The type 1 insulin-like growth factor receptor pathway

Research conducted over the past two decades has shown the importance of the type 1 insulin-like growth factor receptor (IGF1R) in tumorigenesis, metastasis, and resistance to existing forms of cancer therapy. The IGF1R itself has only recently been accepted as a credible treatment target, however, perhaps reflecting the potential problems for drug design posed by normal tissue IGF1R expression, and close homology with the insulin receptor. Currently approximately 12 anti-IGF1R therapeutics are undergoing clinical evaluation, including blocking antibodies and tyrosine kinase inhibitors. This review will summarize the principal signaling pathways activated by IGF1R and the preclinical data that validated this receptor as a treatment target. We will review clinical progress in the testing of IGF1R inhibitory drug candidates, the relative benefits and potential toxicities of coinhibition of the insulin receptor, and the rationale for combining IGF1R blockade with other cancer treatments. An understanding of IGF1R signaling is important because it will guide the incorporation of appropriate molecular markers into clinical trial design. This will be key to the identification of patients most likely to benefit, and so will influence the ability of IGF1R inhibition to make the transition from experimental intervention to clinical therapy.     

Activation of insulin-like growth factor I receptor signaling pathway is critical for mouse plasma cell tumor growth

Plasma cell neoplasia in humans generally occurs as multiple myeloma, an incurable form of cancer. Tumors with marked similarity can be induced in mice by a variety of agents, including chemicals, silicone, and oncogene-containing retroviruses, suggesting the use of murine tumors as an informative model to study plasma cell disease. Herein, we have focused on the role of insulin-like growth factor I receptor (IGF-IR) signaling in the development of plasma cell disease. The insulin receptor substrate 2/phosphatidylinositol 3'-kinase/p70S6K pathway was found to be either constitutively or IGF-I-dependently activated in all plasma cell tumors. Biological relevance was demonstrated in that plasma cell lines with up-regulated IGF-IR expression levels exhibited mitogenic responses to IGF-I. More importantly, expression of a dominant-negative mutant of IGF-IR in these lines strongly suppressed tumorigenesis in vivo. Taken together, these results demonstrate that up-regulation and activation of IGF-IR and the downstream signaling pathway involving insulin receptor substrate 2, phosphatidylinositol 3'-kinase, and p70S6K may play an important role in the development of a broad spectrum of plasma cell tumors.     

The insulin-like growth factor-I receptor kinase inhibitor NVP-ADW742 sensitizes medulloblastoma to the effects of chemotherapy

Medulloblastoma is the most common malignant tumor of the central nervous system in children. The insulin-like growth factor-I receptor (IGF-IR) is an important growth factor for medulloblastoma. The novel IGF-I receptor (IGF-IR) kinase inhibitor NVP-ADW742 has in vitro activity against tumors. Daoy cells were treated with NVP-ADW742 combined with temozolomide, which is commonly used in the chemotherapy of medulloblastoma. The effects on proliferation were assayed by CCK-8 assay. Cell cycle status and apoptosis were assayed by FACS analysis. The IGF-IR signaling pathway was analyzed by RT2 Profiler? PCR arrays and Western blotting. NVP-ADW742 inhibited IGF-IR-mediated proliferation with an IC50 of 11.12 μmol/l. The PCR array data suggested that 14 genes were down-regulated at the mRNA level after NVP-ADW742 treatment. Western blot analysis suggested that NVP-ADW742 induced early suppression of Akt, P38 and GSK-3β phosphorylation, as well as a decrease in the intracellular levels of PI3K, Akt, P38, GSK-3β and Bcl-2. Combined with NVP-ADW742 (2 μmol/l), IC50 of Daoy to temozolomide was decreased from 452.12 to 256.81 μmol/l. Cell apoptosis was enhanced from 16.18±2.47% to 23.20 ± 2.80%. G phase arrest was also found in both the temozolomide alone group and the temozolomide combined with NVP-ADW742 group. NVP-ADW742 inhibited the activation of PI3K, Akt, P38 and GSK-3β caused by temozolomide. NVP-ADW742 enhanced the chemosensitivity of Daoy to temozolomide in vitro, as a potent anti-tumor agent highly selective against IGF-IR.     

The insulin-like growth factor axis and prostate cancer: lessons from the transgenic adenocarcinoma of mouse prostate (TRAMP) model

We have characterized the temporal expression of the insulin-like growth factor (IGF) axis in the transgenic adenocarcinoma of mouse prostate (TRAMP) model as prostate cancer progression in this model closely mimics that observed in the human disease, and the model provides samples representing the earliest stages of prostate cancer that are clinically the most difficult to obtain. We report that prostate-specific IGF-I mRNA expression increased during prostate cancer progression in TRAMP mice and was elevated in the accompanying metastatic lesions, whereas prostatic IGF-I mRNA remained at nontransgenic levels in androgen-independent disease. Expression of IGF-II mRNA, however, was reduced in primary prostate cancer, metastatic lesions, and androgen-independent disease. Expression of type-1 IGF receptor (IGF1R) mRNA, encoding the cognate receptor for both IGF-I and IGF-II, as well as type-2 IGF receptor (IGF2R) mRNA was not found to be altered during primary prostate cancer progression in intact TRAMP mice but was dramatically reduced in metastatic lesions and in androgen-independent disease. Similar to reports from clinical disease, serum IGF-I levels were observed to increase precociously in TRAMP mice early in disease progression but remained at nontransgenic levels after castration. Elevated serum levels of IGF-binding protein 2 were observed to correlate with advanced prostate cancer in the TRAMP model. Together these observations implicate IGF-I as an important factor during the initiation and progression of primary prostate cancer and provide evidence that there is a strong selection against expression of IGF1R and IGF2R in metastatic and androgen-independent disease.     

Tumor development by transgenic expression of a constitutively active insulin-like growth factor I receptor

The insulin-like growth factor I receptor (IGF-IR) is a transmembrane tyrosine kinase that is essential to growth and development and also thought to provide a survival signal for the maintenance of the transformed phenotype. There has been increasing interest in further understanding the role of IGF-I signaling in cancer and in developing receptor antagonists for therapeutic application. We describe herein a novel animal model that involves transgenic expression of a fusion receptor that is constitutively activated by homodimerization. Transgenic mice that expressed the activated receptor showed aberrant development of the mammary glands and developed salivary and mammary adenocarcinomas as early as 8 weeks of age. Xenograft tumors and a cell line were derived from the transgenic animals and are sensitive to inhibition by a novel small-molecule inhibitor of the IGF-IR kinase. This new model should provide new opportunities for further understanding how aberrant IGF-IR signaling leads to tumorigenesis and for optimizing novel antagonists of the receptor kinase.     

Oligodendrogliomas result from the expression of an activated mutant epidermal growth factor receptor in a RAS transgenic mouse astrocytoma model

A significant proportion of human malignant gliomas exhibit amplification, overexpression, or mutations of the epidermal growth factor receptor (EGFR). To define the functional role(s) of the EGFR in the pathogenesis of gliomas, we established transgenic mice that express both wild-type (wt) and mutant (EGFRvIII) EGFR molecules using the human glial fibrillary acidic protein (GFAP) promoter. Both GFAP-EGFR(wt) and GFAP-EGFRvIII transgenic mice demonstrated increased numbers of astrocytes compared with control littermates, however, developed normally without formation of gliomas. To determine whether EGFR overexpression could modify the tumor phenotype in our previously reported GFAP-V(12)Ha-ras transgenic mouse astrocytoma model, mice expressing both activated RAS and EGFR were developed. GFAP-V(12)Ha-ras;GFAP-EGFRvIII, but not GFAP-V(12)Ha-ras;GFAP-EGFR(wt) double transgenic mice, had decreased survival with fifty percent of the mice dead at 2-4 weeks from gliomas, compared with 12-16 weeks for the GFAP-V(12)Ha-ras mice. Furthermore, GFAP-V(12)Ha-ras;GFAP-EGFRvIII mice developed oligodendrogliomas and mixed oligoastrocytoma tumors, instead of the fibrillary astrocytomas observed in GFAP-V(12)Ha-ras mice. In addition to yielding a spontaneous model of infiltrating oligodendroglioma, this study demonstrates that astrocyte-specific expression of EGFRvIII alone is insufficient for gliomagenesis but rather contributes to glioma progression in the context of existing predisposing genetic changes.     

17beta-estradiol up-regulates the insulin-like growth factor receptor through a nongenotropic pathway in prostate cancer cells

Prostate carcinomas frequently express estrogen receptors (ER), irrespective of androgen receptor (AR) expression; however, the role of ERs and estrogens in prostate cancer is controversial. We found that 17beta-estradiol (E(2)) is able to markedly up-regulate insulin-like growth factor (IGF)-I receptor (IGF-IR) mRNA and protein expression in both AR-positive (LNCaP cells) and AR-negative (PC-3 cells) prostate cancer cells. This effect occurs not only via ERalpha but also via ERbeta stimulation and is specific for IGF-IR because it does not involve the cognate insulin receptor. IGF-IR up-regulation is associated with increased IGF-IR phosphorylation and with increased mitogenic and motogenic activities in response to IGF-I. IGF-IR up-regulation by E(2) does not require ER binding to DNA and is poorly sensitive to antiestrogen blockade, whereas it is associated with the activation of cytosolic kinase cascades involving Src, extracellular signal-regulated kinase (ERK)-1/2, and, to a lesser extent, phosphatidylinositol 3-kinase and is sensitive to the inhibition of these kinases. In conclusion, our data indicate that estrogens may contribute to IGF system deregulation in prostate cancer through the activation of a nongenotropic pathway. Estrogens may have a role, therefore, in tumor progression to androgen independence. Inhibition of the IGF-IR or the Src-ERK pathway should be considered, therefore, as an adjuvant therapy in prostate cancer.     

Overexpression of the insulin-like growth factor I receptor and activation of the AKT pathway in hyperplastic endometrium.

PURPOSE: Although there is considerable information on the molecular aberrations associated with endometrial cancer, very little is known of the changes in gene expression associated with endometrial hyperplasia. EXPERIMENTAL DESIGN: To address this, we have compared the level of expression of estrogen-regulated genes and components of the insulin-like growth factor I (IGF-I) signaling pathway in endometrial biopsies from subjects with normal endometrium, complex atypical endometrial hyperplasia, and endometrial adenocarcinoma (type I). RESULTS: There was a significant increase in the expression of the IGF-I receptor (IGF-IR) in biopsies from hyperplastic endometrium and endometrial carcinoma compared with the proliferative endometrium. The receptor was also activated, as judged by increased tyrosine phosphorylation. In addition, in endometrial hyperplasia and carcinoma, the downstream components of the IGF-IR pathway are activated, as reflected in increased Akt phosphorylation. Loss of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) expression in endometrial hyperplasia did not correlate with increased activation of IGF-IR. However, the simultaneous loss of PTEN expression and increased IGF-IR activation in hyperplasia was associated with an increased incidence of endometrial carcinoma. CONCLUSIONS: These results suggest that up-regulation of IGF-IR and loss of PTEN may be independent events that give rise to complementary activation of the IGF-I pathway and increase the probability of the development of cancer. These studies suggest that increased expression of IGF-IR may be an important contributor to the risk of endometrial hyperplasia and cancer.     

IGF1信号通路IGF1 IGF1R及AKT在卵巢癌顺铂耐药中表达的研究

  目的  检测IGF信号通路关键蛋白IGF1、IGF1R及AKT在卵巢癌患者血清及组织中的表达。  方法  ATP-TCA法对卵巢癌标本进行药敏试验,ELISA法检测顺铂耐药和敏感组患者血清中IGF1、IGF1R及P-AKT的表达,免疫组织化学检测卵巢癌组织中IGF1、IGF1R、Akt的表达。自患者完成化疗出院后每个月复查CA125,如CA125有异常则行影像学检查,随访时间1年。  结果  IGF1、IGF1R及AKT在卵巢癌顺铂耐药组的表达显著高于敏感组（P=0.000 1）,免疫组织化学结果显示顺铂耐药组和敏感组IGF1、IGF1R及AKT的表达相比较差异有统计学意义（P＜0.05）。随访顺铂敏感组24例中有18例患者超过1年CA125处于正常值;6例患者超过半年CA125处于正常值;耐药组中有16例患者化疗结束后半年内CA125上升高于正常值,彩超或MRI检查提示有复发病灶。  结论  IGF信号通路关键蛋白可能参与卵巢癌顺铂耐药,IGF1可能作为卵巢癌靶向治疗的新靶点。      

A mouse model of the most aggressive subgroup of human medulloblastoma

Medulloblastomas that display a large cell/anaplastic morphology and overexpress the cellular c-MYC gene are highly aggressive and carry a very poor prognosis. This so-called MYC-subgroup differs in its histopathology, gene expression profile, and clinical behavior from other forms of medulloblastoma. We generated a mouse model of MYC-subgroup medulloblastoma by transducing Trp53-null cerebellar progenitor cells with Myc. The cardinal features of these mouse medulloblastomas closely mimic those of human MYC-subgroup tumors and significantly differ from mouse models of the Sonic-Hedgehog- and WNT-disease subgroups. This mouse model should significantly accelerate understanding and treatment of the most aggressive form of medulloblastoma and infers distinct roles for MYC and MYCN in tumorigenesis.     

The Ron receptor promotes prostate tumor growth in the TRAMP mouse model

The Ron receptor tyrosine kinase (TK) is overexpressed in many cancers, including prostate cancer. To examine the significance of Ron in prostate cancer in vivo, we utilized a genetically engineered mouse model, referred to as TRAMP mice, that is predisposed to develop prostate tumors. In this model, we show that prostate tumors from 30-week-old TRAMP mice have increased Ron expression compared with age-matched wild-type prostates. Based on the upregulation of Ron in human prostate cancers and in this murine model of prostate tumorigenesis, we hypothesized that this receptor has a functional role in the development of prostate tumors. To test this hypothesis, we crossed TRAMP mice with mice that are deficient in Ron signaling (TK-/-). Interestingly, TK-/- TRAMP+ mice show a significant decrease in prostate tumor mass relative to TRAMP mice containing functional Ron. Moreover, TK-/- TRAMP+ prostate tumors exhibited decreased tumor vascularization relative to TK+/+ TRAMP+ prostate tumors, which correlated with reduced levels of the angiogenic molecules vascular endothelial growth factor and CXCL2. Although Ron loss did not alter tumor cell proliferation, a significant decrease in cell survival was observed. Similarly, murine prostate cancer cell lines containing a Ron deficiency exhibited decreased levels of active nuclear factor-κB, suggesting that Ron may be important in regulating prostate cell survival at least partly through this pathway. In total, our data show for the first time that Ron promotes prostate tumor growth, prostate tumor angiogenesis and prostate cancer cell survival in vivo.     

鼻咽癌细胞PI3K/AKT和ERK/MAPK信号通路活性表达及其临床意义的探讨

目的:探讨鼻咽癌细胞中PK3K/AKT和ERK/MAPK信号传导通路异常激活与鼻咽癌细胞发生发展的关系.方法:蛋白质印迹法检测3例鼻咽低分化鳞癌组织及其细胞株(CNE2)和鼻咽炎性组织中IGF-1R、AKT和ERKl/2蛋白的表达情况;相同实验方法检测鼻咽癌细胞株CNE2中磷酸化的PAKT和pERK1/2蛋白的表达和给予胰岛素样生长因子-1(IGF-1)刺激癌细胞后磷酸化的pAKT和pERK的表达水平,再分别用PKB/AKT和ERK/MAPK通路抑制剂对CNE2细胞信号传导通路磷酸化的调节作用进行抑制试验.结果:3例鼻咽低分化鳞癌组织和cNE2细胞株中IGF-1R、AKT和ERK1/2蛋白表达水平明显高于鼻咽炎性组织;IGF-1可刺激CNE2细胞中PAKT和pERK1/2的表达增加,与空白对照组相比,其pAKT和pERK表达量明显增高;给予wortrnannin和PD98059治疗24和48 h后,CNE2细胞株生长明显受到抑制.结论:IGF-lR的过度表达及其PK3K/AKT、ERK/MAPK信号传导通路的异常激活在鼻咽癌的发生、发展过程中可能起着非常重要的作用,IGF-1R系统有可能作为复发或转移性鼻咽癌治疗中一个潜在的靶分子.中华肿瘤防治杂志.2009,16(1):44-47     

胰岛素样生长因子1受体信号通路与西妥昔单抗在鼻咽癌耐药机制中的关系

目的 建立西妥昔单抗耐药的人鼻咽癌细胞系5-8F/Erbitux,初步探讨胰岛素样生长因子1受体(IGF-1R)信号通路与西妥昔单抗在鼻咽癌耐药机制中的关系.方法 以表皮生长因子受体(EGFR)高表达且西妥昔单抗抑制率较高的人鼻咽癌5-8F细胞株为研究对象,采用逐步增加剂量法诱导建立西妥昔单抗耐药细胞5-8F/Erbitux.采用四甲基偶氮唑蓝(MTr)法检测西妥昔单抗对5-8F/Erbitux细胞的半数抑制浓度(IC50),计算耐药指数(RI).计数法描绘5-8F/Erbitux和5-8F细胞的生长曲线,计算倍增时间(TD).以流式细胞仪检测5-8F/Erbitux和5-8F细胞的细胞周期.采用MTT法检测5-8F/Erbitux细胞对5-氟尿嘧啶(5-Fu)、顺铂(DDP)及紫杉醇(TAX)的交叉耐药谱.采用Western blot法检测5-8F/Erbitux和5-8F细胞中P糖蛋白(P-gp)、IGF-1R及磷酸化IGF-1R(p-IGF1R)的表达.采用实时荧光定量PCR法检测5-8F/Erbitux和5-8F细胞中多药耐药基因(MDR1)的表达量.结果 成功建立西妥昔单抗耐药的人鼻咽癌细胞系5-8F/Erbitux,西妥昔单抗作用3 d和5 d时的RI分别为1.2和1.1.5-8F和5-8F/Erbitux细胞的TD分别为26.63 h和142.30 h.与5-8F细胞比较,5-8F/Erbitux细胞中G0/G1期比例显著增高(P＜0.001),S期比例显著下降(P＜0.001).5-8F/Erbitux对5-Fu存在交叉耐药(RI=3.95,P＜0.01),对TAX和DDP不存在交叉耐药(RI分别为1.14和0.68,均P＞0.05).与5-8F细胞相比,5-8F/Erbitux细胞中P-gp、IGF-1R及p-IGF-1R蛋白的表达水平均显著升高(均P＜0.001).MDR1基因在5-8F细胞中未检测到,而在5-8F/Erbitux细胞中仅有很微量的表达.结论 西妥昔单抗耐药细胞5-8F/Erbitux不存在与传统化疗药物相似的多药耐药性;过度活化的IGF-1R信号通路可能是5-8F/Erbitux细胞耐药的机制之一.