Molecular Characterization of PDGFR‐α/PDGF‐A and c‐KIT/SCF in Gliosarcomas

Abstract

Gliosarcomas are rare and poorly characterized malignant brain tumors that exhibit a biphasic tissue pattern with areas of gliomatous and sarcomatous differentiation. These tumors are histological variants of glioblastoma, displaying a similar genetic profile and dismal prognosis. Up-regulation of PDGFR subfamily of tyrosine kinase members, PDGFR-α and c-Kit, and their intracellular effectors RAS/RAF/MAPK has a crucial role in the cancer development. In addition, signal transduction mediated by activating mutations of c-Kit and PDGFR can be effectively blocked by specific tyrosine kinase inhibitors, such as Imatinib mesylate. The aim of this study was to characterize the molecular alterations of PDGFR signaling in gliosarcomas. Six cases were analyzed by immunohistochemistry for the expression of PDGFR-α, c-Kit and their ligands PDGF-A and SCF, respectively. The cases were further evaluated for the presence of activating mutations of PDGFR-α (exons 12 and 18) and c-kit (exons 9, 11, 13, and 17), as well as B-RAF (exons 11 and 15). Expression of PDGF-A was found in all cases and co-expression of PDGFR-α was observed in three cases. Four cases showed expression of SCF, and c-Kit was observed only in one case that also expressed SCF. Generally, immunoreaction predominates in the glial component. The mutational analysis of PDGFR-α showed the presence of an IVS17-50insT intronic insertion in two cases, one of them also with a 2472C > T silent mutation; this silent mutation was also found in another case. Glioma cell line analysis of IVS17-50insT insertion showed no influence on PDGFR-α gene splicing. No mutations were detected in c-kit and B-RAF oncogenes. Our Results indicate that activating mutations of PDGFR-α, c-kit and B-RAF are absent in gliosarcomas. Nevertheless, the presence of a PDGFR-a/PDGFA and c-Kit/SCF autocrine/paracrine stimulation loop in a proportion of cases, supports the potential role of specific tyrosine kinase inhibitors in the treatment of gliosarcomas.

Automated Network Analysis Identifies Core Pathways in Glioblastoma

“…However, these genes may represent additional drivers and targets of amplification. For example, KIT has been identified as a proto-oncogene, and has been previously implicated in glioblastoma [40] – [42] . KDR encodes one of the two receptors of the Vascular Endothelial Growth Factor (VEGF), and maintains a key role in regulating angiogenesis-related functions [43] .…”

Expression, mutation and copy number analysis of platelet-derived growth factor receptor A (PDGFRA) and its ligand PDGFA in gliomas

“…Representative 3- μ m thick sections were cut from formalin-fixed and paraffin-embedded samples and subjected to immunohistochemical analysis. Immunohistochemistry was carried out using a LabVision Autostainer (LabVision Corporation, Fremont, CA, USA) and the streptavidin—biotin–peroxidase complex technique, with rabbit polyclonal antibodies raised against human PDGFA (clone N-30, dilution 1:80; Santa Cruz Biotechnology, Santa Cruz, USA), and PDGFRA (dilution 1:175; LabVision Corporation) as previously described ( Carvalho et al , 2005 ; Reis et al , 2005 ). In brief, deparaffinised and rehydrated sections used to study PDGFA expression were pre-treated by microwaving in 10 m citrate buffer (pH 6.0) three times for 5 min at 600 W. The sections used for PDGFRA expression were submitted to heat-induced antigen retrieval with 10 m citrate buffer (pH 6.0) for 20 min in a water bath.…”

“…All sections were counterstained with Gill-2 haematoxylin. As previously described ( Reis et al , 2005 ), both the distribution and intense immunoreactivity were semi-quantitatively scored by JML and ALF independently with the observers blinded to the clinical information and results of the other molecular tests as follows: (−) (negative), (+) (⩽5%), (++) (5–50%), and (+++) (>50%). Samples with scores (−) and (+) were considered negative, and those with scores (++) and (+++) were considered positive.…”

Analysis of a synchronous gliosarcoma and meningioma with long survival: A case report and review of the literature

“…The screening of mutations was carried out by polymerase chain reaction (PCR)-single-strand conformational polymorphism (PCR-SSCP), followed by direct DNA sequencing, as previously described. [ 27 29 ] None of lesions showed TP53 or BRAF mutations [ Table 1 ].…”

“…[ 2 24 ] The occurrence of similar genetic alterations in both glial and mesenchymal components supports the concept of a monoclonal origin of the metaplastic mesenchymal differentiation from the astrocytic component. [ 11 12 28 29 ] However, the molecular mechanisms governing this mesenchymal differentiation are still unclear. Interestingly, a recent study report the isolation of gliosarcoma stem cells, which were able to further undergo glial and mesenchymal differentiation.…”