Inactivation of PI3K/Akt signaling mediates proliferation inhibition and G2/M phase arrest induced by andrographolide in human glioblastoma cells.
OBJECTIVE
Andrographolide, a principal diterpenoid lactone isolated from the traditional herbal medicine Andrographis paniculata, has been reported to show anti-tumor activity. Since the high lipid solubility of andrographolide permits it to penetrate the blood-brain barrier and concentrate in the brain, we hypothesized that andrographolide may be a potential chemotherapeutic agent for the treatment of glioblastomas. To clarify this point, we investigated the growth inhibitory effect and mechanisms of actions of andrographolide on human glioblastoma U251 and U87 cells.


METHODS
MTT assay and trypan blue exclusion assay were used to investigate the proliferation inhibitory and cytotoxic effects of andrographolide, respectively. Cell cycle distribution was analyzed using flow cytometry. Apoptosis analysis proceeded by detecting the cleavage of caspase-3. The levels of proteins were probed by Western blotting.


RESULTS
The results showed that non-toxic concentrations of andrographolide inhibited the proliferation of human glioblastoma cells through induction of G2/M arrest, which was accompanied by down-regulating Cdk1 and Cdc25C proteins. Additionally, andrographolide decreased the activity of PI3K/Akt signaling, as demonstrated by down-regulation of the expression of phos-PI3K, phos-Akt, phos-mTOR and phos-p70s6k in U251 and U87 cells. Furthermore, additive effects on the proliferation inhibition, G2/M arrest and down-regulation of G2/M phase-related proteins were observed, when a combined treatment of andrographolide with PI3K inhibitor LY294002 was used in U251 and U87 cells.


CONCLUSIONS
We prove that andrographolide inhibits the proliferation of human glioblastoma cells via inducing G2/M arrest, which is mediated by inhibiting the activity of PI3K/Akt signaling.
Department of Pharmacology, Shenyang Pharmaceutical University, Shenyang 110016, China.
Yanchun
Y
Li
Pengfei
P
Zhang
Feng
F
Qiu
Lixia
L
Chen
Caixia
C
Miao
Jianchun
J
Li
Wei
W
Xiao
Enlong
E
Ma
D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D004224:Diterpenes / Q000494:pharmacology*; D016195:G2 Phase / Q000187:drug effects* / Q000502:physiology; D005909:Glioblastoma / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D000894:Anti-Inflammatory Agents, Non-Steroidal; D004224:Diterpenes; D006131:Growth Inhibitors; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; C030419:andrographolide