santalol and Prostatic-Neoplasms

Previous studies have shown that the sandalwood oil constituent α-santalol inhibits growth of cultured human prostate cancer cells in vitro and PC-3 prostate cancer xenografts. Along with the studies from our laboratory, it is well established that α-santalol targets the phosphatidylinositol-4,5-bisphosphate 3-kinase-AKT serine/ threonine kinase 1 (AKT) pathway to induce apoptosis but its growth-suppressive effects have not been fully elucidated. The current study was undertaken to investigate the role of autophagy in α-santalol-induced prostate cancer cell death.. Cell lines LNCaP and PC-3 were maintained in an atmosphere of 95% air and 5% CO2 at 37°C. Trypan blue dye exclusion assay was employed to assess the effects of α-santalol with/without 3-methyl adenine on the cell viability of prostate cancer cells. Acidic vesicular organelles induced by α-santalol treatment were detected by staining with acridine orange. Immunofluorescence and immunoblotting were performed to analyze expression of proteins involved in the AKT-mammalian target of rapamycin (mTOR) pathway.. LNCaP and PC-3 cells upon treatment with α-santalol resulted in characteristic features analogous to autophagic response, including formation of acidic vesicular organelles, recruitment and cleavage of microtubule-associated protein 1 light chain 3 (LC3) to autophagosomes. Alpha-santalol treatment further suppressed phosphorylation of activated AKT and mTOR, which are critical regulators of autophagic response. In addition, pre-treatment of PC-3 cells with specific inhibitor of autophagy (3-methyladenine) and co-treatment with α-santalol attenuated the expression of LC3-II and phospho-AKT, and significantly reduced the cell viability.. The present study indicates that α-santalol induces autophagy by targeting the AKT-mTOR pathway in prostate cancer cells, which may serve as a protective mechanism.

Topics: Adenine; Apoptosis; Autophagy; Cell Line, Tumor; Humans; Male; Microtubule-Associated Proteins; Phosphorylation; Polycyclic Sesquiterpenes; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Signal Transduction; TOR Serine-Threonine Kinases

We have shown previously that alpha-santalol, a major component of sandalwood oil inhibits growth of cultured prostate cancer cells in vitro by causing apoptosis, but the mechanism of cell death is not fully elucidated. The present study was undertaken to investigate the role of PI3K/Akt/survivin pathway in alpha-santalol-induced apoptosis employing cultured LNCaP and PC-3 human prostate cancer cells. Treatment of prostate cancer cells with alpha-santalol (20, 40 μM) resulted in the down regulation of survivin and p-AKT (s-473) expression and statistically significant reduction in total survivin levels as evidenced by survivin ELISA assay. Furthermore, inhibition of PI3K-Akt pathway by pharmacological inhibitor, LY294002 enhanced the apoptotic cell death induced by alpha-santalol as determined by cell viability, cellular morphology, active caspase-3 activity and expression of cleaved PARP, cleaved caspase-3 levels. In conclusion, the present study provides novel insight into the molecular circuitry of alpha-santalol-induced cell death and reveals that alpha-santalol targets Akt/Survivin pathway to induce cell death and that the cell death is increased in the presence of a known inhibitor of the pathway.

Topics: Apoptosis; Caspase 3; Cell Line, Tumor; Humans; Male; PC-3 Cells; Phosphatidylinositol 3-Kinases; Plant Oils; Polycyclic Sesquiterpenes; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Sesquiterpenes; Signal Transduction; Survivin

VEGF receptor 2 (VEGFR2) inhibitors, as efficient antiangiogenesis agents, have been applied in the cancer treatment. However, recently, most of these anticancer drugs have some adverse effects. Discovery of novel VEGFR2 inhibitors as anticancer drug candidates is still needed.. We used α-santalol and analyzed its inhibitory effects on human umbilical vein endothelial cells (HUVECs) and Prostate tumor cells (PC-3 or LNCaP) in vitro. Tumor xenografts in nude mice were used to examine the in vivo activity of α-santalol.. α-santalol significantly inhibits HUVEC proliferation, migration, invasion, and tube formation. Western blot analysis indicated that α-santalol inhibited VEGF-induced phosphorylation of VEGFR2 kinase and the downstream protein kinases including AKT, ERK, FAK, Src, mTOR, and pS6K in HUVEC, PC-3 and LNCaP cells. α-santalol treatment inhibited ex vivo and in vivo angiogenesis as evident by rat aortic and sponge implant angiogenesis assay. α-santalol significantly reduced the volume and the weight of solid tumors in prostate xenograft mouse model. The antiangiogenic effect by CD31 immunohistochemical staining indicated that α-santalol inhibited tumorigenesis by targeting angiogenesis. Furthermore, α-santalol reduced the cell viability and induced apoptosis in PC-3 cells, which were correlated with the downregulation of AKT, mTOR and P70S6K expressions. Molecular docking simulation indicated that α-santalol form hydrogen bonds and aromatic interactions within the ATP-binding region of the VEGFR2 kinase unit.. α-santalol inhibits angiogenesis by targeting VEGFR2 regulated AKT/mTOR/P70S6K signaling pathway, and could be used as a potential drug candidate for cancer therapy.

Topics: Angiogenesis Inhibitors; Animals; Apoptosis; Cell Line, Tumor; Cell Proliferation; Gene Expression Regulation, Neoplastic; Human Umbilical Vein Endothelial Cells; Humans; Male; Mice; Mice, Nude; Models, Molecular; Molecular Docking Simulation; Molecular Targeted Therapy; Neovascularization, Pathologic; Polycyclic Sesquiterpenes; Prostate; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Rats; Sesquiterpenes; Signal Transduction; Vascular Endothelial Growth Factor Receptor-2; Xenograft Model Antitumor Assays

The anticancer effects of α-santalol, a major component of sandalwood oil, have been reported against the development of certain cancers such as skin cancer both in vitro and in vivo. The primary objectives of the current study were to investigate the cancer preventive properties of α-santalol on human prostate cancer cells PC-3 (androgen independent and P-53 null) and LNCaP (androgen dependent and P-53 wild-type), and determine the possible mechanisms of its action. The effect of α-santalol on cell viability was determined by trypan blue dye exclusion assay. Apoptosis induction was confirmed by analysis of cytoplasmic histone-associated DNA fragmentation using both an apoptotic ELISA kit and a DAPI fluorescence assay. Caspase-3 activity was determined using caspase-3 (active) ELISA kit. PARP cleavage was analyzed using immunoblotting. α-Santalol at 25-75 μM decreased cell viability in both cell lines in a concentration and time dependent manner. Treatment of prostate cancer cells with α-santalol resulted in induction of apoptosis as evidenced by DNA fragmentation and nuclear staining of apoptotic cells by DAPI. α-Santalol treatment also resulted in activation of caspase-3 activity and PARP cleavage. The α-santalol-induced apoptotic cell death and activation of caspase-3 was significantly attenuated in the presence of pharmacological inhibitors of caspase-8 and caspase-9. In conclusion, the present study reveals the apoptotic effects of α-santalol in inhibiting the growth of human prostate cancer cells.

Topics: Androgens; Antineoplastic Agents, Phytogenic; Apoptosis; Caspase 3; Caspase 8; Caspase 9; Cell Line, Tumor; Cell Survival; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Humans; Male; Plant Oils; Poly(ADP-ribose) Polymerases; Polycyclic Sesquiterpenes; Prostatic Neoplasms; Sesquiterpenes