Institute of Pathophysiology and Immunology, Centre for Molecular Medicine, Graz, Austria.
Cancer. 2010 Jun 15;116(12):2902-12. doi: 10.1002/cncr.25049.
Fibrosis is a cardinal feature of small intestinal neuroendocrine tumors (SI-NETs) both in local peritumoral tissue and systemic sites (cardiac). 5-HT, a commonly secreted NET amine, is a known inducer of fibrosis, although the mechanistic basis for it and growth factors regulating fibrosis and proliferation in the tumor microenvironment are unclear. We hypothesized that targeting 5-HT(2B) receptors on tumor cells would inhibit SI-NET 5-HT release and, thereby, fibroblast activation in the tumor microenvironment.
We studied the 5-HT(2B) receptor antagonist PRX-08066 in NET cell lines (KRJ-I, H720) and in the coculture system (KRJ-I cells: fibroblastic HEK293 cells) using real time polymerase chain reaction, ELISA, Ki67 immunostaining, and flow cytometry-based caspase 3 assays to assess antiproliferative and profibrotic signaling pathways.
In the 5-HT(2B) expressing SI-NET cell line, KRJ-I, PRX-08066 inhibited proliferation (IC(50) 4.6 x 10(-9)M) and 5-HT secretion (6.9 x 10(-9)M) and decreased ERK1/2 phosphorylation and profibrotic growth factor synthesis and secretion (transforming growth factor beta 1 [TGFbeta1], connective tissue growth factor [CTGF] and fibroblast growth factor [FGF2]). In the KRJ-I:HEK293 coculture system, PRX-08066 significantly decreased 5-HT release (>60%), Ki67 (transcript and immunostaining: 20%-80%), TGFbeta1, CTGF, and FGF2 transcription (20%-50%) in the KRJ-I cell line. 5-HT itself stimulated HEK293 proliferation (25%) and synthesis of TGFbeta1, CTGF and FGF2. PRX-08066 inhibition of KRJ-I function reversed these effects in the coculture system.
Targeting the 5-HT(2B) receptor may be an effective antiproliferative and antifibrotic strategy for SI-NETs because it inhibits tumor microenvironment fibroblasts as well as NET cells. Fibrosis and proliferation appear to be biologically interfaced neuroendocrine neoplasia domains.
纤维化是小肠类癌（SI-NETs）的一个主要特征，无论是在局部肿瘤周围组织还是在全身部位（心脏）。5-HT 是一种常见的神经内分泌瘤分泌胺，是纤维化的已知诱导剂，尽管其机制基础以及调节肿瘤微环境中纤维化和增殖的生长因子尚不清楚。我们假设，针对肿瘤细胞上的 5-HT（2B）受体将抑制 SI-NET 中 5-HT 的释放，从而抑制肿瘤微环境中成纤维细胞的激活。
我们使用实时聚合酶链反应、ELISA、Ki67 免疫染色和基于流式细胞术的 caspase 3 测定，研究了 NET 细胞系（KRJ-I、H720）和共培养系统（KRJ-I 细胞：成纤维细胞 HEK293 细胞）中 5-HT（2B）受体拮抗剂 PRX-08066 的作用。
在表达 5-HT（2B）的 SI-NET 细胞系 KRJ-I 中，PRX-08066 抑制增殖（IC（50）为 4.6×10（-9）M）和 5-HT 分泌（6.9×10（-9）M），并降低 ERK1/2 磷酸化以及促纤维化生长因子的合成和分泌（转化生长因子β 1[ TGFβ1]、结缔组织生长因子[ CTGF]和成纤维细胞生长因子[ FGF2]）。在 KRJ-I：HEK293 共培养系统中，PRX-08066 显著降低 5-HT 释放（>60%）、Ki67（转录和免疫染色：20%-80%）、KRJ-I 细胞系中的 TGFβ1、CTGF 和 FGF2 转录（20%-50%）。5-HT 本身刺激 HEK293 增殖（25%）并合成 TGFβ1、CTGF 和 FGF2。PRX-08066 抑制 KRJ-I 功能在共培养系统中逆转了这些作用。
针对 5-HT（2B）受体可能是一种有效的 SI-NET 抗增殖和抗纤维化策略，因为它抑制肿瘤微环境中的成纤维细胞和神经内分泌瘤细胞。纤维化和增殖似乎是生物学相互作用的神经内分泌肿瘤领域。
