Transforming Growth Factor Receptor Type II Inactivation Induces the Malignant Transformation of Intestinal Neoplasms Initiated by Apc Mutation
Vanderbilt University, Нашвилл, Michigan, United States Cancer Research
(Impact Factor: 9.33).
11/2006; 66(20):9837-44. DOI: 10.1158/0008-5472.CAN-06-0890
The transforming growth factor-beta (TGF-beta) signaling pathway is a tumor-suppressor pathway that is commonly inactivated in colon cancer. TGF-beta is a secreted ligand that mediates its effects through a transmembrane heteromeric receptor complex, which consists of type I (TGFBR1) and type II subunits (TGFBR2). Approximately 30% of colon cancers carry TGFBR2 mutations, demonstrating that it is a common target for mutational inactivation in this cancer. To assess the functional role of TGFBR2 inactivation in the multistep progression sequence of colon cancer, we generated a mouse model that recapitulates two common genetic events observed in human colon cancer by mating Apc(1638N/wt) mice with mice that are null for Tgfbr2 in the intestinal epithelium, Villin-Cre;Tgfbr2(E2flx/E2flx) mice. In this model, we observed a dramatic increase in the number of intestinal adenocarcinomas in the Apc(1638N/wt);Villin-Cre;Tgfbr2(E2flx/E2flx) mice (called Apc(1638N/wt);Tgfbr2(IEKO)) compared with those mice with intact Tgfbr2 (Apc(1638N/wt);Tgfbr2(E2flx/E2flx)). Additionally, in vitro analyses of epithelial tumor cells derived from the Apc(1638N/wt);Tgfbr2(IEKO) mice showed enhanced expression and activity of matrix metalloproteinase MMP-2 and MMP-9, as well as increased TGF-beta1 secretion in the conditioned medium. Similarly, primary tumor tissues from the Apc(1638N/wt);Tgfbr2(IEKO) mice also showed elevated amounts of TGF-beta1 as well as higher MMP-2 activity in comparison with Apc(1638N/wt);Tgfbr2(E2flx/E2flx)-derived tumors. Thus, loss of TGFBR2 in intestinal epithelial cells promotes the invasion and malignant transformation of tumors initiated by Apc mutation, providing evidence that Wnt signaling deregulation and TGF-beta signaling inactivation cooperate to drive the initiation and progression, respectively, of intestinal cancers in vivo.
Available from: Ji-Liang Li
- "In addition, a relatively high intracellular expression and secretion of TGF-β1 were observed upon miR-93-mediated TGFβR2 down-regulation, which was consistent with a report by Munoz  who believed that it was possibly due to the attenuated TGF-β signaling pathway. This hints its undefined effects on NPC aggressiveness, which deserves further investigations. "
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ABSTRACT: MiR-17-92 cluster and its paralogues have emerged as crucial regulators of many oncogenes and tumor suppressors. Transforming growth factor-beta receptor II (TGFbetaR2), as an important tumor suppressor, is involved in various cancer types. However, it is in cancer that only two miRNAs of this cluster and its paralogues have been reported so far to regulate TGFbetaR2. MiR-93 is oncogenic, but its targetome in cancer has not been fully defined. The role of miR-93 in nasopharyngeal carcinoma (NPC) still remains largely unknown.
We firstly evaluated the clinical signature of TGFbetaR2 down-regulation in clinical samples, and next used a miRNA expression profiling analysis followed by multi-validations, including Luciferase reporter assay, to identify miRNAs targeting TGFbetaR2 in NPC. In vitro and in vivo studies were performed to further investigate the effects of miRNA-mediated TGFbetaR2 down-regulation on NPC aggressiveness. Finally, mechanism studies were conducted to explore the associated pathway and genes influenced by this miRNA-mediated TGFbetaR2 down-regulation.
TGFbetaR2 was down-regulated in more than 50% of NPC patients. It is an unfavorable prognosis factor contributing to clinical NPC aggressiveness. A cluster set of 4 TGFbetaR2-associated miRNAs was identified; they are all from miR-17-92 cluster and its paralogues, of which miR-93 was one of the most significant miRNAs, directly targeting TGFbetaR2, promoting cell proliferation, invasion and metastasis in vitro and in vivo. Moreover, miR-93 resulted in the attenuation of Smad-dependent TGF-beta signaling and the activation of PI3K/Akt pathway by suppressing TGFbetaR2, further promoting NPC cell uncontrolled growth, invasion, metastasis and EMT-like process. Impressively, the knockdown of TGFbetaR2 by siRNA displayed a consentaneous phenocopy with the effect of miR-93 in NPC cells, supporting TGFbetaR2 is a major target of miR-93. Our findings were also substantiated by investigation of the clinical signatures of miR-93 and TGFbetaR2 in NPC.
The present study reports an involvement of miR-93-mediated TGFbetaR2 down-regulation in NPC aggressiveness, thus giving extended insights into molecular mechanisms underlying cancer aggressiveness. Approaches aimed at blocking miR-93 may serve as a promising therapeutic strategy for treating NPC patients.
Available from: Rui Medeiros
- "Reduced TGFBR2 expression levels are correlated with a shorter survival rate of colon cancer patients, as does the reduced expression of the co-receptor betaglycan in breast and PC patients [8,9]. High expression levels of TGFBR2 can mediate the pro-apoptotic function of the TGFβ1 signaling pathway and its loss promotes invasion and malignant transformation [10,11]. "
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ABSTRACT: Prostate cancer (PC) is the most frequently diagnosed cancer in men. The acquisition of castration-resistant (CR) phenotype is associated with the activation of signaling pathways mediated by growth factors. The TGFβ1 and its receptors have an important role in tumor progression, being the pro-apoptotic function modulated by the expression of TGFBR2. A single nucleotide polymorphism -875 G > A in TGFBR2 gene has been described, which may influence the expression levels of the receptor. Our purpose was to investigate the potential role of TGFBR2-875G>A in PC risk and in the response to androgen deprivation therapy (ADT). TGFBR2-875G>A polymorphism was studied by allelic discrimination using real-time polymerase chain reaction (PCR) in 891 patients with PC and 874 controls. A follow-up study was undertaken to evaluate response to ADT. The TGFBR2 and SMAD7 mRNA expression were analyzed by a quantitative real-time PCR. We found that TGFBR2-875GG homozygous patients present lower expression levels of TGFBR2 mRNA (AA/AG: 2(-ΔΔCT) =1.5, P=0.016). GG genotype was also associated with higher Gleason grade (OR=1.51, P=0.019) and increased risk of an early relapse after ADT (HR=1.47, P=0.024). The concordance (c) index analysis showed that the definition of profiles that contains information regarding tumor characteristics associated with genetic information present an increased capacity to predict the risk for CR development (c-index model 1: 0.683 vs model 2: 0.736 vs model 3: 0.746 vs model 4: 0.759). The TGFBR2-875G>A contribution to an early relapse in ADT patients, due to changes in mRNA expression, supports the involvement of TGFβ1 pathway in CRPC. Furthermore, according to our results, we hypothesize the potential benefits of the association of genetic information in predictive models of CR development.
Available from: Alan R Clarke
- "Mu~ noz et al., used a mouse model which do not express TGF-b receptor II within the intestinal epithelium and found that these mice develop spontaneous tumours only very infrequently . However, when they crossed onto an Apc 1638N/wt background in order to study the effects of loss of TGF-b signalling in the context of aberrant Wnt-signalling the mouse presented with no significant increase in the number of neoplastic intestinal lesions than was seen in the Apc 1638N/wt mouse with functional TGF-b receptor II, but with a drastically increased proportion of lesion categorised as advanced, high grade and adenocarcinomas (Mu~ noz et al., 2006). This mouse model has not only increased our understanding of factors "
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ABSTRACT: Colorectal cancer (CRC) is the third most common cancer in the UK, with over 37,500 people being diagnosed every year. Survival rates for CRC have doubled in the last 30 years and it is now curable if diagnosed early, but still over half of all sufferers do not survive for longer than 5 years after diagnosis. The major complication to treating this disease is that of metastasis, specifically to the liver, which is associated with a 5 year survival of less than 5%. These statistics highlight the importance of the development of earlier detection techniques and more targeted therapeutics. The future of treating this disease therefore lies in increasing understanding of the mutations which cause tumourigenesis, and insight into the development and progression of this complex disease. This can only be achieved through the use of functional models which recapitulate all aspects of the human disease. There is a wide range of models of CRC available to researchers, but all have their own strengths and weaknesses. Here we review how CRC can be modelled and discuss the future of modelling this complex disease, with a particular focus on how genetically engineered mouse models have revolutionised this area of research.
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