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.

Background: Despite impressive response rates after initiation of IM-based therapy, most GISTs acquire resistance to IM which remains the main driving force to identify novel molecular targets to increase GISTs sensitivity to the current therapeutic regimens.Methods: IM-naive GIST (T-1) and resistant (T-1R and 430) cells were treated with IM alone or in combination with BGJ398 or neutralizing anti-FGF-2 Abs. Cell proliferation and growth were examined by the MTS-based assay and iCELLigence system. Migration and invasion were studied by wound-healing and transwell-invasion assays. Expression of ALDH1A1, CD44, CD26, apoptosis and proliferation markers were examined by RT-PCR and western blotting. Activation of FGF-signaling in GIST xenografts and primary tumors was assesed by WB, IHC-staining and ELISA.

Aim. To assess of adaptive immunity of the duodenal mucosa in neonates with sepsis. Methods. A study of duodenal biopsy specimens obtained during duodenoscopy from neonates who had signs of suspected ulcerative lesions of the digestive tract. Five of them were obtained from infants with clinical and laboratory signs of neonatal sepsis (NS), two from infants without sepsis (comparison group). Immunohistochemical staining was performed using the Novolink Polymer Detection System imaging system with commercial antibodies to CD4, CD8, CD20 and Bcl-2, and the CSAII Biotin-free Tyramide Signal Amplification System imaging system with commercial antibodies to caspase-3 and caspase-9 in accordance with the manufacturers instructions. Results. It was found that the number of CD4+ T-lymphocytes of the duodenal mucosa in neonatal sepsis group in 4 of 5 infants did not differ from the control group. The number of CD8+ lymphocytes in neonates with sepsis in 3 of 5 cases was even higher than in the control group. The number of CD20+ B-lymphocytes in 4 infants with sepsis was significantly less compared with the control. Activation of apoptosis in mucosal cells was detected, which was manifested by a large number of caspase-3-positive cells (in 4 of 5 cases) in comparison with the control group. The number of caspase-9-positive cells in the studied groups was almost equal. A substantial decrease in the number of Bcl-2-positive mucosal cells in all 5 infants with sepsis was noted as compared with the control indicators. Conclusion. The study revealed moderate immunosuppression in the duodenal mucosa in neonates with sepsis, manifested by low values of CD20+ B-lymphocytes in the absence of a significant decrease in the number of CD4+ and CD8+ T-lymphocytes. The detected moderate activation of apoptosis processes against the background of reduced antiapoptotic potential creates the conditions for a possible translocation of the intestinal microbiota into the bloodstream.

Aim. To examine the expression of fibroblast growth factor-2 and its isoforms in gastrointestinal stromal tumors and assess the prognostic value of this marker. Methods. The study included 44 patients with gastric gastrointestinal stromal tumors of the stomach who were prescribed surgical or combined treatment with the targeted drug imatinib (imatinib mesylate). Immunohistochemistry (IHC)-staining and immunoblotting with monoclonal antibodies were used to assess the expression of FGF-2. Statistical analysis for differences in clinical and morphological parameters was performed by using Students, MannWhitneyWilcoxon and Fishers tests. Differences were considered significant at p 0.05. Results. Fibroblast growth factor-2 expression was assessed in tumor tissues in 39 out of 44 analyzed patients. The frequency of fibroblast growth factor-2 expression in the observed patients was 84.6% (33/39). The moderate and strong fibroblast growth factor-2 expression was detected in 21 (53.8%) patients with gastric gastrointestinal stromal tumors. High expression of low-molecular weight (18 kDa) fibroblast growth factor-2 isoform was found in all tumor samples from patients with high-risk gastrointestinal stromal tumor (prognostic group 6) (p=0.039), which indicated the active secretion of this ligand by its signalling pathway in the cancer cells. Patients with high levels of low‐molecular‐weight fibroblast growth factor-2 showed a higher level of Ki-67 proliferative activity (р=0.013) and tumor size (р=0.0017). Patients with increased expression of the low molecular weight isoform of fibroblast growth factor-2 in gastric gastrointestinal stromal tumor had a higher risk of recurrence, as well as larger tumor size and proliferative activity compared with patients without expression of this isoform. The level of fibroblast growth factor-2 expression in tumor samples, determined by immunohistochemistry-staining, increases after initiation of imatinib to based therapy, which may indicate the formation of resistance to this targeted drug and the progression of the disease. Conclusion. The results of the study suggest that FGF-2 might be an independent prognostic marker of gastric gastrointestinal stromal tumor and a viable therapeutic target.