The Nedd8-Activating Enzyme Inhibitor MLN4924 Induces Autophagy and Apoptosis to Suppress Liver Cancer Cell Growth

Abstract

Posttranslational neddylation of cullins in the Cullin-Ring E3 ligase (CRL) complexes is needed for proteolytic degradation of CRL substrates, whose accumulation induces cell-cycle arrest, apoptosis, and senescence. The Nedd8-activating enzyme (NAE) is critical for neddylation of CRL complexes and their growth-promoting function. Recently, the anticancer small molecule MLN4924 currently in phase I trials was determined to be an inhibitor of NAE that blocks cullin neddylation and inactivates CRL, triggering an accumulation of CRL substrates that trigger cell-cycle arrest, apoptosis, and senescence in cancer cells. Here, we report that MLN4924 also triggers autophagy in response to CRL inactivation and that this effect is important for the ability of MLN4924 to suppress the outgrowth of liver cancer cells in vitro and in vivo. MLN4924-induced autophagy was attributed partially to inhibition of mTOR activity, due to accumulation of the mTOR inhibitory protein Deptor, as well as to induction of reactive oxygen species stress. Inhibiting autophagy enhanced MLN4924-induced apoptosis, suggesting that autophagy is a survival signal triggered in response to CRL inactivation. In a xenograft model of human liver cancer, MLN4924 was well-tolerated and displayed a significant antitumor effect characterized by CRL inactivation and induction of autophagy and apoptosis in liver cancer cells. Together, our findings support the clinical investigation of MLN4924 for liver cancer treatment and provide a preclinical proof-of-concept for combination therapy with an autophagy inhibitor to enhance therapeutic efficacy. Cancer Res; 72(13); 3360-71. Ó2012 AACR.

Huaier polysaccharide induces apoptosis in hepatocellular carcinoma cells through p38 MAPK

“…However, the present findings are contradictory to these observations, as increased expression of p53 was observed in HepG2 cells expressing wild-type and functional p53, and in Huh7 cells carrying the mutated and inactivated p53 gene (23). The results of the current study suggested that HP could induce apoptosis in HCC cells regardless of the p53 status.…”

Targeting cullin-RING ligases for cancer treatment: rationales, advances and therapeutic implications

“…Stabilization/induction of REDD1 was induced upon MLN4924 treatment in multiple myeloma and siRNA-mediated knockdown was shown to alleviate the cytotoxicity of MLN4924 (Gu et al 2014). Furthermore, MLN4924-mediated mTOR inhibition was shown to trigger pro-survival autophagy in liver cancer cells and simultaneous inhibition of autophagic responses enhances cytotoxic effects (Luo et al 2012). This is consistent with a previous report with knockdown of RING finger protein Rbx1 in the CRL complex, in which protective autophagic responses were also induced .…”

The covalent modifier Nedd8 is critical for the activation of Smurf1 ubiquitin ligase in tumorigenesis

“…In contrast to the tumourpromoting role of Smurf1, Smurf2 has been suggested to function as a tumour suppressor gene since ablation of Smurf2 in mice resulted in increased susceptibility to various types of cancers in aged mice 61 . We noted that the NAE inhibitor MLN4924 has been recently identified as a novel approach to the treatment of acute myeloid leukaemia, head and neck cancer and liver cancer [62][63][64] . In addition, MLN4924 was demonstrated to inhibit tumour growth in lung cancer xenografts 65 .…”