acacetin and Prostatic-Neoplasms

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in the formation and growth of human cancer. Therefore, STAT3 is a therapeutic target for cancer drug discovery. Acacetin, a flavone present in various plants, inhibits constitutive and inducible STAT3 activation in STAT3-activated DU145 prostate cancer cells. Acacetin inhibits STAT3 activity by directly binding to STAT3, which we confirmed by a pull-down assay with a biotinylated compound and two level-free methods, namely, a drug affinity responsive target stability (DARTS) experiment and a cellular thermal shift assay (CETSA). Acacetin inhibits STAT3 phosphorylation at the tyrosine 705 residue and nuclear translocation in DU145 cells, which leads to the downregulation of STAT3 target genes. Acacetin then induces apoptosis in a time-dependent manner. Interestingly, acacetin induces the production of reactive oxygen species (ROS) that are not involved in the acacetin-induced inhibition of STAT3 activation because the suppressed p-STAT3 level is not rescued by treatment with GSH or NAC, which are general ROS inhibitors. We also found that acacetin inhibits tumor growth in xenografted nude mice. These results suggest that acacetin, as a STAT3 inhibitor, could be a possible drug candidate for targeting STAT3 for the treatment of cancer in humans.

Topics: Animals; Antineoplastic Agents, Phytogenic; Apoptosis; Cell Line, Tumor; Cell Proliferation; Female; Flavones; Gene Expression; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Models, Molecular; Phosphorylation; Prostatic Neoplasms; Protein Binding; Protein-Tyrosine Kinases; Reactive Oxygen Species; STAT3 Transcription Factor; Xenograft Model Antitumor Assays

Acacetin (5,7-dihydroxy-4'-methoxyflavone) is a flavonoid compound with antimutagenic, antiplasmodial, antiperoxidant, anti-inflammatory and anticancer effects. However, the molecular targets and pathways underlying the anticancer effects of acacetin are yet to be elucidated. In this study, we investigated whether acacetin induces apoptosis in the human prostate cancer cell line, DU145. The results of 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays revealed that cell viability decreased in a dose- and time-dependent manner in response to acacetin. 4',6-Diamidino-2-phenylindole (DAPI) staining revealed that chromatin condensation significantly increased in a dose-dependent manner. Flow cytometric analysis indicated that acacetin suppressed the viability of DU145 cells by inducing apoptosis. Western blot anlaysis of various markers of signaling pathways revealed that acacetin targets the Akt and nuclear factor (NF)-κB signaling pathways by inhibiting the phosphorylation of IκBα and NF-κB in a dose-dependent manner. Consistent with its ability to induce apoptosis, the acacetin-mediated inhibition of the pro-survival pathway, Akt, and of the NF-κB pathway was accompanied by a marked reduction in the levels of the NF-κB‑regulated anti-apoptotic proteins, Bcl-2 and X-linked inhibitor of apoptosis protein (XIAP), as well as of the proliferative protein, cyclooxygenase (COX)-2. We further evaluated the effects of acacetin on prostate cancer using mice subcutaneously injected with DU145 prostate cancer cells. The acacetin-treated nude mice bearing DU145 tumor xenografts exhibited significantly reduced tumor size and weight, due to the effects of acacetin on cancer cell apoptosis, as determined by terminal deoxyribonucleotide transferase-mediated dUTP nick end-labeling (TUNEL) assay. Our findings suggest that acacetin exerts antitumor effects by targeting the Akt/NF-κB signaling pathway. Rurther investigations on this flavonoid are warranted to evaluate its potential use in the prevention and therapy of prostate cancer.

Topics: Animals; Antineoplastic Agents, Phytogenic; Apoptosis; bcl-2-Associated X Protein; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclooxygenase 2; Disease Models, Animal; Dose-Response Relationship, Drug; Flavones; Humans; Male; Mice; Mice, Nude; NF-kappa B; Phosphorylation; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Signal Transduction; X-Linked Inhibitor of Apoptosis Protein

Acacetin (5,7-dihydroxy-4'-methoxyflavone), a flavonoid compound, has anti-peroxidative and anti-inflammatory effects. The effect of acacetin on antimetastasis in human prostate cancer DU-145 cells was investigated. First, the result demonstrated acacetin could exhibit an inhibitory effect on the abilities of the adhesion, invasion, and migration by cell-matrix adhesion assay, wound-healing assay, and Boyden chamber assay. Data also showed acacetin could inhibit the phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) involved in the downregulation of the expressions of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), and urokinase-type plasminogen activator (u-PA) at both the protein and mRNA levels. Next, acacetin significantly decreased the nuclear levels of nuclear factor kappa B (NF-kappaB), c-Fos, and c-Jun. Also, the treatment with acacetin to DU145 cells also leads to a dose-dependent inhibition on the binding ability of NF-kappaB and activator protein-1 (AP-1). Furthermore, the treatment of inhibitors specific for p38 MAPK (SB203580) to DU145 cells could cause reduced expressions of MMP-2, MMP-9, and u-PA. These results showed acacetin could inhibit the invasion and migration abilities of DU145 cells by reducing MMP-2, MMP-9, and u-PA expressions through suppressing p38 MAPK signaling pathway and inhibiting NF-kappaB- or AP-1-binding activity. These findings proved acacetin might be offered further application as an antimetastatic agent.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cell Movement; Flavones; Flavonoids; Humans; Male; Matrix Metalloproteinases; Neoplasm Invasiveness; Neoplasm Metastasis; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Prostatic Neoplasms; RNA, Messenger; Signal Transduction; Urokinase-Type Plasminogen Activator

This study was carried out to assess the anticancer efficacy of linarin (LN), linarin acetate (LA) and acacetin (AC), the flavonoid compounds with the same flavone ring structure but different substitution, against human prostate cancer (PCA), LNCaP and DU145 cells. LN was isolated and purified from Chrysanthemum zawadskii; LA was chemically synthesized from LN, and AC obtained commercially. In each case, the cells were treated with these agents at 25-100 microM doses for 24-72 h. LN and LA showed moderate cell growth inhibition with different time kinetics as compared to AC. LN caused up to a 5-fold increase in cell death and LA enhanced cell death by up to 4-fold with the increase in treatment time in both cell lines. AC showed a time- as well as dose-dependent stronger cell growth inhibition (20-70%) accompanied by cell death as compared to LN and LA in both the cell lines. LN or LA did not show any profound effect on cell cycle arrest except for a moderate G1 arrest, whereas, AC showed a stronger G1 and/or G2-M arrest depending on the doses and treatment times. G1 arrest was associated with an increase in Cip1/p21 and a decrease in CDK2, CDK4 and CDK6 protein levels. G2-M arrest was associated with a decrease in Cdc25C, Cdc2/p34 and cyclin B1, which were more prominent in LNCaP compared to DU145 cells. LN, LA and AC induced cell death was associated with significant increase in apoptosis induction (up to 5-6-fold) accompanied by poly-(ADP-ribose) polymerase cleavage. Overall, AC showed more potent anticancer efficacy among these three flavonoids, which was diminished when its flavone ring was modified by disaccharide rhamnose substitution at C7 (LN) or acetylation of this substituted group (LA). These findings, for the first time, revealed the structural determinants in anticancer efficacy and mechanisms of these three flavonoids against human PCA cells.

Topics: Apoptosis; Cell Cycle; Cell Cycle Proteins; Cell Proliferation; Chrysanthemum; Flavones; Glycosides; Humans; Male; Poly(ADP-ribose) Polymerases; Prostatic Neoplasms; Rhamnose; Structure-Activity Relationship; Tumor Cells, Cultured