Discrepant NOXA (PMAIP1) transcript and NOXA protein levels: a potential Achilles’ heel in mantle cell lymphoma

Abstract

Mantle cell lymphoma (MCL) is an aggressive lymphoid neoplasm with transient response to conventional chemotherapy. We here investigated the role of the Bcl-2 homology domain 3-only protein NOXA for life–death decision in MCL. Surprisingly, NOXA (PMAIP1) mRNA and NOXA protein levels were extremely discrepant in MCL cells: NOXA mRNA was found to be highly expressed whereas NOXA protein levels were low. Chronic active B-cell receptor signaling and to a minor degree cyclin D1 overexpression contributed to high NOXA mRNA expression levels in MCL cells. The phoshatidyl-inositol-3 kinase/AKT/mammalian target of rapamycin pathway was identified as the major downstream signaling pathway involved in the maintenance of NOXA gene expression. Interestingly, MCL cells adapt to this constitutive pro-apoptotic signal by extensive ubiquitination and rapid proteasomal degradation of NOXA protein (T½∼15–30 min). In addition to the proteasome inhibitor Bortezomib, we identified the neddylation inhibitor MLN4924 and the fatty acid synthase inhibitor Orlistat as potent inducers of NOXA protein expression leading to apoptosis in MCL. All inhibitors targeted NOXA protein turnover. In contrast to Bortezomib, MLN4924 and Orlistat interfered with the ubiquitination process of NOXA protein thereby offering new strategies to kill Bortezomib-resistant MCL cells. Our data, therefore, highlight a critical role of NOXA in the balance between life and death in MCL. The discrepancy between NOXA transcript and protein levels is essential for sensitivity of MCL to ubiquitin-proteasome system inhibitors and could therefore provide a druggable Achilles' heel of MCL cells.

Neddylation Inhibition Activates the Extrinsic Apoptosis Pathway through ATF4–CHOP–DR5 Axis in Human Esophageal Cancer Cells

“…MLN4924 was reported to induce Noxa expression and intrinsic apoptosis in several cancers, but the underlying mechanism for the induction of Noxa upon MLN4924 treatment remains largely unknown (3,12,22,46). In the present study, we found that, in ESCC cells, MLN4924-induced Noxa is dependent on ATF4: first, MLN4924 blocks ATF4 turnover and induces its accumulation; second, the downregulation of ATF4 via siRNA silencing completely blocked the induction of Noxa.…”

“…BH3-only protein Noxa is a key mediator of intrinsic apoptosis (12,(46)(47)(48). MLN4924 was reported to induce Noxa expression and intrinsic apoptosis in several cancers, but the underlying mechanism for the induction of Noxa upon MLN4924 treatment remains largely unknown (3,12,22,46).…”

Targeting protein neddylation with an NEDD8-activating enzyme inhibitor MLN4924 induced apoptosis or senescence in human lymphoma cells

“…20,27,28 Encouragingly, lymphoma cells, compared to other types of cancer cells, exhibit the highest sensitivity to MLN4924. 9 Moreover, normal lymphocytes including T/B cells and peripheral blood mononuclear cells (PBMCs) are resistant to MLN4924 treatment, while lymphoma cells are shown to be very sensitive to this anticancer agent.…”

“…20 Dengler et al reported that MLN4924 killed mantle cell lymphoma (MCL) cells by stabilizing pro-apoptotic protein NOXA. 27 Interestingly, Godbersen et al found that MLN4924 thwarted microenvironment-driven NF-kB activation and induces apoptosis in chronic lymphocytic leukemia B cells. 28 These collective findings demonstrate that the neddylation pathway is required for the growth and survival of lymphoma cells.…”

Influence of fatty acid synthase inhibitor orlistat on the DNA repair enzyme O6-methylguanine-DNA methyltransferase in human normal or malignant cells in vitro

“…According to this mechanism, one would expect that FASN inhibition could be of value not only as a device for attaining antitumor effects, but also as an anticancer treatment modality. In addition, orlistat has been found to augment pro-apoptotic NOXA protein (8), thus reinforcing its possible cancer protective activity. However, preclinical studies performed on rats exposed to predisposing factors for colon cancer (i.e., receiving high fat diet alone or combined with the carcinogen compound methyl hydrazine), showed that long-term treatment with orlistat lead to severe crypt alterations of colonic mucosa, that are considered colon cancer biomarkers (9,10).…”