Caspase-independent apoptosis induction of quorum-sensing autoinducer analogs against chronic myeloid leukemia K562

Emerging applications of bacteria as antitumor agents

Bacteria are associated with the human body and colonize the gut, skin, and mucous membranes. These associations can be either symbiotic or pathogenic. In either case, bacteria derive more benefit from their host. The ability of bacteria to enter and survive within the human body can be exploited for human benefit. They can be used as a vehicle for delivering or producing bioactive molecules, such as toxins and lytic enzymes, and eventually for killing tumor cells. Clostridium and Salmonella have been shown to infect and survive within the human body, including in tumors. There is a need to develop genetic circuits, which enable bacterial cells to carry out the following activities: (i) escape the human immune system, (ii) invade tumors, (iii) multiply within the tumorous cells, (iv) produce toxins via quorum sensing at low cell densities, and (v) express suicide genes to undergo cell death or cell lysis after the tumor has been lysed. Thus, bacteria have the potential to be exploited as anticancer agents.

The crude extract of Corni Fructus induces apoptotic cell death through reactive oxygen species-modulated pathways in U-2 OS human osteosarcoma cells

Crude extract of Corni Fructus (CECF) has been used in Traditional Chinese medicine for the treatment of different diseases for hundreds of years. The purpose of this study was to investigate the cytotoxic effects of CECF on U-2 OS human osteosarcoma cells. Flow cytometry was used for measuring the percentage of viable cells, cell-cycle distribution, apoptotic cells in sub-G1 phase, reactive oxygen species (ROS), Ca(2+) levels, and mitochondrial membrane potential (ΔΨm ). Comet assay and 4'-6-diamidino-2-phenylindole staining were used for examining DNA damage and condensation. Western blotting was used to examine apoptosis-associated protein levels in U-2 OS cells after exposed to CECF. Immunostaining and confocal laser system microscope were used to examine protein translocation after CECF incubation. CECF decreased the percentage of viability, induced DNA damage and DNA condensation, G₀/G₁ arrest, and apoptosis in U-2 OS cells. CECF-stimulated activities of caspase-8, caspase-9, and caspase-3, ROS, and Ca(2+) production, decreased ΔΨm levels of in U-2 OS cells. CECF increased protein levels of caspase-3, caspase-9, Bax, cytochrome c, GRP78, AIF, ATF-6α, Fas, TRAIL, p21, p27, and p16 which were associated with cell-cycle arrest and apoptosis. These findings suggest that CECF triggers apoptosis in U-2 OS cells via ROS-modulated caspase-dependent and -independent pathways.

Icaritin suppresses the proliferation of human osteosarcoma cells in vitro by increasing apoptosis and decreasing MMP expression

AIM

To explore whether icaritin, a prenylflavonoid derivative of the Chinese tonic herb Epimedium, could suppress the proliferation of human osteosarcoma cells in vitro, and to elucidate the mechanisms of the action.

METHODS

Human osteosarcoma SaOS2 cell line was used in the present study. The proliferation of the cells was examined using MTT assay and immunofluorescence DAPI staining. Cell motility was studied with the scratch assay. Cell apoptosis was determined by Annexin V-FITC and PI double staining using flow cytometry. Western blotting and RT-PCR were used to measure the expression of mRNAs and proteins in the cells.

RESULTS

Icaritin (5-15 μmol/L) suppressed the proliferation of SaOS2 cells in vitro in a dose-dependent manner. Furthermore, the cell motility was significantly decreased after exposure to icaritin. Moreover, icaritin (5 μmol/L) time-dependently induced the apoptosis of SaOS2 cells, markedly suppressed MMP-2 and MMP-9 expression, upregulated caspase-3 and caspase-9 expression, and increased the level of cleaved caspase-3 in the cells. Co-exposure to the caspase-3 inhibitor zVAD-fmk (10 μmol/L) compromised the icaritin-induced caspase-3 expression and apoptosis in SaOS2 cells.

CONCLUSION

Icaritin suppresses the proliferation of SaOS2 human osteosarcoma cells by increasing apoptosis and downregulating MMP expression.

[Quorum sensing in bacteria and yeast]

Bacterial sets are complex dynamic systems, which interact with each other and through the interaction, bacteria coexist, collaborate, compete and share information in a coordinated manner. A way of bacterial communication is quorum sensing. Through this mechanism the bacteria can recognize its concentration in a given environment and they can decide the time at which the expression of a particular set of genes should be started for developing a specific and simultaneous response. The result of these interconnections raises properties that cannot be explained from a single isolated bacterial cell.