Role of p27Kip1 as a transcriptional regulator

Mechanism of KLF2 in young mice with pneumonia induced by Streptococcus pneumoniae

BACKGROUND

Streptococcus pneumoniae (Spn) is a major causative agent of pneumonia, which can disseminate to the bloodstream and brain. Pneumonia remains a leading cause of death among children aged 1-59 months worldwide. This study aims to investigate the role of Kruppel-like factor 2 (KLF2) in lung injury caused by Spn in young mice.

METHODS

Young mice were infected with Spn to induce pneumonia, and the bacterial load in the bronchoalveolar lavage fluid was quantified. KLF2 expression in lung tissues was analyzed using real-time quantitative polymerase chain reaction and Western blotting assays. Following KLF2 overexpression, lung tissues were assessed for lung wet-to-dry weight ratio and Myeloperoxidase activity. The effects of KLF2 on lung injury and inflammation were evaluated through hematoxylin and eosin staining and enzyme-linked immunosorbent assay. Chromatin immunoprecipitation and dual-luciferase assay were conducted to examine the binding of KLF2 to the promoter of microRNA (miR)-222-3p and cyclin-dependent kinase inhibitor 1B (CDKN1B), as well as the binding of miR-222-3p to CDKN1B. Levels of miR-222-3p and CDKN1B in lung tissues were also determined.

RESULTS

In young mice with pneumonia, KLF2 and CDKN1B were downregulated, while miR-222-3p was upregulated in lung tissues. Overexpression of KLF2 reduced lung injury and inflammation, evidenced by decreased bacterial load, reduced lung injury, and lower levels of proinflammatory factors. Co-transfection of miR-222-3p-WT and oe-KLF2 significantly reduced luciferase activity, suggesting that KLF2 binds to the promoter of miR-222-3p and suppresses its expression. Transfection of CDKN1B-WT with miR-222-3p mimics significantly reduced luciferase activity, indicating that miR-222-3p binds to CDKN1B and downregulates its expression. Overexpression of miR-222-3p or downregulation of CDKN1B increased bacterial load in BALF, lung wet/dry weight ratio, MPO activity, and inflammation, thereby reversing the protective effect of KLF2 overexpression on lung injury in young mice with pneumonia.

CONCLUSIONS

KLF2 alleviates lung injury in young mice with Spn-induced pneumonia by transcriptional regulation of the miR-222-3p/CDKN1B axis.

Emerging roles of cytosolic phosphoenolpyruvate kinase 1 (PCK1) in cancer

Although it was traditionally believed that gluconeogenesis enzymes were absent from cancers that did not originate in gluconeogenic organs, numerous investigations have shown that they are functionally expressed in a variety of tumors as mediators of shortened forms of Gluconeogenesis. One of the isomers of PEPCK, the first-rate limiting enzyme in gluconeogenesis, is PCK 1, which catalyzes the conversion of oxaloacetate (OAA) and GTP into PEP, CO2, and GDP. It is also known as PEPCK-C or PCK1, and it is cytosolic. Despite being paradoxical, it has been demonstrated that, in addition to its enzymatic role in normal metabolism, this enzyme also plays a role in tumors that arise in gluconeogenic and non-gluconeogenic organs. According to newly available research, it has metabolic and non-metabolic roles in tumor progression and development. Thus, this review will give insight into PCK1 relationship, function, and mechanism in or with different types of cancer using contemporary findings.

Apilimod enhances specific productivity in recombinant CHO cells through cell cycle arrest and mediation of autophagy

Chinese hamster ovary (CHO) cells are expected to acquire the ability to produce higher recombinant therapeutic protein levels using various strategies. Genetic engineering targeting the cell cycle and autophagy pathways in the regulation of cell death in CHO cell cultures has received attention for enhancing the production of therapeutic proteins. In this study, we examined the small-molecule compound apilimod, which was found to have a positive influence on recombinant protein expression in CHO cells. This was confirmed by selective blocking of the cell cycle at the G0/G1 phase. Apilimod treatment resulted in decreased expression of cyclin-dependent kinase 3 (CDK3) and Cyclin C and increased expression of cyclin-dependent kinase suppressor p27Kip1, which are critical regulators of G1 cell cycle progression and important targets controlling cell proliferation. Furthermore, total transcription factor EB (TFEB) was lower in apilimod-treated CHO cells than in control cells, resulting in decreased lysosome biogenesis and autophagy with apilimod treatment. These multiple effects demonstrate the potential of apilimod for development as a novel enhancer for the production of recombinant proteins in CHO cell engineering.

The rates of adult neurogenesis and oligodendrogenesis are linked to cell cycle regulation through p27-dependent gene repression of SOX2

Cell differentiation involves profound changes in global gene expression that often has to occur in coordination with cell cycle exit. Because cyclin-dependent kinase inhibitor p27 reportedly regulates proliferation of neural progenitor cells in the subependymal neurogenic niche of the adult mouse brain, but can also have effects on gene expression, we decided to molecularly analyze its role in adult neurogenesis and oligodendrogenesis. At the cell level, we show that p27 restricts residual cyclin-dependent kinase activity after mitogen withdrawal to antagonize cycling, but it is not essential for cell cycle exit. By integrating genome-wide gene expression and chromatin accessibility data, we find that p27 is coincidentally necessary to repress many genes involved in the transit from multipotentiality to differentiation, including those coding for neural progenitor transcription factors SOX2, OLIG2 and ASCL1. Our data reveal both a direct association of p27 with regulatory sequences in the three genes and an additional hierarchical relationship where p27 repression of Sox2 leads to reduced levels of its downstream targets Olig2 and Ascl1. In vivo, p27 is also required for the regulation of the proper level of SOX2 necessary for neuroblasts and oligodendroglial progenitor cells to timely exit cell cycle in a lineage-dependent manner.

Heat enhances the inhibitory effect of lipopolysaccharide on duck granulosa cell proliferation and steroid biosynthesis in vitro

Lipopolysaccharide (LPS) reduces the reproductive performance of laying ducks, especially during the hot summer months. To study the underlying mechanisms, we investigated the effects of different LPS concentrations and heat on duck granulosa cell (GC) proliferation and steroid biosynthesis in vitro. We investigated GC proliferation, secretion, and activation of the MAPK pathway. The cell cycle results showed that LPS treatment alone did not significantly affect cell proliferation, whereas the mRNA expression levels of IGF2, IGFBP2, and CyclinD1 were downregulated and p27kip1 was significantly upregulated after 2000 ng/mL LPS treatment when compared to untreated cells. In steroid hormone synthesis, although LPS increased the expression of most steroid biosynthesis genes, it inhibited the expression of CYP11A1 at high LPS concentrations. High temperatures enhanced the inhibitory effect of LPS on the expression of proliferation-promoting genes. Heat significantly reduced CYP11A1 and CYP19A1 expression. In addition, the phosphorylation of P38 was significantly upregulated by high temperatures combined with LPS, whereas the phosphorylation of ERK1/2 and JNK was downregulated. The relative protein expression of Bax/BCL-2 was upregulated at high temperatures in combination with LPS. Heat treatment enhanced the inhibitory effects of LPS on the proliferation and hormone biosynthesis of duck GCs in vitro.

CDK regulators—Cell cycle progression or apoptosis—Scenarios in normal cells and cancerous cells

Serine/threonine kinases called cyclin-dependent kinases (CDKs) interact with cyclins and CDK inhibitors (CKIs) to control the catalytic activity. CDKs are essential controllers of RNA transcription and cell cycle advancement. The ubiquitous overactivity of the cell cycle CDKs is caused by a number of genetic and epigenetic processes in human cancer, and their suppression can result in both cell cycle arrest and apoptosis. This review focused on CDKs, describing their kinase activity, their role in phosphorylation inhibition, and CDK inhibitory proteins (CIP/KIP, INK 4, RPIC). We next compared the role of different CDKs, mainly p21, p27, p57, p16, p15, p18, and p19, in the cell cycle and apoptosis in cancer cells with respect to normal cells. The current work also draws attention to the use of CDKIs as therapeutics, overcoming the pharmacokinetic barriers of pan-CDK inhibitors, analyze new chemical classes that are effective at attacking the CDKs that control the cell cycle (cdk4/6 or cdk2). It also discusses CDKI's drawbacks and its combination therapy against cancer patients. These findings collectively demonstrate the complexity of cancer cell cycles and the need for targeted therapeutic intervention. In order to slow the progression of the disease or enhance clinical outcomes, new medicines may be discovered by researching the relationship between cell death and cell proliferation.

p27kip1 Modulates the Morphology and Phagocytic Activity of Microglia

p27kip1 is a multifunctional protein that promotes cell cycle exit by blocking the activity of cyclin/cyclin-dependent kinase complexes as well as migration and motility via signaling pathways that converge on the actin and microtubule cytoskeleton. Despite the broad characterization of p27kip1 function in neural cells, little is known about its relevance in microglia. Here, we studied the role of p27kip1 in microglia using a combination of in vitro and in situ approaches. While the loss of p27kip1 did not affect microglial density in the cerebral cortex, it altered their morphological complexity in situ. However, despite the presence of p27kip1 in microglial processes, as shown by immunofluorescence in cultured cells, loss of p27kip1 did not change microglial process motility and extension after applying laser-induced brain damage in cortical brain slices. Primary microglia lacking p27kip1 showed increased phagocytic uptake of synaptosomes, while a cell cycle dead variant negatively affected phagocytosis. These findings indicate that p27kip1 plays specific roles in microglia.

Activation of estrogen receptor ESR1 and ESR2 induces proliferation of the human testicular embryonal carcinoma NT2/D1 cells

The aims of the present study were to investigate the expression of the classic estrogen receptors ESR1 and ESR2, the splicing variant ESR1-36 and GPER in human testicular embryonal carcinoma NT2/D1 cells, and the effects of the activation of the ESR1 and ESR2 on cell proliferation. Immunostaining of ESR1, ESR2, and GPER were predominantly found in the nuclei, and less abundant in the cytoplasm. ESR1-36 isoform was predominantly expressed in the perinuclear region and cytoplasm, and some weakly immunostained in the nuclei. In nonstimulated NT2/D1 cells (control), proteins of the cell cycle CCND1, CCND2, CCNE1 and CDKN1B are present. Activation of ESR1 and ESR2 increases, respectively, CCND2 and CCNE1 expression, but not CCND1. Activation of ESR2 also mediates upregulation of the cell cycle inhibitor CDKN1B. This protein co-immunoprecipitated with CCND2. Also, E2 induces an increase in the number and viability of the NT2/D1 cells. These effects are blocked by simultaneous pretreatment with ESR1-and ESR2-selective antagonists, confirming that both estrogen receptors regulate NT2/D1 cell proliferation. In addition, E2 increases SRC phosphorylation, and SRC mediates cell proliferation. Our study provides novel insights into the signatures and molecular mechanisms of estrogen receptor in NT2/D1 cells.

The cyclin-dependent kinase inhibitor p27Kip1 interacts with the aryl hydrocarbon receptor and negatively regulates its transcriptional activity

p27^Kip1 functions to coordinate cell cycle progression through the inhibition of cyclin-dependent kinase (CDK) complexes. p27^Kip1 also exerts distinct activities beyond CDK-inhibition, including functioning as a transcriptional regulator. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor with diverse biological roles. The regulatory inputs that control AhR-mediated transcriptional responses are an active area of investigation. AhR was previously established as a direct regulator of p27^Kip1 transcription. Here, we report the physical interaction of AhR and p27^Kip1 and show that p27^Kip1 expression negatively regulates AhR-mediated transcription. p27^Kip1 knockout cells display increased AhR nuclear localisation and significantly higher expression of AhR target genes. This work thus identifies new regulatory cross-talk between p27^Kip1 and AhR.

Immunohistochemical Profile of Parathyroid Tumours: A Comprehensive Review

Immunohistochemistry remains an indispensable tool in diagnostic surgical pathology. In parathyroid tumours, it has four main applications: to detect (1) loss of parafibromin; (2) other manifestations of an aberrant immunophenotype hinting towards carcinoma; (3) histogenesis of a neck mass and (4) pathogenetic events, including features of tumour microenvironment and immune landscape. Parafibromin stain is mandatory to identify the new entity of parafibromin-deficient parathyroid neoplasm, defined in the WHO classification (2022). Loss of parafibromin indicates a greater probability of malignant course and should trigger the search for inherited or somatic CDC73 mutations. Aberrant immunophenotype is characterised by a set of markers that are lost (parafibromin), down-regulated (e.g., APC protein, p27 protein, calcium-sensing receptor) or up-regulated (e.g., proliferation activity by Ki-67 exceeding 5%) in parathyroid carcinoma compared to benign parathyroid disease. Aberrant immunophenotype is not the final proof of malignancy but should prompt the search for the definitive criteria for carcinoma. Histogenetic studies can be necessary for differential diagnosis between thyroid vs. parathyroid origin of cervical or intrathyroidal mass; detection of parathyroid hormone (PTH), chromogranin A, TTF-1, calcitonin or CD56 can be helpful. Finally, immunohistochemistry is useful in pathogenetic studies due to its ability to highlight both the presence and the tissue location of certain proteins. The main markers and challenges (technological variations, heterogeneity) are discussed here in the light of the current WHO classification (2022) of parathyroid tumours.

In vitro Effects of Biologically Active Vitamin D on Myogenesis: A Systematic Review

Vitamin D (VD) deficiency is associated with muscle weakness. A reduction in the incidence of falls in the elderly following VD supplementation and identification of the VD receptor within muscle cells suggests a direct effect of VD on muscle, but little is known about the underlying mechanisms. Here we systematically searched the literature to identify effects of active VD [1,25(OH)2D3] on skeletal muscle myogenesis in vitro, with no restriction on year of publication. Eligibility was assessed by strict inclusion/exclusion criteria and agreed by two independent investigators. Twelve relevant pa-pers were identified using four different cell types (C2C12, primary mouse satellite cells, primary chick myoblasts, and primary human myoblasts) and a range of myogenic markers (myoD, myogenin, creatine kinase, myosin heavy chain, and myotube size). A clear inhibitory effect of 1,25(OH)2D3 on proliferation was reported, while the effects on the different stages of differentiation were less consistent probably due to variation in cell type, time points and doses of 1,25(OH)2D3 used. However, myotube size was consistently increased by 1,25(OH)2D3. Overall, the evidence suggests that 1,25(OH)2D3 inhibits proliferation and promotes differentiation of myoblasts, but future studies should use time courses to gain a clearer understanding.

p27Kip1, an Intrinsically Unstructured Protein with Scaffold Properties

The Cyclin-dependent kinase (CDK) regulator p27^Kip1 is a gatekeeper of G1/S transition. It also regulates G2/M progression and cytokinesis completion, via CDK-dependent or -independent mechanisms. Recently, other important p27^Kip1 functions have been described, including the regulation of cell motility and migration, the control of cell differentiation program and the activation of apoptosis/autophagy. Several factors modulate p27^Kip1 activities, including its level, cellular localization and post-translational modifications. As a matter of fact, the protein is phosphorylated, ubiquitinated, SUMOylated, O-linked N-acetylglicosylated and acetylated on different residues. p27^Kip1 belongs to the family of the intrinsically unstructured proteins and thus it is endowed with a large flexibility and numerous interactors, only partially identified. In this review, we look at p27^Kip1 properties and ascribe part of its heterogeneous functions to the ability to act as an anchor or scaffold capable to participate in the construction of different platforms for modulating cell response to extracellular signals and allowing adaptation to environmental changes.

Chromosome microarray characterisation of chromosome arm 12p loss associated with complex molecular karyotype and recurrent adverse cytogenetic markers in multiple myeloma

Copy number loss within chromosome 12 short arm (12p) has gained attention as an adverse cytogenetic marker in multiple myeloma. The prognostic significance and characterisation of the common minimal deleted region remains controversial between various studies with loss of CD27 proposed as the putative critical gene. We aimed to determine the frequency of 12p loss, its correlation with adverse cytogenetic markers further to define and characterise 12p deletions. Our study included a prospective cohort of 574 multiple myeloma patients referred for cytogenetic testing, including interphase fluorescence in situ hybridisation for IGH (14q32.33) translocations and chromosome microarray. Loss of 12p was detected in 54/574 (9.4%) patients and when compared with the non-12p loss group [520/574 (90.6%)], 12p loss patients demonstrated a statistically significant association with specific recurrent cytogenetic markers: complex molecular karyotypes (98.1% vs 45.2%), 1p loss (50.0% vs 20.2%), t(4;14) (20.4% vs 7.7%), 8p loss (37.0% vs 15.0%), 13/13q loss (70.4% vs 41.7%), and 17p loss (33.3% vs 6.5%). The size and location of 12p losses were heterogeneous with a common 0.88 Mb minimally deleted region that included ~9 genes from ETV6 to CDKN1B in 52/54 (~96.3%) patients but did not include CD27. Our findings support 12p loss being a secondary chromosome abnormality frequently co-occurring with adverse cytogenetic markers and complex molecular karyotypes indicative of chromosome instability.

Establishing and maintaining fertility: the importance of cell cycle arrest

In this review, Frost et al. summarize the current knowledge on the Cip/Kip family of cyclin-dependent kinase inhibitors in mouse gonad development and highlight new roles for cell cycle inhibitors in controlling and maintaining female fertility.

Development of the ovary or testis is required to establish reproductive competence. Gonad development relies on key cell fate decisions that occur early in embryonic development and are actively maintained. During gonad development, both germ cells and somatic cells proliferate extensively, a process facilitated by cell cycle regulation. This review focuses on the Cip/Kip family of cyclin-dependent kinase inhibitors (CKIs) in mouse gonad development. We particularly highlight recent single-cell RNA sequencing studies that show the heterogeneity of cyclin-dependent kinase inhibitors. This diversity highlights new roles for cell cycle inhibitors in controlling and maintaining female fertility.

Stimulation of c-Jun/AP-1-Activity by the Cell Cycle Inhibitor p57Kip2

p57 is a member of the Cip/Kip family of cell cycle inhibitors which restrict the eukaryotic cell cycle by binding to and inhibiting cyclin/CDK complexes. They are considered as tumor suppressors and inactivating genomic mutations of p57 are associated with human overgrowth disorders. Increasing evidence suggests that p57 controls additional cellular processes beyond cell cycle control such as apoptosis, cell migration or transcription. Here we report that p57 can stimulate AP-1 promotor activity. While transactivation by c-Jun is strongly activated by p57, it did not enhance c-Fos induced transcription. This indicates that c-Jun is the target of p57 in the canonical AP-1 heterodimeric transcription factor. We could detect endogenous p57/c-Jun containing complexes in cells by co-immunoprecipitation. The strong stimulation of c-Jun activity is not the consequence of activating phosphorylation in the transactivation domain (TAD) of c-Jun, but rather due to negative interference with c-Jun repressors and positive interference with c-Jun activators. In contrast to full-length p57, the amino- and carboxy-terminal domains of p57 are insufficient for a significant activation of c-Jun induced transcription. When expressed in presence of full length p57, the p57 C-terminus abrogated and the N-terminus enhanced c-Jun activation. This indicates that the C-terminus may bind and sequester a putative activator of c-Jun, whereas the N-terminus may sequester a c-Jun repressor. Interestingly, the p57 aminoterminus is sufficient for binding to the two c-Jun repressors HDAC1 and HDAC3. These data are consistent with a model of c-Jun activation where p57 is a part of large nuclear remodeling/transcription complexes. p57 might stimulate transcription by inhibiting transcription repressor proteins like HDACs via its N-terminus and/or attracting transcription activators through its C-terminus. These data suggest that in addition to its role as a CDK inhibitor and tumor suppressor, p57 may also exert tumor promoting functions by activation of the proto-oncoprotein c-Jun.

A New CYP2E1 Inhibitor, 12-Imidazolyl-1-dodecanol, Represents a Potential Treatment for Hepatocellular Carcinoma

Cytochrome P450 2E1 (CYP2E1) is a key target protein in the development of alcoholic and nonalcoholic fatty liver disease (FLD). The pathophysiological correlate is the massive production of reactive oxygen species. The role of CYP2E1 in the development of hepatocellular carcinoma (HCC), the final complication of FLD, remains controversial. Specifically, CYP2E1 has not yet been defined as a molecular target for HCC therapy. In addition, a CYP2E1-specific drug has not been developed. We have already shown that our newly developed CYP2E1 inhibitor 12-imidazolyl-1-dodecanol (I-ol) was therapeutically effective against alcoholic and nonalcoholic steatohepatitis. In this study, we investigated the effect of I-ol on HCC tumorigenesis and whether I-ol could serve as a possible treatment option for terminal-stage FLD. I-ol exerted a very highly significant antitumour effect against hepatocellular HepG2 cells. Cell viability was reduced in a dose-dependent manner, with only the highest doses causing a cytotoxic effect associated with caspase 3/7 activation. Comparable results were obtained for the model colorectal adenocarcinoma cell line, DLD-1, whose tumorigenesis is also associated with CYP2E1. Transcriptome analyses showed a clear effect of I-ol on apoptosis and cell-cycle regulation, with the increased expression of p27Kip1 being particularly noticeable. These observations were confirmed at the protein level for HepG2 and DLD-1 cells grafted on a chorioallantoic membrane. Cell-cycle analysis showed a complete loss of proliferating cells with a simultaneous increase in S-phase arrest beginning at a threshold dose of 30 μM. I-ol also reduced xenograft tumour growth in nude mice. This antitumour effect was not associated with tumour cachexia. I-ol was not toxic to healthy tissues or organs. This study demonstrates for the first time the therapeutic effect of the specific CYP2E1 inhibitor I-ol on the tumorigenesis of HCC. Our findings imply that I-ol can potentially be applied therapeutically on patients at the final stage of FLD.

AMG900 as novel inhibitor of the translationally controlled tumor protein

INTRODUCTION

Cancer is one of the leading causes of death worldwide. Classical cytotoxic chemotherapy exerts high side effects and low tumor selectivity. Translationally controlled tumor protein (TCTP) is a target for differentiation therapy, a promising, new therapeutic approach, which is expected to be more selective and less toxic than cytotoxic chemotherapy. The aim of the present investigation was to identify novel TCTP inhibitors.

METHODS

We performed in silico screening and molecular docking using a chemical library of more than 31,000 compounds to identify a novel inhibitor of TCTP. We tested AMG900 in vitro for binding to TCTP by microscale thermophoresis and co-immunoprecipitation. Additionally, we examined the effect of TCTP blockade on cell cycle progression by flow cytometry and Western blotting and cancer cell survival by resazurin assays in MCF-7, SK-OV3 and MOLT-4 cell lines.

RESULTS

We identified AMG900 as new inhibitor of TCTP. AMG900 bound to the p53 binding site of TCTP with a free binding energy of -9.63 ± 0.01 kcal/mol. This compound decreased TCTP expression to 23.4 ± 1.59% and increased p53 expression to 194.29 ± 24.27%. Furthermore, AMG900 induced G0/G1 arrest as shown by flow cytometry and Western blot of relevant cell cycle proteins. AMG900 decreased CDK2, CDK4, CDK6, cyclin D1 and cyclin D3 expression, whereas p18, p21 and p27 expression increased. Moreover, AMG900 disturbed TCTP-p53 complexation as shown by co-immunoprecipitation and increased expression of free p53.

DISCUSSION

AMG900 may serve as novel lead compound for the development of differentiation therapy approaches against cancer.

Regulation of Hemogenic Endothelial Cell Development and Function

Embryonic definitive hematopoiesis generates hematopoietic stem and progenitor cells (HSPCs) essential for establishment and maintenance of the adult blood system. This process requires the specification of a subset of vascular endothelial cells to become blood-forming, or hemogenic, and the subsequent endothelial-to-hematopoietic transition to generate HSPCs therefrom. The mechanisms that regulate these processes are under intensive investigation, as their recapitulation in vitro from human pluripotent stem cells has the potential to generate autologous HSPCs for clinical applications. In this review, we provide an overview of hemogenic endothelial cell development and highlight the molecular events that govern hemogenic specification of vascular endothelial cells and the generation of multilineage HSPCs from hemogenic endothelium. We also discuss the impact of hemogenic endothelial cell development on adult hematopoiesis.

Regulation of p27Kip1 and p57Kip2 Functions by Natural Polyphenols

In numerous instances, the fate of a single cell not only represents its peculiar outcome but also contributes to the overall status of an organism. In turn, the cell division cycle and its control strongly influence cell destiny, playing a critical role in targeting it towards a specific phenotype. Several factors participate in the control of growth, and among them, p27^Kip1 and p57^Kip2, two proteins modulating various transitions of the cell cycle, appear to play key functions. In this review, the major features of p27 and p57 will be described, focusing, in particular, on their recently identified roles not directly correlated with cell cycle modulation. Then, their possible roles as molecular effectors of polyphenols’ activities will be discussed. Polyphenols represent a large family of natural bioactive molecules that have been demonstrated to exhibit promising protective activities against several human diseases. Their use has also been proposed in association with classical therapies for improving their clinical effects and for diminishing their negative side activities. The importance of p27^Kip1 and p57^Kip2 in polyphenols’ cellular effects will be discussed with the aim of identifying novel therapeutic strategies for the treatment of important human diseases, such as cancers, characterized by an altered control of growth.

AKT/GSK-3β/β-catenin signaling pathway participates in erythropoietin-promoted glioma proliferation

PURPOSE

Although erythropoietin (EPO) has been proven to significantly promote the proliferation of cancer cells, the mechanism for promoting glioma proliferation is poorly understood. Here, we examined the functional role of the AKT/GSK-3β/β-catenin signaling pathway in the EPO-mediated proliferation of glioma.

METHODS

The distribution of EPO and Ki-67 among clinical samples with different WHO grades was plotted by Immunological Histological Chemistry analysis. U87 and U251 glioma cell lines were treated with short hairpin RNA targeting (shEPO), recombinant human erythropoietin (rhEPO) and/or AKT-specific inhibitor (MK-2206). The changes in phosphorylated AKT, nuclear β-catenin, cyclin D1 and p27kip1 expression were detected. Cell cycle distributions and glioma proliferation in vitro and in vivo were analyzed.

RESULTS

The expression level of EPO was significantly elevated with the increase of WHO grade and Ki67 in clinical glioma specimens. In vitro, knockdown of endogenous EPO in U87 and U251 cells effectively block the phosphorylation of AKT and GSK-3β and the expression of nuclear β-catenin. shEPO treatment also significantly decreased the expression of cyclin D1 and increased the expression of p27kip1. The cell cycle transition then slowed down and the proliferation of glioma cells or mouse xenograft tumors both decreased. Treatment of cells or tumors with extra rhEPO reversed the above biological effects mediated by shEPO. rhEPO-induced activation of the AKT/GSK-3β/β-catenin pathway and proliferation were abolished by MK-2206.

CONCLUSIONS

Our study identified the AKT/GSK-3β/β-catenin axis as a critical mediator of EPO-induced glioma proliferation and further provided a clinically significant dimension to the biology of EPO.

Common Functions of Disordered Proteins across Evolutionary Distant Organisms

Intrinsically disordered proteins and regions typically lack a well-defined structure and thus fall outside the scope of the classic sequence–structure–function relationship. Hence, classic sequence- or structure-based bioinformatic approaches are often not well suited to identify homology or predict the function of unknown intrinsically disordered proteins. Here, we give selected examples of intrinsic disorder in plant proteins and present how protein function is shared, altered or distinct in evolutionary distant organisms. Furthermore, we explore how examining the specific role of disorder across different phyla can provide a better understanding of the common features that protein disorder contributes to the respective biological mechanism.

VCP/p97 targets the nuclear export and degradation of p27Kip1 during G1 to S phase transition

One of the critical regulatory mechanisms for cell cycle progression is the timely degradation of CDK inhibitors, including p21^Cip1 and p27^Kip1 . VCP/p97, an AAA-ATPase, is reported to be overexpressed in many types of cancers. Here, we found that treatment of MCF-7 human breast cancer cells with DBeQ, a VCP inhibitor, or VCP knockdown in MCF-7 cells arrested cells at G1 phase, accompanied with the blockage of both p21 and p27 degradation. Whereas, double knockdown of p21 and p27 in MCF-7 cells rendered cells refractory to DBeQ-induced G1 arrest. Moreover, inhibition or knockdown of VCP or UFD1, one of VCP's co-factors, in MCF-7, NIH3T3, or HEK293T cells blocked the nuclear export of p27 during earlier G1 phase after mitogen stimulation. We also identified the nuclear localization sequence (NLS) of VCP, and found that adding back wild-type VCP, not the NLS-deleted VCP mutant, restored the nuclear export and degradation of p27 in VCP knockout MCF-7 cells. Importantly, we found that VCP inhibition sensitized breast cancer cells to the treatment of several anticancer therapeutics both in vitro and in vivo. Taken together, our study not only uncovers the mechanisms underlying VCP-mediated cell proliferation control but also provides potential therapeutic option for cancer treatment.

MYC Oncogene Contributions to Release of Cell Cycle Brakes

Promotion of the cell cycle is a major oncogenic mechanism of the oncogene c-MYC (MYC). MYC promotes the cell cycle by not only activating or inducing cyclins and CDKs but also through the downregulation or the impairment of the activity of a set of proteins that act as cell-cycle brakes. This review is focused on the role of MYC as a cell-cycle brake releaser i.e., how MYC stimulates the cell cycle mainly through the functional inactivation of cell cycle inhibitors. MYC antagonizes the activities and/or the expression levels of p15, ARF, p21, and p27. The mechanism involved differs for each protein. p15 (encoded by CDKN2B) and p21 (CDKN1A) are repressed by MYC at the transcriptional level. In contrast, MYC activates ARF, which contributes to the apoptosis induced by high MYC levels. At least in some cells types, MYC inhibits the transcription of the p27 gene (CDKN1B) but also enhances p27's degradation through the upregulation of components of ubiquitin ligases complexes. The effect of MYC on cell-cycle brakes also opens the possibility of antitumoral therapies based on synthetic lethal interactions involving MYC and CDKs, for which a series of inhibitors are being developed and tested in clinical trials.

p27Kip1 - p(RhoB)lematic in lung cancer

Lung cancer is the leading cause of cancer mortality worldwide, with adenocarcinomas of the non‐small cell lung carcinoma (NSCLC) subtype accounting for the majority of cases. Therefore, an urgent need exists for a more detailed dissection of the molecular events driving NSCLC development and the identification of clinically relevant biomarkers. Even though originally identified as a tumour suppressor, recent studies associate the cytoplasmically (mis)localised CDK inhibitor p27^Kip1 (p27) with unfavourable responses to chemotherapy and poor outcomes in NSCLC, supporting the hypothesis that the protein can execute oncogenic activities. In a recent issue of The Journal of Pathology, Calvayrac and coworkers uncover a novel molecular mechanism that can explain this oncogenic role of p27. They demonstrate that cytoplasmic p27 binds and inhibits the small GTPase RhoB and thereby relieves a selection pressure for RhoB loss that is frequently observed in NSCLC. This is supported not only by studies with genetically modified mice, but also through identification of a cohort of human lung cancer patients with cytoplasmic p27 and continued RhoB expression, where this signature correlates with decreased survival. This not only establishes a potentially useful biomarker, but also provides yet another facet of the complex roles p27 undertakes in tumourigenesis. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Gold nanoparticles-loaded anti-miR221 enhances antitumor effect of sorafenib in hepatocellular carcinoma cells

Objective: Currently, sorafenib is the main systemic chemotherapy drug for advanced stage of hepatocellular carcinoma (HCC). However, emerging data from some clinical HCC patients indicates that sorafenib alone has only moderate antitumor efficacy, and could not inhibit metastasis and progression of disease. MiR-221 plays a role in promoting tumorigenesis in HCC by inhibiting the expression of p27. In this study, we analyzed the synergistic anti-tumor effects of sorafenib and gold nanoparticles-loaded anti-miR221 on HCC cell lines. Methods: Gold nanoparticles-loaded anti-miR221 was investigated and identified by transmission electron microscope, ultraviolet-visible spectroscopy, zeta potential and dynamic light scattering measurements as well as the confocal microscopy and dark-field imaging. Two HCC cell lines were treated with sorafenib and AuNPs-anti-miR221 alone or combination in vitro to investigate the inhibitory effect by CCK-8, live/dead fluorescence staining and colony-forming unit assays. MiR-221/p27/DNMT1 signaling pathway including p27 and DNMT1 was examined by western blot. Results: AuNPs-anti-miR221 can enhance the effect of sorafenib in inhibiting cell proliferation via inactivating miR-221/p27/DNMT1 signaling pathway. Conclusions: Our results demonstrate that sorafenib combined with AuNPs-anti-miR221 treatment does effectively inhibit proliferation of HCC cell lines synergistically. These data suggest the AuNPs-anti-miR221 may be a promising chemosensitizer to sorafenib in the treatment of HCC.