Zhang Q, etal., Cell Death Dis. 2015 Aug 27;6:e1867. doi: 10.1038/cddis.2015.215.
The tumor-suppressor gene cyclin-dependent kinase inhibitor 1B (P27) is downregulated in gastric cancer cells mainly through proteolytic degradation mediated by the SKP-Cullin1-F-Box (SCF) complex. But the correlation between its downregulation and gastric cancer prognosis still remains indefinite.
MLN4924, an anti-tumor agent, which suppresses the SCF complex by inhibiting Cullin1 neddylation, emerges as a promising tool to elucidate its functions in gastric cancer cells. In this study, MLN4924 induced significant growth inhibition of gastric cancer cells in a dose-dependent manner, along with the simultaneous accumulation of P27 and cell cycle abnormalities such as G2/M arrest. Importantly, we found that P27 silencing in MLN4924-treated cells resulted in an enhancement of growth inhibition both in vitro and in vivo. Mechanism analysis revealed the antagonism effects of antioxidants to this excess apoptosis, suggesting reactive oxygen species (ROS) overproduction especially in the mitochondria was the principal cause of the augmentation. Moreover, the robust ROS attacked the mitochondria to initiate collapse of the mitochondrial membrane permeability and the exportation of apoptosis-inducing factor (AIF), IAP-binding mitochondrial protein (SMAC/DIABLO) and cytochrome c. Finally, we also found that P27 knockdown affected the expression profile of several critical BH3 family members to amplify the mitochondrial dysfunction and apoptosis. In summary, our findings unveiled a protective role of P27 by maintaining mitochondrial membrane permeability in MLN4924-treated gastric cancer cells, and therefore highlighted the potential combination of MLN4924 with P27 inhibition to improve its therapeutic efficacy.
Neel NF, etal., Mol Cancer Ther. 2014 Jan;13(1):122-33. doi: 10.1158/1535-7163.MCT-12-1232. Epub 2013 Nov 12.
The high prevalence of KRAS mutations and importance of the RalGEF-Ral pathway downstream of activated K-ras in pancreatic ductal adenocarcinoma (PDAC) emphasize the importance of identifying novel methods by which to therapeutically target these pathways. It was recently demonstrated that phosphory
lation of RalA S194 by Aurora A kinase (AAK) is critical for PDAC tumorigenesis. We sought to evaluate the AAK-selective inhibitor MLN8237 as a potential indirect anti-RalA-targeted therapy for PDAC. We used a site-specific phospho-S194 RalA antibody and determined that RalA S194 phosphorylation levels were elevated in a subset of PDAC cell lines and human tumors relative to unmatched normal controls. Effects of MLN8237 on anchorage-independent growth in PDAC cell lines and growth of patient-derived xenografts (PDX) were variable, with a subset of cell lines and PDX showing sensitivity. Surprisingly, RalA S194 phosphorylation levels in PDAC cell lines or PDX tumors did not correlate with MLN8237 responsiveness. However, we identified Ki67 as a possible early predictive biomarker for response to MLN8237 in PDAC. These results indicate that MLN8237 treatment may be effective for a subset of patients with PDAC independent of RalA S194 phosphorylation. Ki67 may be an effective pharmacodynamic biomarker to identify response early in the course of treatment.
Li Y, etal., Thyroid. 2018 Sep 18. doi: 10.1089/thy.2018.0183.
BACKGROUND: c-Myc is overexpressed in different types of cancer including thyroid cancer, and is considered undruggable over the decades. There is evidence showing that MLN8237, a kind of Aurora A kinase (AURKA) inhibitor, destabilizes c-Myc proteins
in liver cancer cells through disrupting c-Myc/AURKA complex. However, the role of MLN8237 in thyroid cancer remains largely unclear. Our aims were to test therapeutic potential of MLN8237 in thyroid cancer, and to analyze determinant factors affecting the response of thyroid cancer cells to MLN8237 and clarify corresponding mechanism. METHODS: We evaluated phenotypic effects of MLN8237 in thyroid cancer cells through a series of in vitro and in vivo experiments, and explore the mechanism of c-Myc affecting MLN8237 response by using western blot, ubiquitination and cycloheximide (CHX)-chase assays. RESULTS: Our data showed that the levels of c-Myc proteins were strongly associated with MLN8237 cellular response in thyroid cancer cells. Only the cells with high c-Myc expression exhibited growth inhibition upon MLN8237 treatment; however, MLN8237 almost did not affect the growth of those with low c-Myc expression. Mechanistically, MLN8237 dramatically promoted proteasomal degradation of c-Myc proteins through disrupting c-Myc/AURKA complex in the cells with high c-Myc expression. A similar antitumor activity of MLN8237 was also found in xenograft tumor models. CONCLUSIONS: Our data demonstrate that c-Myc is a major determinant for MLN8237 responsiveness in thyroid cancer cells. Thus, indirectly targeting c-Myc by MLN8237 may be an effective strategy for thyroid cancer overexpressing c-Myc.
Knorr KL, etal., Cell Death Differ. 2015 Dec;22(12):2133-42. doi: 10.1038/cdd.2015.74. Epub 2015 Jun 5.
MLN4924 (pevonedistat), an inhibitor of the Nedd8 activating enzyme (NAE), has exhibited promising clinical activity in acute myelogenous leukemia (AML). Here we demonstrate that MLN4924 induces apoptosis in AML cell lines a
nd clinical samples via a mechanism distinct from those observed in other malignancies. Inactivation of E3 cullin ring ligases (CRLs) through NAE inhibition causes accumulation of the CRL substrate c-Myc, which transactivates the PMAIP1 gene encoding Noxa, leading to increased Noxa protein, Bax and Bak activation, and subsequent apoptotic changes. Importantly, c-Myc knockdown diminishes Noxa induction; and Noxa siRNA diminishes MLN4924-induced killing. Because Noxa also neutralizes Mcl-1, an anti-apoptotic Bcl-2 paralog often upregulated in resistant AML, further experiments have examined the effect of combining MLN4924 with BH3 mimetics that target other anti-apoptotic proteins. In combination with ABT-199 or ABT-263 (navitoclax), MLN4924 exerts a synergistic cytotoxic effect. Collectively, these results provide new insight into MLN4924-induced engagement of the apoptotic machinery that could help guide further exploration of MLN4924 for AML.
