cytochrome-c-t and pevonedistat

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.

Topics: Animals; Antineoplastic Agents; Antioxidants; Apoptosis Inducing Factor; Apoptosis Regulatory Proteins; Cell Line, Tumor; Cullin Proteins; Cyclin-Dependent Kinase Inhibitor p27; Cyclopentanes; Cytochromes c; Embryo, Nonmammalian; F-Box Proteins; G2 Phase Cell Cycle Checkpoints; Gene Expression Regulation, Neoplastic; Humans; Intracellular Signaling Peptides and Proteins; Mitochondrial Proteins; Pyrimidines; Reactive Oxygen Species; RNA, Small Interfering; S-Phase Kinase-Associated Proteins; Signal Transduction; Stomach Neoplasms; Xenograft Model Antitumor Assays; Zebrafish