osu-03012 and Lymphoma--B-Cell

We recently reported that inhibition of Cyclooxygenase-2 (Cox-2) reduced human B-CLL proliferation and survival. Herein, we investigated the mechanisms whereby small molecule Cox-2 selective inhibitors, SC-58125 (a Celebrex analog) and CAY10404 blunt survival of human B-cell lymphomas and chronic lymphocytic leukemia B-cells. SC-58125 and OSU03012 (a Celebrex analog that lacks Cox-2 inhibitory activity) both decreased intracellular glutathione (GSH) content in malignant human B-cells, as well as in Cox-2 deficient mouse B-cells. This new finding supports Cox-2 independent effects of SC-58125. Interestingly, SC-58125 also significantly increased B-cell reactive oxygen species (ROS) production, suggesting that ROS are a pathway that reduces malignant cell survival. Addition of GSH ethyl ester protected B lymphomas from the increased mitochondrial membrane permeability and reduced survival induced by SC-58125. Moreover, the SC-58125-mediated GSH depletion resulted in elevated steady-state levels of the glutamate cysteine ligase catalytic subunit mRNA and protein. These new findings of increased ROS and diminished GSH levels following SC-58125 exposure support novel mechanisms whereby a Cox-2 selective inhibitor reduces malignant B-cell survival. These observations also support the concept that certain Cox-2 selective inhibitors may have therapeutic value in combination with other drugs to kill malignant B lineage cells.

Topics: Animals; B-Lymphocytes; Catalytic Domain; Cell Proliferation; Cell Survival; Cells, Cultured; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Dose-Response Relationship, Drug; Glutamate-Cysteine Ligase; Glutathione; Humans; Isoxazoles; Leukemia, Lymphocytic, Chronic, B-Cell; Lymphoma, B-Cell; Mice; Mice, Knockout; Oxidative Stress; Pyrazoles; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sulfonamides; Sulfones

Chronic lymphocytic leukemia (CLL) is an incurable adult leukemia characterized by disrupted apoptosis. OSU03012 is a bioavailable third-generation celecoxib derivative devoid of cyclooxygenase-2 inhibitory activity that potently induces apoptosis in prostate cancer cell lines and is being developed as an anticancer therapy in the National Cancer Institute (NCI) Rapid Access to Intervention Development (RAID) program. We assessed the ability of OSU03012 to induce apoptosis in primary CLL cells and the mechanism by which this occurs. The LC50 (lethal concentration 50%) of OSU03012 at 24 hours was 7.1 microM, and this decreased to 5.5 microM at 72 hours. Additionally, we have demonstrated that OSU03012 mediates apoptosis by activation of the intrinsic, mitochondrial pathway of apoptosis but also activates alternative cell death pathways that are caspase independent. The early activation of both caspase-dependent and -independent pathways of apoptosis is novel to OSU03012 and suggests it has great potential promise for the treatment of CLL. Moreover, unlike the great majority of therapeutic agents used to treat leukemia or other forms of cancer, OSU03012 induces cell death entirely independent of bcl-2 expression. Overall, these data provide justification for further preclinical development of OSU03012 as a potential therapeutic agent for CLL.

Topics: Apoptosis; Caspases; Cell Transformation, Neoplastic; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Lymphoma, B-Cell; Mitochondria; Proto-Oncogene Proteins c-bcl-2; Pyrazoles; Sulfonamides; Tumor Cells, Cultured