Inhibition of PI3K/Akt pathway impairs G2/M transition of cell cycle in late developing progenitors of the avian embryo retina

Silva H, P. de Carvalho R, Ventura ALM, Calaza KC, Silveira MS, Kubrusly RCC, de Melo Reis RA. The Healthy and Diseased Retina Seen through Neuron-Glia Interactions

The retina is the sensory tissue responsible for the first stages of visual processing, with a conserved anatomy and functional architecture among vertebrates. To date, retinal eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, glaucoma, and others, affect nearly 170 million people worldwide, resulting in vision loss and blindness. To tackle retinal disorders, the developing retina has been explored as a versatile model to study intercellular signaling, as it presents a broad neurochemical repertoire that has been approached in the last decades in terms of signaling and diseases. Retina, dissociated and arranged as typical cultures, as mixed or neuron- and glia-enriched, and/or organized as neurospheres and/or as organoids, are valuable to understand both neuronal and glial compartments, which have contributed to revealing roles and mechanisms between transmitter systems as well as antioxidants, trophic factors, and extracellular matrix proteins. Overall, contributions in understanding neurogenesis, tissue development, differentiation, connectivity, plasticity, and cell death are widely described. A complete access to the genome of several vertebrates, as well as the recent transcriptome at the single cell level at different stages of development, also anticipates future advances in providing cues to target blinding diseases or retinal dysfunctions.

PIK Your Poison: The Effects of Combining PI3K and CDK Inhibitors against Metastatic Cutaneous Squamous Cell Carcinoma In Vitro

Cutaneous squamous cell carcinoma (cSCC) is a very common skin malignancy with poor prognosis for patients with locally advanced or metastatic cSCC (mcSCC). PI3K/AKT/mTOR and cell cycle signalling pathways are often dysregulated in mcSCC. A combination drug approach has been theorised to overcome the underwhelming clinical performance of targeted inhibitors as single agents. This study investigates the potential of targeted inhibition of the p110α-subunit of PI3K with PIK-75 or BGT226 (P13Ki), and of CDK1/2/5/9 with dinaciclib (CDKi) as single agents and in combination. The patient-derived mcSCC cell lines, UW-CSCC1 and UW-CSCC2, were used to assess cell viability, migration, cell signalling, cell cycle distribution, and apoptosis. PIK-75, BGT226, and dinaciclib exhibited strong cytotoxic potency as single agents. Notably, the non-malignant HaCaT cell line was unaffected. In 2D cultures, PIK-75 synergistically enhanced the cytotoxic effects of dinaciclib in UW-CSCC2, but not UW-CSCC1. Interestingly, this pattern was reversed in 3D spheroid models. Despite the combination of PIK-75 and dinaciclib resulting in an increase in cell cycle arrest and apoptosis, and reduced cell motility, these differences were largely negligible compared to their single-agent counterpart. The differential responses between the cell lines correlated with driver gene mutation profiles. These findings suggest that personalised medicine approaches targeting PI3K and CDK pathways in combination may yield some benefit for mcSCC, and that more complex 3D models should be considered for drug responsiveness studies in this disease.

Hypoxia Modulates Radiosensitivity and Response to Different Radiation Qualities in A549 Non-Small Cell Lung Cancer (NSCLC) Cells

Hypoxia-induced radioresistance reduces the efficacy of radiotherapy for solid malignancies, including non-small cell lung cancer (NSCLC). Cellular hypoxia can confer radioresistance through cellular and tumor micro-environment adaptations. Until recently, studies evaluating radioresistance secondary to hypoxia were designed to maintain cellular hypoxia only before and during irradiation, while any handling of post-irradiated cells was carried out in standard oxic conditions due to the unavailability of hypoxia workstations. This limited the possibility of simulating in vivo or clinical conditions in vitro. The presence of molecular oxygen is more important for the radiotoxicity of low-linear energy transfer (LET) radiation (e.g., X-rays) than that of high-LET carbon (12C) ions. The mechanisms responsible for 12C ions' potential to overcome hypoxia-induced radioresistance are currently not fully understood. Therefore, the radioresistance of hypoxic A549 NSCLC cells following exposure to X-rays or 12C ions was investigated along with cell cycle progression and gene expression by maintaining hypoxia before, during and after irradiation. A549 cells were incubated under normoxia (20% O2) or hypoxia (1% O2) for 48 h and then irradiated with X-rays (200 kV) or 12C ions (35 MeV/n, LET ~75 keV/µm). Cell survival was evaluated using colony-forming ability (CFA) assays immediately or 24 h after irradiation (late plating). DNA double-strand breaks (DSBs) were analyzed using γH2AX immunofluorescence microscopy. Cell cycle progression was determined by flow cytometry of 4',6-diamidino-2-phenylindole-stained cells. The global transcription profile post-irradiation was evaluated by RNA sequencing. When hypoxia was maintained before, during and after irradiation, hypoxia-induced radioresistance was observed only in late plating CFA experiments. The killing efficiency of 12C ions was much higher than that of X-rays. Cell survival under hypoxia was affected more strongly by the timepoint of plating in the case of X-rays compared to 12C ions. Cell cycle arrest following irradiation under hypoxia was less pronounced but more prolonged. DSB induction and resolution following irradiation were not significantly different under normoxia and hypoxia. Gene expression response to irradiation primarily comprised cell cycle regulation for both radiation qualities and oxygen conditions. Several PI3K target genes involved in cell migration and cell motility were differentially upregulated in hypoxic cells. Hypoxia-induced radioresistance may be linked to altered cell cycle response to irradiation and PI3K-mediated changes in cell motility and migration in A549 cells rather than less DNA damage or faster repair.

Cell cycle regulation by ADP and IGF-1 in cultured late developing glia progenitors of the avian retina

In the avian retina, ADP induces the proliferation of late developing glia progenitors. Here, we show that in serum-containing retinal cell cultures, ADP-induced increase in [3H]-thymidine incorporation can be prevented by the IGF-1 receptor antagonists AG1024 and I-OMe-Tyrphostin AG 538, suggesting the participation of IGF-1 in ADP-mediated progenitor proliferation. In contrast, no increase in [3H]-thymidine incorporation is observed in retinal cultures treated only with IGF-1. Under serum starvation, while no increase in cell proliferation is detected in cultures treated only with ADP or IGF-1, a significant increase in [3H]-thymidine incorporation and number of PCNA expressing cells is observed in cultures treated concomitantly with ADP plus IGF-1, suggesting that both molecules are required to induce proliferation of retinal progenitors. In serum-starved cultures, although an increase in cell viability is detected by MTT assays in IGF-1-treated cultures, no significant increase in viability of [3H]-thymidine labeled progenitors is observed, suggesting that IGF-1 may contribute to survival of postmitotic cells in culture. While only ADP increases intracellular calcium, only IGF-1 induces the phosphorylation of Akt in the retinal cultures. IGF-1 through the PI3K/Akt pathway induces a significant increase in the transcription and expression of CDK1 with a decrease in phospho-histone H3 expression that is concomitant with an increase in the expression of cyclins D1 and E and CDK2. These findings suggest that IGF-1 stimulates CDK-1 mRNA and protein expression that enable progenitors to progress through the cell cycle. However, signaling of ADP in the presence IGF-I seems to be required for DNA synthesis.

A Role of PI3K/Akt Signaling in Oocyte Maturation and Early Embryo Development

A serine/threonine-specific protein kinase B (PKB), also known as Akt, is a key factor in the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway that regulates cell survival, metabolism and proliferation. Akt phosphorylates many downstream specific substrates, which subsequently control the nuclear envelope breakdown (NEBD), centrosome maturation, spindle assembly, chromosome segregation, and cytokinesis. In vertebrates, Akt is also an important player during oogenesis and preimplantation development. In the signaling pathways regulating mRNA translation, Akt is involved in the control of mammalian target of rapamycin complex 1 (mTORC1) and thereby regulates the activity of a translational repressor, the eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). In this review, we summarize the functions of Akt in mitosis, meiosis and early embryonic development. Additionally, the role of Akt in the regulation of mRNA translation is addressed with respect to the significance of this process during early development.

Chemical signaling in the developing avian retina: Focus on cyclic AMP and AKT-dependent pathways

Communication between developing progenitor cells as well as differentiated neurons and glial cells in the nervous system is made through direct cell contacts and chemical signaling mediated by different molecules. Several of these substances are synthesized and released by developing cells and play roles since early stages of Central Nervous System development. The chicken retina is a very suitable model for neurochemical studies, including the study of regulation of signaling pathways during development. Among advantages of the model are its very well-known histogenesis, the presence of most neurotransmitter systems found in the brain and the possibility to make cultures of neurons and/or glial cells where many neurochemical functions develop in a similar way than in the intact embryonic tissue. In the chicken retina, some neurotransmitters or neuromodulators as dopamine, adenosine, and others are coupled to cyclic AMP production or adenylyl cyclase inhibition since early stages of development. Other substances as vitamin C and nitric oxide are linked to the major neurotransmitter glutamate and AKT metabolism. All these different systems regulate signaling pathways, including PKA, PKG, SRC, AKT and ERK, and the activation of the transcription factor CREB. Dopamine and adenosine stimulate cAMP accumulation in the chick embryo retina through activation of D1 and A2a receptors, respectively, but the onset of dopamine stimulation is much earlier than that of adenosine. However, adenosine can inhibit adenylyl cyclase and modulate dopamine-dependent cAMP increase since early developmental stages through A1 receptors. Dopamine stimulates different PKA as well as EPAC downstream pathways both in intact tissue and in culture as the CSK-SRC pathway modulating glutamate NMDA receptors as well as vitamin C release and CREB phosphorylation. By the other hand, glutamate modulates nitric oxide production and AKT activation in cultured retinal cells and this pathway controls neuronal survival in retina. Glutamate and adenosine stimulate the release of vitamin C and this vitamin regulates the transport of glutamate, activation of NMDA receptors and AKT phosphorylation in cultured retinal cells. In the present review we will focus on these reciprocal interactions between neurotransmitters or neuromodulators and different signaling pathways during retinal development.

A Proteomic Platform Unveils the Brain Glycogen Phosphorylase as a Potential Therapeutic Target for Glioblastoma Multiforme

In the last few years, several efforts have been made to identify original strategies against glioblastoma multiforme (GBM): this requires a more detailed investigation of the molecular mechanism of GBM so that novel targets can be identified for new possible therapeutic agents. Here, using a combined biochemical and proteomic approach, we evaluated the ability of a blood–brain barrier-permeable 2,3-benzodiazepin-4-one, called 1g, to interfere with the activity and the expression of brain glycogen phosphorylase (PYGB) on U87MG cell line in parallel with the capability of this compound to inhibit the cell growth and cycle. Thus, our results highlighted PYGB as a potential therapeutic target in GBM prompting 1g as a capable anticancer drug thanks to its ability to negatively modulate the uptake and metabolism of glucose, the so-called “Warburg effect”, whose increase is considered a common feature of cancer cells in respect of their normal counterparts.

Biphasic dose-dependent G0/G1 and G2/M cell cycle arrest by synthetic 2,3-arylpyridylindole derivatives in A549 lung cancer cells

A collection of 2,3-arylpyridylindole derivatives were synthesized via the Larock heteroannulation and evaluated for their in vitro cytotoxic activity against A549 human lung cancer cells. Two derivatives expressed good cytotoxicity with IC 50 values of 1.18±0.25 μM and 0.87±0.10 μM and inhibited tubulin polymerization in vitro , with molecular docking studies suggesting the binding modes of the compounds in the colchicine binding site. Both derivatives have biphasic cell cycle arrest effects depending on their concentrations. At a lower concentration (0.5 μM), the two compounds induced G0/G1 cell cycle arrest by activating the JNK/p53/p21 pathway. At a higher concentration (2.0 μM), the two derivatives arrested the cell cycle at the G2/M phase via Akt signaling and inhibition of tubulin polymerization. Additional cytotoxic mechanisms of the two compounds involved the decreased expression of Bcl-2 and Mcl-1 antiapoptotic proteins through inhibition of the STAT3 and Akt signaling pathways.

Long Noncoding RNA Maternally Expressed Gene 3 Targets miR-30b and Regulates the AKT Serine/Threonine Kinase 1/Phosphoinositide 3-Kinase Signaling Pathway of H2O2-Induced Proliferation, Apoptosis, and Oxidative Stress in Retinal Ganglion Cells

Oxidative stress is an important factor affecting retinal ganglion cell (RGC) apoptosis. RGC apoptosis is the main pathophysiological feature of visual impairment as a result of glaucoma. Recently, it has been found that long noncoding RNA (lncRNA) and microRNAs are involved in RGC apoptosis. Here, the function of lncRNA maternally expressed gene 3 (MEG3) and miR-30b in H2 O2-induced RGC proliferation, apoptosis, and oxidative stress was investigated. The expression levels of MEG3 and miR-30b were detected by RT-PCR; the effects of MEG3 and miR-30b on the proliferation and apoptosis of RGCs were observed by flow cytometry; the levels of apoptosis-related proteins and AKT/PI3K signal pathway proteins were detected by protein immunoassay; and the regulation of miR-34a by pvt1 was verified by in vivo and in vitro experiments. The expression of MEG3 and miR-30b increased and decreased significantly in RGCs treated by H2O2. MEG3 expression decreased, apoptosis level-related proteins decreased, the apoptosis rate reduced, and the activity of MDA and SOD decreased. When the expression of miR-34a was inhibited, the proliferation rate of RGCs increased, the apoptosis rate decreased, and the level of apoptosis-related proteins decreased, which reversed MEG3’s effect on RGC apoptosis and proliferation. Furthermore, pvt1 could bind the miR-30b promoter and regulate it with in vitro expression and in vivo expression. Besides, we found that miR-30b can regulate the AKT/PI3K signaling pathway and participate in cell apoptosis and hyperplasia in stress response. LncRNA MEG3 targets miR-30b and regulates the AKT/PI3K signaling pathway on H2 O2-induced cell apoptosis, hyperplasia, and oxidative stress of RGCs.

Pyrroloquinoline Quinine and LY294002 Changed Cell Cycle and Apoptosis by Regulating PI3K-AKT-GSK3β Pathway in SH-SY5Y Cells

To verify the role of PI3K-AKT-GSK3β pathway during manganese (Mn)-induced cell death, apoptosis, related indicators were investigated. SH-SY5Y cells were directly exposed to different concentrations of MnCl₂. Then, cell viability, apoptosis, necrosis rate, and cell cycle were detected by MTT, FITC Annexin V Apoptosis Detection Kit with PI and PI staining. Then, in two intervention groups, cells were preconditioned with agonist (PQQ) and suppressant (LY294002). The cell viability decreased with a dose-response relationship (p < 0.05), while apoptosis and necrosis increased (p < 0.05). The ratio of G₀/G1 and G₂/M also decreased, but the percentage of S phase increased (p < 0.05). During above process, PI3K-AKT-GSK3β pathway was involved by regulating the expression of PI3K, AKT, p-AKT, and GSK3β (p < 0.05). For further research, cell cycle and apoptosis were detected pretreatment with PQQ and LY294002 before Mn exposure. The result showed cell ability, apoptosis, and necrosis rate changed obviously compared with non-pretreated group (p < 0.05). The variance of G0/G1 and G2/M ratio and percentage of S phase were also different, especially in 2.0 mM (p < 0.05). Mn can cause apoptosis and necrosis, varying cell cycle of SH-SY5Y cells, which could be changed by PQQ and LY294002 by regulating PI3K-AKT-GSK3β pathway.

Genistein Inhibits Proliferation of BRCA1 Mutated Breast Cancer Cells: The GPR30-Akt Axis as a Potential Target

Background

BRCA1 mutated breast cancer cells exhibit the elevated cell proliferation and the higher metastatic potential. G protein-coupled receptor 30 (GPR30) has been shown to regulate growth of hormonally responsive cancers, such as ovarian and breast cancers, and high expression of GPR30 is found in estrogen receptor (ER)-negative breast cancer cells. ER-negative breast cancer patients often have a mutation in the tumor suppressor gene, BRCA1. This study explored antiproliferative effects of genistein, a chemopreventive isoflavone present in legumes, and underlying molecular mechanisms in triple negative breast cancer cells with or without functionally active BRCA1.

Methods

Expression of BRCA1, GPR30 and Nrf2 was measured by Western blot analysis. Reactive oxygen species (ROS) accumulation was monitored by using the fluorescence-generating probe, 2’,7’-dichlorofluorescein diacetate. The effects of genistein on breast cancer cell viability and proliferation were assessed by the MTT, migration and clonogenic assays.

Results

The expression of GPR30 was dramatically elevated at both transcriptional and translational levels in BRCA1 mutated breast cancer cells compared to cells with wild-type BRCA1. Notably, there was diminished Akt phosporylation in GPR30 silenced cells. Treatment of BRCA1 silenced breast cancer cells with genistein resulted in the down-regulation of GPR30 expression and the inhibition of Akt phosphorylation as well as the reduced cell viability, migration and colony formation. Genistein caused cell cycle arrest at the G2/M phase in BRCA1-mutant cells through down-regulation of cyclin B1 expression. Furthermore, BRCA1-mutant breast cancer cells exhibited higher levels of intracellular ROS than those in the wild-type cells. Genistein treatment lowered the ROS levels through up-regulation of Nrf2 expression.

Conclusions

Lack of functional BRCA1 activates GPR30 signaling, thereby stimulating Akt phosphorylation and cell proliferation. Genistein induces G2/M phase arrest by down-regulating cyclin B1 expression, which is attributable to its suppression of GPR30 activation and Akt phosphorylation in BRCA1 impaired breast cancer cells.

Gross Morphometry, Histomorphometry, and Immunohistochemistry Confirm Early and Persistent Jejunal Crypt Hyperplasia in Poults with Enteritis and Depressed Growth

Phosphorylated histone 3 (PH3) and cleaved caspase 3 (CCASP3) were used to detect proliferating and apoptotic cells, respectively, in the jejunums of female sibling poults, with and without enteritis and depressed growth, from hatch to day 35. Poults that developed enteritis and depressed growth (SIB flock) were raised on a commercial farm in eastern North Carolina, whereas poults with normal growth and no enteritis (TAU flock) were raised in the Teaching Animal Unit at North Carolina State University College of Veterinary Medicine. Beginning on day 5 through day 35 and at processing, TAU poults were significantly heavier than SIB poults. Jejunal weights, relative jejunal weights, and jejunal densities were greater in SIB poults from day 10 through 35. Jejunal efficiency (body weight /jejunal length) was higher in TAU poults at day 5 and days 10 through 35. Mucosal thickness was greater in SIB poults between days 7 and 21 but greater in TAU poults at days 28 and 35. From day 7 to 35, villus-to-crypt ratios were higher for TAU poults and lower for SIB poults because hyperplastic crypts formed a greater percentage of the mucosa in SIB poults. By day 7, PH3- and CCASP3-positive cells were increased in SIB poults, showing that mucosal changes resulted from combined crypt epithelial hyperplasia and increased apoptosis of villous enterocytes. Findings in this study confirm that enteritis, in the absence of clinical signs, and depressed growth in turkey poults begins by day 7, can be identified microscopically, persists for at least 35 days, is associated with lower processing weights, and has a profound negative effect on turkey growth.

Cucurbitacin E inhibits cellular proliferation and enhances the chemo-response in gastric cancer by suppressing AKt activation

Background: The incidence and mortality rate of gastric cancer has markedly declined over the past few decades, due to the progress and advances in the development of diagnostic and treatment regimens. However, there is still a large portion of patients who are first diagnosed during the advanced stage of gastric cancer when chemotherapy is needed. Unfortunately, resistance to chemotherapeutic agents is the most frequent occurrence during treatment, which indicates a need for the discovery of novel therapeutic anticancer drugs. Methods: The tumor-suppression effect of eight different cucurbitacins was evaluated in gastric cancer cell lines, and the Cucurbitacin E (CuE) showing the greatest effect was used in further studies to explore the mechanism and potential synergistic effect of Dox both in vitro and in vivo. Results: Compared with other cucurbitacins, CuE showed the greatest antiproliferative activity against the gastric cancer cell lines. Further investigations revealed that CuE suppressed the growth of gastric cancer cell lines through the induction of G2/M arrest and subsequent apoptosis by impairing AKt activation and reducing its expression in gastric cancer cells. Furthermore, our results indicate that CuE can significantly enhance the cytotoxicity of doxorubicin (Dox) both in vitro and in vivo. Conclusion: In summary, we present the first evidence of the efficacy of CuE for the inhibition of gastric cancer growth and the synergistic antitumorigenic effect of CuE and Dox, both in vitro and in vivo.

Melatonin Abrogates the Anti-Developmental Effect of the AKT Inhibitor SH6 in Bovine Oocytes and Embryos

Melatonin, a nighttime-secreted antioxidant hormone produced by the pineal gland, and AKT, a serine/threonine-specific protein kinase, have been identified as regulators for several cellular processes essential for reproduction. The current study aimed to investigate the potential interplay between melatonin and AKT in bovine oocytes in the context of embryo development. Results showed that the inclusion of SH6, a specific AKT inhibitor, during in vitro maturation (IVM) significantly reduced oocyte maturation, cumulus cell expansion, cleavage, and blastocyst development that were rescued upon addition of melatonin. Oocytes treated with SH6 in the presence of melatonin showed lower levels of reactive oxygen species (ROS) and blastocysts developed exhibited low apoptosis while the mitochondrial profile was significantly improved compared to the SH6-treated group. The RT-qPCR results showed up-regulation of the mRNA of maturation-, mitochondrial-, and cumulus expansion-related genes including GDF-9, BMP-15, MARF1, ATPase, ATP5F1E, POLG2, HAS2, TNFAIP6, and PTGS2 and down-regulation of Bcl-2 associated X apoptosis regulator (BAX), caspase 3, and p21 involved in apoptosis and cell cycle arrest in melatonin-SH6 co-treated group compared to SH6 sole treatment. The immunofluorescence showed high levels of caspase 3 and caspase 9, and low AKT phosphorylation in the SH6-treated group compared to the control and melatonin-SH6 co-treatment. Taken together, our results showed the importance of both melatonin and AKT for overall embryonic developmental processes and, for the first time, we report that melatonin could neutralize the deleterious consequences of AKT inhibition, suggesting a potential role in regulation of AKT signaling in bovine oocytes.

Purinergic signaling in the retina: From development to disease

Retinal injuries and diseases are major causes of human disability involving vision impairment by the progressive and permanent loss of retinal neurons. During development, assembly of this tissue entails a successive and overlapping, signal-regulated engagement of complex events that include proliferation of progenitors, neurogenesis, cell death, neurochemical differentiation and synaptogenesis. During retinal damage, several of these events are re-activated with both protective and detrimental consequences. Purines and pyrimidines, along with their metabolites are emerging as important molecules regulating both retinal development and the tissue's responses to damage. The present review provides an overview of the purinergic signaling in the developing and injured retina. Recent findings on the presence of vesicular and channel-mediated ATP release by retinal and retinal pigment epithelial cells, adenosine synthesis and release, expression of receptors and intracellular signaling pathways activated by purinergic signaling in retinal cells are reported. The pathways by which purinergic receptors modulate retinal cell proliferation, migration and death of retinal cells during development and injury are summarized. The contribution of nucleotides to the self-repair of the injured zebrafish retina is also discussed.

Effects of LY294002 on the function of retinal endothelial cell in vitro

AIM

To study the effects of LY294002 [phosphatidylinositol 3-kinase (PI3K) inhibitor] on the function and mechanisms of retinal endothelial cells (RECs) in vitro.

METHODS

RECs were randomly divided into control group and LY294002 treatment group. RECs in the control group were placed the incubator for hypoxic exposure in vitro. RECs in the LY294002 treatment group were pretreated with LY294002 (40 µmol/L) under hypoxic condition. The expression of matrix metalloproteinase (MMP)-2, MMP-9, vascular endothelial growth factor (VEGF), and apoptosis and proliferation of RECs were evaluated with Western blot, real-time reverse transcription-polymerase chain reaction (RT-PCR), and flow cytometric analysis, correspondently.

RESULTS

Compared with the control group, treating the RECs with LY294002 was able to remarkably inhibit cell proliferation rates (t_1d=2.13, t_2d=2.65, t_3d=2.36, t_4d=2.06, all P<0.05). Flow cytometric analysis indicated that a moderate increase in apoptosis in the LY294002 treatment group compared to the control group (t=2.51, P<0.05). The expression of MMP-2, MMP-9 and VEGF were downregulated in the LY294002 treatment group by Western blot and real-time RT-PCR (all P<0.05).

CONCLUSION

LY294002 regulates the function of RECs by reducing the expression of MMP-2, MMP-9, and VEGF in vitro. LY294002 may provide an effective method for preventing pathological angiogenesis.

Inhibition of LY294002 in retinal neovascularization via down-regulation the PI3K/AKT-VEGF pathway in vivo and in vitro

AIM

To investigate the effects of the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 on retinal neovascularization (RNV) in the oxygen-induced retinopathy (OIR) mouse model and human umbilical vein endothelial cells (HUVECs).

METHODS

C57BL/6J mice were randomly divided into normoxia-control, OIR-control and LY294002 treatment groups. LY294002 or phosphate-buffered solution was intraperitoneally injected daily into mouse pups from P6 to P9 in LY294002 treatment group or OIR-control group. Morphological and pathological changes in RNV, as well as expression levels of PI3K, serine-threonine kinase (AKT) and vascular endothelial growth factor (VEGF) were observed. HUVECs treating with LY294002 were exposed to hypoxia; the expression of PI3K, AKT and VEGF were examined by Western blot and RT-PCR analyses.

RESULTS

Compared with the OIR-control group, LY294002 significantly inhibit RNV. Adenosine diphosphatase (ADPase) staining and hematoxylin and eosin staining indicated that the clock hour scores of neovascularization and the nuclei of pre-retinal neovascular cells in the LY294002 treatment group were clearly less than those in the OIR-control group (1.41±0.52 vs 6.20±1.21; 10.50±1.58 vs 22.25±1.82, both P<0.05). Intravitreal injection of LY294002 (in the LY294002 treatment group) markedly decreased PI3K/AKT-VEGF expression compared with the OIR-control group by immunohistochemistry, Western blotting and RT-PCR (all P<0.05). In HUVECs treated with hypoxia, expression of PI3K, AKT and VEGF were downregulated in the hypoxia-LY294002 group (all P<0.05).

CONCLUSION

The PI3K inhibitor LY294002 can inhibit RNV by downregulating PI3K, AKT, and VEGF expression in vivo and in vitro. LY294002 may provide an effective method for preventing retinopathy of prematurity (ROP).

Functional role of AKT signaling in bovine early embryonic development: potential link to embryotrophic actions of follistatin

BACKGROUND

TGF-β signaling pathways regulate several crucial processes in female reproduction. AKT is a non-SMAD signaling pathway regulated by TGF-β ligands essential for oocyte maturation and early embryonic development in the mouse, but its regulatory role in bovine early embryonic development is not well established. Previously, we demonstrated a stimulatory role for follistatin (a binding protein for specific members of TGF-β superfamily) in early bovine embryonic development. The objectives of the present studies were to determine the functional role of AKT signaling in bovine early embryonic development and embryotrophic actions of follistatin.

METHODS

We used AKT inhibitors III and IV as pharmacological inhibitors of AKT signaling pathway during the first 72 h of in vitro embryo culture. Effects of AKT inhibition on early embryonic development and AKT phosphorylation were investigated in the presence or absence of exogenous follistatin.

RESULTS

Pharmacological inhibition of AKT signaling resulted in a significant reduction in early embryo cleavage, and development to the 8- to 16-cell and blastocyst stages (d7). Treatment with exogenous follistatin increased AKT phosphorylation and rescued the inhibitory effect of AKT inhibitors III and IV on AKT phosphorylation and early embryonic development.

CONCLUSIONS

Collectively, results suggest a potential requirement of AKT for bovine early embryonic development, and suggest a potential role for follistatin in regulation of AKT signaling in early bovine embryos.

Kinases Involved in Both Autophagy and Mitosis

Both mitosis and autophagy are highly regulated dynamic cellular processes and involve various phosphorylation events catalysed by kinases, which play vital roles in almost all physiological and pathological conditions. Mitosis is a key event during the cell cycle, in which the cell divides into two daughter cells. Autophagy is a process in which the cell digests its own cellular contents. Although autophagy regulation has mainly been studied in asynchronous cells, increasing evidence indicates that autophagy is in fact tightly regulated in mitosis. Here in this review, we will discuss kinases that were originally identified to be involved in only one of either mitosis or autophagy, but were later found to participate in both processes, such as CDKs (cyclin-dependent kinases), Aurora kinases, PLK-1 (polo-like kinase 1), BUB1 (budding uninhibited by benzimidazoles 1), MAPKs (mitogen-activated protein kinases), mTORC1 (mechanistic target of rapamycin complex 1), AMPK (AMP-activated protein kinase), PI3K (phosphoinositide-3 kinase) and protein kinase B (AKT). By focusing on kinases involved in both autophagy and mitosis, we will get a more comprehensive understanding about the reciprocal regulation between the two key cellular events, which will also shed light on their related therapeutic investigations.

Andrographolide inhibits prostate cancer by targeting cell cycle regulators, CXCR3 and CXCR7 chemokine receptors

Despite state of the art cancer diagnostics and therapies offered in clinic, prostate cancer (PCa) remains the second leading cause of cancer-related deaths. Hence, more robust therapeutic/preventive regimes are required to combat this lethal disease. In the current study, we have tested the efficacy of Andrographolide (AG), a bioactive diterpenoid isolated from Andrographis paniculata, against PCa. This natural agent selectively affects PCa cell viability in a dose and time-dependent manner, without affecting primary prostate epithelial cells. Furthermore, AG showed differential effect on cell cycle phases in LNCaP, C4-2b and PC3 cells compared to retinoblastoma protein (RB(-/-)) and CDKN2A lacking DU-145 cells. G2/M transition was blocked in LNCaP, C4-2b and PC3 after AG treatment whereas DU-145 cells failed to transit G1/S phase. This difference was primarily due to differential activation of cell cycle regulators in these cell lines. Levels of cyclin A2 after AG treatment increased in all PCa cells line. Cyclin B1 levels increased in LNCaP and PC3, decreased in C4-2b and showed no difference in DU-145 cells after AG treatment. AG decreased cyclin E2 levels only in PC3 and DU-145 cells. It also altered Rb, H3, Wee1 and CDC2 phosphorylation in PCa cells. Intriguingly, AG reduced cell viability and the ability of PCa cells to migrate via modulating CXCL11 and CXCR3 and CXCR7 expression. The significant impact of AG on cellular and molecular processes involved in PCa progression suggests its potential use as a therapeutic and/or preventive agent for PCa.

Reciprocal feedback inhibition of the androgen receptor and PI3K as a novel therapy for castrate-sensitive and -resistant prostate cancer

Gain-of-function of the androgen receptor (AR) and activation of PI3K/AKT/mTOR pathway have been demonstrated to correlate with progression to castration-resistant prostate cancer (CRPC). However, inhibition of AR or PI3K/mTOR alone results in a reciprocal feedback activation. Therefore, we hypothesized that dual inhibition of the AR and PI3K/mTOR pathway might lead to a synergistic inhibition of cell growth and overcome drug resistance in CRPC. Here, we reported that androgen-depletion increased AR protein level and Akt phosphorylation at Ser473 and Thr308 in LNCaP cells. Moreover, we developed resistance cell lines of LNCaP to Enzalutamide (or MDV3100), an AR inhibitor (named as LNCaP ‘MDV-R’) and PF-04691502, a PI3K/mTOR inhibitor (named as LNCaP ‘PF-R’). MTS analysis showed that LNCaP ‘PF-R’ was strongly resistant to Enzalutamide treatment, and on the other hand, LNCaP ‘MDV-R’ was 6-fold resistant to PF-04691502 treatment. Mechanistically, LNCaP ‘MDV-R’ cells had significantly reduced AR, loss of PSA and increase Akt activity in contrast with LNCaP ‘PF-R’ cells. Combined inhibition of PI3K/mTOR and AR pathways with a variety of small molecular inhibitors led to a synergistic suppression of cell proliferation and a profound increase of apoptosis and cell cycle arrest in both androgen-dependent LNCaP and independent CRPC 22Rv1 cell lines. In conclusion, this study provides preclinical proof-of-concept that the combination of a PI3K/mTOR inhibitor with an AR inhibitor results in a synergistic anti-tumor response in non-CRPC and CRPC models.

Adhesion glycoprotein CD44 functions as an upstream regulator of a network connecting ERK, AKT and Hippo-YAP pathways in cancer progression

Targeted therapies are considered to be the future of cancer treatment. However, the mechanism through which intracellular signaling pathways coordinate to modulate oncogenesis remains to be elucidated. In this study, we describe a novel crosstalk among ERK, AKT and Hippo-YAP pathways, with CD44 as an upstream regulator. High cell density leads to activation of ERK and AKT but inactivation of YAP in cancer cells. CD44 modulates cell proliferation and cell cycle but not apoptosis. The expression and activity of cell cycle genes were cooperatively regulated by ERK, AKT and Hippo-YAP signaling pathways through CD44-mediated mechanisms. In addition, CD44 depletion abrogates cancer stem cell properties of tumor initiating cells. Taken together, we described a paradigm where CD44 functions as an upstream regulator sensing the extracellular environment to modulate ERK, AKT and Hippo-YAP pathways which cooperatively control downstream gene expression to modulate cell contact inhibition of proliferation, cell cycle progression and maintenance of tumor initiating cells. Our current study provides valuable information to design targeted therapeutic strategies in cancers.

Curcumin induces autophagy, inhibits proliferation and invasion by downregulating AKT/mTOR signaling pathway in human melanoma cells

Melanoma is the foremost malignant cutaneous cancer and it is extremely resistant to chemotherapy and radiotherapy. Curcumin is an active component of turmeric, the yellow spice derived from the rhizome of Curcuma longa, and is widely known for its anti-inflammatory and anti-cancerogenic properties. Several recent studies suggest that curcumin induces apoptosis by modulating multiple signaling pathways to exert its anticancer effect. In the present study, we investigated the effect of curcumin on the viability, invasion potential, cell cycle, autophagy and the AKT, mTOR, P70S6K proteins of AKT/mTOR signaling pathway in human melanoma A375 and C8161 cell lines in vitro and in an in vivo tumorigenesis model. Curcumin effectively inhibited the proliferation of melanoma cells in vitro and in vivo. It suppressed cell invasion, arrested the cancer cells at G2/M phase of the cell cycle, and induced autophagy. Furthermore, curcumin suppressed the activation of AKT, mTOR and P70S6K proteins. Curcumin, therefore, is a potent suppressor of cell viability and invasion, and simultaneously an inducer of autophagy in A375 and C8161 cells. Accordingly, curcumin could be a novel therapeutic candidate for the management of melanoma.

PF-04691502, a dual PI3K/mTOR inhibitor has potent pre-clinical activity by inducing apoptosis and G1 cell cycle arrest in aggressive B-cell non-Hodgkin lymphomas

The PI3K/Akt/mTOR pathway is activated in a variety of human tumors including B-cell non-Hodgkin lymphoma (B-NHL). Targeting this pathway has been validated in solid and hematological tumors. In the present study, we demonstrated that PF-04691502, a novel PI3K/mTOR inhibitor has potent activity in a panel of aggressive B-NHL cell lines including diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL). MTS analysis showed that PF-04691502 effectively inhibited cell proliferation with IC50 values ranging from 0.12 to 0.55 µM. Cells treated with PF-04691502 exhibited decreased phosphorylation of Akt and S6 ribosomal protein confirming the mechanism of action of a PI3K/mTOR inhibitor. Also, treatment of B-NHL cell lines with PF-04691502 induced apoptosis in a dose- and time-dependent manner. Moreover, PF-04691502 significantly induced G1 cell cycle arrest associated with a decrease in cyclin D1 which contributed to suppression of cell proliferation. Finally, rituximab enhanced apoptosis induced by PF-04691502. Taken together, our findings provide for the first time that PF-04691502 inhibits the constitutively activated PI3K/mTOR pathway in aggressive B-cell NHL cell lines associated with inhibition of cell cycle progression, cell proliferation and promotion of apoptosis. These findings suggest that PF-04691502 is a novel therapeutic strategy in aggressive B-cell NHL and warrants early phase clinical trial evaluation with and without rituximab.

Cadmium promotes the proliferation of triple-negative breast cancer cells through EGFR-mediated cell cycle regulation

Cadmium (Cd) is a carcinogenic metal which is implicated in breast cancer by epidemiological studies. It is reported to promote breast cancer cell growth in vitro through membrane receptors. The study described here examined Cd-mediated growth of non-metastatic human breast cancer derived cells that lack receptors for estrogen, progesterone, and HER2. Treatment of triple-negative HCC 1937 cells with 0.1-0.5 μM Cd increased cell growth by activation of AKT and ERK. Accelerated cell cycle progression was achieved by increasing the levels of cyclins A, B, and E, as well as those of CDKs 1 and 2. Although triple negative cells lack estrogen receptor, they express high levels of EGFR. Therefore, further studies on HCC 1937 and another triple-negative cell line, HCC 38, were conducted using specific siRNA and an inhibitor of EGFR to determine whether EGFR was responsible for mediating the effect of Cd. The results revealed that in both cell types EGFR was not only activated upon Cd treatment, but was also essential for the downstream activation of AKT and ERK. Based on these observations, it is concluded that, in breast cancer cells lacking estrogen receptor, sub-micromolar concentration of Cd can promote cell proliferation. Furthermore, that EGFR plays a critical role in this process.

Involvement of nucleotides in glial growth following scratch injury in avian retinal cell monolayer cultures

When retinal cell cultures were mechanically scratched, cell growth over the empty area was observed. Only dividing and migrating, 2 M6-positive glial cells were detected. Incubation of cultures with apyrase (APY), suramin, or Reactive Blue 2 (RB-2), but not MRS 2179, significantly attenuated the growth of glial cells, suggesting that nucleotide receptors other than P2Y1 are involved in the growth of glial cells. UTPγS but not ADPβS antagonized apyrase-induced growth inhibition in scratched cultures, suggesting the participation of UTP-sensitive receptors. No decrease in proliferating cell nuclear antigen (PCNA(+)) cells was observed at the border of the scratch in apyrase-treated cultures, suggesting that glial proliferation was not affected. In apyrase-treated cultures, glial cytoplasm protrusions were smaller and unstable. Actin filaments were less organized and alfa-tubulin-labeled microtubules were mainly parallel to scratch. In contrast to control cultures, very few vinculin-labeled adhesion sites could be noticed in these cultures. Increased Akt and ERK phosphorylation was observed in UTP-treated cultures, effect that was inhibited by SRC inhibitor 1 and PI3K blocker LY294002. These inhibitors and the FAK inhibitor PF573228 also decreased glial growth over the scratch, suggesting participation of SRC, PI3K, and FAK in UTP-induced growth of glial cells in scratched cultures. RB-2 decreased dissociated glial cell attachment to fibronectin-coated dishes and migration through transwell membranes, suggesting that nucleotides regulated adhesion and migration of glial cells. In conclusion, mechanical scratch of retinal cell cultures induces growth of glial cells over the empty area through a mechanism that is dependent on activation of UTP-sensitive receptors, SRC, PI3K, and FAK.

Role of linker histone H1c during the reprogramming of Chinese swamp buffalo (Bubalus Bubalis) embryos produced by somatic cell nuclear transfer

During reprogramming, there is exchange of histone H1c and the oocyte-specific linker histone, and H1c may play a critically important role in the reprogramming process of somatic cell nuclear transfer (SCNT). The aim of the present study was to investigate the role of the H1c gene in SCNT reprogramming in Chinese swamp buffalo (Bubalus bubalis) using RNA interference (RNAi). Chinese swamp buffalo H1c gene sequences were obtained and H1c-RNAi vectors were designed, synthesised and then transfected into a buffalo fetal skin fibroblast cell line. Expression of H1c was determined by real-time polymerase chain reaction to examine the efficiency of vector interference. These cells were then used as a nuclear donor for SCNT so as to observe the further development of SCNT embryos. Inhibition of H1c gene expression in donor cells significantly improved the developmental speed of embryos from the 1-cell to 8-cell stage. Furthermore, compared with the control group, inhibition of H1c gene expression significantly reduced the blastocyst formation rate. It is concluded that linker histone H1c is very important in SCNT reprogramming in Chinese swamp buffalo. Correct expression of the H1c gene plays a significant role in preimplantation embryonic development in B. bubalis.

Endogenous versus exogenous markers of adult neurogenesis in canaries and other birds: advantages and disadvantages

Although the existence of newborn neurons had originally been suggested, but not broadly accepted, based on studies in adult rodent brains, the presence of an active neurogenesis process in adult homoeothermic vertebrates was first firmly established in songbirds. Adult neurogenesis was initially studied with the tritiated thymidine technique, later replaced by the injection and detection of the marker of DNA replication 5-bromo-2'-deoxyuridine (BrdU). More recently, various endogenous markers were used to identify young neurons or cycling neuronal progenitors. We review here the respective advantages and pitfalls of these different approaches in birds, with specific reference to the microtubule-associated protein, doublecortin (DCX), that has been extensively used to identify young newly born neurons in adult brains. All these techniques of course have limitations. Exogenous markers label cells replicating their DNA only during a brief period and it is difficult to select injection doses that would exhaustively label all these cells without inducing DNA damage that will also result in some form of labeling during repair. On the other hand, specificity of endogenous markers is difficult to establish due to problems related to the specificity of antibodies (these problems can be, but are not always, addressed) and more importantly because it is difficult, if not impossible, to prove that a given marker exhaustively and specifically labels a given cell population. Despite these potential limitations, these endogenous markers and DCX staining in particular clearly represent a useful approach to the detailed study of neurogenesis especially when combined with other techniques such as BrdU.