Expression of insulin-like growth factor-1 receptor in metastatic uveal melanoma and implications for potential autocrine and paracrine tumor cell growth.

We investigated the importance of the insulin-like growth factor-1 receptor (IGF-1R) in hepatic metastases of uveal melanoma. The expression pattern of IGF-1R in archival tissue samples of hepatic metastasis from 24 patients was analyzed by immunohistochemistry. All the samples of hepatic metastases stained positive for IGF-1R. To investigate the biological role of IGF-1R on the growth of metastatic uveal melanoma, a long-term cell line obtained from a hepatic metastasis (TJU-UM001) was evaluated. TJU-UM001 expressed cell surface IGF-1R (>90%) and proliferated in response to exogenous and endogenous insulin-like growth factor-1 (IGF-1). Correlatively, anti-IGF-1R antibody completely blocked IGF-1-induced growth of TJU-UM001 cells. IGF-1 preferentially induced phosphorylation of Akt (S473) in quiescent TJU-UM001 cells, and this was blocked by anti-IGF-1R antibody. This study suggests that autocrine and paracrine mechanisms underlie IGF-1-induced growth of metastatic uveal melanoma and underscore the potential benefit of IGF-1 or IGF-1R antagonism in treatment for metastatic uveal melanoma.

Nutrient restriction and radiation therapy for cancer treatment: when less is more.

Calorie restriction (CR), or a diet modification aiming to reduce the total intake of calories by 20%-40%, has been shown to increase longevity across multiple species. Recently, there has been growing interest in investigating the potential role of CR as a treatment intervention for age-related diseases, such as cancer, because an increasing body of literature has demonstrated a metabolic component to both carcinogenesis and tumor progression. In fact, many of the molecular pathways that are altered with CR are also known to be altered in cancer. Therefore, manipulation of these pathways using CR can render cancer cells, and most notably breast cancer cells, more susceptible to standard cytotoxic treatment with radiation and chemotherapy. In this review article we demonstrate the laboratory and clinical evidence that exists for CR and show compelling evidence through the molecular pathways CR induces about how it may be used as a treatment in tandem with radiation therapy to improve our rates of disease control.

The decline and fall of the IGF-I receptor.

This review examines the effect of targeting the insulin-like growth factor 1 receptor (IGF-IR) in human cancers. The results are disappointing. The causes for the failure are discussed, as well as the possible use of the IGF-IR as a secondary target.

Growth of v-src-transformed cells in serum-free medium through the induction of growth factors.

The v-src oncogene is one of only two oncogenes capable of transforming mouse embryo fibroblasts (MEFs) lacking the IGF-IR gene (R-cells). R-/v-src cells grow robustly in the absence of serum, suggesting the hypothesis that they may produce one or more growth factors that would sustain their ability to proliferate in serum-free condition. Using proteomic approaches on serum-free conditioned media derived from v-src-transformed cells, we have identified two growth promoting factors: ostepontin and proliferin. Subsequent experiments have indicated that osteopontin plays a prevalent role in promoting growth of v-src-transformed cells in serum-deprived condition.

Inhibition of the single downstream target BAG1 activates the latent apoptotic potential of MYC.

Aberrant MYC expression is a common oncogenic event in human cancer. Paradoxically, MYC can either drive cell cycle progression or induce apoptosis. The latent ability of MYC to induce apoptosis has been termed "intrinsic tumor suppressor activity," and reactivating this apoptotic function in tumors is widely considered a valuable therapeutic goal. As a transcription factor, MYC controls the expression of many downstream targets, and for the majority of these, it remains unclear whether or not they play direct roles in MYC function. To identify the subset of genes specifically required for biological activity, we conducted a screen for functionally important MYC targets and identified BAG1, which encodes a prosurvival chaperone protein. Expression of BAG1 is regulated by MYC in both a mouse model of breast cancer and transformed human cells. Remarkably, BAG1 induction is essential for protecting cells from MYC-induced apoptosis. Ultimately, the synthetic lethality we have identified between MYC overexpression and BAG1 inhibition establishes a new pathway that might be exploited to reactivate the latent apoptotic potential of MYC as a cancer therapy.

The type 1 insulin-like growth factor receptor and resistance to DACH1.

The mammalian homolog of the Drosophila dachshund gene (DACH1) has been reported as a tumor suppressor in human breast and prostate cancers. It downregulates the epidermal growth factor receptor (EGFR) and cyclin D1. The signaling pathway of the type 1 insulin-like growth factor receptor (IGF-IR) is known to be responsible for the development of resistance to treatment of human cancer with antibodies to the EGFR. We have asked whether DACH1 still exerts its tumor suppressor activity in cells dependent on the IGF-IR for growth. We find that in cells growing in IGF-1 (and unresponsive to EGF), DACH1 is devoid of tumor suppressor activity.

Expression of micro-RNA-145 is regulated by a highly conserved genomic sequence 3' to the pre-miR.

Micro-RNA-145 (miR145), a tumor suppressor miR, dramatically inhibits growth of cancer cells in culture and plays a significant role in human stem cells differentiation. We have isolated a human genomic sequence of 864 bp comprising the pre-miR and its flanking sequences. The cloned miR145 genomic sequence expresses a mature miR145 in transfected cells. We show here that flanking sequences on either side of the pre-miR sequence can modulate its expression levels. Surprisingly, a highly conserved sequence 3' to the pre-miR plays a crucial role in miR145 expression.

Regulation of microRNA-145 by growth arrest and differentiation.

MicroRNA145 (miR145), a tumor suppressor miR, has been reported to inhibit growth of human cancer cells, to induce differentiation and to cause apoptosis, all conditions that result in growth arrest. In order to clarify the functional effects of miR145, we have investigated its expression in diverse conditions and different cell lines. Our results show that miR145 levels definitely increase in differentiating cells and also in growth-arrested cells, even in the absence of differentiation. Increased expression during differentiation sometimes occurs as a late event, suggesting that miR145 could be required either early or late during the differentiation process.

Mutual interaction and reciprocal down-regulation between c-met and insulin receptor substrate-1.

The insulin receptor substrate-1 (IRS-1) and c-met, the receptor for the hepatocyte growth factor (HGF) co-immuno-precipitate from lysates treated with the respective antibodies. The interaction between IRS-1 and c-met requires a tyrosyl phosphorylated IRS-1 and results in reciprocal down-regulation. IRS-1 inhibits cell motility, while the activated c-met promotes it. These and other results suggest an explanation for reports in the literature indicating that c-met levels are high and IRS-1 levels are low in human cancer metastases.

microRNA, cell cycle, and human breast cancer.

The discovery of microRNAs as a novel class of gene expression regulators has led to a new strategy for disease diagnostics and therapeutics. Cell cycle, cell proliferation, and tumorigenesis are all regulated by microRNAs. Several general principles linking microRNAs and cancer have been recently reviewed; therefore, the current review focuses specifically on the perspective of microRNAs in control of cell cycle, stem cells, and heterotypic signaling, as well as the role of these processes in breast cancer. Altered abundance of cell cycle regulation proteins and aberrant expression of microRNAs frequently coexist in human breast cancers. Altered microRNA expression in breast cancer cell lines is associated with altered cell cycle progression and cell proliferation. Indeed, recent studies have demonstrated a causal role for microRNA in governing breast tumor suppression or collaborative oncogenesis. This review summarizes the current understanding of the role for microRNA in regulating the cell cycle and summarizes the evidence for aberrant microRNA expression in breast cancer. The new evidence for microRNA regulation by annotated genes and the involvement of microRNA in breast cancer metastasis are discussed, as is the potential for microRNA to improve breast cancer diagnosis and therapy.

The microRNA miR-92 increases proliferation of myeloid cells and by targeting p63 modulates the abundance of its isoforms.

MicroRNAs (miRs) are 21- to 23-nucleotide RNA molecules that regulate the stability or translational efficiency of target messenger RNAs of proteins involved in cell growth and apoptosis. miR-92 is part of the mir-17-92 cluster, which comprises members with an effect on cell proliferation. However, the role of miR-92 is unknown, and its targets have not been identified. Here, we describe a mechanism through which miR-92 contributes to regulate cell proliferation. Using a miR-92 synthetic double-strand oligonucleotide, we demonstrate that miR-92 increases 32D myeloid cell proliferation and 5-bromo-2-deoxyuridine (BrdU) incorporation and inhibits cell death. The effect is miR-92 specific since the miR-92 antagomir inhibits cell proliferation. Moreover, we show that miR-92 acts by modulating p63-isoform abundance through down-regulatation of endogenous DeltaNp63beta. Using luciferase reporters containing p63 3'UTR fragments with wild-type or mutant miR-92 complementary sites, we demonstrate that the wild-type 3'UTR is a direct target of miR-92. Finally, we observed that a miR-92-resistant DeltaNp63beta isoform (without 3'UTR) inhibits cell proliferation and parallels the effect of the antagomir. We conclude that one of the molecular mechanisms through which miR-92 increases cell proliferation is by negative regulation of an isoform of the cell-cycle regulator p63.

Growth inhibition by microRNAs that target the insulin receptor substrate-1.

We have examined several microRNAs (miRs) indicated by the databases as targeting the signaling pathway of the type-1 insulin-like growth factor receptor (IGF-IR). Most of the miRs tested had multiple targets, as expected, leading to cell death. However, miR145 seemed to affect its tumor suppressor activity largely by downregulating the docking protein of the IGF-IR, the insulin receptor substrate-1 (IRS-1). These results suggest that, despite the many targets provided by the databases, in some cases a single target can be predominant in determining the end results.

Mechanism of growth inhibition by MicroRNA 145: the role of the IGF-I receptor signaling pathway.

MicroRNA 145 (miR145) has been proposed as a tumor suppressor. It was previously shown that miR145 targets the 3' UTR of the insulin receptor substrate-1 (IRS-1) and dramatically inhibits the growth of colon cancer cells. miR145 also targets the type 1 insulin-like growth factor receptor (IGF-IR). We show here that an IRS-1 lacking its 3' UTR is no longer down-regulated by miR145 and rescues colon cancer cells from miR145-induced inhibition of growth. An IGF-IR resistant to miR145 (again by elimination of its 3' UTR) is not down-regulated by miR145 but fails to rescue colon cancer cells from growth inhibition. These and other results, taken together, indicate that down-regulation of IRS-1 plays a significant role in the tumor suppressor activity of miR145.

AMG 479, a fully human anti-insulin-like growth factor receptor type I monoclonal antibody, inhibits the growth and survival of pancreatic carcinoma cells.

Pancreatic carcinoma is a leading cause of cancer deaths, and recent clinical trials of a number of oncology therapeutics have not substantially improved clinical outcomes. We have evaluated the therapeutic potential of AMG 479, a fully human monoclonal antibody against insulin-like growth factor (IGF) type I receptor (IGF-IR), in two IGF-IR-expressing pancreatic carcinoma cell lines, BxPC-3 and MiaPaCa2, which also differentially express insulin receptor (INSR). AMG 479 bound to IGF-IR (K(D) 0.33 nmol/L) and blocked IGF-I and IGF-II binding (IC(50) < 0.6 nmol/L) without cross-reacting to INSR. AMG 479 completely inhibited ligand-induced (IGF-I, IGF-II, and insulin) activation of IGF-IR homodimers and IGF-IR/INSR hybrids (but not INSR homodimers) leading to reduced cellular viability in serum-deprived cultures. AMG 479 inhibited >80% of basal IGF-IR activity in BxPC-3 and MiaPaCa2 xenografts and prevented IGF-IR and IGF-IR/INSR hybrid activation following challenge with supraphysiologic concentrations of IGF-I. As a single agent, AMG 479 inhibited (∼ 80%) the growth of pancreatic carcinoma xenografts, and long-term treatment was associated with reduced IGF-IR signaling activity and expression. Efficacy seemed to be the result of two distinct biological effects: proapoptotic in BxPC-3 and antimitogenic in MiaPaCa2. The combination of AMG 479 with gemcitabine resulted in additive inhibitory activity both in vitro and in vivo. These results indicate that AMG 479 is a clinical candidate, both as a single agent and in combination with gemcitabine, for the treatment of patients with pancreatic carcinoma

Customizing the targeting of IGF-1 receptor.

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

The insulin receptor substrate-1: a biomarker for cancer?

This review focuses on IRS-1 and the evidence of its role in cell transformation. The literature strongly suggests that IRS-1 should be considered a biomaker for cancers susceptible to IGF-IR targeting. In addition, I would like to propose that IRS-1 may have a more general role in cancer, and could be considered as a protein having the opposite effect of tumor suppressors, a sort of anti-p53 molecule.

The role of insulin receptor substrate-1 in the oncogenicity of simian virus 40 T antigen.

The Simian Virus 40 large T antigen (Tag) and the insulin receptor substrate-1 (IRS-1) interact with each other. Tag is a nuclear protein even in the absence of IRS-1, but IRS-1 is required for occupancy and activation by Tag of the ribosomal DNA (rDNA), cyclin D1 and c-myc promoters. Our results indicate that IRS-1 plays a significant role in Tag activation of cell cycle progression genes.

Regulation of insulin receptor substrate-1 expression levels by caveolin-1.

The insulin receptor substrate-1 (IRS-1), a docking protein of the type 1 insulin-like growth factor receptor (IGF-IR) plays a significant role in cell proliferation and differentiation. The expression of IRS-1 is down-regulated in mouse embryo fibroblasts (MEFs) with a deletion of caveolin-1 (cav1) genes (KO cells). Levels of IRS-1 mRNA are not affected. Re-introduction of cav1 into KO cells rescues IRS-1 expression. Stabilization of protein levels is reciprocal and a strict correlation between IRS-1 and cav1 levels was confirmed in five cell lines, and in mouse tissues. IRS-1 binds through its phosphotyrosine binding (PTB) domain to tyrosine 14 (Y14) of cav1, the residue phosphorylated by IGF-1 stimulation and by v-src. The down-regulation of IRS-1 in cav-/- cells occurs via the proteasome pathway. These results indicate a novel mechanism for the regulation of IRS-1 expression levels, an important finding in view of IRS-1 role in cell proliferation and transformation.

The role of insulin receptor substrate-1 in transformation by v-src.

The insulin receptor substrate-1 (IRS-1), a docking protein for both the insulin (InR) and the insulin-like growth factor-1 (IGF-IR) receptors, sends a mitogenic, anti-differentiation and transforming signal. We now show that down-regulation of IRS-1 in cells transformed by v-src reverses the transformed phenotype (growth in serum-free medium and colony formation in soft agar). IRS-1 translocates to nuclei and is found in the cyclin D1 and rDNA promoters. Stat3, which is activated by src, requires both IRS-1 and src for promoter occupancy. IRS-1 (by itself or in combination with src) also markedly increases transcription from these two promoters. We also show that IRS-1 binds to src via its two PI3-K binding tyrosine residues, and that these two residues are required for transformation of mammary cancer cells expressing v-src. Taken together, these results indicate a significant role of IRS-1 in the activation of cell cycle progression genes and transformation of cells by v-src.