Natarajan Valliyammai, Bandapalli Obul R, Rajkumar Thangarajan, Sagar Tenali Gnana, Karunakaran Nirmala
Departments of *Molecular Oncology ‡Medical Oncology, Cancer Institute (WIA), Chennai, Tamilnadu, India †Department of Pediatric Hematology, Oncology and Immunology, University of Heidelberg, Heidelberg, Germany.
J Pediatr Hematol Oncol. 2015 Jan;37(1):e23-30. doi: 10.1097/MPH.0000000000000290.
The NOTCH1 signaling pathway is essential for hematopoiesis and a critical regulatory step for T-cell proliferation and maturation. The E3 ubiquitin ligase FBXW7 controls NOTCH1 protein stability. Mutations in NOTCH1/FBXW7 activate NOTCH signaling and are of prognostic significance in patients with T-cell acute lymphoblastic leukemia (T-ALL). In this study we analyzed NOTCH1 and FBXW7 mutations in 50 South Indian T-ALL patients treated by a modified ALL BFM 95 regimen. The hot spot exons (HD-N, HD-C, TAD, and PEST) of NOTCH1 and exons 9 of the 10 of FBXW7 were polymerase chain reaction amplified and sequenced. In total, 20 of the 50 (40%) T-ALL patients revealed heterozygous mutations in the NOTCH1 domains, and a predominance of missense mutations in HD-N (70%) and PEST (15%) domains. FBXW7 mutations were detected in 5 of the 50 (10%) T-ALL patients. T-ALL patients with NOTCH1/FBXW7 mutations expressed higher protein level of NOTCH1 compared with patients without NOTCH1/FBXW7 mutations. Six of the mutations detected in NOTCH1 were not reported previously. When tested in a Dual Luciferase Renilla reporter assay some of these conferred increased NOTCH activity, suggesting that these are activating mutations. Importantly, 13 of the 20 (65%) NOTCH1/FBXW7-mutated T-ALL patients showed a good prednisone response (P=0.01) and a better clinical outcome compared with NOTCH1/FBXW7 nonmutated patients (P=0.03). These data suggest that NOTCH1/FBXW7 mutations are present in T-ALL patients from Southern India and may be useful biomarkers to predict prognosis in T-ALL.
NOTCH1信号通路对造血作用至关重要，是T细胞增殖和成熟的关键调控步骤。E3泛素连接酶FBXW7控制NOTCH1蛋白稳定性。NOTCH1/FBXW7中的突变激活NOTCH信号，对T细胞急性淋巴细胞白血病（T-ALL）患者具有预后意义。在本研究中，我们分析了采用改良ALL BFM 95方案治疗的50例南印度T-ALL患者的NOTCH1和FBXW7突变情况。对NOTCH1的热点外显子（HD-N、HD-C、TAD和PEST）以及FBXW7的10个外显子中的第9个外显子进行聚合酶链反应扩增和测序。总共，50例（40%）T-ALL患者中有20例在NOTCH1结构域中发现杂合突变，且错义突变在HD-N结构域（70%）和PEST结构域（15%）中占优势。50例（10%）T-ALL患者中有5例检测到FBXW7突变。与无NOTCH1/FBXW7突变的患者相比，有NOTCH1/FBXW7突变的T-ALL患者NOTCH1蛋白水平表达更高。在NOTCH1中检测到的6种突变以前未被报道。当在双荧光素酶海肾荧光素酶报告基因检测中进行测试时，其中一些突变导致NOTCH活性增加，表明这些是激活突变。重要的是，20例（65%）NOTCH1/FBXW7突变的T-ALL患者中有13例对泼尼松反应良好（P = 0.01），与NOTCH1/FBXW7未突变的患者相比临床结局更好（P = 0.03）。这些数据表明，NOTCH1/FBXW7突变存在于来自印度南部的T-ALL患者中，可能是预测T-ALL预后的有用生物标志物。
