Selective modulation of type 1 insulin-like growth factor receptor signaling and functions by beta1 integrins

We show here that beta1 integrins selectively modulate insulin-like growth factor type I receptor (IGF-IR) signaling in response to IGF stimulation. The beta1A integrin forms a complex with the IGF-IR and insulin receptor substrate-1 (IRS-1); this complex does not promote IGF-I mediated cell adhesion to laminin (LN), although it does support IGF-mediated cell proliferation. In contrast, beta1C, an integrin cytoplasmic variant, increases cell adhesion to LN in response to IGF-I and its down-regulation by a ribozyme prevents IGF-mediated adhesion to LN. Moreover, beta1C completely prevents IGF-mediated cell proliferation and tumor growth by inhibiting IGF-IR auto-phosphorylation in response to IGF-I stimulation. Evidence is provided that the beta1 cytodomain plays an important role in mediating beta1 integrin association with either IRS-1 or Grb2-associated binder1 (Gab1)/SH2-containing protein-tyrosine phosphate 2 (Shp2), downstream effectors of IGF-IR: specifically, beta1A associates with IRS-1 and beta1C with Gab1/Shp2. This study unravels a novel mechanism mediated by the integrin cytoplasmic domain that differentially regulates cell adhesion to LN and cell proliferation in response to IGF

Selective modulation of type 1 insulin-like growth factor receptor signaling and functions by β1 integrins

We show here that β1 integrins selectively modulate insulin-like growth factor type I receptor (IGF-IR) signaling in response to IGF stimulation. The β1A integrin forms a complex with the IGF-IR and insulin receptor substrate-1 (IRS-1); this complex does not promote IGF-I mediated cell adhesion to laminin (LN), although it does support IGF-mediated cell proliferation. In contrast, β1C, an integrin cytoplasmic variant, increases cell adhesion to LN in response to IGF-I and its down-regulation by a ribozyme prevents IGF-mediated adhesion to LN. Moreover, β1C completely prevents IGF-mediated cell proliferation and tumor growth by inhibiting IGF-IR auto-phosphorylation in response to IGF-I stimulation. Evidence is provided that the β1 cytodomain plays an important role in mediating β1 integrin association with either IRS-1 or Grb2-associated binder1 (Gab1)/SH2-containing protein-tyrosine phosphate 2 (Shp2), downstream effectors of IGF-IR: specifically, β1A associates with IRS-1 and β1C with Gab1/Shp2. This study unravels a novel mechanism mediated by the integrin cytoplasmic domain that differentially regulates cell adhesion to LN and cell proliferation in response to IGF

OPCML Is a Broad Tumor Suppressor for Multiple Carcinomas and Lymphomas with Frequently Epigenetic Inactivation

Background: Identification of tumor suppressor genes (TSGs) silenced by CpG methylation uncovers the molecular mechanism of tumorigenesis and potential tumor biomarkers. Loss of heterozygosity at 11q25 is common multiple tumors including nasopharyngeal carcinoma (NPC). OPCML, located at 11q25, is one of the downregulated genes we identified through digital expression subtraction. Methodology/Principal Findings: Semi-quantitative RT-PCR showed frequent OPCML silencing in NPC and other common tumors, with no homozygous deletion detected by multiplex differential DNA-PCR. Instead, promoter methylation of OPCML was frequently detected in multiple carcinoma cell lines (nasopharyngeal, esophageal, lung, gastric, colon, liver, breast, cervix, prostate), lymphoma cell lines (non-Hodgkin and Hodgkin lymphoma, nasal NK/T-cell lymphoma) and primary tumors, but not in any non-tumor cell line and seldom weakly methylated in normal epithelial tissues. Pharmacological and genetic demethylation restored OPCML expression, indicating a direct epigenetic silencing. We further found that OPCML is stress-responsive, but this response is epigenetically impaired when its promoter becomes methylated. Ecotopic expression of OPCML led to significant inhibition of both anchorage-dependent and -indendent growth of carcinoma cells with endogenous silencing. Conlusions/Significance: Thus, through functional epigenetics, we identified OPCML as a broad tumor suppressor, which is frequently inactivated by methylation in multiple malignancies. © 2008 Cui et al.published_or_final_versio

Production of Altered Cell Foci by 3-Methylcholanthrene in Mouse Cells Infected with AKR Leukemia Virus

This report describes altered cell foci observed 9-14 days after treatment with 3-methylcholanthrene of mouse-embryo tissue cultures that had previously been infected with wild-type AKR (RNA tumor) virus. The foci consisted of randomly oriented, piled-up, spindle-shaped cells. When heavily stained with Giemsa, the colonies of transformed cells were grossly visible and countable. Under the same experimental conditions, such changes of morphology were not detectable in the uninfected cells treated with 3-methylcholanthrene or in untreated cells infected with virus. The procedure may provide a rapid, quantitative test system for measurement of the oncogenic potential of certain carcinogens. As in similar previous studies in rat and hamster cells, the results suggest that the infectious, but nontransforming, RNA tumor viruses provided nascent oncogenic information, which when activated by 3-methylcholanthrene served as the specific genetic determinants of transformation

Mitochondria Biogenesis and Bioenergetics Gene Profiles in Isogenic Prostate Cells with Different Malignant Phenotypes

Background. The most significant hallmarks of cancer are directly or indirectly linked to deregulated mitochondria. In this study, we sought to profile mitochondria associated genes in isogenic prostate cell lines with different tumorigenic phenotypes from the same patient. Results. Two isogenic human prostate cell lines RC77N/E (nonmalignant cells) and RC77T/E (malignant cells) were profiled for expression of mitochondrial biogenesis and energy metabolism genes by qRT-PCR using the Human Mitochondria and the Mitochondrial Energy Metabolism RT2 PCR arrays. Forty-seven genes were differentially regulated between the two cell lines. The interaction and regulatory networks of these genes were generated by Ingenuity Pathway Analysis. UCP2 was the most significantly upregulated gene in primary adenocarcinoma cells in the current study. The overexpression of UCP2 upon malignant transformation was further validated using human prostatectomy clinical specimens. Conclusions. This study demonstrates the overexpression of multiple genes that are involved in mitochondria biogenesis, bioenergetics, and modulation of apoptosis. These genes may play a role in malignant transformation and disease progression. The upregulation of some of these genes in clinical samples indicates that some of the differentially transcribed genes could be the potential targets for therapeutic interventions

Integration and loss of a single ν-Ki-ras gene affects tumorigenic potential of human osteosarcoma cells

AbstractThe human osteosarcoma cell line Te85 clone F-5 is not tumorigenic in vivo. Its transformation with Kirsten murine sarcoma virus (KiMSV) (KHOS) confers full malignant properties and stable non-tumorigenic revertants of this KHOS cell line have been obtained. Here we show that integration and expression of a single copy of the KiMSV proviral DNA, which is totally lost in the HOS 240S revertant, is responsible for the acquisition of tumorigenicity. Cytogenetic analysis and the absence of a residual LTR copy in the revertant cellular genome suggest that the loss of KiMSV provirus is caused either by chromosomal segregation or by recombination not involving the LTR. In addition analysis of the expression of ras proteins revealed no changes in the pattern of c-ras products and the expression of v-ras only in the KHOS cells. All these data suggest that Te85 and HOS 240S cell lines could represent a human alternative recipient system to rodent cells in studies with oncogenes

Comparative Metabolomic and Lipidomic Analysis of Phenotype Stratified Prostate Cells.

Prostate cancer (PCa) is the most prevalent cancer amongst men and the second most common cause of cancer related-deaths in the USA. Prostate cancer is a heterogeneous disease ranging from indolent asymptomatic cases to very aggressive life threatening forms. The goal of this study was to identify differentially expressed metabolites and lipids in prostate cells with different tumorigenic phenotypes. We have used mass spectrometry metabolomic profiling, lipidomic profiling, bioinformatic and statistical methods to identify, quantify and characterize differentially regulated molecules in five prostate derived cell lines. We have identified potentially interesting species of different lipid subclasses including phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), glycerophosphoinositols (PIs) and other metabolites that are significantly upregulated in prostate cancer cells derived from distant metastatic sites. Transcriptomic and biochemical analysis of key enzymes that are involved in lipid metabolism demonstrate the significant upregulation of choline kinase alpha in the metastatic cells compared to the non-malignant and non-metastatic cells. This suggests that different de novo lipogenesis and other specific signal transduction pathways are activated in aggressive metastatic cells as compared to normal and non-metastatic cells