Article

Oncogenic KIT signaling and therapeutic intervention in a mouse model of gastrointestinal stromal tumor

Department of Developmental Biology, Computational Biology Center, and Molecular Cytology Facility, Sloan-Kettering Institute, New York, NY 10021, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 09/2006; 103(34):12843-8. DOI: 10.1073/pnas.0511076103
Source: PubMed

ABSTRACT Kit receptor-activating mutations are critical in the pathogenesis of gastrointestinal stromal tumors (GIST). We investigated mechanisms of oncogenic Kit signaling and the consequences of therapeutic intervention in a mouse model of human GIST. Treatment of GIST mice with imatinib decreased cell proliferation and increased apoptosis in the tumor. Analysis of tumor tissue from imatinib-treated mice showed diminished phosphatidylinositol 3-kinase (PI3-kinase) and mammalian target of rapamycin (mTOR) signaling suggesting that oncogenic Kit signaling critically contributes to the translational response in GIST. Treatment with RAD001 (everolimus), an mTOR inhibitor, diminished the translational response and cell proliferation in tumor lesions, pointing to mTOR inhibition as a therapeutic approach for imatinib-resistant GIST. Analysis of RNA expression profiles in GIST lesions with and without imatinib treatment showed changes in expression of IFN-inducible genes and cell cycle regulators. These results convincingly show that KitV558Delta/+ mice represent a unique faithful mouse model of human familial GIST, and they demonstrate the utility of these mice for preclinical investigations and to elucidate oncogenic signaling mechanisms by using genetic approaches and targeted pharmacological intervention.

Download full-text

Full-text

Available from: Gunhild Sommer, Aug 21, 2015
0 Followers
 · 
163 Views
  • Source
    • ". In addition, we have also added to the grading system the area with myxoid degeneration, which is characterized by the replacement of viable tumor tissue by an amorphous matrix with low cellularity as a pattern of response to TKI treatment observed [21]. Mitotic figures and apoptotic cells were counted in 10 high power fields (0.45-mm field diameter) at × 400 magnification on H&E staining. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We evaluated the efficacy of CK6, a KIT monoclonal antibody, in a panel of human gastrointestinal stromal tumor (GIST) xenograft models. Nude mice were bilaterally transplanted with human GIST xenografts (four patient derived and two cell line derived), treated for 3 weeks, and grouped as follows: control (untreated); CK6 (40 mg/kg, 3× weekly); imatinib (50 mg/kg, twice daily); sunitinib (40 mg/kg, once daily); imatinib + CK6; sunitinib + CK6 (same doses and schedules as in the single-agent treatments). Tumor volume assessment, Western blot analysis, and histopathology were used for evaluation of efficacy. Statistical analysis was performed using Mann-Whitney U (MWU) and Wilcoxon matched-pairs tests. CK6 as a single agent only reduced tumor growth rate in the UZLX-GIST3 model (P = .053, MWU compared to control), while in none of the other GIST models an effect on tumor growth rate was observed. CK6 did not result in significant anti-proliferative or pro-apoptotic effects in any of the GIST models, and moreover, CK6 did not induce a remarkable inhibition of KIT activation. Furthermore, no synergistic effect of combining CK6 with tyrosine kinase inhibitors (TKIs) was observed. Conversely, in certain GIST xenografts, anti-tumor effects seemed to be inferior under combination treatment compared to single-agent TKI treatment. In the GIST xenografts tested, the anti-tumor efficacy of CK6 was limited. No synergy was observed on combination of CK6 with TKIs in these GIST models. Our findings highlight the importance of using relevant in vivo human tumor xenograft models in the preclinical assessment of drug combination strategies. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Translational oncology 04/2015; 369(2). DOI:10.1016/j.tranon.2015.02.004 · 3.40 Impact Factor
  • Source
    • "C-KIT protein (CD117) expression has been reported to be 95% positive in GIST and suggested by the World Health Organization to be a defining feature of GISTs (Ponsaing et al., 2007). Gene mutation of KIT or platelet-derived growth factor receptor alpha are reported to induce oncogenic signalling in the absence of their ligands, leading to activation of the PI3K-AKT and MEK- MAPK pathways that promote tumorigenesis (Heinrich et al., 2003; Rossi et al., 2006; Liegl-Atzwanger et al., 2010). Most GISTs are positive for CD34 and heavy molecular weight caldesmon (Miettinen et al., 1999b; Miettinen et al., 2006). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors that account for about 2% of gastric tumors. Metallothioneins (MTs) are multifunctional proteins associated with carcinogenesis and known to be coded by 10 functional MT genes. This study evaluated MT mRNA and protein expression in GISTs and compared the expression levels with gastric carcinomas. An immunohistochemical study of MT protein expression was performed in 15 GISTs (specifically located in the stomach) and 38 early stage gastric carcinomas. The percentage of cells stained and intensity of staining were determined. MT-2A mRNA expression was investigated in 6 GISTs and 6 early stage gastric carcinoma patients. All GISTs displayed positive nuclear immunostaining, with most GISTs having predominantly mildly stained nuclei (93.3%). On the other hand, 37 out of 38 gastric carcinoma cases were positively stained for nuclear MT with 24 cases (63.2%) exhibiting predominantly mild nuclear staining, 7 cases (18.4%) moderate nuclear staining, and 6 cases (15.8%) strong nuclear staining. Nuclear MT expression was found to be significantly lower in GIST samples when compared with gastric carcinoma tissues based on the percentage stained and immunoreactive score. We then established that the MT-2A gene transcript was the most abundant MT isoform in MKN28 gastric cancer cells and analyzed its expression in GIST and gastric carcinoma tissues. We found that GISTs had significantly lower MT-2A mRNA levels than gastric carcinoma tissues. Lower MT-2A gene expression and nuclear MT protein expression in GISTs when compared with gastric carcinomas may reflect their different underlying biology and divergent histogenesis.
    The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 02/2011; 294(2):267-72. DOI:10.1002/ar.21321 · 1.53 Impact Factor
  • Source
    • "The role of oncogenic KIT signaling on ERK1/2 activation has been recently evaluated by our group in a KIT V558Δ/+ GIST mouse model, produced by a knock-in strategy introducing a KIT exon 11-activating mutation into the mouse genome (Rossi et al., 2006). Although untreated tumors show consistent activation of ERK1/2 phosphorylation, there is no effect of imatinib treatment on ERK activation (Rossi et al., 2006). Thus BRAF mutated GIST patients may be similarly resistant to imatinib inhibition. "
    [Show abstract] [Hide abstract]
    ABSTRACT: BRAF and NRAS are commonly mutated in cancer and represent the most frequent genetic events in malignant melanoma. More recently, a subset of melanomas was shown to overexpress KIT and harbor KIT mutations. Although most gastrointestinal stromal tumors (GISTs) exhibit activating mutations in either KIT or PDGFRA, about 10% of the cases lack mutations in these genes. It is our hypothesis following the melanoma model that mutations in BRAF or NRAS may play a role in wild-type GIST pathogenesis. Alterations in RAS/MEK/ERK pathway may also be involved in development of imatinib resistance in GIST, particularly in tumors lacking secondary KIT or PDGFRA mutations. Imatinib-naive wild-type GISTs from 61 patients, including 15 children and 28 imatinib-resistant tumors without secondary KIT mutations were analyzed. Screening for hot spots mutations in BRAF (exons 11 and 15) and NRAS (exons 2 and 3) was performed. A BRAF exon 15 V600E was identified in 3 of 61 GIST patients, who shared similar clinical features, being 49- to 55-years-old females and having their tumors located in the small bowel. The tumors were strongly KIT immunoreactive and had a high risk of malignancy. An identical V600E BRAF mutation was also identified in one of 28 imatinib resistant GIST lacking a defined mechanism of drug resistance. In conclusion, we identified a primary BRAF V600E mutations in 7% of adult GIST patients, lacking KIT/PDGFRA mutations. The BRAF-mutated GISTs show predilection for small bowel location and high risk of malignancy. A secondary V600E BRAF mutation could represent an alternative mechanism of imatinib resistance. Kinase inhibitors targeting BRAF may be effective therapeutic options in this molecular GIST subset.
    Genes Chromosomes and Cancer 10/2008; 47(10):853-9. DOI:10.1002/gcc.20589 · 3.84 Impact Factor
Show more