三七总皂甙对多发性骨髓瘤细胞的增殖抑制作用及机制的研究

目的：观察三七总皂甙（PNS）对多发性骨髓瘤RPMI8226细胞增殖抑制的作用;并观察三七总皂甙与阿霉素（adriamycin,ADM）联合,是否具有协同效应,为三七总皂甙应用于多发性骨髓瘤临床治疗提供一定的实验依据。方法：MTT法检测三七总皂甙对RPMI8226细胞增殖的影响;运用金氏公式分析三七总皂甙与ADM联合的协同效应;RT-PCR法检测Bcl-2、Bax mRNA水平的变化。结果：三七总皂甙可抑制RPMI8226细胞的增殖,并呈剂量依赖性,24h IC50值为213.42±2.21μg/ml;三七总皂甙与ADM联合,表现出协同效应;三七总皂甙与ADM联合处理MM细胞24h后,Bcl-2 mRNA表达较单独应用三七总皂甙或ADM前明显下调,而Bax表达则明显上调。结论：三七总皂甙可以抑制多发性骨髓瘤细胞增殖,联合阿霉素,具有协同效应;其作用可能是通过下调Bcl-2,上调Bax在转录水平的表达而实现的。     

TRAIL is a potent inducer of apoptosis in myeloma cells derived from multiple myeloma patients and is not cytotoxic to hematopoietic stem cells.

TRAIL, the ligand for the newly discovered DR-4 and DR-5 receptor, is a member of the TNF family of death signal transduction proteins with a mechanism of cell death similar to that of Fas and Fas ligand (Fas-L) system. We provide first time evidence that TRAIL is a potent inducer of apoptosis in multiple myeloma (MM) cell lines. TRAIL effectively induced extensive apoptosis in 8226 and ARP-1 MM cells in a time- and dose-dependent manner. Apoptosis with TRAIL reached about 80% within 48 h of treatment with a dose of 160 ng/ml. Furthermore, we provide first time evidence that similar to Fas, TRAIL-induced apoptosis is not blocked by bcl-2 in MM cell lines. Most importantly, TRAIL induced substantial apoptosis in freshly isolated, flow-sorted myeloma cells obtained from different MM patients expressing variable levels of bcl-2. Finally, we demonstrate for the first time that TRAIL is not cytotoxic to purified CD34+/CD45dim hematopoietic stem cells and does not inhibit CFU-GM or BFU-E colony formation in methylcellulose.     

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。     

非甾体消炎药诱导胃癌细胞凋亡及其机制的研究

目的：明确非甾体消炎药(NSAIDs)能否诱导胃癌细胞凋亡；明确不同的p53基因表型对NSAIDs诱导的细胞凋亡是否有影响；明确NSAIDs对细胞凋亡相关基因Bcl-2及Bax表达的调控。方法：通过MTT比色法检测NSAIDs对细胞生长活力的影响；应用丫啶橙(AO)染色、Annexin-V／PI双染色、共聚焦显微镜、流式细胞术检测细胞凋亡；应用RT-PCR、Western-blot方法检测bcl-2、bax基因及蛋白水平的改变。结果：NSAIDs药物吲哚美辛(Indo)和阿司匹林(Asp)对胃癌细胞株AGS(p53 ／ )、MKN28(p53-／-)均有显著的生长抑制作用，且呈时间／浓度依赖性增强；在相同作用条件下，AGS细胞的凋亡率明显高于MKN28细胞，处理组MKN28细胞凋亡数量虽有所增多，但与正常对照组相比不具有统计学意义；随着药物作用时间的延长，Bcl-2基因mRNA表达逐渐减弱，Bax基因及蛋白表达逐渐增强，在药物作用6～24小时改变最为明显。结论：一定浓度的NSAIDs作用一定时间后，可诱导胃癌细胞凋亡，这为NSAIDs的抗肿瘤应用增加了理论依据；NSAIDs不能诱导p53基因突变的MKN28胃癌细胞株发生显著的凋亡，p53基因突变可能阻断了NSAIDs的凋亡诱导效应；NSAIDs可能通过调控Bcl-2、Bax的基因及蛋白水平而诱导肿瘤细胞凋亡。     

Tamoxifen-induced apoptosis in breast cancer cells relates to down-regulation of bcl-2, but not bax and bcl-X(L), without alteration of p53 protein levels.

Tamoxifen (TAM) has been shown to induce apoptosis in breast cancer cells. bcl-2 family genes, which can interact with each other, have been shown to interfere with apoptosis after various stimuli. In this study, we investigated the effects of TAM on bcl-2 family gene products bcl-2, bax, and bcl-X(L) and on p53 levels in estrogen receptor-positive MCF-7 breast cancer cells. We found that TAM induced time- and concentration-dependent down-regulation of bcl-2 at both the mRNA and protein level. Down-regulation of bcl-2 correlated with TAM-induced apoptosis. In addition, estradiol treatment significantly increased bcl-2 protein expression and blocked the reduction of bcl-2 by TAM. TAM did not, however, affect bax, bcl-X(L), or p53 expression at the mRNA or protein level. Our results demonstrate that TAM can induce apoptosis in a time- and dose-dependent manner by modulating bcl-2 levels in breast cancer cells, and down-regulation of bcl-2 induced by TAM was not accompanied by alterations in p53 levels.     

Neoplastic cell apoptosis in nude mice transplants with nasopharyngeal carcinoma cell lines

We know that tumor growth speed is criticallyinfluenced by the ratio of neoplastic cell proliferation andcell death, and there are two patterns of cell death, namely,necrosis and apoptosis. What is the proportion of necrosisand apoptosis seen in nude mice transplants ofnasopharyngeal carcinoma (NPC) cell lines, CNE-1 andCNE-2? Does the apoptosis play an important role inneoplastic cell death? If so, what is the pathway ofapoptosis developed in those transplants?MATERIALS AND METHODS…     

三七总皂甙对多发性骨髓瘤细胞的增殖抑制作用及机制的研究

目的:观察三七总皂甙(PNS)对多发性骨髓瘤RPMI8226细胞增殖抑制的作用;并观察三七总皂甙与阿霉素(adriamycin,ADM)联合,是否具有协同效应,为三七总皂甙应用于多发性骨髓瘤临床治疗提供一定的实验依据。方法:MTT法检测三七总皂甙对RPMI8226细胞增殖的影响;运用金氏公式分析三七总皂甙与ADM联合的协同效应;RT-PCR法检测Bcl-2、Bax mRNA水平的变化。结果:三七总皂甙可抑制RPMI8226细胞的增殖,并呈剂量依赖性,24h IC50值为213.42±2.21μg/ml;三七总皂甙与ADM联合,表现出协同效应;三七总皂甙与ADM联合处理MM细胞24h后,Bcl-2 mRNA表达较单独应用三七总皂甙或ADM前明显下调,而Bax表达则明显上调。结论:三七总皂甙可以抑制多发性骨髓瘤细胞增殖,联合阿霉素,具有协同效应;其作用可能是通过下调Bcl-2,上调Bax在转录水平的表达而实现的。     

Antisense p53 transduction leads to overexpression of bcl-2 and dexamethasone resistance in multiple myeloma

Multiple myeloma is a malignant proliferation of plasma cells which fail to undergo apoptosis. To understand events associated with lack of apoptosis in these cells, we studied effect of antisense p53 gene transduction in a multiple myeloma cell line, ARH77. Adeno-associated virus was used as a vector to introduce p53 cDNA in an antisense orientation driven by a herpes virus thymidine kinase promoter. We observed, that an antisense p53 (p53as) transduced cell line showed marked reduction in p53 mRNA and protein expression and increased growth when compared to the control cell lines transduced with neomycin-resistance gene or untransduced cells. There was a concomitant up-regulation of bcl-2 expression by over five-fold in p53as-transduced cells compared with controls; while there was no significant change in expression of c-myc and IL-6, genes implicated in myeloma growth. We measured apoptosis in the transduced cells by DNA end-labeling reaction which revealed decrease in apoptosis from 15.6% in control cells to 1.6% in p53as-transduced cells. Additionally, the p53as cells over expressing bcl-2 also showed resistance to killing by dexamethasone. In summary, our data demonstrates that loss of p53 function leads to myeloma cell progression and resistant phenotype through bcl-2-related mechanisms.     

Involvement of bcl-2 and bax gene expression in apoptosis and differentiation of the non-tumorigenic murine hematopoietic cell line, 32DC13(G)

32DCl3(G) is an interleukin-3 (IL-3) dependent, non-tumorigenic murine hematopoietic cell line which undergoes terminal differentiation into granulocytes when exposed to granulocyte-colony stimulating factor (G-CSF). This line therefore offers a convenient system to study the expression of genes involved in apoptosis and differentiation. In our experiments we have acquired evidence that during the differentiation pathway, likewise in apoptosis induced by IL-3 deprivation, detectable levels of bax mRNA appear, while bcl-2 expression decreases. These events are under the control of the p53 tumor-suppressor gene. In these cells, an overexpression of exogenous wild-type p53 leads to a decrease in bcl-2 mRNA and to the appearance of box mRNA, which instead is absent in the parental cells growing in IL-3 conditioned medium. Furthermore, results from experiments on p53 transfected cells demonstrate that excess wild-type p53 activity, on its own, fails to elicit apoptosis as long as IL-3 is present and does not induce differentiation if G-CSF is not added to the culture medium. We conclude that in apoptosis and differentiation of 32DCl3(G) the alterate ratio of bcl-2 and box gene expression, modulated by p53, is an early event dependent on IL-3 withdrawal and that the appearance of bax and the decrease of bcl-2 expression are necessary, but not sufficient for the acquisition of a completely mature granulocytic phenotype.     

全反式维甲酸对食管癌细胞系EC109作用的研究

目的 探讨不同浓度全反式维甲酸(ATRA)对食管癌细胞系EC109的生长抑制作用及其机理.方法 不同浓度ATRA作用于细胞EC109,采用MTT法检测细胞生长;通过流式细胞仪检测和DNA梯状电泳证实凋亡存在;用RT-PCR方法检测凋亡诱导过程中p53、bcl-2和bax基因表达变化.结果 ATRA呈剂量及时间依赖性抑制细胞生长;琼脂糖电泳呈现凋亡DNA梯状条带;流式细胞仪分析存在明显的凋亡峰;ATRA处理组bax和p53基因表达上调,但bcl-2基因表达下调.结论 ATRA具有抑制食管癌细胞株EC109生长作用,其机理可能是诱导细胞凋亡,其分子机制可能与bcl-2/bax和p53的表达相关.     

Imexon-induced apoptosis in multiple myeloma tumor cells is caspase-8 dependent.

PURPOSE: Imexon is a 2-cyanoaziridine agent that has been shown to inhibit growth of chemotherapy-sensitive myeloma cells through apoptosis with decreased cellular stores of glutathione and increased reactive oxygen species (ROS). We examined the mechanism of imexon cytotoxicity in a diverse panel of dexamethasone and chemotherapy-sensitive and -resistant myeloma cell lines. EXPERIMENTAL DESIGN: We examined cellular cytotoxicity, apoptosis, and changes in redox state in dexamethasone-sensitive (C2E3), dexamethasone-resistant (1-310 and 1-414), chemotherapy-sensitive (RPMI-8226), and chemotherapy-resistant (DOX-1V and DOX-10V) myeloma cell lines. RESULTS: We found significant cytotoxicity after 48-h incubation with imexon (80-160 microM) in dexamethasone and chemotherapy-sensitive and -resistant myeloma cell lines in a time- and dose-dependent manner. The mechanism of imexon cytotoxicity in all cell lines was related to induction of apoptosis with the presence of cleaved caspase-3. Moreover, after imexon exposure in C2E3 and 1-414 cell lines, we demonstrated caspase-8-dependent apoptosis. Bcl-2:bax was proapoptotic with imexon in C2E3, whereas bcl-2:bax was independent of steroid resistance, chemotherapy sensitivity, and chemotherapy resistance. Depletion of intracellular glutathione was documented in RPMI-8226 at high imexon concentrations (>or=225 microM) but not in other cell lines. Furthermore, ROS were found in C2E3, RPMI-8226, and 1-310 only at high imexon concentrations, whereas a sensitive marker of oxidative DNA damage, 8-hydroxydeoxyguanosine, was not increased in any cell line. CONCLUSIONS: Our results demonstrate that imexon has significant broad antimyeloma activity that is mediated through apoptotic mechanisms that is not dependent on production of ROS. Moreover, we have identified a mechanism of cytotoxicity in dexamethasone-sensitive and -resistant myeloma cells induced by imexon that is caspase-8 dependent.     

Topoisomerase-I inhibitors for human malignant glioma: Differential modulation of p53, p21, bax and bcl-2 expression and of CD95-mediated apoptosis by camptothecin and β-lapachone

β-lapachone and camptothecin are structurally unrelated agents thought to inhibit topoisomerase-I activity through distinct mechanisms. We find that β-lapachone is much more potent than camptothecin in inducing acute cytotoxic effects on human malignant glioma cells. Acute cytotoxicity induced by both drugs is apoptotic by electron microscopy, but not blocked by inhibitors of RNA or protein synthesis and not associated with changes in the expression of bcl-2, bax, p53, p21 or GADD45 proteins. In contrast, prolonged exposure of glioma cells to both drugs for 72 hr results in growth inhibition and apoptosis, with EC₅₀ values around 1 μM. None of 7 glioma cell lines tested were resistant to either drug. LN-229 cells which have partial p53-wild-type activity show enhanced expression of p53, p21 and bax protein, whereas bcl-2 levels decrease, after exposure to camptothecin. In contrast, β-lapachone increases bax protein expression in the absence of p53 activation. T98G cells are mutant for p53. In these cells, p53 levels do not change and p21 is not induced. bax accumulation in T98G cells is induced by both drugs, with bcl-2 levels unaltered. Surprisingly, ectopic expression of murine bcl-2 fails to abrogate the toxicity of either drug. Camptothecin, but not β-lapachone, sensitizes human malignant glioma cells to apoptosis induced by the cytotoxic cytokines, tumor necrosis factor-α and CD95 ligand. Thus, both drugs have potent anti-glioma activity that may be mediated by enhanced bax expression but is not inhibited by ectopic bcl-2 expression. Camptothecin-like agents are particularly promising for immunochemotherapy of malignant glioma using cytotoxic drugs and CD95 ligand. Int. J. Cancer 73:707–714, 1997. © 1997 Wiley-Liss, Inc.     

Growth inhibition, cell-cycle arrest and apoptosis in human T-cell leukemia by the isothiocyanate sulforaphane

Glucosinolates (GL) can inhibit, retard or reverse experimental multistage carcinogenesis. When brassica plant tissue is broken, GLs are hydrolyzed by the endogenous enzyme myrosinase (Myr), releasing many products including isothiocyanates (ITC). Synthetic ITCs like sulforaphane exert chemopreventive effects against chemically induced tumors in animals, modulating enzymes required for carcinogens' activation/detoxification and/or the induction of cell-cycle arrest and apoptosis in tumor cell lines. To investigate the chemopreventive potential of ITCs while reproducing the circumstances of dietary contact with sulforaphane, we studied proliferation, apoptosis induction and p53, bcl-2 and bax protein expression in Jurkat T-leukemia cells by sulforaphane, the ITC generated in situ in a quantitative manner by Myr starting from glucoraphanin (GRA). Jurkat cells were treated with different doses of GRA-Myr mixture. Effects on cell growth or survival were evaluated by counting trypan blue-excluding cells. Cell-cycle progression, apoptosis and expression of p53, bax and bcl-2 proteins were analyzed by flow cytometry. Results were analyzed by two-sided Fisher's exact test. Sulforaphane, but not GRA, caused G(2)/M-phase arrest (P = 0.028) and increase of apoptotic cell fraction (P < 0.0001) in a time- and dose-dependent manner. Necrosis was observed after prolonged exposure to elevated sulforaphane doses. Moreover, it markedly increased p53 and bax protein expression, and slightly affected bcl-2 expression. These findings indicate that sulforaphane but not the native GL GRA can exert both protective and toxic effects inhibiting leukemic cell growth. Sulforaphane therefore deserves study as a potential chemopreventive/chemotherapeutic antileukemic agent.     

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.     

Expression of bcl-2 and bax in chewing tobacco-induced oral cancers and oral lesions from India

Deregulation of oncogenes and tumor suppressor genes involved in apoptosis has been associated with tumor development and progression. To investigate the involvement of apoptosis regulating proteins in oral cancer in Indian patients, primarily associated with chewing tobacco habits, immunohistochemical expression of bcl-2 and bax was examined in 63 oral squamous cell carcinomas, and 31 putative premalignant lesions. Our studies revealed overexpression of tumor specific cytoplasmic bcl-2 in 56% and bax in 43% oral cancers. The oral cancers in the Indian patients are preceded by premalignant oral lesions; hence oral lesions were examined for bcl-2 and bax expression. We observed aberrant expression of bcl-2 in 16% oral lesions comprising leukoplakias and SMF and bax in 55% oral lesions. We have already reported, p53 expression in these oral cancers and lesions. It was noteworthy that 30% oral cancers demonstrated a p53+bcl2+ pattern, and 14% samples exhibited p53+bcl2+bax+ pattern. However, none of the oral lesions showed concurrent deregulation of p53 and bcl-2 or all the three genes. Interestingly 45% oral lesions were p53-bax+ as compared to 18% oral cancers; while 39% oral lesions were bcl2-bax+ as compared to 14% oral cancers, indicating overexpression of bax in oral lesions, in the absence of p53 and bcl-2 proteins. Significant correlation was observed between positive nodal status and bcl2+ (p=0.047) and p53+bcl-2+ (p=0.01) in oral cancers. Kaplan Meier survival analysis showed significantly (p=0.059) higher survival in patients with p53- oral tumors than with p53+ tumors. Our studies thus indicate frequent overexpression of apoptosis regulators bcl-2, bax and p53 proteins in oral cancers, and a subset of oral lesions, representing early events in oral car-cinogenesis. The aberrant bcl-2 expression and loss of p53 function observed, may play an important role in the tumorigenesis of oral cancers by allowing escape from apoptosis and enabling additional genetic alterations to accrue.