The Receptor for the Type I Insulin-like Growth Factor and its Ligands Regulate Multiple Cellular Functions That Impact on Metastasis

Molecular regulation of phenolic compounds on IGF-1 signaling cascade in breast cancer

Breast cancer is a highly aggressive and heterogeneous disease with complex features that remains a major health problem and undermines the span and quality of life of women worldwide. Primary literature has shown the role of phenolic compounds in controlling the onset of breast cancer. The mechanism of action of phenolic compounds can be explained by their interaction with signal transduction pathways that regulate cell proliferation and induction of apoptosis. One of the targets of phenolic compounds is the insulin like growth factor 1 (IGF-1) signaling cascade, which plays a significant role in the growth and development of mammary tissues by leading proliferative and anti-apoptotic events. Increasing research evidence points to the function of the IGF-1 cascade system in the commencement, progression, and metastasis of breast tissue malignancy. In this review, we mainly discuss the function of the IGF-1 system, and the role of phenolic compounds in regulating the IGF-1 signaling cascade and curbing breast malignancies.

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

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

M2‑like tumour‑associated macrophage‑secreted IGF promotes thyroid cancer stemness and metastasis by activating the PI3K/AKT/mTOR pathway

M2‑like tumour‑associated macrophages (TAMs) have been demonstrated to promote the growth of anaplastic thyroid carcinoma (ATC). However, the underlying mechanism of M2‑like TAMs in ATC remains unclear. Thus, in the present study, the role and mechanism of M2‑like TAMs in ATC were investigated. M2‑like TAMs were induced by treatment with PMA, plus IL‑4 and IL‑13, and identified by flow cytometry. Transwell and sphere formation assays were applied to assess the invasion and stemness of ATC cells. The expression levels of insulin‑like growth factor (IGF)‑1 and IGF‑2 were examined by ELISA and reverse transcription‑quantitative PCR. Proteins related to the epithelial‑mesenchymal transition (EMT), stemness and the PI3K/AKT/mTOR pathway were examined via western blotting. Immunohistochemistry (IHC) was used to detect the expression of the M2‑like TAM markers CD68 and CD206 in ATC tissues and thyroid adenoma tissues. It was found that treatment with PMA plus IL‑4 and IL‑13 successfully induced M2‑like TAMs. Following co‑culture with M2‑like TAMs, the invasive ability and stemness of ATC cells were significantly increased. The expression levels of the EMT‑related markers N‑cadherin and Vimentin, the stemness‑related markers Oct4, Sox2 and CD133, and the insulin receptor (IR)‑A/IGF1 receptor (IGF1R) were markedly upregulated, whereas E‑cadherin expression was significantly decreased. In addition, the production of IGF‑1 and IGF‑2 was significantly increased. Of note, exogenous IGF‑1/IGF‑2 promoted the invasion and stemness of C643 cells, whereas blocking IGF‑1 and IGF‑2 inhibited metastasis and stemness by repressing IR‑A/IGF‑1R‑mediated PI3K/AKT/mTOR signalling in the co‑culture system. IHC results showed that the expression of CD68 and CD206 was obviously increased in ATC tissues. To conclude, M2‑like TAMs accelerated the metastasis and increased the stemness of ATC cells, and the underlying mechanism may be related to the section of IGF by M2‑like TAMs, which activates the IR‑A/IGF1R‑mediated PI3K/AKT/mTOR signalling pathway.

Comparison of Survival Outcomes Among Patients With Breast Cancer With Distant vs Ipsilateral Supraclavicular Lymph Node Metastases

IMPORTANCE

There is a lack of studies exploring whether the survival of patients with distant lymph node metastases (DLNM) is different from that of patients with ipsilateral supraclavicular lymph node metastases (ISLM) and other stage IV breast cancer.

OBJECTIVE

To assess the survival of patients with DLNM from breast cancer vs ISLM and other stage IV breast cancer.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included 2033 patients diagnosed with breast cancer between January 1, 2010, and December 31, 2014, from the Surveillance, Epidemiology and End Results registries database. Three groups of patients were included: (1) patients with ISLM without any distant metastasis, (2) patients with DLNM, and (3) patients with distant metastases (DLNM excluded). Patients younger than 18 years or older than 100 years were excluded. The data were analyzed in February 2020.

EXPOSURES

Surgery for primary tumor, surgery for distant lymph nodes, and radiotherapy.

MAIN OUTCOMES AND MEASURES

Overall survival (OS) and breast cancer-specific survival (BCSS).

RESULTS

Of the 2033 women (mean [SD] age, 62.03 [14.62] years [range, 23.00-99.00 years]; 1510 White participants [74.3%]) with breast cancer included in the study, 346 patients (17.0%) had DLNM, 212 (10.4%) had ISLM, and 1475 (72.6%) had distant metastases (DLNM excluded). The 3-year BCSS rates were 63.24% for ISLM, 64.54% for DLNM, and 41.20% for distant metastases. The 3-year OS rates were 53.46% for ISLM, 62.67% for DLNM, and 38.21% for distant metastases. Compared with patients with ISLM, patients with DLNM showed similar BCSS (hazard ratio [HR], 0.81; 95% CI, 0.52-1.25; P = .34) and OS (HR, 0.73; 95% CI, 0.51-1.05; P = .09), whereas patients with distant metastases showed significantly poorer BCSS (HR, 1.99; 95% CI, 1.43-2.78; P < .001) and OS (HR, 1.79; 95% CI, 1.35-2.38; P < .001). Of the 346 patients with DLNM, primary surgery (HR, 0.21; 95% CI, 0.12-0.39; P < .001) and radiotherapy (HR, 0.46; 95% CI, 0.25-0.87; P = .02) were significantly associated with improved OS.

CONCLUSIONS AND RELEVANCE

The results of this cohort study suggest that DLNM of breast cancer, with similar survival to N3c disease (indicating metastases to the ipsilateral supraclavicular lymph nodes), might be a regional disease, and reassessment of the role of lymph node metastases in breast cancer may be necessary. Given these findings, aggressive locoregional therapies for this disease are recommended, although future studies are still needed to confirm these results.

Plasmodium infection inhibits tumor angiogenesis through effects on tumor-associated macrophages in a murine implanted hepatoma model

Background

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death in China. The lack of an effective treatment for this disease results in a high recurrence rate in patients who undergo radical tumor resection, and the 5-year survival rate of these patients remains low. Our previous studies demonstrated that Plasmodium infection provides a potent antitumor effect by inducing innate and adaptive immunity in a murine Lewis lung carcinoma (LLC) model.

Methods

This study aimed to investigate the inhibitory effect of Plasmodium infection on hepatocellular carcinoma in mice, and various techniques for gene expression analysis were used to identify possible signal regulation mechanisms.

Results

We found that Plasmodium infection efficiently inhibited tumor progression and prolonged survival in tumor-bearing mice, which served as a murine implanted hepatoma model. The inhibition of tumor progression by Plasmodium infection was related to suppression of tumor angiogenesis within the tumor tissue and decreased infiltration of tumor-associated macrophages (TAMs). Further study demonstrated that matrix metalloprotease 9 (MMP-9) produced by TAMs contributed to tumor angiogenesis in the tumor tissue and that the parasite-induced reduction in MMP-9 expression in TAMs resulted in the suppression of tumor angiogenesis. A mechanistic study revealed that the Plasmodium-derived hemozoin (HZ) that accumulated in TAMs inhibited IGF-1 signaling through the PI3-K and MAPK signaling pathways and thereby decreased the expression of MMP-9 in TAMs.

Conclusions

Our study suggests that this novel approach of inhibiting tumor angiogenesis by Plasmodium infection is of high importance for the development of new therapies for cancer patients.

Roles of insulin-like growth factor II in regulating female reproductive physiology

The number of growth factors involved in female fertility has been extensively studied, but reluctance to add essential growth factors in culture media has limited progress in optimizing embryonic growth and implantation outcomes, a situation that has ultimately led to reduced pregnancy outcomes. Insulin-like growth factor II (IGF-II) is the most intricately regulated of all known reproduction-related growth factors characterized to date, and is perhaps the predominant growth factor in human ovarian follicles. This review aims to concisely summarize what is known about the role of IGF-II in follicular development, oocyte maturation, embryonic development, implantation success, placentation, fetal growth, and in reducing placental cell apoptosis, as well as present strategies that use growth factors in culture systems to improve the developmental potential of oocytes and embryos in different species. Synthesizing the present knowledge about the physiological roles of IGF-II in follicular development, oocyte maturation, and early embryonic development should, on the one hand, deepen our overall understanding of the potential beneficial effects of growth factors in female reproduction and on the other hand support development (optimization) of improved outcomes for assisted reproductive technologies.

Curcumol induces cell cycle arrest and apoptosis by inhibiting IGF-1R/PI3K/Akt signaling pathway in human nasopharyngeal carcinoma CNE-2 cells

Curcumol has been proved to possess antitumor effects in vivo and in vitro in several cancers. Previously, we have found that curcumol induced apoptosis in CNE-2 cells, but its underlying mechanism has not yet been studied well. Recently, our team clarified that curcumol inhibited colorectal cancer cells' growth partially through insulin-like growth factor 1 receptor (IGF-1R) pathway. Given the key importance of IGF-1R pathway in tumorigenesis, we want to explore whether curcumol effects on nasopharyngeal carcinoma (NPC) cells relates to IGF-1R and its downstream pathway inactivation. In this study, we found that curcumol inhibited IGF-1R and p-Akt expression in a dose- and time-dependent way. In addition, it also regulated their downstream GSK-3β's activity in CNE-2 cells, which further triggering alterations in the expression of cycle- and apoptosis-related molecules, and then leading to G0/G1-phase arrest and apoptosis. Moreover, curcumol's effect on CNE-2 cells was partly eliminated by IGF-1R's agonist IGF-1. In conclusion, our findings indicated that the inhibitory effect of curcumol on proliferation of NPC cells is related to the inhibition of IGF-1R and its downstream PI3K/Akt/GSK-3β pathway.

IGF system in sarcomas: a crucial pathway with many unknowns to exploit for therapy

The insulin-like growth factor (IGF) system has gained substantial interest due to its involvement in regulating cell proliferation, differentiation and survival during anoikis and after conventional and targeted therapies. However, results from clinical trials have been largely disappointing, with only a few but notable exceptions, such as trials targeting sarcomas, especially Ewing sarcoma. This review highlights key studies focusing on IGF signaling in sarcomas, specifically studies underscoring the properties that make this system an attractive therapeutic target and identifies new relationships that may be exploited. This review discusses the potential roles of IGF2 mRNA-binding proteins (IGF2BPs), discoidin domain receptors (DDRs) and metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) in regulating the IGF system. Deeper investigation of these novel regulators of the IGF system may help us to further elucidate the spatial and temporal control of the IGF axis, as understanding the control of this axis is essential for future clinical studies.

The type I insulin-like growth factor regulates the liver stromal response to metastatic colon carcinoma cells

Hepatic stellate cells (HSC) play a major role in initiating the liver fibrogenic (wounding) response of the liver and can also orchestrate a pro-metastatic microenvironment in the liver in response to invading cancer cells. Here we explored the role of the hepatic stellate cells in colon carcinoma liver metastasis with emphasis on the contribution of the insulin-like growth factor (IGF) axis to their activation and function. To this end, we used mice with a Tamoxifen inducible liver IGF-I deficiency. We found that in mice with a sustained IGF-I deficiency, recruitment and activation of HSC into tumor-infiltrated areas of the liver were markedly diminished, resulting in decreased collagen deposition and reduced tumor expansion. In addition, IGF-I could rescue HSC from apoptosis induced by pro-inflammatory factors such as TNF-α known to be upregulated in the early stages of liver metastasis. Moreover, in surgical specimens, activated IGF-IR was observed on HSC-like stromal cells surrounding colorectal carcinoma liver metastases. Finally, IGF-targeting in vivo using an IGF-Trap caused a significant reduction in HSC activation in response to metastatic colon cancer cells. Therefore, our data identify IGF as a survival factor for HSC and thereby, a promoter of the pro-metastatic microenvironment in the liver. IGF-targeting could therefore provide a strategy for curtailing the pro-metastatic host response of the liver during the early stages of liver metastasis.

The insulin-like growth factor-I receptor (IGF-IR) in breast cancer: biology and treatment strategies

Breast cancer is the most common cancer and the second leading cause of cancer-related deaths among women worldwide. Although patients are often diagnosed in the early and curable stages, the treatment of metastatic breast cancer remains a major clinical challenge. The combination of chemotherapy with new targeting agents, such as bevacizumab, is helpful in improving patient survival; however, novel treatment strategies are required to improve clinical outcomes. The insulin-like growth factor-I receptor (IGF-IR) is a tyrosine kinase cell surface receptor which is involved in the regulation of cell growth and metabolism. Previous studies have shown that activation of the IGF-IR signaling pathway promotes proliferation, survival, and metastasis of breast cancer cells. Additionally, overexpression of IGF-IR is associated with breast cancer cell resistance to anticancer therapies. Recently, IGF-IR has been introduced as a marker of stemness in breast cancer cells and there is also accumulating evidence that IGF-IR contributes to the establishment and maintenance of breast cancer epithelial-mesenchymal transition (EMT). Therefore, pharmacological or molecular targeting of IGF-IR could be a promising strategy, in the treatment of patients with breast cancer, particularly in order to circumvent the therapeutic resistance and targeting breast cancer stem/progenitors. Currently, many strategies have been developed for targeting IGF-IR, some have entered clinical trials and some are in preclinical stages for breast cancer therapy. In this review, we will first discuss on the biology of IGF-IR in an attempt to find the role of this receptor in breast cancer and then discuss about therapeutic strategies to target this receptor.

Inhibition of p70S6K1 Activation by Pdcd4 Overcomes the Resistance to an IGF-1R/IR Inhibitor in Colon Carcinoma Cells

Agents targeting insulin-like growth factor 1 receptor (IGF-1R) are being actively examined in clinical trials. Although there has been some initial success of single-agent targeting IGF-1R, attempts in later studies failed because of resistance. This study aimed to understand the effects of programmed cell death 4 (Pdcd4) on the chemosensitivity of the IGF-1R inhibitor OSI-906 in colorectal cancer cells and the mechanism underlying this impact. Using OSI-906-resistant and -sensitive colorectal cancer cells, we found that the Pdcd4 level directly correlates with cell chemosensitivity to OSI-906. In addition, tumors derived from Pdcd4 knockdown cells resist the growth inhibitory effect of OSI-906 in a colorectal cancer xenograft mouse model. Moreover, Pdcd4 enhances the antiproliferative effect of OSI-906 in resistant cells through suppression of p70S6K1 activation. Knockdown of p70S6K1, but not p70S6K2, significantly increases the chemosensitivity of OSI-906 in cultured colorectal cancer cells. Furthermore, the combination of OSI-906 and PF-4708671, a p70S6K1 inhibitor, efficiently suppresses the growth of OSI-906-resistant colon tumor cells in vitro and in vivo. Taken together, activation of p70S6K1 that is inhibited by Pdcd4 is essential for resistance to the IGF-1R inhibitor in colon tumor cells, and the combinational treatment of OSI-906 and PF-4708671 results in enhanced antiproliferation effects in colorectal cancer cells in vitro and in vivo, providing a novel venue to overcome the resistance to the IGF-1R inhibitor in treating colorectal cancer.

Apicidin-resistant HA22T hepatocellular carcinoma cells massively promote pro-survival capability via IGF-IR/PI3K/Akt signaling pathway activation

Despite rapid advances in the diagnostic and surgical procedures, hepatocellular carcinoma (HCC) remains one of the most difficult human malignancies to treat. This may be due to the chemoresistant behaviors of HCC. It is believed that acquired resistance could be overcome and improve the overall survival of HCC patients by understanding the mechanisms of chemoresistance in HCC. A stable HA22T cancer line, which is chronically resistant to a histone deacetylase inhibitor, was established. After comparing the molecular mechanism of apicidin-R HA22T cells to parental ones by Western blotting, cell cycle-regulated proteins did not change in apicidin-R cells, but apicidin-R cells were more proliferative and had higher tumor growth (wound-healing assay and nude mice xenograft model). Moreover, apicidin-R cells displayed increased levels of p-IGF-IR, p-PI3K, p-Akt, Bcl-xL, and Bcl-2 but also significantly inhibited the tumor suppressor PTEN protein and apoptotic pathways when compared to the parental strain. Therefore, the highly proliferative effect of apicidin-R HA22T cells was blocked by Akt knockdown. For all these findings, we believe that novel strategies to attenuate IGF-IR/PI3K/Akt signaling could overcome chemoresistance toward the improvement of overall survival of HCC patients.

The insulin and igf-I pathway in endocrine glands carcinogenesis

Endocrine cancers are a heterogeneous group of diseases that may arise from endocrine cells in any gland of the endocrine system. These malignancies may show an aggressive behavior and resistance to the common anticancer therapies. The etiopathogenesis of these tumors remains mostly unknown. The normal embryological development and differentiation of several endocrine glands are regulated by specific pituitary tropins, which, in adult life, control the function and trophism of the endocrine gland. Pituitary tropins act in concert with peptide growth factors, including the insulin-like growth factors (IGFs), which are considered key regulators of cell growth, proliferation, and apoptosis. While pituitary TSH is regarded as tumor-promoting factor for metastatic thyroid cancer, the role of other pituitary hormones in endocrine cancers is uncertain. However, multiple molecular abnormalities of the IGF system frequently occur in endocrine cancers and may have a role in tumorigenesis as well as in tumor progression and resistance to therapies. Herein, we will review studies indicating a role of IGF system dysregulation in endocrine cancers and will discuss the possible implications of these findings for tumor prevention and treatment, with a major focus on cancers from the thyroid, adrenal, and ovary, which are the most extensively studied.

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 receptor functionally enhances multistage tumor progression and conveys intrinsic resistance to IGF-1R targeted therapy

The type 1 insulin-like growth factor receptor (IGF-1R) tyrosine kinase is an important mediator of the protumorigenic effects of IGF-I/II, and inhibitors of IGF-1R signaling are currently being tested in clinical cancer trials aiming to assess the utility of this receptor as a therapeutic target. Despite mounting evidence that the highly homologous insulin receptor (IR) can also convey protumorigenic signals, its direct role in cancer progression has not been genetically defined in vivo, and it remains unclear whether such a role for IR signaling could compromise the efficacy of selective IGF-1R targeting strategies. A transgenic mouse model of pancreatic neuroendocrine carcinogenesis engages the IGF signaling pathway, as revealed by its dependence on IGF-II and by accelerated malignant progression upon IGF-1R overexpression. Surprisingly, preclinical trials with an inhibitory monoclonal antibody to IGF-1R did not significantly impact tumor growth, prompting us to investigate the involvement of IR. The levels of IR were found to be significantly up-regulated during multistep progression from hyperplastic lesions to islet tumors. Its functional involvement was revealed by genetic disruption of the IR gene in the oncogene-expressing pancreatic beta cells, which resulted in reduced tumor burden accompanied by increased apoptosis. Notably, the IR knockout tumors now exhibited sensitivity to anti-IGF-1R therapy; similarly, high IR to IGF-1R ratios demonstrably conveyed resistance to IGF-1R inhibition in human breast cancer cells. The results predict that elevated IR signaling before and after treatment will respectively manifest intrinsic and adaptive resistance to anti-IGF-1R therapies.

Selective disruption of insulin-like growth factor-1 (IGF-1) signaling via phosphoinositide-dependent kinase-1 prevents the protective effect of IGF-1 on human cancer cell death

Insulin-like growth factor-1 (IGF-1) signaling system exerts a broad antiapoptotic function and plays a crucial role in resistance to anticancer therapies. Exposure of MCF-7 breast cancer cells to IGF-1 rapidly and transiently induced tyrosine phosphorylation and activation of phosphoinositide-dependent kinase-1 (PDK1). This was paralleled by Akt/protein kinase B and protein kinase C-zeta phosphorylation, at Thr(308) and Thr(410), respectively. IGF-1 treatment also enhanced PDK1 interaction with IGF-1 receptor (IGF-1R) in intact MCF-7 cells. Pulldown assays revealed that PDK1 bound IGF-1R in vitro and that the region encompassing amino acids 51-359 of PDK1 was necessary for the interaction. Synthetic peptides corresponding to IGF-1R C terminus amino acids 1295-1337 (C43) and to PDK1 amino acids 114-141 reduced in vitro IGF-1R/PDK1 interaction in a concentration-dependent manner. Loading of fluoresceinated-C43 (fluorescein isothiocyanate (FITC)-C43) into MCF-7 cells significantly reduced IGF-1R/PDK1 interaction and phosphorylation of PDK1 substrates. Moreover, FITC-C43 intracellular loading reverted the protective effect of IGF-1 on growth factor deprivation-induced cell death. Finally, the inhibition of IGF-1R/PDK1 interaction and signaling by FITC-C43 was accompanied by 2-fold enhanced killing capacity of cetuximab in human GEO colon adenocarcinoma cells and was sufficient to restore cell death in cetuximab-resistant cell clones. Thus, disruption of PDK1 interaction with IGF-1R reduces IGF-1 survival effects in cancer cells and may enhance cell death by anticancer agents.

Assessing the clinical utility of measuring Insulin-like Growth Factor Binding Proteins in tissues and sera of melanoma patients

Background

Different Insulin-like Growth Factor Binding Proteins (IGFBPs) have been investigated as potential biomarkers in several types of tumors. In this study, we examined both IGFBP-3 and -4 levels in tissues and sera of melanoma patients representing different stages of melanoma progression.

Methods

The study cohort consisted of 132 melanoma patients (primary, n = 72; metastatic, n = 60; 64 Male, 68 Female; Median Age = 56) prospectively enrolled in the New York University School of Medicine Interdisciplinary Melanoma Cooperative Group (NYU IMCG) between August 2002 and December 2006. We assessed tumor-expression and circulating sera levels of IGFBP-3 and -4 using immunohistochemistry and ELISA assays. Correlations with clinicopathologic parameters were examined using Wilcoxon rank-sum tests and Spearman-rank correlation coefficients.

Results

Median IGFBP-4 tumor expression was significantly greater in primary versus metastatic patients (70% versus 10%, p = 0.01) A trend for greater median IGFBP-3 sera concentration was observed in metastatic versus primary patients (4.9 μg/ml vs. 3.4 μg/ml, respectively, p = 0.09). However, sera levels fell within a normal range for IGFBP-3. Neither IGFBP-3 nor -4 correlated with survival in this subset of patients.

Conclusion

Decreased IGFBP-4 tumor expression might be a step in the progression from primary to metastatic melanoma. Our data lend support to a recently-described novel tumor suppressor role of secreting IGFBPs in melanoma. However, data do not support the clinical utility of measuring levels of IGFBP-3 and -4 in sera of melanoma patients.

Abnormalities of IGF-I signaling in the pathogenesis of diseases of the bone, brain, and fetoplacental unit in humans

IGF-I action is essential for the regulation of tissue formation and remodeling, bone growth, prenatal growth, brain development, and muscle metabolism. Cellular effects of IGF-I are mediated through the IGF-I receptor, a transmembrane tyrosine kinase that phosphorylates intracellular substrates, resulting in the activation of multiple intracellular signaling cascades. Dysregulation of IGF-I actions due to impairment in the postreceptor signaling machinery may contribute to multiple diseases in humans. This article will review current information on IGF-I signaling and illustrate recent results demonstrating how impaired IGF-I signaling and action may contribute to the pathogenesis of human diseases, including osteoporosis, neurodegenerative disorders, and reduced fetal growth in utero.

IGF-I protects human oral buccal mucosal epithelial cells from sodium nitroprusside-induced apoptosis via PI3-kinase

OBJECTIVE

Cancers of the head and neck account for the vast majority of all malignancies of the oral cavity. The insulin-like growth factor (IGF) family of proteins is well documented to have an important role in rescuing cells from apoptosis. While it is known the IGF proteins are present in normal oral epithelial and cancer cells its role is not fully understood. Our aim was to study the ability of IGFs to rescue sodium nitroprusside (SNP)-induced apoptotic normal oral epithelial cells in vitro.

DESIGN

Cultured normal human oral keratinocytes (NOKs) or epithelial cells were used. Apoptosis was induced by SNP then cells were exposed to IGF-I or IGF-II to rescue them. Cell viability was assessed by ELISA (for cell death and caspase 3) and FACS analysis; post receptor effects of IGF-I or IGF-II were assessed by [(3)H] thymidine incorporation. Cell signaling events were measured by western blotting using antibodies against phosphorylated Akt or p42/p44 MAPK, and measuring PI3-K activity by ELISA.

RESULTS

SNP induced apoptosis of NOKs and activated the PI3-K/Akt survival pathway. Exposing cells to IGF proteins prevented their apoptosis. IGF-I and -II caused significant increases in PI3-K, but not MAPK, activity. SNP and LY294002, a PI3-K inhibitor, both caused a significant rise in caspase 3 release from NOKs which was reduced in the presence of IGFs.

CONCLUSIONS

The data establishes the importance of IGF-activated PI3-K in rescuing cells from apoptosis. It lends further evidence to the significance of IGF proteins in the possible development of oral cancer.

Loss of responsiveness to IGF-I in cells with reduced cathepsin L expression levels

The lysosomal cysteine proteinase cathepsin L is involved in proteolytic processing of internalized proteins. In transformed cells, where it is frequently overexpressed, its intracellular localization and functions can be altered. Previously, we reported that treatment of highly metastatic, murine carcinoma H-59 cells with small molecule cysteine proteinase inhibitors altered the responsiveness of the type I insulin-like growth factor (IGF-I) receptor and consequently reduced cell invasion and metastasis. To assess more specifically the role of cathepsin L in IGF-I-induced signaling and tumorigenicity, we generated H-59 subclones with reduced cathepsin L expression levels. These clonal lines showed an altered responsiveness to IGF-I in vitro, as evidenced by (i) loss of IGF-I-induced receptor phosphorylation and Shc recruitment, (ii) reduced IGF-I (but not IGF-II)-induced cellular proliferation and migration, (iii) decreased anchorage-independent growth and (iv) reduced plasma membrane levels of IGF-IR. These changes resulted in increased apoptosis in vivo and an impaired ability of the cells to form liver metastases. The results demonstrate that cathepsin L expression levels regulate cell responsiveness to IGF-I and thereby identify a novel function for cathepsin L in the control of the tumorigenic/metastatic phenotype.

The emerging role of the insulin-like growth factor pathway as a therapeutic target in cancer

The insulin-like growth factor signaling pathway is important in many human cancers based on data from experimental models as well as epidemiological studies. Important therapies targeted at this pathway have been or are being developed, including monoclonal antibodies to the insulin-like growth factor-I receptor and small molecule inhibitors of the tyrosine kinase function of this receptor. These investigational therapies are now being studied in clinical trials. Emerging data from phase I trials are encouraging regarding the safety of the monoclonal antibodies. In this manuscript, the rationale for targeting the insulin-like growth factor system is reviewed in addition to a summary of the available clinical trial data.

Modifying IGF1 activity: an approach to treat endocrine disorders, atherosclerosis and cancer

Insulin-like growth factor 1 (IGF1) is a polypeptide hormone that has a high degree of structural similarity to human proinsulin. Owing to its ubiquitous nature and its role in promoting cell growth, strategies to inhibit IGF1 actions are being pursued as potential adjunctive measures for treating diseases such as short stature, atherosclerosis and diabetes. In addition, most tumour cell types possess IGF1 receptors and conditions in the tumour microenvironment, such as hypoxia, can lead to enhanced responsiveness to IGF1. Therefore, inhibiting IGF1 action has been proposed as a specific mechanism for potentiating the effects of existing anticancer therapies or for directly inhibiting tumour cell growth.

Regional lymph node metastases; a singular manifestation of the process of clinical metastases in cancer: contemporary animal research and clinical reports suggest unifying concepts

Research results from laboratory animals and human clinical reports provide insight into cancer cell disseminations and elaborate the complex metastatic cascade of cells into both regional lymph nodes and other distant organs. Critical appraisal of clinical trials indicates that lymph node metastases are themselves non-lethal, but indicate prognosis, confirming laboratory conclusions. Distant vital organ metastases can be resected with long term survival in highly selective situations, demonstrating metastatic specificity in oligometastatic disease. Appreciating lymphatic system embryology, anatomy, and physiology is necessary for understanding lymph node metastases. The primary lymphatic system function was to return interstitial fluid to the circulation. Later evolutionary insertion of lymphocyte collections in lymph nodes interrupting lymph flow completed a system of analyzing external antigens to enable adaptive immunologic responses. Human cancers seldom elicit major immunological responses; they are not generally "foreign" enough. Therefore, lymphatic metastases have little meaning in evolutionary terms. Organ specificity of both lymphatic and distant metastases occurs as metastatic cells lie dormant, but grow selectively only in liver, lung, bone, or lymph nodes. These organ specific metastatic cells have little ability to produce different organ site clinical metastases. Thus, laboratory findings and clinical correlations emphasize that surgical lymph node removal should be de-emphasized or omitted. More physiological approaches to the highly manipulable multi-step processes of clinical metastases arising from host microenvironments will eventually prevail.

The role of the IGF system in cancer growth and metastasis: overview and recent insights

IGF-I receptor (IGF-IR) signaling and functions are mediated through the activities of a complex molecular network of positive (e.g., type I IGF) and negative (e.g., the type II IGF receptor, IGF-IIR) effectors. Under normal physiological conditions, the balance between the expression and activities of these molecules is tightly controlled. Changes in this delicate balance (e.g., overexpression of one effector) may trigger a cascade of molecular events that can ultimately lead to malignancy. In recent years, evidence has been mounting that the IGF axis may be involved in human cancer progression and can be targeted for therapeutic intervention. Here we review old and more recent evidence on the role the IGF system in malignancy and highlight experimental and clinical studies that provide novel insights into the complex mechanisms that contribute to its oncogenic potential. Controversies arising from conflicting evidence on the relevance of IGF-IR and its ligands to human cancer are discussed. Our review highlights the importance of viewing the IGF axis as a complex multifactorial system and shows that changes in the expression levels of any one component of the axis, in a given malignancy, should be interpreted with caution and viewed in a wider context that takes into account the expression levels, state of activation, accessibility, and functionality of other interacting components. Because IGF targeting for anticancer therapy is rapidly becoming a clinical reality, an understanding of this complexity is timely because it is likely to have an impact on the design, mode of action, and clinical outcomes of newly developed drugs.

Regional lymph node metastases, a singular manifestation of the process of clinical metastases in cancer: contemporary animal research and clinical reports suggest unifying concepts

The multistep complex metastatic cascade in cancer has been extensively studied in recent years. In addition, the concept of metastatic organ specificity has been elaborated. Histological studies in clinical situations have become far more sophisticated, enabling the frequent discovery of minor collections of cells in bone marrow and lymph nodes. Pertinent clinical evidence of the selective nodal metastatic pattern exists in differentiated thyroid cancer in younger, low-risk patients, yet none of the published risk group definitions indicate that lymph node metastases have a relationship to thyroid cancer survival. This unique clinical situation with very frequent nodal metastases but excellent survival is replicated in carcinoid cancers of the gastrointestinal tract. The lymph node metastatic frequency without distant organ metastases in these two human cancers help cement the understanding gained from laboratory and animal research regarding metastatic specificity and hopefully will help place the role of lymph node metastases generally and their surgical removal on a more scientifically and logically based understanding. More broadly, the elaboration of the frequency of metastatic cell dissemination to distant organs as well as lymph nodes, and comprehension of the metastatic cascade with metastatic specificity may reorient our understanding of the evolution from metastatic cells to clinical metastatic disease. Additionally, these concepts reemphasize that lymph node metastases are indicators, not governors, of distant metastases and survival, and add the assumption that metastatic tumor cells and tumor cell clusters, and perhaps even micrometastases in other organs, are themselves only indicators and not governors of distant metastases and survival in human cancers since they represent dormant metastases prior to their host microenvironmental changes that, on rare occasions, lead to angiogenesis and clinical metastases. Thus, the future may allow us to abandon some aspects of our surgical or systemic attack on clinical cancer metastases, such as lymph node removal or use of toxic chemotherapy, but open the door to more physiological and hopefully less traumatic approaches to the highly manipulable multistep genetic and physiological process of metastatic development. The future biological models of clinical cancer behavior will have to incorporate aspects of understanding the intricate metastatic cascade, and particularly the host microenvironmental factors that permit or prevent progressive growth of dormant cells or cell clusters to clinical metastases.

High IGFBP-3 levels in marrow plasma in early-stage MDS: effects on apoptosis and hemopoiesis

The pathophysiology of the myelodysplastic syndromes (MDS) is incompletely understood. Tumor necrosis factor (TNF)alpha levels are elevated, particularly in early-stage MDS, and apoptosis in marrow cells is upregulated. Observations in other models have shown a role for insulin-like growth factor binding protein 3 (IGFBP-3) in TNFalpha-mediated apoptosis. We observed increased levels of IGFBP-3 in the marrow plasma of patients with MDS (P = 0.005) and hypothesized that altered IGFBP-3 levels contribute to the dysregulation of hemopoiesis in MDS by affecting proliferation and apoptosis. Western analysis of marrow plasma from MDS patients revealed an increase in the ratio of intact vs fragmented IGFBP-3 in early-stage MDS (relative to controls) that decreased with MDS disease progression, suggesting increased proteolysis with more advanced disease. Thus, these results provide evidence for dysregulation of IGFBP-3 in patients with MDS. While the data are complex, they are consistent with a modulatory effect of IGFBP-3 on hemopoiesis in MDS. Conceivably, understanding these mechanisms may allow for the development of novel therapeutic strategies.

Blockade of Paracrine Supply of Insulin-Like Growth Factors Using Neutralizing Antibodies Suppresses the Liver Metastasis of Human Colorectal Cancers

Environmental stimuli, such as organ-specific growth factors, can influence the metastatic potential of a tumor. The liver is the main source of insulin-like growth factors (IGFs). The importance of IGF signal in hepatic metastasis has been clarified mainly by IGF-I receptor targeting strategies. This study aims to confirm these precedent reports by novel tool, neutralizing antibodies against IGFs and to show that IGFs are promising therapeutic targets for hepatic metastasis in vivo. Hepatic metastasis was induced by intrasplenic injection of human colorectal cancer cell line, HT29. The antimetastatic effects of three antibodies (anti-mouse IGF-I, anti-mouse IGF-II, and anti-human/mouse IGF-II designated KM1468) were tested singly or in combination in the early phase of metastasis. The dose escalation effect of KM1468 and its survival benefit were examined in the early and late phases of metastasis. The mechanism of IGF neutralization was investigated with immunohistochemistry. Dual neutralization of paracrine IGF-I and IGF-II showed modest additive antimetastatic effects than single neutralization of IGF-I or IGF-II. In any phase of metastasis, neutralization led to significant tumor growth inhibition and longer survival. Dose escalation of KM1468 influenced survival only in the late phase of metastasis. Apoptosis increased significantly in the antibody-treated group compared with the control group (P = 0.0025) In conclusion, IGFs are promising therapeutic targets for hepatic metastases of colorectal cancers. However, the IGF dependency is probably variable in the metastatic process.

Expression of insulin-like growth factor 1 and receptor in ischemic rats treated with human marrow stromal cells

Human bone marrow stromal cells (hMSCs) enhance neurological recovery after stroke in rodents, possibly via induction of growth factors. We therefore elected to test the effects of hMSC treatment on insulin-like growth factor 1 (IGF-1), which plays an important role in growth, development, neuroprotection and repair in the adult. Rats (n=57) were subjected to permanent middle cerebral artery occlusion (MCAo) and injected intravenously with 3 x 10(6) hMSCs or phosphate-buffered saline (PBS) at 1 day after MCAo. Functional outcome was measured after MCAo using a modified Neurological Severity Score (mNSS). Gene expression of IGF-1 and IGF-1 receptor (IGF-1R) in the ischemic brain tissue were measured at 2 and 7 days after MCAo using reverse transcription-polymerase chain reaction (RT-PCR). Immunohistochemistry was performed to measure the expression of bromodeoxyuridine (BrdU), doublecortin (DCX), IGF-1 and IGF-1R at 7, 14 and 30 days after MCAo. Treatment of MCAo with hMSCs significantly improved functional recovery from 14 to 30 days. MAB1281-labeled hMSCs entered the ischemic brain and increased time-dependently. hMSC treatment significantly increased IGF-1 mRNA and BrdU(+), DCX(+), IGF-1(+) and IGF-1R(+) cells compared to PBS-treated rats (p<0.05). The percentage of BrdU(+) or DCX(+) cells colocalized with IGF-1 increased in the hMSC-treated rats compared to the PBS-treated rats (p<0.05). IGF-1 and IGF-1R may contribute to improved functional recovery and increased neurogenesis after treatment of stroke with hMSCs.

Relationship between low-molecular-weight insulin-like growth factor-binding proteins, caspase-3 activity, and oocyte quality

Bovine follicular atresia is associated with the apoptosis of granulosa cells and the subsequent loss of oocyte competence through the reduction of cellular contact (e.g., gap junctions). Several components of the insulin-like growth factor (IGF) system are thought to affect follicular atresia. Whereas the IGF-binding proteins (IGFBPs) are present in varying quantities throughout follicular development, IGFBP-5 appears to be present only during atresia, in parallel with its regulation in other tissue remodeling systems. However, to our knowledge, no connection has yet been made between atresia, low-molecular-weight IGFBP content, and oocyte quality in the bovine ovary. Caspases are actively involved in ovarian follicular atresia, and apoptosis in antral follicles is caspase-3-dependent. Hence, the aim of the present study was to investigate the use of these factors in the assessment of oocyte quality and developmental potential. Oocytes were aspirated, morphologically classified, and individually matured in vitro. The follicular fluid and granulosa cells of these follicles were analyzed for IGFBP profile and caspase-3 activity, respectively. A significant correlation was found between the presence of low-molecular-weight IGFBPs in bovine follicular fluid and caspase-3 activity of granulosa cells isolated from individual follicles. The highest percentage of development to the blastocyst stage was observed in oocytes from slightly atretic follicles. This group of oocytes contained an equal proportion of oocytes at grades 1-3. These data demonstrate that low-molecular-weight IGFBP profile is a more reliable method than the traditional morphological assessment of oocytes and can be used as an effective marker of developmentally competent oocytes. Importantly, these results have implications for the use of noninvasive follicular fluid markers in the selection of competent oocytes to improve outcomes of in vitro fertilization.

14-3-3σ Mediation of Cell Cycle Progression Is p53-independent in Response to Insulin-like Growth Factor-I Receptor Activation

We investigated the role of 14-3-3sigma protein in insulin-like growth factor-I (IGF-I) receptor signaling. It has been previously shown that 14-3-3sigma negatively regulates cell cycle especially in response to p53-sensitive DNA damage. In this study we demonstrated that 14-3-3sigma is a positive mediator of IGF-I receptor-induced cell proliferation. Treatment with IGF-I increased 14-3-3sigma mRNA and protein levels about 4-fold, in a time-dependent manner in MCF-7 breast cancer cells. Preincubation with the phosphoinositide 3'-kinase inhibitor LY294002 significantly reduced the effects of IGF-I on 14-3-3sigma gene expression in these cells, suggesting that this effect of IGF-I occurs via the phosphoinositide 3'-kinase pathway. 14-3-3sigma is induced by IGF-I in MCF-7 cells, which express wild-type p53, as well as in MCF-7 cells transfected with a small interference RNA targeting duplex that reduced p53 expression levels. These results suggest that IGF-I induces 14-3-3sigma expression in a manner that is independent of p53. Using the small interference RNA strategy, we demonstrated that a 70-75% reduction of 14-3-3sigma mRNA levels resulted in a similar decrease in the effects of IGF-I on cell cycle progression and proliferation in MCF-7 cells. This effect was also associated with a reduction in IGF-I-induced cyclin D1 expression. Taken together, these results suggest that 14-3-3sigma positively mediates IGF-I-induced cell cycle progression.

Loss of Tumorigenicity and Metastatic Potential in Carcinoma Cells Expressing the Extracellular Domain of the Type 1 Insulin-Like Growth Factor Receptor

The receptor for the type 1 insulin-like growth factor (IGF-IR) was identified as a major regulator of the malignant phenotype and a target for cancer therapy. In the present study, a novel IGF-IR mutant consisting of the entire extracellular domain of the receptor (IGFIR(933)) was genetically engineered and expressed in highly metastatic H-59 murine lung carcinoma cells. We show here that the cells expressed a truncated heterotetramer (beta(m)-alpha-alpha-beta(m)) that was secreted into the medium and could neutralize the effects of exogenous IGF-I, thus diminishing IGF-I-induced signaling and blocking IGF-I-mediated cellular functions such as cell proliferation, invasion, and survival. In vivo, tumor incidence and growth rate were markedly reduced in mice inoculated s.c. with H-59/IGFIR(933) cells. Moreover, after the intrasplenic/portal inoculation of these cells, there was a 90% reduction in the incidence of hepatic metastases and a significant increase in the long-term, disease-free survival of the mice compared with controls. Our results identify the IGFIR(933) as a potent antitumorigenic and antimetastatic agent with potential applications for cancer gene therapy.

Dual Regulation of MMP-2 Expression by the Type 1 Insulin-like Growth Factor Receptor

The matrix metalloproteinase (MMP)-2 has been recognized as a major mediator of basement membrane degradation, angiogenesis, tumor invasion, and metastasis. The factors that regulate its expression have not, however, been fully elucidated. We previously identified the type I insulin-like growth factor (IGF-I) receptor as a regulator of MMP-2 synthesis. The objective of the present study was to investigate the signal transduction pathway(s) mediating this regulation. We show here that in Lewis lung carcinoma subline H-59 cells treated with IGF-I (10 ng/ml), the PI 3-kinase (phosphatidylinositol 3'-kinase) /protein kinase B (Akt) and C-Raf/ERK pathways were activated, and MMP-2 promoter activity, mRNA, and protein synthesis were induced. MMP-2 induction was blocked by the PI 3-kinase inhibitors LY294002 and wortmannin, by overexpression of a dominant-negative Akt or wild-type PTEN (phosphatase and tensin homologue deleted on chromosome 10), and by rapamycin. In contrast, a MEK inhibitor PD98059 failed to reduce MMP-2 promoter activation and actually increased MMP-2 mRNA and protein synthesis by up to 30%. Interestingly, suppression of PI 3-kinase signaling by a dominant-negative Akt enhanced ERK activity in cells stimulated with 10 ng/ml but not with 100 ng/ml IGF-I. Furthermore, at the higher (100 ng/ml) IGF-I concentration, C-Raf and ERK, but not PI 3-kinase activation, was enhanced, and this resulted in down-regulation of MMP-2 synthesis. This effect was reversed in cells expressing a dominant-negative ERK mutant. The results suggest that IGF-I can up-regulate MMP-2 synthesis via PI 3-kinase/Akt/mTOR (the mammalian target of rapamycin) signaling while concomitantly transmitting a negative regulatory signal via the Raf/ERK pathway. The outcome of IGF-IR (the receptor for IGF-I) activation may ultimately depend on factors, such as ligand bioavailability, that can shift the balance preferentially toward one pathway or the other.

Insulin-like growth factor (IGF)-binding protein-4 inhibits colony formation of colorectal cancer cells by IGF-independent mechanisms

Effects of insulin-like growth factor-binding protein-4 (IGFBP-4) on proliferation, colony formation, and cell migration were assessed in IGF-sensitive and -insensitive colorectal cancer cell lines. In IGF-insensitive Isreco-1 cells, overexpression of IGFBP-4 reduced colony formation but not cell proliferation and migration, whereas exogenous IGF-II had no effect. In IGF-dependent LS1034 cells, IGFBP-4 inhibited all parameters of growth tested, whereas IGF-II partially restored reduced proliferation and cell migration only. In Isreco-2 cells, which lack endogenous IGF expression but are IGF sensitive, colony formation was also reduced by IGFBP-4. Therefore, specific parameters of malignant progression of colon carcinoma cells are distinctly affected by IGF-dependent and IGF-independent effects of IGFBP-4.

Type 1 insulin-like growth factor regulates MT1-MMP synthesis and tumor invasion via PI 3-kinase/Akt signaling

The membrane type 1 matrix metalloproteinase (MT1-MMP) has been identified as a major activator of MMP-2 - a process involving the formation of a trimolecular complex with TIMP-2. We previously identified the IGF-I receptor as a positive regulator of MMP-2 synthesis. Here, we investigated the role of IGF-IR in the regulation of MT1-MMP. Highly invasive Lewis lung carcinoma subline H-59 cells express MT1-MMP and utilize it to activate their major extracellular matrix degrading proteinase-MMP-2. These cells were transiently transfected with a plasmid vector expressing a luciferase reporter gene downstream of the mouse MT1-MMP promoter. IGF-I treatment increased luciferase activity in the transfected cells by up to 10-fold and augmented endogenous MT1-MMP mRNA and protein synthesis by up to 2-3-fold, relative to controls. MT1-MMP induction and invasion were blocked by the PI 3-kinase inhibitors LY294002 and wortmannin and by rapamycin, but not by the MEK inhibitor PD98059. Overexpression of a dominant negative Akt mutant or of the tumor suppressor phosphatase and tensin homologue, PTEN, in these cells also caused a significant reduction in MT1-MMP expression and invasion. The results demonstrate that IGF-IR controls tumor cell invasion by coordinately regulating MMP-2 expression and its MT1-MMP-mediated activation and identify PI 3-kinase/Akt/mTOR signaling as critical to this regulation.

Regulation of insulin-like growth factor type I (IGF-I) receptor kinase activity by protein tyrosine phosphatase 1B (PTP-1B) and enhanced IGF-I-mediated suppression of apoptosis and motility in PTP-1B-deficient fibroblasts

The insulin-like growth factor type I (IGF-I) receptor (IGF-IR), activated by its ligands IGF-I and IGF-II, can initiate several signal transduction pathways that mediate suppression of apoptosis, proliferation, differentiation, and transformation. Here we investigated the regulation of IGF-IR activation and function by protein tyrosine phosphatase 1B (PTP-1B). Coexpression of PTP-1B with a beta-chain construct of the IGF-IR (betaWT) inhibited IGF-IR kinase activity in fission yeast Schizosaccharomyces pombe, in COS cells, and in IGF-IR-deficient fibroblasts. In both spontaneously immortalized and simian virus 40 T antigen-transformed embryonic fibroblast cell lines derived from PTP-1B knockout mice, IGF-I induced higher levels of IGF-IR autophosphorylation and kinase activity than were induced in PTP-1B-expressing control cells. PTP-1B-deficient cells exhibited enhanced IGF-I-mediated protection from apoptosis in response to serum withdrawal or etoposide killing, as well as enhanced plating efficiency and IGF-I-mediated motility. Reexpression of PTP-1B in spontaneously immortalized fibroblasts resulted in decreased IGF-IR and AKT activation, as well as decreased protection from apoptosis and decreased motility. These findings demonstrate that PTP-1B can regulate IGF-IR kinase activity and function and that loss of PTP-1B can enhance IGF-I-mediated cell survival, growth, and motility in transformed cells.

Inhibition of carcinoma cell growth and metastasis by a vesicular stomatitis virus G-pseudotyped retrovector expressing type I insulin-like growth factor receptor antisense

A replication-defective, vesicular stomatitis virus G-pseudotyped, Moloney murine leukemia virus retroviral vector (vLTR-IGF-IR(AS)) was generated in which a type I insulin-like growth factor receptor (IGF-IR) antisense fragment is expressed in a bicistronic mRNA with an enhanced green fluorescent protein (EGFP) reporter under the control of a potent long terminal repeat (LTR). The suitability of these retroparticles for gene therapy was tested with highly metastatic, carcinoma H-59 cells, which depend on IGF-IR expression for tumorigenicity and metastasis. Transduction with these, but not with control retroviral particles expressing EGFP only, resulted in a 70% reduction in IGF-IR levels and the loss of IGF-IR-regulated functions. Moreover, the ability of vLTR-IGF-IR(AS) retroparticle-transduced tumor cells to form experimental hepatic metastases was significantly reduced relative to controls. The results identify retrovector-mediated delivery of IGF-IR antisense as a potential strategy for cancer gene therapy.