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A phytochemical investigation on the stems and leaves of Clausena emarginata led to the isolation of a previously undescribed carbazole alkaloid, clausemargine A (1), together with 11 known analogues (2–12). The structure of 1 was elucidated by extensive spectroscopic methods and the known compounds were identified by comparisons with data reported in the literature. All known compounds (2–12) were isolated from C. emarginata for the first time. All isolated compounds were evaluated for their their antiproliferative activities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480 in vitro. Compounds 1–12 showed significant antiproliferative effects with IC50 values ranging from 0.28 to 15.18 μM. [ABSTRACT FROM AUTHOR]

A phytochemical investigation on the stems and leaves of Clausena lenis led to the isolation of a new furanocoumarin, clauselenisin A (1), together with five known analogues (2–6). The structure of 1 was elucidated by extensive spectroscopic methods and the known compounds were identified by comparisons with data reported in the literature. All known compounds (2–6) were isolated from C. lenis for the first time. All isolated compounds were evaluated for their their antiproliferative activities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480 in vitro. Compounds 1–6 showed significant antiproliferative effects with IC50 values ranging from 0.36 to 16.48 μM. [ABSTRACT FROM AUTHOR]

Phytochemical investigation on the stems and leaves of Trigonostemon howii resulted in the isolation of a new abietane diterpenoid, trigohowimine A (1), along with seven known structurally diverse diterpenoids (2–8). The structure of 1 was elucidated by extensive spectroscopic methods and the known compounds were identified by comparison with data reported in the literature. New compound 1 was evaluated for its cytotoxicities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480. Compound 1 showed significant inhibitory effects against various human cancer cell lines with IC50 values ranging from 0.82 to 8.53 μM. [ABSTRACT FROM AUTHOR]

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), initially identified as a glycolytic enzyme and considered as a housekeeping gene, is widely used as an internal control in experiments on proteins, mRNA, and DNA. However, emerging evidence indicates that GAPDH is implicated in diverse functions independent of its role in energy metabolism; the expression status of GAPDH is also deregulated in various cancer cells. One of the most common effects of GAPDH is its inconsistent role in the determination of cancer cell fate. Furthermore, studies have described GAPDH as a regulator of cell death; other studies have suggested that GAPDH participates in tumor progression and serves as a new therapeutic target. However, related regulatory mechanisms of its numerous cellular functions and deregulated expression levels remain unclear. GAPDH is tightly regulated at transcriptional and posttranscriptional levels, which are involved in the regulation of diverse GAPDH functions. Several cancer-related factors, such as insulin, hypoxia inducible factor-1 (HIF-1), p53, nitric oxide (NO), and acetylated histone, not only modulate GAPDH gene expression but also affect protein functions via common pathways. Moreover, posttranslational modifications (PTMs) occurring in GAPDH in cancer cells result in new activities unrelated to the original glycolytic function of GAPDH. In this review, recent findings related to GAPDH transcriptional regulation and PTMs are summarized. Mechanisms and pathways involved in GAPDH regulation and its different roles in cancer cells are also described. [ABSTRACT FROM AUTHOR]

(20S) ginsenoside Rh2 (G-Rh2), a major bioactive metabolite of ginseng, effectively inhibits the survival and proliferation of human liver cancer cells. However, its molecular targets and working mechanism remain largely unknown. Excitingly, we screened out heat shock protein 90 alpha (HSP90A), a key regulatory protein associated with liver cancer, as a potential target of (20S) G-Rh2 by phage display analysis and mass spectrometry. The molecular docking and thermal shift analyses demonstrated that (20S) G-Rh2 directly bound to HSP90A, and this binding was confirmed to inhibit the interaction between HSP90A and its co-chaperone, cell division cycle control protein 37 (Cdc37). It is well-known that the HSP90A-Cdc37 system aids in the folding and maturation of cyclin-dependent kinases (CDKs). As expected, CDK4 and CDK6, the two G0-G1 phase promoting kinases as well as CDK2, a key G1-S phase transition promoting kinase, were significantly downregulated with (20S) G-Rh2 treatment, and these downregulations were mediated by the proteasome pathway. In the same condition, the cell cycle was arrested at the G0-G1 phase and cell growth was inhibited significantly by (20S) G-Rh2 treatment. Taken together, this study for the first time reveals that (20S) G-Rh2 exerts its anti-tumor effect by targeting HSP90A and consequently disturbing the HSP90A-Cdc37 chaperone system. HSP90A is frequently overexpressed in human hepatoma cells and the higher expression is closely correlated to the poor prognosis of liver cancer patients. Thus, (20S) G-Rh2 might become a promising alternative drug for liver cancer therapy. [ABSTRACT FROM AUTHOR]

The novel compound JRS-15 was obtained through the chemical modification of xylocydine. JRS-15 exhibited much stronger cytotoxic and pro-apoptotic activity than its parent compound in various cancer cell lines, with IC50 values in HeLa, HepG2, SK-HEP-1, PC-3M and A549 cells ranging from 12.42 to 28.25 µM. In addition, it is more potent for killing cancer than non-cancerous cells. Mechanistic studies showed that JRS-15 treatment arrested cell cycle at the G1/S phase, which further triggered the translocation of Bax and Bak to the mitochondria, resulting in mitochondrial membrane potential (MMP) depolarization and the subsequent release of cytochrome c and the second mitochondria-derived activator of caspase (Smac). The sequential activation of caspase-9 and caspase-3/7 and the cleavage of poly (ADP-ribose) polymerase (PARP) were observed following these mitochondrial events. Caspase-8, an initiator caspase that is required to activate the membrane receptor-mediated extrinsic apoptosis pathway was not activated in JRS-15-treated cells. Further analysis showed that the levels of the anti-apoptotic proteins Bcl-xL and XIAP were significantly reduced upon JRS-15 treatment. Furthermore, the caspase-9 inhibitor z-LEHD-fmk, the pan-caspase inhibitor z-VAD-fmk, and Bcl-xL or XIAP overexpression all effectively prevented JRS-15-induced apoptosis. Taken together, these results indicate that JRS-15 induces cancer cell apoptosis by regulating multiple apoptosis-related proteins, and this compound may therefore be a good candidate reagent for anticancer therapy. [ABSTRACT FROM AUTHOR]

Aim: To generate a monoclonal antibody (McAb) against cell surface F1F0 AT P synthase (ATPase) and observe its antitumoral activity on both human umbilical vein endothelial cells (HUVEC) and tumor cells. Methods: Hybridoma cells secreting McAb against ATPase were produced by polyethylene glycol-mediated fusions and screened by ELISA. The specificity of McAb was demonstrated by immunofluorescence and confocal imaging, as well as flow cytometry analysis. After the blockade of surface ATPase with McAb on HUVEC and human breast adenocarcinoma MDA-MB-231 cells, an AT P determination kit and CellTiter96 AQueous Assay (MTS) assay were used to detect the effect of the antibody on extracellular ATP modification and cell proliferation. A cellular cytotoxicity assay in combination with doxorubicin, and a cell migration assay on MDA-MB-231 cells were used to determine the antitumoral activity. Finally, a HUVEC tube formation assay was used to detect the antiangiogenic effect of McAb178-5G10. Results: A monoclonal antibody (McAb178-5G10) against the β-subunit of ATPase was generated, and its reactivity toward HUVEC and tumor cells was studied. We demonstrate that McAb178-5G10 binds to ATPase at the cell surface, where it is able to inhibit AT P synthesis. This antibody also prevents the proliferation of HUVEC and MDA-MB-231 cells. Furthermore, McAb178-5G10 enhances the tumoricidal effects of doxorubicin ( P<0.05), inhibits the migration of MDA-MB-231 in transwell assays ( P<0.01), and disrupts HUVEC tube formation on Matrigel ( P<0.01). Conclusion: McAb178-5G10 binds preferentially to cell surface ATPase, blocks ATP synthesis, and exhibits both antiangiogenic and antitumorigenic effects. [ABSTRACT FROM AUTHOR]

Summary: Early-stage oral cancer patients may have distinct clinical outcomes and respond differently to the same treatment. Up to now, there is still no individual marker to identify such patients with poor outcome. Down-regulation of a tumor suppressor gene, S100A2, in oral cancer cells was identified by mRNA profiling analysis then confirmed by RT-PCR and Southern blotting. The expression of nuclear S100A2 protein examined by immunohistochemistry was not significantly associated with any patient characteristic among the 70 early-stage oral squamous cell carcinoma (SCC) patients. Intriguingly, the loss of nuclear S100A2 positivity was significantly associated with shorter disease-free survival (p =0.019) while having no effect on the overall survival of these patients. Cox regression analysis with backward elimination identified S100A2 (p =0.006), tobacco smoking (p =0.013), and betel quid chewing (p =0.019) as independent predictors of disease-free survival. This is a first study to demonstrate that loss of nuclear S100A2 may serve as an independent prognostic marker for early-stage oral cancer patients at high risk of recurrence. A more aggressive treatment modality and intensive follow-up may be recommended for the patients with reduced expression of S100A2 in tumor cell nuclei. [Copyright &y& Elsevier]

Little is known about the specificity of angiogenic properties of oral cancer cells and the possible mechanisms. Stimulatory effects on proliferation and migration of human umbilical vein endothelial cells (HUVEC) characterized the angiogenic properties of oral cancer cells but not normal oral keratinocytes (NOK). ELISA found the presence of vascular endothelial growth factors (VEGF) both in the tested oral cancer cells and NOK. Attenuation of the proangiogenic effects by neutralizing VEGF antibodies suggests VEGF play a key role in the acquisition of the angiogenic phenotype in oral cancer cells. Western blotting of p53 and murine double mutant 2 (Mdm2) together with p53 DNA sequencing analysis indicate that p53 function loss by mutation or overexpression of Mdm2 occurred in all tested oral cancer cells regardless of their etiology. In summary, the angiogenic property of oral cancer cells is mediated by many factors in addition to VEGF and the functional status of p53. [ABSTRACT FROM AUTHOR]

LNCaP cells are human prostatic cancer cells that have a frame-shift mutation of the tumor suppressor gene PTEN and do not express the insulin receptor substrate-1 (IRS-1), a major substrate of the type 1 insulin-like growth factor receptor (IGF-IR). Ectopic expression of IRS-1 in LNCaP cells increases cell adhesion and decreases cell motility by an IGF-I-independent mechanism. We show now that these effects of IRS-1 are accompanied by serine phosphorylation of IRS-1 and are inhibited by inhibitors of phosphatidylinositol 3-kinase (PI3K). We have confirmed the requirement for PI3K activity and serine phosphorylation by the use of IRS-1 mutants, expressed in LNCaP cells. Serine phosphorylation inhibits IGF-I-induced tyrosyl phosphorylation of IRS-1, which is restored by the expression of wild-type PTEN or by inhibition of PI3K activity. Finally, IRS-1 in LNCaP cells co-immunoprecipitates with integrin α 5 β 1, and the association is again IGF-I-independent. We conclude that in LNCaP cells, IRS-1 is serine phosphorylated by PI3K, generating effects that are different, and even opposite, from those generated by IGF-I. Oncogene (2001) 20, 490–500. [ABSTRACT FROM AUTHOR]

LNCaP prostatic cancer cells are characterized by having a PTEN mutation, low levels of type 1 insulin-like growth factor receptor (IGF-IR) and no IRS-1, one of the major substrates of the IGF-IR. The absence of IRS-1, an activator of PI3-kinase, is compensated in these cells by the mutation in PTEN, an inhibitor of PI3-kinase. However, IGF-IR signaling in the absence of IRS-1 can cause cell differentiation and growth arrest. We hypothesized that these three characteristics may not be unrelated, specifically that, together, they may favor the metastatic spread of prostatic cancer cells without decreasing their growth potential. In support of this hypothesis, we report here that: (1) IRS-1 expression increases cell adhesion and decreases cell motility; (2) over-expression of the IGF-IR, in the absence of IRS-1, causes growth arrest and (3) a combination of IGF-IR and IRS-1 restores the transformed phenotype of LNCaP cells. These findings suggest a mechanism by which prostatic cancer cells can achieve metastatic potential without interfering with their growth potential. Oncogene (2000) 19, 2687–2694 [ABSTRACT FROM AUTHOR]

Ginsenoside Rk1 and Rg5 are minor ginseng saponins that have received more attention recently because of their high oral bioavailability. Each of them can effectively inhibit the survival and proliferation of human liver cancer cells, but the underlying mechanism remains largely unknown. Network pharmacology and bioinformatics analysis demonstrated that G-Rk1 and G-Rg5 yielded 142 potential targets, and shared 44 putative targets associated with hepatocellular carcinoma. Enrichment analysis of the overlapped genes showed that G-Rk1 and G-Rg5 may induce apoptosis of liver cancer cells through inhibition of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signal pathways. Methyl thiazolyl tetrazolium (MTT) assay was used to confirm the inhibition of cell viability with G-Rk1 or G-Rg5 in highly metastatic human cancer MHCC-97H cells. We evaluated the apoptosis of MHCC-97H cells by using flow cytometry and 4′,6-diamidino-2-phenylindole (DAPI) staining. The translocation of Bax/Bak led to the depolarization of mitochondrial membrane potential and release of cytochrome c and Smac. A sequential activation of caspase-9 and caspase-3 and the cleavage of poly(ADP-ribose) polymerase (PARP) were observed after that. The levels of anti-apoptotic proteins were decreased after treatment of G-Rk1 or G-Rg5 in MHCC-97H cells. Taken together, G-Rk1 and G-Rg5 promoted the endogenous apoptotic pathway in MHCC-97H cells by targeting and regulating some critical liver cancer related genes that are involved in the signal pathways associated with cell survival and proliferation. [ABSTRACT FROM AUTHOR]

The aim of the present study was to verify the pro-apoptotic anticancer potential of several 5,8-dimethoxy-1,4-phthoquinone (DMNQ) derivatives in Ras-mediated tumorigenesis. MTT assays were used to detect cellular viability and flow cytometry was performed to assess intracellular reactive oxygen species (ROS) levels and apoptosis. The expression levels of proteins were detected via western blotting. Among the 12 newly synthesized DMNQ derivatives, 2-benzylthio-5,8-dimethoxynaphthalene-1,4-dione (BZNQ; component #1) significantly reduced cell viability both in mouse NIH3T3 embryonic fibroblasts cells (NC) and H-RasG12V transfected mouse NIH3T3 embryonic fibroblasts cells (NR). Moreover, BZNQ resulted in increased cytotoxic sensitivity in Ras-mutant transfected cells. Furthermore, the reactive oxygen species (ROS) levels in H-RasG12V transfected HepG2 liver cancer cells (HR) were significantly higher compared with the levels in HepG2 liver cancer cells (HC) following BZNQ treatment, which further resulted in increased cellular apoptosis. Eliminating cellular ROS using an ROS scavenger N-acetyl-L-cysteine markedly reversed BZNQ-induced cellular ROS accumulation and cell apoptosis in HC and HR cells. Western blotting results revealed that BZNQ significantly downregulated H-Ras protein expression and inhibited the Ras-mediated downstream signaling pathways such as protein kinase B, extracellular signal-related kinase and glycogen synthase kinase phosphorylation and β-catenin protein expression. These results indicated that the novel DMNQ derivative BZNQ may be a therapeutic drug for Ras-mediated liver tumorigenesis. The results of the current study suggest that BZNQ exerts its effect by downregulating H-Ras protein expression and Ras-mediated signaling pathways. [ABSTRACT FROM AUTHOR]

Proliferating cell nuclear antigen (PCNA) is a nuclear protein synthesized in the late G1 and S phase of the cell cycle which can be detected immunohistochemically in paraffin-embedded tissue as a useful marker for the proliferating fraction of cells in tissue specimens. Thirty-eight cases of oral squamous cell carcinoma were studied in groups according to clinical staging and histological grading (UICC system), these included 5 cases of T1, 13 cases of T2, and 20 cases of T3, and 19 cases of Gl, 12 cases of G2, and 7 cases of G3. The mean percentage of PCNA positively stained tumor cells in this series was 29.2. The mean percentages of PCNA-positive cells in each stage and grade were: T1 (13.7%), T2 (24.4%), and T3 (34.3%); GI (30.5%), G2 (24.8%), and G3 (33.2%). The results indicate that the percentage of PCNA positively stained tumor cells in oral squamous cell carcinoma was significantly greater when tumor size was larger than 2 cm (T1 versus T2/T3). However, there was no significant difference between T2 and T3. There was no correlation between the number of PCNA- stained tumor cells and histological grade. [ABSTRACT FROM AUTHOR]

Backgrounds: Tamoxifen is typically used to treat patients with estrogen receptor alpha (ERα)-positive breast cancer. However, 30% of these patients gain acquired resistance to tamoxifen during or after tamoxifen treatment. As a Ras modulator, Nogo-B receptor (NgBR) is required for tumorigenesis through the signaling crosstalk with epidermal growth factor (EGF) receptor (EGFR)-mediated pathways. NgBR is highly expressed in many types of cancer cells and regulates the sensitivity of hepatocellular carcinoma to chemotherapy. In this study, we found the expression of NgBR is increased in tamoxifen-resistant ERα-positive breast cancer cells.Methods: Tamoxifen-resistant ERα-positive MCF-7 and T47D breast cancer cell lines were established by culturing with gradually increased concentration of 4-hydroxytamoxifen (4-OHT). The effects of NgBR on tamoxifen resistance was determined by depleting NgBR in these cell lines using previously validated small interfering RNA (siRNA). The effects of 4-OHT on cell viability and apoptosis were determined using well-accepted methods such as clonogenic survival assay and Annexin V/propidium iodide staining. The alteration of EGF-stimulated signaling and gene expression was determined by western blot analysis and real-time PCR, respectively.Results: NgBR knockdown with siRNA attenuates EGF-induced phosphorylation of ERα and restores the sensitivity to tamoxifen in ERα-positive breast cancer cells. Mechanistically, our data demonstrated that NgBR knockdown increases the protein levels of p53 and decreases survivin, which is an apoptosis inhibitor.Conclusions: These results suggested that NgBR is a potential therapeutic target for increasing the sensitivity of ERα-positive breast cancer to tamoxifen. [ABSTRACT FROM AUTHOR]

Two novel γ -lactone derivatives, trigoheterophines A ( 1 ) and B ( 2 ), together with four known furan derivatives ( 3 – 6 ), were isolated from the stems and leaves of Trigonostemon heterophyllus . The structures of 1 and 2 were elucidated by extensive spectroscopic methods and the known compounds were identified by comparing with the data reported in literature. Among them, trigoheterophines A ( 1 ) and B ( 2 ) represent an unusual type of γ -lactone derivatives, possessing 21 carbon atoms on the carbon skeleton, and known compouds ( 3 – 6 ) are rare furan derivatives in the plant kingdom with diverse long-chain hydrocarbyl groups as substituents at C-4. All isolated compounds were evaluated for their antiproliferative activities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480 in vitro . Compounds 1 – 6 showed significant antiproliferative effects against various human cancer cell lines with IC 50 values ranging from 0.28 to 12.06 μM. These findings suggest that the discoveries of these novel γ -lactone derivatives and furan derivatives with significant antiproliferative activities isolated from T. heterophyllus could be of great importance to the development of new anticancer agents. [ABSTRACT FROM AUTHOR]