Carnosic acid modulates Akt/IKK/NF-κB signaling by PP2A and induces intrinsic and extrinsic pathway mediated apoptosis in human prostate carcinoma PC-3 cells.

Abstract

This study investigates the efficacy of carnosic acid (CA), a polyphenolic diterpene, isolated from the plant rosemary (Rosemarinus officinalis), on androgen-independent human prostate cancer PC-3 cells. CA induced anti-proliferative effects in PC-3 cells in a concentration- and time-dependent manner, which was due to apoptotic induction as evident from flow-cytometry, DNA laddering and TUNEL assay. Apoptosis was associated with the activation of caspase-8, -9, -3 and -7, increase in Bax:Bcl-2 ratio, release of cytochrome-c and decrease in expression of inhibitor of apoptosis (IAP) family of proteins. Apoptosis was attenuated upon pretreatment with specific inhibitors of caspase-8 (Z-IETD-fmk) and caspase-9 (Z-LEHD-fmk) suggesting the involvement of both intrinsic and extrinsic apoptotic cascades. Further, apoptosis resulted from the inhibition of IKK/NF-κB pathway as evident from decreased DNA binding activity, nuclear translocation of p50 and p65 and IκBα phosphorylation. The down-regulation of IKK/NF-κB was associated with inhibition of Akt phosphorylation and its kinase activity with a concomitant increase in the serine/threonine protein phosphatase 2A (PP2A) activity. Pharmacologic inhibition of PP2A by okadaic acid and calyculin A, significantly reversed CA-mediated apoptotic events in PC-3 cells indicating that CA induced apoptosis by activation of PP2A through modulation of Akt/IKK/NF-κB pathway. In addition, CA induced apoptosis in another androgen refractory prostate cancer DU145 cells via intrinsic pathway as evidenced from the activation of caspase 3, cleavage of PARP, increase in Bax:Bcl-2 ratio and cytochrome-c release. Carnosic acid, therefore, may have the potential for use in the prevention and/or treatment of prostate cancer.

• Authors: Susanta Kar, Shreyasi Palit, Writoban Basu Ball, Pijush K Das
• Journal: Apoptosis : an international journal on programmed cell death (Apoptosis) Vol. 17 Issue 7 Pg. 735-47 (Jul 2012) ISSN: 1573-675X [Electronic] Netherlands
• PMID: 22453599 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Abietanes
• NF-kappa B
• Plant Extracts
• Proto-Oncogene Proteins c-akt
• I-kappa B Kinase
• Protein Phosphatase 2
• salvin

Topics

• Abietanes (pharmacology)
• Apoptosis (drug effects)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Down-Regulation (drug effects)
• Drug Screening Assays, Antitumor
• Enzyme Activation (drug effects)
• Humans
• I-kappa B Kinase (metabolism)
• Male
• NF-kappa B (metabolism)
• Plant Extracts (pharmacology)
• Prostatic Neoplasms (enzymology, pathology)
• Protein Phosphatase 2 (metabolism)
• Proto-Oncogene Proteins c-akt (metabolism)
• Signal Transduction (drug effects)