胃腸道基質瘤癌(GIST)被認為起源於胃腸道肌肉層內的卡哈細胞發生癌症轉化，70~80%病人帶有KIT基因增加功能性的突變，此突變使酪胺酸激酶KIT不需與其配體Stem cell factor結合而持續性活化。KIT基因最常發生突變在其基因外顯子11(≈70%)接著是外顯子9(≈10-15%)再來是外顯子13, 14, 17(≈5%)。臨床上使用多型酪胺酸激酶抑制劑(TKIs) imatinib mesylate (IM)、sunitinib malate (SU) 、sorafenib 衍生化合物regorafenib分別為現有第一、二、三線藥物用來治療無法切除或發生轉移的胃腸道基質瘤癌。然而這些藥物有一些限制像是藥物治療一段時間GIST病人疾病會惡化，多數此疾病惡化與KIT基因產生第二個突變有關，且配合藥物治療後疾病無進展發生率的中位數值也不理想，因此，持續發展新穎藥物來治療對現有藥物IM無效及更進化的GIST是很重要的。 本研究利用國家衛生研究院生藥所合成的新穎酪胺酸激酶抑制劑1J373S1對KIT突變GIST細胞生長的抑制作用和其分子機制。1J373S1可抑制表現KIT突變的3株GIST細胞株生長且可以有效抑制其KIT磷酸化，包含: 對IM有效KIT外顯子13突變的GIST882細胞，對IM無效SU有效KIT外顯子11/13雙突變的GIST430，對IM/SU皆無效KIT外顯子11/17雙突變的GIST48。1J373S1不僅可抑制KIT突變的3株GIST細胞株KIT磷酸化且其抑制酪胺酸激酶磷酸化作用也在轉染一系列KIT 突變constructs (包含臨床上常見的KIT第一和第二突變位點)到COS1細胞此in vitro系統證實1J373S1有效抑制KIT不同突變點的KIT磷酸化。有趣的是，現有有效的TKIs通常都使其敏感的GIST細胞株細胞週期停在G0，然而，1J373S1處理的GIST48, GIST430細胞週期停在G2/M。且我們實驗發現1J373S1處理後的GIST48其p53, p21, p16, E2F表現量上升，並觀察到β-galactosidase此老化特徵。未來我們將持續研究1J373S1造成GIST48,GIST430細胞週期停在G2/M的分子機制和探討老化對1J373S1處理後GIST48細胞抑制生長的角色。

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumors of the gastrointestinal tract. GISTs frequently exhibit gain-of-function KIT mutations (70-80% of GISTs), which leads to constitutive activation of the KIT tyrosine kinase receptor in the absence of its binding ligand, stem cell factor (SCF). The most common KIT mutations are located at exon 11 (≈80%) followed by exon 9 (≈10-15%) and exons 13, 14 or 17 (≈5%). Clinically, imatinib mesylate (IM), sunitinib malate (SU), regorafenib, a sorafenib-derived compound, are multi-tyrosine kinase inhibitors (TKIs), are the current standard treatments for patients with unresectable and/or metastatic GIST. However, those drugs have limitations: experience disease progression, associated with the acquisition of secondary mutations, and unsatisfactory median progression-free survival. Therefore, it is important to explore much suitable compound for advanced gastrointestinal stromal tumor. In this study, we aim to evaluate the growth inhibitory effects and molecular mechanisms of a novel TKI from the Institute of Biotechnology and Pharmacology, National Health Research Institutes, the 1J373S1 that was initially designed as a FLT-3 inhibitor, on IM and/or SU resistance GIST cells. The 1J373S1 shows activity on inhibiting the KIT phosphorylation and proliferation of KIT mutated GIST cells, including IM-sensitive exon13 mutated GIST882, IM-resistant/sunitinib-sensitive exon 11/13 doubly mutated GIST430, IM/SU-resistant/nilotinib-sensitive exon 11/17 doubly mutated GIST48. The superiority of 1J373S1 on inhibiting the activation of KIT mutant proteins was confirmed in an in vitro cell-based platform consisting of a series of COS-1 cells expressing various KIT cDNA constructs encoding common primary ± secondary mutations observed in clinical GISTs. Interestingly, TKI treatment usually resulted in G0 arrest in sensitive cell lines (SU for GIST 430 and nilotinib for GIST48), however, 1J373S1 treatment resulted in G2/M-arrest in both GIST48 and GIST430 cells and also induces GIST cell lines apoptosis. In addition, we have explored that 1J373S1 treatment can induce senescent signals: p53, p21, p16, E2F, β-galactosidase signal up-regulation of exon 11/17 doubly mutated GIST48. In future work, we shall explore the molecular mechanisms of growth inhibition GIST cells further more.

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