Drug Resistance And Invasion In Diffuse Large B-Cell Lymphoma Are Mediated By Akt, 14-3-3 Zeta, And Vimentin

Acquired multi-drug resistance to the anthracycline-based CHOP chemotherapy is a major cause of unsuccessful treatment and mortality in 40% of diffuse large B-cell lymphoma (DLBCL) patients. To investigate molecular mechanisms of multidrug resistance, we generated CHOP-resistant DLBCL cells through repeated selection in the presence of a clinically-relevant CHOP cocktail (cyclophosphamide, doxorubicin, vincristine, prednisone at the ratio of 80:5.5:0.16:11.1). Differential protein expression between CHOP-sensitive and CHOP-resistant DLBCL cells was investigated by two-dimensional differential in-gel (DIGE) analysis, which identified 10 differentially-expressed proteins related to glycolysis (Triosephosphate isomerase-1, Enolase-1), cytoskeletal structure (Ezrin, Vimentin, Tubulin-specific chaperone B), purine biosynthesis (Serine hydroxymethyltransferase), calcium-binding (Sorcin), and apoptosis (p53, 14-3-3zeta, Akt). Upregulation of Akt, 14-3-3ζ, and Vimentin was observed by Western blotting in CHOP-resistant cells compared to CHOP-sensitive cells. These proteins were also heterogenously upregulated in primary DLBCL tissues relative to normal lymphatic tissue. Our previous studies showed that siRNA-mediated knockdown of 14-3-3ζ reversed CHOP resistance in DLBCL cells (Maxwell et al [2009] J. Biol. Chem. 284:22379-89). Our current study showed that chemical Akt inhibition overcame CHOP resistance in DLBCL cells and CHOP-resistant cells exhibited a five-fold greater ability to invade collagen matrices than CHOP-sensitive cells. Moreover, knockdown of Vimentin by siRNA or inhibition by Withaferin A decreased invasion capacity of the CHOP-resistant cells in collagen matrices. The data indicate activation of an Akt-14-3-3ζ-mediated signaling pathway as a contributor to the multi-drug resistant phenotype associated with vimentin-dependent invasive behavior in DLBCL cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 702. doi:10.1158/1538-7445.AM2011-702