Didox (a novel ribonucleotide reductase inhibitor) overcomes Bcl-2 mediated radiation resistance in prostate cancer cell line PC-3

In this study, we investigated the influence of Bcl-2 overexpression on the radiosensitizing potential of Didox (DX; 3,4-Dihydroxybenzohydroxamic acid), a novel ribonucleotide reductase inhibitor, in p53-null prostate cancer cell line PC-3. The PC-3 cells were transfected with vector alone or ectopically overexpressed with CMV-Bcl-2 construct. The effect of radiation (IR) or DX alone and in combination (pre and post IR exposure of DX) on cell survival was determined by colony-forming assay. The impact of these two treatments on the cell cycle was determined by flow cytometry. To further understand the molecular mechanism of DX-mediated radiosensitization, induction of pro-survival and pro-apoptotic factors were determined by Western blot and gel-shift assays respectively. When compared to PC-3/Bcl-2 cells (SF(2)=0.84; D(0)=437cGy), the PC-3/vector cells (SF(2)=0.4; D(0)=235cGy) were significantly sensitive to ionizing radiation (p<0.001). Exposure of DX at 5 microM concentration prior or post to radiation in both PC-3/vector and PC-3/Bcl-2 transfectants caused an increase in radiation enhancement ratios. A significant reduction in G(2)M phase was observed in cells exposed to DX post IR when compared to cells exposed to IR alone. Exposure to DX after radiation in PC-3/vector significantly abrogated radiation-induced Bcl-2 upregulation, with a concomitant induction of bax protein. In PC-3/Bcl-2 transfectants, DX exposure after IR caused an induction of bax protein. Gel shift assays indicated that in PC-3/vector cells when exposed to IR caused an induction of NFkappa-B activity however, DX down regulated the NFkappa-B activity. Radiation-induced NFkappa-B activity was abrogated in pre and post DX exposure in combination with IR. These findings indicate that DX mediates a potent radiosensitizing effect in p53 null prostate cancer cells by overcoming radiation induced NFkappa-B activity and Bcl-2 expression.     

Curcumin confers radiosensitizing effect in prostate cancer cell line PC-3

Curcumin (Diferuloylmethane) is a major chemical component of turmeric (curcuma longa) and is used as a spice to give a specific flavor and yellow color in Asian food. Curcumin exhibits growth inhibitory effects in a broad range of tumors as well as in TPA-induced skin tumors in mice. This study was undertaken to investigate the radiosensitizing effects of curcumin in p53 mutant prostate cancer cell line PC-3. Compared to cells that were irradiated alone (SF(2)=0.635; D(0)=231 cGy), curcumin at 2 and 4 microM concentrations in combination with radiation showed significant enhancement to radiation-induced clonogenic inhibition (SF(2)=0.224: D(0)=97 cGy and SF(2)=0.080: D(0)=38 cGy) and apoptosis. It has been reported that curcumin inhibits TNF-alpha-induced NFkappaB activity that is essential for Bcl-2 protein induction. In PC-3 cells, radiation upregulated TNF-alpha protein leading to an increase in NFkappaB activity resulting in the induction of Bcl-2 protein. However, curcumin in combination with radiation treated showed inhibition of TNF-alpha-mediated NFkappaB activity resulting in bcl-2 protein downregulation. Bax protein levels remained constant in these cells after radiation or curcumin plus radiation treatments. However, the downregulation of Bcl-2 and no changes in Bax protein levels in curcumin plus radiation-treated PC-3 cells, together, altered the Bcl2 : Bax ratio and this caused the enhanced radiosensitization effect. In addition, significant activation of cytochrome c and caspase-9 and -3 were observed in curcumin plus radiation treatments. Together, these mechanisms strongly suggest that the natural compound curcumin is a potent radiosesitizer, and it acts by overcoming the effects of radiation-induced prosurvival gene expression in prostate cancer.     

Expression of the human Bcl-2 increases resistance of Ewing's sarcoma cells to apoptosis and inhibits poly(ADP-ribose) polymerase cleavage induced by radiation

We reported previously that Ewing's sarcoma (ES) cells respond to ionizing radiation exposure by arrest in G(2)/M phase and induction of apoptosis which occurs in conjunction with poly(ADP-ribose) polymerase (PARP) proteolytic cleavage. ES cells (A4573 cell line) do not express immunodetectable levels of Bcl-2. To determine if expression of Bcl-2 could modulate radiation-induced ES cell death, we have stably transfected A4573 cells with a full-length human bcl-2 cDNA. Expression of Bcl-2 protein rendered ES cells relatively resistant to radiation-induced apoptosis. Moreover, the anti-apoptotic activity of Bcl-2 was directly related to levels of its expression in different ES clones. Cell cycle characteristics were similar for both parental and Bcl-2 expressing ES cells following radiation treatment, although bcl-2 transfectants exhibited a more protracted G(2)/M phase arrest and lower rate of apoptosis after release from the block. Constitutive expression of Bcl-2 resulted in about two-fold inhibition of PARR cleavage in ES cells dying after ionizing radiation exposure. These data support a role for Bcl-2 protein as a negative regulatory element of PARP proteolysis at the early stages of radiation-induced apoptosis in ES cells.     

Sensitization to radiation-induced DNA damage accelerates loss of bcl-2 and increases apoptosis and autophagy

Since it is important to lower the death threshold in tumor cells and to enhance response to genotoxic damage, the mechanisms of bromodeoxyuridine (BrdU)-mediated radiosensitization were now examined in human C8161 melanoma. This revealed that anti-apoptotic Bcl-2, and cell cycle controlling hyperphosphorylated Rb and cyclin A were downregulated by BrdU, even without irradiation. BrdU pretreatment and subsequent UV irradiation (10 J/m(2)) accelerated an early increase in the ratio of pro-apoptotic Bax to that of Bcl-2, increased apoptosis-associated PARP cleavage and potentiated DNA damage compared to irradiated unsensitized cells. BrdU also synergized with radiation to increase autophagic features, such as perinuclear vacuole formation. More specifically, conversion of LC3B-I into LC3B-II by immune blotting and an increased pattern of cytoplasmic and nuclear LC3B by fluorescent immunostaining, supported induction of autophagy in BrdU-pretreated cells irradiated with 25 J/m(2). This report shows for the first time that radiation sensitizers like BrdU enhance and modify radiation-induced cell death by accelerating an increased bax/bcl-2 ratio in unirradiated cells, and subsequently increasing radiation-induced apoptosis and/or autophagy depending on radiation dosage.     

Bombesin stimulates nuclear factor kappa B activation and expression of proangiogenic factors in prostate cancer cells

The majority of deaths from prostate cancer occur in patients with androgen-insensitive metastatic disease. An important early event in the development of the metastatic phenotype is the induction of genes that promote angiogenesis, such as vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8), which are released from tumor cells into their microenvironment. Coincident with progression from prostatic carcinoma in situ to metastatic disease is an increase in the number of tumor cells exhibiting neuroendocrine (NE) differentiation. NE cells express a variety of peptide hormones, including the bombesin (BBS)-like peptide, gastrin-releasing peptide (GRP), and its cognate receptor, GRP-R. Although there is a strong positive correlation between the degree of NE differentiation and the metastatic potential of prostate cancers, a mechanistic link between increased expression of peptide hormone receptors, such as GRP-R, and proangiogenic gene expression has not been established. Here we report that BBS stimulates nuclear factor kappa B (NF kappa B) activation and proangiogenic gene expression in the androgen-insensitive prostate cancer cells lines, PC-3 and DU-145. In PC-3 cells, BBS stimulation of GRP-R resulted in the up-regulation of IL-8 and VEGF expression through a NF kappa B-dependent pathway. We show that BBS treatment induced inhibitor of NF kappa B degradation, NF kappa B translocation to the cell nucleus, increased NF kappa B binding to its DNA consensus sequence, and increased IL-8 and VEGF mRNA expression and protein secretion. Treatment with the proteasome inhibitor, MG-132, blocked BBS-stimulated NF kappa B DNA binding, and IL-8 and VEGF expression and secretion. Finally, media collected from PC-3 cell cultures, after BBS treatment, stimulated an NF kappa B-dependent migration of human umbilical vascular endothelial cells in vitro. Together, our data demonstrate a role for BBS and GRP-R in the NF kappa B-dependent up-regulation of proangiogenic gene expression, and suggest a possible molecular mechanism linking NE differentiation and the increased metastatic potential of androgen-insensitive prostate cancers.     

bcl-2基因反义寡核苷酸增强放射线诱导Raji细胞凋亡的研究

目的研究bcl-2基因反义寡核苷酸作用淋巴瘤细胞株Raji后,放射线对细胞凋亡的影响.方法bcl-2基因反义寡核苷酸作用Raji细胞后,台盼蓝拒染法计数活细胞;免疫荧光标记观测细胞Bcl-2蛋白水平;用姬姆萨染色和碘化丙啶染色法、流式细胞仪检测细胞凋亡.结果bcl-2基因反义寡核苷酸与放射线联合作用Raji细胞,显著抑制细胞的生长,并呈时间依赖性,活细胞数分别与单用放射线组及无义寡核苷酸联合放射线组相比,统计学上有显著性差异(P＜0.05).bcl-2基因反义寡核苷酸与放射线联合作用于Raji细胞后显著抑制bcl-2蛋白表达,蛋白水平分别与单用放射线组或无义寡核苷酸联用放射线组比较,差异有显著性(P＜0.05).bcl-2基因反义寡核苷酸与放射线同时作用于Raji细胞后,姬姆萨染色可见凋亡细胞,通过流式细胞仪检测的细胞凋亡率显著增加,分别与单用放射线组或无义寡核苷酸联用放射线组相比,具有显著性差异,P＜0.05.结论bcl-2反义寡核苷酸能增强放射线诱导Raji细胞凋亡.     

Inhibition of expression of anti-apoptotic protein Bcl-2 and induction of cell death in radioresistant human prostate adenocarcinoma cell line (PC-3) by methyl jasmonate

Hormone refractory human prostate cancer cell lines are known to be radioresistant, a feature attributed to their ability to induce anti-apoptotic proteins of the Bcl-2 family when exposed to radiation. We investigated whether pro-apoptotic compounds such as methyl jasmonate, a plant stress hormone, can counteract the radiation-induced anti-apoptotic mechanism in a human prostate cancer cell line PC-3. Significant (p < 0.05) increase in cytotoxicity was observed in the combined treatment groups compared to single treatments with methyl jasmonate or γ-radiation. Treatment of irradiated PC-3 cells with methyl jasmonate resulted in suppression of anti-apoptotic Bcl-2 protein and elevation of caspase-3 activity. Our results showed increased apoptosis in the combined treatment group as compared to the irradiated group or the untreated control. In summary, methyl jasmonate suppressed the radiation-induced Bcl-2 expression and enhanced the radiation sensitivity of human prostate cancer cells.     

DAPK诱导PGCl3细胞凋亡时Bcl-2磷酸化的研究

目的:探讨DAPK诱导PGCl3细胞凋亡的可能机制。方法:真核表达载体pcDNA3.1-DAPK导入PGCl3细胞中。RT-PCR检测bcl-2和baxm-RNA丰度变化,Bcl-2含量变化和Bcl-2磷酸化水平变化。结果:DAPK诱导PGCl3细胞凋亡时,bcl-2表达是下调的,bax基因表达量无明显变化,pcDNA3.1-DAPK转染组的Bcl-2磷酸化水平相对pcDNA3.1组要高,同时Bcl-2蛋白含量是减少的。结论:过表达的DAPK诱导PGCl3细胞凋亡与bcl-2转录下调和Bcl-2磷酸化有关     

Ad-ING4对人前列腺癌细胞PC-3体内外抑癌效应的研究

背景与目的：腺病毒作为载体已被广泛用于肿瘤的基因治疗。ING4是生长抑制因子家族中的一个成员,是一种潜在的抑癌基因。本研究旨在探讨腺病毒介导的人ING4基因（Ad-ING4）对人前列腺癌细胞PC-3的体内外抑癌效应及其分子机制。方法：将扩增的Ad-ING4重组腺病毒感染PC-3细胞,用RT-PCR法检测ING4在PC-3细胞中的转录;MTT法检测ING4基因对PC-3细胞增殖的影响：流式细胞术和Hoechst33258染色法检测细胞凋亡的变化;半定量RT-PCR法检测ING4基因的表达对PC．3细胞中的bcl-2、bax、p53和caspase-3凋亡相关基因表达的影响。用Ad-ING4重组腺病毒在裸鼠PC-3移植瘤的瘤体内注射治疗,观察肿瘤生长变化,15d后处死裸鼠,摘除瘤体,称瘤重;用免疫组化法检测瘤组织中Bcl-2、Bax、Caspase-3和CD34蛋白的表达。结果：腺病毒介导的人ING4基因在PC-3细胞中成功转录,明显抑制PC-3细胞增殖,上调p53、bax、caspase．3基因表达和下调bcI-2基因表达,并诱导细胞凋亡。Ad-ING4重组腺病毒能显著抑制裸鼠PC-3移植瘤的生长,瘤重的抑制率达37％,与空病毒载体Ad-GFP组和细胞对照PBS组比较差异有统计学意义（P〈0．05）;免疫组化结果显示Ad-ING4重组腺病毒能明显上调Bax和Caspase-3蛋白的表达水平,下调Bcl-2和CD34蛋白的表达水平。结论：腺病毒介导的ING4基因在体内外均可明显抑制人前列腺癌细胞PC-3的生长,诱导其凋亡,其机制可能是上调P53、Bax、Caspase-3蛋白和下调Bcl-2蛋白表达水平。     

p53基因诱导胱癌细胞HTB9凋亡及相关基因的表达

目的 研究野生型p53基因诱导膀胱癌细胞凋亡的作用,及其对凋亡相关基因bcl-2、bax和ICE表达的调控。方法 将野生型p53基因重组腺病毒载体转染人膀胱癌细胞HTB9,应用RT－PCR检测bax的mRNA表达水平,应用免疫组化法检测bcl-2、bax和ICE蛋白表达水平,以DNA琼脂糖凝胶电泳、脱氧核苷酸转移酶介导的dUTP切口末端标记技术（TUNEL）和流式细胞仪检测细胞凋亡。结果 野生型p53基因导入可诱导HTB9细胞凋亡,凋亡细胞百分率可达50．4％;bax mRNA和蛋白水平增高,ICE和Bcl-2蛋白水平分别增高和下降。结论 野生型p53基因很可能是通过调控凋亡相关基因ICE、Bax和Bcl-2的表达来诱导细胞凋亡。     

Alpha1-adrenoceptor antagonists radiosensitize prostate cancer cells via apoptosis induction

BACKGROUND: Androgen-independent prostate cancer cells can undergo apoptosis in response to non-androgen ablative means such as ionizing radiation. Recent evidence documented the ability of alpha-adrenoceptor antagonists, a widely used medical therapy for the treatment of benign prostatic hypertrophy (BPH), to induce apoptosis in benign and malignant prostate cells. In this study, we evaluated the potential additive/synergistic apoptotic effect of alpha1-adrenoceptor antagonists with ionizing radiation against human prostate cancer cells in vitro. MATERIALS AND METHODS: Androgen-independent human prostate cancer cells (PC-3) were treated with two alpha1-adrenoceptor antagonists, doxazosin and terazosin, for various periods of time prior to and after exposure to ionizing radiation. Apoptosis induction, cell viability and clonogenic assays were then performed to determine loss of clonogenic survival Hoechst staining was performed to detect the apoptotic morphology in prostate cancer cells and the temporal protein expression of the apoptosis regulators bax and caspase-3, was determined using Western blot analysis. RESULTS: No significant difference in cell death of PC-3 cells was detected when either doxazosin or terazosin was combined with ionizing radiation. Terazosin treatment however, 24 hours prior to, or 24 hours post-irradiation resulted in a significant enhancement of radiation-induced loss of clonogenic survival compared to radiation alone (p<0.05). Furthermore, there was a further significant increase in apoptosis induction when cells were pre-treated with terazosin (15%), compared to treatment with radiation alone (6%). Western blot analysis revealed a significant increase in bax protein expression (but not caspase-3) in response to radiation, with no additional effect with the combination treatment (terazosin and ionizing irradiation) compared to radiation alone. CONCLUSION: This is the first study to document the ability of alpha1-adrenoceptor antagonists to enhance the apoptotic effect of ionizing radiation against human prostate cancer cells. As this alpha1-adrenoceptor-mediated elevation of the apoptotic threshold involves neither bax deregulation nor caspase-3 activation, a differential mechanism might be underlying this radiosensitizing effect. The present findings may have important clinical relevance in identifying a more effective therapeutic approach for androgen-independent prostate cancer based on the combined apoptotic effects of quinazoline-based alpha1-adrenoceptor-antagonsists and radiotherapy.     

Molecular determinants of cell death induction following adenovirus-mediated gene transfer of wild-type p53 in prostate cancer cells

Adenoviral vectors expressing wild-type p53 (Ad-p53) induce apoptosis in different types of cancer cells. The therapeutic utility of Ad-p53 is now being evaluated in prostate-cancer patients. Bcl-2 is frequently expressed by prostate-cancer cells and has previously been shown to inhibit p53-mediated cell death following genotoxic stress. We studied the impact of bcl-2 on Ad-p53-induced cell death in human prostate-cancer cells. Human prostate-cancer cell lines LNCaP (p53 wt) and PC3 (p53 mut) were stably transfected with bcl-2. After p53 transduction, cell viability, apoptosis induction and modulation of specific apoptosis-regulatory proteins were assessed. LNCaP vector control and bcl-2-expressing cells underwent similar decreases in viability associated with apoptosis induction following Ad-p53 infection. Increased bcl-2 expression provided significant protection to PC3 cells transduced with Ad-p53. These findings are correlated with modulations in bax, bcl-2, bcl-x(L) and p21 protein levels. These data suggest that Ad-p53 may be useful in the treatment of some prostate cancers.     

Curcumin induces apoptosis involving bax/bcl-2 in human hepatoma SMMC-7721 cells

Curcumin is a major active component of Curcuma aromatica salisb, which has been shown to inhibit proliferation of a wide variety of tumor cells. In this study, the molecular mechanisms of curcumin inducing apoptosis in human hepatoma SMMC-7721 cells were examined. We find that curcumin inhibits the growth of SMMC-7721 cells significantly in a concentration-depenent manner, with typical apoptotic morphological changes of cellular nuclei. Annexin-V/PI double staining detected by flow cytometry and expression of the relative apoptotic proteins (Bax, Bcl-2 and caspase-3) revealed a strong apoptosis-inducing competent of curcumin in SMMC-7721 cells. Curcumin increased the expression of bax protein while decreasing that of bc1-2 protein significantly. The results suggest that curcumin induction of apoptosis involves modulation of bax/bcl-2 in SMMC-7721 cells and provide a molecular basis for the development of naturally compounds as novel anticancer agents for human hepatomas.     

Differential sensitivity of MCF-7 and LCC2 cells, to multiple growth inhibitory agents: possible relation to high bcl-2/bax ratio?

Comparison of LCC2, the E(2)-independent, tamoxifen-resistant subline of the MCF-7 human breast cancer cell line with its parent line, disclosed that it is more resistant to growth inhibition and apoptosis induction by a variety of agents acting by diverse mechanisms. Thus, LCC2 cells can serve as a useful in-vitro model for the study of the molecular mechanisms of this resistance. It was found that bcl-2 protein and mRNA were elevated and that bax protein and mRNA were reduced in LCC2 compared with MCF-7 cells. Incubation of both lines in the presence of bcl-2 antisense caused growth inhibition and reduced bcl-2 protein levels only in MCF-7 cells, suggesting the involvement of bcl-2 in the regulation of normal growth of breast cancer cells. Increased bcl-2 expression in breast cancer cells may correlate with their resistance to growth inhibitory agents. Bcl-2 is a useful target for enhancing the effects of growth inhibitory agents.     

Inhibition of cyclooxygenase-2 activity by celecoxib does not lead to radiosensitization of human prostate cancer cells in vitro.

PURPOSE: To evaluate the potential radiosensitizing effect of the specific COX-2 inhibitor celecoxib (Celebrex) on prostate carcinoma cells in vitro. MATERIALS AND METHODS: The influence of celecoxib (concentration range 5 to 75 microM) on radiation-induced cellular and clonogenic survival was investigated in prostate carcinoma cell lines PC-3, DU145, LNCaP and normal prostate epithelial cells (PrEC). Western blot analysis and ELISA were used to determine the impact of radiation alone or radiation combined with celecoxib treatment on COX-2 expression and prostaglandin E2 synthesis. To evaluate induction of celecoxib-induced apoptosis cell cycle analysis has been performed. RESULTS: Celecoxib (5, 10 and 25 microM) in combination with single-dose irradiation of 2 Gy induced a significant radiosensitization in normal prostate epithelial cells which could not be observed for any of the prostate carcinoma cell lines investigated. Increased COX-2 protein expression in PC-3 cells was obvious only after IR with 15 Gy, while PGE2 production was elevated following irradiation (2-15 Gy) in a dose-dependent manner. Treatment with celecoxib alone or in combination with IR led to a dose-dependent increase in COX-2 protein expression. Nevertheless pre-treatment with celecoxib caused a marked reduction of radiation-induced enzyme activity as tested at the level of PGE2 production, both in PC-3 and DU145 cells. Following fractionated irradiation with single doses of 2 Gy, elevated COX-2 protein expression as well as enhanced PGE2 production was observed already after the second fraction in PC-3 cells. Pre-treatment with celecoxib reduced the amount of PGE(2) significantly, but not of COX-2 protein. CONCLUSIONS: Our data obtained for the human prostate cancer cell lines do not indicate that a marked inhibition of prostaglandin E2 synthesis by celecoxib leads to enhanced radiosensitization. Thus, in terms of radiosensitization the analysed prostate cancer cells can be classified as non-responders to celecoxib treatment.     

术前单疗程化疗对非小细胞肺癌细胞凋亡的影响

目的探讨术前单疗程化疗对ⅢA期非小细胞肺癌细胞凋亡率、增殖指数及bcl-2、bax基因表达的影响。方法 2002年1月至2004年1月,对144例ⅢA期非小细胞肺癌进行随机对照试验,术前化疗组（试验组）和单纯手术组（对照组）各72例,前者于术前化疗1个疗程,化疗结束10-14 d后接受手术;对照组直接行手术治疗。手术切除的肺癌组织应用流氏细胞学方法测定细胞凋亡率、增殖指数及bcl-2、bax基因的表达。结果试验组和对照组细胞凋亡率、增殖指数及bcl-2、bax基因表达分别为（7.40±2.39%）、（4.93±2.13）%;（24.99±7.51）%、（31.72±7.43）%;4.70±1.16、6.51±1.09;5.57±0.96、4.65±0.91,两组比较均差异有显著性（P〈0.05）。结论术前单疗程化疗能提高ⅢA期NSCLC的肿瘤细胞凋亡率,降低肿瘤细胞增殖指数,并抑制bcl-2基因（抑制凋亡的基因）的表达,促进bax基因（促进凋亡的基因）的表达,并可能降低细胞生存能力,减少癌转移灶的发生。     

幽门螺杆菌感染性胃炎细胞凋亡与bcl-2/bax表达的意义

目的：探讨幽门螺杆菌ＨＰ引起胃粘膜上皮细胞凋亡和增殖发迹及ＨＰ致癌作用的可能机制。方法：采用免疫组织化学方法及脱氧核糖核酸末端转移酶介导的ｄＵＴＰ缺口末端标记（ＴＵＮＥＬ）技术,对ＨＰ阳性和ＨＰ阴性者胃粘膜上皮中增殖细胞,凋亡细胞进行原位观察和比较,同时检测ｂｃ１－２／ｂａｘ蛋白表达状态。结果：ＨＰ阳性者胃粘膜上皮细胞增殖指数和凋亡指数显著高于ＨＰ阴性者（Ｐ〈０．０１）。ｂａｘ蛋白表达阳性率在ＨＰ