Preclinical studies of TW-37, a new nonpeptidic small-molecule inhibitor of Bcl-2, in diffuse large cell lymphoma xenograft model reveal drug action on both Bcl-2 and Mcl-1.

Abstract

PURPOSE:

Overexpression of Bcl-2 protein has been observed in more than 80% of B-cell lymphomas, including diffuse large cell lymphoma (DLCL), the most common subtype of non-Hodgkin's lymphoma. We have previously employed the natural product (-)-gossypol to test its therapeutic potential as a small-molecule inhibitor of Bcl-2 for the treatment of B-cell lymphomas.

EXPERIMENTAL DESIGN:

Recently, we have used a structure-based strategy to design a new class of potent small-molecule inhibitor acting on Bcl-2. One such lead compound is the benzenesulfonyl derivative TW-37, which was designed to target the BH3-binding groove in Bcl-2 where proapoptotic Bcl-2 proteins, such as Bak, Bax, Bid, and Bim bind.

RESULTS:

In our fluorescence polarization-based binding assays using recombinant Bcl-2, Bcl-X(L), and Mcl-1 proteins, TW-37 binds to Bcl-2, Bcl-X(L), and Mcl-1 with K(i) values of 290, 1,110 and 260 nmol/L, respectively. Hence, TW-37 is a potent inhibitor of Bcl-2 and has >3-fold selectivity over Bcl-X(L). In vitro, TW-37 showed significant antiproliferative effect in a de novo chemoresistant WSU-DLCL(2) lymphoma cell line and primary cells obtained from a lymphoma patient with no effect on normal peripheral blood lymphocytes. Coimmunoprecipitation experiments showed that TW-37 disrupted heterodimer formation between Bax or truncated-Bid and antiapoptotic proteins in the order Mcl-1 > Bcl-2 >> Bcl-X(L). As expected, TW-37 caused apoptotic death. Pre-exposure of lymphoma cells to TW-37 significantly enhanced the killing effect of cyclophosphamide-doxorubicin-vincristine-prednisone (CHOP) regimen. The maximum tolerated dose of TW-37 in severe combined immunodeficient (SCID) mice was 40 mg/kg for three i.v. injections when given alone and 20 mg/kg, x3 when given in combination with CHOP. Using WSU-DLCL(2)-SCID mouse xenograft model, the addition of TW-37 to CHOP resulted in more complete tumor inhibition compared with either CHOP or TW-37 alone.

CONCLUSIONS:

We conclude that the administration of TW-37, as a potent Bcl-2 and Mcl-1 inhibitor, to standard chemotherapy may prove an effective strategy in the treatment of B-cell lymphoma.

• Authors: Ramzi M Mohammad, Anton Scott Goustin, Amro Aboukameel, Ben Chen, Sanjeev Banerjee, Guoping Wang, Zaneta Nikolovska-Coleska, Shaomeng Wang, Ayad Al-Katib
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 13 Issue 7 Pg. 2226-35 (Apr 01 2007) ISSN: 1078-0432 [Print] United States
• PMID: 17404107 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Benzamides
• Proto-Oncogene Proteins c-bcl-2
• Sulfones
• TW-37 compound
• Vincristine
• Doxorubicin
• Cyclophosphamide
• Prednisone

Topics

• Animals
• Antineoplastic Agents (chemistry, pharmacology)
• Antineoplastic Combined Chemotherapy Protocols (therapeutic use)
• Apoptosis (drug effects)
• Benzamides (chemistry, pharmacology)
• Blotting, Western
• Cyclophosphamide (therapeutic use)
• Dose-Response Relationship, Drug
• Doxorubicin (therapeutic use)
• Female
• Flow Cytometry
• Humans
• Immunoprecipitation
• Lymphoma, Large B-Cell, Diffuse (drug therapy)
• Mice
• Prednisone (therapeutic use)
• Protein Binding
• Proto-Oncogene Proteins c-bcl-2 (antagonists & inhibitors)
• Sulfones (chemistry, pharmacology)
• Vincristine (therapeutic use)
• Xenograft Model Antitumor Assays