ABSTRACT
Inhibition of KIT-signaling is a major molecular target for gastrointestinal stromal tumor (GIST) therapy, and imatinib mesylate (IM) is known as the most effective first-line treatment option for patients with advanced, unresectable, and/or metastatic GISTs. We show here for the first time that the inhibition of KIT-signaling in GISTs induces profound changes in the cellular secretome, leading to the release of multiple chemokines, including FGF-2. IM increased migration, invasion, and colony formation of IM-resistant GISTs in an FGF2-dependent manner, whereas the use of blocking anti-FGF2 antibodies or BGJ398, a selective FGFR inhibitor, abolished these effects, thus suggesting that the activation of FGF2-mediated signaling could serve as a compensatory mechanism of KIT-signaling inhibited in GISTs. Conversely, FGF-2 rescued the growth of IM-naive GISTs treated by IM and protected them from IM-induced apoptosis, consistent with the possible involvement of FGF-2 in tumor response to IM-based therapy. Indeed, increased FGF-2 levels in serum and tumor specimens were found in IM-treated mice bearing IM-resistant GIST xenografts, whereas BGJ398 used in combination with IM effectively inhibited their growth. Similarly, increased FGF-2 expression in tumor specimens from IM-treated patients revealed the activation of FGF2-signaling in GISTs in vivo. Collectively, the continuation of IM-based therapy for IM-resistant GISTs might facilitate disease progression by promoting the malignant behavior of tumors in an FGF2-dependent manner. This provides a rationale to evaluate the effectiveness of the inhibitors of FGF-signaling for IM-resistant GISTs.
ABSTRACT
The diagnosis of 17 small-cell round tumors of the bone and soft tissue, which were histologically similar to Ewing's sarcoma (EWS), was verified on paraffin sections, by using tissue microarray (TMA) technology, immunohistochemistry, cytogenetic (FISH) and molecular biological (RT-PCR) methods. Classical EWS was found to be in 8 patients, large-cell EWS in 1 patient; atypical EWS in 1, and endothelial ESW in 1. Two patients were diagnosed as having primitive neuroectodermal tumor (PNET), synovial sarcoma was present in 1 patient, embryonic rhabdomyosarcoma in 1, high-grade undifferentiated sarcoma in 1 and diffuse B-cell large-cell lymphoma in 1. TMA makes it possible to perform a number of diagnostic procedures on the same block containing a copious number of tumor samples and to assess the results of their use. It is emphasized that the diagnosis of small-cell round tumors requires the use of a package of the currently available methods providing the qualitative characteristics of each neoplasm.
