title: Usp9x- and Noxa-mediated Mcl-1 downregulation contributes to pemetrexed-induced apoptosis in human non-small-cell lung cancer cells.
abstract: Pemetrexed, a folate antimetabolite, combined with cisplatin is used as a first-line therapy for malignant pleural mesothelioma (MPM) and locally advanced or metastatic non-small-cell lung cancer (NSCLC). Pemetrexed arrests cell cycle by inhibiting three enzymes in purine and pyrimidine synthesis that are necessary for DNA synthesis. Pemetrexed also promotes apoptosis in target cells, but little is known about its mechanism in cancer cells. We have previously shown that pemetrexed can result in endoplasmic reticulum (ER) stress, and it can lead to downstream apoptosis. In this study, we further elucidate this mechanism. Our data show that pemetrexed increases Noxa expression through activating transcription factor 4 (ATF4) and activating transcription factor 3 (ATF3) upregulation. Furthermore, pemetrexed induces apoptosis by activating the Noxa-Usp9x-Mcl-1 pathway. Inhibition of Noxa by small interfering RNA (siRNA) promotes Usp9x (ubiquitin-specific peptidase 9, X-linked) expression. Moreover, downregulation of the deubiquitinase Usp9x by pemetrexed results in downstream reduction of myeloid cell leukemia 1 (Mcl-1) expression. Mechanistically, Noxa upregulation likely reduces the availability of Usp9x to Mcl-1, thereby promoting its ubiquitination and degradation, leading to the apoptosis of neoplastic cells. Thus, our findings demonstrate that Noxa-Usp9x-Mcl-1 axis may contribute to pemetrexed-induced apoptosis in human lung cancer cells.
authors.affiliation: School of Life Sciences, Shandong University, Jinan, China.
authors.forename: J
authors.initials: J
authors.lastname: Yan
authors.affiliation: School of Medicine, Shandong University, Jinan, China.
authors.forename: N
authors.initials: N
authors.lastname: Zhong
authors.affiliation: School of Life Sciences, Shandong University, Jinan, China.
authors.forename: G
authors.initials: G
authors.lastname: Liu
authors.affiliation: Central Hospital of Xinwen Mining Group, Xintai, China.
authors.forename: K
authors.initials: K
authors.lastname: Chen
authors.affiliation: School of Life Sciences, Shandong University, Jinan, China.
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.affiliation: School of Life Sciences, Shandong University, Jinan, China.
authors.forename: L
authors.initials: L
authors.lastname: Su
authors.affiliation: Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Singhal
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology*; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000235:genetics* / Q000378:metabolism; D000068437:Pemetrexed; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D005971:Glutamates; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; C498702:PMAIP1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; C506234:USP9X protein, human; D000068437:Pemetrexed; D006147:Guanine; D043222:Ubiquitin Thiolesterase