Effects of STI571 and p27 gene clone on proliferation and apoptosis of K562 cells

Silencing of phospholipase C gamma 2 promotes proliferation of rat hepatocytes in vitro

The management of hepatic failure is undoubtedly difficult, and poor results have led to the search for novel therapeutic approaches. Nowadays, anti-apoptotic gene therapy is considered as an ideal approach. It has been proved that phospholipase Cγ2 (PLCγ2) is involved in the apoptosis of immune cells and tumor cells; however, whether this gene is related to hepatocyte death is still unclear. This study examined the role of PLCγ2 by inhibiting its expression in rat hepatocytes with siRNA. We also further analyzed the cellular mechanism by which the expression inhibition of PLCγ2 induces cell death. Silencing PLCγ2 gene by adenovirus vector expressing PLCγ2-targeted siRNA caused the great decline in the number of G1- and G2/M phase cells, the significant increase in the number of S phase cells, and the obvious reduction in apoptosis index. In addition, silencing PLCγ2 gene relieved the rat hepatocyte damage, such as the cell shrinkage and chromatin condensation, nuclear fragmentation. Further analysis of Ad-PLCγ2 siRNA-transfected hepatocytes demonstrated that suppression of PLCγ2 gene expression could cause the caspase dependent cell death by inhibiting the signal pathway MEKK1/MKK4/JNK1/2/c-Jun. In conclusion, these findings suggest that interference with PLCγ2 expression could relieve the inhibitory effect of PLCγ2 on hepaocyte apoptosis, thus, promote proliferation through inactivating PKCδ-mediated JNK1/2 signaling pathway.

Hyperthermia induces differentiation without apoptosis in permissive temperatures in human erythroleukaemia cells

PURPOSE

The aim of the present study was to investigate whether induction of differentiation by hyperthermia is accompanied by apoptosis and necrosis to further evaluate the benefits of using hyperthermia as a differentiation inducing physical modality.

MATERIALS AND METHOD

Differentiation was evaluated in K562 erythroleukaemia cells by measuring haemoglobin synthesis and flow cytometric measurement of glycophorin A expression. Apoptosis was measured by Annexin-V-FITC and Propidium Iodide (PI) double staining assay. Apoptosis and necrosis was also evaluated morphologically using staining with acridine orange/ethidium bromide (AO/EtBr) by fluorescence microscopy. Heat shock protein 70 (HSP70) level was measured by ELISA kit.

RESULTS

Hyperthermia (43 degrees C) induced differentiation as judged by increased haemoglobin synthesis and glycophorin A expression. No sign of apoptosis or necrosis could be detected at this temperature. Cell viability did not change due to heat treatment, and cellular proliferation was reduced in a dose (heating time) dependent manner. At 45 degrees C, hyperthermia induced apoptosis and necrosis with minimal or no sign of differentiation. HSP70 level was significantly increased at 43 degrees C along with differentiation of leukaemic cells, while at 45 degrees C no significant effect on HSP70 production could be observed.

CONCLUSIONS

The encouraging results obtained here indicate that by heat treatment at 43 degrees C, hyperthermia can be used alone or in combination with other modalities as a differentiation inducing agent without any detectable apoptotic activity. Positive correlation between HSP70 production and induction of differentiation and lack of apoptosis by hyperthermia confirm the possible role of HSP70 in the heat-induced differentiation and apoptosis in leukaemic cells.