Selective Activation of Insulin Receptor Substrate-1 and -2 in Pleural Mesothelioma Cells

ASPSCR1::TFE3-mediated upregulation of insulin receptor substrate 2 (IRS-2) activates PI3K/AKT signaling and promotes malignant phenotype

The ASPSCR1::TFE3 fusion gene, resulting from chromosomal translocation, is detected in alveolar soft part sarcoma (ASPS) and a subset of renal cell carcinomas (RCC). The ASPSCR1::TFE3 oncoprotein, functioning as an aberrant transcription factor, contributes to tumor development and progression by inappropriately upregulating target genes. Here, we identified insulin receptor substrate 2 (IRS-2), a cytoplasmic adaptor protein, as a novel transcriptional target of ASPSCR1::TFE3. Ectopic expression of ASPSCR1::TFE3 led to increased IRS-2 mRNA and protein levels. Chromatin immunoprecipitation and luciferase assays demonstrated that ASPSCR1::TFE3 bound to the IRS-2 promoter region and enhanced its transcription. Moreover, IRS-2 was highly expressed in the ASPSCR1::TFE3-positive RCC cell line FU-UR1, while small interfering RNA-mediated depletion of ASPSCR1::TFE3 markedly decreased IRS-2 mRNA and protein levels. Functionally, IRS-2 knockdown attenuated activation of the PI3K/AKT pathway and reduced proliferation, migration, invasion, adhesion, and clonogenicity in FU-UR1 cells. Pharmacological inhibition of IRS-2 also reduced AKT activation as well as cell viability, clonogenicity, migration, invasion, and adhesion. These findings suggest that IRS-2, regulated by ASPSCR1::TFE3, promotes tumor progression by activating PI3K/AKT signaling and enhancing the malignant phenotype.

High risk genetic variants of human insulin receptor substrate 1(IRS1) infer structural instability and functional interference

Insulin receptor substrate 1(IRS1) is a signaling adapter protein encoded by the IRS1 gene. This protein delivers signals from insulin and insulin-like growth factor-1(IGF-1) receptors to the phosphatidylinositol 3-kinases (P13K)/protein kinase B (Akt) and Extracellular signal-regulated kinases (Erk) - Mitogen-activated protein (MAP) kinase pathways, which regulate particular cellular processes. Mutations in this gene have been linked to type 2 diabetes mellitus, a heightened risk of insulin resistance, and an increased likelihood of developing a number of different malignancies. The structure and function of IRS1 could be severely compromised as a result of single nucleotide polymorphism (SNP) type genetic variants. In this study, we focused on identification of the most harmful non-synonymous SNPs (nsSNPs) of the IRS1 gene as well as prediction of their structural and functional consequences. Six different algorithms made the initial prediction that 59 of the 1142 IRS1 nsSNPs would have a negative impact on the protein structure. In-depth evaluations detected 26 nsSNPs located inside the functional domains of IRS1. Following that, 16 nsSNPs were identified as more harmful based on conservation profile, hydrophobic interaction, surface accessibility, homology modelling, and inter-atomic interactions. Following an in-depth analysis of protein stability, M249T (rs373826433), I223T (rs1939785175) and V204G (rs1574667052) were identified as three most deleterious SNPs and were subjected to molecular dynamics simulation for further insights. These findings will help us understand the implications for disease susceptibility, cancer progression, and the efficacy of therapeutic development against IRS1 gene mutants.Communicated by Ramaswamy H. Sarma.

Antagonist of Growth Hormone-Releasing Hormone Potentiates the Antitumor Effect of Pemetrexed and Cisplatin in Pleural Mesothelioma

Pleural mesothelioma (PM) is an aggressive cancer with poor prognosis and no effective therapies, mainly caused by exposure to asbestos. Antagonists of growth hormone-releasing hormone (GHRH) display strong antitumor effects in many experimental cancers, including lung cancer and mesothelioma. Here, we aimed to determine whether GHRH antagonist MIA-690 potentiates the antitumor effect of cisplatin and pemetrexed in PM. In vitro, MIA-690, in combination with cisplatin and pemetrexed, synergistically reduced cell viability, restrained cell proliferation and enhanced apoptosis, compared with drugs alone. In vivo, the same combination resulted in a strong growth inhibition of MSTO-211H xenografts, decreased tumor cell proliferation and increased apoptosis. Mechanistically, MIA-690, particularly with chemotherapeutic drugs, inhibited proliferative and oncogenic pathways, such as MAPK ERK1/2 and cMyc, and downregulated cyclin D1 and B1 mRNAs. Inflammatory pathways such as NF-kB and STAT3 were also reduced, as well as oxidative, angiogenic and tumorigenic markers (iNOS, COX-2, MMP2, MMP9 and HMGB1) and growth factors (VEGF and IGF-1). Overall, these findings strongly suggest that GHRH antagonists of MIA class, such as MIA-690, could increase the efficacy of standard therapy in PM.

Targeting the IGF/PI3K/mTOR Pathway and AXL/YAP1/TAZ pathways in Primary Bone Cancer

Primary bone cancers (PBC) belong to the family of mesenchymal tumors classified based on their cellular origin, extracellular matrix, genetic regulation, and epigenetic modification. The three major PBC types, Ewing sarcoma, osteosarcoma, and chondrosarcoma, are frequently aggressive tumors, highly metastatic, and typically occur in children and young adults. Despite their distinct origins and pathogenesis, these sarcoma subtypes rely upon common signaling pathways to promote tumor progression, metastasis, and survival. The IGF/PI3K/mTOR and AXL/YAP/TAZ pathways, in particular, have gained significant attention recently given their ties to oncogenesis, cell fate and differentiation, metastasis, and drug resistance. Naturally, these pathways – and their protein constituents – have caught the eye of the pharmaceutical industry, and a wide array of small molecule inhibitors and antibody drug-conjugates have emerged. Here, we review how the IGF/PI3K/mTOR and AXL/YAP/TAZ pathways promote PBC and highlight the drug candidates under clinical trial investigation.

Identification of a glycolysis-related gene signature for survival prediction of ovarian cancer patients

Background

Ovarian cancer (OV) is deemed the most lethal gynecological cancer in women. The aim of this study was to construct an effective gene prognostic model for predicting overall survival (OS) in patients with OV.

Methods

The expression profiles of glycolysis‐related genes (GRGs) and clinical data of patients with OV were extracted from The Cancer Genome Atlas (TCGA) database. Univariate, multivariate, and least absolute shrinkage and selection operator Cox regression analyses were conducted, and a prognostic signature based on GRGs was constructed. The predictive ability of the signature was analyzed using training and test sets.

Results

A gene risk signature based on nine GRGs (ISG20, CITED2, PYGB, IRS2, ANGPTL4, TGFBI, LHX9, PC, and DDIT4) was identified to predict the survival outcome of patients with OV. The signature showed a good prognostic ability for OV, particularly high‐grade OV, in the TCGA dataset, with areas under the curve (AUC) of 0.709 and 0.762 for 3‐ and 5‐year survival, respectively. Similar results were found in the test sets, and the AUCs of 3‐, 5‐year OS were 0.714 and 0.772 in the combined test set. And our signature was an independent prognostic factor. Moreover, a nomogram combining the prediction model and clinical factors was developed.

Conclusion

Our study established a nine‐GRG risk model and nomogram to better predict OS in patients with OV. The risk model represents a promising and independent prognostic predictor for patients with OV. Moreover, our study on GRGs could offer guidance for the elucidation of underlying mechanisms in future studies.

Exosomal transfer of miR-126 promotes the anti-tumour response in malignant mesothelioma: Role of miR-126 in cancer-stroma communication

MiR-126 has been shown to suppress malignant mesothelioma (MM) by targeting cancer-related genes without inducing toxicity or histopathological changes. Exosomes provide the opportunity to deliver therapeutic cargo to cancer stroma. Here, a tumour stromal model composed of endothelial cells (HUVECs), fibroblasts (IMR-90 cells), non-malignant mesothelial cells (Met-5A cells) and MM cells (H28 and MM-B1 cells) was used. The cells were treated with exosomes from HUVECs carrying endogenous (exo-HUVEC) and enriched miR-126 (exo-HUVEC^miR-126), and the uptake/turnover of exosomes; miR-126 distribution within the stroma; and effect of miR-126 on cell signalling, angiogenesis and cell proliferation were evaluated. Based on the sensitivity of MM cells to exo-HUVEC miR-126 treatment, miR-126 was distributed differently across stromal cells. The reduced miR-126 content in fibroblasts in favour of endothelial cells reduced angiogenesis and suppressed cell growth in an miR-126-sensitive environment. Conversely, the accumulation of miR-126 in fibroblasts and the reduced level of miR-126 in endothelial cells induced tube formation in an miR-126-resistant environment via VEGF/EGFL7 upregulation and IRS1-mediated cell proliferation. These findings suggest that transfer of miR-126 via HUVEC-derived exosomes represents a novel strategy to inhibit angiogenesis and cell growth in MM.

Identification of novel mutations of Insulin Receptor Substrate 1 (IRS1) in tumor samples of non-small cell lung cancer (NSCLC): Implications for aberrant insulin signaling in development of cancer

Lung cancer is the leading cause of cancer-related death, and NSCLC constitutes nearly 85%-90% of all cases. The IRS proteins function as adaptors and transmit signals from multiple receptors. Upon binding of insulin to the insulin receptor (IR), IRS1 is phosphorylated at several YXXM motifs creating docking sites for the binding of PI3Kp85, which activates AKT kinase. Therefore, we thought that gain of function mutantions of IRS1 could be related to development of lung cancer. In line with this, we wanted determine whether the IRS1 gene was mutated in the coding regions surrounding YXXM motifs. We sequenced the coding regions surrounding YXXM motifs of IRS1 using tumor samples of 42 NSCLC patients and 40 matching controls and found heterozygote p.S668T mutation in nine of 42 samples and four of nine also had the p.D674H mutation. We generated IRS1 expression vectors harboring p.S668T, p.D674H and double mutants. Expression of the mutants differentially affected insulin-induced phosphorylation of IRS1, AKT, ERK, and STAT3. Also, our mutants induced proliferation, glucose uptake, inhibited the migration of 293T cells and affected the responsiveness of the cells to cisplatin and radiation. Our results suggest that these novel mutations play a role in the phenotype of lung cancer.

Antagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of human malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive cancer with poor prognosis and limited treatment options. MPM remains a serious public health problem, and novel therapeutic strategies are urgently needed. The antitumor properties of growth hormone-releasing hormone (GHRH) antagonists have been demonstrated in different cancers; however, their influence in MPM remains unexplored. Our work shows that GHRH antagonists MIA-602 and MIA-690 reduce survival, proliferation, and migration of human MPM cell lines and primary MPM cells in vitro by modulating apoptotic and oncogenic pathways. In vivo, GHRH antagonists inhibited the growth of MPM xenografts and blunted the production of growth factors in tumors. Overall, the inhibitory activities described in this study suggest that GHRH antagonists may be considered for development of therapies for MPM.

Malignant pleural mesothelioma (MPM) is an aggressive malignancy associated with exposure to asbestos, with poor prognosis and no effective therapies. The strong inhibitory activities of growth hormone-releasing hormone (GHRH) antagonists have been demonstrated in different experimental human cancers, including lung cancer; however, their role in MPM remains unknown. We assessed the effects of the GHRH antagonists MIA-602 and MIA-690 in vitro in MPM cell lines and in primary MPM cells, and in vivo in MPM xenografts. GHRH, GHRH receptor, and its main splice variant SV1 were found in all the MPM cell types examined. In vitro, MIA-602 and MIA-690 reduced survival and proliferation in both MPM cell lines and primary cells and showed synergistic inhibitory activity with the chemotherapy drug pemetrexed. In MPM cells, GHRH antagonists also regulated activity and expression of apoptotic molecules, inhibited cell migration, and reduced the expression of matrix metalloproteinases. These effects were accompanied by impairment of mitochondrial activity and increased production of reactive oxygen species. In vivo, s.c. administration of MIA-602 and MIA-690 at the dose of 5 μg/d for 4 wk strongly inhibited the growth of MPM xenografts in mice, along with reduction of tumor insulin-like growth factor-I and vascular endothelial growth factor. Overall, these results suggest that treatment with GHRH antagonists, alone or in association with chemotherapy, may offer an approach for the treatment of MPM.

Association of IRS2 overexpression with disease progression in intrahepatic cholangiocarcinoma

Insulin receptor substrate 2 (IRS2) is a candidate driver oncogene frequently amplified in cancer and is positively associated with IRS2 expression. The overexpression of IRS2 has been suggested to promote tumor metastasis. However, its function in intrahepatic cholangiocarcinoma (iCCA) has not been investigated extensively. The present study examined 86 cases of iCCA to analyze IRS2 expression and its correlation with clinicopathological characteristics using immunohistochemical assays. Three stable cell lines overexpressing IRS2 were established. The mobility potential of cells was compared in the basal condition and following manipulation using cell migration and invasion assays. Epithelial-mesenchymal transition (EMT)-associated proteins were assessed by western blotting. IRS2 was overexpressed in 29 iCCA cases (33.7%) and was significantly more frequent in cases with large tumor size (P=0.033), classified as an advanced stage by the American Joint Committee on Cancer (P=0.046). In comparison with the control cells, the three IRS2-overexpressing iCCA cell lines exhibited a statistically significant increase in mobility potential. Expression analysis of EMT markers demonstrated decreased epithelial marker levels and increased mesenchymal marker levels in IRS2-overexpressing cells compared with their corresponding control cells. The results of the present study indicate that IRS2 overexpression is characterized by a large tumor size and advanced tumor stage in iCCA, and that it may increase tumor mobility potential by regulating EMT pathways. Therefore, it is a valuable predictive indicator of metastasis and may provide a novel direction for targeted therapy in iCCA.

Stimulatory actions of IGF-I are mediated by IGF-IR cross-talk with GPER and DDR1 in mesothelioma and lung cancer cells

Insulin-like growth factor-I (IGF-I)/IGF-I receptor (IGF-IR) system has been largely involved in the pathogenesis and development of various tumors. We have previously demonstrated that IGF-IR cooperates with the G-protein estrogen receptor (GPER) and the collagen receptor discoidin domain 1 (DDR1) that are implicated in cancer progression. Here, we provide novel evidence regarding the molecular mechanisms through which IGF-I/IGF-IR signaling triggers a functional cross-talk with GPER and DDR1 in both mesothelioma and lung cancer cells. In particular, we show that IGF-I activates the transduction network mediated by IGF-IR leading to the up-regulation of GPER and its main target genes CTGF and EGR1 as well as the induction of DDR1 target genes like MATN-2, FBN-1, NOTCH 1 and HES-1. Of note, certain DDR1-mediated effects upon IGF-I stimulation required both IGF-IR and GPER as determined knocking-down the expression of these receptors. The aforementioned findings were nicely recapitulated in important biological outcomes like IGF-I promoted chemotaxis and migration of both mesothelioma and lung cancer cells. Overall, our data suggest that IGF-I/IGF-IR system triggers stimulatory actions through both GPER and DDR1 in aggressive tumors as mesothelioma and lung tumors. Hence, this novel signaling pathway may represent a further target in setting innovative anticancer strategies.

Regulation of microRNA using promising dietary phytochemicals: Possible preventive and treatment option of malignant mesothelioma

Malignant mesothelioma (MM) is a very aggressive, lethal cancer, and its incidence is increasing worldwide. Development of multi-drug resistance, therapy related side-effects, and disease recurrence after therapy are the major problems for the successful treatment of MM. Emerging evidence indicates that dietary phytochemicals can exert anti-cancer activities by regulating microRNA expression. Until now, only one dietary phytochemical (ursolic acid) has been reported to have MM microRNA regulatory ability. A large number of dietary phytochemicals still remain to be tested. In this paper, we have introduced some dietary phytochemicals (curcumin, epigallocatechin gallate, quercetin, genistein, pterostilbene, resveratrol, capsaicin, ellagic acid, benzyl isothiocyanate, phenethyl isothiocyanate, sulforaphane, indole-3-carbinol, 3,3'-diindolylmethane, diallyl disulphide, betulinic acid, and oleanolic acid) which have shown microRNA regulatory activities in various cancers and could regulate MM microRNAs. In addition to microRNA regulatory activities, curcumin, epigallocatechin gallate, quercetin, genistein, resveratrol, phenethyl isothiocyanate, and sulforaphane have anti-mesothelioma potentials, and pterostilbene, capsaicin, ellagic acid, benzyl isothiocyanate, indole-3-carbinol, 3,3'-diindolylmethane, diallyl disulphide, betulinic acid, and oleanolic acid have potentials to inhibit cancer by regulating the expression of various genes which are also known to be aberrant in MM.

Targeting eukaryotic protein translation in mesothelioma

The default mechanism for protein translation in eukaryotes involves activation of the eIF4 complex at the 5' end of mRNA. This activity is upregulated in cancers, resulting in the expression of a variety of proteins necessary for the development and maintenance of the neoplastic state. Not surprisingly, mesothelioma demonstrates this same reliance on activation of 5' cap mediated translation. Efforts are ongoing to target and exploit our knowledge of this key molecular switch for cancer therapy. Agents targeting the critical eIF4E cap binding protein, disruption of the eIF4 complex, and exploitation for oncolytic virotherapy are some of the important areas of current research in mesothelioma protein translational research.

PI3 Kinase Pathway and MET Inhibition is Efficacious in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive cancer that is commonly associated with prior asbestos exposure. Receptor tyrosine kinases (RTKs) such as MET and its downstream target PI3K are overexpressed and activated in a majority of MPMs. Here, we studied the combinatorial therapeutic efficacy of the MET/ALK inhibitor crizotinib, with either a pan-class I PI3K inhibitor, BKM120, or with a PI3K/mTOR dual inhibitor, GDC-0980, in mesothelioma. Cell viability results showed that MPM cells were highly sensitive to crizotinib, BKM120 and GDC-0980 when used individually and their combination was more effective in suppressing growth. Treatment of MPM cells with these inhibitors also significantly decreased cell migration, and the combination of them was synergistic. Treatment with BKM120 alone or in combination with crizotinib induced G2-M arrest and apoptosis. Both crizotinib and BKM120 strongly inhibited the activity of MET and PI3K as evidenced by the decreased phosphorylation of MET, AKT and ribosomal S6 kinase. Using a PDX mouse model, we showed that a combination of crizotinib with BKM120 was highly synergetic in inhibiting MPM tumor growth. In conclusion our findings suggest that dual inhibition of PI3K and MET pathway is an effective strategy in treating MPM as compared to a single agent.

New therapeutic strategies for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and aggressive malignant disease affecting the mesothelium, commonly associated to asbestos exposure. Therapeutic actions are limited due to the late stage at which most patients are diagnosed and the intrinsic chemo-resistance of the tumor. The recommended systemic therapy for MPM is cisplatin/pemetrexed regimen with a mean overall survival of about 12months and a median progression free survival of less than 6months. Considering that the incidence of this tumor is expected to increase in the next decade and that its prognosis is poor, novel therapeutic approaches are urgently needed. For some tumors, such as lung cancer and breast cancer, druggable oncogenic alterations have been identified and targeted therapy is an important option for these patients. For MPM, clinical guidelines do not recommend biological targeted therapy, mainly because of poor target definition or inappropriate trial design. Further studies are required for a full comprehension of the molecular pathogenesis of MPM and for the development of new target agents. This review updates pre-clinical and clinical data on the efficacy of targeted therapy and immune checkpoint inhibition in the treatment of mesothelioma. Finally, future perspectives in this deadly disease are also discussed.

Analysis of expression of PTEN/PI3K pathway and programmed cell death ligand 1 (PD-L1) in malignant pleural mesothelioma (MPM)

BACKGROUND

Malignant pleural mesothelioma (MPM) frequently express elevated AKT/mTOR activity. Previous reports in gliomas, colon, breast and prostate cancer suggest that PTEN/PI3K pathway may be important for the induction of PD-L1 expression. This study explored the expression of PTEN/PI3K pathway and PD-L1 in MPM and its relationship with the patient́s prognosis

MATERIAL AND METHODS

Twenty seven consecutive MPM patients were reviewed. Formalin-fixed, paraffin-embedded tissue biopsies were used for immunohistochemical analysis of PTEN/PI3K pathway and PD-L1 RESULTS: Expression of PTEN, mTOR, pAKT, p4EBP1, peif4E, pS6 and FOXO3a was found in 88.5%, 92.3%, 78.3%, 38.5%, 100%, 52.2% and 100% of tumors and PD-L1 in 23%. We found a significant correlation between pAKT, FOXO3a and PD-L1 expression and longer overall survival (p <0.05). We did not identify significant association between the level of PD-L1 expression and alterations in PI3K pathway

CONCLUSIONS

This study shows PTEN/PI3K pathway and PD-L1 in MPM are frequently activated. Our results suggests that there is not association between PD-L1 and the involvement of the PI3K pathway in MPM.

Preclinical Effectiveness of Selective Inhibitor of IRS-1/2 NT157 in Osteosarcoma Cell Lines

Osteosarcoma (OS) is the most common primary bone tumor in children and young adults. Several studies have confirmed the involvement of the insulin-like growth factor (IGF) system in the regulation of OS cell proliferation and differentiation as well as in the protection of cells from chemotherapy. Insulin receptor substrate (IRS)-1 is a critical mediator of IGF-1R signaling, and we recently reported that its overexpression in OS cells increases proliferation, migration, and metastasis both in vitro and in vivo. In this study, we evaluated the efficacy of NT157, a selective inhibitor of IRS-1/2, in a panel of OS cells. A strong dose-dependent inhibition of growth was observed in the MG-63, OS-19, and U-2OS OS cell lines, displaying IC50 values at sub-micromolar doses after 72 h of treatment. Exposure to NT157 elicited dose- and time-dependent decreases in IRS-1 levels. Moreover, a protein analysis showed that the degradation of IRS-1 inhibited the activation of principal downstream mediators of the IGF pathway. NT157 significantly affected the cells' migratory ability, as confirmed by a wound-healing assay. The inhibitor induced cytostatic effects, as evidenced by G2/M cell cycle arrest, and did not affect apoptosis. Consequently, NT157 was combined with drugs used to treat OS in order to capitalize on its therapeutic potential. Simultaneous treatments were made in association with chemotherapeutic agents in a fixed ratio for 72 h and cell proliferation was determined by MTT assay. Synergistic or addictive effects with respect to single agents are expressed as the combination index. Significant synergistic effects were obtained with several targeted drugs, such as Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, and NVP-BEZ235, a dual inhibitor of PI-3K/mTOR. Overall, these findings provide evidence for the effectiveness of a selected inhibitor of IRS-1/2 NT157 in OS cells, displaying a promising approach based on the targeting of IRS-1 combined with other therapies for the treatment of this pediatric solid tumor.

MET and PI3K/mTOR as a potential combinatorial therapeutic target in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive disease with a poor prognosis. Studies have shown that both MET and its key downstream intracellular signaling partners, PI3K and mTOR, are overexpressed in MPM. Here we determined the combinatorial therapeutic efficacy of a new generation small molecule inhibitor of MET, ARQ 197, and dual PI3K/mTOR inhibitors NVP-BEZ235 and GDC-0980 in mesothelioma cell and mouse xenograft models. Cell viability results show that mesothelioma cell lines were sensitive to ARQ 197, NVP-BEZ235 and GDC-0980 inhibitors. The combined use of ARQ 197 with either NVP-BEZ235 or GDC-0980, was synergistic (CI<1). Significant delay in wound healing was observed with ARQ 197 (p<0.001) with no added advantage of combining it with either NVP-BEZ235 or GDC-0980. ARQ 197 alone mainly induced apoptosis (20±2.36%) that was preceded by suppression of MAPK activity, while all the three suppressed cell cycle progression. Both GDC-0980 and NVP-BEZ235 strongly inhibited activities of PI3K and mTOR as evidenced from the phosphorylation status of AKT and S6 kinase. The above observation was further substantiated by the finding that a majority of the MPM archival samples tested revealed highly active AKT. While the single use of ARQ 197 and GDC-0980 inhibited significantly the growth of MPM xenografts (p<0.05, p<0.001 respectively) in mice, the combination of the above two drugs was highly synergistic (p<0.001). Our results suggest that the combined use of ARQ 197/NVP-BEZ235 and ARQ 197/GDC-0980 is far more effective than the use of the drugs singly in suppressing MPM tumor growth and motility and therefore merit further translational studies.

Identification of pregnancy-associated plasma protein A as a migration-promoting gene in malignant pleural mesothelioma cells: a potential therapeutic target

Despite recent advances in treatment, malignant pleural mesothelioma (MPM) remains a deadly disease. Targeted therapy generated broad interests and is highly expected for the treatment of MPM, yet promising preclinical results have not been translated into substantial clinical benefits for the patients. In this study, we tried to identify the genes which play functional roles in cell migration as well as to test whether they can be used as novel targets for molecular targeted therapy for MPM in preclinical model. In our study, pregnancy-associated plasma protein A (PAPPA) was identified as a gene whose expression level is correlated with MPM cell migration by correlation analysis combining MPM cell migration ability and their gene expression profiles. Highly migratory cells were selected from MPM cell lines, MSTO-211H, NCI-H290 and EHMES-1 in vitro and up-regulation of PAPPA in these cells were confirmed. In vitro, PAPPA was demonstrated to stimulate the MPM cell migration via cleavage of insulin-like growth factor-binding protein-4 and subsequent release of IGF-1. Gene silencing of PAPPA in MPM cells led to reduced migration, invasion and proliferation. Furthermore, PAPPA shRNA transfected NCI-H290 when orthotopically inoculated into pleural cavity of severe combined immunodeficiency recipient mice, failed to develop tumors and produce bloody pleural effusion as control shRNA transfected cells did. Our study suggests that PAPPA plays a functional role in promoting MPM cell migration and it might serve as a potential therapeutic target for the treatment of MPM.

Investigation of insulin resistance gene polymorphisms in patients with differentiated thyroid cancer

We aimed to investigate insulin receptor substrate-1 (IRS-1), insulin receptor substrate-2 (IRS-2), insulin-like growth factor binding protein-3 (IGFBP-3) genotypes, which are thought to be involved in the pathogenesis of many solid tumors and have thus far not been studied in patients with differentiated thyroid cancer (DTC). The study consisted of 93 patients diagnosed with DTC (79 females, 14 males) and 111 healthy control subjects (63 females, 48 males). The anthropometric measurements, lipid profiles, thyroid function tests and homeostatic model assessment (HOMA) as an indicator of insulin resistance (IR) of all patients were recorded. In addition IRS-1, IRS-2 and IGFBP-3 gene polymorphisms were determined by using polymerase chain reaction and restriction fragment length polymorphism. Hardy-Weinberg equilibrium was tested for each gene polymorphisms, and genetic effects were evaluated by the Chi Square test and multiple logistic regression. Homeostasis model assessment of insulin resistance (HOMA-IR), body mass index, waist circumference and serum total cholesterol levels were significantly higher in patients with DTC than in the control group. There was no difference between the two groups with respect to IRS-1, IRS-2 and IGFBP-3 gene polymorphisms. In addition, these gene polymorphisms were found to have no effect on lymph node metastases or tumor staging. While, obesity and increased HOMA-IR may be risk factors in DTC development, we suggest that IRS-1, IRS-2 and IGFBP-3 gene polymorphisms do not play an important role in pathogenesis of DTC.

The role of key genes and pathways involved in the tumorigenesis of Malignant Mesothelioma

Malignant Mesothelioma (MM) is a very aggressive cancer with low survival rates and often diagnosed at an advanced stage. Several players have been implicated in the development of this cancer, such as asbestos, erionite and the simian virus 40 (SV40). Here, we have reviewed the involvement of erionite, SV40, as well as, the role of several genes (p16(INK4a), p14(ARF), NF2, LATS2, SAV, CTNNB1 and among others), the pathways (RAS, PI3K, Wnt, BCL and Hippo), and their respective roles in the development of MM.

miR-1 induces growth arrest and apoptosis in malignant mesothelioma

BACKGROUND

We investigated microRNA expression profiles of malignant pleural mesothelioma (MPM) specimens to identify novel microRNA that are potentially involved in the oncogenic transformation of human pleural cells.

METHODS

microRNA microarray transcriptional profiling studies of 25 MPM primary tumors were performed. We used normal pleural tissue from an unmatched patient cohort as normal comparators. To confirm microarray data, we used real-time quantitative polymerase chain reaction. Representative cell lines H513 and H2052 were used in functional analyses of miR-1.

RESULTS

In addition to several novel MPM-associated microRNAs, we observed that the expression level of miR-1 was significantly lower in tumors as compared with normal pleural specimens. Subsequently, pre-miR of miR-1 was introduced into MPM cell lines to overexpress this microRNA. Phenotypic changes of these altered cells were assayed. The cellular proliferation rate was significantly inhibited after overexpression of miR-1. Early and late apoptosis was increased markedly in miR-1-transfected cell lines. Taken together, these data suggested that overexpression of miR-1 induced apoptosis in these MPM cell lines, acting as a tumor suppressor. We confirmed our observations by assessing in the transduced MPM cells cell cycle-related, proapoptotic, and antiapoptotic genes, which all showed coordinated, significant changes characteristic of the apoptotic phenotype.

CONCLUSIONS

Further investigation and validation of our microRNA database of MPM may elucidate previously unrecognized molecular pathways and/or mechanisms by identifying novel microRNAs that are involved in malignant transformation. Our study has now found miR-1 to be one of these MPM-associated microRNAs, with potential pathogenic and therapeutic significance.

Therapeutic destruction of insulin receptor substrates for cancer treatment

Insulin receptor substrates 1 and 2 (IRS1/2) mediate mitogenic and antiapoptotic signaling from insulin-like growth factor 1 receptor (IGF-IR), insulin receptor (IR), and other oncoproteins. IRS1 plays a central role in cancer cell proliferation, its expression is increased in many human malignancies, and its upregulation mediates resistance to anticancer drugs. IRS2 is associated with cancer cell motility and metastasis. Currently, there are no anticancer agents that target IRS1/2. We present new IGF-IR/IRS-targeted agents (NT compounds) that promote inhibitory Ser-phosphorylation and degradation of IRS1 and IRS2. Elimination of IRS1/2 results in long-term inhibition of IRS1/2-mediated signaling. The therapeutic significance of this inhibition in cancer cells was shown while unraveling a novel mechanism of resistance to B-RAF(V600E/K) inhibitors. We found that IRS1 is upregulated in PLX4032-resistant melanoma cells and in cell lines derived from patients whose tumors developed PLX4032 resistance. In both settings, NT compounds led to the elimination of IRS proteins and evoked cell death. Treatment with NT compounds in vivo significantly inhibited the growth of PLX4032-resistant tumors and displayed potent antitumor effects in ovarian and prostate cancers. Our findings offer preclinical proof-of-concept for IRS1/2 inhibitors as cancer therapeutics including PLX4032-resistant melanoma. By the elimination of IRS proteins, such agents should prevent acquisition of resistance to mutated-B-RAF inhibitors and possibly restore drug sensitivity in resistant tumors.

Aflatoxin B1 up-regulates insulin receptor substrate 2 and stimulates hepatoma cell migration

Aflatoxin B1 (AFB1) is a potent carcinogen that can induce hepatocellular carcinoma. AFB1-8,9-exo-epoxide, one of AFB1 metabolites, acts as a mutagen to react with DNA and induce gene mutations, including the tumor suppressor p53. In addition, AFB1 reportedly stimulates IGF receptor activation. Aberrant activation of IGF-I receptor (IGF-IR) signaling is tightly associated with various types of human tumors. In the current study, we investigated the effects of AFB1 on key elements in IGF-IR signaling pathway, and the effects of AFB1 on hepatoma cell migration. The results demonstrated that AFB1 induced IGF-IR, Akt, and Erk1/2 phosphorylation in hepatoma cell lines HepG2 and SMMC-7721, and an immortalized human liver cell line Chang liver. AFB1 also down-regulated insulin receptor substrate (IRS) 1 but paradoxically up-regulated IRS2 through preventing proteasomal degradation. Treatment of hepatoma cells and Chang liver cells with IGF-IR inhibitor abrogated AFB1-induced Akt and Erk1/2 phosphorylation. In addition, IRS2 knockdown suppressed AFB1-induced Akt and Erk1/2 phosphorylation. Finally, AFB1 stimulated hepatoma cell migration. IGF-IR inhibitor or IRS2 knockdown suppressed AFB1-induced hepatoma cell migration. These data demonstrate that AFB1 stimulates hepatoma cell migration through IGF-IR/IRS2 axis.

Inhibition of phosphoinositide-3 kinase pathway down regulates ABCG2 function and sensitizes malignant pleural mesothelioma to chemotherapy

Malignant pleural mesothelioma (MPM) is a relatively chemoresistant malignancy. Diverse biological targets are under investigation to develop new therapeutic options. One of these targets, namely the phosphoinositide-3-kinase (PI3K) pathway, has been shown to be a regulator of the side population (SP) phenotype in different cancers. The SP phenotype is due to drug efflux abilities providing drug-resistant properties. The presence of a SP fraction in MPM was recently observed in our laboratory. The aim of this study was to investigate the role of the PI3K pathway in the regulation of the SP phenotype in MPM. Treatment of overnight serum-starved cells with IGF increased phosphorylation of downstream target AKT, S6 and 4EBP1 and SP fraction in ZL55, ZL34 and SDM103T2 MPM cell lines. The PI3K/mTOR inhibitor NVP-BEZ235 and PI3K inhibitor wortmannin reduced the phosphorylation of downstream target AKT, S6 and 4EBP1 and decreased the SP fraction. Chemotherapy resistance mediated by drug efflux was tested by treating the cells with mitoxantrone. NVP-BEZ235 increased mitoxantrone cytotoxicity and this effect was mimicked by fumitremorgin C, a specific ABCG2 inhibitor, although not to the same extent, indicating that ABCG2-mediated drug efflux participates to chemoresistance. The involvement of ABCG2 in drug efflux was confirmed by determination of ABCG2-mediated decrease of intracellular mitoxantrone accumulation and silencing experiments. NVP-BEZ235-mediated decrease in drug efflux was associated with a significant decrease of ABCG2 present at the cell surface in ZL55 and SDM103T2 cells. In conclusion, the PI3K pathway is playing an important role in regulating the SP phenotype in MPM cells and inhibition of this activity may contribute to a more efficient cancer treatment.

MEMO1, a new IRS1-interacting protein, induces epithelial-mesenchymal transition in mammary epithelial cells

MEMO1 (mediator of ErbB2-driven cell motility 1) regulates HER2-dependent cell migration. Increased MEMO1 expression is associated with cancer aggressiveness. Here, we found that MEMO1 is also involved in breast carcinogenesis via regulating insulin-like growth factor-I receptor-dependent signaling events. We showed that MEMO1 binds to insulin receptor substrate 1, activates the downstream PI3K/Akt signaling pathway, leads to upregulation of Snail1 and thereby triggers the epithelial-mesenchymal transition (EMT) program. In addition, MEMO1 overexpression is accompanied by growth factor-independent proliferation, anchorage-independent growth in soft agar, and enhanced metastatic potential. Together, these findings suggest that MEMO1 acts as an oncogene and is a potential therapeutic target for cancer treatment.

Molecular changes in mesothelioma with an impact on prognosis and treatment

CONTEXT

In recent decades, research on malignant pleural mesothelioma (MPM) has been developed to improve patients' outcomes by increasing the level of confidence in MPM diagnosis and prognosis.

OBJECTIVE

To summarize data on genetic and epigenetic abnormalities in MPM that may be of interest for a better management of patients with MPM.

DATA SOURCES

Data were obtained from scientific publications on genetic and epigenetic abnormalities in MPM by studying gene mutations, DNA methylation, and gene and microRNA expression profiling.

CONCLUSIONS

Molecular changes in MPM consist in altered expression and in activation or inactivation of critical genes in oncogenesis, especially tumor suppressor genes at the INK4 and NF2 loci. Activation of membrane receptor tyrosine kinases and deregulation of signaling pathways related to differentiation, survival, proliferation, apoptosis, cell cycle control, metabolism, migration, and invasion have been demonstrated. Alterations that could be targeted at a global level (methylation) have been recently reported. Experimental research has succeeded especially in abolishing proliferation and triggering apoptosis in MPM cells. So far, targeted clinical approaches focusing on receptor tyrosine kinases have had limited success. Molecular analyses of series of MPM cases have shown that defined alterations are present in MPM subsets, consistent with interindividual variations of molecular alterations, and suggesting that identification of patient subgroups will be essential to develop more specific therapies.

Preclinical studies identify novel targeted pharmacological strategies for treatment of human malignant pleural mesothelioma

The incidence of human malignant pleural mesothelioma (hMPM) is still increasing worldwide. hMPM prognosis is poor even if the median survival time has been slightly improved after the introduction of the up-to-date chemotherapy. Nevertheless, large phase II/III trials support the combination of platinum derivatives and pemetrexed or raltitrexed, as preferred first-line schedule. Better understanding of the molecular machinery of hMPM will lead to the design and synthesis of novel compounds targeted against pathways identified as crucial for hMPM cell proliferation and spreading. Among them, several receptors tyrosine kinase show altered activity in subsets of hMPM. This observation suggests that these kinases might represent novel therapeutic targets in this chemotherapy-resistant disease. Over these foundations, several promising studies are ongoing at preclinical level and novel molecules are currently under evaluation as well. Yet, established tumour cell lines, used for decades to investigate the efficacy of anticancer agents, although still the main source of drug efficacy studies, after long-term cultures tend to biologically diverge from the original tumour, limiting the predictive potential of in vivo efficacy. Cancer stem cells (CSCs), a subpopulation of malignant cells capable of self-renewal and multilineage differentiation, are believed to play an essential role in cancer initiation, growth, metastasization and relapse, being responsible of chemo- and radiotherapy refractoriness. According to the current carcinogenesis theory, CSCs represent the tumour-initiating cell (TIC) fraction, the only clonogenic subpopulation able to originate a tumour mass. Consequently, the recently described isolation of TICs from hMPM, the proposed main pharmacological target for novel antitumoural drugs, may contribute to better dissect the biology and multidrug resistance pathways controlling hMPM growth.

Efficacy of anti-insulin-like growth factor I receptor monoclonal antibody cixutumumab in mesothelioma is highly correlated with insulin growth factor-I receptor sites/cell

Insulin growth factor-I receptor (IGF-IR) is expressed in mesothelioma and therefore an attractive target for therapy. The antitumor activity of cixutumumab, a humanized monoclonal antibody to IGF-IR, in mesothelioma and relationship to IGF-IR expression was investigated using eight early passage tumor cells obtained from patients, nine established cell lines and an in vivo human mesothelioma tumor xenograft model. Although IGF-IR expression at the mRNA and protein level was present in all mesothelioma cells, using a quantitative ELISA immunoassay, there was considerable variability of IGF-IR expression ranging from 1 to 14 ng/mg of lysate. Using flow cytometry, the number of IGF-IR surface receptors varied from ≈ 2,000 to 50,000 sites/cell. Cells expressing >10,000 sites/cell had greater than 10% growth inhibition when treated with cixutumumab (100 μg/ml). Cixutumumab also induced antibody-dependent cell-mediated toxicity (>10% specific lysis) in cell lines, which had >20,000 IGF-IR sites/cell. Treatment with cixutumumab decreased phosphorylation of IGF-IR, Akt and Erk in cell lines, H226 and H28 having 24,000 and 51,000 IGF-IR sites/cell, respectively, but not in the cell line H2052 with 3,000 IGF-IR sites/cell. In vivo, cixutumumab treatment delayed growth of H226 mesothelioma tumor xenografts in mice and improved the overall survival of these mice compared to mice treated with saline (p < 0.004). Our results demonstrate that the antitumor efficacy of cixutumumab including inhibition of IGF-IR downstream signaling is highly correlated with IGF-IR sites/cell. A phase II clinical trial of cixutumumab is currently ongoing for the treatment of patients with mesothelioma.

Exploratory analysis of activation of PTEN-PI3K pathway and downstream proteins in malignant pleural mesothelioma (MPM)

BACKGROUND

Malignant pleural mesothelioma (MPM) is a highly aggressive neoplasm with elevated AKT/mTOR activity. We aimed to identify the expression and phosphorylation status of PTEN, PI3K and downstream signaling in MPM.

PATIENTS AND METHODS

Thirty consecutive MPM patients were identified. Clinical data analyzed: sex, age, histology, performance status (PS), white blood count, and neutrophil-lymphocyte ratio (NLR). Paraffin-embedded biopsies were used for immunohistochemical analysis.

RESULTS

Overexpression of PTEN, pMAPK, mTOR, pAKT, 4E-BP1, p4E-BP1, eIF-4E, peIF-4E, p-S6 and FOXO3a in MPM was found in 90%, 100%, 93.3%, 80%, 100%, 43.3%, 96.7%, 100%, 63.3% and 100% of tumors respectively. There was a significant correlation between low pS6 protein expression and longer progression free survival (PFS: 7.9 vs 5.6 months; p = 0.04) and overall survival (OS: 23.4 vs 5.6 months; p = 0.05). Patients with concomitant low expression of pS6 and p4E-BP1 and overexpression of FOXO3a had significantly better prognosis (34.6 vs 1.9 months; p = 0.004). In multivariate analysis, histology and NLR were independent prognostic factors (p = 0.02 and p = 0.04 respectively), but pS6 only showed a trend (p = 0.8).

CONCLUSIONS

This study shows PI3K pathway and downstream proteins in MPM are frequently activated and provides prognostic information. The role of PI3K pathway is worth of prospective validation in future studies on MPM.

Insulin receptor substrates form high-molecular-mass complexes that modulate their availability to insulin/insulin-like growth factor-I receptor tyrosine kinases

Insulin receptor substrates (IRSs) are phosphorylated by activated insulin/insulin-like growth factor (IGF)-I receptor tyrosine kinases. Phosphotyrosyl IRSs are recognized by signaling molecules possessing src homology region 2 (SH2) domains, which mediate various insulin/IGF bioactivities. However, we have shown that IRSs are also associated with other proteins by a phosphotyrosine-independent mechanism. Here, we demonstrated that IRSs form high-molecular-mass complexes (we named these complexes IRSomes) with various proteins and we elucidated their possible roles. Blue native-polyacrylamide gel electrophoresis of cell lysates revealed IRSome formation. Some proteins associated with IRSs in IRS-isoform-, cell-type-, or stimulus-specific manners. Results of the in vitro tyrosine phosphorylation assay indicated that tyrosine phosphorylation of IRS-1 by insulin receptor was decreased when IRS-1 was contained in IRSomes prepared from 3T3-L1 adipocytes treated with TNF-α. Also, tyrosine phosphorylation of IRS-2 by IGF-I receptor was increased when IRS-2 was contained in IRSomes prepared from FRTL-5 thyrocytes treated with dibutyryl cAMP. These results demonstrated that cytokine/hormone-induced formation of IRSomes modulates availability of IRSs to receptor tyrosine kinases.

Association of G1057D variant of insulin receptor substrate-2 with endometriosis

OBJECTIVE

To investigate whether the insulin receptor substrate (IRS)-2 G1057D polymorphism is associated with the risk of endometriosis, and to evaluate potential correlation of IRS2 gene polymorphism with the stages of endometriosis.

DESIGN

Case-control study.

SETTING

Gynecology clinics in university hospital.

PATIENT(S)

Women with (n = 135) or without (n = 135) endometriosis. Afterward, the women with endometriosis were divided into two groups according to the stage: group 1 included 63 women in stages I-II, and group 2 included 72 women in stages III-IV.

INTERVENTION(S)

Genotyping by polymerase chain reaction-based restriction fragment-length polymorphism method.

MAIN OUTCOME MEASURE(S)

Genotype distribution of the G1057D polymorphism in the IRS2 gene.

RESULT(S)

The genotype distribution of the IRS2 G1057D polymorphism in the endometriosis group was significantly different from that of the control group (GG/GD/DD rates were 43.0%/39.3%/17.7% and 55.6%/36.3%/8.1% for the endometriosis and control groups, respectively). Further subgroup analyses according to the stage of endometriosis also revealed a positive association between the IRS2 DD genotype expression and stage III-IV endometriosis patients in the population studied.

CONCLUSION(S)

These results suggest that the IRS2 G1057D polymorphism may be associated with an increased risk for endometriosis.

Activated 4E-BP1 represses tumourigenesis and IGF-I-mediated activation of the eIF4F complex in mesothelioma

BACKGROUND

Insulin-like growth factor (IGF)-I signalling stimulates proliferation, survival, and invasion in malignant mesothelioma and other tumour types. Studies have found that tumourigenesis is linked to dysregulation of cap-dependent protein translation.

METHODS

The effect of IGF stimulation on cap-mediated translation activation in mesothelioma cell lines was studied using binding assays to a synthetic 7-methyl GTP-cap analogue. In addition, cap-mediated translation was genetically repressed in these cells with a dominant active motive of 4E-BP1.

RESULTS

In most mesothelioma cell lines, IGF-I stimulation resulted in a hyperphosphorylation-mediated inactivation of 4E-BP1 compared with that in normal mesothelial cells. An inhibitor of Akt diminished IGF-I-mediated phosphorylation of 4E-BP1, whereas inhibiting MAPK signalling had no such effect. IGF-I stimulation resulted in the activation of the cap-mediated translation complex as indicated by an increased eIF4G/eIF4E ratio in cap-affinity assays. Akt inhibition reversed the eIF4G/eIF4E ratio. Mesothelioma cells transfected with an activated 4E-BP1 protein (4E-BP1(A37/A46)) were resistant to IGF-I-mediated growth, motility, and colony formation. In a murine xenograft model, mesothelioma cells expressing the dominant active 4E-BP1(A37/A46) repressor protein showed abrogated tumourigenicity compared with control tumours.

CONCLUSION

IGF-I signalling in mesothelioma cells drives cell proliferation, motility, and tumourigenesis through its ability to activate cap-mediated protein translation complex through PI3K/Akt/mTOR signalling.

Expression and function of the insulin receptor substrate proteins in cancer

The Insulin Receptor Substrate (IRS) proteins are cytoplasmic adaptor proteins that function as essential signaling intermediates downstream of activated cell surface receptors, many of which have been implicated in cancer. The IRS proteins do not contain any intrinsic kinase activity, but rather serve as scaffolds to organize signaling complexes and initiate intracellular signaling pathways. As common intermediates of multiple receptors that can influence tumor progression, the IRS proteins are positioned to play a pivotal role in regulating the response of tumor cells to many different microenvironmental stimuli. Limited studies on IRS expression in human tumors and studies on IRS function in human tumor cell lines and in mouse models have provided clues to the potential function of these adaptor proteins in human cancer. A general theme arises from these studies; IRS-1 and IRS-4 are most often associated with tumor growth and proliferation and IRS-2 is most often associated with tumor motility and invasion. In this review, we discuss the mechanisms by which IRS expression and function are regulated and how the IRS proteins contribute to tumor initiation and progression.

Inhibition of the insulin-like growth factor 1 receptor pathway enhances the antitumor effect of cisplatin in human malignant mesothelioma cell lines

Human malignant mesothelioma (HMM) is a fatal tumor and is poorly responsive to current therapeutic regimens. The insulin-like growth factor 1 receptor (IGF-1R) pathway is activated in HMM cell lines and tissues. Treatment with AG1024, an inhibitor of the IGF-1R pathway, significantly decreased cell proliferation and attenuated the phosphorylation of Akt and p44/42. In addition, it significantly enhanced the cytotoxic effects of cisplatin in HMM cell lines. This study supports the conjecture that inhibition of the IGF-1R pathway may be a useful target for reducing toxicity and alleviating chemoresistance to traditional anticancer drugs in HMM patients.

New diagnostic and molecular characteristics of malignant mesothelioma

Malignant mesothelioma is a primary cancer of the serosal cavities, an anatomic site that is also frequently affected by metastatic disease, predominantly from primary carcinomas of the lung, breast, and ovary. Advances in immunohistochemistry have resulted in improved diagnostic sensitivity and specificity in the differential diagnosis between metastatic adenocarcinoma and malignant mesothelioma in both cytological and histological material. Recently, the author's group applied high throughput technology to the identification of new markers that may aid in differentiating malignant mesothelioma from ovarian and peritoneal serous carcinoma, tumors with closely related histogenesis and antigenic profile. In addition to the improved tools available for serosal cancer diagnosis, knowledge regarding the biology of malignant mesothelioma has been accumulating in recent years. This review presents current data regarding the diagnostic and biological aspects of malignant mesothelioma.

Transcriptional regulation of IRS5/DOK4 expression in non-small-cell lung cancer cells

The insulin-receptor substrate family plays important roles in cellular growth, signaling, and survival. Two new members of this family have recently been isolated: IRS5/Dok4 and IRS6/Dok5. This study examines the expression of IRS5/DOK4 in a panel of lung cancer cell lines and tumor specimens. The results demonstrate that expression of IRS5/DOK4 is frequently altered with both elevated and decreased expression in non-small-cell lung cancer (NSCLC) tumor specimens. The altered expression of IRS5/DOK4 observed in tumor samples is not due to aberrant methylation. In vitro cell culture studies demonstrate that treatment of NSCLC cell lines with the histone deacetylase inhibitor trichostatin A (TSA) upregulates IRS5/DOK4. This finding indicates that expression is regulated epigenetically at the level of chromatin remodeling. Chromatin immunoprecipitation experiments confirm that the IRS5/DOK4 promoter has enhanced histone hyperacetylation following treatments with TSA. Finally, hypoxia was demonstrated to downregulate IRS5/DOK4 expression. This expression was restored by TSA. The clinical relevance of altered IRS5/DOK4 expression in NSCLC requires further evaluation.

Insulin-like growth factor-I receptor blockade improves outcome in mouse model of lung injury

RATIONALE

The insulin-like growth factor-I (IGF-I) pathway is an important determinant of survival and proliferation in many cells. However, little is known about the role of the IGF-I pathway in lung injury. We previously showed elevated levels of IGF-I in bronchoalveolar lavage fluid from patients with acute respiratory distress syndrome. Furthermore, immunodepletion of IGF from acute respiratory distress syndrome bronchoalveolar lavage increased fibroblast apoptosis.

OBJECTIVES

We examined the effect of blockade of type 1 IGF tyrosine kinase receptor (IGF-IR) in a murine model of bleomycin-induced lung injury and fibrosis.

METHODS

Mice were treated with a monoclonal antibody against the IGF-I receptor (A12) or vehicle after intratracheal bleomycin instillation.

MEASUREMENTS AND MAIN RESULTS

Mice treated with A12 antibody had significantly improved survival after bleomycin injury compared with control mice. Both groups of mice had a similar degree of fibrosis on days 7 and 14, but by Day 28 the A12-treated group had significantly less fibrosis. Delayed treatment with A12 also resulted in decreased fibrosis. A12-treated mice had significantly decreased apoptotic cells on Day 28 compared with control mice. We confirmed that A12 treatment induced mouse lung fibroblast apoptosis in vitro. In addition, IGF-I increased lung fibroblast migration. The primary pathway activated by IGF-I in lung fibroblasts was the insulin receptor substrate-2/phosphatidylinositol 3-kinase/Akt axis.

CONCLUSIONS

IGF-I regulated survival and migration of fibrogenic cells in the lung. Blockade of the IGF pathway increased fibroblast apoptosis and subsequent resolution of pulmonary fibrosis. Thus, IGF-IR may be a potential target for treatment of lung injury and fibrosis.

Progesterone receptor-B regulation of insulin-like growth factor-stimulated cell migration in breast cancer cells via insulin receptor substrate-2

Progesterone action contributes to the signaling of many growth factor pathways relevant to breast cancer tumor biology, including the insulin-like growth factor (IGF) system. Previous work has shown that insulin receptor substrate-2 (IRS-2) but not IRS-1 levels were regulated by progestin in progesterone receptor-B (PR-B) isoform expressing MCF-7 cells (C4-12 PR-B). Furthermore, type 1 IGF receptor (IGF1R) signaling via IRS-2 correlated with the increased cell migration observed in a number of breast cancer cell lines. Consequently, in this study, we examined whether the elevation of IRS-2 protein induced by progestin was sufficient to promote IGF-I-stimulated cell motility. Treatment of C4-12 PR-B cells with progestin shifted the balance of phosphorylation from IRS-1 to IRS-2 in response to IGF-I. This shift in IRS-2 activation was associated with enhanced migration in C4-12 PR-B cells pretreated with progestin, but had no effect on cell proliferation or survival. Treatment of C4-12 PR-B cells with RU486, an antiprogestin, inhibited IGF-induced cell migration. Attenuation of IRS-2 expression using small interfering RNA resulted in decreased IGF-stimulated motility. In addition, IRS-2 knockdown resulted in an abrogation of PKB/Akt phosphorylation but not mitogen-activated protein kinase. Consequently, LY294002, a phosphoinositide-3-kinase inhibitor, abolished IGF-induced cell motility in progestin-treated C4-12 PR-B cells. These data show a role for the PR in functionally promoting growth factor signaling, showing that levels of IRS proteins can determine IGF-mediated biology, PR-B signaling regulates IRS-2 expression, and that IRS-2 can mediate IGF-induced cell migration via phosphoinositide-3-kinase in breast cancer cells.

Protein kinase C beta in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a disease with few therapeutic options. Protein kinase C beta (PKCbeta) is involved in important cellular functions. Enzastaurin (LY317615.HCl) is a novel inhibitor of PKC in clinical development. MPM cell lines (7) and patient tumor tissues (24) were evaluated for expression of PKCbeta by immunoblotting and immunohistochemistry, respectively. In-vitro cell growth assays were performed with enzastaurin with or without cisplatin. Cell migration was evaluated with the wound healing assay. Downstream signaling (survival and focal adhesion pathways) was studied by immunoblotting for related molecules in the presence of phorbol ester with or without enzastaurin. Expression for PKCbeta1 was seen in all cases, with a mean integrated optical density of 152.5 (standard deviation=95.47, n=24), whereas PKCbeta2 expression was less intense, with a mean integrated optical density of 11.45 (standard deviation=16.27, n=21). There was a trend toward lower overall survival among patients expressing above-median PKCbeta1 (P=0.064), but not PKCbeta2. Robust expression of PKCbeta1 and low expression of PKCbeta2 were observed in MPM cell lines. Treatment of MPM cell lines with enzastaurin revealed an IC50 of 5 micromol/l, and strong synergism was observed when combined with cisplatin. Wound healing assay revealed that treatment of H2461 cells with enzastaurin reduced migration by 59.2%. Enzastaurin treatment led to disruption of F-actin architecture. Downstream signaling showed reduced phosphorylation of AKT, FAK (focal adhesion kinase), p130Cas, S6 ribosomal protein, and paxillin. PKCbeta1 was expressed in the majority of MPM samples. Enzastaurin has preclinical activity against MPM, and exhibited synergism with cisplatin. PKCbeta inhibition in MPM might be able to reduce the invasiveness of MPM by affecting cytoskeletal function.

Advances in the systemic therapy of malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive thoracic malignancy associated with exposure to asbestos, and its incidence is anticipated to increase during the first half of this century. Chemotherapy is the mainstay of treatment, yet sufficiently robust evidence to substantiate the current standard of care has emerged only in the past 5 years. This Review summarizes the evidence supporting the clinical activity of chemotherapy, discusses the use of end points for its assessment and examines the influence of clinical and biochemical prognostic factors on the natural history of malignant pleural mesothelioma. Early-phase clinical trials of second-line and novel agents are emerging from an increased understanding of mesothelioma cell biology. Coupled with high-quality translational research, such developments have real potential to improve the outlook of patients at a time of increasing incidence.

Preliminary data suggestive of a novel translational approach to mesothelioma treatment: imatinib mesylate with gemcitabine or pemetrexed

BACKGROUND

Malignant mesothelioma is a cancer which is refractory to current treatments. Imatinib mesylate is a selective inhibitor of tyrosine kinases such as bcr-abl, c-Kit, c-Fms and platelet derived growth factor receptor beta (PDGFRbeta). PDGFRbeta is often overexpressed in mesothelioma cells and is a therapeutic target for imatinib in some solid tumours. A study was undertaken to assess whether imatinib alone or combined with chemotherapeutic agents may be effective for treating mesothelioma.

METHODS

Cultures from mesothelioma MMP, REN and ISTMES2 cell lines were treated with imatinib alone or in combination with a chemotherapeutic agent.

RESULTS

Imatinib induced cytotoxicity and apoptosis selectively on PDGFRbeta positive mesothelioma cells via blockade of receptor phosphorylation and interference with the Akt pathway. Of the chemotherapeutic agents tested in combination with imatinib, a synergistic effect was obtained with gemcitabine and pemetrexed.

CONCLUSIONS

This study provides a rationale for a novel translational approach to the treatment of mesothelioma which relies on enhancement of tumour chemosensitivity by inhibition of Akt.

Aberrant promoter methylation of insulin-like growth factor binding protein-3 gene in human cancers

Insulin-like growth factor binding protein-3 (IGFBP-3) is postulated to be a mediator of growth suppression signals. Here, we examined the methylation status of IGFBP-3 to correlate to clinicopathological factors in human cancers. The methylation status of IGFBP-3 was determined by bisulfite DNA sequencing and was correlated with expression semi-quantified by real-time RT-PCR to develop a methylation-specific PCR (MSP) assay for IGFBP-3. Using the MSP assay, we examined the methylation status of IGFBP-3 in gastric cancer (GC), colorectal cancer (CRC), breast cancer (BC) and malignant mesothelioma (MM). IGFBP-3 methylation was detected in 6 of 13 (46%) and 16 of 24 (67%) GC cell lines and tumors, respectively; 4 of 8 (50%) and 15 of 26 (58%) CRC cell lines and tumors, respectively; 3 of 11 (27%) and 7 of 39 (18%) BC cell lines and tumors, respectively and 1 of 5 (20%) and 18 of 56 (32%) MM cell lines and tumors, respectively. Interestingly, the methylation status of MM specimens from Japanese patients (75%, 12 out of 16 patients) was significantly higher than those from the USA (15%, 6 out of 40 patients) (p < 0.0001), suggesting the presence of ethnic differences in the IGFBP-3 methylation status. We also found that IGFBP-3 methylation was preferentially present in GCs arising in the lower-third of the stomach (p = 0.079). In summary, our results showed that IGFBP-3 methylation played an important role in the silencing of its expression, suggesting that IGFBP-3 may act as a tumor suppressor gene in several human cancers examined.

Expression of Cancer-Associated Molecules in Malignant Mesothelioma

Malignant mesothelioma (MM) is a malignant tumor derived from mesothelial cells, native cells of the body cavities. Exposure to asbestos is the most strongly established etiologic factor, predominantly for the most common disease form, pleural mesothelioma. The pathogenesis of MM involves the accumulation of extensive cytogenetic changes, as well as cancer-related phenotypic alterations that facilitate tumor cell survival, invasion and metastasis. This review presents current knowledge regarding the biological characteristics of this disease that are linked to the so-called hallmarks of cancer. In addition, data suggesting that the anatomic site (solid tumor vs. effusion) affects the expression of metastasis-associated and regulatory molecules in MM are presented. Finally, recent work in which high-throughput methodology has been applied to MM research is reviewed. The data obtained in the reviewed research may aid in defining new prognostic markers and therapeutic targets for this aggressive disease in the future.

Insulin-like growth factors and breast cancer therapy

Despite improvements in breast cancer therapy in recent years, additional therapies need to be developed. New therapies may have activity by themselves or may have utility in combination with other agents. Population, preclinical, and basic data suggest the insulin-like growth factor (IGF) system functions to maintain the malignant phenotype in breast cancer. Since the IGFs act via transmembrane tyrosine kinase receptors, targeting of the key receptors could provide a new pathway in breast cancer. In addition, IGF action enhances cell survival, so combination of anti-IGF therapy with conventional cytotoxic drugs could lead to synergistic effects. In this review, we will discuss the rationale for targeting the IGF system, potential methods to disrupt IGF signaling, and identify potential interactions between IGF inhibitors and other anti-tumor strategies. We will also identify important issues to consider when designing clinical trials.

Suppression of insulin receptor substrate 1 (IRS-1) promotes mammary tumor metastasis

The insulin receptor substrate (IRS) proteins are cytoplasmic adaptors that organize signaling complexes downstream of activated cell surface receptors. Here, we show that IRS-1 and IRS-2, despite significant homology, play critical yet distinct functions in breast cancer, and we identify specific signaling pathways that are influenced by IRS-1 using the polyoma virus middle-T (PyV-MT) transgenic mouse model of mammary carcinoma and Irs-1 null (Irs1(-/-)) mice. The absence of Irs-1 expression enhanced metastatic spread significantly without a significant effect on primary tumor growth. Orthotopic transplant studies revealed that the increased metastatic potential of Irs1-deficient tumor cells is cell autonomous. Mammary tumors that developed in PyV-MT::Irs1(-/-) mice exhibited elevated Irs-2 function and enhanced phosphatidylinositol 3-kinase/Akt/mTor activity, suggesting that one mechanism by which Irs-1 impedes metastasis is to suppress Irs-2-dependent signaling. In support of this mechanism, reduction of Irs-2 expression in Irs1(-/-) tumor cells restored mTor signaling to wild-type levels. PyV-MT::Irs1(-/-) tumors also exhibited a significant increase in vascular endothelial growth factor expression and microvessel density, which could facilitate their dissemination. The significance of our findings for human breast cancer is heightened by our observation that Irs-1 is inactivated in wild-type, metastatic mammary tumors by serine phosphorylation. Collectively, our findings reveal that inactivation of IRS-1 enhances breast cancer metastasis and support the novel hypothesis that IRS-1 has metastasis suppressor functions for breast cancer.

Effects of insulin-like growth factor-1 receptor inhibition in mesothelioma. Thoracic Surgery Directors Association Resident Research Award

BACKGROUND

Malignant mesothelioma is a devastating disease with a poor prognosis. Recent data have shown that insulin-like growth factor-1 receptor (IGF-1R) may play a role in oncogenic signaling. Our aim was to evaluate the effect of a novel IGF-1R inhibitor, NVP-AEW541, on cell growth and IGF associated pathways.

METHODS

Malignant mesothelioma cell lines, H2373 and H2461, previously shown to activate the IGF pathway were grown in culture. The adherent cells, initially plated at 5 x 10(5) cells/plate, were treated for 72 hours, in triplicate, with varying concentration of NVP-AEW541 (0, 1, 5, 10, 20, and 50 microM). Viable cells were counted every 24 hours. Additionally, separate cultures in serum-free medium were treated with NVP-AEW541, then stimulated with IGF and lysates collected for immunoblot analysis.

RESULTS

In both cell lines, 0, 1, 5, and 10 microM showed an inhibitory or static effect, while 20 and 50 microM were cidal. Immunoblot analysis demonstrated that phosphorylation of IGF-1R was inhibited by NVP-AEW541 at higher concentration. Phosphorylation of mitogen-activated protein kinase and Akt, downstream IGF pathway mediators, were also shown to be repressed by drug treatment.

CONCLUSIONS

NVP-AEW541 has a concentration-dependent inhibitory effect on mesothelioma cells in culture. NVP-AEW541 acts by inhibition of IGF-1R phosphorylation. Inhibition effects phosphorylation of downstream mediators in a dose-dependent fashion. Inhibition of the IGF pathway decreases viability of mesothelioma cell culture. Further evaluation of NVP-AEW541, and other selective IGF-1R inhibitors, may play an important role in multimodal treatment of malignant mesothelioma.