Role of insulin-like growth factor-1R system in colorectal carcinogenesis

Autophagy and the Insulin-like Growth Factor (IGF) System in Colonic Cells: Implications for Colorectal Neoplasia

Colorectal cancer (CRC) is one of the most common human malignancies worldwide. Along with apoptosis and inflammation, autophagy is one of three important mechanisms in CRC. The presence of autophagy/mitophagy in most normal mature intestinal epithelial cells has been confirmed, where it has mainly protective functions against reactive oxygen species (ROS)-induced DNA and protein damage. Autophagy regulates cell proliferation, metabolism, differentiation, secretion of mucins and/or anti-microbial peptides. Abnormal autophagy in intestinal epithelial cells leads to dysbiosis, a decline in local immunity and a decrease in cell secretory function. The insulin-like growth factor (IGF) signaling pathway plays an important role in colorectal carcinogenesis. This is evidenced by the biological activities of IGFs (IGF-1 and IGF-2), IGF-1 receptor type 1 (IGF-1R) and IGF-binding proteins (IGF BPs), which have been reported to regulate cell survival, proliferation, differentiation and apoptosis. Defects in autophagy are found in patients with metabolic syndrome (MetS), inflammatory bowel diseases (IBD) and CRC. In neoplastic cells, the IGF system modulates the autophagy process bidirectionally. In the current era of improving CRC therapies, it seems important to investigate the exact mechanisms not only of apoptosis, but also of autophagy in different populations of tumor microenvironment (TME) cells. The role of the IGF system in autophagy in normal as well as transformed colorectal cells still seems poorly understood. Hence, the aim of the review was to summarize the latest knowledge on the role of the IGF system in the molecular mechanisms of autophagy in the normal colon mucosa and in CRC, taking into account the cellular heterogeneity of the colonic and rectal epithelium.

Childhood Body Mass Index Is Associated with Risk of Adult Colon Cancer in Men: An Association Modulated by Pubertal Change in Body Mass Index

BACKGROUND

The relative contribution of childhood and pubertal body mass index (BMI) for the risk of adult colorectal cancer is not known. The aim of this study was to evaluate the independent associations for childhood BMI and pubertal BMI change with risk of colorectal cancer in men.

METHODS

We included 37,663 men born in 1946 to 1961 who had weight and height measured at 8 (childhood) and 20 (young adult age) years of age available from the BMI Epidemiology Study. Information on colorectal cancer was retrieved from the Swedish National Patient Register (257 cases of colon cancer and 159 cases of rectal cancer).

RESULTS

Childhood BMI at 8 years of age [HR, 1.19 per SD increase; 95% confidence interval (CI), 1.06-1.33], but not pubertal BMI change (HR, 1.02; 95% CI, 0.90-1.15), was associated with increased risk of colon cancer. Due to a significant interaction between childhood BMI and pubertal BMI change (P < 0.001), we stratified the analyses according to the median of pubertal BMI change. Childhood BMI was associated with risk of colon cancer in individuals with a pubertal BMI change above, but not below, the median (above: HR = 1.48, 95% CI, 1.26-1.74; below: HR = 0.95, 95% CI, 0.80-1.12). Neither childhood BMI nor pubertal BMI change was associated with rectal cancer.

CONCLUSIONS

High childhood BMI was associated with increased risk of colon cancer only if it was followed by a pubertal BMI increase above the median.

IMPACT

Further studies should evaluate prepubertal childhood BMI in relation to pubertal BMI change and BMI in middle age for the risk of colon cancer.

Protein kinase C (PKC) isoforms in cancer, tumor promotion and tumor suppression

The AGC family of serine/threonine kinases (PKA, PKG, PKC) includes more than 60 members that are critical regulators of numerous cellular functions, including cell cycle and differentiation, morphogenesis, and cell survival and death. Mutation and/or dysregulation of AGC kinases can lead to malignant cell transformation and contribute to the pathogenesis of many human diseases. Members of one subgroup of AGC kinases, the protein kinase C (PKC), have been singled out as critical players in carcinogenesis, following their identification as the intracellular receptors of phorbol esters, which exhibit tumor-promoting activities. This observation attracted the attention of researchers worldwide and led to intense investigations on the role of PKC in cell transformation and the potential use of PKC as therapeutic drug targets in cancer diseases. Studies demonstrated that many cancers had altered expression and/or mutation of specific PKC genes. However, the causal relationships between the changes in PKC gene expression and/or mutation and the direct cause of cancer remain elusive. Independent studies in normal cells demonstrated that activation of PKC is essential for the induction of cell activation and proliferation, differentiation, motility, and survival. Based on these observations and the general assumption that PKC isoforms play a positive role in cell transformation and/or cancer progression, many PKC inhibitors have entered clinical trials but the numerous attempts to target PKC in cancer has so far yielded only very limited success. More recent studies demonstrated that PKC function as tumor suppressors, and suggested that future clinical efforts should focus on restoring, rather than inhibiting, PKC activity. The present manuscript provides some historical perspectives on the tumor promoting function of PKC, reviewing some of the observations linking PKC to cancer progression, and discusses the role of PKC in the pathogenesis of cancer diseases and its potential usage as a therapeutic target.

Dalotuzumab in chemorefractory KRAS exon 2 mutant colorectal cancer: Results from a randomised phase II/III trial

Limited data are available on the efficacy of anti-IGF-1R agents in KRAS mutant colorectal cancer (CRC). We analysed the outcome of 69 chemorefractory, KRAS exon 2 mutant CRC patients who were enrolled in a double-blind, randomised, phase II/III study of irinotecan and cetuximab plus dalotuzumab 10 mg/kg once weekly (arm A), dalotuzumab 7.5 mg/kg every second week (arm B) or placebo (arm C). Objective response rate (5.6% vs. 3.1% vs. 4.8%), median progression-free survival (2.7 vs. 2.6 vs. 1.4 months) and overall survival (7.8 vs. 10.3 vs. 7.8 months) were not statistically significantly different between treatment groups. Most common grade ≥3 treatment-related toxicities included neutropenia, diarrhoea, hyperglycaemia, fatigue and dermatitis acneiform. Expression of IGF-1R, IGF-1, IGF-2 and EREG by quantitative real-time polymerase chain reaction was assessed in 351 patients from the same study with available data on KRAS exon 2 mutational status. Median cycle threshold values for all biomarkers were significantly lower (i.e., higher expression, p < 0.05) among patients with KRAS wild-type compared to those with KRAS exon 2 mutant tumours. No significant changes were found according to location of the primary tumour with only a trend towards lower expression of IGF-1 in colon compared to rectal cancers (p = 0.06). Albeit limited by the small sample size, this study does not appear to support a potential role for anti-IGF-1R agents in KRAS exon 2 mutant CRC. Data on IGF-1R, IGF-1 and IGF-2 expression here reported may be useful for patient stratification in future trials with inhibitors of the IGF pathway.

A Randomized Phase II/III Study of Dalotuzumab in Combination With Cetuximab and Irinotecan in Chemorefractory, KRAS Wild-Type, Metastatic Colorectal Cancer

BACKGROUND

Insulin-like growth factor type 1 receptor (IGF-1R) mediates resistance to epidermal growth factor receptor (EGFR) inhibition and may represent a therapeutic target. We conducted a multicenter, randomized, double blind, phase II/III trial of dalotuzumab, an anti-IGF-1R monoclonal antibody, with standard therapy in chemo-refractory, KRAS wild-type metastatic colorectal cancer.

METHODS

Eligible patients were randomly assigned to dalotuzumab 10mg/kg weekly (arm A), dalotuzumab 7.5mg/kg every alternate week (arm B), or placebo (arm C) in combination with cetuximab and irinotecan. Primary endpoints were progression-free survival (PFS) and overall survival (OS). Secondary endpoints included exploratory biomarker analyses. All statistical tests were two-sided.

RESULTS

The trial was prematurely discontinued for futility after 344 eligible KRAS wild-type patients were included in the primary efficacy population (arm A = 116, arm B = 117, arm C = 111). Median PFS was 3.9 months in arm A (hazard ratio [HR] = 1.33, 95% confidence interval [CI] = 0.98 to 1.83, P = .07) and 5.4 months in arm B (HR = 1.13, 95% CI = 0.83 to 1.55, P = .44) compared with 5.6 months in arm C. Median OS was 10.8 months in arm A (HR = 1.41, 95% CI = 0.99 to 2.00, P = .06) and 11.6 months in arm B (HR = 1.26, 95% CI = 0.89 to 1.79, P = .18) compared with 14.0 months in arm C. Grade 3 or higher asthenia and hyperglycaemia occurred more frequently with dalotuzumab compared with placebo. In exploratory biomarker analyses, patients with high IGF-1 mRNA tumors in arm A had numerically better PFS (5.6 vs 3.6 months, HR = 0.59, 95% CI = 0.28 to 1.23, P = .16) and OS (17.9 vs 9.4 months, HR = 0.67, 95% CI = 0.31 to 1.45, P = .31) compared with those with high IGF-1 mRNA tumors in arm C. In contrast, in arm C high IGF-1 mRNA expression predicted lower response rate (17.6% vs 37.3%, P = .04), shorter PFS (3.6 vs 6.6 months, HR = 2.15, 95% CI = 1.15 to 4.02, P = .02), and shorter OS (9.4 vs 15.5 months, HR = 2.42, 95% CI = 1.21 to 4.82, P = .01).

CONCLUSIONS

Adding dalotuzumab to irinotecan and cetuximab was feasible but did not improve survival outcome. IGF-1R ligands are promising biomarkers for differential response to anti-EGFR and anti-IGF-1R therapies.

Circulating levels of IGF-1, IGFBP-3, and IGF-1/IGFBP-3 molar ratio and colorectal adenomas: A meta-analysis

BACKGROUNDS

Insulin-like growth factor-1(IGF-1) promotes cell proliferation and inhibits apoptosis, and is thereby implicated in carcinogenesis. Insulin-like growth factor binding protein-3 (IGFBP-3) may antagonize IGF-1 action, leading to inhibition of the potential tumorigenicity of IGF-1. We conducted this meta-analysis to estimate the association between IGF-1, IGFBP-3 and IGF-1/IGFBP-3 ratio and the risk of colorectal adenomas (CRAs). Further, we investigated whether this association was different between occurrent and recurrent CRA, by adjustment for obesity, and by advanced CRA.

MATERIALS AND METHODS

Pubmed and Embase were searched up to April, 2015 to identify relevant observational studies and summary odds ratio (OR) and the corresponding 95% confidence interval (95% CI) was estimated using a random-effects model.

RESULTS

A total of 12 studies (11 studies including 3038 cases for IGF-1, 12 studies including 3208 cases for IGFBP-3, and 7 studies including 1867 cases for IGF-1/IGFBP-3 ratio) were included in this meta-analysis. The summary ORs of occurrent CRA for the highest versus lowest category of IGF-1, IGFBP-3 and IGF-1/IGFBP-3 ratio were 1.13 (95% CI: 0.95-1.34), 0.99 (0.84-1.16), and 1.05 (0.86-1.29), respectively. Higher IGF-1 and IGF-1/IGFBP-3 ratio were significantly associated with decreased risk of recurrent CRA (OR for IGF-1=0.60 [95% CI: 0.42-0.85]; IGF-1/IGFBP-3 ratio=0.65 [0.44-0.96]). A stratified analysis by advancement of occurrent CRA produced a significant summary OR of IGF-1 for advanced CRA (OR=2.21 [1.08-4.52]) but not for non-advanced CRA (OR=0.89 [0.55-1.45]). We did not find significant publication bias or heterogeneity.

CONCLUSION

Circulating levels of IGF-1, IGFBP-3 and their molar ratio were not associated with the risk of occurrence of CRA, but IGF-1 was associated with the increased risk for occurrence of advanced CRA.

Molecular Targets in Biliary Carcinogenesis and Implications for Therapy

Biliary tract cancers (BTCs) encompass a group of invasive carcinomas, including cholangiocarcinoma (intrahepatic, perihilar, or extrahepatic), and gallbladder carcinoma. Approximately 90% of patients present with advanced, unresectable disease and have a poor prognosis. The latest recommendation is to treat advanced or metastatic disease with gemcitabine and cisplatin, although chemotherapy has recorded modest survival benefits. Comprehension of the molecular basis of biliary carcinogenesis has resulted in experimental trials of targeted therapies in BTCs, with promising results. This review addresses the emerging role of targeted therapy in the treatment of BTCs. Findings from preclinical studies were reviewed and correlated with the outcomes of clinical trials that were undertaken to translate the laboratory discoveries.

IMPLICATIONS FOR PRACTICE

Biliary tract cancers are rare. Approximately 90% of patients present with advanced, unresectable disease and have a poor prognosis. Median overall and progression-free survival are 12 and 8 months, respectively. Because chemotherapy has recorded modest survival benefits, targeted therapies are being explored for personalized treatment of these cancers. A comprehensive review of targeted therapies in biliary tract cancers was undertaken to present emerging evidence from laboratory and/or molecular studies as they translate to clinical trials and outcomes. The latest evidence on this topic is presented to clinicians and practitioners to guide decisions on treatment of this disease.

ATF3 Mediates Anti-Cancer Activity of Trans-10, cis-12-Conjugated Linoleic Acid in Human Colon Cancer Cells

Conjugated linoleic acids (CLA) are a family of isomers of linoleic acid. CLA increases growth arrest and apoptosis of human colorectal cancer cells through an isomer-specific manner. ATF3 belongs to the ATF/CREB family of transcription factors and is associated with apoptosis in colorectal cancer. The present study was performed to investigate the molecular mechanism by which t10, c12-CLA stimulates ATF3 expression and apoptosis in human colorectal cancer cells. t10, c12-CLA increased an apoptosis in human colorectal cancer cells in dose dependent manner. t10, c12-CLA induced ATF3 mRNA and luciferase activity of ATF3 promoter in a dose-dependent manner. The responsible region for ATF3 transcriptional activation by t10, c12-CLA is located between −147 and −1850 of ATF3 promoter. mRNA stability of ATF3 was not affected by t10, c12-CLA treatment. t10, c12-CLA increases GSK3β expression and suppresses IGF-1-stimulated phosphorylation of Akt. The knockdown of ATF3 suppressed expression of GSK3β and NAG-1 and PARP cleavage. The results suggest that t10, c12-CLA induces apoptosis through ATF3-mediated pathway in human colorectal cancer cells.

Target identification of grape seed extract in colorectal cancer using drug affinity responsive target stability (DARTS) technique: role of endoplasmic reticulum stress response proteins

Various natural agents, including grape seed extract (GSE), have shown considerable chemopreventive and anti-cancer efficacy against different cancers in pre-clinical studies; however, their specific protein targets are largely unknown and thus, their clinical usefulness is marred by limited scientific evidences about their direct cellular targets. Accordingly, herein, employing, for the first time, the recently developed drug affinity responsive target stability (DARTS) technique, we aimed to profile the potential protein targets of GSE in human colorectal cancer (CRC) cells. Unlike other methods, which can cause chemical alteration of the drug components to allow for detection, this approach relies on the fact that a drug bound protein may become less susceptible to proteolysis and hence the enriched proteins can be detected by Mass Spectroscopy methods. Our results, utilizing the DARTS technique followed by examination of the spectral output by LC/MS and the MASCOT data, revealed that GSE targets endoplasmic reticulum (ER) stress response proteins resulting in overall down regulation of proteins involved in translation and that GSE also causes oxidative protein modifications, specifically on methionine amino acids residues on its protein targets. Corroborating these findings, mechanistic studies revealed that GSE indeed caused ER stress and strongly inhibited PI3k-Akt-mTOR pathway for its biological effects in CRC cells. Furthermore, bioenergetics studies indicated that GSE also interferes with glycolysis and mitochondrial metabolism in CRC cells. Together, the present study identifying GSE molecular targets in CRC cells, combined with its efficacy in vast pre-clinical CRC models, further supports its usefulness for CRC prevention and treatment.

IRS2 copy number gain, KRAS and BRAF mutation status as predictive biomarkers for response to the IGF-1R/IR inhibitor BMS-754807 in colorectal cancer cell lines

Insulin-like growth factor receptor 1 (IGF-1R)-targeting therapies are currently at an important crossroad given the low clinical response rates seen in unselected patients. Predictive biomarkers for patient selection are critical for improving clinical benefit. Coupling in vitro sensitivity testing of BMS-754807, a dual IGF-1R/IR inhibitor, with genomic interrogations in 60 human colorectal cancer cell lines, we identified biomarkers correlated with response to BMS-754807. The results showed that cell lines with BRAF(V600E) or KRAS(G13D) mutation were resistant, whereas cell lines with wild-type of both KRAS and BRAF were particularly sensitive to BMS-754807 if they have either higher RNA expression levels of IR-A or lower levels of IGFBP6. In addition, the cell lines with KRAS mutations, those with either insulin receptor substrate 2 (IRS2) copy number gain (CNG) or higher IGF-1R expression levels, were more sensitive to the drug. Furthermore, cell lines with IRS2 CNG had higher levels of ligand-stimulated activation of IGF-1R and AKT, suggesting that these cell lines with IGF-IR signaling pathways more actively coupled to AKT signaling are more responsive to IGF-1R/IR inhibition. IRS2 siRNA knockdown reduced IRS2 protein expression levels and decreased sensitivity to BMS-754807, providing evidence for the functional involvement of IRS2 in mediating the drug response. The prevalence of IRS2 CNG in colorectal cancer tumors as measured by qPCR-CNV is approximately 35%. In summary, we identified IRS2 CNG, IGF-1R, IR-A, and IGFBP6 RNA expression levels, and KRAS and BRAF mutational status as candidate predictive biomarkers for response to BMS-754807. This work proposed clinical development opportunities for BMS-754807 in colorectal cancer with patient selection to improve clinical benefit.

Figitumumab in patients with refractory metastatic colorectal cancer previously treated with standard therapies: a nonrandomized, open-label, phase II trial

PURPOSE

Figitumumab (CP-751,871) is a human IgG2 monoclonal antibody that binds and down-regulates insulin-like growth factor receptor-1 (IGF-1R) and inhibits activation of this receptor by IGF-1 and IGF-2. This nonrandomized, open-label, single-arm, phase II trial evaluated the antitumor activity and safety of figitumumab in patients with metastatic colorectal cancer that was refractory to ≥2 systemic therapies.

METHODS

Cohorts A and B received intravenous figitumumab 20 and 30 mg/kg in 3-week cycles, respectively. Both received loading doses (20 or 30 mg/kg) on days 1 and 2 of cycle 1. The primary endpoint was 6-month survival (null hypothesis for each cohort, H0: p6 mo surv = 0.45). Secondary endpoints included progression-free survival (PFS), overall survival (OS), objective response, safety, and pharmacokinetics.

RESULTS

A total of 168 patients (Cohort A, n = 85; Cohort B, n = 83) received figitumumab. Estimated 6-month survival was 49.4 % (95 % CI 38.8-60.0) in Cohort A and 44.1 % (95 % CI 33.4-54.9) in Cohort B. Median OS was 5.8 and 5.6 months, respectively; median PFS was 1.4 months in both cohorts. No objective partial or complete responses occurred. The respective rates of treatment discontinuation due to treatment-related adverse events (AEs) were 5 and 7 %. The most common grade 3/4 nonhematologic AEs in both cohorts were hyperglycemia and asthenia. No grade 4 hematologic laboratory abnormalities occurred. Most deaths were reported as due to progressive disease; none were due to figitumumab.

CONCLUSION

Six-month survival data do not support further study of figitumumab 20 or 30 mg/kg in this patient population.

In vivo analysis of insulin-like growth factor type 1 receptor humanized monoclonal antibody MK-0646 and small molecule kinase inhibitor OSI-906 in colorectal cancer

The development and characterization of effective anticancer drugs against colorectal cancer (CRC) is of urgent need since it is the second most common cause of cancer death. The study was designed to evaluate the effects of two IGF-1R antagonists, MK-0646, a recombinant fully humanized monoclonal antibody and OSI-906, a small molecule tyrosine kinase inhibitor on CRC cells. Xenograft study was performed on IGF-1R-dependent CRC cell lines for analyzing the antitumor activity of MK-0646 and OSI-906. Tumor proliferation and apoptosis were assessed using Ki67 and TUNEL assays, respectively. We also performed in vitro characterization of MK-0646 and OSI-906 treatment on CRC cells to identify mechanisms associated with drug-induced cell death. Exposure of the GEO and CBS tumor xenografts to MK-0646 or OSI-906 led to a decrease in tumor growth. TUNEL analysis showed an increase of approximately 45-55% in apoptotic cells in both MK-0646 and OSI-906 treated tumor samples. We report the novel finding that treatment with IGF-1R antagonists led to downregulation of X-linked inhibitor of apoptosis (XIAP) protein involved in cell survival and inhibition of cell death. In conclusion, IGF-1R antagonists (MK-0646 and OSI-906) demonstrated single agent inhibition of subcutaneous CRC xenograft growth. This was coupled to pro-apoptotic effects resulting in downregulation of XIAP and inhibition of cell survival. We report a novel mechanism by which MK-0646 and OSI-906 elicits cell death in vivo and in vitro. Moreover, these results indicate that MK-0646 and OSI-906 may be potential anticancer candidates for the treatment of patients with IGF-1R-dependent CRC.

Differential PKA activation and AKAP association determines cell fate in cancer cells

BACKGROUND

The dependence of malignant properties of colorectal cancer (CRC) cells on IGF1R signaling has been demonstrated and several IGF1R antagonists are currently in clinical trials. Recently, we identified a novel pathway in which cAMP independent PKA activation by TGFβ signaling resulted in the destabilization of survivin/XIAP complex leading to increased cell death. In this study, we evaluated the effect of IGF1R inhibition or activation on PKA activation and its downstream cell survival signaling mechanisms.

METHODS

Small molecule IGF1R kinase inhibitor OSI-906 was used to test the effect of IGF1R inhibition on PKA activation, AKAP association and its downstream cell survival signaling. In a complementary approach, ligand mediated activation of IGF1R was performed and AKAP/PKA signaling was analyzed for their downstream survival effects.

RESULTS

We demonstrate that the inhibition of IGF1R in the IGF1R-dependent CRC subset generates cell death through a novel mechanism involving TGFβ stimulated cAMP independent PKA activity that leads to disruption of cell survival by survivin/XIAP mediated inhibition of caspase activity. Importantly, ligand mediated activation of the IGF1R in CRC cells results in the generation of cAMP dependent PKA activity that functions in cell survival by inhibiting caspase activity. Therefore, this subset of CRC demonstrates 2 opposing pathways organized by 2 different AKAPs in the cytoplasm that both utilize activation of PKA in a manner that leads to different outcomes with respect to life and death. The cAMP independent PKA activation pathway is dependent upon mitochondrial AKAP149 for its apoptotic functions. In contrast, Praja2 (Pja2), an AKAP-like E3 ligase protein was identified as a key element in controlling cAMP dependent PKA activity and pro-survival signaling. Genetic manipulation of AKAP149 and Praja2 using siRNA KD had opposing effects on PKA activity and survivin/XIAP regulation.

CONCLUSIONS

We had identified 2 cytoplasmic pathways dependent upon the same enzymatic activity with opposite effects on cell fate in terms of life and death. Understanding the specific mechanistic functions of IGF1R with respect to determining the PKA survival functions would have potential for impact upon the development of new therapeutic strategies by exploiting the IGF1R/cAMP-PKA survival signaling in cancer.

Overcoming IGF1R/IR resistance through inhibition of MEK signaling in colorectal cancer models

PURPOSE

Results from clinical trials involving resistance to molecularly targeted therapies have revealed the importance of rational single-agent and combination treatment strategies. In this study, we tested the efficacy of a type 1 insulin-like growth factor receptor (IGF1R)/insulin receptor (IR) tyrosine kinase inhibitor, OSI-906, in combination with a mitogen-activated protein (MAP)-ERK kinase (MEK) 1/2 inhibitor based on evidence that the MAP kinase pathway was upregulated in colorectal cancer cell lines that were resistant to OSI-906.

EXPERIMENTAL DESIGN

The antiproliferative effects of OSI-906 and the MEK 1/2 inhibitor U0126 were analyzed both as single agents and in combination in 13 colorectal cancer cell lines in vitro. Apoptosis, downstream effector proteins, and cell cycle were also assessed. In addition, the efficacy of OSI-906 combined with the MEK 1/2 inhibitor selumetinib (AZD6244, ARRY-142886) was evaluated in vivo using human colorectal cancer xenograft models.

RESULTS

The combination of OSI-906 and U0126 resulted in synergistic effects in 11 of 13 colorectal cancer cell lines tested. This synergy was variably associated with apoptosis or cell-cycle arrest in addition to molecular effects on prosurvival pathways. The synergy was also reflected in the in vivo xenograft studies following treatment with the combination of OSI-906 and selumetinib.

CONCLUSIONS

Results from this study demonstrate synergistic antiproliferative effects in response to the combination of OSI-906 with an MEK 1/2 inhibitor in colorectal cancer cell line models both in vitro and in vivo, which supports the rational combination of OSI-906 with an MEK inhibitor in patients with colorectal cancer. Clin Cancer Res; 19(22); 6219-29. ©2013 AACR.

Hormone and cytokine circadian alteration in non-small cell lung cancer patients

Alterations in hormone secretion and cytokine levels have been evidenced in many neoplastic diseases. In this study we have evaluated the circadian profile of growth hormone (GH), insulin-like growth factor-1 (IGF-1), interleukin-2 (IL2), melatonin (MEL) and cortisol (COR) serum levels in non-small cell lung cancer patients. Blood was sampled every 4 h for 24 h in 11 healthy (H) men (ages 35-53 years) and 9 men with stage 2, 3 or 4 non-small cell lung cancer (C) (ages 43-63 years). Serum GH, total IGF1, IL2, MEL and COR were measured and examined for group differences, trends, and rhythm characteristics. 24-h means were significantly higher in C234 vs H for GH, GH/IGF1, IL2 and COR, and lower for IGF1, but IL2 and COR were not different for C23 vs H. A linear regression across 4 groups (H, C2, C3, C4) found a positive trend for COR, GH, GH/IGF1 and IL2, and a negative trend for IGF1. A linear regression run between the 24-h mean levels of GH, IGF1, COR, MEL and IL2 in healthy subjects evidenced a statistically significant positive trend between MEL and GH (R = 0.281, p = 0.022) and in cancer patients showed a statistically significant negative trend between GH and IGF1 (R = 0.332, p = 0.01), COR and IGF1 (R=0.430, p=0.001), and a statistically significant positive trend between the 24-h mean of COR and GH (R = 0.304, p = 0.02). Rhythms in MEL and COR (peaks near 01:00h and 08:00h, respectively) indicated identical synchronization to the light-dark cycle for both groups. A circadian rhythm was detected in GH and GH/IGF1 for C23 and H, with IGF1 and IL2 non-rhythmic in any group. In conclusion, an increasing trend and progressive loss of circadian rhythmicity in GH and GH/IGF1, an increasing trend in cortisol and IL2, and a decreasing trend in IGF1 in C, reflect a complex chain of events that could be involved in progression of neoplastic disease. A therapeutic strategy needs to take into account circadian patterns and complex interactions of the multiple functions that characterize the hormone and cytokine levels in the frame cancer progression.

Therapeutic targeting of the phosphatidylinositol 3-kinase signaling pathway: novel targeted therapies and advances in the treatment of colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the USA, and more effective treatment of CRC is therefore needed. Advances in our understanding of the molecular pathogenesis of this malignancy have led to the development of novel molecule-targeted therapies. Among the most recent classes of targeted therapies being developed are inhibitors targeting the phosphatidylinositol 3-kinase (PI3K) signaling pathway. As one of the most frequently deregulated pathways in several human cancers, including CRC, aberrant PI3K signaling plays an important role in the growth, survival, motility and metabolism of cancer cells. Targeting this pathway therefore has considerable potential to lead to novel and more effective treatments for CRC. Preclinical and early clinical studies have revealed the potential efficacy of drugs that target PI3K signaling for the treatment of CRC. However, a major challenge that remains is to study these agents in phase III clinical trials to see whether these early successes translate into better patient outcomes. In this review we focus on providing an up-to-date assessment of our current understanding of PI3K signaling biology and its deregulation in the molecular pathogenesis of CRC. Advances in available agents and challenges in targeting the PI3K signaling pathway in CRC treatment will be discussed and placed in the context of the currently available therapies for CRC.

Expression of various insulin-like growth factor-1 mRNA isoforms in colorectal cancer

Aim of the study

Several epidemiological studies have attempted to demonstrate a relationship between increased serum level of insulin-like growth factor 1 (IGF-1) and an augmented risk of developing colorectal cancers (CRC).

The human IGF-1 gene is composed of 6 exons and demonstrated expression of 6 different splice variants (isoforms) of mRNA (IA, IB, IC, IIA, IIB and IIC).

The aim of the study was to evaluate the expression of different isoforms of IGF-1 mRNA in CRC and normal colon tissue.

Material and methods

13 paired tissue specimens (colorectal tumor and non-tumor tissues) were analyzed using both quantitative polymerase chain reaction (PCR) and immunocytochemistry methods (IHC). The expression of classes I and II and variants A, B, C of IGF-1 mRNA were measured.

Results

In CRC higher amounts of IGF-1 class II mRNA than class I mRNA were detected. Among A, B, C isoforms, A variant of IGF-1 mRNA prevailed. The amounts of IGF-1 class I and class II mRNAs and of IGF-1 variant B mRNA were lowered in CRC as compared to the control. In CRC significant correlations were detected between reciprocal expression of class I and class II as well as between I and II isoforms and A, B and C.

Conclusions

Expression of IGF-1 mRNA isoforms differs between normal and CRC tissues. Even if all isoforms of IGF-1 mRNA manifested correlations with each other in tissues of CRC, expression of all transcripts (except that of isoform A) was significantly decreased as compared to the control.

Correlation between gene expression of IGF-1R pathway markers and cetuximab benefit in metastatic colorectal cancer

PURPOSE

This study examined potential correlations between markers related to the insulin-like growth factor-1 receptor (IGF-1R) pathway and clinical benefit from the anti-epidermal growth factor receptor (EGFR) monoclonal antibody cetuximab in metastatic colorectal cancer (mCRC).

EXPERIMENTAL DESIGN

Gene expression profiles for 70 pretreatment specimens from metastatic lesions of patients with chemorefractory mCRC receiving cetuximab monotherapy were analyzed using 74 predefined Gene-Chip probesets representing 33 unique IGF-1R pathway markers to determine correlations with progression-free survival (PFS) and disease control rate.

RESULTS

Higher IGF-1R, higher GRB(7), and lower INSIG(2) expression were associated with longer PFS with cetuximab in univariate analyses, particularly in patients with wild-type K-Ras tumors: median, 122 versus 60 days (P = 0.01), 122 versus 57 days (P = 0.011), and 57 versus 156 days (P < 0.0001), favoring higher IGF-1R, higher GRB(7), and lower INSIG(2) expression, respectively. Lower IGF-1 expression was associated with a PFS benefit with cetuximab, whereas lower IGFBP(3) and INSR expression levels showed trends for a PFS benefit. Lower INSIG(2) expression (vs. higher expression) was associated with greater PFS in the high epiregulin-expressing group (P = 0.001), but not in the low-expressing cohort suggesting an effect independent from the previously reported effect of epiregulin expression. Lower INSIG(2) expression was also associated with higher disease control rate in the overall population (51.4% vs. 11.4%; P = 0.001) and wild-type K-Ras subset (76.2% vs. 18.2%; P < 0.0001).

CONCLUSIONS

These results suggest that markers of the IGF-1R pathway may play a role in predicting benefit from cetuximab therapy in mCRC. Additional clinical studies are warranted to validate these findings.

Insulin-like growth factor: current concepts and new developments in cancer therapy

The insulin-like growth factor (IGF) family and the IGF-1 receptor (IGF-1R) play an important role in cancer. This intricate and complex signaling pathway provides many opportunities for therapeutic intervention, and several novel therapeutics aimed at the IGF-1R, particularly monoclonal antibodies and small molecule tyrosine kinase inhibitors, are under clinical investigation. This article provides a patent overview of the IGF signaling pathway and its complexity, addresses the justification for the use of IGF-1R-targeted therapy, and reviews the results of in vivo and in vitro novel therapeutics. Over the past year, the completion of several phase I, II, and III trials have provided interesting new information about the clinical activity of these novel compounds, particularly CP-751,871, IMC-A12, R1507, AMG-479, AVE-1642, MK-0646, XL-228, OSI-906, and BMS-754807. We review the important preliminary results from clinical trials with these compounds and conclude with a discussion about future therapeutic efforts.

Developmental stage determines estrogen receptor alpha expression and non-genomic mechanisms that control IGF-1 signaling and mammary proliferation in mice

Insulin like growth factor-1 (IGF-1) stimulates increased proliferation and survival of mammary epithelial cells and also promotes mammary tumorigenesis. To study the effects of IGF-1 on the mammary gland in vivo, we used BK5.IGF-1 transgenic (Tg) mice. In these mice, IGF-1 overexpression is controlled by the bovine keratin 5 promoter and recapitulates the paracrine exposure of breast epithelium to stromal IGF-1 that is seen in women. Studies have shown that BK5.IGF-1 Tg mice are more susceptible to mammary tumorigenesis than wild-type littermates. Investigation of the mechanisms underlying increased mammary cancer risk, reported here, revealed that IGF-1 preferentially activated the PI3K/Akt pathway in glands from prepubertal Tg mice, resulting in increased cyclin D1 expression and hyperplasia. However, in glands from postpubertal Tg mice, a pathway switch occurred and activation of the Ras/Raf/MAPK pathway predominated, without increased cyclin D1 expression or proliferation. We further showed that in prepubertal Tg glands, signaling was mediated by formation of an ERα/IRS-1 complex, which activated IRS-1 and directed signaling via the PI3K/Akt pathway. Conversely, in postpubertal Tg glands, reduced ERα expression failed to stimulate formation of the ERα/IRS-1 complex, allowing signaling to proceed via the alternate Ras/Raf/MAPK pathway. These in vivo data demonstrate that changes in ERα expression at different stages of development direct IGF-1 signaling and the resulting tissue responses. As ERα levels are elevated during the prepubertal and postmenopausal stages, these may represent windows of susceptibility during which increased IGF-1 exposure maximally enhances breast cancer risk.

Chronodisruption in lung cancer and possible therapeutic approaches

A customary temporal organization of physiological functions and biological processes is necessary to maintain body homeostasis and an altered body time structure may favour carcinogenesis. There is growing evidence that GH stimulates cancer growth, IGF1 may have a role in carcinogenesis and cancer promotion, GH-IGF1 axis, TRH, TSH, thyroxine, melatonin and cortisol modulate immune cell function and the immune system is often dysfunctional in patients with malignancies. The aim of our study was to evaluate GH-IGF1 axis, hypothalamus-pituitary-thyroid axis, melatonin, cortisol, lymphocyte subsets and IL2 in lung cancer patients. Peripheral blood samples were collected at 4-hour intervals in a 24-hour period from eleven healthy male subjects (age range 35-53 years) and nine male patients suffering from non-small cell lung cancer (age range 43-63 years). In each blood sample, lymphocyte subpopulations (CD3+, CD4+, CD8+, CD16+, CD20+, CD25+, HLA-DR+, γδTcR bearing cells) were analyzed and GH, IGF1, TRH, TSH, FT4, melatonin, cortisol and IL2 were measured. Circadian rhythmicity was evaluated and MESOR, amplitude and acrophase values were compared. In healthy subjects a significant circadian rhythm could be demonstrated with midday peaks for CD8+, CD16+, γδTCR expressing cells and cortisol, and peaks during the night for CD3+, CD4+, GH, TSH and melatonin. A borderline significant rhythm was also observed for CD20+, with a peak late in the evening. IGF1, TRH, FT4 and IL2 values did not show rhythmic variation. In cancer patients a significant circadian rhythm could be demonstrated with diurnal peak for CD16+ and peaks during the night for CD4+ and melatonin. GH, IGF1, TRH, TSH, FT4, cortisol and IL2 values did not show rhythmic variation. MESOR of CD8+ (P<0.0001), CD20+ (P=0.05), γδTCR expressing cells (P=0.01), IGF1 (P<0.001) and TSH (P=0.032) was higher in healthy subjects, whereas MESOR of CD16+ (P<0.0001), CD25+ (P=0.001), GH (P<0.001), TRH (P=0.002), FT4 (P=0.030), cortisol (P=0.01) and IL2 (P=0.02) was higher in cancer patients. Amplitude of circadian variation of γδTCR expressing cells (P=0.01), TSH (P<0.001) and cortisol (P=0.01) was higher in healthy subjects, whereas amplitude of circadian variation of CD4+ was higher in cancer patients (P=0.02). In conclusion, non-small cell lung cancer patients show severe alterations of periodic and quantitative characteristics of neuroendocrine and immune parameters with loss of circadian rhythmicity and internal desynchronization, leading to chronodisruption.

Dual targeting of the insulin-like growth factor and collateral pathways in cancer: combating drug resistance

The insulin-like growth factor pathway, regulated by a complex interplay of growth factors, cognate receptors, and binding proteins, is critically important for many of the hallmarks of cancer such as oncogenesis, cell division, growth, and antineoplastic resistance. Naturally, a number of clinical trials have sought to directly abrogate insulin-like growth factor receptor 1 (IGF-1R) function and/or indirectly mitigate its downstream mediators such as mTOR, PI3K, MAPK, and others under the assumption that such therapeutic interventions would provide clinical benefit, demonstrable by impaired tumor growth as well as prolonged progression-free and overall survival for patients. Though a small subset of patients enrolled within phase I or II clinical trials revealed dramatic clinical response to IGF-1R targeted therapies (most using monoclonal antibodies to IGF-1R), in toto, the anticancer effect has been underwhelming and unsustained, as even those with marked clinical responses seem to rapidly acquire resistance to IGF-1R targeted agents when used alone through yet to be identified mechanisms. As the IGF-1R receptor is just one of many that converge upon common intracellular signaling cascades, it is likely that effective IGF-1R targeting must occur in parallel with blockade of redundant signaling paths. Herein, we present the rationale for dual targeting of IGF-1R and other signaling molecules as an effective strategy to combat acquired drug resistance by carcinomas and sarcomas.

Therapy innovations: tyrosine kinase inhibitors for the treatment of pancreatic neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) show limited sensitivity to cytotoxic agents, requiring the search for novel therapies. Recently, data from a phase III trial demonstrated that sunitinib produces a clinically significant improvement in progression-free survival in patients with unresectable, advanced, or metastatic GEP-NETs. Based on this finding, sunitinib became the first targeted drug approved for the treatment of GEP-NETs, paving the way for the approval of other anticancer agents in this drug-orphan disease. To date, results of trials involving other multitargeted tyrosine kinase inhibitors, such as sorafenib, the monoclonal antibody bevacizumab, and insulin-like growth factor 1 receptor inhibitors, have also shown promising results, and some are already being studied in phase III trials. This review updates the results of ongoing trials using inhibitors of growth factors and tyrosine kinase receptors involved in the carcinogenesis of GEP-NETs.

IGF binding protein-3 treatment alters intestinal cell proliferation but not body weight of adult cystic fibrosis transmembrane conductance regulator deficient mice

The intestinal phenotype of cystic fibrosis (CF) transmembrane conductance regulator deficient mice includes altered cell homeostasis and a distended crypt-villus axis, which, in previous work, was inversely proportional to body weight. To investigate this correlation, herein, we treated CF mice with IGF binding protein-3 (IGFBP-3), a protein which, as it has potent effects on cell proliferation and apoptosis, we hypothesized would alter the intestinal cell homeostasis, and assessed body weight. Six-week-old C57BL/6JxBALB F2 CF and WT mice received recombinant human IGFBP-3 (rhIGFBP-3, 20 mg/kg) or vehicle treatment, and weight gain, serum protein levels, and intestinal histology were assessed. Administration of rhIGFBP-3 to CF mice significantly increased the number of Igfbp-3 positive cells in the intestine and partially reversed the hyperproliferative phenotype of intestinal crypts and muscularis externa, while not affecting apoptosis. Serum Igfbp-3 levels were increased, and Igf-I, albumin, and triglycerides measures were decreased in CF compared with WT mice. rhIGFBP-3 treatment significantly increased serum albumin and triglycerides but did not affect weight gain in CF mice. We have identified rhIGFBP-3 treatment to reduce intestinal cell proliferation, resulting in decreases in crypt depth and muscularis externa thickness in CF mice.

The colorectal cancer disease-specific transcriptome may facilitate the discovery of more biologically and clinically relevant information

BACKGROUND

To date, there are no clinically reliable predictive markers of response to the current treatment regimens for advanced colorectal cancer. The aim of the current study was to compare and assess the power of transcriptional profiling using a generic microarray and a disease-specific transcriptome-based microarray. We also examined the biological and clinical relevance of the disease-specific transcriptome.

METHODS

DNA microarray profiling was carried out on isogenic sensitive and 5-FU-resistant HCT116 colorectal cancer cell lines using the Affymetrix HG-U133 Plus2.0 array and the Almac Diagnostics Colorectal cancer disease specific Research tool. In addition, DNA microarray profiling was also carried out on pre-treatment metastatic colorectal cancer biopsies using the colorectal cancer disease specific Research tool. The two microarray platforms were compared based on detection of probesets and biological information.

RESULTS

The results demonstrated that the disease-specific transcriptome-based microarray was able to out-perform the generic genomic-based microarray on a number of levels including detection of transcripts and pathway analysis. In addition, the disease-specific microarray contains a high percentage of antisense transcripts and further analysis demonstrated that a number of these exist in sense:antisense pairs. Comparison between cell line models and metastatic CRC patient biopsies further demonstrated that a number of the identified sense:antisense pairs were also detected in CRC patient biopsies, suggesting potential clinical relevance.

CONCLUSIONS

Analysis from our in vitro and clinical experiments has demonstrated that many transcripts exist in sense:antisense pairs including IGF2BP2, which may have a direct regulatory function in the context of colorectal cancer. While the functional relevance of the antisense transcripts has been established by many studies, their functional role is currently unclear; however, the numbers that have been detected by the disease-specific microarray would suggest that they may be important regulatory transcripts. This study has demonstrated the power of a disease-specific transcriptome-based approach and highlighted the potential novel biologically and clinically relevant information that is gained when using such a methodology.

ChIP-seq and functional analysis of the SOX2 gene in colorectal cancers

SOX2 is an HMG box containing transcription factor that has been implicated in various types of cancer, but its role in colorectal cancers (CRC) has not been studied. Here we show that SOX2 is overexpressed in CRC tissues compared with normal adjacent tissues using immunohistochemical staining and RT-PCR. We also observed an increased SOX2 expression in nucleus of colorectal cancer tissues (46%, 14/30 cases vs. 7%, 2/30 adjacent tissues). Furthermore, knockdown of SOX2 in SW620 colorectal cancer cells decreased their growth rates in vitro cell line, and in vivo in xenograft models. ChIP-Seq analysis of SOX2 revealed a consensus sequence of wwTGywTT. An integrated expression profiling and ChIP-seq analysis show that SOX2 is involved in the BMP signaling pathway, steroid metabolic process, histone modifications, and many receptor-mediated signaling pathways such as IGF1R and ITPR2 (Inositol 1,4,5-triphosphate receptor, type 2).

The emerging role of insulin-like growth factor 1 receptor (IGF1r) in gastrointestinal stromal tumors (GISTs)

Recent years have seen a growing interest in insulin-like growth factor 1 receptor (IGF1R) in medical oncology. Interesting data have been reported also on IGF1r in gastrointestinal stromal tumors (GISTs) especially in children and in young adult patients whose disease does not harbour mutations on KIT and PDGFRA and are poorly responsive to conventional therapies. However, it is too early to reach conclusions on IGF1R as a novel therapeutic target in GIST because the receptor's biological role is still to be defined and the clinical significance in patients needs to be studied in larger studies. We update and comment the current literature on IGF1R in GISTs and discuss the future perspectives in this promising field.

The insulin-like growth factor I receptor/insulin receptor tyrosine kinase inhibitor PQIP exhibits enhanced antitumor effects in combination with chemotherapy against colorectal cancer models

PURPOSE

There is growing evidence implicating the importance of the insulin-like growth factor (IGF) pathway in colorectal cancer based upon the results of population studies and preclinical experiments. However, the combination of an IGF-I receptor (IGF-IR) inhibitor with standard colorectal cancer chemotherapies has not yet been evaluated. In this study, we investigated the interaction between PQIP, the dual IGF-IR/insulin receptor tyrosine kinase inhibitor, and standard chemotherapies in colorectal cancer cell line models.

EXPERIMENTAL DESIGN

The antiproliferative effects of PQIP, as a single agent and in combination with 5-fluorouracil, oxaliplatin, or SN38, were analyzed against four colorectal cancer cell lines. Downstream effector proteins, apoptosis, and cell cycle were also assessed in the combination of PQIP and SN-38. Lastly, the efficacy of OSI-906 (a derivative of PQIP) combined with irinotecan was further tested using a human colorectal cancer xenograft model.

RESULTS

Treatment with the combination of PQIP and each of three chemotherapies resulted in an enhanced decrease in proliferation of all four colorectal cancer cell lines compared with single-agent treatment. This inhibition was not associated with a significant induction of apoptosis, but was accompanied by cell cycle arrest and changes in phosphorylation of Akt. Interestingly, antitumor activity between PQIP and SN-38 in vitro was also reflected in the human colorectal cancer xenograft model.

CONCLUSIONS

Combination treatment with PQIP, the dual IGF-IR/insulin receptor tyrosine kinase inhibitor, and standard colorectal cancer chemotherapy resulted in enhanced antiproliferative effects against colorectal cancer cell line models, providing a scientific rationale for the testing of OSI-906 and standard colorectal cancer treatment regimens.

Insulin-like growth factor 1 expression correlates with clinical outcome in K-RAS wild type colorectal cancer patients treated with cetuximab and irinotecan

Seventy to 40% of K-RAS wild type colorectal tumors does not seem to benefit from treatment with antiepidermal growth factor receptor (anti-EGFR) monoclonal antibodies. Recent data suggested that in presence of IGF-1 system, altered activation colorectal cancer cells may escape anti-EGFR mediated cell death. The interaction between IGF-1 expression and K-RAS mutational analysis was tested to verify the ability of IGF-1 to identify a subgroup of patients more likely to benefit from EGFR-targeted antibodies treatment. IGF-1 expression and K-RAS mutational status was assessed in advanced colorectal cancer patients receiving irinotecan/cetuximab. One hundred twelve patients were analyzed. IGF-1 was negative in 30 patients (27%) and overexpressed in the remaining 82 cases (73%). In IGF-1 negative and IGF-1 positive tumors, we observed progressive disease in 9 (30%) and 55 (67%) patients, respectively (p = 0.001). Median progression-free survival was 7.5 mo in patients showing IGF-1 negative tumors and 3 mo for IGF-1 expressing tumors (p = 0.002). Among K-RAS wild type patients, IGF-1 negative and positive tumors showed a partial response to cetuximab-irinotecan in 13 (65%) and 11 (22%) cases, respectively (p = 0.002). Median progression-free survival in IGF-1 negative tumors was 10 mo and 3.2 mo in IGF-1 positive colorectal cancers (p = 0.02). IGF-1 proved to be a possible predictive factor for resistance to anti-EGFR monoclonal antibodies in K-RAS wild type colorectal cancer. Combined IGF-1 and K-RAS analysis may represent an effective strategy for a better selection of responding colorectal cancer patients.

ChIP-seq and Functional Analysis of the SOX2 Gene in Colorectal Cancers

Abstract SOX2 is a high mobility group (HMG) box containing transcription factor that has been implicated in various types of cancer, but its role in colorectal cancers (CRC) has not been studied. Here we show that SOX2 is overexpressed in CRC tissues compared with normal adjacent tissues using immunohistochemical staining and RT-PCR. We also observed an increased SOX2 expression in nucleus of colorectal cancer tissues (46%, 14/30 cases vs. 7%, 2/30 adjacent tissues). Furthermore, knockdown of SOX2 in SW620 colorectal cancer cells decreased their growth rates in vitro cell line, and in vivo in xenograft models. ChIP-seq analysis of SOX2 revealed a consensus sequence of wwTGywTT. An integrated expression profiling and ChIP-seq analysis show that SOX2 is involved in the BMP signaling pathway, steroid metabolic process, histone modifications, and many receptor-mediated signaling pathways such as IGF1R and ITPR2 (Inositol 1,4,5-triphosphate receptor, type 2).

Tea catechins as inhibitors of receptor tyrosine kinases: mechanistic insights and human relevance

Receptor tyrosine kinases (RTKs) play important roles in the control of fundamental cellular processes, influencing the balance between cell proliferation and death. RTKs have emerged as molecular targets for the treatment of various cancers. Green tea and its polyphenolic compounds, the catechins, exhibit chemopreventive and chemotherapeutic properties in many human cancer cell types, as well as in various carcinogenicity models in vivo. Epidemiological studies are somewhat less convincing, but some positive correlations have been observed. The tea catechins, including (-)-epigallocatechin-3-gallate (EGCG), have pleiotropic effects on cellular proteins and signaling pathways. This review focuses on the ability of the tea constituents to suppress RTK signaling, and summarizes the mechanisms by which EGCG and other catechins might exert their protective effects towards dysregulated RTKs in cancer cells. The findings are discussed in the context of ongoing clinical trials with RTK inhibitors, and the possibility for drug/nutrient interactions enhancing therapeutic efficacy.

The rationale and development of therapeutic insulin-like growth factor axis inhibition for lung and other cancers

The insulin-like growth factor (IGF) axis involves elements of endocrine, paracrine, and autocrine control. It is centrally involved in normal development and growth. Core signaling is driven through the IGF-1 receptor (IGF-1R) in either homo-multimeric complexes or hetero-multimeric complexes with the insulin receptor (IR). Signaling is affected by a large number of upstream and downstream factors, including the differential expression of various intracellular IR substrates, a range of stimulatory ligands (insulin, IGF-1, and IGF-2), the expression of specific clearance receptors (eg, IGF-2R), and different IGF-binding proteins. Considerable evidence exists to implicate aspects of the IGF axis in the development and maintenance of many different nonneoplastic and neoplastic diseases, including both small-cell lung cancer and non-small-cell lung cancer (NSCLC). A large number of different anticancer strategies directed against the IGF axis are being developed. Monoclonal antibodies directed against the IGF-1R are the furthest advanced clinically. Hyperglycemia appears to be a class effect. To date, the major difference among the antibodies used in clinical trials seems to be their plasma half-lives, leading to a number of different administration regimens being taken forward. Early signals of monotherapy activity have been notably reported in patients with Ewing sarcoma and in several other cancers. Encouraging increases in the NSCLC response rate have already been reported after the addition of an anti-IGF-1R antibody to first-line carboplatin and paclitaxel. Explorations of aspects of ligands, binding proteins, receptors, and receptor substrates are all ongoing to identify potential biomarkers predictive of benefit from IGF axis intervention.

Dissociation of EphB2 signaling pathways mediating progenitor cell proliferation and tumor suppression

Signaling proteins driving the proliferation of stem and progenitor cells are often encoded by proto-oncogenes. EphB receptors represent a rare exception; they promote cell proliferation in the intestinal epithelium and function as tumor suppressors by controlling cell migration and inhibiting invasive growth. We show that cell migration and proliferation are controlled independently by the receptor EphB2. EphB2 regulated cell positioning is kinase-independent and mediated via phosphatidylinositol 3-kinase, whereas EphB2 tyrosine kinase activity regulates cell proliferation through an Abl-cyclin D1 pathway. Cyclin D1 regulation becomes uncoupled from EphB signaling during the progression from adenoma to colon carcinoma in humans, allowing continued proliferation with invasive growth. The dissociation of EphB2 signaling pathways enables the selective inhibition of the mitogenic effect without affecting the tumor suppressor function and identifies a pharmacological strategy to suppress adenoma growth.

The IGF-1/IGF-1R signaling axis in the skin: a new role for the dermis in aging-associated skin cancer

The appropriate response of human keratinocytes to UVB is dependent on the activation status of the IGF-1 receptor. Keratinocytes grown in conditions where the IGF-1 receptor is inactive, inappropriately replicate in the presence of UVB-induced DNA damage. In human skin epidermal keratinocytes do not express IGF-1, so the IGF-1 receptor on keratinocytes is activated by IGF-1 secreted from dermal fibroblasts. We now demonstrate that the IGF-1 produced by human fibroblasts is essential for the appropriate UVB response of keratinocytes. Furthermore, the expression of IGF-1 is silenced in senescent fibroblasts in vitro. Using quantitative RT-PCR and immunohistochemisty, we can demonstrate that IGF-1 expression is also silenced in geriatric dermis in vivo. The diminished IGF-1 expression in geriatric skin correlates with an inappropriate UVB response in geriatric volunteers. Finally, the appropriate UVB response is restored in geriatric skin in vivo via pretreatment with exogenous IGF-1. These studies provide further evidence for a role of the IGF-1R in suppressing UVB-induced carcinogenesis, suggest that fibroblasts play a critical role in maintaining appropriate activation of the keratinocyte IGF-1R, and imply that reduced expression of IGF-1 in geriatric skin could be an important component in the development of aging-related non-melanoma skin cancer.

Design of an insulin analog with enhanced receptor binding selectivity: rationale, structure, and therapeutic implications

Insulin binds with high affinity to the insulin receptor (IR) and with low affinity to the type 1 insulin-like growth factor (IGF) receptor (IGFR). Such cross-binding, which reflects homologies within the insulin-IGF signaling system, is of clinical interest in relation to the association between hyperinsulinemia and colorectal cancer. Here, we employ nonstandard mutagenesis to design an insulin analog with enhanced affinity for the IR but reduced affinity for the IGFR. Unnatural amino acids were introduced by chemical synthesis at the N- and C-capping positions of a recognition alpha-helix (residues A1 and A8). These sites adjoin the hormone-receptor interface as indicated by photocross-linking studies. Specificity is enhanced more than 3-fold on the following: (i) substitution of Gly(A1) by D-Ala or D-Leu, and (ii) substitution of Thr(A8) by diaminobutyric acid (Dab). The crystal structure of [D-Ala(A1),Dab(A8)]insulin, as determined within a T(6) zinc hexamer to a resolution of 1.35 A, is essentially identical to that of human insulin. The nonstandard side chains project into solvent at the edge of a conserved receptor-binding surface shared by insulin and IGF-I. Our results demonstrate that modifications at this edge discriminate between IR and IGFR. Because hyperinsulinemia is typically characterized by a 3-fold increase in integrated postprandial insulin concentrations, we envisage that such insulin analogs may facilitate studies of the initiation and progression of cancer in animal models. Future development of clinical analogs lacking significant IGFR cross-binding may enhance the safety of insulin replacement therapy in patients with type 2 diabetes mellitus at increased risk of colorectal cancer.

Dual silencing of insulin-like growth factor-I receptor and epidermal growth factor receptor in colorectal cancer cells is associated with decreased proliferation and enhanced apoptosis

Overexpression and activation of tyrosine kinase receptors are common features of colorectal cancer. Using the human colorectal cancer cell lines DLD-1 and Caco-2, we evaluated the role of the insulin-like growth factor-I (IGF-I) receptor (IGF-IR) and epidermal growth factor receptor (EGFR) in cellular functions of these cells. We used the small interfering RNA (siRNA) technology to specifically down-regulate IGF-IR and EGFR expression. Knockdown of IGF-IR and EGFR resulted in inhibition of cell proliferation of DLD-1 and Caco-2 cells. An increased rate of apoptosis was associated with siRNA-mediated silencing of IGF-IR and EGFR as assessed by activation of caspase-3/caspase-7. The combined knockdown of both EGFR and IGF-IR decreased cell proliferation and induced cell apoptosis more effectively than did silencing of either receptor alone. Comparable effects on cell proliferation and apoptosis were observed after single and combinational treatment of cells by the IGF-IR tyrosine kinase inhibitor NVP-AEW541 and/or the EGFR tyrosine kinase inhibitor erlotinib. Combined IGF-IR and EGFR silencing by either siRNAs or tyrosine kinase inhibitors diminished the phosphorylation of downstream signaling pathways AKT and extracellular signal-regulated kinase (ERK)-1/2 more effectively than did the single receptor knockdown. Single IGF-IR knockdown inhibited IGF-I-dependent phosphorylation of AKT but had no effect on IGF-I- or EGF-dependent phosphorylation of ERK1/2, indicating a role of EGFR in ligand-dependent ERK1/2 phosphorylation. The present data show that inhibition of the IGF-IR transduction cascade augments the antipoliferative and proapoptotic effects of EGFR inhibition in colorectal cancer cells. A clinical application of combination therapy targeting both EGFR and IGF-IR could be a promising therapeutic strategy.

Customizing the targeting of IGF-1 receptor

The type 1 IGF receptor (IGF-IR) is activated by two ligands, IGF-1 and IGF-2, and by insulin at supraphysiological concentrations. It plays a significant role in the growth of normal and abnormal cells, and antibodies against the IGF-IR are now in clinical trials. Targeting of the IGF-IR in cancer cells (by antibodies or other means) can be improved by the appropriate selection of responsive tumors. This review focuses on the optimization of IGF-IR targeting in human cancer.

Autologous bone marrow stromal cells genetically engineered to secrete an igf-I receptor decoy prevent the growth of liver metastases

Liver metastases respond poorly to current therapy and remain a frequent cause of cancer-related mortality. We reported previously that tumor cells expressing a soluble form of the insulin-like growth factor-I receptor (sIGFIR) lost the ability to metastasize to the liver. Here, we sought to develop a novel therapeutic approach for prevention of hepatic metastasis based on sustained in vivo delivery of the soluble receptor by genetically engineered autologous bone marrow stromal cells. We found that when implanted into mice, these cells secreted high plasma levels of sIGFIR and inhibited experimental hepatic metastases of colon and lung carcinoma cells. In hepatic micrometastases, a reduction in intralesional angiogenesis and increased tumor cell apoptosis were observed. The results show that the soluble receptor acted as a decoy to abort insulin-like growth factor-I receptor (IGF-IR) functions during the early stages of metastasis and identify sustained sIGFIR delivery by cell-based vehicles as a potential approach for prevention of hepatic metastasis.