title: 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.affiliation: Molecular Cell Biology Laboratory, Infectious Disease and Immunology Division, Indian Institute of Chemical Biology, Kolkata, India.
authors.forename: Susanta
authors.initials: S
authors.lastname: Kar
authors.forename: Shreyasi
authors.initials: S
authors.lastname: Palit
authors.forename: Writoban Basu
authors.initials: WB
authors.lastname: Ball
authors.forename: Pijush K
authors.initials: PK
authors.lastname: Das
mesh_terms: D045784:Abietanes / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000473:pathology*; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D045784:Abietanes; D016328:NF-kappa B; D010936:Plant Extracts; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; D054648:Protein Phosphatase 2; C018381:salvin