Small-molecule inhibitor of AF9/ENL-DOT1L/AF4/AFF4 interactions suppresses malignant gene expression and tumor growth

HAT1 is a central regulator of chromatin synthesis that acetylates nascent histone H3:H4 tetramers in the cytoplasm. It may have a role in cancer metabolism by linking cytoplasmic production of acetyl-CoA to nuclear acetyl flux. This is because the HAT1 di-acetylation mark is not propagated in chromatin and instead is de-acetylated after nascent histone insertion into chromatin. Thus, HAT1 likely provides a nuclear source of free acetate that may be recycled to acetyl-CoA for nuclear acetylation reactions. Correspondingly, suppression of HAT1 protein expression impairs tumor growth. To ascertain whether targeting HAT1 is a viable anti-cancer treatment strategy we sought to identify small molecule inhibitors of HAT1. We developed a high-throughput HAT1 acetyl-click assay to facilitate drug discovery and enzymology. Screening of small molecules computationally predicted to bind the active site led to the discovery of multiple riboflavin analogs that inhibited HAT1 enzymatic activity by competing with acetyl-CoA binding. These hits were refined by synthesis and testing over 70 analogs, which yielded structure-activity relationships. The isoalloxazine core was required for enzymatic inhibition, whereas modifications of the ribityl sidechain improved enzymatic potency and cellular growth suppression. These efforts resulted in a lead compound (JG-2016) that suppressed growth of human cancer cells lines in vitro and impaired tumor growth in vivo. This is the first report of a small molecule inhibitor of the HAT1 enzyme complex and represents a step towards targeting this pathway for cancer therapy.

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Evaluation of TW-37, a pan Bcl-2 Proteins Small-Molecule Inhibitor, Against Spectrum of Human B-Cell Lines and Patient-Derived Samples.

Blood ◽

10.1182/blood.v110.11.4521.4521 ◽

2007 ◽

Vol 110 (11) ◽

pp. 4521-4521

Author(s):

Ramzi M. Mohammad ◽

Yuan Sun ◽

Shaomeng Wang ◽

Amro Aboukameel ◽

Ayad M. Al-Katib

Keyword(s):

Tumor Growth ◽

B Cell ◽

Cell Lines ◽

Small Molecule ◽

Cell Lymphoma ◽

Lymphoblastic Leukemia ◽

B Cell Lymphoma ◽

Small Molecule Inhibitor ◽

Molecule Inhibitor ◽

Human B Cell

Abstract Non-Hodgkin’s lymphoma (NHL) tumors include a group of heterogeneous diseases with varying natural histories and responsiveness to therapy; nonetheless, overexpression of Bcl-2 protein is seen in more than 80% of NHL. Throughout the years our laboratory succeeded in establishing a panel of B-cell lines representing various maturational stages of NHL. In this study, we have utilized a structure-based strategy to design a new class of potent nonpeptidic small-molecule inhibitor (SMI) of Bcl-2 family. TW-37, a lead compound that was designed to target the BH3 binding groove of antiapopototic Bcl-2 proteins. It binds to Bcl-2, Bcl-XL and Mcl-1 with Ki values of 290 nM, 1110 nM and 260 nM, respectively. TW-37 showed significant antiproliferative effect against Pre-B-Acute Lymphoblastic Leukemia (WSU-pre-B-ALL), Diffuse Large Cell Lymphoma (WSU-DLCL2), Follicular Small Cleaved Cell Lymphoma (WSU-FSCCL), Waldenstrom’s Macroglobulinemia (WSU-WM) and primary cells obtained from lymphoma patients, despite variations in their anti- and pro-apoptotic Bcl-2 proteins (Bcl-2, Bcl-XL, Mcl-1, Bax, Bak, Bim, Bad, BUMA and Bok). The IC50 for TW-37 varied from 165 nM in the WSU-FSCCL to 300 nM in WSU-DLCL2 cells. Apoptosis was independent of proliferative status or pathological classification of B-cell tumor. TW-37 was able to block Bim-Bcl-XL and Bim-Mcl-1 eterodimerization and induces apoptosis via activation of caspases -9, -3, PARP and DNA fragmentation. Although cell lines and patient samples expressed multiple Bcl-2 family proteins at various levels, TW-37 induced apoptosis was only strongly associated with Bax:Mcl-1 ratio. TW-37 administered to tumor-bearing SCID mice led to significant tumor growth inhibition (T/C), tumor growth delay (T-C) and Log10kill, when used at its maximum tolerated dose (40 mg/kg x 3days) via tail vein. failed to induce changes in the Bcl-2 proteins levels suggests that assessment of baseline Bcl-2 family proteins can be used to prognosticate the response to drug. These findings indicate activity of TW-37 across the spectrum of human B-cell tumors and support the concept of targeting the Bcl-2 system as a therapeutic strategy in the treatment of B-cell lymphoma.

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Targeting deubiquitinase activity with a novel small-molecule inhibitor as therapy for B-cell malignancies

Blood ◽

10.1182/blood-2014-10-605584 ◽

2015 ◽

Vol 125 (23) ◽

pp. 3588-3597 ◽

Cited By ~ 63

Author(s):

Luke F. Peterson ◽

Hanshi Sun ◽

Yihong Liu ◽

Harish Potu ◽

Malathi Kandarpa ◽

...

Keyword(s):

Tumor Growth ◽

B Cell ◽

Cell Survival ◽

Small Molecule ◽

Myeloma Cell ◽

Small Molecule Inhibitor ◽

B Cell Malignancies ◽

Molecule Inhibitor ◽

Key Points

Key Points Deubiquitinases Usp9x and Usp24 regulate Mcl-1 and myeloma cell survival. Small-molecule–mediated Usp9x/Usp24 inhibition induces apoptosis and blocks myeloma tumor growth in vivo.

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