pevonedistat and Cell-Transformation--Neoplastic

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

Cerenkov luminescence imaging (CLI) is an emerging imaging technique that combines aspects of both optical and nuclear imaging fields. The ability to fully evaluate the correlation and sensitivity of CLI to PET is critical to progress this technique further for use in high-throughput screening of pharmaceutical compounds. To achieve this milestone, it must first be established that CLI data correlate to PET data in an in vivo preclinical antitumor study. We used MLN4924, a phase 2 oncology therapeutic, which targets and inhibits the NEDD8-activating enzyme pathway involved in the ubiquitin-proteasome system. We compared the efficacious effects of MLN4924 using PET and Cerenkov luminescence image values in the same animals.. Imaging of (18)F-FDG uptake was performed at 5 time points after drug treatment in the subcutaneously implanted diffuse large B-cell lymphoma tumor line OCI-Ly10. Data were acquired with both modalities on the same day, with a 15-min delay between CLI and PET. PET data analysis was performed using percentage injected dose per cubic centimeter of tissue (%ID/cm(3)), average standardized uptake values, and total glycolytic volume. CLI measurements were radiance, radiance per injected dose (radiance/ID), and total radiant volume.. A strong correlation was found between PET total glycolytic volume and CLI total radiant volume (r(2) = 0.99) and various PET and CLI analysis methods, with strong correlations found between PET %ID/cm(3) and CLI radiance (r(2) = 0.83) and CLI radiance/ID (r(2) = 0.82). MLN4924 demonstrated a significant reduction in tumor volume after treatment (volume ratio of treated vs. control, 0.114 at day 29).. The PET and CLI data presented confirm the correlation and dynamic sensitivity of this new imaging modality. CLI provides a preclinical alternative to expensive PET instrumentation. Future high-throughput studies should provide for quicker turnaround and higher cost-to-return benefits in the drug discovery process.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Transformation, Neoplastic; Cyclopentanes; Female; Fluorodeoxyglucose F18; Humans; Luminescent Measurements; Lymphoma; Mice; Molecular Imaging; Positron-Emission Tomography; Pyrimidines