Detection of poly(ADP-ribose) polymerase cleavage in response to treatment with topoisomerase I inhibitors: a potential surrogate end point to assess treatment effectiveness.

Cleavage of poly(ADP-ribose) polymerase (PARP) by caspases is a prominent characteristic of apoptosis or programmed cell death shown to be induced by topoisomerase (Topo) inhibitors. Because Topo I inhibitors have been shown to be effective in the treatment of some patients with colon cancer, we considered the possibility of using PARP cleavage as an early predictor of responsiveness to this class of agents. We show cleavage of PARP in response to treatment with Topo I inhibitors in colon cancer both in vitro and in vivo: (a) in vitro in SW480, HCT116, VACO5, VACO6, VACO8, VACO411, VACO425, and VACO451 human colon cancer cell lines treated with topotecan (TPT) or CPT-11; (b) in vivo in SW480, VACO451, and VRC5 colon cancer xenografts grown in athymic mice treated with TPT or CPT-11; and (c) in vivo in colon cancer samples from patients undergoing a Phase II clinical trial with CPT-11. Our results show a strong correlation between percentage of PARP cleavage and percentage of acridine orange-positive cells in colon cancer cell lines treated with 0.1 microM TPT for 24 and 48 h, confirming that PARP cleavage is a useful marker for programmed cell death in colon cancer cell lines. Results from experiments performed on colon cancer xenografts also show an association between PARP cleavage and response to treatment with TPT or CPT-11. The increase of PARP cleavage in xenografts and in clinical samples corresponding to treatment with Topo I inhibitors suggests that this procedure may have early predictive value to assess effectiveness of treatment. These results provide the basis for determining the validity of using PARP cleavage as an early marker of chemotherapeutic effectiveness in human samples.     

Piplartine induces caspase-mediated apoptosis in PC-3 human prostate cancer cells

The present study examined the anti-proliferative effects of piplartine on the human prostate cancer cell line PC-3. This is the first report demonstrating the piplartine anti-cancer activity toward prostate cancer cell lines, although its precise mechanism of action is still not completely defined. In MTT assays, it preferentially inhibited growth of androgen-independent PC-3 cells in a dose-dependent (3-30 microM) and time-dependent (12-48 h) manner. In PC-3 cells, it showed an IC50 of 15 microM after 24 h of treatment. After a 24-30 microM treatment for 24 h, there were some reduction of cell volume, cell vacuolization, chromatin condensation and increased number of apoptotic cells visible by light and fluorescence microscopy. Agarose gel electrophoresis revealed that cells treated with piplartine exhibited DNA fragmentation. In addition, growth inhibition of PC-3 cells was associated with G2/M arrest and sub-G1 accumulation. Higher concentrations (24-30 microM) of piplartine modulated apoptosis-related protein expression by down-regulating cdc-2 expression and up-regulating PARP/procaspase-3 cleavage. Also, PC-3 cells treated with piplartine demonstrated caspase-3 activation, as observed with an in vitro caspase-3 colorimetric assay kit. Taken together, these results demonstrated that high concentrations of piplartine exhibited anti-proliferative and anti-cancer effects on PC-3 cells and that caspase-3-mediated PARP cleavage and cell cycle arrest at G2/M phase are involved in the underlying cellular mechanism of the apoptosis process.     

Selenium effects on prostate cell growth.

Epidemiological and clinical data suggest that selenium may prevent prostate cancer, but the biological effects of selenium on normal or malignant prostate cells are not well known. We evaluated the effects of sodium selenite (Na2SeO3) or l-selenomethionine (SeMet) on monolayer and anchorage-independent growth in a series of normal primary prostate cultures (epithelial, stromal, and smooth muscle) and prostate cancer cell lines (LNCaP, PC-3, and DU145). We observed differential, dose-dependent growth inhibition and apoptosis within prostate cancer cells (compared with normal prostate cells) treated with 1-500 microM of Na2SeO3 or SeMet. Na2SeO3 more potently inhibited growth at any given concentration. The androgen-responsive LNCaP cells were the most sensitive to selenium growth suppression (IC50s at 72 h for Na2SeO3 and SeMet were 0.2 and 1.0 microM, respectively). Growth of the primary prostate cells virtually was not suppressed (IC50s at 72 h for Na2SeO3 and SeMet were 22-38 and >500 microM, respectively). We also observed that DNA condensation and DNA fragmentation (terminal deoxynucleotidyltransferase dUTP nick end labeling/fluorescence-activated cell sorting) were elevated in selenium-treated cells and that activated caspase-3 colocalized with terminal deoxynucleotidyltransferase dUTP nick end labeling-stained cells by immunofluorescence. Higher basal poly(ADP-ribose) polymerase (PARP) expression levels and PARP cleavage (a substrate for caspase-3) were observed during apoptosis in tumor cells, compared with normal cells. Selective tumor cell death was associated with an increase in sub-G0-G1 cells after propidium iodide staining and fluorescence-activated cell sorting analysis. SeMet caused an increase in arrest in the G2-M phase of the cell cycle selectively in cancer cells. Inhibition of cancer cell growth by SeMet was associated with phosphorylation of P-Tyr15-p34/cdc2, which caused growth arrest in the G2-M phase. Anchorage-independent growth of prostate cancer cells in soft agar was sensitive to selenium. Our results suggest that Na2SeO3 is the more potent inducer of apoptosis in normal and cancer prostate cells. Our SeMet results involving PARP and G2-M cell-cycle arrest (cited above) indicate that SeMet selectively induces apoptosis in cancer but not primary cells of the human prostate. Our overall findings are relevant to the molecular mechanisms of selenium actions on prostate carcinogenesis and help demonstrate the selective, dose-dependent effects of selenium (especially SeMet) on prostate cancer cell death and growth inhibition.     

Overcoming the radioresistance of prostate cancer cells with a novel Bcl-2 inhibitor

Bcl-2 overexpression is an important mechanism underlying the aggressive behavior of prostate cancer cells and their resistance to radio- or chemotherapy. HA14-1, a recently discovered organic Bcl-2 inhibitor, potently induces apoptosis in various human cancer cells. Sequential exposure of radioresistant LNCaP (wild-type (wt) p53), LNCaP/Bcl-2 (wt p53) and PC3 (mutant p53) prostate cancer cells to a minimally cytotoxic concentration of 10 microM HA14-1 for 1 h followed by 1-6 Gy gamma radiation, resulted in a highly synergistic (combination index <1.0) induction of cell death as determined by an apoptosis assay at 72 h, and a clonogenicity assay at 12 days, after the initial treatment. The reverse treatment sequence did not cause a synergistic induction of cell death. When compared to individual treatments, cell death induced by the combined treatment was associated with dramatically increased reactive oxygen species (ROS) generation, c-Jun N-terminal kinase (JNK) activation, Bcl-2 phosphorylation, cytochrome c release, caspase-3 activation and DNA fragmentation. Exposure to either 200 microg/ml of the antioxidant alpha-tocopherol or 10 microM JNK inhibitor SP600125 before the combined treatment resulted in decreased activation of JNK and caspase-3 as well as decreased DNA fragmentation. However, treatment with the pancaspase inhibitor carbobenzoxyl-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone before the combined treatment inhibited apoptosis without affecting JNK activation, and this inhibitory effect was enhanced in the presence of alpha-tocopherol or SP600125. Taken together, our results indicate that HA14-1 potently sensitizes radioresistant LNCaP and PC3 cells to gamma radiation, regardless of the status of p53. ROS and JNK are important early signals that trigger both caspase-dependent and -independent cell death pathways and contribute to the apoptotic synergy induced by the combined treatments.     

A PARP-1/JNK1 cascade participates in the synergistic apoptotic effect of TNFalpha and all-trans retinoic acid in APL cells

When administrated by isolated limb perfusion, tumor necrosis factor alpha (TNFalpha) is an efficient antitumor agent that improves drug penetration and destroys angiogenic vessels. Moreover, the pronounced potentiation of TNFalpha-induced apoptosis by NF-kappaB inhibitors suggest that these compounds could enhance TNFalpha antitumor efficacy through direct induction of tumor cell apoptosis. Therefore, attempts at amplifying signaling pathways that mediate TNFalpha antitumor effects could help to design combination therapies improving its efficiency. We report that nanomolar concentrations of all-trans retinoic acid (ATRA) amplify TNFalpha-induced apoptosis in APL cells expressing a specific repressor of NF-kappaB activation. This effect is abolished by the pan-caspase inhibitor, Z-VAD-fmk and by caspase-8 and -9 inhibitors. Cell death is accompanied by a drop of mitochondrial potential and by poly (ADP-ribose) polymerase (PARP) activation. Using specific PARP-1 inhibitors and siRNAs, we show that PARP-1 is essential for the synergistic apoptotic effect and c-Jun N-terminal kinase 1 (JNK1) activation triggered by the ATRA/TNFalpha combination. JNK1 siRNAs reduce ATRA/TNFalpha-induced apoptosis, mitochondrial release of cytochrome c and caspase-9 activation. Altogether, these results identify a novel mechanism of PARP-1-induced apoptosis, in which JNK1 provides a link between PARP-1 activation and mitochondrial pathway of caspase-9 activation. This study also suggests that inclusion of nanomolar doses of ATRA could be clinically beneficial in amplifying TNFalpha-induced antitumor signals.     

Potentiation of temozolomide and topotecan growth inhibition and cytotoxicity by novel poly(adenosine diphosphoribose) polymerase inhibitors in a panel of human tumor cell lines.

Potent poly(ADP-ribose) polymerase (PARP) inhibitors have been developed that potentiate the cytotoxicity of ionizing radiation and anticancer drugs. The biological effects of two novel PARP inhibitors, NU1025 (8-hydroxy-2-methylquinazolin-4-[3H]one, Ki = 48 nM) and NU1085 [2-(4-hydroxyphenyl)benzamidazole-4-carboxamide, Ki = 6 nM], in combination with temozolomide (TM) or topotecan (TP) have been studied in 12 human tumor cell lines (lung, colon, ovary, and breast cancer). Cells were treated with increasing concentrations of TM or TP +/- NU1025 (50, 200 microM) or NU1085 (10 microM) for 72 h. The potentiation of growth inhibition by NU1025 and NU1085 varied between the cell lines from 1.5- to 4-fold for TM and 1- to 5-fold for TP and was unaffected by p53 status. Clonogenic assays undertaken in two of the cell lines confirmed that the potentiation of growth inhibition reflected the potentiation of cytotoxicity. NU1025 (50 microM) was about as effective as 10 microM NU1085 at potentiating growth inhibition and cytotoxicity, consistent with the relative potencies of the two molecules as PARP inhibitors. Potentiation of cytotoxicity was obtained at concentrations of NU1025 and NU1085 that were not toxic per se; however, NU1085 alone was 3-fold more cytotoxic (LC50 values ranged from 83 to 94 microM) than NU1025 alone (LC50 > 900 microM). These data demonstrate that PARP inhibitors are effective resistance-modifying agents in human tumor cell lines and have provided a comprehensive assessment protocol for the selection of optimum combinations of anticancer drugs, PARP inhibitors, and cell lines for in vivo studies.     

Sequence dependent exposure of mammary carcinoma cells to Taxotere and the MEK1/2 inhibitor U0126 causes enhanced cell killing in vitro

Taxol (paclitaxel) and Taxotere (docetaxel) are considered as two of the most important anti-cancer chemotherapy drugs. The cytotoxic action of these drugs has been linked to their ability to inhibit microtubule depolymerization, causing growth arrest and subsequent cell death. Studies by a number of laboratories have also linked suppression of mitogen activated protein kinase (MAPK) signaling to enhanced Taxol toxicity. The present study examined the interactions of the semi-synthetic taxane Taxotere with MEK1/2 inhibitors in epithelial tumor cells. Concurrent treatment of MDA-MB-231 mammary and DU145 prostate carcinoma cells with Taxotere and MEK1/2 inhibitor resulted in protection from the anti-proliferative effects of Taxotere in MTT assays. In contrast, in MCF-7 mammary cells, concurrent Taxotere and MEK1/2 inhibitor treatment weakly enhanced the anti-proliferative effects of the taxane. Sequential treatment of MDA-MB-231 and MCF-7 cells with Taxotere followed by MEK1/2 inhibitor also enhanced the anti-proliferative effects of the taxane in MTT assays. However, no enhancement was observed in DU145 or PC-3 cells. Colony formation assays, including isobologram analyses, provided a more definitive demonstration that MCF-7 and MDA-MB-231 cells were sensitized to the toxic effects of Taxotere by U0126. Similar data were observed using Laulimalide, which binds to tubulin at a different site to Taxotere. The enhancement in Taxotere anti-proliferative effects by U0126 correlated with increased cell killing, 48-72h after treatment of cells that was blocked by inhibition of caspase 9, but not caspase 8, function. This observation was associated with prolonged suppression of ERK1/2 and AKT activity, without alteration in either p38 or JNK1/2 activity. Collectively these findings demonstrate that sequential administration of Taxotere followed by MEK1/2 inhibition can lead to increased cell death and loss of reproductive capacity in some, but not all, human tumor cells.     

A Novel All-trans Retinoid Acid Derivative Induces Apoptosis in MDA-MB-231 Breast Cancer Cells

Aims: To explore the effect and probable mechanism of a synthetic retinoid 4-amino-2-tri-fluoromethylphenylester (ATPR) on apoptosis of MDA-MB-231 breast cancer cells. Materials and Methods: MTT assayswere performed to measure the proliferation of MDA-MB-231 cells treated with different concentrations of alltransretinoic acid (ATRA) and ATPR. Morphologic changes were observed by microscopy. The apoptosis ratesand cell cycling of MDA-MB-231 cells treated with ATRA or ATPR were assessed using flow cytometry analysis.Expression of retinoic acid receptor and phosphorylation of ERK, JNK, p38 proteins were detected by Westernblotting. Results: Treatment of the cells with the addition of 15 μmol/L ATPR for 48 h clearly demonstratedreduced cell numbers and deformed cells, whereas no changes in the number and morphology were observedafter treatment with ATRA. The apoptosis rate was 33.2% after breast cancer MDA-MB-231 cells were treatedby ATPR (15 μmol/L) whereas ATRA (15 μmol/L) had no apoptotic effect. ATPR inhibited the phosphorylationof ERK, JNK, and p38 while ATRA had no significant effect. ATPR inhibited the expression of BiP and increasedthe expression of Chop at the protein level compared with control groups, ATRA and ATPR both decreasedthe protein expression of RXR α, ATPR reduced the protein expression of RARβ and RXRβ while ATRA didnot decrease RARβ or RXRβ. Conclusions: ATPR could induce apoptosis of breast cancer MDA-MB-231 cells,possible mechanisms being binding to RARβ/RXRβ heterodimers, then activation of ER stress involving theMAPK pathway.     

Effect of triptolide on focal adhesion kinase and survival in MCF-7 breast cancer cells

Triptolide, a diterpene from Tripterygium wilfordii, has been shown to have potent anticancer activity, exerting its effects through multiple molecular targets and signaling pathways. Yet, its effect on focal adhesion kinase (FAK), a non-receptor tyrosine kinase overexpressed in breast cancer that regulates cellular adhesion and survival, has not been reported. The current study is the first to report on the effect of triptolide on FAK expression, cell adhesion and survival using MCF-7 breast cancer cells. Triptolide significantly reduced MCF-7 anchorage-independent growth in a concentration-dependent manner. Cell rounding and detachment from culture plates were observed as early as 8 h, with significant cell detachment observed after 24 h of triptolide treatment. The adhesion potential of triptolide-treated MCF-7 cells to Matrigel was also compromised. Triptolide induced concentration- and time-dependent cleavage of FAK and PARP, which was dependent on caspase activation. The pan-caspase inhibitor, zVAD-fmk, was the only inhibitor that could significantly reduce FAK and PARP cleavage and cell detachment. However, the presence of zVAD-fmk failed to significantly reverse triptolide-induced cell death. Finally, triptolide-induced FAK cleavage was specific to MCF-7 cells, as no cleaved FAK was observed in MDA-MB-231 cells. In conclusion, our data present the first evidence of triptolide-mediated induction of FAK cleavage that correlates with cell detachment and loss of adhesion potential to the extracellular matrix.     

Modulation of radiation response by histone deacetylase inhibition

PURPOSE: Histone deacetylase (HDAC) inhibitors, which modulate chromatin structure and gene expression, represent a class of anticancer agents that hold particular potential as radiation sensitizers. In this study, we examine the capacity of the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) to modulate radiation response in human tumor cell lines and explore potential mechanisms underlying these interactions. METHODS AND MATERIALS: Cell proliferation: Exponentially growing tumor cells were incubated in medium containing 0-10 microM of SAHA for 72 h. Cells were fixed/stained with crystal violet to estimate cell viability. Apoptosis: Caspase activity was analyzed by fluorescence spectroscopy using a fluorescein labeled pan-caspase inhibitor. Cells were harvested after 48 h of exposure to SAHA (1.0 microM), radiation (6 Gy), or the combination. Whole cell lysates were evaluated for poly(ADP-ribose) polymerase (PARP) cleavage by western blot analysis. Radiation survival: Cells were exposed to varying doses of radiation +/- 3 days pretreatment with SAHA (0.75-1.0 microM). After incubation intervals of 14-21 days, colonies were stained with crystal violet and manually counted. Immunocytochemistry: Cells were grown and treated in chamber slides. At specified times after treatment with SAHA, cells were fixed in paraformaldehyde, permeabilized in methanol, and probed with primary and secondary antibody solutions. Slides were analyzed using an epifluorescent microscope. RESULTS: SAHA induced a dose-dependent inhibition of proliferation in human prostate (DU145) and glioma (U373vIII) cancer cell lines. Exposure to SAHA enhanced radiation-induced apoptosis as measured by caspase activity (p < 0.05) and PARP cleavage. The impact of SAHA on radiation response was further characterized using clonogenic survival analysis, which demonstrated that treatment with SAHA reduced tumor survival after radiation exposure. We identified several oncoproteins and DNA damage repair proteins (epidermal growth factor receptor, AKT, DNA-PK, and Rad51) that show differential expression after exposure to SAHA. These proteins may contribute to mechanistic synergy between HDAC inhibition and radiation response. CONCLUSION: These preclinical results suggest that treatment with the HDAC inhibitor SAHA can enhance radiation-induced cytotoxicity in human prostate and glioma cells. We are examining the capacity of HDAC inhibitors to modulate radiation response and tumor control in animal xenograft model systems to strengthen the rationale for future clinical trial exploration.     

川楝素对乳腺癌细胞的生长抑制作用

[目的]探讨川楝素对人乳腺癌MDA—MB-453细胞作用及其机制。[方法]取对数生长期的MDA—MB-453细胞,0、6．25、12．50、25．00、50．00、100．00nmol／L川楝素处理,绘制生长曲线。川楝素0、12．5、50nmol／L处理72h后,MTS法检测川楝素对乳腺癌细胞增殖的影响,流式细胞仪检测川楝素对乳腺癌细胞凋亡和细胞周期的影响。[结果]川楝素对乳腺癌细胞有增殖抑制作用．并呈时间剂量依赖性（P〈0．01）。MDA—MB453细胞48h、72h、96h的IC50分别为17．25、22．20和135．69nmol／L。流式细胞分析表明,川楝素诱导乳腺癌细胞的凋亡呈浓度依赖性（P〈0．01）,且阻滞细胞在S期（P〈0．01）,以0、12．50、50．00nmol／L川楝素处理乳腺癌细胞72h后,MDA—MB-453细胞早期凋亡率分别为3．21％、9．64％和20．19％,MDA—MB-453细胞处于细胞周期S期细胞占20．98％、35．92％和45．02％。[结论]川楝素对乳腺癌MDA—MB-453细胞增殖具有抑制作用,其作用机制可能与诱导细胞凋亡和引起S期阻滞有关。     

Gene expression profiling revealed novel mechanism of action of Taxotere and Furtulon in prostate cancer cells

Background  

Both Taxotere and Capecitabine have shown anti-cancer activity against various cancers including prostate cancer. In combination, Taxotere plus Capecitabine has demonstrated higher anti-cancer activity in advanced breast cancers. However, the molecular mechanisms of action of Taxotere and Capecitabine have not been fully elucidated in prostate cancer.     

Guggulsterone-induced apoptosis in human prostate cancer cells is caused by reactive oxygen intermediate dependent activation of c-Jun NH2-terminal kinase

Guggulsterone, a constituent of Indian Ayurvedic medicinal plant Commiphora mukul, causes apoptosis in cancer cells but the sequence of events leading to cell death is poorly understood. We now show that guggulsterone-induced cell death in human prostate cancer cells is caused by reactive oxygen intermediate (ROI)-dependent activation of c-Jun NH(2)-terminal kinase (JNK). Exposure of PC-3 and LNCaP cells to apoptosis inducing concentrations of guggulsterone resulted in activation of JNK and p38 mitogen-activated protein kinase (p38 MAPK) in both cell lines and activation of extracellular signal-regulated kinase 1/2 (ERK1/2) in LNCaP cells. The guggulsterone-induced apoptosis in PC-3/LNCaP cells was partially but statistically significantly attenuated by pharmacologic inhibition (SP600125) as well as genetic suppression of JNK activation. On the other hand, pharmacologic inhibition of p38 MAPK activation in PC-3 or LNCaP cells (SB202190) and ERK1/2 activation in LNCaP cells (PD98059) did not protect against guggulsterone-induced cell death. The guggulsterone treatment caused generation of ROI in prostate cancer cells but not in a normal prostate epithelial cell line (PrEC), which was also resistant to guggulsterone-mediated JNK activation. The guggulsterone-induced JNK activation as well as cell death in prostate cancer cells was significantly attenuated by overexpression of catalase and superoxide dismutase. In addition, guggulsterone treatment resulted in a decrease in protein level and promoter activity of androgen receptor in LNCaP cells. In conclusion, the present study reveals that the guggulsterone-induced cell death in human prostate cancer cells is regulated by ROI-dependent activation of JNK and guggulsterone inhibits promoter activity of androgen receptor.     

Cyclooxygenase (COX) inhibitors induce apoptosis in non-small cell lung cancer through cyclooxygenase independent pathways

Cyclooxygenase (COX) inhibitors are chemopreventive in many tumours but the role of COX inhibition in their effects is contentious. Here we determined if COX inhibitors influenced apoptosis in two non-small cell lung cancer cells one which over expresses COX-2 (MOR-P) and one which expresses neither isoform (H-460). NS398, a selective COX inhibitor, and indomethacin, a non-selective COX inhibitor, were cytotoxic in both cell lines, independently of their COX-2 expression. Furthermore, the cytotoxic concentrations were far greater than the concentrations required to inhibit COX. As indomethacin was more effective we used it in mechanistic studies. Indomethacin induced apoptotic cell death assessed as cytochrome c and apoptotic inducing factor (AIF) release, caspase activation, PARP, lamin B and gelsolin cleavage, chromatin condensation and nuclear fragmentation. The pan-caspase inhibitor, z-VAD, attenuated cell death, and blocked caspase activation, PARP cleavage and nuclear fragmentation without preventing cytochrome c release, suggesting that cytochrome c release is upstream of caspase activation. These observations suggest that COX inhibitors induce apoptosis in non-small lung cancer cells through cytochrome c and AIF release, and subsequent caspase activation, independently of COX-2 expression and prostaglandin production.     

JNK信号通路介导ghrelin对乳腺癌MDA-MB-231细胞耐药蛋白表达的影响

目的探讨ghrelin调控c-Jun氨基末端激酶(c-Jun N-terminal kinase,JNK)信号转导通路对乳腺癌细胞P-糖蛋白表达的影响。方法培养人乳腺癌MDA-MB-231细胞,分别加入生长激素释放肽(ghrelin,100 nmol/L,干预72小时)、多柔比星(0.8 mg/L,干预72小时)、ghrelin联合多柔比星(ghrelin 100 nmol/L,多柔比星0.8 mg/L,干预72小时)。采用MTT方法检测细胞增殖,Western blot法检测细胞JNK、P-糖蛋白(P-glycoprotein,P-gp)的表达及p-JNK水平。结果 MTT检测显示,人乳腺癌MDA-MB-231细胞在ghrelin的干预下增殖(P<0.01),存活率在多柔比星的干预下降低(P<0.01),ghrelin联合多柔比星能够抑制多柔比星对MDA-MB-231细胞的杀伤作用(P<0.01)。ghrelin组JNK表达及p-JNK水平上升(均P<0.01),且P-gp蛋白表达上升(P<0.05);多柔比星组JNK表达及p-JNK水平下降(均P<0.01);ghrelin联合多柔比星较多柔比星组JNK表达及p-JNK水平增加,且P-gp表达明显上升(均P<0.05)。结论 ghrelin激活JNK信号通路干预乳腺癌细胞P-gp表达增加从而抑制多柔比星诱导乳腺癌细胞凋亡。     

Acetyl-keto-beta-boswellic acid induces apoptosis through a death receptor 5-mediated pathway in prostate cancer cells

Acetyl-keto-beta-boswellic acid (AKBA), a triterpenoid isolated from Boswellia carterri Birdw and Boswellia serrata, has been found to inhibit tumor cell growth and to induce apoptosis. The apoptotic effects and the mechanisms of action of AKBA were studied in LNCaP and PC-3 human prostate cancer cells. AKBA induced apoptosis in both cell lines at concentrations above 10 microg/mL. AKBA-induced apoptosis was correlated with the activation of caspase-3 and caspase-8 as well as with poly(ADP)ribose polymerase (PARP) cleavage. The activation of caspase-8 was correlated with increased levels of death receptor (DR) 5 but not of Fas or DR4. AKBA-induced apoptosis, caspase-8 activation, and PARP cleavage were inhibited by knocking down DR5 using a small hairpin RNA. AKBA treatment increased the levels of CAAT/enhancer binding protein homologous protein (CHOP) and activated a DR5 promoter reporter but did not activate a DR5 promoter reporter with the mutant CHOP binding site. These results suggest that AKBA induces apoptosis in prostate cancer cells through a DR5-mediated pathway, which probably involves the induced expression of CHOP.