Expression of neurotrophins and their receptors in adult sarcomas.

Abstract

10562 Background: Neurotrophins (NT) influence proliferation, survival, death, and differentiation by binding Tropomyosin-related kinase (Trk) receptors and p75NTR(CD271). While the three Trk-receptors TrkA, TrkB, and TrkC display specific binding to their ligands, i.e. TrkA to NGF (nerve growth factor), TrkB to BDNF (brain-derived neurotrophic factor), NT4/5 (neurotrophin 4/5) and TrkC to NT3 (neurotrophin 3), CD271 shows low affinity to all neurotrophins. Notably, CD271 has been suggested as marker for the prospective isolation of bone marrow mesenchymal stromal cells (MSC), and rhabdomyosarcomas have previously been found to express neurotrophins and NT receptors. Methods: RNA was isolated from sarcoma cell lines and freshly obtained sarcoma (src) cells from patients after surgical resection. RNA was reverse transcribed and cDNA products underwent PCR analysis with specific primers. Furthermore, cell lines from the same primary tissues were established and treated with doxorubicin. Effects of K252a (Trk receptor inhibitor), Pep5 (CD271-Inhibitor), and neurotrophins on sarcoma cell proliferation and survival were analyzed. Results: An array of freshly obtained clinical src samples (n=10 each subtype) was screened for expression of NT3, NT4/5, BDNF, NGF as well as TrkA, TrkB, TrkC, and CD271. Interestingly, src subtype-specific expression patterns were observed. In the established cell lines, K252a increased doxorubicin-induced tumor cell death, while CD271-Inhibitor Pep5 enhanced proliferation in doxorubicin treated cells, especially under serum free conditions and when combined with BDNF and NGF. Conclusions: NT and NT receptors are expressed on all adult src samples screened in this study. Chemotherapy resistant liposrc as well as myxofibrosrc samples displayed the strongest expression of NT3 as well as TrkB, TrkC, and CD271. The concomitant expression of NT and their receptors suggests autocrine self-stimulation, which may propagate survival, proliferation, and treatment resistance. NT receptor tyrosine kinases may represent an interesting therapeutic target in adult src.