Ceccon Monica, Merlo Maria Elena Boggio, Mologni Luca, Poggio Teresa, Varesio Lydia M, Menotti Matteo, Bombelli Silvia, Rigolio Roberta, Manazza Andrea D, Di Giacomo Filomena, Ambrogio Chiara, Giudici Giovanni, Casati Cesare, Mastini Cristina, Compagno Mara, Turner Suzanne D, Gambacorti-Passerini Carlo, Chiarle Roberto, Voena Claudia
Department of Health Science, University of Milano-Bicocca, Monza, Italy.
Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.
Oncogene. 2016 Jul 21;35(29):3854-3865. doi: 10.1038/onc.2015.456. Epub 2015 Dec 14.
Most of the anaplastic large-cell lymphoma (ALCL) cases carry the t(2;5; p23;q35) that produces the fusion protein NPM-ALK (nucleophosmin-anaplastic lymphoma kinase). NPM-ALK-deregulated kinase activity drives several pathways that support malignant transformation of lymphoma cells. We found that in ALK-rearranged ALCL cell lines, NPM-ALK was distributed in equal amounts between the cytoplasm and the nucleus. Only the cytoplasmic portion was catalytically active in both cell lines and primary ALCL, whereas the nuclear portion was inactive because of heterodimerization with NPM1. Thus, about 50% of the NPM-ALK is not active and sequestered as NPM-ALK/NPM1 heterodimers in the nucleus. Overexpression or relocalization of NPM-ALK to the cytoplasm by NPM genetic knockout or knockdown caused ERK1/2 (extracellular signal-regulated protein kinases 1 and 2) increased phosphorylation and cell death through the engagement of an ATM/Chk2- and γH2AX (phosphorylated H2A histone family member X)-mediated DNA-damage response. Remarkably, human NPM-ALK-amplified cell lines resistant to ALK tyrosine kinase inhibitors (TKIs) underwent apoptosis upon drug withdrawal as a consequence of ERK1/2 hyperactivation. Altogether, these findings indicate that an excess of NPM-ALK activation and signaling induces apoptosis via oncogenic stress responses. A 'drug holiday' where the ALK TKI treatment is suspended could represent a therapeutic option in cells that become resistant by NPM-ALK amplification.
大多数间变性大细胞淋巴瘤（ALCL）病例携带t(2;5; p23;q35)，该基因会产生融合蛋白NPM-ALK（核磷蛋白-间变性淋巴瘤激酶）。NPM-ALK失调的激酶活性驱动了多种支持淋巴瘤细胞恶性转化的信号通路。我们发现，在ALK重排的ALCL细胞系中，NPM-ALK在细胞质和细胞核中分布等量。在细胞系和原发性ALCL中，只有细胞质部分具有催化活性，而细胞核部分由于与NPM1异源二聚化而无活性。因此，约50%的NPM-ALK不具有活性，并以NPM-ALK/NPM1异源二聚体的形式被隔离在细胞核中。通过NPM基因敲除或敲低使NPM-ALK过表达或重新定位到细胞质中，会导致细胞外信号调节蛋白激酶1和2（ERK1/2）磷酸化增加，并通过ATM/Chk2和γH2AX（磷酸化的H2A组蛋白家族成员X）介导的DNA损伤反应引发细胞死亡。值得注意的是，对ALK酪氨酸激酶抑制剂（TKIs）耐药的人NPM-ALK扩增细胞系在停药后会因ERK1/2过度激活而发生凋亡。总之，这些发现表明，过量的NPM-ALK激活和信号传导通过致癌应激反应诱导细胞凋亡。对于因NPM-ALK扩增而产生耐药性的细胞，暂停ALK TKI治疗的“药物假期”可能是一种治疗选择。
