Cell biology international [Cell Biol Int] 2009 Mar; Vol. 33 (3), pp. 402-10. Date of Electronic Publication: 2009 Feb 07.
Apoptosis, Benzimidazoles chemistry, Caspases metabolism, Cell Line, Tumor, Collagen Type XI metabolism, Cytochromes c metabolism, Dose-Response Relationship, Drug, Fluorescent Dyes chemistry, Humans, K562 Cells, Leukemia, Myelogenous, Chronic, BCR-ABL Positive metabolism, Leukemia, Myelogenous, Chronic, BCR-ABL Positive pathology, Antineoplastic Agents pharmacology, Lipid Peroxidation drug effects, and gamma-Linolenic Acid pharmacology
Various polyunsaturated fatty acids, especially gamma-linolenic acid (GLA), inhibit the growth of a variety of tumor cells. Some evidence indicates that polyunsaturated fatty acid can kill cells by apoptosis. In the current study, we tested the apoptotic effect of GLA on human chronic myelogenous leukemia K562 cells. GLA induced K562 cell death in a dose-dependent manner. Typical apoptotic nuclei were shown by staining of K562 cells with DNA-binding fluorochrome Hoechst 33342, characterized by chromatin condensation and nuclear fragmentation. Flow cytometric analysis also demonstrated that GLA caused dose-dependent apoptosis of K562 cells. The apoptosis could be inhibited by a pancaspase inhibitor (z-VAD-fmk), suggesting the involvement of caspases. Further, release of cytochrome c, activation of caspase-3 and cleavage of PARP were found in GLA-induced apoptosis. GLA treatment could also elevate lipid peroxidation in K562 cells, and antioxidant alpha-tocopherol could reverse the cytotoxicity of GLA. The saturated fatty acid SA, which did not exhibit significant increase in lipid peroxidation, also did not induce cytotoxicity. Intracellular GSH was also determined, and there was no marked change of GSH levels in cells after incubation with GLA compared with the control. These results demonstrate that GLA could induce apoptosis in K562 cells. Apoptosis is mediated by release of cytochrome c, activation of caspase-3. Lipid peroxidation may play a role in GLA cytotoxicity.
Chemico-biological interactions [Chem Biol Interact] 2006 Aug 25; Vol. 162 (2), pp. 140-8. Date of Electronic Publication: 2006 Jun 09.
Amino Acid Chloromethyl Ketones pharmacology, Butylated Hydroxytoluene pharmacology, Caspase 3, Cell Nucleus drug effects, Cell Proliferation drug effects, Cell Survival drug effects, Dose-Response Relationship, Drug, Doxorubicin pharmacology, Drug Resistance, Multiple, Drug Resistance, Neoplasm, Flow Cytometry, Humans, K562 Cells, L-Lactate Dehydrogenase metabolism, Malondialdehyde metabolism, Time Factors, Apoptosis drug effects, Caspases metabolism, Lipid Peroxidation drug effects, and gamma-Linolenic Acid pharmacology
Numerous studies have revealed that gamma-linolenic acid (GLA) possesses effective tumoricidal properties while not inducing damage to normal cells or creating harmful systemic side effects. It can exert anti-tumor efficacy against a variety of cancers including leukemia. However, little is known about the effects of GLA on leukemia resistant to chemotherapy, emerging as a serious clinical problem. The present study tested GLA-induced apoptosis in K562/ADM multidrug-resistant (MDR) leukemic cells and investigated its possible mechanisms. Using cell viability, fluorescent staining of nuclei, flow cytometric Annexin V/PI double staining and lactate dehydrogenase (LDH) release, we found that GLA could inhibit cell growth and induce apoptosis and secondary necrosis. The results showed that incubation with GLA concentrations of 10-60 microg/ml caused a dose- and time-dependent decrease of K562/ADM cell viability, and the IC50 value was 50.5 microg/ml at 24 h and 31.5 microg/ml at 48 h. Flow cytometry using Annexin V/PI double staining assessed apoptosis, necrosis and viability. Typical apoptotic nuclei were shown by staining of K562/ADM cells with DNA-binding fluorochrome Hoechst 33342, characterized by chromatin condensation and nuclear fragmentation. On the other hand, after treated K562/ADM cells with 20 microg/ml GLA for 48 h and with 40 microg/ml GLA for 12 h, the LDH release significantly increased, indicated losses of plasma membrane integrity and presence of necrosis. Further, the inhibition of GLA-induced apoptosis by a pan-caspase inhibitor (z-VAD-fmk) suggested the involvement of caspases. The increase of caspase-3 activity with GLA concentration confirmed its role in the process. The results also showed that the malondialdehyde (MDA) content was also significantly elevated, and antioxidant BHT could block GLA cytotoxity, indicating the cytotoxity induced by GLA may be due to lipid peroxidation.