Abstract
Upregulation of protein neddylation occurs in numerous types of human cancer, including liver cancer. MLN4924, a potent neddylation-inhibiting pharmacological agent, demonstrates anticancer ability in numerous cancers. However, the sensitivity of MLN4924 in liver cancer remains unsatisfactory due to factors causing resistance. RT-qPCR and western blotting were utilized to assess the mRNA and protein levels of genes, respectively. Cell Counting Kit-8 assay and colony formation assays were employed to assess cell viability and proliferation. The pathway of protein degradation and stability were determined by western blotting after treatment with MG132 and cycloheximide. An immunoprecipitation assay was utilized to detect the ubiquitination of protein. An in vitro ubiquitination assay was used to determine the ubiquitin linkage. To the best of our knowledge, the present study was the first to demonstrate that NF-κB inhibitor α (IκBα) downregulation and subsequent inflammation in response to MLN4924 limited the antitumor potential of MLN4924. Ectopic expression of IκBα enhanced the antitumor potential of MLN4924 in liver cancer cells. Moreover, the results of the present study demonstrated that MLN4924 decreased IκBα via promoting the K48 linkage of ubiquitin to IκBα. Mechanistic studies demonstrated that MLN4924 enhanced the protein stability of β-transducin repeat-containing protein (β-TrCP), promoting the ubiquitination of IκBα, which led to the ubiquitin-mediated degradation of IκBα. In addition, the results of the present study also demonstrated that β-TrCP knockdown markedly inhibited MLN4924 from suppressing the growth of liver cancer cells, via attenuating MLN4924-mediated IκBα downregulation and inflammation. Collectively, these results indicated that the β-TrCP/IκBα/inflammation pathway may act as a novel resistance factor of MLN4924, and targeting β-TrCP may be beneficial for the treatment of liver cancer.
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