Contributions
Abstract: PB1604
Type: Publication Only
Background
The second messenger cAMP plays key roles in multiple intracellular signaling pathways. cAMP signaling pathway can impede drug-induced apoptosis in leukemic cells and elevated levels of this second messenger inhibit doxorubicin-induced apoptosis and p53 accumulation in acute lymphoblastic leukemia cells. In addition, elevated cAMP levels may activate a variety of signaling pathways through protein kinases. cAMP responsive element binding protein (CREB) is a transcription factor that can be activated by cAMP-dependent protein kinase A. CREB is overexpressed in majority of bone marrow samples from patients with ALL and AML and confers survival advantage to the cancer cells.
Aims
According to the fact that cAMP can activate CREB and the role of CREB in malignant cell growth, we sought to determine if CREB plays the mediator role in inhibitory effect of cAMP on doxorubicin-induced apoptosis and p53 accumulation in BCP-ALL cells or not. Moreover, we aimed to assess the effect of CREB on BCP-ALL, NALM-6 cells proliferation and survival.
Methods
In present study, CREB was knocked down using lentiviral CREB shRNA in NALM-6 cells. Knocked down cells were treated with doxorubicin in presence or absence of the cAMP-elevating agents. The expression levels of different apoptotic and anti-apoptotic proteins were assessed by western blot analysis. Gene expression levels were evaluated using qRT-PCR. The apoptosis was assessed using flowcytometry analysis.
Results
We demonstrated here that CREB knockdown induced apoptosis and impaired growth of BCP-ALL NALM-6 cells which was associated with caspase activation. The gene expression levels of prosurvival signals Bcl-2, Mcl-1, Bcl-xL, survivin and XIAP were down-regulated upon CREB suppression. However, the p53 and p21 levels remain unchanged in CREB knocked down cells. Amazingly, our results showed that CREB knockdown cannot eliminate the inhibitory effect of elevated cAMP on doxorubicin-induced apoptosis and p53 accumulation in BCP-ALL cells.
Conclusion
These findings indicate a critical role for CREB in proliferation, survival, and apoptosis of BCP-ALL cells. The data also suggest that targeting CREB alone could possibly serve as potential therapeutic approach in BCP-ALL but it cannot restore the doxorubicin-induced apoptosis and p53 accumulation in malignant cAMP-elevated cells.
Session topic: 1. Acute lymphoblastic leukemia – Biology & Translational Research
Keyword(s): Acute lymphoblastic leukemia, Apoptosis, CAMP
Abstract: PB1604
Type: Publication Only
Background
The second messenger cAMP plays key roles in multiple intracellular signaling pathways. cAMP signaling pathway can impede drug-induced apoptosis in leukemic cells and elevated levels of this second messenger inhibit doxorubicin-induced apoptosis and p53 accumulation in acute lymphoblastic leukemia cells. In addition, elevated cAMP levels may activate a variety of signaling pathways through protein kinases. cAMP responsive element binding protein (CREB) is a transcription factor that can be activated by cAMP-dependent protein kinase A. CREB is overexpressed in majority of bone marrow samples from patients with ALL and AML and confers survival advantage to the cancer cells.
Aims
According to the fact that cAMP can activate CREB and the role of CREB in malignant cell growth, we sought to determine if CREB plays the mediator role in inhibitory effect of cAMP on doxorubicin-induced apoptosis and p53 accumulation in BCP-ALL cells or not. Moreover, we aimed to assess the effect of CREB on BCP-ALL, NALM-6 cells proliferation and survival.
Methods
In present study, CREB was knocked down using lentiviral CREB shRNA in NALM-6 cells. Knocked down cells were treated with doxorubicin in presence or absence of the cAMP-elevating agents. The expression levels of different apoptotic and anti-apoptotic proteins were assessed by western blot analysis. Gene expression levels were evaluated using qRT-PCR. The apoptosis was assessed using flowcytometry analysis.
Results
We demonstrated here that CREB knockdown induced apoptosis and impaired growth of BCP-ALL NALM-6 cells which was associated with caspase activation. The gene expression levels of prosurvival signals Bcl-2, Mcl-1, Bcl-xL, survivin and XIAP were down-regulated upon CREB suppression. However, the p53 and p21 levels remain unchanged in CREB knocked down cells. Amazingly, our results showed that CREB knockdown cannot eliminate the inhibitory effect of elevated cAMP on doxorubicin-induced apoptosis and p53 accumulation in BCP-ALL cells.
Conclusion
These findings indicate a critical role for CREB in proliferation, survival, and apoptosis of BCP-ALL cells. The data also suggest that targeting CREB alone could possibly serve as potential therapeutic approach in BCP-ALL but it cannot restore the doxorubicin-induced apoptosis and p53 accumulation in malignant cAMP-elevated cells.
Session topic: 1. Acute lymphoblastic leukemia – Biology & Translational Research
Keyword(s): Acute lymphoblastic leukemia, Apoptosis, CAMP