Yang Xinping, Liu Liyun, Sternberg David, Tang Liren, Galinsky Ilene, DeAngelo Daniel, Stone Richard
Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
Cancer Res. 2005 Aug 15;65(16):7338-47. doi: 10.1158/0008-5472.CAN-04-2263.
Internal tandem duplication (ITD) mutations in the FLT3 tyrosine kinase have been detected in approximately 20% of acute myeloid leukemia (AML) patients. Patients harboring FLT3/ITD mutations have a relatively poor prognosis. FLT3/ITD results in constitutive autophosphorylation of the receptor and factor-independent survival. Previous studies have shown that FLT3/ITD activates the signal transducers and activators of transcription 5 (STAT5), p42/p44 mitogen-activated protein kinase [MAPK; extracellular signal-regulated kinase (ERK) 1/2], and phosphatidylinositol 3-kinase/Akt pathways. We herein provide biochemical and biological evidence that ribosomal S6 kinase 1 (RSK1) and protein kinase A (PKA) are the two principal kinases that mediate the antiapoptotic function of FLT3/ITD via phosphorylation of BAD at Ser112. Inhibiting both MAPK kinase (MEK)/ERK and PKA pathways by a combination of U0126 (10 micromol/L) and H-89 (5 micromol/L) reduced most of BAD phosphorylation at Ser112 and induced apoptosis to a level comparable with that induced by FLT3 inhibitor AG1296 (5 micromol/L) in BaF3/FLT3/ITD cells. RNA interference of RSK1 or PKA catalytic subunit reduced BAD phosphorylation and induced apoptosis. The MEK inhibitor U0126 and/or the PKA inhibitor H-89 greatly enhanced the efficacy of the FLT3 inhibitor AG1296, suggesting that combining FLT3/ITD downstream pathway inhibition with FLT3 inhibitors may be a viable therapeutic strategy for AML caused by a FLT3/ITD mutation.
在大约20%的急性髓系白血病(AML)患者中检测到了FLT3酪氨酸激酶的内部串联重复(ITD)突变。携带FLT3/ITD突变的患者预后相对较差。FLT3/ITD导致受体的组成型自磷酸化和不依赖因子的存活。先前的研究表明,FLT3/ITD激活信号转导和转录激活因子5(STAT5)、p42/p44丝裂原活化蛋白激酶[MAPK;细胞外信号调节激酶(ERK)1/2]以及磷脂酰肌醇3激酶/Akt通路。我们在此提供生化和生物学证据,表明核糖体S6激酶1(RSK1)和蛋白激酶A(PKA)是通过在Ser112位点磷酸化BAD来介导FLT3/ITD抗凋亡功能的两种主要激酶。在BaF3/FLT3/ITD细胞中,联合使用U0126(10微摩尔/升)和H - 89(5微摩尔/升)抑制MAPK激酶(MEK)/ERK和PKA通路,可降低Ser112位点大部分BAD的磷酸化水平,并诱导细胞凋亡至与FLT3抑制剂AG1296(5微摩尔/升)诱导的水平相当。对RSK1或PKA催化亚基进行RNA干扰可降低BAD磷酸化并诱导细胞凋亡。MEK抑制剂U0126和/或PKA抑制剂H - 89大大增强了FLT3抑制剂AG1296的疗效,这表明将FLT3/ITD下游通路抑制与FLT3抑制剂联合使用可能是治疗由FLT3/ITD突变引起的AML的一种可行治疗策略。