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.
OBJECTIVE
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.


METHODS
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.
Mohammad
Ramzi M
RM
Division of Hematology and Oncology, Department of Internal Medicine, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan, USA. Mohammad@karmanos.org
Goustin
Anton Scott
AS
Aboukameel
Amro
A
Chen
Ben
B
Banerjee
Sanjeev
S
Wang
Guoping
G
Nikolovska-Coleska
Zaneta
Z
Wang
Shaomeng
S
Al-Katib
Ayad
A
D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides / Q000737:chemistry / Q000494:pharmacology*; D015153:Blotting, Western; D003520:Cyclophosphamide / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000627:therapeutic use; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D047468:Immunoprecipitation; D016403:Lymphoma, Large B-Cell, Diffuse / Q000188:drug therapy*; D051379:Mice; D011241:Prednisone / Q000627:therapeutic use; D011485:Protein Binding; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors*; D013450:Sulfones / Q000737:chemistry / Q000494:pharmacology*; D014750:Vincristine / Q000627:therapeutic use; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D001549:Benzamides; D019253:Proto-Oncogene Proteins c-bcl-2; D013450:Sulfones; C515128:TW-37 compound; D014750:Vincristine; D004317:Doxorubicin; D003520:Cyclophosphamide; D011241:Prednisone