Elucidating the molecular mechanism of action by which RS1-208b induces apoptosis in hematological cancers

Ruben Israel Calderon, University of Texas at El Paso


The 26S proteasome has been successfully targeted to treat multiple myeloma. However, the effect can sometimes be reversed as cells acquire resistance to chemotherapy. Recently, combining proteasome inhibitors with indirect proteasome inhibitors has been proposed in order to delay and even reverse resistance. Small molecules derived from 4-piperidinone that maintain an unsaturated β-carbonyl group are thought to interact with the thiol group of catalytically active cysteine residues in deubiquitinases that associate with the 26S proteasome, effectively inhibiting the proteasome. RS1-208b was selected following a high-throughput screening of a small library of 4-piperidinone derived curcumin structural analogs due to its selectivity towards hematological cancers and its ability to inhibit inflammatory cytokine production. In silico docking experiments showed RS1-208b can inhibit cysteine deubiquitinases by bringing the unsaturated β-carbonyl in close proximity to the thiol group. AmpliSeq analysis revealed RS1-208b elicits a cellular response that is similar to that of proteasome inhibitors collected in the Connectivity Map. Treatment with RS1-208b leads to the rapid accumulation of poly-ubiquitinated proteins, which initiates a cellular response that culminates in cell death. RS1-208b up-regulated transcripts in the PERK-mediated unfolded protein response and the intrinsic pathway of apoptosis, which was verified using several fluorescence based assays. In vivo, RS1-208b delayed the tumor growth in RAMOS xenograft models and increased event-free survival time.

Subject Area

Biology|Molecular biology|Cellular biology

Recommended Citation

Calderon, Ruben Israel, "Elucidating the molecular mechanism of action by which RS1-208b induces apoptosis in hematological cancers" (2016). ETD Collection for University of Texas, El Paso. AAI10249923.