gambogic-acid and Prostatic-Neoplasms

Regulator of G Protein Signaling (RGS) 17 is an overexpressed promoter of cancer survival in lung and prostate tumors, the knockdown of which results in decreased tumor cell proliferation in vitro. Identification of drug-like molecules inhibiting this protein could ameliorate the RGS17's pro-tumorigenic effect. Using high-throughput screening, a chemical library containing natural products was interrogated for inhibition of the RGS17-Gα

Topics: Benzophenanthridines; Biological Products; Cytostatic Agents; Cytotoxins; GTP-Binding Protein Regulators; Humans; Isoquinolines; Lung Neoplasms; Male; Molecular Structure; Pentacyclic Triterpenes; Prostatic Neoplasms; Triterpenes

To study the effect of silencing pyruvate kinase M2 (PKM2) on gambogic acid (GA)-induced apoptosis of human prostate cancer PC3 cells.. Three specific PKM2 siRNAs and one negative control siRNA (si-NC) were transfected into PC3 cells. The silencing effect of PKM2 siRNAs was determined by real-time fluorescence quantitative PCR (qRT-PCR) and Western blot, and the effects of PKM2 siRNA on the vitality and apoptosis of GA-stimulated PC3 cells detected by MTT and AO/EB double staining, respectively. The mRNA and protein levels of c-myc and cyclin D1 were analyzed by qRT-PCR and Western blot, respectively.. All the 3 PKM2 siRNAs effectively reduced the mRNA and protein expressions of PKM2, and PKM2 siRNA-1 exhibited the strongest silencing effect. At 24 h after transfection, the expression levels of PKM2 mRNA and protein were reduced by 70% and 85%, respectively (P < 0.05). Twenty-four hours of treatment with GA (0.5 micromol/L) following transfection with PKM2 siRNA-1 inhibited the vitality of the PC3 cells by 68%, increased their apoptosis, and significantly down-regulated the mRNA and protein levels of c-myc (50% and 35%) and cyclin D1 (60% and 20%) (P < 0.05).. Inhibition of PKM2 sensitized PC3 cells to GA-induced apoptosis, suggesting that PKM2 may be a potential therapeutic target for sensitizing human prostate cancer to GA.

Topics: Apoptosis; Carrier Proteins; Cell Line, Tumor; Humans; Male; Membrane Proteins; Prostatic Neoplasms; RNA Interference; RNA, Small Interfering; Thyroid Hormone-Binding Proteins; Thyroid Hormones; Xanthones

To investigate the mechanisms underlying the inhibitory effect of gambogic acid (GA) on TNF-α-induced metastasis of human prostate cancer PC3 cells in vitro.. TNF-α-mediated migration and invasion of PC3 cells was examined using migration and invasion assays, respectively. NF-κB transcriptional activity and nuclear translocation were analyzed with luciferase reporter gene assays, immunofluorescence assays and Western blots. The ability of p65 to bind the promoter of Snail, an important mesenchymal molecular marker, was detected using a chromatin immunoprecipitation (ChIP) assay. After treatment with Snail-specific siRNA, the expression of invasiveness-associated genes was measured using quantitative real-time PCR and Western blot.. GA significantly inhibited the viability of PC3 cells at 1-5 μmol/L, but did not produce cytotoxic effect at the concentrations below 0.5 μmol/L. GA (0.125-0.5 μmol/L) dose-dependently inhibited the migration and invasion of PC3 cells induced by TNF-α (10 ng/mL). Moreover, the TNF-α-mediated activation of phosphatidylinositol-3-OH kinase/protein kinase B (PI3K/Akt) and NF-κB pathways was suppressed by GA (0.5 μmol/L). Furthermore, this anti-invasion effect of GA was associated with regulation of Snail. Snail expression was significantly down-regulated by treatment with GA (0.5 μmol/L) in the TNF-α-stimulated PC3 cells.. GA inhibits TNF-α-induced invasion of PC3 cells via inactivation of the PI3K/Akt and NF-κB signaling pathways, which may offer a novel approach for the treatment of human prostate cancer.

Topics: Antineoplastic Agents, Phytogenic; Cell Line, Tumor; Cell Movement; Garcinia; Humans; Male; Neoplasm Invasiveness; NF-kappa B; Phosphatidylinositol 3-Kinases; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Signal Transduction; Tumor Necrosis Factor-alpha; Xanthones

The transcription factor, STAT3, is associated with proliferation, survival, and metastasis of cancer cells. We investigated whether gambogic acid (GA), a xanthone derived from the resin of traditional Chinese medicine, Garcinia hanburyi (mangosteen), can regulate the STAT3 pathway, leading to suppression of growth and sensitization of cancer cells. We found that GA induced apoptosis in human multiple myeloma cells that correlated with the inhibition of both constitutive and inducible STAT3 activation. STAT3 phosphorylation at both tyrosine residue 705 and serine residue 727 was inhibited by GA. STAT3 suppression was mediated through the inhibition of activation of the protein tyrosine kinases Janus-activated kinase 1 (JAK1) and JAK2. Treatment with the protein tyrosine phosphatase (PTP) inhibitor pervanadate reversed the GA-induced downregulation of STAT3, suggesting the involvement of a PTP. We also found that GA induced the expression of the PTP SHP-1. Deletion of the SHP-1 gene by siRNA suppressed the ability of GA to inhibit STAT3 activation and to induce apoptosis, suggesting the critical role of SHP-1 in its action. Moreover, GA downregulated the expression of STAT3-regulated antiapoptotic (Bcl-2, Bcl-xL, and Mcl-1), proliferative (cyclin D1), and angiogenic (VEGF) proteins, and this correlated with suppression of proliferation and induction of apoptosis. Overall, these results suggest that GA blocks STAT3 activation, leading to suppression of tumor cell proliferation and induction of apoptosis.

Topics: Apoptosis; Blotting, Western; Breast Neoplasms; Carcinoma, Squamous Cell; Cell Proliferation; DNA, Neoplasm; Electrophoretic Mobility Shift Assay; Female; Head and Neck Neoplasms; Humans; Immunoenzyme Techniques; Janus Kinase 1; Janus Kinase 2; Male; Multiple Myeloma; Phosphorylation; Prostatic Neoplasms; Protein Transport; Protein Tyrosine Phosphatase, Non-Receptor Type 6; RNA, Small Interfering; STAT3 Transcription Factor; Tumor Cells, Cultured; Xanthones

Gambogic acid (GA), the main active compound of Gamboge hanburyi, has been previously reported to activate apoptosis in many types of cancer cell lines by targeting transferrin receptor and modulating nuclear factor-kappaB signaling pathway. Whether GA inhibits angiogenesis, which is crucial for cancer and other human diseases, remains unknown. Here, we found that GA significantly inhibited human umbilical vascular endothelial cell (HUVEC) proliferation, migration, invasion, tube formation, and microvessel growth at nanomolar concentration. In a xenograft prostate tumor model, we found that GA effectively inhibited tumor angiogenesis and suppressed tumor growth with low side effects using metronomic chemotherapy with GA. GA was more effective in activating apoptosis and inhibiting proliferation and migration in HUVECs than in human prostate cancer cells (PC3), suggesting GA might be a potential drug candidate in cancer therapy through angioprevention with low chemotoxicity. Furthermore, we showed that GA inhibited the activations of vascular endothelial growth factor receptor 2 and its downstream protein kinases, such as c-Src, focal adhesion kinase, and AKT. Together, these data suggest that GA inhibits angiogenesis and may be a viable drug candidate in antiangiogenesis and anticancer therapies.

Topics: Animals; Apoptosis; Cell Growth Processes; Cell Line, Tumor; Cell Movement; Endothelial Cells; Humans; Male; Mice; Mice, SCID; Neovascularization, Pathologic; Prostatic Neoplasms; Signal Transduction; Vascular Endothelial Growth Factor Receptor-2; Xanthones; Xenograft Model Antitumor Assays