age 65 (P interaction = 0.0006). We also observed a significant interaction between aspirin/NSAIDs use and the VDR gene. Having the SS or BB VDR genotypes reduced risk of colorectal cancer among non-aspirin/NSAID users; however, aspirin/NSAIDs reduced risk for all VDR genotypes. Conclusions: These data support the protective effect of aspirin and NSAIDs on colorectal cancer risk. In addition, the observed interactions for aspirin/NSAIDs and IRS1 and VDR genotypes suggest that mechanisms other than COX-2 inhibition may be contributing to the protective effect of aspirin and NSAIDs on colorectal cancer risk.

Relationship of visceral adipose tissue to recurrence of adenomatous polyps

OBJECTIVES

Insulin is a growth factor for colorectal cancer. Visceral adipose tissue (VAT) is strongly associated with insulin levels, and insulin and visceral obesity have been associated in cohort studies with colorectal cancer. The aim of this investigation was to determine whether VAT is associated with recurrence of adenomatous polyps, the precursor to colorectal cancer.

METHODS

As an ancillary study to the Polyp Prevention Trial, a randomized clinical trial that evaluated the effect of a low-fat, high-fiber, high vegetable and fruit diet on adenomatous polyp recurrence, subjects at one clinical center underwent measurement of VAT with a single-slice CT scan through the L4-L5 interspace. The scan was performed around the time of the subject's year 4 colonoscopy that determined adenoma recurrence.

RESULTS

Of 119 subjects, 44 of 84 men (52%) and 16 of 35 women (46%) had a recurrent adenoma (p= 0.51). Body mass index (BMI) and weight at baseline and at year 4 colonoscopy were unrelated to adenoma recurrence. In a multivariate model including visceral fat quartile, remote history of polyps, gender, age, and randomization group, only remote history of polyps was statistically significantly associated with recurrent adenoma with a relative risk of 4.6 (95% CI 1.7, 12.4, p= 0.001). There was no consistent monotonic trend of increased or decreased risk of recurrence as one ascended quartiles of adipose tissue for visceral, subcutaneous, or total abdominal fat.

CONCLUSION

In this study, no association between visceral adipose tissue and adenomatous polyp recurrence was observed. Further study and exploration of the role of VAT in adenoma progression is required.

trans-10, cis-12 conjugated linoleic acid reduces insulin-like growth factor-II secretion in HT-29 human colon cancer cells

We previously demonstrated that a mixture of conjugated linoleic acid (CLA) isomers decreases colon cancer incidence in rats treated with 1,2-dimethylhydrazine. Our in vitro studies have also shown that CLA inhibits the growth of HT-29 cells, a human colon cancer cell line. When we compared the individual potencies of the two main isomers found in the mixture of CLA isomers (e.g., cis-9, trans-11 [c9t11] and trans-10, cis-12 [t10c12]), t10c12 CLA decreased viable cell numbers in a dose-dependent manner. By contrast, c9t11 CLA had no effect. Therefore, the present study examined whether the decreased cell growth is related to changes in secretion of insulin-like growth factor (IGF)-II and/or IGF-binding proteins (IGFBPs) that have been shown to regulate HT-29 cell proliferation. Cells were incubated in serum-free medium with various concentrations of the individual CLA isomers, and immunoblot analysis of 24-hour, serum-free, conditioned media using a monoclonal anti-IGF-II antibody was performed. HT-29 cells secreted both mature 7,500 apparent molecular weight (M(r)) and higher-M(r) forms of IGF-II. t10c12 CLA decreased the levels of the higher-M(r) and the mature form of IGF-II in a dose-dependent manner, whereas c9t11 CLA had no effect. Ligand blot analysis of conditioned medium using (125)I-IGF-II revealed that the production of IGFBP-2 and IGFBP-4 was also decreased by t10c12 CLA, whereas c9t11 CLA had no effect. Exogenous IGF-II abrogated the growth inhibition induced by t10c12 CLA. These results indicate that inhibition of HT-29 cell growth by t10c12 CLA may be mediated by decreasing IGF-II secretion in these cells.

Identification of a novel SP3 binding site in the promoter of human IGFBP4 gene: role of SP3 and AP-1 in regulating promoter activity in CaCo2 cells

Insulin-like growth factor binding protein 4 (IGFBP4/BP4) gene expression plays an important role in the transition from proliferation to differentiation of a human colon cancer cell line, CaCo2. We recently cloned and identified multiple cis elements (including putative binding sites for activator protein 1 (AP-1) and specificity proteins (Sps) ) in the promoter of human BP4 gene, and measured a significant upregulation of the promoter activity in response to c-Jun. We therefore examined the role of the single AP-1 site (-869/-863) and other cis elements, in regulating the expression of hBP4 gene, in the current studies. Deletion of a 25 bp sequence from -872 to -848, which contains the AP-1 site, significantly reduced BP4 promoter activity by approximately 50%. Surprisingly, mutation of the AP-1 site did not produce significant alteration in the activity of the BP4 promoter. However, mutation of 7 bp (5'-TGCTGCA) at the 3' end of the AP-1 site resulted in significantly decreasing the promoter activity by >50%. Proteins bound to the 25 bp probe (-872/-848) could be supershifted by antibodies specific for JunD and Sp3 in an EMSA. JunD binding was abolished on mutation of the AP-1 site and Sp3 binding was abolished on mutation of the 7 bp at -861/-855; binding of the purified Sp3 protein to the 25 bp probe was similarly abolished on mutation of the newly discovered Sp3 binding site (TGCTGCA). BP4 promoter activity was upregulated in insect cells in response to Sp3 expression, confirming a functional importance of the novel Sp3 binding site. These studies suggest that the Sp3 binding site, rather than the AP-1 site, may be playing a significant role in regulating the expression of IGFBP4 gene in CaCo2 cells.

Plasma insulin, IGF-binding proteins-1 and -2 and risk of colorectal cancer: a prospective study in northern Sweden

Chronically elevated plasma insulin levels have been postulated to increase colon cancer risk, either directly through colonic insulin receptors or indirectly through downregulation of IGFBP-1 and/or IGFBP-2, thus increasing IGF activity. Our aim was to examine the relationships of plasma insulin and IGFBPs-1 and -2 with risks of colon and rectal cancers. We conducted a case-control study nested within the prospective Northern Sweden Health and Disease Cohort. Insulin and IGFBPs were measured in prediagnostic plasma samples from 168 men and women who developed cancers of the colon (n = 110) or rectum (n = 58) and from 336 matched controls. Conditional logistic regression analyses showed no significant relationship of plasma insulin with risk of colon or rectal cancer. In subjects whose blood samples had been collected after more than 4 hr of fasting, insulin showed a moderate but still nonsignificant association with colorectal cancer risk [ORs over quartiles: 1.00, 0.70 (95% CI 0.35-1.39), 1.06 (95% CI 0.55-2.07), 1.63 (95% CI 0.82-3.24); p(trend) = 0.10]. Plasma IGFBP-1 and IGFBP-2 showed no association with risk of colon and/or rectal cancer, either in the full study population or among the fasting subjects. Our results only moderately support a possible relationship of chronic hyperinsulinemia with colon cancer risk.

Expression and distribution of insulin-like growth factor-1 receptor in human carcinomas

The insulin-like growth factor-1 receptor (IGF1-R) is a cellular receptor overexpressed in many tumor cell lines and in some human tumors that seems to play a critical role in transformation, tumorigenicity, and metastasis. To date, a comprehensive evaluation of tissue distribution of IGF1-R in human carcinomas from different anatomical sites has been lacking. Using stage-oriented human cancer tissue microarrays, we studied IGF1-R expression and distribution in a group of 152 human carcinomas from a variety of anatomical sites and from 63 normal tissues through immunohistochemistry. The tumors included carcinomas from breast (8), ovary (9), endometrium (7), esophagus (5), stomach (7), pancreas (7), liver (4), colon (10), kidney (14), bladder (17), prostate (11), head and neck (31), salivary glands (8), lung (13), and skin (1). Formalin-fixed, paraffin embedded tissues of each case were immuno-stained using the avidin-biotin peroxidase method and an anti-IGF1-R rabbit polyclonal antibody. High-membranous IGF1-R staining was observed in 7 of 8 (87.5%) breast carcinomas, in 9 of 9 (100%) ovarian carcinomas, in 7 of 7 (100%) endometrial carcinomas, in 5 of 7 (71.1%) gastric carcinomas, in 4 of 7 (57.1%) pancreatic carcinomas, in 9 of 10 (90%) colon adenocarcinomas, in 11 of 13 (84.6%) lung carcinomas, in 6 of 11 (54.5%) prostatic adenocarcinomas, and in 17 of 17 (100%) transitional cell carcinomas of the bladder. Only a minority of squamous cell carcinomas of the head and neck and esophagus (34), salivary gland tumors (5), and renal cell carcinomas (14) were IGF1-R positive. This study demonstrates the overexpression of IGF1-R across a wide variety of human carcinomas of glandular or transitional cell origin.

Distribution of insulin like growth factor-1 (IGF-1) and its receptor in the intestines of the one-humped camel (Camelus dromedarius)

The distribution of insulin-like growth factor-1 (IGF-1) and its receptor in the gut of the one-humped camel (Camelus dromedarius) were studied by immunohistochemistry and quantitative receptor autoradiography. IGF-1-IR cells occurred mainly in the lamina propria and epithelium of the small intestine, while in the large intestine positive cells were seen in the columnar cells of the epithelial layer of colonic glands. IGF-I was also discernible in the muscularis externa of the intestines. Autoradiography revealed a higher concentration of receptors in the mucosa compared to the muscular layer. With regard to the mucosa, the highest density of receptors was discernible in the duodenum. Immunohistochemistry revealed the main sites of the receptors to be the lamina propria, epithelia of the crypts and the villi of intestines. Double immunofluorescence studies with combined antisera to IGF-I and its receptor showed that the ligand and its receptor usually occurred within the same cell in the mucosa. A few cells with varied profiles immunoreacted to either the ligand or the receptor but not to both. Cells with varied profiles immunoreacted to antiserum of the receptors but not to the ligand in the muscle layer. Thus IGF-1 might be acting on its receptor via both an autocrine and paracrine modes in the camel mucosa. In the muscularis layer, IGF-1 may be acting by different mechanisms. Our data demonstrate that unlike all other mammals studied, the camel contains a high concentration of IGF-1 receptors in the duodenal mucosa compared to other parts of the camel gut. It also possesses a higher concentration of the receptor in its mucosa compared to the muscle layer. We speculate that this might be a significant feature necessary for the regenerative ability of the duodenal mucosa in the one-humped camel.

Dairy products and colorectal cancer. A review of possible mechanisms and epidemiological evidence

OBJECTIVES

This review provides an overview of the principal hypotheses and epidemiological evidence of the possible links between colorectal cancer and intake of milk and/or dairy products.

METHODS

The first section outlines the main hypotheses about the possible effect of calcium, vitamin D, fats and other milk components. The possible role of acid lactic bacteria in fermented products is also discussed. The second section is a summary of the published epidemiological evidence. The results on milk, cheese and yoghurt are summarized using a meta-analytical approach. The results of studies on calcium and vitamin D are briefly described.

RESULTS

Case-control studies are heterogeneous and, on average, do not provide evidence of association between total intake of total dairy products, milk, cheese or yoghurt and colorectal cancer risk. The average result from cohort studies support the hypothesis of a protective effect of total dairy products (odds ratio (OR): 0.62; 95% confidence interval (CI): 0.52-0.74; P heterogeneity test: 0.93) and for milk (OR: 0.80; 95% CI: 0.68-0.95; P heterogeneity: 0.77). No association was found between cheese (OR: 1.10; 95% CI: 0.88-1.36; P heterogeneity: 0.55) or yoghurt (OR: 1.03; 95% CI: 0.83-1.28; P heterogeneity: 0.69) in cohort studies.

CONCLUSIONS

Cohort studies consistently found a protective effect of total dairy products and milk intake, but the evidence is not supported by case-control studies. No relationship was found with cheese or yoghurt intake. As the number of cohort studies is still limited, their results need to be confirmed by other prospective studies.

Biology of colorectal liver metastases

The elucidation of the interaction of the tumor and its microenvironment has increased surgeons' understanding of the biologic mechanisms mediating metastases formation. The ability to develop effective biologic therapies will depend on understanding the complex interactions among endothelial cells and tumor cells and on the cytokine cross-talk among all cells within a particular tumor at a particular site. Biologic therapies must be targeted to both the site and the tumor. By the time metastases form, most steps in the metastatic cascade have been completed. Therapy to down-regulate or interrupt the last stages of metastases, proliferation, and angiogenesis and mechanisms to disrupt cell survival signals appear to be the most promising areas of investigation.

Overexpression of the insulin-like growth factor I receptor in human colon carcinomas

BACKGROUND

High concentrations of insulin-like growth factor (IGF)-I and IGF-II have been demonstrated in human colonic adenocarcinomas and exert mitogenic effects through paracrine/autocrine interactions with the IGF-I receptor (IGF-IR). However, definitive studies of IGF-IR expression in these tissues have not been performed.

METHODS

To study changes in the levels of the IGF-IR in colorectal carcinoma, we analyzed the expression of IGF-IR in 40 paired samples of normal and carcinomatous colonic tissue by quantitative reverse-transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and ligand binding.

RESULTS

As measured by RT-PCR, the IGF-IR mRNA ratio in paired tumor and adjacent normal mucosa was higher than 2.0 in 32 of 40 (80%) samples. The overall mean IGF-IR mRNA level was five-fold higher in tumor versus adjacent normal mucosa (P < 0.0001). Overexpression of IGF-IR in colon carcinomas was confirmed at the protein level by immunohistochemistry and receptor-binding studies. Colon carcinoma cells exhibited a positive staining for IGF-IR in 91% of all tumors (30 of 33) whereas the adjacent normal colonic epithelial cells showed only a very faint or no significant IGF-IR immunoreactivity. Radioligand assays and Scatchard analysis in both tissue types revealed a single class of high-affinity IGF-IR-binding sites with a similar dissociation constant (K(d;) 0.14 +/- 0.02 nmol/L, n = 18). However, specific (125)IGF-I-binding and receptor concentrations were elevated in tumor membranes compared with normal mucosa (33.6 +/- 5.6 vs. 22.7 +/- 3.4 fmol/mg protein, P < 0.05). IGF-I affinity crosslinking and sodium dodecyl sulfate-polyacrylamide gel electrophoresis displayed specific bands corresponding to the size of the normal alpha-subunit of the IGF-IR that were more intense in carcinomatous samples. IGF-II mRNA levels were significantly elevated in colorectal carcinomas (P < 0.0001). The IGF-II mRNA ratio in tumor versus normal tissue was elevated more than twofold in 28 of 40 paired samples and a positive correlation was observed between the overexpression of IGF-II and IGF-IR in the tumors.

CONCLUSIONS

Our results demonstrate that, in addition to IGF-II, a strong overexpression of IGF-IR is found in the majority of colorectal carcinomas, supporting the hypothesis of an important role of the IGF system in the pathogenesis of colorectal carcinoma.

Transcription factor NF-Y regulates differentiation of CaCo-2 cells

The CaCo-2 cell line is used to study the molecular mechanisms underlying differentiation of intestinal epithelial cells. These cells undergo a gradual differentiation process that is growth-related and depends on cellular density. CaCo-2 cells acquire a morphological polarity and express such markers of mature enterocytes as sucrase-isomaltase, apolipoproteins, alkaline phosphatase, and H-ferritin. Because the NF-Y transcription factor is required for H-ferritin gene expression, we investigated whether it is involved in the expression of the other CaCo-2 differentiation markers. We observed that subunit NF-YA increases during CaCo-2 differentiation and that the constitutive expression of NF-YA, obtained in stably transfected CaCo-2 cells, results in the expression of differentiation markers. In fact, sucrase-isomaltase, apolipoprotein A1, and H-ferritin were constitutively expressed in NF-YA-transfected cells and their levels did not increase during prolonged culture, while these markers were not expressed in mock-transfected CaCo-2 cells or transfected with an inactive NF-YA expression vector until the onset of differentiation.

Impact of insulin-like growth factor receptor-I function on angiogenesis, growth, and metastasis of colon cancer

Insulin-like growth factors and their principal receptor, IGF-I receptor (IGF-IR), are frequently expressed in human colon cancers and play a role in preventing apoptosis, enhancing cell proliferation, and inducing expression of vascular endothelial growth factor (VEGF). The role of IGF-IR in regulating angiogenesis and metastases of human colon cancer has not been elucidated. To determine the in vitro and in vivo effects of IGF-IR in human colon cancer growth and angiogenesis, human KM12L4 colon cancer cells were transfected with a truncated dominant-negative form of IGF-IR (IGF-IR dom-neg). IGF-IR dom-neg-transfected cells demonstrated markedly decreased constitutive expression of VEGF mRNA and protein. Subcutaneous injections of IGF-IR dom-neg-transfected cells in nude mice led to significantly decreased tumor growth (p < 0.05) that was associated with decreased tumor cell proliferation, VEGF expression, and vessel count and with increased tumor cell apoptosis (p < 0.05 for all parameters compared with controls). In addition, pericyte coverage of endothelial cells was significantly decreased in tumors from IGF-IR dom-neg-transfected cells. Following this observation, we demonstrated in vitro that vascular smooth muscle cells migrated significantly less in conditioned medium derived from IGF-IR dom-neg-transfected cells compared with medium from control cells. After splenic injections, IGF-IR dom-neg transfectants failed to produce liver metastases, in contrast to parental cells and mock transfectants (p < 0.05). In addition, IGF-IR dom-neg-transfected cells failed to form liver tumors after direct injection into the liver. These studies demonstrate that the IGF-IR plays an important role in multiple mechanisms that mediate the growth, angiogenesis, and metastasis of human colon cancer. IGF-IR is a valid target for the therapy of human colon cancer.

Trans-10,cis-12-conjugated linoleic acid inhibits Caco-2 colon cancer cell growth

A commercially available mixture of conjugated linoleic acid (CLA) isomers decreases colon cancer cell growth. We compared the individual potencies of the two main isomers in this mixture [cis-9,trans-11 (c9t11) and trans-10,cis-12 (t10c12)] and assessed whether decreased cell growth is related to changes in secretion of insulin-like growth factor II (IGF-II) and/or IGF-binding proteins (IGFBPs), which regulate Caco-2 cell proliferation. Cells were incubated in serum-free medium with different concentrations of the individual CLA isomers. t10c12 CLA dose dependently decreased viable cell number (55 +/- 3% reduction 96 h after adding 5 microM t10c12 CLA). t10c12 CLA induced apoptosis and decreased DNA synthesis, whereas c9t11 CLA had no effect. Immunoblot analysis of 24-h serum-free conditioned medium using a monoclonal anti-IGF-II antibody revealed that Caco-2 cells secreted both a mature 7,500 molecular weight (M(r)) IGF-II and higher M(r) forms of IGF-II. The levels of the higher M(r) and the mature form of IGF-II were decreased 50 +/- 3% and 22 +/- 2%, respectively, by 5 microM t10c12 CLA. c9t11 CLA had no effect. Ligand blot analysis of conditioned medium using 125I-labeled IGF-II revealed that t10c12 CLA slightly decreased IGFBP-2 production; c9t11 CLA had no effect. Exogenous IGF-II reversed t10c12 CLA-induced growth inhibition and apoptosis. These results indicate that CLA-inhibited Caco-2 cell growth is caused by t10c12 CLA and may be mediated by decreasing IGF-II secretion in Caco-2 cells.

Prevention of cytokine-induced apoptosis by insulin-like growth factor-I is independent of cell adhesion molecules in HT29-D4 colon carcinoma cells-evidence for a NF-kappaB-dependent survival mechanism

We have previously established that insulin-like growth factor (IGF)-I, -II and insulin exert a strong protective effect against tumor necrosis factor-alpha (TNF)-induced apoptosis in interferon-gamma (IFN)-sensitized HT29-D4 human colon carcinoma cells. In this study, we report that this effect was still operative when cells were cultured in the absence of integrin- and E-cadherin-mediated cell-extracellular matrix and cell-cell interactions. In this model, IGF-I did not activate the focal adhesion kinase, whereas it induced tyrosine phosphorylation of the insulin receptor substrate-1 and activation of the extracellular signal-related kinase 1 and 2, p38, phosphatidylinositol 3'-kinase and protein kinase B/Akt. However, the use of specific inhibitors indicated that these pathways did not play a role in the adhesion-independent IGF-I anti-apoptotic signal. In contrast, inhibition of the NF-kappaB activation induced a complete reversal of the IGF-I anchorage-independent protective effect. Correspondingly, IGF-I markedly enhanced the TNF- and IFN/TNF-induced NF-kappaB-dependent interleukin-8 production. Our results provide evidence that IGF-I induces resistance against cytokine-induced cell death even in the absence of cell adhesion-mediated signaling. NF-kappaB appears to be a key mediator of this anti-apoptotic effect that should contribute to the resistance of colon cancer cells to immune-destruction during metastasis.

The insulin-like growth factor system as a therapeutic target in colorectal cancer

The purpose of this review is to examine recent evidence that investigates the role of the insulin-like growth factor (IGF) system in colorectal cancer. We concentrate on the evidence that makes the case for the investigation of strategies that might be used to disrupt the IGF system in prevention and treatment. Even though the weight of evidence suggests that components of the IGF system may be appropriate targets, there are a lack of studies that make a systematic characterisation of all the system components in human colorectal cancer. It is anticipated that this information, and the new therapeutic molecules which follow, will impact on the prevention and treatment of patients with this disease.