Oerlemans Ruud, Franke Niels E, Assaraf Yehuda G, Cloos Jacqueline, van Zantwijk Ina, Berkers Celia R, Scheffer George L, Debipersad Kabir, Vojtekova Katharina, Lemos Clara, van der Heijden Joost W, Ylstra Bauke, Peters Godefridus J, Kaspers Gertjan L, Dijkmans Ben A C, Scheper Rik J, Jansen Gerrit
Department of Rheumatology, VUMC Institute for Cancer & Immunology, VU University Medical Center, Amsterdam, The Netherlands.
Blood. 2008 Sep 15;112(6):2489-99. doi: 10.1182/blood-2007-08-104950. Epub 2008 Jun 18.
The proteasome inhibitor bortezomib is a novel anticancer drug that has shown promise in the treatment of refractory multiple myeloma. However, its clinical efficacy has been hampered by the emergence of drug-resistance phenomena, the molecular basis of which remains elusive. Toward this end, we here developed high levels (45- to 129-fold) of acquired resistance to bortezomib in human myelomonocytic THP1 cells by exposure to stepwise increasing (2.5-200 nM) concentrations of bortezomib. Study of the molecular mechanism of bortezomib resistance in these cells revealed (1) an Ala49Thr mutation residing in a highly conserved bortezomib-binding pocket in the proteasome beta5-subunit (PSMB5) protein, (2) a dramatic overexpression (up to 60-fold) of PSMB5 protein but not of other proteasome subunits including PSMB6, PSMB7, and PSMA7, (3) high levels of cross-resistance to beta5 subunit-targeted cytotoxic peptides 4A6, MG132, MG262, and ALLN, but not to a broad spectrum of chemotherapeutic drugs, (4) no marked changes in chymotrypsin-like proteasome activity, and (5) restoration of bortezomib sensitivity in bortezomib-resistant cells by siRNA-mediated silencing of PSMB5 gene expression. Collectively, these findings establish a novel mechanism of bortezomib resistance associated with the selective overexpression of a mutant PSMB5 protein.
蛋白酶体抑制剂硼替佐米是一种新型抗癌药物，在难治性多发性骨髓瘤的治疗中显示出前景。然而，耐药现象的出现阻碍了其临床疗效，其分子基础仍不清楚。为此，我们通过逐步增加硼替佐米浓度（2.5 - 200 nM），在人骨髓单核细胞THP1细胞中培养出了高水平（45至129倍）的对硼替佐米的获得性耐药。对这些细胞中硼替佐米耐药分子机制的研究揭示：（1）在蛋白酶体β5亚基（PSMB5）蛋白高度保守的硼替佐米结合口袋中存在Ala49Thr突变；（2）PSMB5蛋白显著过表达（高达60倍），而包括PSMB6、PSMB7和PSMA7在内的其他蛋白酶体亚基未过表达；（3）对靶向β5亚基的细胞毒性肽4A6、MG132、MG262和ALLN有高水平交叉耐药，但对多种化疗药物无交叉耐药；（4）胰凝乳蛋白酶样蛋白酶体活性无明显变化；（5）通过siRNA介导沉默PSMB5基因表达可恢复硼替佐米耐药细胞对硼替佐米的敏感性。总体而言，这些发现确立了一种与突变型PSMB5蛋白选择性过表达相关的硼替佐米耐药新机制。
