Insulin-like growth factor-I receptor signaling and resistance to trastuzumab (Herceptin).

BACKGROUND: Trastuzumab (Herceptin), an anti-HER2/neu receptor monoclonal antibody that inhibits growth of ErbB2-overexpressing breast cancer, is used to treat such cancers. Development of resistance to trastuzumab, however, is common. We investigated whether insulin-like growth factor-I (IGF-I), which activates cell survival signals, interferes with the growth-inhibitory action of trastuzumab. METHODS: MCF-7/HER2-18 and SKBR3 human breast cancer models were used to assess cell proliferation, colony formation in soft agar, and cell cycle parameters. Throughout, we used trastuzumab at a dose of 10 microg/mL and IGF-I at a dose of 40 ng/mL. All statistical tests were two-sided. RESULTS: Trastuzumab inhibited the growth of MCF-7/HER2-18 cells, which overexpress HER2/neu receptors and express IGF-I receptors (IGF-IRs), only when IGF-IR signaling was minimized. For example, in 1% fetal bovine serum (FBS), trastuzumab reduced cell proliferation by 42% (P =.002); however, in 10% FBS or IGF-I, trastuzumab had no effect on proliferation. In SKBR3 cells, which overexpress HER2/neu receptor but express few IGF-IRs, trastuzumab reduced proliferation by 42% (P =.008) regardless of IGF-I concentration. When SKBR3 cells were genetically altered to overexpress IGF-IRs and cultured with IGF-I, trastuzumab had no effect on proliferation. However, the addition of IGF-binding protein-3, which decreased IGF-IR signaling, restored trastuzumab-induced growth inhibition. CONCLUSIONS: In breast cancer cell models that overexpress HER2/neu, an increased level of IGF-IR signaling appears to interfere with the action of trastuzumab. Thus, strategies that target IGF-IR signaling may prevent or delay development of resistance to trastuzumab.     

Insulin-like growth factor-I signaling in human neuroblastoma cells

Neuroblastoma is a heterogeneous tumor consisting of N (neuronal) and S (stromal) cells. We report that more tumorigenic and motile N cells express higher levels of IGF-I receptor (IGF-IR) than less tumorigenic, more adherent S cells. Shc, one of the two major docking partners of IGF-IR, is equally expressed in N and S cell lines. IGF-I treatment phosphorylates Shc in N cells, but only weakly activates Shc in S cells. Expression of the second partner, insulin receptor substrate (IRS), is cell type specific. S cells exclusively express IRS-1 that undergoes sustained phosphorylation by IGF-I. In contrast, N cells express IRS-2 that is transiently phosphorylated by IGF-I. Downstream of IRS-2 and Shc, IGF-I treatment results in strong activation of Akt and MAPK in N cells and activation of both pathways is required for IGF-I-mediated differentiation. Only IGF-IR activation of phosphatidylinositol-3 kinase is required for tumor edge ruffling in N and S cells, with stimulation of focal adhesion kinase (FAK) and paxillin. This detailed understanding of the 'biochemical signature' of N and S cells provides the background needed to target and disrupt specific IGF signaling pathways in an attempt to develop more effective therapies.     

Insulin-like growth factor-I receptor expression regulates neuroblastoma metastasis to bone

Neuroblastoma is a pediatric tumor that preferentially metastasizes to bone. Patients with bone metastases have a mortality rate >93%, indicating a need for novel treatment targets. Our laboratory has shown that type I insulin-like growth factor receptor (IGF-IR) expression and activation regulate neuroblastoma cell proliferation, motility, invasion, and survival, and that expression of the IGF-IR correlates with neuroblastoma tumorigenicity. Bone expresses large amounts of IGF ligands, and the IGF system is required for normal bone physiology. The current study addresses the role of the IGF system in neuroblastoma metastasis to bone. Upon reaching the bone marrow through the circulation, neuroblastoma cells must dock at the bone marrow endothelium, extravasate into the bone microenvironment, and destroy bone tissue to allow for tumor growth. This report examines the effects of high IGF-IR expression on neuroblastoma cell interaction with bone. The current data show that neuroblastoma cells with high IGF-IR expression, either endogenously or through transfection, adhere to human bone marrow endothelial cells and subsequently migrate toward both IGF-I and human bone stromal cells. High IGF-IR-expressing neuroblastoma cells adhere tightly to bone stromal cells, flatten, and extend processes. When neuroblastoma cells are injected directly into the tibiae of mice, those cells with increased IGF-IR form both osteolytic lesions within the tibiae and secondary tumors within other sites. These results support the hypothesis that IGF-IR expression in neuroblastoma cells increases tumor cell interaction with the bone microenvironment, resulting in greater formation of metastases.     

Insulin-like growth factor-I receptor activation blocks doxorubicin cytotoxicity in sarcoma cells

More than 80% of patients with extremity sarcoma ultimately develop metastases to pulmonary sites. Doxorubicin alone or in combination with other chemotherapeutic agents may result in partial or complete tumor response for sarcoma pulmonary metastases. Regardless of the response, there has been no proven survival benefit from cytotoxic chemotherapy in the treatment of localized or metastatic soft tissue sarcoma. Insulin-like growth factor-I receptor (IGF-I-R) activation may contribute to resistance to chemotherapy in mesenchymal neoplasia. IGF-I-R activation by its ligand decreases in vitro cytotoxic response of sarcoma to doxorubicin, the most active agent against soft tissue sarcoma in adults. Furthermore, IGF-I-R is frequently overexpressed in soft tissue sarcoma and may predict poor response to traditional chemotherapy. The effect of doxorubicin on a human soft tissue sarcoma cell derived from a dedifferentiated lung metastasis was evaluated using titrated doxorubicin doses with and without exogenous IGF-I (100 ng/ml). Western blot analysis was performed to evaluate levels of phosphorylated IGF-I-R under control and experimental conditions. In vitro proliferation assays were performed. Nuclear activation through IGF-I receptor mediated pathways prior to exposing sarcoma cells to doxorubicin altered the pattern of response to doxorubicin with enhanced mitogenesis (>2-fold) and blunted doxorubicin cytotoxicity (>10% change in IC50). These data suggest that activation of IGF-I receptor in sarcoma cells is a potential mechanism for tumor resistance to doxorubicin. Inhibition of IGF-I receptor activation represents a novel approach to enhance the degree and duration of response to traditional chemotherapy against soft tissue sarcoma.     

Insulin-like growth factor-I receptor activity is essential for Kaposi's sarcoma growth and survival

Kaposi's sarcoma (KS) is a highly vascular tumour and is the most common neoplasm associated with human immunodeficiency virus (HIV-1) infection. Growth factors, in particular vascular endothelial growth factor (VEGF), have been shown to play an important role in its development. The role of insulin-like growth factors (IGFs) in the pathophysiology of different tumours led us to evaluate the role of IGF system in KS. The IGF-I receptors (IGF-IR) were identified by immunohistochemistry in biopsies taken from patients with different AIDS/HIV-related KS stages and on KSIMM cells (an established KS-derived cell line). Insulin-like growth factor-I is a growth factor for KSIMM cells with a maximum increase of 3H-thymidine incorporation of 130 +/- 27.6% (P < 0.05) similar to that induced by VEGF and with which it is additive (281 +/- 13%) (P < 0.05). Moreover, specific blockade of the receptor (either by alpha IR3 antibody or by picropodophyllin, a recently described selective IGF-IR tyrosine phosphorylation inhibitor) induced KSIMM apoptosis, suggesting that IGF-IR agonists (IGF-I and -II) mediate antiapoptotic signals for these cells. We were able to identify an autocrine loop essential for KSIMM cell survival in which IGF-II is the IGF-IR agonist secreted by the cells. In conclusion, IGF-I pathway inhibition is a promising therapeutical approach for KS tumours.     

Insulin-like growth factor-I receptor/human epidermal growth factor receptor 2 heterodimerization contributes to trastuzumab resistance of breast cancer cells

The majority of breast cancer patients who achieve an initial therapeutic response to the human epidermal growth factor receptor 2 (HER-2)-targeted antibody trastuzumab will show disease progression within 1 year. We previously reported the characterization of SKBR3-derived trastuzumab-resistant pools. In the current study, we show that HER-2 interacts with insulin-like growth factor-I receptor (IGF-IR) uniquely in these resistant cells and not in the parental trastuzumab-sensitive cells. The occurrence of cross talk between IGF-IR and HER-2 exclusively in resistant cells is evidenced by the IGF-I stimulation resulting in increased phosphorylation of HER-2 in resistant cells, but not in parental cells, and by the inhibition of IGF-IR tyrosine kinase activity leading to decreased HER-2 phosphorylation only in resistant cells. In addition, inhibition of IGF-IR tyrosine kinase activity by I-OMe-AG538 increased sensitivity of resistant cells to trastuzumab. HER-2/IGF-IR interaction was disrupted on exposure of resistant cells to the anti-IGF-IR antibody alpha-IR3 and, to a lesser extent, when exposed to the anti-HER-2 antibody pertuzumab. Heterodimer disruption by alpha-IR3 dramatically restored sensitivity to trastuzumab and resistant cells showed a slightly increased sensitivity to pertuzumab versus parental cells. Neither alpha-IR3 nor pertuzumab decreased HER-2 phosphorylation, suggesting that additional sources of phosphorylation other than IGF-IR exist when HER-2 and IGF-IR are not physically bound. Our data support a unique interaction between HER-2 and IGF-IR in trastuzumab-resistant cells such that cross talk occurs between IGF-IR and HER-2. These data suggest that the IGF-IR/HER-2 heterodimer contributes to trastuzumab resistance and justify the need for further studies examining this complex as a potential therapeutic target in breast cancers that have progressed while on trastuzumab.     

Insulin-like growth factor-I and prostate cancer: a meta-analysis

Some, but not all, epidemiological found have shown that high circulating levels of insulin-like growth factor-I (IGF-I) are associated with an increased risk of prostate cancer. We performed a meta-analysis on all the studies reported so far to evaluate this association. In our Medline search, 14 case-control studies were identified. A standard protocol abstracted information for each study. Hedges' standardized mean difference (HSMD) and odds ratio (OR) were used to estimate the effect of IGF-I and IGF-binding proteins (IGFBP-3). The combined data showed that circulating levels of IGF-I were significantly higher in prostate cancer patients (HSMD = 0.194). The OR for prostate cancer was 1.47 (95% confidence interval (CI) 1.23-1.77) among men with high IGF-I compared to those with low IGF-I. The OR was 1.26 (95% CI 1.03-1.54) for IGFBP-3. Circulating levels of IGF-I and IGFBP-3 are likely to be higher in prostate cancer patients than in the controls. These findings support the suggestion that high IGF-I and IGFBP-3 are associated with an increased risk of prostate cancer.     

Insulin-like growth factor-I receptor blockade reduces tumor angiogenesis and enhances the effects of bevacizumab for a human gastric cancer cell line, MKN45

BACKGROUND:

Insulin‐like growth factor (IGF)‐I receptor (IGF‐IR) signaling is required for tumorigenicity and tumor progression of gastrointestinal cancers. The authors previously reported the success of therapy for gastrointestinal cancers using adenoviruses that expressed dominant‐negative IGF‐IR (IGF‐IR/dn). In addition, it has been demonstrated that IGF‐IR signaling affects vascular endothelial growth factor (VEGF) expression in some other types of tumors. The objective of the current study was to evaluate this interaction by studying the roles of IGF‐IR in tumor angiogenesis and lymphangiogenesis and their implications for targeted therapy in gastric cancer.

METHODS:

The impact of IGF signals on the expression of VEGF‐A and VEGF‐C in a human gastric cancer cell, MKN45, and vascular formation were assessed. The effects of IGF‐IR/dn with or without bevacizumab on angiogenesis, lymphangiogenesis, and tumor suppression in mouse xenografts were assessed.

RESULTS:

IGFs induced the expression of VEGF ligands and up‐regulated in vitro vascular vessel formation. IGF‐IR/dn reduced VEGF expression, reduced the activation of both protein kinase B (Akt) and mitogen‐activated protein kinase (MAPK), and reduced vascular formation, indicating that IGF‐IR/dn inhibited tumor growth in mice by inhibiting both angiogenesis and lymphangiogenesis. However, IGF‐IR/dn did not affect either blood sugar or body weight in these mice. The combination of IGF‐IR/dn and bevacizumab was highly effective against these xenograft tumors, and only this combination resulted in the complete regression of 43% of tumors, reduced the expression of VEGF, and induced apoptosis.

CONCLUSIONS:

The current results indicated that IGF‐IR is involved in angiogenesis and lymphangiogenesis through the modulation of VEGF ligand expression in the gastric cancer cell line MKN45. Targeting IGF‐IR in combination with agents that block the VEGF pathway may have therapeutic utility for gastric cancer therapy. Cancer 2011. © 2011 American Cancer Society.     

Insulin-like growth factor-I receptor antagonism results in increased cytotoxicity of breast cancer cells to doxorubicin and taxol

Therapeutic strategies for patients with advanced-stage adenocarcinoma of the breast frequently include the use of cytotoxic chemotherapy. Insulin-like growth factor I (IGF-I) receptor, a key factor in cell-cycle regulation, is frequently overexpressed in high-grade breast cancers. IGF-I receptor overexpression in these tumors may provide a target for novel molecular therapy against this disease. Early passage samples of estrogen-responsive (ER+) MCF 7 and estrogen receptor-negative (ER-) MDA-231 cells were cultured in semi-confluent conditions. Dose-titrations were performed for doxorubicin and taxol with receptor modulation using IGF-I or a competitive receptor inhibitor, alphaIR3. The addition of 100 ng/ml IGF-I resulted in a >2-fold mitogenic response in both ER+ and ER- cells. Receptor activation prior to the treatment with cytotoxic chemotherapeutic agents altered the pattern of response with a 26.3% increase in IC50. Doxorubicin and taxol both produced dose-related toxicity with IC50 of 0.05 microg/ml and 0.00 microg/ml respectively. The addition of alphaIR3 resulted in increased cytotoxicity in IGF-I stimulated cells compared with the use of doxorubicin or taxol alone. These results suggest that IGF-I receptor modulation alters the response to cytotoxic chemotherapeutic agents in breast cancer cells.     

Insulin-like growth factor-I and risk of high-grade cervical intraepithelial neoplasia.

Insulin-like growth factors (IGF) and their binding proteins (IGFBP) have been implicated in the risk of several epithelial or glandular tumors, including prostate cancer, breast cancer, and colon cancer. Cervical cancer, which is also of epithelial origin, has been shown to overexpress receptors for IGF-I, and plasma levels of IGF-I have been positively associated with cervical cancer precursors in one epidemiologic study. In this case-control study, we investigated plasma levels of IGF-I and IGFBP-3 in relation to the risk of histologically confirmed high-grade cervical intraepithelial neoplasia (HGCIN) and the risk of human papillomavirus (HPV) infection. Included in this analysis were 329 cases and 621 controls recruited from clinics affiliated with two Montréal-area hospital centers. We observed a reduced risk of HGCIN for increasing levels of IGF-I, with an adjusted odds ratio (OR) of 0.40 (95% confidence interval, 0.19-0.87) for the highest quartile relative to the lowest quartile of IGF-I. No association was observed between IGFBP-3 levels and HGCIN. Among controls, IGF-I was associated with a decreased risk of being positive for HPV-16 or HPV-18, with an adjusted odds ratio of 0.20 (95% confidence interval, 0.05-0.87) for the highest quartile relative to the lowest quartile of IGF-I. There was no association observed between IGFBP-3 levels and HPV infection status. IGF-I-mediated effects seemed to predominate among women <30 years of age. In contrast to the previously reported study, our results suggest that levels of IGF-I in young women may be inversely associated with HGCIN, a precursor to cervical cancer.     

Genetic blockade of the insulin-like growth factor-I receptor: a promising strategy for human pancreatic cancer

Pancreatic cancer is one of the most lethal malignant tumors. Insulin-like growth factor (IGF)-I receptor (IGF-Ir) signaling is required for maintenance of growth and tumorigenicity of many tumors, but this pathway has not been well studied in pancreatic cancer. We have shown previously successful therapy in colorectal and lung cancer xenograft models using recombinant adenoviruses expressing dominant negative IGF-I receptors. In this study, we sought to better dissect the mechanism of action of this virus and determine whether IGF-Ir targeted adenoviruses represent potentially effective therapeutics for human pancreatic cancer cells. Truncated IGF-I receptors (IGF-Ir/dn; 482 and 950 amino acids long, respectively, IGF-Ir/482st and IGF-Ir/950st) that function as dominant negative inhibitor were cloned into recombinant adenoviruses and used to treat human pancreatic cancer cells. We assessed the effect of IGF-Ir/dn on signaling blockade, growth, stress response, chemotherapy, radiation-induced apoptosis, and in vivo therapeutic efficacy in xenografts. IGF-Ir/dn expression suppressed tumorigenicity both in vitro and in vivo and up-regulated stressor-induced apoptosis. It effectively blocked both IGF-I and IGF-II-induced activation of Akt-1. IGF-Ir/dn expression increased radiation and chemotherapy-induced apoptosis, and the combination therapy of IGF-Ir/dn with chemotherapy was very effective against tumors in mice. In an i.p. model, IGF-Ir/dn therapy reduced dissemination and prolonged survival times. Moreover, IGF-Ir/482st was more effective than IGF-Ir/950st because of its bystander effect. The antitumor activity of IGF-Ir/dn is mediated through inhibition of Akt-1 and enhances the efficacy of chemotherapy. Adenovirus-IGF-Ir/482st may be a useful anticancer therapeutic for pancreatic cancer.     

Insulin-like growth factor-I gene polymorphism and breast cancer risk in Chinese women

The evidence that high circulating levels of insulin-like growth factor-I (IGF-I) are associated with an increased risk of breast cancer among premenopausal women lends credence to the hypothesis that genetic polymorphisms in the IGF-I gene may be involved in the disease. A population-based case-control study was conducted to assess the association of IGF-I gene polymorphisms [(CA)n repeats in the promoter region] with breast cancer risk and plasma IGF-I level in Chinese women. The study included 1,041 incident breast cancer cases diagnosed from August 1996 through March 1998 in Shanghai and 1,086 randomly selected, age frequency-matched controls from the general population. Although no relation between plasma IGF-I levels and IGF-I genotypes was found, women who carried the genotypes containing the (CA)17 or (CA)19 allele were associated with a significantly decreased (OR = 0.80, 95% CI: 0.64-1.00) or increased (OR = 1.23, 95% CI: 1.04-1.47) risk of breast cancer, respectively, and women who carried the genotypes containing any of the 4 rare alleles, (CA)11, (CA)13, (CA)16 and (CA)23, were associated with a nonsignificantly increased risk of breast cancer (OR = 1.92, 95% CI: 0.92-4.02) compared to those who did not carry the specific alleles. The associations with the (CA)17 or (CA)19 allele were predominantly present among premenopausal women and in a dose-response manner. The meta-analysis results indicated that IGF-I genotypes containing the (CA)19 were consistently associated with increased risk of breast cancer across studies (overall OR = 1.22, 95% CI: 1.06-1.41, p for heterogeneity test = 0.524). The findings of this study support the hypothesis that IGF-I gene polymorphisms may be a significant genetic factor for breast cancer susceptibility.     

Insulin-like growth factor-I receptor, E-cadherin and alpha v integrin form a dynamic complex under the control of alpha-catenin

Dynamic crosstalk between cell adhesion molecules, extracellular matrix and soluble informative factors is essential for cancer cell migration and invasion. Here, we investigated the mechanisms by which the E-cadherin/catenin complex and alpha v integrin can modulate insulin-like growth factor-I (IGF-I)-induced cell migration. Human colon mucosa, human colon cancer cell lines, HT29-D4 and HCT-8 derivatives that differ in their expression of alpha-catenin, were used as models. Interactions between E-cadherin, alpha v integrin and IGF-I receptor (IGF-IR) were analyzed by coimmunoprecipitation and immunolocalization experiments. The impact of these interactions on cell mobility was determined by haptotaxis assays. We report that alpha v integrin, E-cadherin and IGF-IR form a ternary complex in both cultured cancer cells and human normal colonic mucosa. alpha-Catenin regulates the scaffolding of this complex. IGF-IR ligation by IGF-I induces the disruption of the complex and the relocalization of alpha v integrin from cell-cell contacts to focal contact sites. This perturbation is correlated with the observed increase in cell migration. These results suggest that regulation of the alpha v integrin/E-cadherin/IGF-IR scaffolding is essential for the modulation of cell mobility. Its alteration could be of major importance to sustain alterations in cell adhesion that occur during cancer cell invasion and metastasis.     

Insulin-like growth factor-I receptor as a marker for prognosis and a therapeutic target in human esophageal squamous cell carcinoma

Insulin-like growth factor (IGF)-I receptor (IGF-Ir) signaling is required for tumorigenicity and progression of many tumors but this pathway has not been well studied as a prognostic factor or potential therapeutic target in esophageal squamous cell carcinoma (ESCC). In this paper, the association between the expression of IGF-Ir and IGF-II ligand and prognosis was investigated immunohistochemically in 100 surgically resected ESCC. We then assessed the therapeutic effect of blocking IGF receptor signaling using dominant negative IGF-Ir (IGF-Ir/dn) in ESCC in vitro. Expression of IGF-Ir and IGF-II were detected in 60 and 50% of tumors, respectively, and were associated with invasion depth, metastasis, advanced tumor stage and recurrence. Patients with tumors expressing both IGF-Ir and IGF-II had a significantly shorter survival than those expressing either alone or neither in both single and multivariate analysis. IGF-Ir/dn suppressed proliferation and motility as well as upregulating chemotherapy-induced apoptosis through blocking ligand-induced Akt activation. We propose that detection of IGF-Ir/IGF-II in ESCC may be useful for the prediction of recurrence and poor prognosis and for selecting patients for IGF-Ir-targeted therapy. Therapeutic blockade of IGF-Ir may be a useful anticancer therapeutic for ESCC.     

Insulin-like growth factor I receptor signaling in differentiation of neuronal H19-7 cells

The type I insulin-like growth factor receptor (IGF-IR) is known to send two seemingly contradictory signals inducing either cell proliferation or cell differentiation, depending on cell type and/or conditions. H19-7 cells are rat hippocampal neuronal cells immortalized by a temperature-sensitive SV40 large T antigen that grow at 34 degrees C in epidermal growth factor or serum but differentiate at 39 degrees C when induced by basic fibroblast growth factor. At 39 degrees C, expression of the human IGF-IR in H19-7 cells induces an insulin-like growth factor (IGF) I-dependent differentiation. We have investigated the domains of the IGF-IR required for differentiation of H19-7 cells. The tyrosine 950 residue and serines 1280-1283 in the COOH terminus of the receptor are required for IGF-I-induced differentiation at 39 degrees C, although they are dispensable for IGF-I-mediated growth at 34 degrees C. Both domains have to be mutated to inactivate the differentiating function. The inability of these mutant receptors to induce differentiation correlates with mitogen-activated protein kinase activation. In contrast, inhibitors of phosphatidylinositol 3'-kinase have no effect on IGF-I-mediated differentiation of H19-7 cells, although they do inhibit the mitogenic response.     

Insulin-like growth factor-I, IGF-binding protein-3, and mammographic breast density.

Some studies have suggested that insulin-like growth factor (IGF) pathway is related to premenopausal breast density, one of the strongest known breast cancer risk factors. This study was designed specifically to test the hypothesis that higher levels of IGF-I and lower levels of IGF-binding protein (IGFBP)-3 are associated with high mammographic breast density among premenopausal but not among postmenopausal women. A total of 783 premenopausal and 791 postmenopausal healthy women were recruited during screening mammography examinations. Blood samples were collected at the time of mammography, and plasma IGF-I and IGFBP-3 levels were measured by ELISA. Mammographic breast density was estimated using a computer-assisted method. Spearman's partial correlation coefficients (r(s)) were used to evaluate the associations. Adjusted mean breast density was assessed by joint levels of IGF-I and IGFBP-3 using generalized linear models. Among premenopausal women, high levels of IGF-I and low levels of IGFBP-3 were independently correlated with high breast density (r(s) = 0.083; P = 0.021 and r(s) = -0.124; P = 0.0005, respectively). Correlation of IGF-I with breast density was stronger among women in the lowest tertile of IGFBP-3 than among those in the highest tertile of IGFBP-3 (r(s) = 0.138; P = 0.027 and r(s) = -0.039; P = 0.530, respectively). In contrast, the correlation of IGFBP-3 with breast density was stronger among women in the highest tertile of IGF-I than among those in the lowest tertile of IGF-I (r(s) = -0.150; P = 0.016 and r(s) = -0.008; P = 0.904, respectively). Women in the combined top tertile of IGF-I and bottom tertile of IGFBP-3 had higher mean breast density than those in the combined bottom tertile of IGF-I and top tertile of IGFBP-3 (53.8% versus 40.9%; P = 0.014). No significant association was observed among postmenopausal women. Our findings confirm that IGF-I and IGFBP-3 are associated with breast density among premenopausal women. They provide additional support for the idea that, among premenopausal women, these growth factors may affect breast cancer risk, at least in part, through their influence on breast tissue morphology as reflected on mammogram.     

Insulin-like growth factor-I receptor (IGF-IR) targeting with monoclonal antibody cixutumumab (IMC-A12) inhibits IGF-I action in endometrial cancer cells

Specific insulin-like growth factor-I receptor (IGF-IR) targeting emerged in recent years as a promising therapeutic strategy in cancer. Endometrial cancer is the most common gynaecological cancer in the Western world. The aim of this study was to evaluate the potential of cixutumumab (IMC-A12, ImClone Systems), a fully human monoclonal antibody against the IGF-IR, to inhibit IGF-I-mediated biological actions and cell signalling events in four endometrial carcinoma-derived cell lines (ECC-1, Ishikawa, USPC-1 and USPC-2). Our results demonstrate that cixutumumab was able to block the IGF-I-induced autophosphorylation of the IGF-IR. In addition, the PI3K and MAPK downstream signalling pathways were also inactivated by cixutumumab in part of the cell lines. Prolonged (24 h and 48 h) exposures to cixutumumab reduced IGF-IR expression. Furthermore, confocal microscopy of GFP-tagged receptors shows that cixutumumab treatment led to IGF-IR redistribution from the cell membrane to the cytoplasm. Antiapoptotic effects were evaluated by cleavage of caspase 3 and PARP, and mitogenicity and transformation by proliferation and cell cycle assays. Results obtained showed that cixutumumab abrogated the IGF-I-stimulated increase in proliferation rate, and increased caspase-3 and PARP cleavage, two markers of apoptosis. Of importance, cixutumumab had no effect neither on insulin receptor (IR) expression nor on IGF-I activation of IR. In summary, in a cellular model of endometrial cancer cixutumumab was able to inhibit the IGF-I-induced activation of intracellular cascades, apoptosis and proliferation.     

胰岛素样生长因子-Ⅰ上调表皮生长因子对HCE16/3细胞的作用

目的了解胰岛素样生长因子－Ｉ（ＩＧＦ－Ｉ）对ＨＰＶ１６型ＤＮＡ－永生化的人宫颈上皮细胞（ＨＣＥ１６／３细胞）的生长和病毒基因表达的调节。方法使用流式细胞术、软琼脂糖试验和ＲＴ－ＰＣＲ分析了ＩＧＦ－Ｉ和表皮生长因子（ＥＧＦ）对ＨＣＥ１６／３细胞的生长和病毒早期基因表达的调节。结果在缺乏血清的培养条件下,ＩＧＦ－Ｉ对ＨＣＥ１６／３细胞的生长几乎没有调节作用。但ＥＧＦ对永生化上皮细胞有生长刺激作用,这种刺激作用可被ＩＧＦ－Ｉ增强。ＥＧＦ合并使用ＩＧＦ－Ｉ可诱导ＨＣＥ１６／３细胞停泊不依赖性生长。ＲＴ－ＰＣＲ显示ＩＧＦ－Ｉ并不明显改变ＨＣＥ１６／３细胞病毒早期基因的表达。结论ＩＧＦ－Ｉ是ＨＣＥ１６／３细胞生长的弱调节剂,但它可以增强ＥＧＦ对ＨＣＥ１６／３细胞生长的刺激作用     

Insulin-like growth factor-I receptor signaling pathway induces resistance to the apoptotic activities of SCH66336 (lonafarnib) through Akt/mammalian target of rapamycin-mediated increases in survivin expression.

Although preclinical studies have suggested that farnesyltransferase inhibitors (FTI) have promising antitumor activity, clinical trials have shown that FTI activity in patients is actually limited. The mechanism that induces resistance to FTI treatment is still not fully understood. The FTI SCH66336 has been shown to induce apoptotic and antiangiogenic activities in a subset of head and neck squamous cell carcinoma (HNSCC) and non-small cell lung cancer (NSCLC) cell lines. We therefore investigated the mechanisms mediating resistance to the therapeutic activities of SCH66336 in HNSCC and NSCLC. Our various analyses showed that insulin-like growth factor-I receptor (IGF-IR) activation interferes with the antitumor activity of SCH66336 in HNSCC and NSCLC cells. Treatment with SCH66336 activated the IGF-IR/phosphatidylinositol 3-kinase/Akt pathway, leading to increased mammalian target of rapamycin (mTOR)-mediated protein synthesis of survivin in a subset of HNSCC and NSCLC cell lines that were insensitive to the apoptotic activities of the drug. Inhibition of IGF-IR, Akt, or mTOR or the knockdown of survivin expression abolished resistance to SCH66336 and induced apoptosis in the cells. Overexpression of survivin by the use of adenoviral vector protected SCH66336-sensitive HNSCC cells from the apoptotic activities of the drug. Our results suggest that expression of phosphorylated IGF-IR, phosphorylated Akt, phosphorylated mTOR, and survivin serves as biological markers of SCH66336 responsiveness in HNSCC and NSCLC cells and that SCH66336 induces survivin expression through an IGF-IR/Akt/mTOR-dependent pathway. Thus, combining inhibitors of IGF-IR, phosphatidylinositol 3-kinase/Akt, mTOR, or survivin with SCH66336 may be an effective anticancer therapeutic strategy for patients with HNSCC or NSCLC.