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Institute of Molecular Medicine

Laboratory of Steven Grant, M.D.

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Research projects

The goal of this laboratory is to elucidate links that exist between survival signaling and cell cycle regulatory pathways, and to exploit this information to develop novel therapeutic approaches to the treatment of cancer, particularly hematopoietic malignancies.

In one project, researchers are exploring the factors that regulate activation of the NF-ĸB pathway by histone deacetylase inhibitors in human leukemia cells and determining the mechanisms by which interruption of this process may lead to enhanced cell killing. Dr. Grant’s team has recently reported that HDAC inhibitors trigger NF-ĸB activation through the atypical, “inside-out” ATM/NEMO/SUMOylation cascade, and that interference with this process, genetically or pharmacologically, dramatically increases HDAC inhibitor-mediated apoptosis.

In a related project, laboratory members are investigating the role of phosphorylation on RelA acetylation, nuclear translocation and activation, and the impact of disrupting IKK function in regulating these events as well as cell survival. These studies are also being extended to include other arms of the DNA damage response.

In another project, the Grant laboratory is exploiting their observation that interference with the DNA damage response at the level of Chk1 in human multiple myeloma cells elicits the potent activation of the Ras/Raf/MEK/ERK pathway, and that disabling of the latter cascade (e.g., by MEK1/2 shRNA or pharmacologic MEK1/2 inhibitors) leads to a striking increase in expression of the pro-apoptotic protein Bim accompanied by marked apoptosis. They have recently observed that Src inhibitors recapitulate these actions, and promote Chk1 inhibitor lethality both in vitro and in vivo — the latter in association with the pronounced inhibition of angiogenesis. Studies are currently underway extending these findings to include cytokinetically quiescent cells (G0G1), as well as myeloma cells with stem cell characteristics.

This group’s studies are also exploring strategies designed to enhance the activity of proteasome inhibitors in diffuse large B-cell and mantle cell lymphoma. They have observed that HDAC inhibitors and small molecule BH3 mimetics sharply increase proteasome inhibitor lethality in these cells via a process that involves activation of the stress-related kinase JNK, and in the former case, an inactivation of NF-ĸB. Recently, these studies have been extended to include a novel, irreversible proteasome inhibitor, carfilzomib, and have indicated that such regimens actively induce apoptosis in lymphoma cells highly resistant to standard proteasome inhibitors.

Another myeloma-related project seeks to exploit the observation that CDK inhibitors that disrupt CDK9 function act as transcriptional repressors as a consequence of their ability to inhibit the pTEBb/CDK9/cyclin T complex, and by extension, phosphorylation of the CTD of RNA Pol II. This leads to down-regulation of multiple short-lived proteins, including Mcl-1. These researchers have found that such CDK9 inhibitors potentially enhance the activity of BH3 mimetics toward multiple myeloma cells. They are in the process of extending these findings to animal models as a prelude to proposing novel treatment strategies involving CDK9 inhibitors and BH3 mimetics in patients with refractory multiple myeloma.

Additional projects are underway examining mechanisms by which HDAC inhibitors promote the activity of dual aurora kinase/Bcr/Abl inhibitors in Bcr/Abl+ leukemias, and interactions between the multi-kinase and Raf inhibitor sorafenib and BH3mimetics in human leukemia cells.

Laboratory members

Elisa Attkisson
Laboratory Specialist

Mandy Aust
Laboratory Specialist

Shuang Chen, M.D., Ph.D.
Instructor

Yun Dai, M.D., Ph.D.
Associate Professor

Girija Dasmahapatra, Ph.D.
Instructor

Beata Holkova, M.D.
Assistant Professsor

Lora Kramer
Life/Physical Science Technician II

Tri Nguyen, M.D., Ph.D.
Instructor

Rebecca Parker
Laboratory Specialist

Xin-Yan Pei, Ph.D.
Instructor

Mohamed Rahmani, Ph.D.
Associate Professor

Yu Zhang
Postdoctoral Associate

Liang Zhou
Postdoctoral Associate

Key publications

Rahmani M, Mayo M, Attkisson E, Grant S. Inhibition of Bcl-2 anti-apoptotic members by obatoclax potently enhances sorafenib-induced apoptosis in human myeloid leukemia cells through a Bim-dependent process. Blood, In press.

Chen S, Xinyan Pei, Myers J, Wang L, Kramer LB, Schwartz D, Su F, Simmons G, Richey JD, Larsen DG, Orlowski R, Dai Y, Grant S. CDK inhibitors up-regulate BH3-only proteins to sensitize human myeloma cells to BH3 mimetic therapies. Cancer Research, In press.

Dai Y, Chen S, Pei X-Y, Shah R, Dent P, Grant S. Src inhibitors lower the threshold for Chk1-inhibitor lethality in human myeloma cells in vitro and in vivo. Blood 2011, 117:1947-1957.

Grant S, Milstein S, Spiegel S. Endogenous modulators and pharmacologic inhibitors of histone deacetylases in cancer therapy. Oncogene 2011, 31:537-551.

Dai Y, Chen S, Wang L, Pei X-Y, Funk V, Kramer LB, Dent P, Grant S. Disruption of IĸB kinase (IKK)-mediated RelA serine 536 phosphorylation sensitizes human multiple myeloma cells to histone deacetylase (HDAC) inhibitors. Journal of Biologic Chemistry 2011, 286:34036-34050.

Dasmahapatra G, Jordan N, Friedberg J, Fisher R, Dent P, Grant S. Vorinostat synergistically potentiates the activity of the proteasome inhibitor carfilzomib in DLBCL cells sensitive or resistant to bortezomib. Blood 2010, 115:4478-87.

Rosato RR, Kolla S, Coe S, Almenara J, Patel A, Amin S, Atadja P, Fisher PB, Dent P, Grant S. Histone deacetylase inhibitors activate NF-ĸB in human leukemia cells through an oxidative injury and DNA damage/ATM/NEMO-dependent mechanism. Journal of Biologic Chemistry. 2010, 285:10064-10077.

Chen S, Dai, Y, Pei X-Y, Grant S. Bim upregulation by the histone deacetylase inhibitor SBHA underlies interactions with the Bcl-2 antagonist ABT-737: evidence for distinct anti-apoptotic functions of Bcl-2, Bcl-xL and Mcl-1. Molecular and Cell Biology. 2009, 29:6149-6169.

Rahmani M, Habibi J, Yacoub A, Davis EM, Dent P, Grant S. The kinase inhibitor sorafenib kills human leukemia cells through a process involving induction of ER stress. Molecular and Cellular Biology. 2007, 15:5499-5513.

Rahmani M, Davis EM, Bauer C, Dent P, Grant S. Apoptosis induced by the kinase inhibitor BAY 43-9006 in human leukemia cells involves down-regulation of Mcl-1 through inhibition of translation. Journal of Biologic Chemistry. 2005 280:35217-35227.

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