Figure 2.
Constitutive expression of activated JNK and phospho-c-jun in B lymphomas and the effect of MAPK inhibitors on the growth of murine and human B-lymphoma cells. (A) Murine and human B-lymphoma cell lines (i), primary B lymphoma isolated from mouse (ii), and primary B-lymphoma samples from human patients (iii) expressed phosphorylated form of JNK constitutively with little expression by normal splenic B cells, normal peripheral blood human B cells, and prostate cancer cells (LNCaP and PC-3). A variety of B-lymphoma cell lines and tumors from both murine and human origin express phosphorylated form of c-jun constitutively (iv). Mouse primary tumors are spontaneous B lymphomas from aged mice (tumor nos. 1 to 7) and B lymphomas isolated from Eμ-Myc transgenic mice. Human primary B lymphomas include small-cell lymphoma (SCL), large-cell lymphoma (LCL), follicular cell lymphoma (FCL), Burkitt lymphoma (BL), and marginal zone lymphoma (MZL), which are characterized by flow cytometry. (B) BKS-2 B-lymphoma cells were cultured for 48 hours with vehicle (DMSO) alone or with indicated concentrations of SP600125 or PD98059. Results were expressed as percentage of basal proliferation (mean ± SE of triplicate cultures) when compared with cells that were not treated with any inhibitor. The actual counts are 61 449 ± 2636 for the untreated cells. (C) BJAB B-lymphoma cells were cultured for 48 hours with vehicle (DMSO) alone, or the indicated concentrations of SP600125, PD98059, or SB203580. The actual counts are 119 333 ± 7118 for the medium. Panels D, E, F, G, and H represent the effect of SP600125 on basal proliferation of CH12.LX, WEHI-231, CH31, Ramos, and RAJI B-lymphoma cells, respectively; panels I and J, of OCI-Ly7 and OCI-Ly10 DLBCL cells, respectively. For D-G and I-J, ▪ indicates SP600125; □, DMSO equivalents. (K) Annexin V staining of prostate cancer cell line PC-3 in the presence or absence of varying concentrations of SP600125 for 24 hours. MG132 is used as a positive control, which is a proteasome inhibitor. Results are presented as means ± SE of triplicate cultures. *P < .05 when comparing response with SP600125 to solvent or medium-only treatment. Results are representative of 3 experiments.