Abstract
Purpose: Doxorubicin is administrated as a single agent in first-line
therapy of breast cancer to induce apoptosis in tumor cells. Bax,
Bcl-xL, Caspase-8 and 9 proteins are involved in induction of apoptosis. The
present study describes Bax, Bcl-xL gene expression
and Caspase-8 and 9 protein levels in MCF-7 cells incubated with doxorubicin at
different doses an incubation times.
Methods: The cytotoxic
effects of doxorubicin were studied using MTT assay. MCF-7
cells were treated with three concentrations of doxorubicin (0.1, 0.5, 1 μM)
and incubated for 24, 48 and 72 hours then expression levels of Bax and Bcl-xL
genes were elucidated by Real-time RT-PCR technique and protein levels of
caspase-8 and caspase-9 proteins were measured using ELISA method.
Morphological modifications of the cells were also monitored via light
microscopic images.
Results:
Doxorubicin decreased the anti-apoptotic Bcl-xL and increased
pro-apoptotic Bax mRNA levels. Doxorubicin induced a significant
increase in Bax /Bcl-xL ratio in all doses and incubation
times (p<0.05). Highest (more than 10 fold) increase in Bax /Bcl-xL
ratio was revealed after 48 h incubation of the cells with in all
doses of doxorubicin. Doxorubicin also increased caspase-9 level in a time and
dose-dependent manner, while
caspase-8 level didn't follow time and dose dependency pattern.
Conclusion: Our results confirm that
doxorubicin induces mitochondrial-dependent apoptosis by down-regulation of
Bcl-xL and up- regulation of Bax and caspase-9 expressions.