Research

CDDO-Imidazolide inhibits growth and survival of c-Myc-induced mouse B cell and plasma cell neoplasms

Seong-Su Han^1,5 , Liangping Peng¹ , Seung-Tae Chung¹ , Wendy DuBois¹ , Sung-Ho Maeng² , Arthur L Shaffer³ , Michael B Sporn⁴ and Siegfried Janz¹

¹  Laboratory of Genetics, Center for Cancer Research (CCR), National Cancer Institute (NCI), National Institutes of Health (NIH), Bethesda, MD, USA

²  Laboratory of Cellular Carcinogenesis and Tumor Promotion, CCR, NCI, NIH, Bethesda, MD, USA

³  Metabolism Branch, CCR, NCI, NIH, Bethesda, MD, USA

⁴  Department of Pharmacology, Dartmouth Medical School, Hanover, NH, USA

⁵  Markey Cancer Center, Department of Radiation Medicine, University of Kentucky, Lexington, KY 40536, USA

author email corresponding author email

Molecular Cancer 2006, 5:22doi:10.1186/1476-4598-5-22

Published:	7 June 2006

Abstract

Background

Gene-targeted iMyc^Eμ mice that carry a His₆-tagged mouse Myc(c-myc)cDNA, Myc^His, just 5' of the immunoglobulin heavy-chain enhancer, Eμ, are prone to B cell and plasma cell neoplasms, such as lymphoblastic B-cell lymphoma (LBL) and plasmacytoma (PCT). Cell lines derived from Myc-induced neoplasms of this sort may provide a good model system for the design and testing of new approaches to prevent and treat MYC-driven B cell and plasma cell neoplasms in human beings. To test this hypothesis, we used the LBL-derived cell line, iMyc^Eμ-1, and the newly established PCT-derived cell line, iMyc^Eμ-2, to evaluate the growth inhibitory and death inducing potency of the cancer drug candidate, CDDO-imidazolide (CDDO-Im).

Methods

Morphological features and surface marker expression of iMyc^Eμ-2 cells were evaluated using cytological methods and FACS, respectively. mRNA expression levels of the inserted Myc^His and normal Myc genes were determined by allele-specific RT-PCR and qPCR. Myc protein was detected by immunoblotting. Cell cycle progression and apoptosis were analyzed by FACS. The expression of 384 "pathway" genes was assessed with the help of Superarray^© cDNA macroarrays and verified, in part, by RT-PCR.

Results

Sub-micromolar concentrations of CDDO-Im caused growth arrest and apoptosis in iMyc^Eμ-1 and iMyc^Eμ-2 cells. CDDO-Im-dependent growth inhibition and apoptosis were associated in both cell lines with the up-regulation of 30 genes involved in apoptosis, cell cycling, NFκB signaling, and stress and toxicity responses. Strongly induced (≥10 fold) were genes encoding caspase 14, heme oxygenase 1 (Hmox1), flavin-containing monooxygenase 4 (Fmo4), and three members of the cytochrome P450 subfamily 2 of mixed-function oxygenases (Cyp2a4, Cyp2b9, Cyp2c29). CDDO-Im-dependent gene induction coincided with a decrease in Myc protein.

Conclusion

Growth arrest and killing of neoplastic mouse B cells and plasma cells by CDDO-Im, a closely related derivative of the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid, appears to be caused, in part, by drug-induced stress responses and reduction of Myc.