pevonedistat and carfilzomib

Retinoblastoma protein (Rb) is a tumor suppressor that binds and represses E2F transcription factors. In cervical cancer cells, human papilloma virus (HPV) protein E7 binds to Rb, releasing it from E2F to promote cell cycle progression, and inducing ubiquitination of Rb. E7-mediated proteasomal degradation of Rb requires action by another protease, calpain, which cleaves Rb after Lys 810. However, it is not clear why cleavage is required for Rb degradation. Here, we report that the proteasome cannot initiate degradation efficiently on full-length Rb. Calpain cleavage exposes a region that is recognized by the proteasome, leading to rapid proteolysis of Rb. These findings identify a mechanism for regulating protein stability by controlling initiation and provide a better understanding of the molecular mechanism underlying transformation by HPV.

Topics: Acrylates; Calpain; Cell Cycle; Cell Transformation, Neoplastic; Cyclopentanes; E2F Transcription Factors; Female; Gene Expression Regulation, Neoplastic; HEK293 Cells; Human papillomavirus 16; Humans; NEDD8 Protein; Oligopeptides; Papillomavirus E7 Proteins; Proteasome Endopeptidase Complex; Protein Stability; Pyrimidines; Recombinant Proteins; Retinoblastoma Binding Proteins; Ubiquitin-Protein Ligases; Ubiquitination; Uterine Cervical Neoplasms

The NEDD8-activating enzyme (NAE) inhibitor MLN4924 inhibits cullin-RING ubiquitin ligase complexes including the SKP1-cullin-F-box E3 ligase βTrCP. MLN4924 therefore inhibits also the βTrCP-dependent activation of the classical and the alternative NFĸB pathway. In this work, we found that a subgroup of multiple myeloma cell lines (e.g., RPMI-8226, MM.1S, KMS-12BM) and about half of the primary myeloma samples tested are sensitized to TNF-induced cell death by MLN4924. This correlated with MLN4924-mediated inhibition of TNF-induced activation of the classical NFκB pathway and reduced the efficacy of TNF-induced TNFR1 signaling complex formation. Interestingly, binding studies revealed a straightforward correlation between cell surface TNFR1 expression in multiple myeloma cell lines and their sensitivity for MLN4924/TNF-induced cell death. The cell surface expression levels of TNFR1 in the investigated MM cell lines largely correlated with TNFR1 mRNA expression. This suggests that the variable levels of cell surface expression of TNFR1 in myeloma cell lines are decisive for TNF/MLN4924 sensitivity. Indeed, introduction of TNFR1 into TNFR1-negative TNF/MLN4924-resistant KMS-11BM cells, was sufficient to sensitize this cell line for TNF/MLN4924-induced cell death. Thus, MLN4924 might be especially effective in myeloma patients with TNFR1

Topics: Adult; Aged; Apoptosis; Bortezomib; Cell Line, Tumor; Cell Survival; Cyclopentanes; Female; Humans; Male; Middle Aged; Multiple Myeloma; Necrosis; NF-kappa B; Oligopeptides; Pyrimidines; Receptors, Tumor Necrosis Factor, Type I; Signal Transduction; Tumor Necrosis Factor-alpha; Ubiquitin-Activating Enzymes