cay-10404 and Leukemia--Lymphocytic--Chronic--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

We recently reported that activated normal human B lymphocytes express Cox-2. These findings prompted us to evaluate whether human B-CLL cells express Cox-2 and synthesize prostaglandins. In contrast to naive human B cells, B-CLL cells constitutively expressed Cox-2 protein and produced PGE2, PGF2alpha, and TXA2. Elevated Cox-2 expression was seen in a subgroup of B-CLL cells that exhibit poor prognostic factors, including unmutated variable heavy chain status and increased CD38 expression. Furthermore, stimulation of B-CLL cells with CD40 ligand plus TNFalpha increased Cox-2 levels. The role of Cox-2 in promoting B-CLL survival was investigated using nonselective and selective Cox-2 inhibitors. Significant reductions in B-CLL survival occurred following Cox-2 inhibition. These new findings support that constitutive Cox-2 expression in B-CLL cells promotes their survival and possibly their expansion in vivo. It will therefore be important to evaluate drugs that inhibit Cox-2 as potential therapeutic agents in B-CLL in vivo.

Topics: B-Lymphocytes; Cell Growth Processes; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Dinoprost; Dinoprostone; Enzyme Activation; Humans; Immunoglobulin Heavy Chains; Immunohistochemistry; Indomethacin; Isoxazoles; Leukemia, Lymphocytic, Chronic, B-Cell; Nitrobenzenes; Pyrazoles; Sulfonamides; Sulfones; Thromboxane A2