Harrison College of Pharmacy

Current Funding

Proteasome inhibitor for the treatment of solid tumors
Funder: NCI R01 CA213223
Date: 2017-23
Role: Principal Investigator
Total Cost: $1,805,000
Goal: The major goal of this project is to determine whether 2-specific proteasome inhibitors sensitize triple-negative breast cancer cells to FDA-approved proteasome inhibitors, and whether inhibition of the recovery of proteasome will also sensitize them to these agents.

Laboratory Personnel

Graduate Students

• Olasubomi Akintola
• Fnu Ibtisam
• Tyler Jenkins
• Sriraja Srinivasa

Research Assistant

• Mitchell Patterson

External Links

• NCBI Bibliography
• Google Scholar Profile
• ORCID Profile
• LinkedIn Profile

Research Interests and Publications

Overview - My laboratory is focused on targeting the proteasome for the treatment of cancer. The proteasome is a multi-subunit, multiple active sites proteolytic complex that, through degradation of abnormal polypeptides, plays a key role in protein quality control in every mammalian cells. It also degrades many regulatory proteins and thus plays a major role in the regulation of many cellular functions (e.g., cell cycle, gene transcription). Rapidly proliferating tumor cells depend more on proteasome function than non-malignant cells, creating a therapeutic window for using proteasome inhibitors for the treatment of cancer. Three proteasome inhibitors, bortezomib, carfilzomib and ixazomib, are approved by the FDA for the treatment of multiple myeloma and mantle cell lymphoma.

• Kisselev AF, van der Linden WA, Overkleeft HS. Proteasome inhibitors: an expanding army attacking a unique target. Chem. Biol. 2012: 20; 99-115. PMID: 11514224
• Kisselev AF, Goldberg AL. Proteasome inhibitors: from research tools to drug candidates. Chem. Biol. 2001; 8: 739-758. PMID: 11514224

Major Accomplishments - The major accomplishment of our laboratory is the development of specific inhibitors of b5, b1 and b2 active sites and using these inhibitors to define the roles of these sites as drug targets in cancer. We found that inhibition of b5 sites, which are the prime targets of the FDA-approved inhibitors, is not sufficient to cause apoptosis of tumor cells, and that specific inhibitors of b1 and b2 sites dramatically sensitize malignant cells to b5 inhibitors.

• Kisselev AF. Site-specific proteasome inhibitors. Biomolecules 2022; 12: 54. PMID:35053202.
• Geurink PP, van der Linden WA, Mirabella AC, Gallastegui N, de Bruin G, Blom AEM, Voges MJ, Mock ED, Florea BI, van der Marel GA, Driessen C, van der Stelt M, Groll M, Herman S. Overkleeft HS, and Kisselev AF. Incorporation of non-natural amino acids improves cell permeability and potency of specific inhibitors of proteasome trypsin-like sites. J. Med. Chem. 2013; 56:1262-75. PMID: 23320547.
• Mirabella AC, Pletvev AA, Downey SL, Britton M, Shabaneh TA, Verdoes M, Filipov D, Overkleft HS, Kisselev AF. Specific cell-permeable inhibitor of proteasome’s trypsin-like sites selectively sensitizes myeloma cells to bortezomib and carfilzomib. Chem. Biol. 2011: 18; 608-18 PMID: 21609842
• Screen M, Britton M, Downey SL, Verdoes M, Voges MJ, Bloom AEM, Geurink PP, Risseeuw MDP, Florea BI, van der Linden WA, Pletnev AA, Overkleeft HS, Kisselev AF. Thenature of pharmacophore influences active site specificity of proteasome inhibitors. J. Biol. Chem. 2010; 285: 40125-34. PMID: 20937826
• Britton M, Lucas MM, Downey SL, Screen M, Verdoes M, Pletnev AA, Tokhunts RA, Amir O, Goddard AL, Pelphrey PM, Wright DL, Overkleeft HS, Kisselev AF. Selective inhibitors of proteasome’s caspase-like sites sensitize cells to specific inhibition of chymotrypsin-like sites. Chem. Biol. 2009: 16, 1278-1289. PMID: 20064438.

Current Projects - The major goal of our laboratory is to expand the use of proteasome inhibitors to the treatment of different cancers, using the knowledge about optimal active site profile of these agents that we generated using site-specific inhibitors. We are focusing on acute lymphoblastic leukemia (ALL) and triple-negative breast cancer (TNBC) because cell lines derived from these cancers are as sensitive to bortezomib as multipel myeloma cells. We are pursuing several projects.

Nanoparticle formulations of proteasome inhibitors to solid tumors. The major obstacle to expanding use of proteasome inhibitors to the treatment of solid tumors is their low metabolic stability, poor tumor penetration and on-target toxicities due to inhibition of proteasome in normal tissues (e.g., gastrointestinal, cardiac and renal toxicities). To overcome these problems, we are developing, in collaboration with Dr. Arnold in our department, liposomal nanoparticle formulations of proteasome inhibitors.

Immunoproteasome inhibitors for the treatment of hematologic malignancies. Hematologic malignancies are difficult to target with nanoparticles, and our approach to selective inhibition of proteasome in these tumors is to target lymphoid-tissue specific form of proteasome called the immunoproteasome. ALL cells express the highest ratio of immune to constitutive proteasomes among hematologic malignancies, and we found that ALL cells are very sensitive to immunoproteasome inhibitors. This projects is focused on a subtype of ALL that is driven by t(4;11) chromosomal translocation that results in the expression of MLL-AF4 fusion protein, confers poor prognosis, but makes cells highly sensitive to proteasome inhibitors. Most infant ALLs are driven by this translocation and an additional benefit of using immunoproteasome inhibitors instead of FDA-approved inhibitors is that it will reduce pediatric specific toxicities (e.g., inhibition of bone growth and testicular development) caused by inhibition of constitutive proteasome in non-lymphoid tissues.

• Jenkins TW, Downey-Kopyscinski SL, Fields JL, Colley WC, Israel MA, Maksimenko AV, Fiering SN, Kisselev AF. Anti-leukemic activity of immunoproteasome inhibitor ONX-0914 in acute lymphoblastic leukemia expressing MLL-AF4 fusion protein. Scientific Reports 2021; 11:10883. PMID:340435431
• Downey-Kopyscinski S, Daily EW, Gautier M, Bhatt A, Florea BI, Mitsiades CS, Richardson P, Driessen C, Overkleeft HS, Kisselev AF. An inhibitor of proteasome β2 sites sensitizes myeloma cells to immunoproteasome inhibitors. Blood Adv. 2018; 2:2443-2451 (25 citations).  PMID: 30266819.

Mechanism of recovery of proteasome activity after treatments with inhibitors. Another obstacle to clinical efficacy of proteasome inhibitors is the rapid recovery of proteasome activity after clinically relevant pulse-treatment. According to the published literature, the recovery is a transcriptional response mediated by the transcription factor Nrf1 (NFE2L1), which is activated by a novel aspartic protease DDI2. We have obtained strong evidence that there is a second pathway for the recovery of proteasome activity and are currently dissecting this pathway.

• Weyburne ES, Wilkins O, Sha Z, Williams DA, Pletnev AA, de Bruin G, Overkleeft HS, Goldberg AL, Cole MD, Kisselev AF. Inhibition of the proteasome β2 site sensitizes triple-negative breast cancer cells to β5 inhibitors and suppresses Nrf1 activation. Cell Chem. Biol. 2017; 24: 218-230. PMID: 28132893.

Mechanistic basis of sensitivity of non-myeloma cells to proteasome inhibitors. Despite an essential role of proteasome in the quality control of nascent polypeptides, proteasome inhibitors are effective in MM cells because these cells produce and secreted large amounts of immunoglobulins creating a very high load on proteasome. Together with other laboratories, we found that sensitivity of myeloma cells to proteasome inhibitors depends on the load of proteasomes in these cells. ALL and TNBC cells are as sensitive to proteasome inhibitors as MM in vitro but molecular basis of such sensitivity is not known. We are currently testing whether high load on proteasome in these cells is responsible for higher sensitivity and why the load on proteasomes in these cells is higher than in other tumors.

• Shabaneh TB, Downey SL, Screen M, Goddard A, Lucas M, and Eastman A, Kisselev AF* Molecular basis of differential sensitivity of myeloma cells to clinically relevant bolus treatment with bortezomib. PLoS ONE 2013; 8:e56132 PMID: 23460792.
• Downey-Kopyscinski SL, Srinivasa S, Kisselev AF. Clinically relevant pulse-treatment generates bortezomib-resistant myeloma cell line that lacks proteasome mutations and is sensitive to Bcl-2 inhibitor venetoclax. Scientific Reports 2022; 12:12788. PMID 35896610.

Novel proteasome inhibitors. 26S proteasome consists of 20S proteolytic core, which contains 1, 2, and 5 proteolytic sites, and 19S regulatory particle that recognizes and unfold substrates, and controls access to the 20S proteolytic core. Unfolding is carried out by 6 ATPase subunits of the 19S particles. There are no inhibitors of proteasome 19S ATPase activity. While investigating the mechanism of synergy between proteasome inhibitors and inhibitors of Bruton’s tyrosine kinase (BTK) kinase we found that some of them inhibit multiple proteolytic activities of the 20S core and ATPase activity of the 26S proteasome. This work demonstrates the feasibility of the development of inhibitors of the 26S proteasome ATPase activity.