Carnosol, a dietary diterpene, displays growth inhibitory effects in human prostate cancer PC3 cells leading to G2-phase cell cycle arrest and targets the 5'-AMP-activated protein kinase (AMPK) pathway.
OBJECTIVE
This study examines the anti-cancer effect of carnosol in human prostate cancer PC3 cells and its role in modulating multiple signaling pathways associated with carcinogenesis.


METHODS
PC3 cells were treated with carnosol and were evaluated using a flow cytometry, a protein array and Western blot analysis to identify signaling pathways targeted by carnosol.


RESULTS
Using an MTT assay we found that carnosol (10-70 microM) decreases cell viability in a time and dose-dependent manner. Further analysis using flow cytometry as well as biochemical analysis identified G2-phase cell cycle arrest. To establish a more precise mechanism, we performed a protein array that evaluated 638 proteins involved in cell signaling pathways. The protein array identified 5'-AMP-activated protein kinase (AMPK), a serine/threonine protein kinase involved in the regulation of cellular energy balance as a potential target. Further downstream effects consistent with cancer inhibition included the modulation of the mTOR/HSP70S6k/4E-BP1 pathway. Additionally, we found that carnosol targeted the PI3K/Akt pathway in a dose dependent manner.


CONCLUSIONS
These results suggest that carnosol targets multiple signaling pathways that include the AMPK pathway. The ability of carnosol to inhibit prostate cancer in vitro suggests carnosol may be a novel agent for the management of PCa.
Johnson
Jeremy J
JJ
Center for Women's Health Research, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin, USA.
Syed
Deeba N
DN
Heren
Chenelle R
CR
Suh
Yewseok
Y
Adhami
Vaqar M
VM
Mukhtar
Hasan
H
D055372:AMP-Activated Protein Kinases; D045784:Abietanes / Q000494:pharmacology*; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D016195:G2 Phase / Q000187:drug effects*; D006801:Humans; D008297:Male; D009097:Multienzyme Complexes / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000473:pathology* / Q000517:prevention & control; D040081:Protein Array Analysis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors
D055372:AMP-Activated Protein Kinases; D045784:Abietanes; D016588:Anticarcinogenic Agents; D051017:Apoptosis Regulatory Proteins; D018797:Cell Cycle Proteins; D009097:Multienzyme Complexes; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C068623:carnosol