Investigation du système ubiquitine protéasome et découverte de nouvelles cibles thérapeutiques anti-cancer surpassant la résistance acquise au bortézomib
Multiple Myeloma (MM) is the second most common human blood cancer. The proteasome, a multi-protein complex responsible for the degradation of ubiquitinated proteins, has been established as a major target for the treatment of MM cancer patients. Although patient survival rates have significantly improved since the introduction of proteasome inhibitors (bortezomib), patients develop resistance and ultimately relapse. Therefore, this disease remains a major public health issue and there is an absolute need to develop novel therapies. In our study, we generated bortezomib-resistant cancer cell lines and conducted deubiquitinases (DUB: 100 genes) and ubiquitin-conjugating enzymes (E2: 40 genes) RNAi screens to identify which genes of these families affect cell proliferation of sensitive and/or resistant cancer cells following abrogation of their function. Among several hits, we identified the proteasome-associated DUB PSMD14, which is required for protein deubiquitination prior to their entry and degradation by the proteasome. These hits have been validated by other RNAi sequences. Further, PSMD14 was submitted to more detailed analysis using RNAi, CRISPR/Cas9 and mutagenesis approaches in sensitive or resistant cancer cells. We found that PSMD14 depletion result in a dramatic decrease of cell proliferation and cell death compared to bortezomib target PSMB5. On the other hand, we observed that the extent of histone H2A ubiquitination and HSP70 expression levels are correlated with the cellular sensitivity to proteasome inhibition. Thus, these factors could be potential biomarkers for MM patient survival prognosis.  PMSD14 as well as other candidates revealed from our screens represent potential therapeutic targets whose inhibition is predicted to overcome the acquired resistance to proteasome inhibitors currently used to treat cancer patients.
Cancer PSMD14 Proteasome Proteasome inhibitor Acquired resistance New therapy Screening Deubiquitinase Ubiquitin conjugation enzyme