AIM： To investigate the role of Beclin 1 on the susceptibility of HepG2 cells to undergo apoptosis after anti-Fas antibody or doxorubicin treatment. METHODS： Beclin 1 silencing was achieved using RNA interference. D...AIM： To investigate the role of Beclin 1 on the susceptibility of HepG2 cells to undergo apoptosis after anti-Fas antibody or doxorubicin treatment. METHODS： Beclin 1 silencing was achieved using RNA interference. DNA ploidy, the percentage of apoptotic cells and the mitochondrial membrane potential were assessed by flow cytometry. Levels of Beclin 1, BCI-XL and cytochrome c, and the cleavage of poly （ADP-ribose） polymerase （PARP） were assayed by using Western blots. RESULTS： Beclin 1 expression decreased by 75% 72 h after Beclin 1 siRNA transfection. Partial Beclin 1 silencing significantly increased the percentage of subG1 cells 24 and 40 h after treatment with doxorubicin or anti-Fas antibody, respectively, and this potentiation was abrogated by treatment with a pan-caspase inhibitor. Partial Beclin 1 silencing also increased PARP cleavage, mitochondrial membrane depolarization and cytosolic cytochrome c. The pro-apoptotic consequences of partial Beclin 1 silencing were not associated with a decline in Bcl-XL expression.CONCLUSION： Partial Beclin 1 silencing aggravates mitochondrial permeabilization and apoptosis in HepG2 cells treated with an anti-Fas antibody or with doxorubicin.展开更多
AIM： To investigate the effect of stable c-Fos over- expression on immortalized human hepatocyte （IHH） proliferation. METHODS： IHHs stably transfected with c-Fos （IHH- Fos） or an empty vector （IHH-C） were grow...AIM： To investigate the effect of stable c-Fos over- expression on immortalized human hepatocyte （IHH） proliferation. METHODS： IHHs stably transfected with c-Fos （IHH- Fos） or an empty vector （IHH-C） were grown in me- dium supplemented with 1% serum or stimulated with 10% serum. Cell proliferation was assessed by cell counts, 3H-thymidine uptake and flow cytometry analyses. The levels of cell cycle regulatory proteins （Cyclin DI, E, A） cyclin dependent kinases （cdk） cdk2, cdk4, cdk6, and their inhibitors p15, p16, p21, p27, total and phosphorylated GSK-3β and epidermal growth factor receptor （EGF-R） were assayed by Western blotting. Analysis of O/c/in D1 mRNA levels was performed by reverse transcription-polymerase chain reaction and real-time polymerase chain reaction （PCR） analysis. Stability of Cyclin DI was studied by cycloheximide blockade experiments. RESULTS： Stable c-Fos overexpression increased cell proliferation under low serum conditions and resulted in a two-fold increase in [3H]-thymidine incorpora- tion following serum addition. Cell cycle analysis by flow cytometry showed that c-Fos accelerated the cell cycle kinetics. Following serum stimulation, Cyclin D1 was more abundantly expressed in c-Fos overexpress- ing cells. Cyclin D1 accumulation did not result from increased transcriptional activation, but from nuclear stabilization. Overexpression of c-Fos correlated with higher nuclear levels of inactive phosphorylated GSK- 3β, a kinase involved in Cyclin D1 degradation and higher levels of EGF-R mRNA, and EGF-R protein com- pared to IHH-C both in serum starved, and in serum stimulated cells. Abrogation of EGF-R signalling in IHH- Fos by treatment with AG1478, a specific EGF-R tyro- sine kinase inhibitor, prevented the phosphorylation of GSK-3β induced by serum stimulation and decreased Cyclin D1 stability in the nucleus. CONCLUSION： Our results clearly indicate a positive role for c-Fos in cell cycle regulation in hepatocytes. Importantly, we delineate a new mechanism by which c-Fos could contribute to hepatocarcinogenesis through stabilization of Cyclin D1 within the nucleus, evoking a new feature to c-Fos implication in hepatocellular carcinoma.展开更多
文摘AIM： To investigate the role of Beclin 1 on the susceptibility of HepG2 cells to undergo apoptosis after anti-Fas antibody or doxorubicin treatment. METHODS： Beclin 1 silencing was achieved using RNA interference. DNA ploidy, the percentage of apoptotic cells and the mitochondrial membrane potential were assessed by flow cytometry. Levels of Beclin 1, BCI-XL and cytochrome c, and the cleavage of poly （ADP-ribose） polymerase （PARP） were assayed by using Western blots. RESULTS： Beclin 1 expression decreased by 75% 72 h after Beclin 1 siRNA transfection. Partial Beclin 1 silencing significantly increased the percentage of subG1 cells 24 and 40 h after treatment with doxorubicin or anti-Fas antibody, respectively, and this potentiation was abrogated by treatment with a pan-caspase inhibitor. Partial Beclin 1 silencing also increased PARP cleavage, mitochondrial membrane depolarization and cytosolic cytochrome c. The pro-apoptotic consequences of partial Beclin 1 silencing were not associated with a decline in Bcl-XL expression.CONCLUSION： Partial Beclin 1 silencing aggravates mitochondrial permeabilization and apoptosis in HepG2 cells treated with an anti-Fas antibody or with doxorubicin.
文摘AIM： To investigate the effect of stable c-Fos over- expression on immortalized human hepatocyte （IHH） proliferation. METHODS： IHHs stably transfected with c-Fos （IHH- Fos） or an empty vector （IHH-C） were grown in me- dium supplemented with 1% serum or stimulated with 10% serum. Cell proliferation was assessed by cell counts, 3H-thymidine uptake and flow cytometry analyses. The levels of cell cycle regulatory proteins （Cyclin DI, E, A） cyclin dependent kinases （cdk） cdk2, cdk4, cdk6, and their inhibitors p15, p16, p21, p27, total and phosphorylated GSK-3β and epidermal growth factor receptor （EGF-R） were assayed by Western blotting. Analysis of O/c/in D1 mRNA levels was performed by reverse transcription-polymerase chain reaction and real-time polymerase chain reaction （PCR） analysis. Stability of Cyclin DI was studied by cycloheximide blockade experiments. RESULTS： Stable c-Fos overexpression increased cell proliferation under low serum conditions and resulted in a two-fold increase in [3H]-thymidine incorpora- tion following serum addition. Cell cycle analysis by flow cytometry showed that c-Fos accelerated the cell cycle kinetics. Following serum stimulation, Cyclin D1 was more abundantly expressed in c-Fos overexpress- ing cells. Cyclin D1 accumulation did not result from increased transcriptional activation, but from nuclear stabilization. Overexpression of c-Fos correlated with higher nuclear levels of inactive phosphorylated GSK- 3β, a kinase involved in Cyclin D1 degradation and higher levels of EGF-R mRNA, and EGF-R protein com- pared to IHH-C both in serum starved, and in serum stimulated cells. Abrogation of EGF-R signalling in IHH- Fos by treatment with AG1478, a specific EGF-R tyro- sine kinase inhibitor, prevented the phosphorylation of GSK-3β induced by serum stimulation and decreased Cyclin D1 stability in the nucleus. CONCLUSION： Our results clearly indicate a positive role for c-Fos in cell cycle regulation in hepatocytes. Importantly, we delineate a new mechanism by which c-Fos could contribute to hepatocarcinogenesis through stabilization of Cyclin D1 within the nucleus, evoking a new feature to c-Fos implication in hepatocellular carcinoma.
