TRIM44 is indispensable for glioma cell proliferation and cell cycle progression through AKT/p21/p27 signaling pathway

Journal of Neuro-Oncology - Incidental discovery accounts for 30% of newly-diagnosed intracranial meningiomas. There is no consensus on their optimal management. This review aimed to evaluate the...     

p63alpha and DeltaNp63alpha can induce cell cycle arrest and apoptosis and differentially regulate p53 target genes.

The p53 tumor suppressor protein plays a critical role in the regulation of the cell cycle and apoptosis. The importance of p53's functions is underscored by the high incidence of p53 mutations in human cancers. Recently, two p53-related proteins, p73 and p63, were identified as members of the p53 gene family. Multiple isoforms of p73 have been found, including DeltaN variants in which the N-termini are truncated. p63 is expressed as three major forms, p63alpha, p63beta and p63gamma, each of which differ in their C-termini. All three forms can be alternatively transcribed from a cryptic promoter located within intron 3, producing DeltaNp63alpha, DeltaNp63beta and DeltaNp63gamma. The high degree of similarity of p73 and p63 to evolutionarily conserved regions of p53 suggests that these proteins play an important and potentially redundant role in regulating cell cycle arrest and apoptosis. Here we describe the characterization of cell lines generated to inducibly express p63alpha and DeltaNp63alpha. We have found that p63alpha and DeltaNp63alpha can differentially regulate endogenous p53 target genes and induce cell cycle arrest and apoptosis. Deletion of the N-terminal 26 amino acids of DeltaNp63alpha abolished its ability to transactivate p53 target genes and induce cell cycle arrest and apoptosis. This indicates that a putative transactivation domain exists within the N-terminus of the DeltaN variants of p63. Furthermore, the differential regulation of p53 target genes by p63alpha and DeltaNp63alpha suggests that p63 and p53 utilize both similar and different signaling pathways to execute their cellular functions.     

Apigenin induces cell cycle arrest and p21/WAF1 expression in a p53-independent pathway

Apigenin, a common dietary flavonoid, has been shown to induce cell growth-inhibition and cell cycle arrest in many cancer cell lines. One important effect of apigenin is to increase the stability of the tumor suppressor p53 in normal cells. Therefore, apigenin is expected to play a large role in cancer prevention by modifying the effects of p53 protein. However, the mechanisms of apigenin's effects on p53-mutant cancer cells have not been revealed yet. We assessed the influence of apigenin on cell growth and the cell cycle in p53-mutant cell lines. Treatment with apigenin resulted in growth-inhibition and G2/M phase arrest in two p53-mutant cancer cell lines, HT-29 and MG63. These effects were associated with a marked increase in the protein expression of p21/WAF1. We have shown that p21/WAF1 mRNA expression was also markedly increased by treatment with apigenin in a dose- and time-dependent manner. However, we could not detect p21/WAF1 promoter activity following treatment with apigenin. Similarly, promoter activity from pG13-Luc, a p53-responsive promoter plasmid, was not activated by treatment with apigenin with or without p53 protein expression. These results suggest that there is a p53-independent pathway for apigenin in p53-mutant cell lines, which induces p21/WAF1 expression and growth-inhibition. Apigenin may be a useful chemopreventive agent not only in wild-type p53 status, but also in cancer with mutant p53.     

CDO1通过PI3K/AKT信号通路调控胃癌细胞增殖及细胞周期

目的:探讨半胱氨酸双加氧酶1(CDO1)对胃癌细胞增殖、细胞周期的调控机制。方法:用脂质体法将si-NC组（转染si-NC）、si-CDO1组（转染si-CDO1）、pcDNA组（转染pcDNA）、pcDNA-CDO1组（转染pcDNA-CDO1）、pcDNA-CDO1+DMSO组（转染pcDNA-CDO1并用DMSO处理）、pcDNA-CDO1+IGF-1组（转染pcDNA-CDO1并用IGF-1处理）转染至AKG细胞。用实时荧光定量逆转录聚合酶链反应（qRT-PCR）、免疫印迹（Western blot）、细胞计数试剂盒（CCK-8）、流式细胞术检测细胞CDO1、PI3K、Akt、p-Akt蛋白的表达、细胞增殖、细胞周期。结果:与人胃黏膜上皮细胞GES-1相比，胃腺癌细胞AKG中CDO1的表达明显降低（P<0.05）；与si-NC组相比，si-CDO1组AKG细胞的增殖明显上调，细胞发生明显的S期、G2/M期阻滞，过表达CDO1则具有相反的作用。重要的是，敲减CDO1可上调PI3K/AKT信号通路关键基因PI3K、p-Akt的表达，而过表达CDO1具有相反的作用。激活PI3K/AKT信号通路后，过表达CDO1对胃癌细胞的增殖、细胞周期的调控作用可被部分逆转。结论:CDO1可抑制胃癌细胞的增殖，调控细胞周期，其机制与抑制PI3K/AKT信号通路的活性有关，将为胃癌的治疗提供参考。     

胃癌细胞周期不同时相MTS1/p16、p21、p53的表达

进一步明明确不同周期时相肿瘤细胞Ｐ１６基因的表达水平及在细胞周期调控中的作用。方法改进并建立了一个高同步率,高收获率的细胞周期同步化的方法,通过此方法把细胞同步在不同的时期,对ＲＮＡ及蛋白的表达进行研究,确定地不同同量丰中Ｐ１６的表达有何变化,同时分析其它几个重要的抑癌基因如Ｐ５３、Ｐ２１,研究它们在细胞周期中的表达以及与Ｐ１６基因相经关系。结果确定在不同周期时相的胃癌细胞系ＭＧｃ８０－３Ｇ     

The rTS signaling pathway as a target for drug development

The rTS gene was discovered because it codes for a complementary (antisense) RNA to the messenger RNA for thymidylate synthase (TS). It was later shown that rTS also encodes 2 proteins, rTSa and rTSb. Recently, it has become apparent that rTSb overexpression can cause the downregulation of TS protein in a colon cancer cell line through the production of > or = 1 previously unknown signaling molecules. This observation signified the presence of a previously unidentified signaling pathway. The existence of a signaling pathway that can regulate TS protein levels and the widespread expression of the rTSb protein suggests that a new target for drug development may be on the horizon. This review describes the relationship between the rTS and TS genes and the known and potential effects of rTS RNAs and rTS proteins. We also present the structure of an identified TS downregulatory compound that may serve as a lead compound for development.     

Glabridin arrests cell cycle and inhibits proliferation of hepatocellular carcinoma by suppressing braf/MEK signaling pathway

Tumor Biology - Glabridin, an isoflavone isolated from licorice, owns a variety of pharmacological effects. Several reports have demonstrated that glabridin could regulate multiple cellular...     

EEF1E1 promotes glioma proliferation by regulating cell cycle through PTEN/AKT signaling pathway

The cell cycle, a pivotal regulator of cell proliferation, can be significantly influenced by the phosphatase and tensin homolog (PTEN)/AKT signaling pathway's modulation of cyclin-related proteins. In our study, we discovered the crucial role of EEF1E1 in this process, as it appears to downregulate PTEN expression. Furthermore, our findings affirmed that EEF1E1 modulates downstream cell cycle-related proteins by suppressing the PTEN/AKT pathway. Cell cycle assay results revealed that EEF1E1 downregulation stunted the advancement of glioma cells in both the G1 and S phases. A suite of assays—Cell Counting Kit-8, colony formation, and ethyl-2’-deoxyuridine—substantiated that the EEF1E1 downregulation markedly curtailed glioma proliferation. We further validated this phenomenon through animal studies and coculture experiments on brain slices. Our comprehensive investigation indicates that EEF1E1 knockdown can effectively inhibit the glioma cell proliferation by regulating the cell cycle via the PTEN/AKT signaling pathway. Consequently, EEF1E1 emerges as a potential therapeutic target for glioma treatment, signifying critical clinical implications.     

The cAMP signaling pathway as a therapeutic target in lymphoid malignancies

Certain subsets of lymphoid cells, such as thymocytes or peripheral B cells, undergo apoptosis after treatment with agents which elevate intracellular 3',5' cyclic adenosine monophosphate (cAMP). Investigators have also noted induction of apoptosis of chronic lymphocytic leukemia (CLL) cells following treatment with methylxanthines, a phenomenon that may, at least in part, be due to the activity of these drugs as non-specific phosphodiesterase (PDE) inhibitors. We discuss three general strategies for altering cAMP-mediated signal transduction in lymphoid cells. After a review of what is known about the expression and regulation of PDE families in human lymphoid cells, we focus on the use of isoform-specific PDE inhibitors as potential therapeutic agents in CLL. Our work has suggested that despite the presence of PDE1, PDE3B, PDE4 and PDE7 enzymes in CLL, inhibition of PDE4 results in uniquely potent induction of apoptosis in CLL cells. This effect is relatively specific as comparable treatment of human peripheral blood T cells does not induce apoptosis. Clinical trials utilizing PDE4 inhibitors are indicated in the therapy of CLL patients resistant to standard therapy.     

Deleted in liver cancer 1 controls cell migration through a Dia1-dependent signaling pathway

Deleted in liver cancer (DLC) 1 and 2 are Rho GTPase-activating proteins that are frequently down-regulated in various types of cancer. Ectopic expression in carcinoma cell lines lacking these proteins has been shown to inhibit cell migration and invasion. However, whether the loss of DLC1 or DLC2 is the cause of aberrant Rho signaling in transformed cells has not been investigated. Here, we have down-regulated DLC1 and DLC2 expression in breast cancer cells using a RNA interference approach. Silencing of DLC1 led to the stabilization of stress fibers and focal adhesions and enhanced cell motility in wound-healing as well as chemotactic Transwell assays. We provide evidence that enhanced migration of cells lacking DLC1 is dependent on the Rho effector protein Dia1 but does not require the activity of Rho kinase. By contrast, DLC2 knockdown failed to affect the migratory behavior of cells, suggesting that the two proteins have distinct functions. This is most likely due to their differential subcellular localizations, with DLC1 found in focal adhesions and DLC2 being mainly cytosolic. Collectively, our data show that DLC1 is critically involved in the control of Rho signaling and actin cytoskeleton remodeling and that its cellular loss is sufficient for the acquisition of a more migratory phenotype of breast cancer cells.     

The Akt signaling pathway: An emerging therapeutic target in malignant melanoma

Studies using cultured melanoma cells and patient tumor biopsies have demonstrated deregulated PI3 kinase-Akt3 pathway activity in ∼70% of melanomas. Furthermore, targeting Akt3 and downstream PRAS40 has been shown to inhibit melanoma tumor development in mice. Although these preclinical studies and several other reports using small interfering RNAs and pharmacological agents targeting key members of this pathway have been shown to retard melanoma development, analysis of early Phase I and Phase II clinical trials using pharmacological agents to target this pathway demonstrate the need for (1) selection of patients whose tumors have PI3 kinase-Akt pathway deregulation, (2) further optimization of therapeutic agents for increased potency and reduced toxicity, (3) the identification of additional targets in the same pathway or in other signaling cascades that synergistically inhibit the growth and progression of melanoma, and (4) better methods for targeted delivery of pharmaceutical agents inhibiting this pathway. In this review we discuss key potential targets in PI3K-Akt3 signaling, the status of pharmacological agents targeting these proteins, drugs under clinical development, and strategies to improve the efficacy of therapeutic agents targeting this pathway.     

Human p14(ARF)-mediated cell cycle arrest strictly depends on intact p53 signaling pathways

The tumor suppressor ARF is transcribed from the INK4a/ARF locus in partly overlapping reading frames with the CDK inhibitor p16(Ink4a). ARF is able to antagonize the MDM2-mediated ubiquitination and degradation of p53, leading to either cell cycle arrest or apoptosis, depending on the cellular context. However, recent data point to additional p53-independent functions of mouse p19(ARF). Little is known about the dependency of human p14(ARF) function on p53 and its downstream genes. Therefore, we analysed the mechanism of p14(ARF)-induced cell cycle arrest in several human cell types. Wild-type HCT116 colon carcinoma cells (p53(+/+)p21(CIP1+/+) 14-3-3sigma(+/+)), but not p53(-/-) counterparts, underwent G(1) and G(2) cell cycle arrest following infection with a p14(ARF)-adenovirus. In p21(CIP1-/-) cells, p14(ARF) did not induce G(1) or G(2) arrest, while 14-3-3sigma(-/-) counterparts were mainly arrested in G(1), pointing to essential roles of p21(CIP1) in G(1) and G(2) arrest and cooperative roles of p21 and 14-3-3sigma in ARF-mediated G(2) arrest. Our data demonstrate a strict p53 and p21(CIP1) dependency of p14(ARF)-induced cell cycle arrest in human cells.     

Adriamycin induced G2/M cell cycle arrest in transitional cell cancer cells with wt p53 and p21(WAF1/CIP1) genes

Adriamycin (ADM), widely used for systemic and local treatment of bladder tumors, triggers apoptosis in bladder cancer cells. Here we investigated the effect of ADM on cell cycle progression and expression of cell cycle regulating proteins in bladder cancer cell lines with various p53 and p21(WAF1/CIP1) status. Flowcytometric analysis was used to estimate the cell cycle distribution of T24, HT-1376, RT4, and SCaBER bladder cancer cell lines. Cell cycle regulating proteins were analyzed by Immunoblot. Treatment of RT4 cells, bearing wild type p53 and p21(WAF1/CIP1), with ADM induced expression of both proteins and cell cycle arrest, not in G1, as was anticipated, but in the G2 phase. Simultaneously, Retinoblastoma (Rb) protein expression was decreased. Expression of PCNA, which is a target gene of E2F, was not changed. The results suggest that even if the tumor cells bear wild type (wt) p53 and wt p21(WAF1/CIP1) and both proteins accumulate due to genotoxic stimuli, the cell cycle arrest might happen not in the G1 but in the G2 phase.     

雷帕霉素对食管鳞癌细胞系EC9706的mTOR/p70S6K信号通路的影响

目的：观察雷帕霉素（rapamycin，rapa）对食管鳞癌细胞系EC9706的mTOR／p70S6K信号通路的影响。方法：采用免疫细胞化学证实mTOR／p70S6K信号通路的存在，然后通过DNALadder、RT—PCR、Westernblot及流式细胞术分别从DNA、RNA、蛋白及细胞水平研究rapa对细胞凋亡和信号通路的影响。结果：免疫细胞化学结果显示，在细胞核及细胞质中mTOR均呈阳性；rapa处理后有明显DNALadder产生，且mTOR的mRNA水平及蛋白水平下调。但是，mTOR下游的直接靶点p70S6K的mRNA水平及蛋白水平则升高，二者的变化程度均与rapa剂量的相关；流式细胞术检测结果表明，rapa可使细胞停滞于G1期。结论：食管鳞癌细胞系EC9706中存在mTOR／p70S6K信号通路并且处于激活状态，rapa能明显促进细胞凋亡并抑制该通路激活，从而间接抑制翻译的进行。