Proteomic Analysis Reveals that Odoroside A Triggers G2/M Arrest and Apoptosis in Colorectal Carcinoma Through ROS‐p53 Pathway

Odoroside A (OA) is an active ingredient extracted from the leaves of Nerium oleander Linn. (Apocynaceae). This study aims to examine the anticancer bioactivity of OA against CRC cells and to investigate the action mechanisms involved. As a result, OA can significantly inhibit cellular ability and induce apoptosis of CRC cells in a concentration‐dependent manner without any obvious cytotoxicity in normal colorectal epithelial cells. Then, quantitative proteomics combined with bioinformatics is adopted to investigate the alterations of proteins and signaling pathways in response to OA treatment. As suggested by the proteomic analysis, flow cytometry and Western blotting analyses validate that exposure of CRC cells to OA causes cell cycle arrest and apoptosis, accompanied with the activation of the ROS/p53 signaling pathway. This observation demonstrates that OA, as a natural product, can induce oxidative stress to suppress tumor cell growth, implicating a novel therapeutic agent against CRC without obvious side effects.     

褪黑素通过提高p53和Fas的表达促进小鼠肝癌H22细胞凋亡

目的：研究褪黑素（MLT）对小鼠肝癌细胞株H22的促凋亡作用及其机理。方法：采用丫啶橙（AO）染色、培养液乳酸脱氢酶（LDH）活性检测和流式细胞术（FCM）观察MLT的促凋亡作用;采用RT-PCR方法检测MLT处理前后细胞的p53 mRNA、Fas mRNA的水平。结果：AO染色后H22细胞呈现明显核浓缩的凋亡形态;培养液LDH活性检测及FCM分析均提示MLT诱导H22细胞发生凋亡;RT-PCR结果显示p53、Fas表达增强。结论：MLT能促进H22细胞p53和Fas的表达,从而诱导细胞发生凋亡。     

探究新辅助化疗对胃癌细胞Bcl-2和p53基因表达的影响

胃癌在中国的发病率和死亡率居恶性肿瘤前列,现在胃癌的治疗主要以手术和化疗为主的综合治疗,新辅助化疗是胃癌综合治疗的重要组成部分,通过新辅助化疗能够有效抑制癌细胞增殖、缩小肿瘤体积等优点,从而为手术切除创造条件。本研究用新辅助化疗处理患胃癌的小鼠,并检测了新辅助化疗处理前后胃癌细胞内p53和Bcl-2 (细胞凋亡相关因子)基因在组织内的表达变化情况,以及与对照相比新辅助化疗对肿瘤大小的影响。结果表明,新辅助化疗可以减缓肿瘤的增长,显著上调小鼠胃癌组织内细胞凋亡因子p53的表达,并且显著下调Bcl-2抗凋亡因子的表达,从而有效地抑制胃癌细胞的增殖。这一结果可能为新辅助化疗对胃癌的治疗分子机制提供一些理论支持。     

雷公藤甲素诱导HeLa细胞p53依赖的自噬和凋亡

自噬与凋亡被认为是细胞程序性死亡的两种重要途径,二者的交互联系对阐明药物的抗肿瘤机理有重要价值.众多的研究表明,雷公藤甲素对多种肿瘤细胞都具有显著的抑制作用.细胞凋亡与自噬可被相同的因素所诱导,p53蛋白可以同时对二者起调控作用,在自噬与凋亡的交互作用(crosstalk)中扮演着重要角色.本文以He La细胞为模型,研究雷公藤甲素诱导He La细胞发生自噬和凋亡的机制,并通过抑制p53依赖的转录,研究雷公藤甲素诱导He La细胞p53依赖的自噬和凋亡交互联系.     

p53 and p21(Waf1) Are Recruited to Distinct PML‐Containing Nuclear Foci in Irradiated and Nutlin‐3a‐Treated U2OS Cells

Promyelocytic leukemia nuclear bodies (PML‐NBs) are multiprotein complexes that include PML protein and localize in nuclear foci. PML‐NBs are implicated in multiple stress responses, including apoptosis, DNA repair, and p53‐dependent growth inhibition. ALT‐associated PML bodies (APBs) are specialized PML‐NBs that include telomere‐repeat binding‐factor TRF1 and are exclusively in telomerase‐negative tumors where telomere length is maintained through alternative (ALT) recombination mechanisms. We compared cell‐cycle and p53 responses in ALT‐positive cancer cells (U2OS) exposed to ionizing radiation (IR) or the p53 stabilizer Nutlin‐3a. Both IR and Nutlin‐3a caused growth arrest and comparable induction of p53. However, p21, whose gene p53 activates, displayed biphasic induction following IR and monophasic induction following Nutlin‐3a. p53 was recruited to PML‐NBs 3–4 days after IR, approximately coincident with the secondary p21 increase. These p53/PML‐NBs marked sites of apparently unrepaired DNA double‐strand breaks (DSBs), identified by colocalization with phosphorylated histone H2AX. Both Nutlin‐3a and IR caused a large increase in APBs that was dependent on p53 and p21 expression. Moreover, p21, and to a lesser extent p53, was recruited to APBs in a fraction of Nutlin‐3a‐treated cells. These data indicate (1) p53 is recruited to PML‐NBs after IR that likely mark unrepaired DSBs, suggesting p53 may either be further activated at these sites and/or function in their repair; (2) p53–p21 pathway activation increases the percentage of APB‐positive cells, (3) p21 and p53 are recruited to ALT‐associated PML‐NBs after Nutlin‐3a treatment, suggesting that they may play a previously unrecognized role in telomere maintenance. J. Cell. Biochem. 111: 1280–1290, 2010. © 2010 Wiley‐Liss, Inc.     

Zinc Induces Expression of the BH3-only Protein PUMA Through p53 and ERK Pathways in SH-SY5Y Neuroblastoma Cells

Accumulating evidence suggests that zinc (Zn²⁺) contributes to neuronal death in pathologic states such as ischemia. p53-upregulated modulator of apoptosis (PUMA), which is a BH3-only protein, is known to promote apoptosis through a tumor suppressor p53-dependent and -independent mechanism. In this study, we examined the effect of Zn²⁺ on the induction of the PUMA gene in human neuroblastoma SH-SY5Y cells. The expression of PUMA was induced by Zn²⁺ in a dose- and time-dependent manner. A reporter assay revealed that Zn²⁺ activated the PUMA promoter. In addition, the mutation of the p53 binding site in the PUMA promoter region reduced promoter activation by Zn²⁺. These findings suggest that p53 participates in Zn²⁺-induced PUMA expression. Furthermore, we also demonstrated here that Zn²⁺ stimulates the phosphorylation of ERK and that the MEK-ERK pathway inhibitor, U0126, suppressed Zn²⁺-induced PUMA expression. Taken together, these results indicate that Zn²⁺ regulates the induction of PUMA through p53 and ERK pathways.