OSU-DY7, a Novel D-Tyrosinol Derivative, Mediates Cytotoxicity in Chronic Lymphocytic Leukemia and Lymphoblastic Lymphoma through p38 Mitogen-Activated Protein Kinase Pathway.

Chronic lymphocytic leukemia (CLL) is a most common form of adult leukemia with minimal treatment options. Drug resistance and associated immune deregulation limit use of current therapies, thus warranting need for alternative therapy development. Our laboratories recently identified a novel D-tyrosinol-derived compound targeting p38 MAPK pathway, OSU-DY7 [(R)-2-amino-3-(4-heptyloxy-phenyl)-propan-1-ol]. Here we demonstrate the efficacy of OSU-DY7 for lymphocytic cell lines and primary B cells from CLL patients.

We tested the pre-clinical efficacy of OSU-DY7 in primary CLL B cells and B cell lines representing CLL (MEC-1), ALL (697), and lymphoblastic lymphoma (Raji and Ramos).

The cytotoxicity of OSU-DY7 was both dose- and time-dependent. The IC₅₀ of OSU-DY7 at 24 hrs for MEC-1, 697, Raji, Ramos and primary B-CLL cells were 2.40 μM, 10.39 μM, 6.04 μM, 3.75 μM and 3.58 μM respectively. OSU-DY7 induced activation of caspase-3 and poly (adenocine diphosphate-ribose) polymerase (PARP) cleavage. Pancaspase inhibitor Z-VAD-FMK partially rescued OSU-DY7-induced cytotoxicity in CLL B cells and cell lines. Interestingly, OSU-DY7 mediated-cytotoxicity was associated with increased phosphorylation of p38 MAPK and its downstream target protein MAPKAPK2 in both lymphocytic cell lines and primary B-CLL cells. Compared with control group, the ratio of p-p38MAPK (Thr180Tyr182) versus p38MAPK in Raji cells treated with 2 μM, 4 μM and 8 μM of OSU-DY7 increased 2.2, 4.7 and 11 fold respectively (p<0.0001). Similar increase in p38MAPK phosphorylation was also observed in six CLL patient samples after treatment with OSU-DY7 2 μM, 4 μM and 8 μM for 24 hours (p=0.0004). Moreover, SB202190, a specific p38 MAPK inhibitor, decreased MAPKAPK2 protein level with concomitant rescue of the cells from the OSU-DY7 mediated-cytotoxicity. Thus pretreatment of Raji and primary CLL B cells with SB202190 reduced the OSU-DY7 induced cytotoxicity by 36.7% and 24.3% respectively by 24hrs (Raji:p<0.0001; primary CLL B cells: p<0.005 ). Furthermore, SB202190 rescued OSU-DY7 down regulated survivin protein by ∼2 fold (p<0.0001, n=3) and mRNA levels by 2.4 fold (95% CI: 1.56∼3.84 fold, p=0.0026, n=3) in Raji cells indicating a role for p38MAPK dependent regulation of survivin by OSU-DY7.

This study provides an evidence for a role of OSU-DY7 in p38 MAPK dependent activation and survivin down regulation associated with apoptosis in lymphocytic cells, thus warranting further development of this novel agent for alternative therapy for lymphocytic malignancies. [This work was supported by D. Warren Brown Foundation and Leukemia and Lymphoma Society]

No relevant conflicts of interest to declare.