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.     

Tumour suppressive function and modulation of programmed cell death 4 (PDCD4) in ovarian cancer

Background

Programmed cell death 4 (PDCD4), originally identified as the neoplastic transformation inhibitor, was attenuated in various cancer types. Our previous study demonstrated a continuous down-regulation of PDCD4 expression in the sequence of normal-borderline-malignant ovarian tissue samples and a significant correlation of PDCD4 expression with disease-free survival. The objective of the current study was to further investigate the function and modulation of PDCD4 in ovarian cancer cells.

Principal Findings

We demonstrated that ectopic PDCD4 expression significantly inhibited cell proliferation by inducing cell cycle arrest at G₁ stage and up-regulation of cell cycle inhibitors of p27 and p21. Cell migration and invasion were also inhibited by PDCD4. PDCD4 over-expressing cells exhibited elevated phosphatase and tensin homolog (PTEN) and inhibited protein kinase B (p-Akt). In addition, the expression of PDCD4 was up-regulated and it was exported to the cytoplasm upon serum withdrawal treatment, but it was rapidly depleted via proteasomal degradation upon serum re-administration. Treatment of a phosphoinositide 3-kinase (PI3K) inhibitor prevented the degradation of PDCD4, indicating the involvement of PI3K-Akt pathway in the modulation of PDCD4.

Conclusion

PDCD4 may play a critical function in arresting cell cycle progression at key checkpoint, thus inhibiting cell proliferation, as well as suppressing tumour metastasis. The PI3K-Akt pathway was implied to be involved in the regulation of PDCD4 degradation in ovarian cancer cells. In response to the stress condition, endogenous PDCD4 was able to shuttle between cell compartments to perform its diverted functions.     

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.     

Regulatory effects of programmed cell death 4 (PDCD4) protein in interferon (IFN)-stimulated gene expression and generation of type I IFN responses

The precise mechanisms by which the activation of interferon (IFN) receptors (IFNRs) ultimately controls mRNA translation of specific target genes to induce IFN-dependent biological responses remain ill defined. We provide evidence that IFN-α induces phosphorylation of programmed cell death 4 (PDCD4) protein on Ser67. This IFN-α-dependent phosphorylation is mediated by either the p70 S6 kinase (S6K) or the p90 ribosomal protein S6K (RSK) in a cell-type-specific manner. IFN-dependent phosphorylation of PDCD4 results in downregulation of PDCD4 protein levels as the phosphorylated form of PDCD4 interacts with the ubiquitin ligase β-TRCP (β-transducin repeat-containing protein) and undergoes degradation. This process facilitates IFN-induced eukaryotic translation initiation factor 4A (eIF4A) activity and binding to translation initiation factor eIF4G to promote mRNA translation. Our data establish that PDCD4 degradation ultimately facilitates expression of several ISG protein products that play important roles in the generation of IFN responses, including IFN-stimulated gene 15 (ISG15), p21(WAF1/CIP1), and Schlafen 5 (SLFN5). Moreover, engagement of the RSK/PDCD4 pathway by the type I IFNR is required for the suppressive effects of IFN-α on normal CD34(+) hematopoietic precursors and for antileukemic effects in vitro. Altogether, these findings provide evidence for a unique function of PDCD4 in the type I IFN system and indicate a key regulatory role for this protein in mRNA translation of ISGs and control of IFN responses.     

miR-21 modulates chemosensitivity of tongue squamous cell carcinoma cells to cisplatin by targeting PDCD4

Chemoresistance is a challenge for clinician in management of tongue cancer. Therefore, it is necessary to explore alternative therapeutic methods to overcome drug resistance. miRNAs are endogenous ?22nt RNAs that play important regulatory roles by targeting mRNAs. miR-21, an essential oncogenic molecule, is associated with chemosensitivity of several human cancer cells to anticancer agents. In this study, we investigated the effects and molecular mechanisms of miR-21 in chemosensitivity of tongue squamous cell carcinoma cells (TSCC) to cisplatin. miR-21 expression was detected in tongue cancer tissue using RT-PCR and PDCD4 protein expression was measured using immunohistochemistry. miR-21 and(or) PDCD4 depleted cell lines were generated using miR-21 inhibitor and(or) siRNA. The viabilities of treated cells were analyzed using MTT assay. RT-PCR was used to detect miR-21 expression and immunoblotting was used to detect protein levels. Cell cycle and apoptosis were analyzed using propidium iodide (PI) staining and Annexin V/PI staining, respectively. The expression of miR-21 in tumorous tissue was significantly higher compared with adjacent normal tissue and loss of PDCD4 expression was observed in TSCCs. Transfection of miR-21 inhibitor induced sensitivity of TSCC cells (Tca8113 and CAL-27) to cisplatin. TSCC cells transfected with PDCD4 siRNA became more resistant to cisplatin therapy. We found an increase PDCD4 protein level following the transfection of miR-21 inhibitor using Western blot analysis. In addition, the enhanced growth-inhibitory effect by miR-21 inhibitor was weakened after the addition of PDCD4 siRNA. Suppression of miR-21 or PDCD4 could significantly promote or reduce cisplatin-induced apoptosis, respectively. Our data suggest that miR-21 could modulate chemosensitivity of TSCC cells to cisplatin by targeting PDCD4, and miR-21 may serve as a potential target for TSCC therapy.     

Suppression of programmed cell death 4 (PDCD4) protein expression by BCR-ABL-regulated engagement of the mTOR/p70 S6 kinase pathway

There is accumulating evidence that mammalian target of rapamycin (mTOR)-activated pathways play important roles in cell growth and survival of BCR-ABL-transformed cells. We have previously shown that the mTOR/p70 S6 kinase (p70 S6K) pathway is constitutively activated in BCR-ABL transformed cells and that inhibition of BCR-ABL kinase activity by imatinib mesylate abrogates such activation. We now provide evidence for the existence of a novel regulatory mechanism by which BCR-ABL promotes cell proliferation, involving p70 S6K-mediated suppression of expression of programmed cell death 4 (PDCD4), a tumor suppressor protein that acts as an inhibitor of cap-dependent translation by blocking the translation initiation factor eIF4A. Our data also establish that second generation BCR-ABL kinase inhibitors block activation of p70 S6K and downstream engagement of the S6 ribosomal protein in BCR-ABL transformed cells. Moreover, PDCD4 protein expression is up-regulated by inhibition of the BCR-ABL kinase in K562 cells and BaF3/BCR-ABL transfectants, suggesting a mechanism for the generation of the proapoptotic effects of such inhibitors. Knockdown of PDCD4 expression results in reversal of the suppressive effects of nilotinib and imatinib mesylate on leukemic progenitor colony formation, suggesting an important role for this protein in the generation of antileukemic responses. Altogether, our studies identify a novel mechanism by which BCR-ABL may promote leukemic cell growth, involving sequential engagement of the mTOR/p70 S6K pathway and downstream suppression of PDCD4 expression.     

Genetically programmed cell death (apoptosis)

Extensively and successfully studied problems of programmed cell death are considered. Recent evidence on apoptosis genes is presented, including the bcl-2 family and other genes with similar functions. A scheme of pathways of the main apoptosis mechanism is constructed. Examples of associations of apoptosis and diseases are presented in a special section.     

Programmed cell death 1 (PDCD1) gene haplotypes and susceptibility of patients to basal cell carcinoma

Molecular Biology Reports - Programmed death-1 (PD-1), as an immunoinhibitory receptor encoded by programmed cell death-1 (PDCD1) gene, has a pivotal role in tolerance to self-antigens. Mutations...     

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.     

动物细胞培养过程中的细胞自然凋亡

细胞培养过程中的细胞自然凋亡是细胞受环境压力的影响而发生的现象。随着细胞自然凋亡的分子生物学和生物化学研究的深入,对以动物细胞产品生产为目的的细胞培养产业将产生极有价值的影响。采用DNA重组技术把预防细胞自然凋亡的基因导入细胞和在培基中加入具有抗细胞自然凋亡的化合物等手段已用于预防或减缓细胞培养过程中的细胞自然凋亡。这些技术将大大延长细胞达到饱和密度后的培养时间,从而使细胞培养系统的生产效率得以显著提高。     

IL-4 enhances programmed cell death (apoptosis) in stimulated human monocytes.

Because IL-4 down-regulates several proinflammatory functions associated with human monocytes/macrophages, we explored the possibility that IL-4 also decreases monocyte survival. IL-4 caused a concentration-dependent decrease in viability of IL-1 or LPS stimulated, but not unstimulated, monocytes. Nonviable cells demonstrated classic features of programmed cell death or apoptosis, in that they were condensed and contained oligonucleosome-sized (200 bp) DNA fragments. When compared with several other cytokines commonly associated with inflammatory lesions, IL-4 was uniquely effective in enhancing cell death. We found that IL-4 enhanced death more quickly in IL-1-stimulated cells than in LPS-stimulated cells, that stimulated monocytes did not become resistant to the effects of IL-4 during culture, and that the effects of IL-4 on viability were antagonized by IFN-gamma. Enhanced cell death was stimulus-specific in that monocyte viability maintained by certain activating agents, such as Con A or CSF, was unaffected by IL-4. These findings represent the first evidence of cytokine-enhanced programmed cell death in monocytes and suggest that the antiinflammatory effects of IL-4 are mediated in part by reducing survival of stimulated monocytes in chronic lesions.     

Genetic control of programmed cell death (apoptosis) in Drosophila

Programmed cell death, or apoptosis, is a highly conserved cellular process that has been intensively investigated in nematodes, flies, and mammals. The genetic conservation, the low redundancy, the feasibility for high-throughput genetic screens and the identification of temporally and spatially regulated apoptotic responses make Drosophila melanogaster a great model for the study of apoptosis. Here, we review the key players of the cell death pathway in Drosophila and discuss their roles in apoptotic and non-apoptotic processes.     

Induction of programmed cell death (apoptosis) in mature lymphocytes

The apoptosis of human peripheral blood lymphocytes was analyzed by the breakdown of DNA into oligonucleosome-sized fragments. The mature lymphocytes were rendered sensitive to apoptosis by either the omission of fetal bovine serum in the culture medium or the addition of polymyxin B. In the first case it was counteracted by phorbol myristate acetate. The possible involvement of protein kinase C in cell survival is pointed out.     

Structure-function correlation of human programmed cell death 5 protein

Human programmed cell death 5 (PDCD5) is a translocatory protein playing an important role in the apoptotic process of cells. Although there are accumulated data about PDCD5 function, the correlation of the structure with the function of PDCD5 has not been investigated. Here, we report the studies of structure-function relationship of PDCD5 by multidimensional NMR methods and by FACScan flow cytometer and fluorescence microscope. The 3D structure of intact PDCD5 and the internal motions of PDCD5 have been determined. PDCD5 has a compact core structure of low flexibility with two mobile α-helices at N-terminal region and a flexible unstructured C-terminal region. The flow cytometry and internalization measurements of different PDCD5 fragments indicate that the charged residues are crucial for the ability of apoptosis-promoting and cell translocation of the protein. Combined analyses reveal a fact that the regions that seem to be most involved in the function also are more flexible in PDCD5.     

p21-activated protein kinase gamma-PAK suppresses programmed cell death of BALB3T3 fibroblasts

In response to stress stimulants, cells activate opposing signaling pathways for cell survival and programmed cell death. p21-activated protein kinase gamma-PAK is involved in both cell survival and cell death pathways. Many stress stimulants activate gamma-PAK as a full-length enzyme and as a proteolytic fragment. Caspase-mediated proteolytic activation parallels cell death and appears to be a pro-apoptotic factor in stress-induced cell death. Here, we show that activation of full-length gamma-PAK promotes cell survival and suppresses stress-induced cell death. Expression of constitutively active gamma-PAK-T402E, which mimics activated full-length gamma-PAK, stimulates cell survival of BALB3T3 fibroblasts in response to tumor necrosis factor alpha, growth factor withdrawal, and UVC light. This stimulation of cell survival is mainly due to protection of cells from cell death rather than by stimulation of proliferation. Expression of gamma-PAK-T402E increases phosphorylation of the pro-apoptotic Bcl-2 family protein Bad and protects from cell death induced by ectopic expression of Bad. In response to tumor necrosis factor alpha, expression of gamma-PAK-T402E increases the early but reduces the late activation of ERK, JNK, and p38. Our results indicate that the ubiquitous gamma-PAK may have a crucial function in cell survival by regulating the pro-apoptotic activity of Bad and the stress-induced activation of ERK, JNK, and p38 pathways.     

miR-93 enhances hepatocellular carcinoma invasion and metastasis by EMT via targeting PDCD4

Objectives

To clarify the potential biological function of miR-93 and its related molecular mechanism underlying metastasis in human hepatocellular carcinoma (HCC).

Results

miR-93 was significantly up-regulated in HCC tissues and was associated with poor 5-year overall survival in HCC patients. Transwell assays showed that over-expression of miR-93 increased HCC cell migration and invasion in vitro. Programmed cell death 4 (PDCD4) was a target gene of miR-93 and miR-93 could down-regulate the expression of PDCD4 by directly targeting its 3′-UTR. The re-expression of PDCD4 could attenuate the HCC cell invasion and migration induced by miR-93, while the knockdown of PDCD4 would promote HCC cell migration and invasion via the epithelial-mesenchymal transition (EMT) pathway.

Conclusions

miR-93 provides new insight into the molecular mechanisms of pathogenesis and progression in HCC and offer a potential therapeutic target for the treatment of HCC patients.

     

Chlamydia and programmed cell death

Discordant views regarding host cell death induction by Chlamydia are likely owing to the different methods used for evaluation of apoptosis. Apoptotic and non-apoptotic death owing to both caspase-dependent and -independent activation of the Bax protein occur late in the productive growth cycle. Evidence also suggests that Chlamydia inhibits apoptosis during productive growth as part of its intracellular survival strategy. This is in part owing to proteolytic degradation of the BH3-only family of pro-apoptotic proteins in the mitochondrial pathway. Chlamydia also inhibits apoptosis during persistent growth or in phagocytes, but induces apoptosis in T cells, which suggests that apoptosis has an immunomodulatory role in chlamydial infections. The contribution of apoptosis in disease pathogenesis remains a focus for future research.