Proteasome-based mechanisms of intrinsic and acquired bortezomib resistance in non-small cell lung cancer

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• 作者：Leonie H.A.M. de Wilt^a ; Gerrit Jansen^b ; Yehuda G. Assaraf^c ; Johan van Meerloo^d ; Jacqueline Cloos^d ; Aaron D. Schimmer^e ; Elena T. Chan^f ; Christopher J. Kirk^f ; Godefridus J. Peters^a ; Frank A.E. Kruyt^g ; ^{f.a.e.kruyt@umcg.nl}
• 关键词：Bortezomib ; Resistance ; Lung cancer ; Mutation ; ¦Â5 proteasome subunit ; Proteasome inhibitors
• 刊名：Biochemical Pharmacology
• 出版年：2012
• 出版时间：15 January 2012
• 年：2012
• 卷：83
• 期：2
• 页码：207-217
• 全文大小：1243 K

文摘

The proteasome inhibitor bortezomib, registered for Multiple Myeloma treatment, is currently explored for activity in solid tumors including non-small cell lung cancer (NSCLC). Here we studied the proteasome-based mechanisms underlying intrinsic and acquired bortezomib resistance in NSCLC cells. Various NSCLC cell lines displayed differential intrinsic sensitivities to bortezomib. High basal chymotrypsin- and caspase-like proteasome activities correlated with bortezomib resistance in these cells. Next, via stepwise selection, acquired bortezomib resistant cells were obtained with 8-70-fold increased resistance. Cross-resistance was found to proteasome inhibitors specifically targeting ¦Â-subunits, but not to the novel ¦Á-subunit-specific proteasome inhibitor (5AHQ). Consistently, bortezomib-resistant cells required higher bortezomib concentrations to induce G2/M arrest and apoptosis. Interestingly, bortezomib concentration-dependent caspase cleavage, Mcl-1 and NOXA accumulation remained intact in resistant H460 and SW1573 cells, while A549 resistant cells displayed different expression profiles suggesting additional and more protein specific adaptations. Furthermore, bortezomib-resistant cells exhibited increased levels of both constitutive and immuno-¦Â-subunits. Sequence analysis of the bortezomib-binding pocket in the ¦Â5-subunit revealed Ala49Thr, Met45Val and Cys52Phe substitutions that were not previously described in solid tumors. Bortezomib-resistant cells displayed reduced catalytic proteasome activities and required higher bortezomib concentrations to achieve comparable inhibition of proteasome activity. Taken together, these findings establish that high basal levels of proteasome activity correlate with intrinsic bortezomib resistance. Furthermore, acquired bortezomib resistance in NSCLC is associated with proteasome subunit overexpression and emergence of mutant ¦Â5-subunits that likely compromise bortezomib binding. ¦Á-Subunit-specific proteasome inhibitors, however, can efficiently bypass this resistance modality.