Alexei F. Kisselev, Ph.D.
Associate Professor of Pharmacology & Toxicology
Pharmacology & Toxicology
Moscow State University, Moscow, Russia, MS 1991
Norris Cotton Cancer Center
Pharmacology and Toxicology Graduate Program
Program in Experimental and Molecular Medicine
7936 Rubin 632, One Medical Center Drive
Norris Cotton Cancer Center
Dartmouth Medical School
Lebanon NH 03756
proteasome different active sites as drug targets in cancer; mechanism of multiple myeloma resistance to proteasome inhibitor bortezomib; development of novel proteasome inhibitors for the treatment of multiple myeloma and solid tumors
My laboratory works on fundamental and translational aspects of proteasome pharmacology, biochemistry, and cell biology. Proteins in all living cells are constitutively synthesized and degraded. The 26S proteasome is a large (2.5MDa) ATP-dependent proteolytic machine, which is responsible for the majority of protein degradation in mammalian cells. The majority of its substrates are damaged and misfolded proteins. Cancer cells, especially those which produce large amounts of proteins (e.g., antibody-secreting multiple myeloma cells), generate excessive amounts of abnormal proteins resulting in a high load on proteasome in these cells and making cancer cells highly sensitive to proteasome inhibitors. Peptide boronate inhibitor of proteasome Velcade (bortezomib) is being used for the treatment of multiple myeloma and mantle cell lymphoma, and five other proteasome inhibitors are now undergoing clinical trials.
The translational aspects of our work are aimed at defining the roles of the proteasome’s different active sites as drug targets in cancer and using this information to develop a more potent proteasome inhibitor for the treatment of cancer. Each proteasome has three pairs of active sites, the chymotrypsin-like, trypsin-like, and caspase-like. Bortezomib and second-generation proteasome inhibitors were developed as inhibitors of the chymotrypsin-like sites, but most co-inhibit one or both of the other two sites. To clarify whether co-targeting of the other two sites is important for the anti-neoplastic activity of inhibitors, we developed highly specific inhibitors of all three sites and showed that specific inhibition of chymotrypsin-like sites is not sufficient to induce cytotoxicity. We also showed that co-inhibition of the caspase-like or, even better, of the trypsin-like sites is needed to induce maximal cytotoxicity in multiple myeloma cells. We further discovered that certain unique cell-permeable inhibitors of trypsin-like sites that we developed selectively sensitize multiple myeloma and breast cancer cells to bortezomib and carfilzomib (a proteasome inhibitor in phase III trials). Our goals for the next five years are to validate these finding in mice, identify molecular markers of response and develop approaches to selectively target inhibitors to tumors. Selective targeting will also allow us to achieve two important goals: (1) decrease toxicity of inhibitors and (2) increase inhibition of the proteasome to the levels needed to increase clinical response in myeloma and achieve it in solid tumors. We set the latter goal because we found that current clinically achievable levels of proteasome inhibition are cytotoxic to neither the majority of multiple myeloma cells lines nor to all solid tumor cell lines we have tested.
The site-specific inhibitors we have developed will also be excellent tools for studying the role of proteasome active sites in the physiological processes regulated by the ubiquitin-proteasome pathway (e.g., antigen presentation). We are pursuing this research in collaboration with other laboratories.
PEMM102 (module IV leader); Medical Pharmacology; PEMM131; Pharm133
Dr. Kisselev was born and grew up in Moscow, Russia. He received his Masters degree in Chemistry (with Honors) from the Moscow State University in in 1991. He received a Ph.D. his bioorganic chemistry in 1995 form the same University for research on HIV protease carried out at the Max-von-Pettenkofer Institute at the University of Munich in Germany. He moved to the USA in 1995 and did his postdoctoral work with Prof. Alfred Goldberg at Harvard Medical School where he received fellowship awards from the Medical Foundation and the Leukemia and Lymphoma Society.
2 graduate students currently in the lab
Multiple BH3 mimetics antagonize antiapoptotic MCL1 protein by inducing the endoplasmic reticulum stress response and up-regulating BH3-only protein NOXA.
Specific cell-permeable inhibitor of proteasome trypsin-like sites selectively sensitizes myeloma cells to bortezomib and carfilzomib.
Nature of pharmacophore influences active site specificity of proteasome inhibitors.
Activity-based profiling reveals reactivity of the murine thymoproteasome-specific subunit beta5t.
A panel of subunit-selective activity-based proteasome probes.
Incorporation of fluorinated phenylalanine generates highly specific inhibitor of proteasome's chymotrypsin-like sites.
Selective inhibitor of proteasome's caspase-like sites sensitizes cells to specific inhibition of chymotrypsin-like sites.
Joining the army of proteasome inhibitors.
A cell-permeable inhibitor and activity-based probe for the caspase-like activity of the proteasome.
Importance of the different proteolytic sites of the proteasome and the efficacy of inhibitors varies with the protein substrate.