Chandra J, Niemer I, Gilbreath J, Kliche K O, Andreeff M, Freireich E J, Keating M, McConkey D J
Departments of Cell Biology and Hematology, The University of Texas, M.D. Anderson Cancer Center, Houston, TX, USA.
Blood. 1998 Dec 1;92(11):4220-9.
Our previous work showed that the nuclear scaffold (NS) protease is required for apoptosis of both thymocytes and chronic lymphocytic leukemic (CLL) lymphocytes. Because partial sequencing of one of the subunits of the NS protease revealed homology to the proteasome, we tested the effects of classical proteasome inhibitors on apoptosis in CLL cells. Here we report that proteasome inhibition caused high levels of DNA fragmentation in all patients analyzed, including those resistant to glucocorticoids or nucleoside analogs, in vitro. Proteasome inhibitor-induced DNA fragmentation was associated with activation of caspase/ICE family cysteine protease(s) and was blocked by the caspase antagonist, zVADfmk. Analysis of the biochemical mechanisms involved showed that proteasome inhibition resulted in mitochondrial dysregulation leading to the release of cytochrome c and a drop in mitochondrial transmembrane potential (triangle upPsi). These changes were associated with inhibition of NFkappaB, a proteasome-regulated transcription factor that has been implicated in the suppression of apoptosis in other systems. Together, our results suggest that drugs that target the proteasome might be capable of bypassing resistance to conventional chemotherapy in CLL.
我们之前的研究表明，核支架（NS）蛋白酶是胸腺细胞和慢性淋巴细胞白血病（CLL）淋巴细胞凋亡所必需的。由于NS蛋白酶其中一个亚基的部分测序显示与蛋白酶体具有同源性，我们测试了经典蛋白酶体抑制剂对CLL细胞凋亡的影响。在此我们报告，蛋白酶体抑制在体外导致所有分析患者（包括那些对糖皮质激素或核苷类似物耐药的患者）出现高水平的DNA片段化。蛋白酶体抑制剂诱导的DNA片段化与半胱天冬酶/ICE家族半胱氨酸蛋白酶的激活相关，并被半胱天冬酶拮抗剂zVADfmk阻断。对所涉及生化机制的分析表明，蛋白酶体抑制导致线粒体失调，进而导致细胞色素c释放以及线粒体跨膜电位（△Ψ）下降。这些变化与NFκB的抑制相关，NFκB是一种蛋白酶体调节的转录因子，在其他系统中参与细胞凋亡的抑制。总之，我们的结果表明，靶向蛋白酶体的药物可能能够绕过CLL对传统化疗的耐药性。
