Involvement of the intrinsic and extrinsic cell‐death pathways in the induction of apoptosis of mature lymphocytes by the Escherichia coli heat‐labile enterotoxin

Escherichia coli heat‐labile enterotoxin (LT) exhibits a broad range of immunomodulatory activities, including the induction of lymphocyte‐programmed cell death. In previous studies, we have demonstrated that in vivo LT promotes apoptosis of immature T and B cells through the stimulation of endogenous glucocorticoids. In the present study, we show that the extrinsic cell‐death pathway as well as the apoptosis‐inducing factor do not participate in the LT‐induced elimination of thymocytes. In contrast to developing lymphocytes, LT promotes the death of mature lymphocytes by both glucocorticoid‐ and Fas death receptor/Fas ligand‐dependent mechanisms. However, the dependency of these mechanisms in the LT‐induced cell‐death activity seems to be different among CD4⁺ and CD8⁺ T cells. Altogether, our study shows that the same bacterial toxin can induce apoptosis of lymphoid cells through several mechanisms depending on the status of differentiation of these cells.     

Association of early phase of colorectal carcinogenesis with STAT3 activation and its relevance in apoptosis regulation

Expression of STAT3/pSTAT3 in colorectal cancer (CRC) patients of Indian origin was studied to assess its significance in early detection and apoptosis regulation. Colorectal tissues with malignant lesions were STAT3/pSTAT3 positive in 66% of the cases and among these positive cases, well differentiated, moderately differentiated and poorly differentiated cancers were 86%, 60% and 0% respectively. All CRC specimens studied were immunoreactive with anti-carcinoembryonic antigen antibody. Cells purified from CRC tissues exhibited greater STAT3/pSTAT3 reactivity than peripheral blood mononuclear cells (PBMC) from healthy individuals, which served as control. apoptotic index (AI) was comparatively low in tissue specimens with STAT3/pSTAT3 expression. CRC cells with a comparatively less number of apoptotic cells, expressed a minimum number of Caspase-3 positive cells (4.73%), in comparison to healthy-PBMC (12.63%). CRC cells with high STAT3/pSTAT3 staining had cells with greater percentage of Bcl2 reactivity (23.05%), but less positivity with Caspase3 antibody (2.05%). Overall data suggests that CRC population was STAT3/pSTAT3 immunoreactive in a stage specific manner and STAT3 protects cancerous colorectal epithelial cells from apoptosis. Bcl-2, Cyclin D1 and Caspase-3 control the activity of apoptosis regulator, STAT3.     

Autophagy in cancer: having your cake and eating it

Autophagy, one of two major intracellular degradation pathways, plays a critical role in energy homeostasis and the quality control of macromolecules and intracellular organelles. Previous work has demonstrated the importance of autophagy in maintaining cellular fitness, both in healthy and stressful conditions, revealing the complex interplay between autophagy and other stress-responsive phenotypes. The complex outcomes of stress-responsive autophagy confer on it both pro- and anti-tumourigenic roles, depending on the cellular and environmental context. Furthermore, recent findings that functionally link autophagy to the tumour suppressor mechanism, cellular senescence, have revealed a new role of autophagy in cancer biology. In this review we summarise the current evidence on the relationship between autophagy and cancer, with a focus on its role in senescence.     

环氧化酶-2、p53和Bcl-2在胃癌组织中的表达及其意义

目的检测环氧化酶-2（cyclooxygenase-2,COX-2）、p53和Bcl-2在胃癌组织中的表达,并探讨其意义。方法利用半定量RT—PCR法检测80例胃腺癌及对应的癌旁组织和正常胃组织中COX-2的表达情况;采用免疫组化技术检测80例胃腺癌及对应的癌旁组织和正常组织中p53、Bcl-2的表达情况。结果（1）COX-2阳性表达率分析,COX-2阳性表达率在胃癌组织明显高于相应的癌旁组织和正常组织（0．025〈P〈0．05）,COX-2在低分化的胃腺癌中的阳性表达率高于中高分化类型的胃腺癌（0．01〈P〈0．025）;（2）p53基因表达率在胃癌组织明显高于相应的癌旁组织和正常组织（P〈0．005）,p53基因在低分化胃癌中的阳性表达率明显高于高分化类型的胃腺癌（O．01〈P〈0．025）。（3）Bcl-2基因在胃癌组织的表达率明显高于相应的癌旁组织和正常组织（P〈0．005）,Bcl-2基因表达率在低分化类型的胃腺癌中的阳性表达率明显高于中高分化类型胃腺癌（P〈0．005）。结论COX-2、p53、Bcl-2与胃癌的发生相关,COX-2和Bcl-2在不同分化类型的胃癌组织中的表达差异均具有显著性统计学意义,p53在低分化与高分化腺癌组织中的表达差异有显著性意义,因此可以用来判断肿瘤的预后。     

Pinocembrin triggers Bax-dependent mitochondrial apoptosis in colon cancer cells

Bioflavanoids are the major pigments in plants with multitude of biological activities including inhibition of proliferation or induction of apoptosis in tumor cells. Even though the safety records of most flavanoids are exceptional, its therapeutic use is still in its infancy. We have isolated pinocembrin (5,7-dihydroxyflavanone) from Alpinia galanga that showed cytotoxicity against a variety of cancer cells including normal lung fibroblasts with relative nontoxicity to human umbilical cord endothelial cells. The compound induced loss of mitochondrial membrane potential with subsequent release of cytochrome c and processing of caspase-9 and -3 in colon cancer cell line HCT 116. Processing of caspase-8 was minimal. The initial trigger for mitochondrial apoptosis appears to be by the translocation of cytosolic Bax protein to mitochondria. Overexpression of proapoptotic Bax protein sensitized the colon cancer cells to pinocembrin-induced apoptosis and Bax knockout cells were resistant to pinocembrin-induced apoptosis. Antiapoptotic protein Bcl-X(L) only partially prevented apoptosis induced by this compound. The Bax-dependent cell death involving classical cytochrome c release and processing of caspase-9 and -3 suggests that pinocembrin is a classical mitochondrial apoptosis inducer. But the failure of Bcl-X(L) overexpression to completely prevent apoptosis induced by this compound suggests that pinocembrin is capable of triggering mitochondrial-independent cell death that needs to be clarified. The existence of cell death upon Bcl-X(L) overexpression is a promising feature of this compound that can be exploited against drug resistant forms of cancer cells either alone or in combination with other drugs.     

Bcl‐XL and MCL‐1 constitute pertinent targets in ovarian carcinoma and their concomitant inhibition is sufficient to induce apoptosis

In ovarian carcinomas, recurrence and acquired chemoresistance are the first leading causes of therapeutic failure and are responsible for the poor overall survival rate. Cisplatin exposure of sensitive cells has been previously associated with a down‐regulation of Bcl‐X_L expression and apoptosis, whereas recurrence was systematically observed when Bcl‐X_L expression was maintained. Bcl‐X_L down‐regulation could thus constitute an interesting chemosensitizing strategy. We showed that a Bcl‐X_L targeted RNA interference strategy efficiently sensitized chemoresistant ovarian carcinoma cells to cisplatin, but some of them were still able to re‐proliferate. Considering the possible cooperation between Bcl‐X_L and MCL‐1, we investigated the possibility to avoid recurrence in vitro using a multi‐targeted RNAi strategy directed against these two anti‐apoptotic proteins. We showed that their concomitant inhibition lead to massive apoptosis in absence of cisplatin, this multi‐targeted RNAi approach being much more efficient than conventional chemotherapy. We thus demonstrated that Bcl‐X_L and MCL‐1 cooperate to constitute together a strong molecular “bolt”, which elimination could be sufficient to allow chemoresistant ovarian carcinoma cells apoptosis. Moreover, we demonstrated that in presence of a low concentration of cisplatin, the concomitant down‐regulation of Bcl‐X_L and MCL‐1 allowed a complete annihilation of tumour cells population thus avoiding subsequent recurrence in vitro in cell lines highly refractory to any type of conventional chemotherapy. Therefore, Bcl‐X_L and MCL‐1 targeted strategies could constitute an efficient therapeutic tool for the treatment of chemoresistant ovarian carcinoma, in association with conventional chemotherapy.     

抗氧化剂和Ca2+清除剂调控As2O3诱导白血病细胞凋亡中Bcl-2和p53的表达

目的: 研究抗氧化剂NAC, NDMS, CAT和Ca2+清除剂Quin 2调控As2O3诱导白血病细胞株NB4, K562, HL-60凋亡时Bcl-2和p53表达的作用. 方法: 不同浓度As2O3处理细胞内Bcl-2和p53用相应抗体标记, 并用流式细胞仪检测. 结果: 0.6,2.7和8.1 μmol*L-1 As2O3作用72 h能诱导NB4, K562和HL-60发生0.45±0.04, 0.58±0.06和0.62±0.08凋亡, 上述浓度药物能使NB4, K562, HL-60 3种细胞中Bcl-2蛋白的平均荧光强度分别由109±31, 101±32, 87±23下降到68±22, 54±33, 66±18.相反, 可使3种细胞中p53蛋白的平均荧光强度分别由18±5, 2±1, 3±1上升到30±9, 15±6, 28±8. 而抗氧化剂NAC, NDMS, CAT和Ca2+清除剂Quin 2对3种细胞内Bcl-2和p53表达没有显著影响, 但能抑制As2O3引起的p53表达上调. 对As2O3引起的Bcl-2下降则显示了不同的调控作用. 结论: As2O3诱导的Bcl-2下降、p53上升和细胞凋亡可被抗氧化剂和Ca2+清除剂抑制.     

睾丸肿瘤bax和bcl-2蛋白的流式细胞定量研究

目的研究bax和bcl-2蛋白表达在睾丸肿瘤发生发展中的作用。方法应用流式细胞术和细胞免疫荧光技术检测56例睾丸肿瘤bax和bcl-2蛋白的表达。结果bax阳性48例(85.7%),bcl-2阳性40例(71.4%);bax和bcl-2蛋白表达与肿瘤的病理类型、临床分期和淋巴结转移无明显相关(P>0.05)。结论bax和bcl-2蛋白的异常表达尚不能成为睾丸肿瘤发生发展的预后参数。     

放射复合伤口愈合中外周血淋巴细胞凋亡及其与愈合延迟的关系

为研究放射复合伤口愈合中外周血淋巴细胞凋亡规律并探讨其与愈合延迟的关系，将120只大鼠随机分为单纯创伤组与创伤复合照射组，用原位末端标记（TUNEL）方法检测细胞凋亡，碱磷酶免疫组织化学方法检测Bax,Bcl-2蛋白表达，结果发现，创伤复合照射组动物白细胞数出现下降，伤后3天降至最低，伤后5天仍显著低于单纯创伤组；伤后两组动物中血淋巴细胞凋亡率均升高，但创伤照射组凋亡率始终高于单纯创伤组；伤后不同时间淋巴细胞Bax蛋白出现升高，创伤照射组明显高于单纯创伤组，而Bcl-2呈现相反的变化趋势，该结果提示，照射后外周血白细胞数的降低和淋巴细胞凋亡的增加是辐射延迟伤口愈合的重要原因，Bax和Bcl-2蛋白参与了淋巴细胞凋亡的调控。