Antiproliferative and proapoptotic effects of topotecan in combination with thymoquinone on acute myelogenous leukemia.

BACKGROUND: Topotecan has shown promising antineoplastic activity in solid tumors and acute leukemia. Because of the primary dose-limiting toxicity of topotecan, it is necessary to identify other agents that can work synergistically with topotecan, potentially increasing its efficacy while limiting its toxicity. Many studies showed synergism in combination of topotecan with gemcitabine and bortezomib. Other studies report the increase in growth inhibition of gemcitabine or oxaliplatin when cells were preexposed to naturally occurring drugs such as thymoquinone. The aim of this project was to study the mode of action of topotecan along with thymoquinone, on survival and apoptosis pathways in acute myelogenous leukemia (AML) cell lines, and to investigate the potential synergistic effect of thymoquinone on topotecan. MATERIALS AND METHODS: U937 cells were incubated with different topotecan and thymoquinone concentrations for 24 and 48 hours, separately and in combination. Cell proliferation was determined using WST-1 (Roche) reagent. The effect of the compounds on protein expression of Bax, Bcl2, p53, caspase-9, -8, and -3 was determined using Western blot analysis. Cell cycle analysis was performed in addition to annexin/propidium iodide staining. RESULTS: Thymoquinone and topotecan exhibited antiproliferative effects on U937 cells when applied separately. In combination, the reduction in proliferation was extremely significant with a major increase in the expression levels of Bax/Bcl2, p53, and caspase-3 and -9. Preexposure with thymoquinone resulted in an increase in cell growth inhibition compared with topotecan treatment. CONCLUSION: Thymoquinone, when combined with topotecan in noncytotoxic doses, produced synergistic antiproliferative and proapoptotic effects in AML cells. Preexposure to thymoquinone seems to be more effective than simultaneous application with topotecan.

Kefir exhibits anti­proliferative and pro­apoptotic effects on colon adenocarcinoma cells with no significant effects on cell migration and invasion.

Kefir, a fermented milk product, exhibits anti­tumoral activity in vivo; yet its mechanism of action remains elusive. Recent studies have focused on the mechanism of action of kefir on cancer cells in vitro. The current study aims at examining the effect of kefir on cell survival, proliferation, and motility of colorectal cancer (CRC) cells. Kefir's anti­cancer potential was tested on CRC cell lines, Caco­2 and HT­29, through cytotoxicity, proliferation, and apoptotic assays. The expression of certain genes involved in proliferation and apoptosis was measured using reverse transcriptase­polymerase chain reaction (RT­PCR) and western blotting. To assess the effect of kefir on cancer metastasis, wound­healing and time­lapse movies, in addition to collagen­based invasion assay, were used. The results show that cell­free fractions of kefir exhibit an anti­proliferative effect on Caco­2 and HT­29 cells. Analysis of DNA content by flow cytometry revealed the ability of kefir to induce cell cycle arrest at the G1 phase. Kefir was also found to induce apoptosis, as seen by cell death ELISA. Results from RT­PCR showed that kefir decreases the expression of transforming growth factor α (TGF­α); and transforming growth factor­ß1 (TGF­ß1) in HT­29 cells. Western blotting results revealed an upregulation in Bax:Bcl­2 ratio, confirming the pro­apoptotic effect of kefir, and an increase in p53 independent­p21 expression upon kefir treatment. MMP expression was not altered by kefir treatment. Furthermore, results from time­lapse motility movies, wound­healing, and invasion assays showed no effect on the motility of colorectal as well as breast (MCF­7 and MB­MDA­231) cancer cells upon kefir treatment. Our data suggest that kefir is able to inhibit the proliferation and induce apoptosis in HT­29 and Caco­2 CRC cells, yet it does not exhibit a significant effect on the motility and invasion of these cells in vitro.