Cross-talk between mitogenic Ras/MAPK and survival PI3K/Akt pathways: a fine balance. Biochem Soc Trans. 2012;40:139-146. [PMID: 22260680 DOI: 10.1042/BST20110609]

Kaempferol Inhibits Angiogenesis by Suppressing HIF-1α and VEGFR2 Activation via ERK/p38 MAPK and PI3K/Akt/mTOR Signaling Pathways in Endothelial Cells

Kaempferol has been shown to inhibit vascular formation in endothelial cells. However, the underlying mechanisms are not fully understood. In the present study, we evaluated whether kaempferol exerts antiangiogenic effects by targeting extracellular signal-regulated kinase (ERK)/p38 mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/Akt/mechanistic target of rapamycin (mTOR) signaling pathways in endothelial cells. Endothelial cells were treated with various concentrations of kaempferol for 24 h. Cell viability was determined by the 3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay; vascular formation was analyzed by tube formation, wound healing, and mouse aortic ring assays. Activation of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor receptor 2 (VEGFR2), ERK/p38 MAPK, and PI3K/Akt/mTOR was analyzed by Western blotting. Kaempferol significantly inhibited cell migration and tube formation in endothelial cells, and suppressed microvessel sprouting in the mouse aortic ring assay. Moreover, kaempferol suppressed the activation of HIF-1α, VEGFR2, and other markers of ERK/p38 MAPK and PI3K/Akt/mTOR signaling pathways in endothelial cells. These results suggest that kaempferol inhibits angiogenesis by suppressing HIF-1α and VEGFR2 activation via ERK/p38 MAPK and PI3K/Akt/mTOR signaling in endothelial cells.

Activation of Grm1 expression by mutated BRaf (V600E) in vitro and in vivo

Our laboratory previously showed that ectopic expression of Grm1 is sufficient to induce spontaneous melanoma formation with 100% penetrance in transgenic mouse model, TG-3, which harbors wild-type BRaf. Studies identified Grm1 expression in human melanoma cell lines and primary to secondary metastatic melanoma biopsies having wild-type or mutated BRaf, but not in normal melanocytes or benign nevi. Grm1 expression was detected in tissues from mice genetically engineered with inducible melanocyte-specific BRaf^V600E. Additionally, stable clones derived from introduction of exogenous BRaf^V600E in mouse melanocytes also showed Grm1 expression, which was not detected in the parental or empty vector-derived cells, suggesting that expression of BRaf^V600E could activate Grm1 expression. Despite aberrant Grm1 expression in the inducible, melanocyte-specific BRaf^V600E mice, no tumors formed. However, in older mice, the melanocytes underwent senescence, as demonstrated previously by others. It was proposed that upregulated p15 and TGFβ contributed to the senescence phenotype. In contrast, in older TG-3 mice the levels of p15 and TGFβ remained the same or lower. Taken together, these results suggest the temporal regulation on the expression of "oncogenes" such as Grm1 or BRaf^V600E is critical in the future fate of the cells. If BRaf^V600E is turned on first, Grm1 expression can be induced, but this is not sufficient to result in development of melanoma; the cells undergo senescence. In contrast, if ectopic expression of Grm1 is turned on first, then regardless of wild-type or mutated BRaf in the melanocytes melanoma development is the consequence.

Synergistic anticancer activity of 20(S)-Ginsenoside Rg3 and Sorafenib in hepatocellular carcinoma by modulating PTEN/Akt signaling pathway

Sorafenib, a multikinase inhibitor for hepatocellular carcinoma treatment, inhibits the Raf/MAPK/ERK signaling pathway. However, PI3K/Akt signaling pathway is activated by Sorafenib and cross-talks with the Raf/MAPK/ERK signaling pathway, leading to drug resistance. 20(S)-Ginsenoside Rg3 has been reported with significant anticancer effect to numerous carcinomas by inhibition of PI3K-Akt signaling pathway. Hence, we aim to examine the synergistic anticancer activity of 20(S)-Ginsenoside Rg3 and Sorafenib via modulation of PTEN/Akt signaling pathway. Human hepatocellular carcinoma cell lines HepG2 and Huh7 were used. Cell viability, clonogenic assay, apoptosis assay, western blot analysis, xenograft treatment and immunohistochemistry were carried out. The viability of hepatocellular carcinoma cells significantly decreased by the treatment of Sorafenib combined with 20(S)-Ginsenoside Rg3, as well as the enhanced apoptotic rates. The levels of PTEN, Bax and cleaved caspase-3 expression increased, while the levels of phospho-PDK1 and phospho-Akt expression decreased by the treatment of Sorafenib combined with 20(S)-Ginsenoside Rg3. In vivo, the tumor volumes and weight decreased in the Sorafenib combined with 20(S)-Ginsenoside Rg3 group. The results demonstrated the synergistic anticancer activity of 20(S)-Ginsenoside Rg3 and Sorafenib in HCC by modulating PTEN/Akt signaling pathway. These findings suggest a promising strategy for HCC treatment, which could be performed in a sufficiently frequent manner.

Phosphoproteomics reveals network rewiring to a pro-adhesion state in annexin-1-deficient mammary epithelial cells

Background

Annexin-1 (ANXA1) plays pivotal roles in regulating various physiological processes including inflammation, proliferation and apoptosis, and deregulation of ANXA1 functions has been associated with tumorigenesis and metastasis events in several types of cancer. Though ANXA1 levels correlate with breast cancer disease status and outcome, its distinct functional involvement in breast cancer initiation and progression remains unclear. We hypothesized that ANXA1-responsive kinase signaling alteration and associated phosphorylation signaling underlie early events in breast cancer initiation events and hence profiled ANXA1-dependent phosphorylation changes in mammary gland epithelial cells.

Methods

Quantitative phosphoproteomics analysis of mammary gland epithelial cells derived from ANXA1-heterozygous and ANXA1-deficient mice was carried out using stable isotope labeling with amino acids in cell culture (SILAC)-based mass spectrometry. Kinase and signaling changes underlying ANXA1 perturbations were derived by upstream kinase prediction and integrated network analysis of altered proteins and phosphoproteins.

Results

We identified a total of 8110 unique phosphorylation sites, of which 582 phosphorylation sites on 372 proteins had ANXA1-responsive changes. A majority of these phosphorylation changes occurred on proteins associated with cytoskeletal reorganization spanning the focal adhesion, stress fibers, and also the microtubule network proposing new roles for ANXA1 in regulating microtubule dynamics. Comparative analysis of regulated global proteome and phosphoproteome highlighted key differences in translational and post-translational effects of ANXA1, and suggested closely coordinated rewiring of the cell adhesion network. Kinase prediction analysis suggested activity modulation of calmodulin-dependent protein kinase II (CAMK2), P21-activated kinase (PAK), extracellular signal-regulated kinase (ERK), and IκB kinase (IKK) upon loss of ANXA1. Integrative analysis revealed regulation of the WNT and Hippo signaling pathways in ANXA1-deficient mammary epithelial cells, wherein there is downregulation of transcriptional effects of TEA domain family (TEAD) suggestive of ANXA1-responsive transcriptional rewiring.

Conclusions

The phosphoproteome landscape uncovered several novel perspectives for ANXA1 in mammary gland biology and highlighted its involvement in key signaling pathways modulating cell adhesion and migration that could contribute to breast cancer initiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0924-4) contains supplementary material, which is available to authorized users.

The stem cell factor (SCF)/c-KIT signalling in testis and prostate cancer

The stem cell factor (SCF) is a cytokine that specifically binds the tyrosine kinase receptor c-KIT. The SCF/c-KIT interaction leads to receptor dimerization, activation of kinase activity and initiation of several signal transduction pathways that control cell proliferation, apoptosis, differentiation and migration in several tissues. The activity of SCF/c-KIT system is linked with the phosphatidylinositol 3-kinase (PI3-K), the Src, the Janus kinase/signal transducers and activators of transcription (JAK/STAT), the phospholipase-C (PLC-γ) and the mitogen-activated protein kinase (MAPK) pathways. Moreover, it has been reported that cancer cases display an overactivation of c-KIT due to the presence of gain-of-function mutations or receptor overexpression, which renders c-KIT a tempting target for cancer treatment. In the case of male cancers the most documented activated pathways are the PI3-K and Src, both enhancing abnormal cell proliferation. It is also known that the Src activity in prostate cancer cases depends on the presence of tr-KIT, the cytoplasmic truncated variant of c-KIT that is specifically expressed in tumour tissues and, thus, a very interesting target for drug development. The present review provides an overview of the signalling pathways activated by SCF/c-KIT and discusses the potential application of c-KIT inhibitors for treatment of testicular and prostatic cancers.

Lonicera japonica Thunb. Induces caspase-dependent apoptosis through death receptors and suppression of AKT in U937 human leukemic cells

Decoctions obtained from the dried flowers of Lonicera japonica Thunb. (Indongcho) have been utilized in folk remedies against inflammatory diseases. Recently, many agents that have used for inflammatory diseases are showing anticancer effects. Here, we have isolated polyphenols extracted from lyophilized Lonicera japonica Thunb (PELJ) and investigated the anticancer effects of PELJ on U937 cells. Here, we demonstrated that PELJ induced apoptosis by upregulation of DR4 and Fas, and further it is augmented by suppression of XIAP. In addition, The PELJ-induced apoptosis is at least in part by blocking PI3K/Akt pathway. These findings suggest that PELJ may provide evidence of anticancer activities on U937 cells. Further study for detailed mechanism and the effects on animal models is warranted to determine whether PELJ provide more conclusive evidence that PELJ which may provide a beneficial effect for treating cancer.

In vitro characterization of spheres derived from colorectal cancer cell lines

Spherical cultures (SCs) can be regarded in cancer research as a link between in vitro investigations on cancer lines and in vivo studies of tumor development. SCs are believed to mimic tumor architecture and to be enriched in cancer stem cell-like cells (CSC-like cells). In the present study we characterized colonospheres derived from colorectal cancer (CRC) cell lines, and we confirmed the ability of HCT116 and HT29 cell lines to form spheres within serum-free medium, however, the detailed analysis presented the major differences concerning their characteristics including morphology, phenotype, proliferative potential, distribution in the cell cycle phases and spherogenicity. Moreover, after we magnetically separated CD133+ and CD133- cells we could conduct the analogical analysis as we performed for the original cells. We observed that all cellular fractions unveiled sphere formation capacity, even when cultured in limited number of cells per well and only SCs originated from CD133+ fraction resembled morphologically the parental spheres. Both CD133+ and CD133- subsets derived from HCT116 line were more enriched in cells in G0/G1 phase of the cell cycle in comparison to their HT29 analogues. Additionally, proliferative potential also varied amongst all studied fractions. Surprisingly, 3-D invasion assay revealed that only HCT116-derived populations were able to migrate into extended regions of Matrigel Matrix confirming their higher aggressiveness. Our results provided comprehensive characterization of CRC cell lines culture in adherent and spherical forms and, what seems to be the most advantageous, the comparison of two distinct fractions after magnetic separation. As we found the specific features of cells presented line- and expansion mode-dependency, thus, such complete description might appear crucial before CRC lines would be involved into sophisticated assays, especially focused on potentially novel therapeutic agents targeting CSC-like cells.

Association between integrin-linked kinase and hyperthermia in oral squamous cell carcinoma

The present study aimed to observe the effect of the biological functions of integrin-linked kinase (ILK) silencing combined with hyperthermia on Tca8113 cells. Lentivirus-mediated short hairpin RNA (shRNA)-targeting ILK was transfected into oral squamous cell carcinoma (OSCC) Tca8113 cells and, combined with hyperthermia, several experimental methods were used to detect their biological behavior in vitro. On the basis of in vitro experiments, Tca8113 cells were transplanted into nude mice models, and ILK-shRNA-lentivirus was injected into the nude mice transplanted tumor and combined with hyperthermia. Tumor morphology and the associated protein expression changes were determined. Subsequent to ILK silencing combined with hyperthermia, the growth, migration and proliferation of Tca8113 cells were significantly inhibited. Flow cytometry revealed that the cells were blocked in the S phase, and western blot analysis demonstrated that ILK, phosphorylated (p)-RAC-alpha serine/threonine-protein kinase (Akt), p-glycogen synthase kinase-3β and p-heat shock factor 1 protein expression levels were significantly decreased, while apoptosis-associated protein B-cell lymphoma-2-associated X protein expression and the efficacy of hypothermia were significantly increased. By ILK silencing combined with hyperthermia, a significant therapeutic effect on transplanted tumors was observed in nude mice. Immunohistochemistry revealed the same results as the in vitro experiments. ILK silencing combined with hyperthermia can inhibit the growth, proliferation and migration of Tca8113 cells, promote Tca8113 cell apoptosis, inhibit the phosphatidylinositol-3-kinase/Akt signaling pathway and increase hyperthermia sensitivity; the combination therapy exhibits a synergistic sensitizing effect. Therefore, ILK silencing combined with hypothermia may serve as a novel combination therapy strategy against OSCC.

Phase I clinical trials in patients with advanced non-small cell lung cancer treated within a Drug Development Unit: What have we learnt?

OBJECTIVES

Despite advances in novel drug development for patients with advanced non-small cell lung cancer (NSCLC), there are still only a limited number of approved treatments. We therefore evaluated the clinical outcomes of patients with advanced NSCLC referred to a dedicated phase I clinical trials unit assessed baseline clinical factors associated with successful enrollment onto phase I trials.

MATERIAL AND METHODS

We conducted a retrospective study involving patients with advanced NSCLC referred to the Drug Development Unit at the RMH between January 2005 and December 2013.

RESULTS

257 patients with advanced NSCLC were referred for consideration of phase I trials, of which only 89 (35%) patients successfully commenced phase I trials. The commonest reasons for not entering study included poor ECOG performance status and rapid disease progression. A multivariate analysis identified that ECOG performance status (0-1) and RMH prognostic score (0-1) were associated with successful enrollment onto phase I trials (p<0.001). Single agent therapies included novel agents against the phosphatidylinositol-3 kinase pathway, insulin growth factor-1 receptor and pan-HER family tyrosine kinases. These trial therapies were well tolerated and mainly associated with grade 1-2 adverse events, with a minority experiencing grade 3 toxicities. Nine (10%) patients, 4 with known EGFR or KRAS mutations, achieved RECIST partial responses. Median time to progression was 2.6 months and median overall survival was 8.1 months for patients enrolled.

CONCLUSIONS

Phase I trial therapies were generally well tolerated with potential antitumor benefit for patients with advanced NSCLC. Early referral to drug development units at time of disease progression should be considered to enhance the odds of patient participation in these studies.

Periostin promotes migration and osteogenic differentiation of human periodontal ligament mesenchymal stem cells via the Jun amino-terminal kinases (JNK) pathway under inflammatory conditions

OBJECTIVES

Mesenchymal stem cell (MSC)-mediated periodontal tissue regeneration is considered to be a promising method for periodontitis treatment. The molecular mechanism of functional regulation by MSCs remains unclear, thus limiting their application. Our previous study discovered that Periostin (POSTN) promoted the migration and osteogenic differentiation of periodontal ligament mesenchymal stem cells (PDLSCs), but it is still unclear whether POSTN is able to restore the regenerative potential of PDLSCs under inflammatory conditions. In this study, we investigated the effect of POSTN on PDLSCs under inflammatory conditions and its mechanism.

MATERIALS AND METHODS

PDLSCs were isolated from periodontal ligament tissue. TNF-α was used at 10 ng/mL to mimic inflammatory conditions. Lentivirus POSTN shRNA was used to knock down POSTN. Recombinant human POSTN (rhPOSTN) was used to stimulate PDLSCs. A scratch assay was used to analyse cell migration. Alkaline phosphatase (ALP) activity, Alizarin Red staining and expression of osteogenesis-related genes were used to investigate the osteogenic differentiation potential. Western blot analysis was used to detect the mitogen-activated protein kinases (MAPK) and AKT signalling pathways.

RESULTS

After a 10 ng/mL TNF-α treatment, knockdown of POSTN impeded scratch closure, inhibited ALP activity and mineralization in vitro, and decreased expression of RUNX2, OSX, OPN and OCN in PDLSCs, while 75 ng/mL rhPOSTN significantly accelerated scratch closure, enhanced ALP activity and mineralization in vitro, and increased expression of RUNX2, OSX, OPN and OCN. In addition, knockdown of POSTN inhibited expression of phosphorylated c-Jun N-terminal kinase (p-JNK), while 75 ng/mL rhPOSTN increased expression of p-JNK in PDLSCs with TNF-α treatment. Furthermore, inhibition of JNK by its inhibitor SP600125 dramatically blocked POSTN-enhanced scratch closure, ALP activity and mineralization in PDLSCs.

CONCLUSIONS

Our results revealed that POSTN might promote the migration and osteogenic differentiation potential of PDLSCs via the JNK pathway, providing insight into the mechanism underlying MSC biology under inflammatory conditions and identifying a potential target for improving periodontal tissue regeneration.

Brief Report: A Differential Transcriptomic Profile of Ex Vivo Expanded Adult Human Hematopoietic Stem Cells Empowers Them for Engraftment Better than Their Surface Phenotype

Transplantation of small cord blood (CB) units, or of autologous ex vivo‐genetically modified adult hematopoietic stem cells (HSC), face the common challenge of suboptimal HSC doses for infusion and impaired engraftment of the transplanted cells. Ex vivo expansion of HSCs, using either cell‐based coculture approaches or especially small molecules have been successfully tested mainly in CB and in prolonged cultures. Here, we explored whether innovative combinations of small molecules can sufficiently, after short culture, expand adult HSCs while retaining their functionality in vivo. We found that 5‐day cultured cells, in the presence of the small molecule combinations tested, achieved higher engraftment levels in NSG mice than both their uncultured and their cytokine only‐cultured counterparts. Surprisingly, the engraftment levels were neither concordant to the numbers of phenotypically similar HSCs expanded under different small molecule combinations, nor explained by their distinct companion cells present. Transcriptomic comparative analysis of sorted, phenotypically similar, ex vivo generated HSCs transplanted in equal numbers, suggested that HSCs generated under expansion conditions that maintain low expression of the Rap1/Ras/PI3K‐AKT pathway exhibit a superior functional profile in vivo. Stem Cells Translational Medicine2017;6:1852–1858

Structure-Guided Design and Initial Studies of a Bifunctional MEK/PI3K Inhibitor (ST-168)

The structure-based design of a new single entity, MEK/PI3K bifunctional inhibitor (7, ST-168), which displays improved MEK1 and PI3K isoform inhibition, is described. ST-168 demonstrated a 2.2-fold improvement in MEK1 inhibition and a 2.8-, 2.7-, 23-, and 2.5-fold improved inhibition toward the PI3Kα, PI3Kβ, PI3Kδ, and PI3Kγ isoforms, respectively, as compared to a previous lead compound (4; ST-162) in in vitro enzymatic inhibition assays. ST-168 demonstrated superior tumoricidal efficacy over ST-162 in an A375 melanoma spheroid tumor model. ST-168 was comparatively more effective than ST-162 in promoting tumor control when administrated orally in a tumor therapy study conducted in an A375 melanoma mouse model confirming its bioavailability and efficacy toward combined in vivo MEK1/PI3K inhibition.

Tetrahydrocurcumin induces mesenchymal-epithelial transition and suppresses angiogenesis by targeting HIF-1α and autophagy in human osteosarcoma

Human osteosarcoma is considered a malignant tumor with poor prognosis that readily metastasizes. Tetrahydrocurcumin (THC) has been reported to have anti-tumor activity in numerous tumors. In addition, hypoxia-inducible factor-1α (HIF-1α) has been demonstrated to be associated with tumor metastasis by regulating epithelial-mesenchymal transition (EMT). However, the role of THC in osteosarcoma remains uncertain. Therefore, this study aimed to elucidate the potential mechanisms. We found that THC significantly reduced the growth of osteosarcoma cells and suppressed migration and invasion, as tested in a nude mouse lung metastasis model. Additionally, the mesenchymal-epithelial transition (MET) process was facilitated by THC. Mechanistically, our study showed that HIF-1α had a pivotal role in the anti-metastatic effect of THC. Importantly, HIF-1α expression was downregulated by THC by inhibiting Akt/mTOR and p38 MAPK pathways. Moreover, THC exhibited a remarkable inhibitory effect on HIF-1α expression and angiogenesis under hypoxic conditions. Furthermore, THC activated autophagy and induced MET and suppressed angiogenesis in a HIF-1α-related manner. Taken together, our findings suggest that THC suppresses metastasis and invasion and this may be associated with HIF-1α and autophagy, which would potentially provide therapeutic strategies for human osteosarcoma.

A Bifunctional MAPK/PI3K Antagonist for Inhibition of Tumor Growth and Metastasis

Responses to targeted therapies frequently are brief, with patients relapsing with drug-resistant tumors. For oncogenic MEK and BRAF inhibition, drug resistance commonly occurs through activation of PI3K/AKT/mTOR signaling and immune checkpoint modulation, providing a robust molecular target for concomitant therapy. Here, we evaluated the efficacy of a bifunctional kinase inhibitor (ST-162) that concurrently targets MAPK and PI3K signaling pathways. Treatment with ST-162 produced regression of mutant KRAS- or BRAF-addicted xenograft models of colorectal cancer and melanoma and stasis of BRAF/PTEN-mutant melanomas. Combining ST-162 with immune checkpoint blockers further increased efficacy in a syngeneic KRAS-mutant colorectal cancer model. Nascent transcriptome analysis revealed a unique gene set regulated by ST-162 related to melanoma metastasis. Subsequent mouse studies revealed ST-162 was a potent inhibitor of melanoma metastasis to the liver. These findings highlight the significant potential of a single molecule with multikinase activity to achieve tumor control, overcome resistance, and prevent metastases through modulation of interconnected cell signaling pathways. Mol Cancer Ther; 16(11); 2340-50. ©2017 AACR.

Inflammatory mediator ultra-low-molecular-weight hyaluronan triggers necrosis of B-precursor leukemia cells with high surface CD44 expression

Acute lymphoblastic leukemia (ALL) with mixed lineage leukemia (MLL) gene rearrangements (MLL+ALL) has a dismal prognosis and is characterized by high surface CD44 expression. Known that CD44 has the specific binding sites for a natural ligand hyaluronan (HA), we investigated biological effects of HA with different molecular sizes on MLL+ALL cell lines, and found that the addition of ultra-low-molecular-weight (ULMW)-HA strongly suppressed their thymidine uptakes. The MLL+ALL cell line lacking surface CD44 expression established by genome editing showed no suppression of thymidine uptake. Surface CD44-high B-precursor ALL cell lines other than MLL+, but not T-ALL cell lines, were also suppressed in their thymidine uptakes. The inhibition of thymidine uptakes was because of induction of cell death, but dead cells lacked features of apoptosis on cytospin smears and flow cytometric analysis. The cell death was neither blocked by pan-caspase inhibitor nor autophagy inhibitor, but was completely blocked by necrosis inhibitor necrostatin-1. Necrotic cell death was further supported by a marked release of a high-mobility protein group B1 and morphological changes on transmission electron microscopy. Elevation of intracellular reactive oxygen species production suggested a role for inducing this necrotic cell death. ULMW-HA-triggered cell death was similarly demonstrated in surface CD44-high primary B-precursor leukemia cells. Assuming that ULMW-HA is abundantly secreted at the site of infection and inflammation, this study sheds light on understanding the mechanism of a transient inflammation-associated remission of leukemia. Further, the CD44-targeting may become an effective approach in future for the treatment of refractory B-precursor ALL by its capability of predominantly eradicating CD44-high leukemia-initiating cells.

Zeylenone, a naturally occurring cyclohexene oxide, inhibits proliferation and induces apoptosis in cervical carcinoma cells via PI3K/AKT/mTOR and MAPK/ERK pathways

There is a strong rationale to therapeutically target the PI3K/Akt/mTOR and MAPK/ERK pathways in cervical carcinoma since they are highly deregulated in this disease. Previous study by our group have demonstrated that Zeylenone (Zey) exhibited strong suppressive activity on PI3K/AKT/mTOR and MAPK/ERK signaling, providing a foundation to investigate its antitumor activity in cervical carcinoma. Herein, the present study aimed to investigate suppressive effect of Zey on HeLa and CaSki cells, and further explore the underlying mechanisms. Cells were treated with Zey for indicated time, followed by measuring its effects on cell viability, colony formation, cell cycle, cell apoptosis, and signal pathways. In vivo antitumor activity of Zey was then assessed with nude xenografts. We found that Zey substantially suppressed cell proliferation, induced cell cycle arrest, and increased cell apoptosis, accompanied by increased production of ROS, decreased mitochondrial membrane potential, activated caspase apoptotic cascade, and attenuated PI3K/Akt/mTOR and MAPK/ERK pathways. Additionally, in vivo experiments showed that Zey exerted good antitumor efficacy against HeLa bearing mice models via decreasing levels of p-PI3K and p-ERK. Collectively, these data clearly demonstrated the antitumor activity of Zey in cervical carcinoma cells, which is most likely via the regulation of PI3K/Akt/mTOR and MAPK/ERK pathways.

Regulation of the PI3K/Akt pathway during decidualization of endometrial stromal cells

Infertility is constantly increasing in Canada, where 16% of Canadian couples are experiencing difficulty conceiving. It is thought that infertility can emanate from the dysregulated communication between the embryo and the maternal endometrium. In order to allow for this window of implantation to be open at the right moment, endometrial stromal cells proliferate and differentiate by a mechanism called decidualization. Intracellular and molecular mechanisms involved in the regulation of apoptosis and cell proliferation during decidualization of the endometrium are yet to be fully understood. It has been well demonstrated previously that Akt is importantly involved in cell survival and glycogen synthesis. Akt1, Akt2 and Akt3 isoforms have distinct physiological roles; this could also be the case during decidualization and pregnancy. The aim of this study is to investigate the regulation of PI3K/Akt pathway during the decidualization process of endometrial stromal cells. Expression of Akt isoforms, Akt activity (phospho-Akt), pIκB and substrates of Akt during decidualization were measured. To our knowledge, these results are the first to suggest a decrease in levels of Akt isoforms as well as a downregulation of Akt activity in the process of decidualization of human endometrial stromal cells. We also uncovered that decidualization induced nuclear localization of p65 through the phosphorylation of IκB, its inhibitory subunit; however, Par-4, a recently uncovered regulator of cell differentiation, was displaced from the nucleus upon decidualization. Our results also suggest that HIESC cells exhibit decreased motility during decidualization and that PI3K pathway inhibition could be involved in this process. Finally, we demonstrate that specific Akt isoforms present unique effects on the successful induction of decidualization. Further analyses will involve investigations to understand the precise signaling mechanisms by which this pathway is regulated.

An immediate-late gene expression module decodes ERK signal duration

The RAF‐MEK‐ERK signalling pathway controls fundamental, often opposing cellular processes such as proliferation and apoptosis. Signal duration has been identified to play a decisive role in these cell fate decisions. However, it remains unclear how the different early and late responding gene expression modules can discriminate short and long signals. We obtained both protein phosphorylation and gene expression time course data from HEK293 cells carrying an inducible construct of the proto‐oncogene RAF. By mathematical modelling, we identified a new gene expression module of immediate–late genes (ILGs) distinct in gene expression dynamics and function. We find that mRNA longevity enables these ILGs to respond late and thus translate ERK signal duration into response amplitude. Despite their late response, their GC‐rich promoter structure suggested and metabolic labelling with 4SU confirmed that transcription of ILGs is induced immediately. A comparative analysis shows that the principle of duration decoding is conserved in PC12 cells and MCF7 cells, two paradigm cell systems for ERK signal duration. Altogether, our findings suggest that ILGs function as a gene expression module to decode ERK signal duration.

Growth and stress response mechanisms underlying post-feeding regenerative organ growth in the Burmese python

Background

Previous studies examining post-feeding organ regeneration in the Burmese python (Python molurus bivittatus) have identified thousands of genes that are significantly differentially regulated during this process. However, substantial gaps remain in our understanding of coherent mechanisms and specific growth pathways that underlie these rapid and extensive shifts in organ form and function. Here we addressed these gaps by comparing gene expression in the Burmese python heart, liver, kidney, and small intestine across pre- and post-feeding time points (fasted, one day post-feeding, and four days post-feeding), and by conducting detailed analyses of molecular pathways and predictions of upstream regulatory molecules across these organ systems.

Results

Identified enriched canonical pathways and upstream regulators indicate that while downstream transcriptional responses are fairly tissue specific, a suite of core pathways and upstream regulator molecules are shared among responsive tissues. Pathways such as mTOR signaling, PPAR/LXR/RXR signaling, and NRF2-mediated oxidative stress response are significantly differentially regulated in multiple tissues, indicative of cell growth and proliferation along with coordinated cell-protective stress responses. Upstream regulatory molecule analyses identify multiple growth factors, kinase receptors, and transmembrane receptors, both within individual organs and across separate tissues. Downstream transcription factors MYC and SREBF are induced in all tissues.

Conclusions

These results suggest that largely divergent patterns of post-feeding gene regulation across tissues are mediated by a core set of higher-level signaling molecules. Consistent enrichment of the NRF2-mediated oxidative stress response indicates this pathway may be particularly important in mediating cellular stress during such extreme regenerative growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3743-1) contains supplementary material, which is available to authorized users.

Salinomycin: A new paradigm in cancer therapy

The primary hurdle in the treatment of cancer is acquisition of resistance by the tumor cells toward multiple drugs and selectively targeting the cancer stem cells. This problem was overcome by the chemotherapeutic property of recently discovered drug salinomycin. Exact mechanism of action of salinomycin is not yet known, but there are multiple pathways by which salinomycin inhibits tumor growth. Salinomycin decreases the expression of adenosine triphosphate-binding cassette transporter in multidrug resistance cells and interferes with Akt signaling pathway, Wnt/β-catenin, Hedgehog, and Notch pathways of cancer progression. Salinomycin selectively targets cancer stem cells. The potential of salinomycin to eliminate both cancer stem cells and therapy-resistant cancer cells may characterize the compound as a novel and an efficient chemotherapeutic drug.

Tetraarsenic hexoxide induces G2/M arrest, apoptosis, and autophagy via PI3K/Akt suppression and p38 MAPK activation in SW620 human colon cancer cells

Tetraarsenic hexoxide (As₄O₆₎ has been used in Korean folk medicines for the treatment of cancer, however its anti-cancer mechanisms remain obscured. Here, this study investigated the anti-cancer effect of As₄O₆ on SW620 human colon cancer cells. As₄O₆ has showed a dose-dependent inhibition of SW620 cells proliferation. As₄O₆ significantly increased the sub-G1 and G2/M phase population, and Annexin V-positive cells in a dose-dependent manner. G2/M arrest was concomitant with augment of p21 and reduction in cyclin B1, cell division cycle 2 (cdc 2) expressions. Nuclear condensation, cleaved nuclei and poly (adenosine diphosphate‑ribose) polymerase (PARP) activation were also observed in As₄O₆-treated SW620 cells. As₄O₆ induced depolarization of mitochondrial membrane potential (MMP, ΔΨm) but not reactive oxygen species (ROS) generation. Further, As₄O₆ increased death receptor 5 (DR5), not DR4 and suppressed the B‑cell lymphoma‑2 (Bcl-2) and X-linked inhibitor of apoptosis protein (XIAP) family proteins. As₄O₆ increased the formation of AVOs (lysosomes and autophagolysosomes) and promoted the conversion of microtubule-associated protein 1A/1B-light chain 3 (LC3)-I to LC3-II in a dose- and time- dependent manner. Interestingly, a specific phosphoinositide 3-kinase (PI3K)/Akt inhibitor (LY294002) augmented the As₄O₆ induced cell death; whereas p38 mitogen-activated protein kinases (p38 MAPK) inhibitor (SB203580) abrogated the cell death. Thus, the present study provides the first evidence that As₄O₆ induced G2/M arrest, apoptosis and autophagic cell death through PI3K/Akt and p38 MAPK pathways alteration in SW620 cells.

EGFR signaling pathways are wired differently in normal 184A1L5 human mammary epithelial and MDA-MB-231 breast cancer cells

Because of differences in the downstream signaling patterns of its pathways, the role of the human epidermal growth factor family of receptors (HER) in promoting cell growth and survival is cell line and context dependent. Using two model cell lines, we have studied how the regulatory interaction network among the key proteins of HER signaling pathways may be rewired upon normal to cancerous transformation. We in particular investigated how the transcription factor STAT3 and several key kinases' involvement in cancer-related signaling processes differ between normal 184A1L5 human mammary epithelial (HME) and MDA-MB-231 breast cancer epithelial cells. Comparison of the responses in these cells showed that normal-to-cancerous cellular transformation causes a major re-wiring of the growth factor initiated signaling. In particular, we found that: i) regulatory interactions between Erk, p38, JNK and STAT3 are triangulated and tightly coupled in 184A1L5 HME cells, and ii) STAT3 is only weakly associated with the Erk-p38-JNK pathway in MDA-MB-231 cells. Utilizing the concept of pathway substitution, we predicted how the observed differences in the regulatory interactions may affect the proliferation/survival and motility responses of the 184A1L5 and MDA-MB-231 cells when exposed to various inhibitors. We then validated our predictions experimentally to complete the experiment-computation-experiment iteration loop. Validated differences in the regulatory interactions of the 184A1L5 and MDA-MB-231 cells indicated that instead of inhibiting STAT3, which has severe toxic side effects, simultaneous inhibition of JNK together with Erk or p38 could be a more effective strategy to impose cell death selectively to MDA-MB-231 cancer cells while considerably lowering the side effects to normal epithelial cells. Presented analysis establishes a framework with examples that would enable cell signaling researchers to identify the signaling network structures which can be used to predict the phenotypic responses in particular cell lines of interest.

7α-Hydroxycholesterol induces monocyte/macrophage cell expression of interleukin-8 via C5a receptor

We investigated effects of 7-oxygenated cholesterol derivatives present in atherosclerotic lesions, 7α-hydroxycholesterol (7αOHChol), 7β-hydroxycholesterol (7βOHChol), and 7-ketocholesterol (7K), on IL-8 expression. Transcript levels of IL-8 and secretion of its corresponding gene product by monocytes/macrophages were enhanced by treatment with 7αOHChol and, to a lesser extent, 7K, but not by 7βOHChol. The 7-oxygenated cholesterol derivatives, however, did not change transcription of the IL-8 gene in vascular smooth muscle cells. 7αOHChol-induced IL-8 gene transcription was inhibited by cycloheximide and Akt1 downregulation, but not by OxPAPC. Expression of C5a receptor was upregulated after stimulation with 7αOHChol, but not with 7K and 7βOHChol, and a specific antagonist of C5a receptor inhibited 7αOHChol-induced IL-8 gene expression in a dose dependent manner. Pharmacological inhibitors of PI3K and MEK almost completely inhibited expression of both IL-8 and cell-surface C5a receptor induced by 7αOHChol. These results indicate that 7-oxygenated cholesterol derivatives have differential effects on monocyte/macrophage expression of IL-8 and C5a receptor and that C5a receptor is involved in 7αOHChol-induced IL-8 expression via PI3K and MEK.

PINTnet: construction of condition-specific pathway interaction network by computing shortest paths on weighted PPI

Background

Identifying perturbed pathways in a given condition is crucial in understanding biological phenomena. In addition to identifying perturbed pathways individually, pathway analysis should consider interactions among pathways. Currently available pathway interaction prediction methods are based on the existence of overlapping genes between pathways, protein-protein interaction (PPI) or functional similarities. However, these approaches just consider the pathways as a set of genes, thus they do not take account of topological features. In addition, most of the existing approaches do not handle the explicit gene expression quantity information that is routinely measured by RNA-sequecing.

Results

To overcome these technical issues, we developed a new pathway interaction network construction method using PPI, closeness centrality and shortest paths. We tested our approach on three different high-throughput RNA-seq data sets: pregnant mice data to reveal the role of serotonin on beta cell mass, bone-metastatic breast cancer data and autoimmune thyroiditis data to study the role of IFN- α. Our approach successfully identified the pathways reported in the original papers. For the pathways that are not directly mentioned in the original papers, we were able to find evidences of pathway interactions by the literature search. Our method outperformed two existing approaches, overlapping gene-based approach (OGB) and protein-protein interaction-based approach (PB), in experiments with the three data sets.

Conclusion

Our results show that PINTnet successfully identified condition-specific perturbed pathways and the interactions between the pathways. We believe that our method will be very useful in characterizing biological mechanisms at the pathway level. PINTnet is available at http://biohealth.snu.ac.kr/software/PINTnet/.

Dual inhibition of Akt and c-Met as a second-line therapy following acquired resistance to sorafenib in hepatocellular carcinoma cells

Sorafenib displays a limited efficacy for advanced hepatocellular carcinoma (HCC). Some patients with HCC initially respond to sorafenib, but eventually succumb to the disease, indicating that the acquired resistance to sorafenib reduces its beneficial effects. No alternative drugs are available after the failure of sorafenib therapy. Therefore, investigation of the mechanisms underlying the acquired resistance and development of second-line treatments for sorafenib-resistant HCC are urgently required. In this study, sorafenib-resistant HCC cells generated from sorafenib-sensitive human HCC cells were shown to overproduce hepatocyte growth factor (HGF) and overexpress c-Met kinase and its phosphorylated form, leading to the activation of Akt and ERK (extracellular signaling-regulated kinase) pathways. Use of specific c-Met inhibitors enhanced the effects of sorafenib by inhibiting the growth of sorafenib-resistant HCC cells. Akt inhibitors, a class of second-line therapeutic drugs under investigation for treating HCC in clinical trials, enhanced the effects of sorafenib, but also activated the c-Met pathway in sorafenib-resistant cells. Dual inhibition of Akt and c-Met by their respective inhibitors, MK2206 and capmatinib, additively or synergistically suppressed sorafenib-resistant HCC cells in vitro and sorafenib-resistant HCC xenografts in mice. The anticancer activities of MK2206 mainly rely on its ability to induce cell apoptosis and autophagic death, while capmatinib treatment leads to cell cycle arrest at phase G1. These results provide strong evidence for further investigation on the clinical utility of dual inhibition of Akt and c-Met, particularly MK2206 and capmatinib, as a second-line therapy for advanced HCC that has acquired resistance to sorafenib.

Genistein decreases A549 cell viability via inhibition of the PI3K/AKT/HIF‑1α/VEGF and NF‑κB/COX‑2 signaling pathways

Genistein is an important chemopreventive agent against atherosclerosis and cancer. However, whether genistein is effective in the treatment of lung cancer, and its underlying mechanism, remains to be determined. The present study demonstrated that genistein treatment of A549 lung cancer cells decreased viability in a dose‑ and time‑dependent manner, and induced apoptosis. Additionally, A549 cells exhibited significantly increased reactive oxygen species formation and cytochrome‑c leakage, and activated caspase‑3, B‑cell lymphoma 2‑associated X protein and apoptosis inducing factor expression levels, which are involved in the mitochondrial apoptosis pathway. Furthermore, the phosphatidylinositol‑4,5‑biphosphate 3‑kinase (PI3K)/protein kinase B (AKT)/hypoxia‑inducible factor‑1α (HIF‑1α) and nuclear factor‑κB (NF‑κB)/cyclooxygenase‑2 (COX‑2) signaling pathways were significantly downregulated by genistein treatment. In conclusion, reduced proliferation and increased apoptosis in A549 lung cancer cells was associated with inhibition of the PI3K/AKT/HIF‑1α/ and NF‑κB/COX‑2 signaling pathways, which implicates genistein as a potential chemotherapeutic agent for the treatment of lung cancer.

Inhibition of Survival Pathways MAPK and NF-kB Triggers Apoptosis in Pancreatic Ductal Adenocarcinoma Cells via Suppression of Autophagy

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with a survival rate of 4-6 months from diagnosis. PDAC is the fourth leading cause of cancer-related death in the Western world, with a mortality rate of 10 cases per 100,000 population. Chemotherapy constitutes only a palliative strategy, with limited effects on life expectancy.

AIMS

To investigate the biological response of PDAC to mitogen-activated protein kinase (MAPK) and NF-kappaB (NF-kB) inhibitors and the role of autophagy in the modulation of these signaling pathways in order to address the challenge of developing improved medical protocols for patients with PDAC.

METHODS

Two ATCC cell lines, MIAPaCa-2 and PANC-1, were used as PDAC models. Cells were exposed to inhibitors of MAPK or NF-kB survival pathways alone or after autophagy inhibition. Several aspects were analyzed, as follows: cell proliferation, by [(3)H]TdR incorporation; cell death, by TUNEL assay, regulation of autophagy by LC3-II expression level and modulation of pro-and anti-apoptotic proteins by Western blot.

RESULTS

We demonstrated that the inhibition of the MAPK and NF-kB survival pathways with U0126 and caffeic acid phenethyl ester (CAPE), respectively, produced strong inhibition of pancreatic tumor cell growth without inducing apoptotic death. Interestingly, U0126 and CAPE induced apoptosis after autophagy inhibition in a caspase-dependent manner in MIA PaCa-2 cells and in a caspase-independent manner in PANC-1 cells.

CONCLUSIONS

Here we present evidence that allows us to consider a combined therapy regimen comprising an autophagy inhibitor and a MAPK or NF-kB pathway inhibitor as a possible treatment strategy for pancreatic cancer.

Neurotrophin-4 induces myelin protein zero expression in cultured Schwann cells via the TrkB/PI3K/Akt/mTORC1 pathway

Myelin formation during peripheral nervous system development, as well as myelin repair after injury and in disease, requires multiple intrinsic and extrinsic signals. Neurotrophin-4 (NT-4) is a member of the neurotrophin family, which regulates the development of neuronal networks by participating in the growth of neuronal processes, synaptic development and plasticity, neuronal survival, and differentiation. However, the intracellular signaling pathways by which NT-4 participates in myelination by Schwann cells remain elusive. In this study, we examined the effects of NT-4 on the expression of compact myelin proteins in cultured Schwann cells. Using real-time quantitative RT-PCR and western blotting, we found that NT-4 could significantly enhance the expression of myelin protein zero (MPZ) but not the expression of myelin basic protein or peripheral myelin protein 22. Further, knockdown of truncated TrkB with small interfering RNA could eliminate the effect of NT-4 on MPZ expression. Moreover, we demonstrated that the NT-4-enhanced MPZ expression depended on Akt and mTORC1 signaling. Taken together, these results suggest that NT-4 binds TrkB to enhance the expression of MPZ in Schwann cells, probably through the PI3K/Akt/mTORC1 signaling pathway, thus contributing to myelination.

Signaling by FGF Receptor 2, Not FGF Receptor 1, Regulates Myelin Thickness through Activation of ERK1/2-MAPK, Which Promotes mTORC1 Activity in an Akt-Independent Manner

FGF signaling has emerged as a significant "late-stage" regulator of myelin thickness in the CNS, independent of oligodendrocyte differentiation. Therefore, it is critically important to identify the specific FGF receptor type and its downstream signaling molecules in oligodendrocytes to obtain better insights into the regulatory mechanisms of myelin growth. Here, we show that FGF receptor type 2 (FGFR2) is highly enriched at the paranodal loops of myelin. Conditional ablation of this receptor-type, but not FGF receptor type 1 (FGFR1), resulted in attenuation of myelin growth, expression of major myelin genes, key transcription factor Myrf and extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) activity. This was rescued by upregulating ERK1/2 activity in these mice, strongly suggesting that ERK1/2 are key transducers of FGFR2 signals for myelin growth. However, given that the PI3K/Akt/mechanistic target of rapamycin (mTOR) pathway is also known to regulate myelin thickness, we examined FGFR2-deficient mice for the expression of key signaling molecules in this pathway. A significant downregulation of p-mTOR, p-Raptor, and p-S6RP was observed, which was restored to normal by elevating ERK1/2 activity in these mice. Similar downregulation of these molecules was observed in ERK1/2 knock-out mice. Interestingly, since p-Akt levels remained largely unchanged in these mice, it suggests a mechanism of mTORC1 activation by ERK1/2 in an Akt-independent manner in oligodendrocytes. Taken together, these data support a model in which FGFs, possibly from axons, activate FGFR2 in the oligodendrocyte/myelin compartment to increase ERK1/2 activation, which ultimately targets Myrf, as well as converges with the PI3K/Akt/mTOR pathway at the level of mTORC1, working together to drive the growth of the myelin sheath, thus increasing myelin thickness.SIGNIFICANCE STATEMENT It is well accepted that myelin is a biologically active membrane in active communication with the axons. However, the axonal signals, the receptors on myelin, and the integration of intracellular signaling pathways emanating downstream from these receptors that drive the growth of the myelin sheath remain poorly understood in the CNS. This study brings up the intriguing possibility that FGF receptor 2, in the oligodendrocyte/myelin compartment, may be one such signal. Importantly, it provides compelling evidence linking FGFR2 with the ERK1/2-MAPK pathway, which converges with the PI3K/Akt/mTOR (mechanistic target of rapamycin) pathway at the level of mTORC1 and also regulates the transcription factor Myrf, together providing a mechanistic framework for regulating both the transcriptional and translational machinery required for the proper growth of the myelin sheath.

Quantification of growth factor signaling and pathway cross talk by live-cell imaging

Peptide growth factors stimulate cellular responses through activation of their transmembrane receptors. Multiple intracellular signaling cascades are engaged following growth factor-receptor binding, leading to short- and long-term biological effects. Each receptor-activated signaling pathway does not act in isolation but rather interacts at different levels with other pathways to shape signaling networks that are distinctive for each growth factor. To gain insights into the specifics of growth factor-regulated interactions among different signaling cascades, we developed a HeLa cell line stably expressing fluorescent live-cell imaging reporters that are readouts for two major growth factor-stimulated pathways, Ras-Raf-Mek-ERK and phosphatidylinositol (PI) 3-kinase-Akt. Incubation of cells with epidermal growth factor (EGF) resulted in rapid, robust, and sustained ERK signaling but shorter-term activation of Akt. In contrast, hepatocyte growth factor induced sustained Akt signaling but weak and short-lived ERK activity, and insulin-like growth factor-I stimulated strong long-term Akt responses but negligible ERK signaling. To address potential interactions between signaling pathways, we employed specific small-molecule inhibitors. In cells incubated with EGF or platelet-derived growth factor-AA, Raf activation and the subsequent stimulation of ERK reduced Akt signaling, whereas Mek inhibition, which blocked ERK activation, enhanced Akt and turned transient effects into sustained responses. Our results reveal that individual growth factors initiate signaling cascades that vary markedly in strength and duration and demonstrate in living cells the dramatic effects of cross talk from Raf and Mek to PI 3-kinase and Akt. Our data further indicate how specific growth factors can encode distinct cellular behaviors by promoting complex interactions among signaling pathways.

Dual Inhibition of PI3K/Akt and mTOR by the Dietary Antioxidant, Delphinidin, Ameliorates Psoriatic Features In Vitro and in an Imiquimod-Induced Psoriasis-Like Disease in Mice

AIM

The treatment of psoriasis remains elusive, underscoring the need for identifying novel disease targets and mechanism-based therapeutic approaches. We recently reported that the PI3K/Akt/mTOR pathway that is frequently deregulated in many malignancies is also clinically relevant for psoriasis. We also provided rationale for developing delphinidin (Del), a dietary antioxidant for the management of psoriasis. This study utilized high-throughput biophysical and biochemical approaches and in vitro and in vivo models to identify molecular targets regulated by Del in psoriasis.

RESULTS

A kinome-level screen and Kds analyses against a panel of 102 human kinase targets showed that Del binds to three lipid (PIK3CG, PIK3C2B, and PIK3CA) and six serine/threonine (PIM1, PIM3, mTOR, S6K1, PLK2, and AURKB) kinases, five of which belong to the PI3K/Akt/mTOR pathway. Surface plasmon resonance and in silico molecular modeling corroborated Del's direct interactions with three PI3Ks (α/c2β/γ), mTOR, and p70S6K. Del treatment of interleukin-22 or TPA-stimulated normal human epidermal keratinocytes (NHEKs) significantly inhibited proliferation, activation of PI3K/Akt/mTOR components, and secretion of proinflammatory cytokines and chemokines. To establish the in vivo relevance of these findings, an imiquimod (IMQ)-induced Balb/c mouse psoriasis-like skin model was employed. Topical treatment of Del significantly decreased (i) hyperproliferation and epidermal thickness, (ii) skin infiltration by immune cells, (iii) psoriasis-related cytokines/chemokines, (iv) PI3K/Akt/mTOR pathway activation, and (v) increased differentiation when compared with controls. Innovation and Conclusion: Our observation that Del inhibits key kinases involved in psoriasis pathogenesis and alleviates IMQ-induced murine psoriasis-like disease suggests a novel PI3K/AKT/mTOR pathway modulator that could be developed to treat psoriasis. Antioxid. Redox Signal. 26, 49-69.

Dissecting Cell-Fate Determination Through Integrated Mathematical Modeling of the ERK/MAPK Signaling Pathway

The past three decades have witnessed an enormous progress in the elucidation of the ERK/MAPK signaling pathway and its involvement in various cellular processes. Because of its importance and complex wiring, the ERK pathway has been an intensive subject for mathematical modeling, which facilitates the unraveling of key dynamic properties and behaviors of the pathway. Recently, however, it became evident that the pathway does not act in isolation but closely interacts with many other pathways to coordinate various cellular outcomes under different pathophysiological contexts. This has led to an increasing number of integrated, large-scale models that link the ERK pathway to other functionally important pathways. In this chapter, we first discuss the essential steps in model development and notable models of the ERK pathway. We then use three examples of integrated, multipathway models to investigate how crosstalk of ERK signaling with other pathways regulates cell-fate decision-making in various physiological and disease contexts. Specifically, we focus on ERK interactions with the phosphoinositide-3 kinase (PI3K), c-Jun N-terminal kinase (JNK), and β-adrenergic receptor (β-AR) signaling pathways. We conclude that integrated modeling in combination with wet-lab experimentation have been and will be instrumental in gaining an in-depth understanding of ERK signaling in multiple biological contexts.

Citrulline directly modulates muscle protein synthesis via the PI3K/MAPK/4E-BP1 pathway in a malnourished state: evidence from in vivo, ex vivo, and in vitro studies

Citrulline (CIT) is an endogenous amino acid produced by the intestine. Recent literature has consistently shown CIT to be an activator of muscle protein synthesis (MPS). However, the underlying mechanism is still unknown. Our working hypothesis was that CIT might regulate muscle homeostasis directly through the mTORC1/PI3K/MAPK pathways. Because CIT undergoes both interorgan and intraorgan trafficking and metabolism, we combined three approaches: in vivo, ex vivo, and in vitro. Using a model of malnourished aged rats, CIT supplementation activated the phosphorylation of S6K1 and 4E-BP1 in muscle. Interestingly, the increase in S6K1 phosphorylation was positively correlated (P < 0.05) with plasma CIT concentration. In a model of isolated incubated skeletal muscle from malnourished rats, CIT enhanced MPS (from 30 to 80% CIT vs. Ctrl, P < 0.05), and the CIT effect was abolished in the presence of wortmannin, rapamycin, and PD-98059. In vitro, on myotubes in culture, CIT led to a 2.5-fold increase in S6K1 phosphorylation and a 1.5-fold increase in 4E-BP1 phosphorylation. Both rapamycin and PD-98059 inhibited the CIT effect on S6K1, whereas only LY-294002 inhibited the CIT effect on both S6K1 and 4E-BP1. These findings show that CIT is a signaling agent for muscle homeostasis, suggesting a new role of the intestine in muscle mass control.

SNP variants at the MAP3K1/SETD9 locus 5q11.2 associate with somatic PIK3CA variants in breast cancers

Genome-wide association studies have revealed many breast cancer (BC) risk-associated genetic variants that might functionally interact with other molecular determinants of BC. We analysed the association of 21 known risk-associated single-nucleotide variants (SNVs) with recurrent somatic variants in two cohorts of 77 and 754 oestrogen receptor α-positive BCs. Four SNVs located at 5q11.2 were found to be associated with the somatic PIK3CA variant status in the pilot cohort of 77 cases with odds ratio (OR) up to 6.5 indicating strong effects, and were selected for the validation phase. Two of these SNVs, rs252913 and rs331499, located in the MAP3K1/SETD9 gene boundary, were confirmed to be associated with somatic PIK3CA variants in the large cohort with OR 2.97 (1.17-7.75) and 1.76 (1.11-2.77), respectively, notably higher than their BC risk-associated values, both around 1.1. In the presence of the SNV or of somatic PIK3CA variants, cancers express significantly elevated levels of MAP3K1 and SETD9, with synergy of SNV and PIK3CA variants in MAP3K1 gene overexpression, consistent with a preferential PIK3CA-dependent regulation of the variant alleles.

Identifying the crosstalk of dysfunctional pathways mediated by lncRNAs in breast cancer subtypes

Crosstalk among abnormal pathways widely occurs in human cancer and generally leads to insensitivity to cancer treatment. How long non-coding RNAs (lncRNAs) participate in the regulation of an abnormal pathway crosstalk in human cancer is largely unknown. Here, we proposed a strategy that integrates mRNA and lncRNA expression profiles for systematic identification of lncRNA-mediated crosstalk among risk pathways in different breast cancer subtypes. We identified 12 to 44 crosstalking pathway pairs mediated by 28 to 49 lncRNAs in four breast cancer subtypes. An LncRNA-mediated crosstalking pathway network in each breast cancer subtype was then constructed. We observed a number of breast cancer subtype-specific crosstalks of risk pathways. These subtype-specific lncRNA-mediated pathway crosstalks largely determined subtype-selective functions. Notably, we observed that lncRNAs mediated the crosstalk of pathways by cooperating with known important protein-coding genes, which play core roles in the deterioration of breast cancer. And we also identified key lncRNAs contributing to the crosstalk network in each subtype. As an example, the low expression of LIFR-AS1 was associated with poor survival in LumB subtype, and its cooperated genes IL1R and TGFBR located at the most upstream of the MAPK signaling pathway shared a common cascade path (p38 MAPKs-MEF2C) that can result in proliferation, differentiation and apoptosis. In summary, we offer an effective way to characterize complex crosstalks mediated by lncRNAs in breast cancer subtypes, which can be applied to other diseases and provide useful information for understanding the pathogenesis of human cancer.

BRD7 mediates hyperglycaemia-induced myocardial apoptosis via endoplasmic reticulum stress signalling pathway

Bromodomain-containing protein 7 (BRD7) is a tumour suppressor that is known to regulate many pathological processes including cell growth, apoptosis and cell cycle. Endoplasmic reticulum (ER) stress-induced apoptosis plays a key role in diabetic cardiomyopathy (DCM). However, the molecular mechanism of hyperglycaemia-induced myocardial apoptosis is still unclear. We intended to determine the role of BRD7 in high glucose (HG)-induced apoptosis of cardiomyocytes. In vivo, we established a type 1 diabetic rat model by injecting a high-dose streptozotocin (STZ), and lentivirus-mediated short hairpin RNA (shRNA) was used to inhibit BRD7 expression. Rats with DCM exhibited severe myocardial remodelling, fibrosis, left ventricular dysfunction and myocardial apoptosis. The expression of BRD7 was up-regulated in the heart of diabetic rats, and inhibition of BRD7 had beneficial effects against diabetes-induced heart damage. In vitro, H9c2 cardiomyoblasts was used to investigate the mechanism of BRD7 in HG-induced apoptosis. Treating H9c2 cardiomyoblasts with HG elevated the level of BRD7 via activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and increased ER stress-induced apoptosis by detecting spliced/active X-box binding protein 1 (XBP-1s) and C/EBP homologous protein (CHOP). Furthermore, down-regulation of BRD7 attenuated HG-induced expression of CHOP via inhibiting nuclear translocation of XBP-1s without affecting the total expression of XBP-1s. In conclusion, inhibition of BRD7 appeared to protect against hyperglycaemia-induced cardiomyocyte apoptosis by inhibiting ER stress signalling pathway.

Target regulation of PI3K/Akt/mTOR pathway by cannabidiol in treatment of experimental multiple sclerosis

This study was aimed to investigate whether treatment with purified cannabidiol (CBD) may counteract the development of experimental multiple sclerosis (MS), by targeting the PI3K/Akt/mTOR pathway. Although the PI3K/Akt/mTOR pathway was found to be activated by cannabinoids in several immune and non-immune cells, currently, there is no data about the effects of CBD in the PI3K/Akt/mTOR activity in MS. Experimental Autoimmune Encephalomyelitis (EAE), the most common model of MS, was induced in C57BL/6 mice by immunization with myelin oligodendroglial glycoprotein peptide (MOG)_35-55. After EAE onset, which occurs approximately 14days after disease induction, mice were daily intraperitoneally treated with CBD (10mg/kg mouse) and observed for clinical signs of EAE. At 28days from EAE-induction, mice were euthanized and spinal cord tissues were sampled to perform immunohistochemical evaluations and western blot analysis. Our results showed a clear downregulation of the PI3K/Akt/mTOR pathway following EAE induction. CBD treatment was able to restore it, increasing significantly the phosphorylation of PI3K, Akt and mTOR. Also, an increased level of BNDF in CBD-treated mice seems to be involved in the activation of PI3K/Akt/mTOR pathway. In addition, our data demonstrated that therapeutic efficacy of CBD treatment is due to reduction of pro-inflammatory cytokines, like IFN-γ and IL-17 together with an up-regulation of PPARγ. Finally, CBD was found to promote neuronal survival by inhibiting JNK and p38 MAP kinases. These results provide an interesting discovery about the regulation of the PI3K/Akt/mTOR pathway by cannabidiol administration, that could be a new potential therapeutic target for MS management.

Integrating network reconstruction with mechanistic modeling to predict cancer therapies

Signal transduction networks are often rewired in cancer cells. Identifying these alterations will enable more effective cancer treatment. We developed a computational framework that can identify, reconstruct, and mechanistically model these rewired networks from noisy and incomplete perturbation response data and then predict potential targets for intervention. As a proof of principle, we analyzed a perturbation data set targeting epidermal growth factor receptor (EGFR) and insulin-like growth factor 1 receptor (IGF1R) pathways in a panel of colorectal cancer cells. Our computational approach predicted cell line-specific network rewiring. In particular, feedback inhibition of insulin receptor substrate 1 (IRS1) by the kinase p70S6K was predicted to confer resistance to EGFR inhibition, suggesting that disrupting this feedback may restore sensitivity to EGFR inhibitors in colorectal cancer cells. We experimentally validated this prediction with colorectal cancer cell lines in culture and in a zebrafish (Danio rerio) xenograft model.

Insulin as a Potent Stimulator of Akt, ERK and Inhibin-βE Signaling in Osteoblast-Like UMR-106 Cells

Insulin is a peptide hormone of the endocrine pancreas and exerts a wide variety of physiological actions in insulin sensitive tissues, such as regulation of glucose homeostasis, cell growth, differentiation, learning and memory. However, the role of insulin in osteoblast cells remains to be fully characterized. In this study, we demonstrated that the insulin (100 nM) has the ability to stimulate the phosphorylation of protein kinase B (Akt/PKB) and extracellular signal-regulated kinase (ERK) and the levels of inhibin-βE in the osteoblast-like UMR-106 cells. This insulin-stimulated activities were abolished by the PI3K and MEK1 inhibitors LY294002 and PD98059, respectively. This is the first report proving that insulin is a potential candidate that enables the actions of inhibin-βE subunit of the TGF-β family. The current investigation provides a foundation for the realization of insulin as a potential stimulator in survival signaling pathways in osteoblast-like UMR-106 cells.

The Antiviral Alkaloid Berberine Reduces Chikungunya Virus-Induced Mitogen-Activated Protein Kinase Signaling

Chikungunya virus (CHIKV) has infected millions of people in the tropical and subtropical regions since its reemergence in the last decade. We recently identified the nontoxic plant alkaloid berberine as an antiviral substance against CHIKV in a high-throughput screen. Here, we show that berberine is effective in multiple cell types against a variety of CHIKV strains, also at a high multiplicity of infection, consolidating the potential of berberine as an antiviral drug. We excluded any effect of this compound on virus entry or on the activity of the viral replicase. A human phosphokinase array revealed that CHIKV infection specifically activated the major mitogen-activated protein kinase (MAPK) signaling pathways extracellular signal-related kinase (ERK), p38 and c-Jun NH2-terminal kinase (JNK). Upon treatment with berberine, this virus-induced MAPK activation was markedly reduced. Subsequent analyses with specific inhibitors of these kinases indicated that the ERK and JNK signaling cascades are important for the generation of progeny virions. In contrast to specific MAPK inhibitors, berberine lowered virus-induced activation of all major MAPK pathways and resulted in a stronger reduction in viral titers. Further, we assessed the in vivo efficacy of berberine in a mouse model and measured a significant reduction of CHIKV-induced inflammatory disease. In summary, we demonstrate the efficacy of berberine as a drug against CHIKV and highlight the importance of the MAPK signaling pathways in the alphavirus infectious cycle.

IMPORTANCE

Chikungunya virus (CHIKV) is a mosquito-borne virus that causes severe and persistent muscle and joint pain and has recently spread to the Americas. No licensed drug exists to counter this virus. In this study, we report that the alkaloid berberine is antiviral against different CHIKV strains and in multiple human cell lines. We demonstrate that berberine collectively reduced the virus-induced activation of cellular mitogen-activated protein kinase signaling. The relevance of these signaling cascades in the viral life cycle was emphasized by specific inhibitors of these kinase pathways, which decreased the production of progeny virions. Berberine significantly reduced CHIKV-induced inflammatory disease in a mouse model, demonstrating efficacy of the drug in vivo Overall, this work makes a strong case for pursuing berberine as a potential anti-CHIKV therapeutic compound and for exploring the MAPK signaling pathways as antiviral targets against alphavirus infections.

Microcystin-LR promotes cell proliferation in the mice liver by activating Akt and p38/ERK/JNK cascades

Microcystin-LR (MC-LR), a heptapeptide produced by blue-green algae, is shown to induce cytotoxicity by inhibiting protein phosphatase 2A (PP2A) activity. Our previous study revealed that MC-LR promoted cell proliferation in vitro by activating the Akt/mTORC1/S6K1 pathway. This study aims to further investigate the effects of MC-LR on cell proliferation and the correlated mechanisms in vivo. Mice were injected intraperitoneally with 20-80 μg/kg/d MC-LR from 2 h (hours) to 4 d (days). The results showed that the associations of MC-LR with PP2A/C (PP2A C subunit) were concentration-dependent but not time-dependent in the liver, whereas the total PP2A activity was inhibited in both concentration and time dependent manners. The PP2A regulator α4 was found to release its associated PP2A/C as MC-LR bound to PP2A/C. Importantly, 80 μg/kg MC-LR promoted liver cell proliferation beginning at 1 d post exposure, and hyperproliferation also occurred in the 40 μg/kg group at 4 d after exposure. Meanwhile, the Akt/mTORC1/S6K1 and Akt/β-catenin signaling pathways were activated as early as at 2 h post exposure. Furthermore, MC-LR also activated ERK/p38/JNK MAPKs as early as at 2 h post exposure, which was supported by the hyperphosphorylation of their substrates, ATF-2, c-Jun and c-Myc. Interestingly, the total c-Jun and c-Myc levels also increased after MC-LR exposure. These findings indicate that MC-LR can also promote cell proliferation in vivo, and the activation of Akt and MAPK signaling pathways due to PP2A inhibition is proposed to participate in this process.

RAS and downstream RAF-MEK and PI3K-AKT signaling in neuronal development, function and dysfunction

In postmitotic neurons, the activation of RAS family small GTPases regulates survival, growth and differentiation. Dysregulation of RAS or its major effector pathway, the cascade of RAF-, mitogen-activated and extracellular-signal regulated kinase kinases (MEK), and extracellular-signal regulated kinases (ERK) causes the RASopathies, a group of neurodevelopmental disorders whose pathogenic mechanisms are the subject of intense research. I here summarize the functions of RAS-RAF-MEK-ERK signaling in neurons in vivo, and discuss perspectives for harnessing this pathway to enable novel treatments for nervous system injury, the RASopathies, and possibly other neurological conditions.

Dynamic culture yields engineered myocardium with near-adult functional output

Engineered cardiac tissues hold promise for cell therapy and drug development, but exhibit inadequate function and maturity. In this study, we sought to significantly improve the function and maturation of rat and human engineered cardiac tissues. We developed dynamic, free-floating culture conditions for engineering "cardiobundles", 3-dimensional cylindrical tissues made from neonatal rat cardiomyocytes or human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) embedded in fibrin-based hydrogel. Compared to static culture, 2-week dynamic culture of neonatal rat cardiobundles significantly increased expression of sarcomeric proteins, cardiomyocyte size (∼2.1-fold), contractile force (∼3.5-fold), and conduction velocity of action potentials (∼1.4-fold). The average contractile force per cross-sectional area (59.7 mN/mm²) and conduction velocity (52.5 cm/s) matched or approached those of adult rat myocardium, respectively. The inferior function of statically cultured cardiobundles was rescued by transfer to dynamic conditions, which was accompanied by an increase in mTORC1 activity and decline in AMPK phosphorylation and was blocked by rapamycin. Furthermore, dynamic culture effects did not stimulate ERK1/2 pathway and were insensitive to blockers of mechanosensitive channels, suggesting increased nutrient availability rather than mechanical stimulation as the upstream activator of mTORC1. Direct comparison with phenylephrine treatment confirmed that dynamic culture promoted physiological cardiomyocyte growth rather than pathological hypertrophy. Optimized dynamic culture conditions also augmented function of human cardiobundles made reproducibly from cardiomyocytes derived from multiple hPSC lines, resulting in significantly increased contraction force (∼2.5-fold) and conduction velocity (∼1.4-fold). The average specific force of 23.2 mN/mm² and conduction velocity of 25.8 cm/s approached the functional metrics of adult human myocardium. In conclusion, we have developed a versatile methodology for engineering cardiac tissues with a near-adult functional output without the need for exogenous electrical or mechanical stimulation, and have identified mTOR signaling as an important mechanism for advancing tissue maturation and function in vitro.

Modulation of thyroidal radioiodide uptake by oncological pipeline inhibitors and Apigenin

Targeted radioiodine therapy for thyroid cancer is based on selective stimulation of Na+/I- Symporter (NIS)-mediated radioactive iodide uptake (RAIU) in thyroid cells by thyrotropin. Patients with advanced thyroid cancer do not benefit from radioiodine therapy due to reduced or absent NIS expression. To identify inhibitors that can be readily translated into clinical care, we examined oncological pipeline inhibitors targeting Akt, MEK, PI3K, Hsp90 or BRAF in their ability to increase RAIU in thyroid cells expressing BRAFV600E or RET/PTC3 oncogene. Our data showed that (1) PI3K inhibitor GDC-0941 outperformed other inhibitors in RAIU increase mainly by decreasing iodide efflux rate to a great extent; (2) RAIU increase by all inhibitors was extensively reduced by TGF-β, a cytokine secreted in the invasive fronts of thyroid cancers; (3) RAIU reduction by TGF-β was mainly mediated by NIS reduction and could be reversed by Apigenin, a plant-derived flavonoid; and (4) In the presence of TGF-β, GDC-0941 with Apigenin co-treatment had the highest RAIU level in both BRAFV600E expressing cells and RET/PTC3 expressing cells. Taken together, Apigenin may serve as a dietary supplement along with small molecule inhibitors to improve radioiodine therapeutic efficacy on invasive tumor margins thereby minimizing future metastatic events.