Programmed cell death 50 (and beyond)

In the 50 years since we described cell death as ‘programmed,'' we have come far, thanks to the efforts of many brilliant researchers, and we now understand the mechanics, the biochemistry, and the genetics of many of the ways in which cells can die. This knowledge gives us the resources to alter the fates of many cells. However, not all cells respond similarly to the same stimulus, in either sensitivity to the stimulus or timing of the response. Cells prevented from dying through one pathway may survive, survive in a crippled state, or die following a different pathway. To fully capitalize on our knowledge of cell death, we need to understand much more about how cells are targeted to die and what aspects of the history, metabolism, or resources available to individual cells determine how each cell reaches and crosses the threshold at which it commits to death.     

Association of the programmed cell death 1 (PDCD1) gene polymorphism with ankylosing spondylitis in the Korean population

The PD-1 (programmed death 1) molecule is a negative regulator of T cells. PDCD1 (programmed cell death 1) has been reported to have a genetic association in systemic lupus erythematosus and rheumatoid arthritis in Caucasians. However, there are no reports on the association between this gene and ankylosing spondylitis (AS). The present study investigated the association of the PD-1 polymorphisms and the haplotypes with AS in a Korean population sample. In a case-control association study, two single-nucleotide polymorphisms, PD-1.5 C/T and PD-1.9 T/C, were genotyped in 95 AS patients and 130 healthy controls. The T allele of the PD-1.9 polymorphism was more frequent in the Korean male population with AS than in the Korean male controls (21.0% versus 6.9%, odds ratio 1.89, 95% confidence interval 1.483 to 2.408). The frequency of the CT haplotype (PD-1.5 C/T and PD-1.9 T/C) was higher in the AS patients (19%) than the controls (5.4%) (odds ratio 1.83, 95% confidence interval 1.559 to 2.521). The PD-1 polymorphism was demonstrated in Korean AS patients. The results suggest a genetic association between the PD-1 polymorphism and susceptibility to AS.     

Programmed cell death 4 (PDCD4) mediates the sensitivity of gastric cancer cells to TRAIL-induced apoptosis by down-regulation of FLIP expression

Tumor necrosis factor-related apoptosis induced ligand (TRAIL) is an important apoptosis inducer in a variety of tumor cells. In the present study, we determined the underlying molecular mechanisms by which certain gastric cancer cells are resistant to TRAIL. We first detected expression of programmed cell death 4 (PDCD4) in three gastric cancer cell lines and identified its association with the sensitivity of gastric cancer cells to TRAIL. We then stably transfected PDCD4 cDNA or shRNA into these gastric cell lines. Our data showed that restoration of PDCD4 expression induced TRAIL sensitivity, whereas knockdown of PDCD4 expression reduced the sensitivity of these tumor cells to TRAIL treatment. PDCD4 was able to suppress expression of FLICE-inhibiting protein (FLIP), a negative regulator of apoptosis. Knockdown of FLIP expression using FLIP shRNA had similar effects as those of restored PDCD4 expression. Furthermore, the proteasome inhibitor MG132 was able to inhibit expression of FLIP mRNA and protein and upregulate the sensitivity of these cells to TRAIL treatment. Taken together, the results from the current study demonstrated that PDCD4 plays an important role in mediating the sensitivity of gastric cancer cells to TRAIL-induced apoptosis through FLIP suppression. Therefore, the proteasome inhibitor MG132 should be further evaluated for combination therapy with TRAIL.     

Expression of programmed cell death protein 4 (PDCD4) and miR-21 in urothelial carcinoma

BackgroundWe investigated the role of the programmed cell death 4 (PDCD4) tumor suppressor gene in specimens of transitional cell carcinoma and of healthy individuals.MethodsPDCD4 immunohistochemical expression was investigated in 294 cases in histologically proven transitional cell carcinoma in different tumorous stages (28 controls, 122 non-muscle invasive urothelial carcinoma, stages Tis-T1, 119 invasive transitional cell carcinoma stages T2–T4 and 25 metastases). MiR-21 expression, an important PDCD4 regulator, was assessed with real-time PCR analysis and showed inverse correlation to tissue PDCD4 expression.ResultsNuclear and cytoplasmatic PDCD4 immunostaining decreased significantly with histopathological progression of the tumor (p < 0001). Controls showed strong nuclear and cytoplasmatic immunohistochemical staining. MiR-21 up regulation in tissue corresponded to PDCD4 suppression.ConclusionsThese data support a decisive role for PDCD4 down regulation in transitional cell carcinoma and confirm miR-21 as a negative regulator for PDCD4. Additionally, PDCD4 immunohistochemical staining turns out to be a possible diagnostic marker for transitional cell carcinoma.     

Programmed cell death 4 (PDCD4) is an important functional target of the microRNA miR-21 in breast cancer cells

MicroRNAs are emerging as important regulators of cancer-related processes. The miR-21 microRNA is overexpressed in a wide variety of cancers and has been causally linked to cellular proliferation, apoptosis, and migration. Inhibition of mir-21 in MCF-7 breast cancer cells causes reduced cell growth. Using array expression analysis of MCF-7 cells depleted of miR-21, we have identified mRNA targets of mir-21 and have shown a link between miR-21 and the p53 tumor suppressor protein. We furthermore found that the tumor suppressor protein Programmed Cell Death 4 (PDCD4) is regulated by miR-21 and demonstrated that PDCD4 is a functionally important target for miR-21 in breast cancer cells.     

Programmed cell death protein 5 (PDCD5) is phosphorylated by CK2 in vitro and in 293T cells

CK2 is a multifunctional kinase, involved in cell growth, apoptosis, DNA integrity preservation, viral infection, and many other biological processes. Based on an analysis of phosphopeptides database derived from phosphoproteomic studies we previously identified a list of potential new CK2 substrates, including, among others, Programmed Cell Death 5 (PDCD5), a protein involved in cell death and down-regulated in different forms of human tumors. Here we provide experimental evidence that PDCD5 is indeed a bona fide substrate of CK2. PDCD5 is phosphorylated in vitro by both CK2α subunit and by the CK2 holoenzyme at a residue, S118, which is found phosphorylated in vivo. We also show that PDCD5 is phosphorylated by CK2 in 293T cells. Transfection of the non-phosphorylatable mutant (S118A) impairs the PDCD5 acceleration of either doxorubimicin- or UV-induced apoptosis in U2OS cells. Our results suggest a functional link between the CK2 phosphorylation and the apoptotic potential of PDCD5.     

细胞程序性死亡与生态适应

细胞程序性死亡是多细胞有机生命周期中正常的组成部分,细胞程序性死亡过程的存在对生物体是一种保护机制。它是在生物进化过程中形成的,也是生物对环境的适应方式之一。     

程序性细胞死亡与肿瘤

程序性细胞死亡（programmed cell death,PCD）是指由基因控制的细胞自主的有序性死亡方式,涉及一系列基因的激活、表达以及调控等。目前,经典细胞凋亡被称为Ⅰ型PCD,而自噬性细胞死亡称为Ⅱ型PCD,坏死样程序性细胞死亡则被称为Ⅲ型PCD,它们在肿瘤的发生、发展及治疗过程中起非常重要的作用。该文结合国内外最新研究进展主要针对不同细胞死亡模式及其相互作用、关键作用蛋白,细胞自噬与肿瘤发生,细胞自噬、凋亡与肿瘤治疗作一简要综述,并展望发展前景,提出在肿瘤治疗中如何利用不同死亡模式的协同作用最大限度地发挥其临床应用价值。     

Increased dermal mast cell prevalence and susceptibility to development of basal cell carcinoma in humans

Exposure to ultraviolet B (UVB) radiation (280-320 nm) is the primary etiologic factor associated with the development of basal cell carcinoma (BCC). The outgrowth of these keratinocyte-derived skin lesions is enhanced by the ability of UVB to impair an immune response that would otherwise eliminate them. Studies in a range of inbred mouse strains as well as mast cell-depleted mice reconstituted with mast cell precursors support a functional link between histamine-staining dermal mast cells and the extent of susceptibility to UVB-induced systemic immunomodulation. Humans, like mouse strains, display variations in dermal mast cell prevalence. In a study of Danish and South Australian BCC patients and control subjects, one 4-mm punch biopsy of non-sun-exposed buttock skin was sampled from each participant. This skin site was investigated to avoid any changes in mast cell prevalence caused by sun exposure. Two sections (4 microm) per biopsy were immunohistochemically stained for detection of histamine-containing dermal mast cells. Computer-generated image analysis evaluated dermal mast cell prevalence in both sections by quantifying the total number of mast cells according to the total dermal area (expressed as mast cells per square millimeter). This technique enabled us to detect heterogeneity of dermal mast cell prevalence in buttock skin between individuals and provided evidence of an association between high dermal mast cell prevalence and BCC development in two diverse populations. We hypothesize that mast cells function in humans, as in mouse strains, by initiating immunosuppression following UV irradiation and, thereby, allowing a permissive environment for the development of BCC. Thus, a high dermal mast cell prevalence as demonstrable in buttock skin is a significant predisposing factor for development of BCC in humans.     

Programmed cell death and the gene behind spinal muscular atrophy.

A gene involved in the development of spinal muscular atrophy (SMA) has been found on human chromosome 5 after a 4-year search. Named the neuronal apoptosis inhibitor protein (NAIP) gene, it is believed to inhibit the normal process of apoptosis--the disintegration of single cells that results from programmed cell death--in motor neurons. The researchers who found the NAIP gene also discovered that healthy people carry one complete copy of the gene along with many other partial copies. Many children with SMA have the partial copies but not the complete gene. This discovery facilitates the accurate genetic diagnosis of SMA. But gene therapy for SMA will not be possible until researchers find a suitable vector to stably introduce activated and intact copies of the gene into the motor neurons of children with SMA in time to stop motor neuron loss.     

MicroRNA-21 promotes cell proliferation and down-regulates the expression of programmed cell death 4 (PDCD4) in HeLa cervical carcinoma cells

MicroRNAs are involved in cancer-related processes. The microRNA-21(miR-21) has been identified as the only miRNA over-expressed in a wide variety of cancers, including cervical cancer. However, the function of miR-21 is unknown in cervical carcinomas. In this study, we found that the inhibition of miR-21 in HeLa cervical cancer cells caused profound suppression of cell proliferation, and up-regulated the expression of the tumor suppressor gene PDCD4. We also provide direct evidence that PDCD4-3′UTR is a functional target of miR-21 and that the 18 bp putative target site can function as the sole regulatory element in HeLa cells. These results suggest that miR-21 may play an oncogenic role in the cellular processes of cervical cancer and may serve as a target for effective therapies.     

Programmed cell death and hybrid incompatibility

We propose a new theory to explain developmental aberrations in plant hybrids. In our theory, hybrid incompatibilities arise from imbalances in the mechanisms that cause male sterility in hermaphroditic plants. Mitochondria often cause male sterility by killing the tapetal tissue that nurtures pollen mother cells. Recent evidence suggests that mitochondria destroy the tapetum by triggering standard pathways of programmed cell death. Some nuclear genotypes repress mitochondrial male sterility and restore pollen fertility. Normal regulation of tapetal development therefore arises from a delicate balance between the disruptive effects of mitochondria and the defensive countermeasures of the nuclear genes. In hybrids, incompatibilities between male-sterile mitochondria and nuclear restorers may frequently upset the regulatory control of programmed cell death, causing tapetal abnormalities and male sterility. We propose that hybrid misregulation of programmed cell death may also spill over into other tissues, explaining various developmental aberrations observed in hybrids.     

Programmed cell death and the proteasome

A characteristic feature of apoptotic cell death is the activation of a cascade of cytoplasmic proteases that results in the cleavage of a limited number of target proteins. A central role in these proteolytic events has been assigned to members of the capase family. However, the use of low molecular weight proteasomal inhibitors has also demonstrated that protein degradation or processing by the ubiquitin-proteasome system of the cell has a decisive impact on cell survival and death as well, depending on the cell type and/or the proliferative status of the cells studied. Treatment of proliferating cells with proteasome inhibitors leads to cell death, potentially involving an internal signalling conflict between accumulating levels of the cdk inhibitor p27Kip1 and c-myc. In contrast, in terminally differentiated cells the same compounds have the opposite effect of blocking apoptosis, possibly by preventing proteasome-mediated degradation of a capase inhibitor. In this review the role of proteasome-mediated proteolysis in the dying cell is discussed and apparently conflicting results are integrated into a working hypothesis which functionally locates the proteasome upstream of capase3-like enzymes.     

Nevoid basal cell carcinoma syndrome (Gorlin syndrome)

Brachydactyly ("short digits") is a general term that refers to disproportionately short fingers and toes, and forms part of the group of limb malformations characterized by bone dysostosis. The various types of isolated brachydactyly are rare, except for types A3 and D. Brachydactyly can occur either as an isolated malformation or as a part of a complex malformation syndrome. To date, many different forms of brachydactyly have been identified. Some forms also result in short stature. In isolated brachydactyly, subtle changes elsewhere may be present. Brachydactyly may also be accompanied by other hand malformations, such as syndactyly, polydactyly, reduction defects, or symphalangism. For the majority of isolated brachydactylies and some syndromic forms of brachydactyly, the causative gene defect has been identified. In isolated brachydactyly, the inheritance is mostly autosomal dominant with variable expressivity and penetrtance. Diagnosis is clinical, anthropometric and radiological. Prenatal diagnosis is usually not indicated for isolated forms of brachydactyly, but may be appropriate in syndromic forms. Molecular studies of chorionic villus samples at 11 weeks of gestation and by amniocentesis after the 14^th week of gestation can provide antenatal diagnosis if the causative mutation in the family is known. The nature of genetic counseling depends both on the pattern of inheritance of the type of brachydactyly present in the family and on the presence or absence of accompanying symptoms. There is no specific management or treatment that is applicable to all forms of brachydactyly. Plastic surgery is only indicated if the brachydactyly affects hand function or for cosmetic reasons, but is typically not needed. Physical therapy and ergotherapy may ameliorate hand function. Prognosis for the brachydactylies is strongly dependent on the nature of the brachydactyly, and may vary from excellent to severely influencing hand function. If brachydactyly forms part of a syndromic entity, prognosis often depends on the nature of the associated anomalies.     

Up-regulation of TRPV1 in mononuclear cells of end-stage kidney disease patients increases susceptibility to N-arachidonoyl-dopamine (NADA)-induced cell death

Transient receptor potential vanilloid (TRPV) 1 channels function as sensors for a variety of noxious and inflammatory signals, including capsaicin, heat and protons, and are up-regulated under inflammatory conditions. As end-stage kidney disease (ESKD) is associated with chronic inflammation, impaired immunity and depressed lymphocyte numbers, we sought to determine whether altered TRPV1 (and related TRPV2) expression in immune cells might be a contributing factor. TRPV1 and TRPV2 mRNA expression in peripheral blood mononuclear cells (PBMC) was similar in controls and ESKD patients by quantitative real-time RT-PCR. However, using immunocytochemistry, TRPV1-immunoreactivity was significantly higher and TRPV2-immunoreactivity was significantly lower in PBMC from ESKD patients compared to controls. The plant-derived TRPV1 agonists, capsaicin and resiniferatoxin (RTX) and the putative endovanilloid/endocannabinoids, N-arachidonoyl-dopamine (NADA) and N-oleoyl-dopamine (OLDA), induced concentration-dependent death of PBMC from healthy donors with a rank order of potency of RTX > NADA > OLDA >> capsaicin. TRPV1 (5′-iodoresiniferatoxin) and cannabinoid (CB₂; AM630) receptor antagonists blocked the cytotoxic effect of NADA. In subsequent experiments, PBMC from ESKD patients exhibited significantly increased susceptibility to NADA-induced death compared to PBMC from controls. The apparent up-regulation of TRPV1 may be a response to the inflammatory milieu in which PBMC exist in ESKD and may be responsible for the increased susceptibility of these cells to NADA-induced death, providing a possible explanation as to why ESKD patients have reduced lymphocyte counts and impaired immune function. Thus, TRPV1 (and possibly CB₂) antagonists may have potential for the treatment of immune dysfunction in ESKD.     

Programmed cell death and its clinical implications

Cell death is a highly regulated process that is ubiquitous in all eukaryotes. Programmed cell death (PCD) is an integral part of both animal and plant development. Studies on apoptosis, the well characterized form of programmed cell death led to the identification of a central tripartite death switch i.e. apoptosome consisting of Apaf-1, Apaf-2 and Apaf-3. The caspases, a family of cysteine-dependent aspartate directed-proteases, constitute the central executioners of apoptosis. Much of the attention on programmed cell death is focused on caspases, however, cell death can still occur even when the caspase cascade is blocked, revealing the existence of nonapoptotic alternative pathway(s) of cell death. The mitochondrial release of cytochrome C following a PCD inducing stimulus in both plants and animals suggests the evolutionary conservation of death pathways. Dysregulation of apoptosis may be related to the development of several disease states as well as ageing. Excessive apoptosis is associated with neurodegenerative disorders, AIDS etc., whereas deficient apoptosis is associated with cancer, auto-immunity, viral infections etc. Understanding the regulation of programmed cell death would throw light in designing drugs and gene therapies that can target specific molecules in the apoptotic pathway opening the vistas for new therapeutic endeavors in many areas of medicine.     

Programmed cell death and patterning in Drosophila

Selective cell death provides developing tissues with the means to precisely sculpt emerging structures. By imposing patterned cell death across a tissue, boundaries can be created and tightened. As such, programmed cell death is becoming recognized as a major mechanism for patterning of a variety of complex structures. Typically, cell types are initially organized into a fairly loose pattern; selective death then removes cells between pattern elements to create correct structures. In this review, we examine the role of selective cell death across the course of Drosophila development, including the tightening of embryonic segmental boundaries, head maturation, refining adult structures such as the eye and the wing, and the ability of cell death to correct for pattern defects introduced by gene mutation. We also review what is currently known of the relationship between signals at the cell surface that are responsible for tissue patterning and the basal cell death machinery, an issue that remains poorly understood.     

果蝇程序化死亡基因5(PDCD5)同源cDNA的克隆和序列分析

 为了解人类白血病细胞凋亡相关新基因 TFAR1 9(PDCD5,programmed cell death5)在不同种属间的序列同源性 ,利用 EST(expression sequence tag)拼接、RT- PCR、DNA序列测定技术及计算机分析技术 ,首次成功地进行了果蝇 PDCD5同源 c DNA编码区基因克隆和序列分析 .发现果蝇与小鼠及果蝇与人 PDCD5在核苷酸水平上分别有 57.5%和 57.1 %的同源性 ,在氨基酸水平上分别有 46.8%和 46.4%的同源性 .功能区分析发现 ,果蝇 PDCD5c DNA编码 1 33个氨基酸 ,计算机预测可能是一种核蛋白 ,含 5个可能的酪蛋白激酶 (casein kinase )磷酸化位点 ,2个可能的 PKC磷酸化位点 ,与人 PDCD5的功能区类似 .因而果蝇 PDCD5是与人 PDCD5同源的新基因 ,可能都与细胞程序化死亡相关 .