Apoptosis, also called programmed cell death, is morphologically characterized by cell shrinkage, membrane remodeling, cell blebbing, chromatin condensation and DNA fragmentation with apoptotic bodies.1-3) Apoptosis activation has been considered a good target in cancer therapies. 4,5) In general, apoptosis is regulated by pro-apoptotic and antiapoptotic proteins of the Bcl-2 family and executed through caspases (or cysteine-aspartic proteases), chiefly via two major and inter-related pathways, i.e., the mitochondria-dependent "intrinsic" cytochrome c/caspase-9 pathway and the death receptor-mediated "extrinsic" caspase-8 pathway. [6][7][8] Additionally, apoptosis is controlled by various cell signaling pathways such as the phosphoinositide 3-kinase (PI3K)/AKT survival pathway, regulating apoptosis chiefly by blocking caspase-9 and the mitochondria damaging Bcl-2 family protein, Bad, through phosphorylative inactivation. 9)Tanshinone IIA (Tan IIA,14,6,8,13, Fig. 1A), one of the phytochemical compounds isolated from the Chinese medicinal herb Danshen (root of Salvia miltiorrhiza BUNGE), has been reported to exert diverse biological properties including anti-oxidative, 3,10,11) anti-angiogenic, 12) and anti-inflammatory activities.13) More importantly, anti-cancer activities have been reported including human hepatoma, [14][15][16][17] breast cancer 18) and leukemia. 19) However, there is no report of anticancer activity of Tan IIA on prostate cancer cells. Thus, in the present study, we investigated the cytocidal/apoptosis effect against prostate cancer cell lines of different pathogenetic make-up: LNCaP (p53 null, phosphate and tensin homolog (PTEN) null-high AKT, androgen sensitive) and PC-3 (p53 null, PTEN null-high AKT, androgen receptor null). Our mechanistic investigations suggested an involvement of mitochondria-intrinsic caspase activation cascade and inhibition of PI3K/AKT pathway. MATERIALS AND METHODSTanshinone IIA Isolation The procedure of Tan IIA (Fig. 1A) isolation is as reported by Choi and colleagues. 20)Cell Culture Human prostate cancer cells LNCaP (ATCC CRL 1740, p53 wild type, PTEN mutant-high AKT) and PC3 (ATCC CRL 1435, p53 null, PTEN null-high AKT), and breast cancer cells MDA-MB-231 (ATCC HTB 26, p53 mutant, wild type PTEN-low AKT) were obtained from American Type Culture Collection (ATCC) and maintained in RPMI 1640 supplemented with 10% fetal bovine serum (FBS) and 2 mmol/l L-glutamine, 10 mmol/l N-(2-hydroxyethyl)piperazine-NЈ-2-ethanesulfonic acid (HEPES), 1 mmol/l sodium pyruvate, and 4.5% D-glucose without antibiotics.Cytotoxicity Assay The cytotoxicity of Tan IIA was assessed by a tetrazolium salt, 2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) assay. LNCaP or PC3 cells were seeded onto 96-well microplates at a density of 1ϫ10 4 cells per well in 100 ml of complete medium. After incubation for 24 h, cells were exposed to var- IIA; 14,16-epoxy-20-nor-5(10),6,8,13,15-abietapentaene-11,12-dione), a phytochemical derived from the roots of Salvia miltio...

AR targeting action of tanshinones was distinct from Casodex and contributed to prostate cancer growth suppression in vitro and in vivo.

Our group previously reported that tanshinone IIA induced apoptosis via a mitochondria dependent pathway in LNCaP prostate cancer cells. In the present study, the roles of androgen receptor (AR) and p53 signaling pathways were investigated in tanshinone IIA-induced G1 arrest in LNCaP cells. Tanshinone IIA significantly inhibited the growth and proliferation of LNCaP cells by colony formation and BrdU incorporation assays, respectively. Tanshinone IIA induced cell cycle arrest at G1 phase and down-regulated cyclin D1, CDK2 and CDK4. Furthermore, tanshinone IIA activated the phosphorylation of p53 at Ser 15 residue and its downstream p21 and p27. Additionally, tanshinone IIA suppressed the expression of AR and prostate specific antigen (PSA). Conversely, silencing p53 using its specific siRNA reversed cyclin D1 expression inhibited by tanshinone IIA. However, knockdown of AR had no effect on the p53/p21/p27 signaling pathway activated by tanshinone IIA in LNCaP cells. In AR siRNA-transfected cells, tanshinone IIA did not cause cell cycle arrest and reduce cyclin D1, implying that AR is essential to induce G1 arrest by tanshinone IIA in LNCaP cells. Taken together, the findings suggest that tanshinone IIA induces G1 arrest via activation of p53 signaling and inhibition of AR in LNCaP cells.

Baicalein is a flavonoid (5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran4-one) and an active principle in Scutellaria baicalensis. The present study was performed to investigate the mechanisms underlying the antifibrotic effects of baicalein with a focus on Rho kinase (ROCK) inhibition. The effect of baicalein on ROCK activity was analyzed using an immobilized metal affinity for phosphochemicals (IMAP)-based time-resolved fluorescence resonance energy transfer (TR-FRET) assay. The underlying mechanisms of baicalein were examined using angiotensin II-stimulated H9c2 cells. Rho kinase (ROCK1 and ROCK2) studies using IMAP-TR-FRET showed that baicalein possesses potent ROCK inhibitory activity with IC 50 values of 6.55 and 2.82 µM, respectively. Pretreatment with baicalein (for 2 h) concentration-dependently decreased the angiotensin II-induced phosphorylation of myosin phosphatase (MYPT) and myosin light chain (MLC). Furthermore, baicalein also concentration-dependently suppressed actin stress fiber formation in angiotensin II-stimulated H9c2 cells. These results suggest that baicalein potently inhibits ROCK and that by so doing it modulates actin stress fiber formation. These anti-fibrotic effects of baicalein explain, at least in part, its pharmacology and mode of action.