Thymoquinone induces apoptosis in malignant T-cells via generation of ROS.

We show that HTLV-1 negative leukemia cells are more sensitive to TQ due to higher levels of drug-induced reactive oxygen species (ROS). PreG1 population in HTLV-1 negative Jurkat and CEM was higher than HTLV-1 transformed HuT-102 and MT-2 cells. Peripheral blood mononuclear cells were more resistant. Hoechst staining indicated more features of apoptosis, namely nuclear blebs and shrunken nuclei in HuT-102 than Jurkat. A greater depletion of the antioxidant enzyme glutathione occurred in Jurkat, which consequently led to an increase in ROS, loss of mitochondrial membrane potential, cytochrome c release, activation of caspases 3 and 9, and cleavage of PARP. Treatment with z-VAD-fmk partially reversed TQ-induced apoptosis, suggesting a caspase-dependent mechanism. N-acetyl cysteine prevented apoptosis providing evidence that cell death is ROS-dependent. Catalase prevented apoptosis to a lesser extent than NAC. In summary, TQ induces apoptosis in adult T cell leukemia/lymphoma by decreasing glutathione and increasing ROS, and levels of ROS underlie the differential cellular response to TQ. Our data suggest a potential therapeutic role for TQ in sensitizing HTLV-I-negative T-cell lymphomas.

Sage components enhance cell death through nuclear factor kappa-B signaling.

The sage components linalyl acetate (Ly) and alpha-terpineol (Te) exhibit synergistic anti-proliferative effects. We investigated the effects of Ly and Te on NF-kappaB signaling in HCT-116 colon cancer cells. Ly and Te combinations dose-dependently reduced HCT-116 viability at non-cytotoxic concentrations. Combination treatment induced 30%-60% increase in PreG1 through induction of apoptosis and necrosis. DNA binding assays revealed that combination treatment suppressed both basal and TNF-alpha-induced NF-kappaB activation. This suppression correlated with the inhibition of p65 nuclear translocation and IkappaB-alpha degradation. The lack of change in IKK expression levels or inhibition in IkappaB-alpha phosphorylation suggest the involvement of an IKK-independent mechanism. Ly and Te combination was found to downregulate the expression of NF-kappaB-regulated antiapoptotic and proliferative gene products. Separate treatments and drug combinations significantly decreased DNA binding activity of NF-kappaB which led to the potentiation of cell death induced by the colon cancer drugs oxaliplatin and 5-FU. These results indicate that Ly and Te anticancer activities are partly mediated through the suppression of NF-kappaB activation, suggesting their use in combination with chemotherapeutic agents to induce apoptosis.