Biomedical subjects

Eiman Aleem

Publications and source records attributed to Eiman Aleem.

11 recordsLinked to original sources

PubMed2026

Amplification-Driven S100A11 Overexpression in Hepatocellular Carcinoma Is Associated with Metabolic Reprogramming, ECM Remodelling, and Immune Evasion: A Pan-Cancer Genomic Study.

BACKGROUND: S100A11, a calcium-binding S100 family protein, is increasingly implicated in carcinogenesis, yet its molecular regulation and clinical relevance across cancers remain unclear. Hepatocellular carcinoma (HCC) carries a dismal prognosis, in part due to a lack of reliable biomarkers for risk stratification of established disease. METHODS: We conducted a pan-cancer analysis of S100A11 genomic alterations across 31 studies (10,767 samples) obtained from TCGA, encompassing copy number alterations, somatic mutations, and DNA methylation. HCC-specific analyses evaluated S100A11 expression, its potential as a diagnostic/prognostic marker, co-expression networks, and pathway enrichment using TCGA-LIHC data, with univariate and multivariate Cox regression to assess survival associations. RESULTS: S100A11 alterations were predominantly driven by copy number amplification, with the highest frequencies in hepatobiliary cancers, lung and breast cancers. Copy number amplification showed a consistent inverse relationship with promoter methylation, indicating amplification-driven transcriptional activation. In HCC, S100A11 was markedly overexpressed compared with normal liver tissue, with strong diagnostic discriminatory capacity. High S100A11 expression was significantly associated with inferior overall survival (log-rank p = 0.032; HR = 1.46, 95% CI 1.03-2.06) and remained an independent predictor of overall survival after adjustment for age, sex, and AJCC pathologic stage (HR = 1.27, 95% CI 1.01-1.60, p = 0.038). Co-expression and pathway analyses demonstrated an association between S100A11 and metabolic reprogramming, extracellular matrix remodelling, and immune dysregulation. CONCLUSIONS: These findings identify S100A11 as a candidate diagnostic and prognostic biomarker in HCC whose overexpression is associated with metabolic reprogramming, ECM remodelling, and immune dysregulation, warranting experimental validation of a mechanistic role.

ECM↗

PubMed2006

PRKAR1A inactivation leads to increased proliferation and decreased apoptosis in human B lymphocytes.

The multiple neoplasia syndrome Carney complex (CNC) is caused by heterozygote mutations in the gene, which codes for the RIalpha regulatory subunit (PRKAR1A) of protein kinase A. Inactivation of PRKAR1A and the additional loss of the normal allele lead to tumors in CNC patients and increased cyclic AMP signaling in their cells, but the oncogenetic mechanisms in affected tissues remain unknown. Previous studies suggested that PRKAR1A down-regulation may lead to increased mitogen-activated protein kinase (MAPK) signaling. Here, we show that, in lymphocytes with PRKAR1A-inactivating mutations, there is increased extracellular signal-regulated kinase (ERK) 1/2 and B-raf phosphorylation and MAPK/ERK kinase 1/2 and c-Myc activation, whereas c-Raf-1 is inhibited. These changes are accompanied by increased cell cycle rates and decreased apoptosis that result in an overall net gain in proliferation and survival. In conclusion, inactivation of PRKAR1A leads to widespread changes in molecular pathways that control cell cycle and apoptosis. This is the first study to show that human cells with partially inactivated RIalpha levels have increased proliferation and survival, suggesting that loss of the normal allele in these cells is not necessary for these changes to occur.

Apoptosis↗

PubMed2006

Dependence of cisplatin-induced cell death in vitro and in vivo on cyclin-dependent kinase 2.

Cisplatin is one of the most effective chemotherapeutics, but its usefulness is limited by its toxicity to normal tissues, including cells of the kidney proximal tubule. The purpose of these studies was to determine the mechanism of cisplatin cytotoxicity. It was shown in vivo that cisplatin administration induces upregulation of the gene for the p21 cyclin-dependent kinase (cdk) inhibitor in kidney cells. This protein is a positive effector on the fate of cisplatin-exposed renal tubule cells in vivo and in vitro; adenoviral transduction of p21 completely protected proximal tubule cells from cisplatin toxicity. Herein is reported that cdk2 inhibitory drugs protect kidney cells in vivo and in vitro, that transduction of kidney cells in vitro with dominant-negative cdk2 also protected, and that cdk2 knockout cells were resistant to cisplatin. The cdk2 knockout cells regained cisplatin sensitivity after transduction with wild-type cdk2. It is concluded that cisplatin cytotoxicity depends on cdk2 activation and that the mechanism of p21 protection is by direct inhibition of cdk2. This demonstrated the involvement of a protein that previously was associated with cell-cycle progression with pathways of apoptosis. It also was demonstrated that this pathway of cisplatin-induced cell death can be interceded in vivo to prevent nephrotoxicity.

Adenine↗

PubMed2006

CDK2 is required by MYC to induce apoptosis.

Depending upon the cellular and physiologic context, the overexpression of the MYC proto-oncogene results in rapid cell growth, proliferation, induction of apoptosis and/or proliferative arrest. What determines the precise consequences upon MYC activation is not clear. We have found that cyclin-dependent kinase 2 (CDK2) is required by MYC to induce apoptosis. MYC-induced apoptosis was suppressed in mouse embryonic fibroblasts (MEF) knocked out for Cdk2 or normal human fibroblasts (NHF) upon expression of the CDK2 inhibitor p27 or treated with RNAi directed at CDK2. Knockout of Cdk2 did not prevent MYC from inducing p53 and Bim. The inhibition of CDK2 did not prevent apoptosis induced by the DNA damaging agent etoposide. Our results surprisingly suggest that CDK2 defines whether MYC induction causes apoptosis.

Animals↗

PubMed2006

IL-7 promotes T cell proliferation through destabilization of p27Kip1.

Interleukin (IL)-7 is required for survival and homeostatic proliferation of T lymphocytes. The survival effect of IL-7 is primarily through regulation of Bcl-2 family members; however, the proliferative mechanism is unclear. It has not been determined whether the IL-7 receptor actually delivers a proliferative signal or whether, by promoting survival, proliferation results from signals other than the IL-7 receptor. We show that in an IL-7-dependent T cell line, cells protected from apoptosis nevertheless underwent cell cycle arrest after IL-7 withdrawal. This arrest was accompanied by up-regulation of the cyclin-dependent kinase inhibitor p27Kip1 through a posttranslational mechanism. Overexpression of p27Kip1 induced G1 arrest in the presence of IL-7, whereas knockdown of p27Kip1 by small interfering RNA promoted S phase entry after IL-7 withdrawal. CD4 or CD8 T cells transferred into IL-7-deficient hosts underwent G1 arrest, whereas 27Kip1-deficient T cells underwent proliferation. We observed that IL-7 withdrawal activated protein kinase C (PKC)theta and that inhibition of PKCtheta with a pharmacological inhibitor completely blocked the rise of p27Kip1 and rescued cells from G1 arrest. The conventional pathway to breakdown of p27Kip1 is mediated by S phase kinase-associated protein 2; however, our evidence suggests that PKCtheta acts via a distinct, unknown pathway inducing G1 arrest after IL-7 withdrawal from T cells. Hence, IL-7 maintains T cell proliferation through a novel pathway of p27Kip1 regulation.

Animals↗

PubMed2006

Mouse models of cell cycle regulators: new paradigms.

In yeast, a single cyclin-dependent kinase (Cdk) is able to regulate diverse cell cycle transitions (S and M phases) by associating with multiple stage-specific cyclins. The evolution of multicellular organisms brought additional layers of cell cycle regulation in the form of numerous Cdks, cyclins and Cdk inhibitors to reflect the higher levels of organismal complexity. Our current knowledge about the mammalian cell cycle emerged from early experiments using human and rodent cell lines, from which we built the current textbook model of cell cycle regulation. In this model, the functions of different cyclin/Cdk complexes were thought to be specific for each cell cycle phase. In the last decade, studies using genetically engineered mice in which cell cycle regulators were targeted revealed many surprises. We discovered the in vivo functions of cell cycle proteins within the context of a living animal and whether they are essential for animal development. In this review, we discuss first the textbook model of cell cycle regulation, followed by a global overview of data obtained from different mouse models. We describe the similarities and differences between the phenotypes of different mouse models including embryonic lethality, sterility, hematopoietic, pancreatic, and placental defects. We also describe the role of key cell cycle regulators in the development of tumors in mice, and the implications of these data for human cancer. Furthermore, animal models in which two or more genes are ablated revealed which cell cycle regulators interact genetically and functionally complement each other. We discuss for example the interaction of cyclin D1 and p27 and the compensation of Cdk2 by Cdc2. We also focus on new functions discovered for certain cell cycle regulators such as the regulation of S phase by Cdc2 and the role of p27 in regulating cell migration. Finally, we conclude the chapter by discussing the limitations of animal models and to what extent can the recent findings be reconciled with the past work to come up with a new model for cell cycle regulation with high levels of redundancy among the molecular players.

Animals↗

PubMed2005

Cell cycle sibling rivalry: Cdc2 vs. Cdk2.

It has been long believed that the cyclin-dependent kinase 2 (Cdk2) binds to cyclin E or cyclin A and exclusively promotes the G1/S phase transition and that Cdc2/cyclin B complexes play a major role in mitosis. We now provide evidence that Cdc2 binds to cyclin E (in addition to cyclin A and B) and is able to promote the G1/S transition. This new concept indicates that both Cdk2 and/or Cdc2 can drive cells through G1/S phase in parallel. In this review we discuss the classic cell cycle model and how results from knockout mice provide new evidence that refute this model. We focus on the roles of Cdc2 and p27 in regulating the mammalian cell cycle and propose a new model for cell cycle regulation that accommodates these novel findings.

Animals↗

PubMed2005

Cdc2-cyclin E complexes regulate the G1/S phase transition.

The cyclin-dependent kinase inhibitor p27(Kip1) is known as a negative regulator of cell-cycle progression and as a tumour suppressor. Cdk2 is the main target of p27 (refs 2, 3) and therefore we hypothesized that loss of Cdk2 activity should modify the p27(-/-) mouse phenotype. Here, we show that although p27(-/-) Cdk2(-/-) mice developed ovary tumours and tumours in the anterior lobe of the pituitary, we failed to detect any functional complementation in p27(-/-) Cdk2(-/-) double-knockout mice, indicating a parallel pathway regulated by p27. We observed elevated levels of S phase and mitosis in tissues of p27(-/-) Cdk2(-/-) mice concomitantly with elevated Cdc2 activity in p27(-/-) Cdk2(-/-) extracts. p27 binds to Cdc2, cyclin B1, cyclin A2, or suc1 complexes in wild-type and Cdk2(-/-) extracts. In addition, cyclin E binds to and activates Cdc2. Our in vivo results provide strong evidence that Cdc2 may compensate the loss of Cdk2 function.

2-Aminopurine↗

PubMed2004

Cdk2 as a master of S phase entry: fact or fake?

It has long been believed that Cdk2 and its activator cyclin E play essential roles in the progression of the mitotic cell cycle. However, recent studies using knockout mouse models revealed that neither Cdk2 nor cyclin E are essential in vivo. The purpose of this Perspective is to compare both Cdk2 and cyclin E knockout mice models and to discuss potential mechanisms driving the cell cycle in the absence of Cdk2 or cyclin E. Particular emphasis is placed on possible non-catalytic roles of cyclin E, the expression and activity of the second cyclin binding partner of Cdk2, cyclin A, as well as on the expression and degradation of the Cdk2 inhibitor p27Kip1 in the absence of Cdk2.

Animals↗

PubMed2004

Protein phosphatase inhibitor-1 mRNA expression correlates with neoplastic transformation of epithelial liver cells and progression of hepatocellular carcinomas.

Protein phosphatase inhibitor-1 plays an important role in the regulation of glycogen metabolism through inhibition of protein phosphatase-1 activity, and it has been implicated in the regulation of cell growth. Using real-time quantitative RT-PCR, we studied the mRNA expression of inhibitor-1 in hepatocellular carcinomas induced in rats by oral administration of N-nitrosomorpholine, and in a non-tumorigenic liver cell line (C1I), that stores glycogen in excess during early passages. In late passages, glycogen is gradually lost concomitant with cell transformation. Our in vitro model included a tumorigenic subline of C1I cells that was obtained by chemically-induced neoplastic transformation using N-methyl-N'-nitro-N-nitrosoguanidine (C1Ict), and does not store glycogen, as well as Morris hepatoma 3924A (MH3924A) cells. We found that in hepatocellular carcinomas, in the late glycogen-poor passages (C1I(late)), and in the tumorigenic subline (C1Ict) of C1I cells, and in MH3924A cells the mRNA expression of inhibitor-1 is significantly increased. This increase in expression varied from 15 to 290-fold of that observed in normal liver. In contrast, in the early glycogen-storing passage of C1I cells (C1I(early)) the level of inhibitor-1 mRNA was found to be slightly less than that of normal liver. Inhibitor-1 mRNA levels correlated with the degree of differentiation of HCCs. These results indicate that the expression of inhibitor-1 mRNA is tightly linked to tumor progression and to the process of liver cell transformation in vitro and is inversely correlated with the glycogen content of the cell.

Administration, Oral↗

PubMed2003

Cdk2 knockout mice are viable.

BACKGROUND: Cyclin-dependent kinases (Cdks) and their cyclin regulatory subunits control cell growth and division. Cdk2/cyclin E complexes are thought to be required because they phosphorylate the retinoblastoma protein and drive cells through the G1/S transition into the S phase of the cell cycle. In addition, Cdk2 associates with cyclin A, which itself is essential for cell proliferation during early embryonic development. RESULTS: In order to study the functions of Cdk2 in vivo, we generated Cdk2 knockout mice. Surprisingly, these mice are viable, and therefore Cdk2 is not an essential gene in the mouse. However, Cdk2 is required for germ cell development; both male and female Cdk2(-/-) mice are sterile. Immunoprecipitates of cyclin E1 complexes from Cdk2(-/-) spleen extracts displayed no activity toward histone H1. Cyclin A2 complexes were active in primary mouse embryonic fibroblasts (MEFs), embryo extracts and in spleen extracts from young animals. In contrast, there was little cyclin A2 kinase activity in immortalized MEFs and spleen extracts from adult animals. Cdk2(-/-) MEFs proliferate but enter delayed into S phase. Ectopic expression of Cdk2 in Cdk2(-/-) MEFs rescued the delayed entry into S phase. CONCLUSIONS: Although Cdk2 is not an essential gene in the mouse, it is required for germ cell development and meiosis. Loss of Cdk2 affects the timing of S phase, suggesting that Cdk2 is involved in regulating progression through the mitotic cell cycle.

Animals↗