Pyk2 amplifies epidermal growth factor and c-Src-induced Stat3 activation

C-terminally phosphorylated p27 activates self-renewal driver genes to program cancer stem cell expansion, mammary hyperplasia and cancer

In many cancers, a stem-like cell subpopulation mediates tumor initiation, dissemination and drug resistance. Here, we report that cancer stem cell (CSC) abundance is transcriptionally regulated by C-terminally phosphorylated p27 (p27pT157pT198). Mechanistically, this arises through p27 co-recruitment with STAT3/CBP to gene regulators of CSC self-renewal including MYC, the Notch ligand JAG1, and ANGPTL4. p27pTpT/STAT3 also recruits a SIN3A/HDAC1 complex to co-repress the Pyk2 inhibitor, PTPN12. Pyk2, in turn, activates STAT3, creating a feed-forward loop increasing stem-like properties in vitro and tumor-initiating stem cells in vivo. The p27-activated gene profile is over-represented in STAT3 activated human breast cancers. Furthermore, mammary transgenic expression of phosphomimetic, cyclin-CDK-binding defective p27 (p27CK-DD) increases mammary duct branching morphogenesis, yielding hyperplasia and microinvasive cancers that can metastasize to liver, further supporting a role for p27pTpT in CSC expansion. Thus, p27pTpT interacts with STAT3, driving transcriptional programs governing stem cell expansion or maintenance in normal and cancer tissues.

Role of c-Src in Carcinogenesis and Drug Resistance

The aberrant transformation of normal cells into cancer cells, known as carcinogenesis, is a complex process involving numerous genetic and molecular alterations in response to innate and environmental stimuli. The Src family kinases (SFK) are key components of signaling pathways implicated in carcinogenesis, with c-Src and its oncogenic counterpart v-Src often playing a significant role. The discovery of c-Src represents a compelling narrative highlighting groundbreaking discoveries and valuable insights into the molecular mechanisms underlying carcinogenesis. Upon oncogenic activation, c-Src activates multiple downstream signaling pathways, including the PI3K-AKT pathway, the Ras-MAPK pathway, the JAK-STAT3 pathway, and the FAK/Paxillin pathway, which are important for cell proliferation, survival, migration, invasion, metastasis, and drug resistance. In this review, we delve into the discovery of c-Src and v-Src, the structure of c-Src, and the molecular mechanisms that activate c-Src. We also focus on the various signaling pathways that c-Src employs to promote oncogenesis and resistance to chemotherapy drugs as well as molecularly targeted agents.

A Single-Step Genome-Wide Association Study for Semen Traits of Egyptian Buffalo Bulls

The present study aimed to contribute to the limited research on buffalo (Bubalus bubalis) semen traits by incorporating genomic data. A total of 8465 ejaculates were collected. The genotyping procedure was conducted using the Axiom® Buffalo Genotyping 90 K array designed by the Affymetrix Expert Design Program. After conducting a quality assessment, we utilized 67,282 SNPs genotyped in 192 animals. We identified several genomic loci explaining high genetic variance by employing single-step genomic evaluation. The aforementioned regions were located on buffalo chromosomes no. 3, 4, 6, 7, 14, 16, 20, 22, and the X-chromosome. The X-chromosome exhibited substantial influence, accounting for 4.18, 4.59, 5.16, 5.19, and 4.31% of the genomic variance for ejaculate volume, mass motility, livability, abnormality, and concentration, respectively. In the examined genomic regions, we identified five novel candidate genes linked to male fertility and spermatogenesis, four in the X-chromosome and one in chromosome no. 16. Additional extensive research with larger sample sizes and datasets is imperative to validate these findings and evaluate their applicability for genomic selection.

Advancement of regulating cellular signaling pathways in NSCLC target therapy via nanodrug

Lung cancer (LC) is one of the leading causes of high cancer-associated mortality worldwide. Non-small cell lung cancer (NSCLC) is the most common type of LC. The mechanisms of NSCLC evolution involve the alterations of multiple complex signaling pathways. Even with advances in biological understanding, early diagnosis, therapy, and mechanisms of drug resistance, many dilemmas still need to face in NSCLC treatments. However, many efforts have been made to explore the pathological changes of tumor cells based on specific molecular signals for drug therapy and targeted delivery. Nano-delivery has great potential in the diagnosis and treatment of tumors. In recent years, many studies have focused on different combinations of drugs and nanoparticles (NPs) to constitute nano-based drug delivery systems (NDDS), which deliver drugs regulating specific molecular signaling pathways in tumor cells, and most of them have positive implications. This review summarized the recent advances of therapeutic targets discovered in signaling pathways in NSCLC as well as the related NDDS, and presented the future prospects and challenges.

RAGE inhibitor TTP488 (Azeliragon) suppresses metastasis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic cancer subtype, which is generally untreatable once it metastasizes. We hypothesized that interfering with the Receptor for Advanced Glycation End-products (RAGE) signaling with the small molecule RAGE inhibitors (TTP488/Azeliragon and FPS-ZM1) would impair TNBC metastasis and impair fundamental mechanisms underlying tumor progression and metastasis. Both TTP488 and FPS-ZM1 impaired spontaneous and experimental metastasis of TNBC models, with TTP488 reducing metastasis to a greater degree than FPS-ZM1. Transcriptomic analysis of primary xenograft tumor and metastatic tissue revealed high concordance in gene and protein changes with both drugs, with TTP488 showing greater potency against metastatic driver pathways. Phenotypic validation of transcriptomic analysis by functional cell assays revealed that RAGE inhibition impaired TNBC cell adhesion to multiple extracellular matrix proteins (including collagens, laminins, and fibronectin), migration, and invasion. Neither RAGE inhibitor impaired cellular viability, proliferation, or cell cycle in vitro. Proteomic analysis of serum from tumor-bearing mice revealed RAGE inhibition affected metastatic driver mechanisms, including multiple cytokines and growth factors. Further mechanistic studies by phospho-proteomic analysis of tumors revealed RAGE inhibition led to decreased signaling through critical BC metastatic driver mechanisms, including Pyk2, STAT3, and Akt. These results show that TTP488 impairs metastasis of TNBC and further clarifies the signaling and cellular mechanisms through which RAGE mediates metastasis. Importantly, as TTP488 displays a favorable safety profile in human studies, our study provides the rationale for evaluating TTP488 in clinical trials to treat or prevent metastatic TNBC.

STAT3 and PD-L1 are negatively correlated with ATM and have impact on the prognosis of triple-negative breast cancer patients with low ATM expression

INTRODUCTION

Triple-negative breast cancer (TNBC) is known for its aggressive behaviors and lacking of effective treatment. Programmed cell death ligand-1 (PD-L1) inhibitor has just been approved for using in the management of advanced TNBC. To accurately screen TNBC sensitive to anti-PD-L1 treatment and to explore the feasibility of the ataxia-telangiectasia mutation protein (ATM) inhibitor combined with PD-L1 inhibitor, radiotherapy and chemotherapy, we focus on whether ATM participates in the regulation of PD-L1 and affects the prognosis of patients through c-Src, signal transducer and activator of transcription 1&3 (STAT1 and STAT3).

MATERIALS AND METHODS

We used immunohistochemical staining to explore the relationship of ATM with c-Src, STAT1, STAT3, PD-1/PD-L1, Tumor-infiltrating lymphocytes (TILs), as well as other clinicopathologic features in 86 pathological stage III TNBCs. Their impact on prognosis was also explored.

RESULTS

We found ATM expression was negatively correlated with STAT1, STAT3, PD-L1, TILs and CD8 + cells in TNBC. STAT1 positively correlated the expression of PD-L1. In TNBC with ATM low expression, STAT3 was an independent factor for improved prognosis, while PD-L1 was an independent negative prognostic factor. Furthermore, in low ATM group, the phosphorylation of tyrosine at position 419 of c-Src (p-c-src Y419) was correlated with the overexpression of STAT3.

CONCLUSION

Locally advanced TNBC with low ATM expression may be more likely to benefit from anti-PD-L1 inhibitors. The feasibility of ATM functional inhibitor combined with immune checkpoint blockade therapies in the treatment of TNBC is also worthy of further exploration. Our study suggests that STAT3 has different impacts on tumor progression in different tumors.

Unravelling the Role of Kinases That Underpin Androgen Signalling in Prostate Cancer

The androgen receptor (AR) signalling pathway is the key driver in most prostate cancers (PCa), and is underpinned by several kinases both upstream and downstream of the AR. Many popular therapies for PCa that target the AR directly, however, have been circumvented by AR mutation, such as androgen receptor variants. Some upstream kinases promote AR signalling, including those which phosphorylate the AR and others that are AR-regulated, and androgen regulated kinase that can also form feed-forward activation circuits to promotes AR function. All of these kinases represent potentially druggable targets for PCa. There has generally been a divide in reviews reporting on pathways upstream of the AR and those reporting on AR-regulated genes despite the overlap that constitutes the promotion of AR signalling and PCa progression. In this review, we aim to elucidate which kinases—both upstream and AR-regulated—may be therapeutic targets and require future investigation and ongoing trials in developing kinase inhibitors for PCa.

Sperm-oocyte signaling: the role of IZUMO1R and CD9 in PTK2B activation and actin remodeling at the sperm binding site†

Sperm-oocyte binding initiates an outside-in signaling event in the mouse oocyte that triggers recruitment and activation of the cytosolic protein kinase PTK2B in the cortex underlying the bound sperm. While not involved in gamete fusion, PTK2B activity promotes actin remodeling events important during sperm incorporation. However, the mechanism by which sperm-oocyte binding activates PTK2B is unknown, and the present study examined the possibility that sperm interaction with specific oocyte surface proteins plays an important role in PTK2B activation. Imaging studies revealed that as IZUMO1R and CD9 became concentrated at the sperm binding site, activated (phosphorylated) PTK2B accumulated in the cortex underlying the sperm head and in microvilli partially encircling the sperm head. In order to determine whether IZUMO1R and/or CD9 played a significant role in PTK2B recruitment and activation at the sperm binding site, the ability of oocytes null for Izumo1r or Cd9, to initiate an increase in PTK2B content and activation was tested. The results revealed that IZUMO1R played a minor role in PTK2B activation and had no effect on actin remodeling; however, CD9 played a very significant role in PTK2B activation and subsequent actin remodeling at the sperm binding site. These findings suggest the possibility that interaction of sperm surface proteins with CD9 or CD9-associated oocyte proteins triggers PTK2B activation at the sperm binding site.

Scrodentoids H and I, a Pair of Natural Epimerides from Scrophularia dentata, Inhibit Inflammation through JNK-STAT3 Axis in THP-1 Cells

Background

Scrophularia dentata is an important medicinal plant and used for the treatment of exanthema and fever in Traditional Tibetan Medicine. Scrodentoids H and I (SHI), a pair of epimerides of C₁₉-norditerpenoids isolated from Scrophularia dentata, could transfer to each other in room temperature and were firstly reported in our previous work. Here, we first reported the anti-inflammatory effects of SHI on LPS-induced inflammation.

Purpose

To evaluate the anti-inflammatory property of SHI, we investigated the effects of SHI on LPS-activated THP-1 cells.

Methods

THP-1 human macrophages were pretreated with SHI and stimulated with LPS. Proinflammatory cytokines IL-1β and IL-6 were measured by RT-PCR and enzyme-linked immunosorbent assays (ELISA). The mechanism of action involving phosphorylation of ERK, JNK, P38, and STAT3 was measured by western Blot. The NF-κB promoter activity was evaluated by Dual-Luciferase Reporter Assay System in TNF-α stimulated 293T cells.

Results

SHI dose-dependently reduced the production of proinflammatory cytokines IL-1β and IL-6. The ability of SHI to reduce production of cytokines is associated with phosphorylation depress of JNK and STAT3 rather than p38, ERK, and NF-κB promoter.

Conclusions

Our experimental results indicated that anti-inflammatory effects of SHI exhibit attenuation of LPS-induced inflammation and inhibit activation through JNK/STAT3 pathway in macrophages. These results suggest that SHI might have a potential in treating inflammatory disease.

Proline-rich tyrosine kinase 2 via enhancing signal transducer and activator of transcription 3-dependent cJun expression mediates retinal neovascularization

Despite the involvement of proline-rich tyrosine kinase 2 (Pyk2) in endothelial cell angiogenic responses, its role in pathological retinal angiogenesis is not known. In the present study, we show that vascular endothelial growth factor A (VEGFA) induces Pyk2 activation in mediating human retinal microvascular endothelial cell (HRMVEC) migration, sprouting and tube formation. Downstream to Pyk2, VEGFA induced signal transducer and activator of transcription 3 (STAT3) activation and cJun expression in the modulation of HRMVEC migration, sprouting and tube formation. Consistent with these observations, hypoxia induced activation of Pyk2-STAT3-cJun signaling axis and siRNA-mediated downregulation of Pyk2, STAT3 or cJun levels substantially inhibited hypoxia-induced retinal endothelial cell proliferation, tip cell formation and neovascularization. Together, these observations suggest that activation of Pyk2-mediated STAT3-cJun signaling is required for VEGFA-induced HRMVEC migration, sprouting and tube formation in vitro and hypoxia-induced retinal endothelial cell proliferation, tip cell formation and neovascularization in vivo.

Fatty acid binding protein 5 promotes metastatic potential of triple negative breast cancer cells through enhancing epidermal growth factor receptor stability

Fatty acid binding protein 5 (FABP5), an intracellular lipid binding protein, has been shown to play a role in various cancers, including breast cancer. However, FABP5 and its role in triple negative breast cancer (TNBC) have not been studied. We show FABP5 protein expression correlates with TNBC, high grade tumors, and worse disease-free survival in a tissue microarray containing 423 breast cancer patient samples. High FABP5 expression significantly correlates with epidermal growth factor receptor (EGFR) expression in these samples. Decreased tumor growth and lung metastasis were observed in FABP5-/- mice othotopically injected with murine breast cancer cells. FABP5 loss in TNBC tumor cells inhibited motility and invasion. Mechanistic studies revealed that FABP5 knockdown in TNBC cells results in decreased EGFR expression and FABP5 is important for EGF-induced metastatic signaling. Loss of FABP5 leads to proteasomal targeting of EGFR. Our studies show that FABP5 has a role in both host and tumor cell during breast cancer progression. These findings suggest that FABP5 mediates its enhanced effect on TNBC metastasis, in part, through EGFR, by inhibiting EGFR proteasomal degradation. These studies show, for the first time, a correlation between FABP5 and EGFR in enhancing TNBC metastasis through a novel mechanism.

Targeting PYK2 mediates microenvironment-specific cell death in multiple myeloma

Multiple myeloma (MM) remains an incurable malignancy due, in part, to the influence of the bone marrow microenvironment on survival and drug response. Identification of microenvironment-specific survival signaling determinants is critical for the rational design of therapy and elimination of MM. Previously, we have shown that collaborative signaling between β1 integrin-mediated adhesion to fibronectin and interleukin-6 confers a more malignant phenotype via amplification of signal transducer and activator of transcription 3 (STAT3) activation. Further characterization of the events modulated under these conditions with quantitative phosphotyrosine profiling identified 193 differentially phosphorylated peptides. Seventy-seven phosphorylations were upregulated upon adhesion, including PYK2/FAK2, Paxillin, CASL and p130CAS consistent with focal adhesion (FA) formation. We hypothesized that the collaborative signaling between β1 integrin and gp130 (IL-6 beta receptor, IL-6 signal transducer) was mediated by FA formation and proline-rich tyrosine kinase 2 (PYK2) activity. Both pharmacological and molecular targeting of PYK2 attenuated the amplification of STAT3 phosphorylation under co-stimulatory conditions. Co-culture of MM cells with patient bone marrow stromal cells (BMSC) showed similar β1 integrin-specific enhancement of PYK2 and STAT3 signaling. Molecular and pharmacological targeting of PYK2 specifically induced cell death and reduced clonogenic growth in BMSC-adherent myeloma cell lines, aldehyde dehydrogenase-positive MM cancer stem cells and patient specimens. Finally, PYK2 inhibition similarly attenuated MM progression in vivo. These data identify a novel PYK2-mediated survival pathway in MM cells and MM cancer stem cells within the context of microenvironmental cues, providing preclinical support for the use of the clinical stage FAK/PYK2 inhibitors for treatment of MM, especially in a minimal residual disease setting.

Cytoskeletal rearrangement and Src and PI-3K-dependent Akt activation control GABA(B)R-mediated chemotaxis

The γ-amino butyric acid (GABA) type B receptors (GABA(B)R) function as chemoattractant receptors in response to GABA(B)R agonists in human neutrophils. The goal of this study was to define signaling mechanisms regulating GABA(B)R-mediated chemotaxis and cytoskeletal rearrangement. In a proteomic study we identified serine/threonine kinase Akt, tyrosine kinases Src and Pyk2, microtubule regulator kinesin and microtubule affinity-regulating kinase (MARK) co-immunoprecipitating with GABA(B)R. To define the contributions of these candidate signaling events in GABA(B)R-mediated chemotaxis, we used rat basophilic leukemic cells (RBL-2H3 cells) stably transfected with human GABA(B1b) and GABA(B2) receptors. The GABA(B)R agonist baclofen induced Akt phosphorylation and chemotaxis by binding to its specific GABA(B)R since pretreatment of cells with CGP52432, a GABA(B)R antagonist, blocked such effects. Moreover, baclofen induced Akt phosphorylation was shown to be dependent upon PI-3K and Src kinases. Baclofen failed to stimulate actin polymerization in suspended RBL cells unless exposed to a baclofen gradient. However, baclofen stimulated both actin and tubulin polymerization in adherent RBL-GABA(B)R cells. Blockade of actin and tubulin polymerization by treatment of cells with cytochalasin D or nocodazole respectively, abolished baclofen-mediated chemotaxis. Furthermore, baclofen stimulated Pyk2 and STAT3 phosphorylation, both known regulators of cell migration. In conclusion, GABA(B)R stimulation promotes chemotaxis in RBL cells which is dependent on signaling via PI3-K/Akt, Src kinases and on rearrangement of both microtubules and actin cytoskeleton. These data define mechanisms of GABA(B)R-mediated chemotaxis which may potentially be used to therapeutically regulate cellular response to injury and disease.

CCR7 regulates cell migration and invasion through JAK2/STAT3 in metastatic squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (SCCHN) frequently involves metastasis at diagnosis. Our previous research has demonstrated that CCR7 plays a key role in regulating SCCHN metastasis, and this process involves several molecules, such as PI3K/cdc42, pyk2, and Src. In this study, the goals are to identify whether JAK2/STAT3 also participates in CCR7's signal network, its relationship with other signal pathways, and its role in SCCHN cell invasion and migration. The results showed that stimulation of CCL19 could induce JAK2/STAT3 phosphorylation, which can be blocked by Src and pyk2 inhibitors. After activation, STAT3 was able to promote low expression of E-cadherin and had no effect on vimentin. This JAk2/STAT3 pathway not only mediated CCR7-induced cell migration but also mediated invasion speed. The immunohistochemistry results also showed that the phosphorylation of STAT3 was correlated with CCR7 expression in SCCHN, and CCR7 and STAT3 phosphorylation were all associated with lymph node metastasis. In conclusion, JAk2/STAT3 plays a key role in CCR7 regulating SCCHN metastasis.

Electrical stimulation induces IL-6 in skeletal muscle through extracellular ATP by activating Ca(2+) signals and an IL-6 autocrine loop

Interleukin-6 (IL-6) is an important myokine that is highly expressed in skeletal muscle cells upon exercise. We assessed IL-6 expression in response to electrical stimulation (ES) or extracellular ATP as a known mediator of the excitation-transcription mechanism in skeletal muscle. We examined whether the canonical signaling cascade downstream of IL-6 (IL-6/JAK2/STAT3) also responds to muscle cell excitation, concluding that IL-6 influences its own expression through a positive loop. Either ES or exogenous ATP (100 μM) increased both IL-6 expression and p-STAT3 levels in rat myotubes, a process inhibited by 100 μM suramin and 2 U/ml apyrase. ATP also evoked IL-6 expression in both isolated skeletal fibers and extracts derived from whole FDB muscles. ATP increased IL-6 release up to 10-fold. STAT3 activation evoked by ATP was abolished by the JAK2 inhibitor HBC. Blockade of secreted IL-6 with a neutralizing antibody or preincubation with the STAT3 inhibitor VIII reduced STAT3 activation evoked by extracellular ATP by 70%. Inhibitor VIII also reduced by 70% IL-6 expression evoked by ATP, suggesting a positive IL-6 loop. In addition, ATP increased up to 60% the protein levels of SOCS3, a negative regulator of the IL-6 signaling pathway. On the other hand, intracellular calcium chelation or blockade of IP3-dependent calcium signals abolished STAT3 phosphorylation evoked by either extracellular ATP or ES. These results suggest that expression of IL-6 in stimulated skeletal muscle cells is mediated by extracellular ATP and nucleotide receptors, involving IP3-dependent calcium signals as an early step that triggers a positive IL-6 autocrine loop.

Genetic Interactions of STAT3 and Anticancer Drug Development

Signal transducer and activator of transcription 3 (STAT3) plays critical roles in tumorigenesis and malignant evolution and has been intensively studied as a therapeutic target for cancer. A number of STAT3 inhibitors have been evaluated for their antitumor activity in vitro and in vivo in experimental tumor models and several approved therapeutic agents have been reported to function as STAT3 inhibitors. Nevertheless, most STAT3 inhibitors have yet to be translated to clinical evaluation for cancer treatment, presumably because of pharmacokinetic, efficacy, and safety issues. In fact, a major cause of failure of anticancer drug development is lack of efficacy. Genetic interactions among various cancer-related pathways often provide redundant input from parallel and/or cooperative pathways that drives and maintains survival environments for cancer cells, leading to low efficacy of single-target agents. Exploiting genetic interactions of STAT3 with other cancer-related pathways may provide molecular insight into mechanisms of cancer resistance to pathway-targeted therapies and strategies for development of more effective anticancer agents and treatment regimens. This review focuses on functional regulation of STAT3 activity; possible interactions of the STAT3, RAS, epidermal growth factor receptor, and reduction-oxidation pathways; and molecular mechanisms that modulate therapeutic efficacies of STAT3 inhibitors.

Efficient one-pot synthesis of tigogenin saponins and their antitumor activities

An efficient synthesis of naturally occurring tigogenin triglycoside 1a and its three derivatives 1b-d bearing different carbohydrate moieties, as well as their antitumor activities, is described. Partially protected thiogalactosides bearing unprotected 2,4-OH or 4-OH groups were used to facilitate regioselective reactions for one-pot sequential multi-step glycosylation, which has significantly simplified the target molecule synthesis. The synthetic saponins 1a-d exhibited much higher anti-tumor activities than the positive control cisplatin against the human epithelial cervical cancer cell (HeLa) as evaluated by CCK-8 assay.

Tyrosine 23 Phosphorylation of Annexin A2 Promotes Proliferation, Invasion, and Stat3 Phosphorylation in the Nucleus of Human Breast Cancer SK-BR-3 Cells

Objective

To investigate the role of tyrosine 23 (Tyr23) phosphorylation of Annexin A2 (Anxa2) in regulating the proliferation and invasion of human breast cancer SK-BR-3 cells.

Methods

A panel of lentivirus plasmids expressing Anxa2-wide type (Ana2-WT), Anxa2-Y23A, and Anxa2-Y23D was generated and infected with SK-BR-3 cells. The monoclonal strains were screened. The expression of Anxa2-WT, Anxa2-Y23A, and Anxa2-Y23D was determined by Western blot analysis. The ability of the cells to proliferate was detected through an MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] test. Boyden chamber assays were employed to examine migration and invasion abilities. The interaction between Anxa2 and Stat3 was analyzed by immunoprecipitation analyses. Nucleoprotein and cytosolic protein were extracted from SK-BR-3, Anxa2-WT, Anxa2-Y23A, and Anxa2-Y23D cells to analyze the expression and localization of Stat3 phosphorylation.

Results

The monoclonal strains constitutively expressing Anxa2-WT, Anxa2-Y23A, and Anxa2-Y23D were screened. Both Anxa2-WT and Anxa2-Y23D enhanced the proliferation, migration and invasion abilities of SK-BR-3 cells (P<0.05). Immunoprecipitation analysis revealed that Anxa2 and Stat3 interacted with each other, and the expression of Stat3 phosphorylation in the nucleus was enhanced by Anxa2-Y23D.

Conclusions

Tyr23 phosphorylation of Anxa2 promotes the proliferation and invasion of human breast cancer SK-BR-3 cells and the phosphorylation of Stat3 in the nucleus.

Src kinase signaling mediates estrous behavior induced by 5β-reduced progestins, GnRH, prostaglandin E2 and vaginocervical stimulation in estrogen-primed rats

The progesterone receptor (PR) is a dual function protein that acts in the nucleus as a transcriptional factor and at the cytoplasm as a scaffold for the Src-MAPK signaling pathway. Several agents lacking affinity for the PR, such as 5β-reduced progestins, GnRH or prostaglandin E(2) (PGE(2)) facilitate estrous behavior in ovariectomized (ovx), estrogen-primed rats yet their action is blocked by the antiprogestin RU486. We hypothesize that these agents act by using the PR-Src-mitogen activated protein kinase alternative pathway. To test this hypothesis we used PP2, a specific inhibitor of the Src kinase family. Intraventricular infusion of 30 μg of PP2, 30 min before behavioral testing, significantly attenuated estrous behaviors induced in estradiol benzoate (E(2)B)-primed rats by 5β-dihydroprogesterone (5β-DHP), 5β-pregnan-3β-ol-20-one (5β,3β-Pgl), GnRH, PGE(2) and by manual flank/vaginocervical stimulation. These results suggest that the Src signaling system, by activating mitogen-activated protein kinases, participates in the facilitation of estrous behavior in E(2)B-primed rats induced by agents lacking affinity for the PR.

DOCK8 functions as an adaptor that links TLR-MyD88 signaling to B cell activation

The adaptors DOCK8 and MyD88 have been linked to serological memory. Here we report that DOCK8-deficient patients had impaired antibody responses and considerably fewer CD27(+) memory B cells. B cell proliferation and immunoglobulin production driven by Toll-like receptor 9 (TLR9) were considerably lower in DOCK8-deficient B cells, but those driven by the costimulatory molecule CD40 were not. In contrast, TLR9-driven expression of AICDA (which encodes the cytidine deaminase AID), the immunoglobulin receptor CD23 and the costimulatory molecule CD86 and activation of the transcription factor NF-κB, the kinase p38 and the GTPase Rac1 were intact. DOCK8 associated constitutively with MyD88 and the tyrosine kinase Pyk2 in normal B cells. After ligation of TLR9, DOCK8 became tyrosine-phosphorylated by Pyk2, bound the Src-family kinase Lyn and linked TLR9 to a Src-kinase Syk-transcription factor STAT3 cascade essential for TLR9-driven B cell proliferation and differentiation. Thus, DOCK8 functions as an adaptor in a TLR9-MyD88 signaling pathway in B cells.

Mitochondrial localized STAT3 is involved in NGF induced neurite outgrowth

Background

Signal transducer and activator of transcription 3 (STAT3) plays critical roles in neural development and is increasingly recognized as a major mediator of injury response in the nervous system. Cytokines and growth factors are known to phosphorylate STAT3 at tyrosine⁷⁰⁵ with or without the concomitant phosphorylation at serine⁷²⁷, resulting in the nuclear localization of STAT3 and subsequent transcriptional activation of genes. Recent evidence suggests that STAT3 may control cell function via alternative mechanisms independent of its transcriptional activity. Currently, the involvement of STAT3 mono-phosphorylated at residue serine⁷²⁷ (P-Ser-STAT3) in neurite outgrowth and the underlying mechanism is largely unknown.

Principal Findings

In this study, we investigated the role of nerve growth factor (NGF) induced P-Ser-STAT3 in mediating neurite outgrowth. NGF induced the phosphorylation of residue serine⁷²⁷ but not tyrosine⁷⁰⁵ of STAT3 in PC12 and primary cortical neuronal cells. In PC12 cells, serine but not tyrosine dominant negative mutant of STAT3 was found to impair NGF induced neurite outgrowth. Unexpectedly, NGF induced P-Ser-STAT3 was localized to the mitochondria but not in the nucleus. Mitochondrial STAT3 was further found to be intimately involved in NGF induced neurite outgrowth and the production of reactive oxygen species (ROS).

Conclusion

Taken together, the findings herein demonstrated a hitherto unrecognized novel transcription independent mechanism whereby the mitochondria localized P-Ser-STAT3 is involved in NGF induced neurite outgrowth.

PYK2 signaling is required for PDGF-dependent vascular smooth muscle cell proliferation

Aberrant vascular smooth muscle cell (VSMC) growth is associated with many vascular diseases including atherosclerosis, hypertension, and restenosis. Platelet-derived growth factor-BB (PDGF) induces VSMC proliferation through control of cell cycle progression and protein and DNA synthesis. Multiple signaling cascades control VSMC growth, including members of the mitogen-activated protein kinase (MAPK) family as well as phosphatidylinositol 3-kinase (PI3K) and its downstream effector AKT/protein kinase B (PKB). Little is known about how these signals are integrated by mitogens and whether there are common receptor-proximal signaling control points that synchronize the execution of physiological growth functions. The nonreceptor proline-rich tyrosine kinase 2 (PYK2) is activated by a variety of growth factors and G protein receptor agonists in VSMC and lies upstream of both PI3K and MAPK cascades. The present study investigated the role of PYK2 in PDGF signaling in cultured rat aortic VSMC. PYK2 downregulation attenuated PDGF-dependent protein and DNA synthesis, which correlated with inhibition of AKT and extracellular signal-regulated kinases 1 and 2 (ERK1/2) but not p38 MAPK activation. Inhibition of PDGF-dependent protein kinase B (AKT) and ERK1/2 signaling by inhibitors of upstream kinases PI3K and MEK, respectively, as well as downregulation of PYK2 resulted in modulation of the G(1)/S phase of the cell cycle through inhibition of retinoblastoma protein (Rb) phosphorylation and cyclin D(1) expression, as well as p27(Kip) upregulation. Cell division kinase 2 (cdc2) phosphorylation at G(2)/M was also contingent on PDGF-dependent PI3K-AKT and ERK1/2 signaling. These data suggest that PYK2 is an important upstream mediator in PDGF-dependent signaling cascades that regulate VSMC proliferation.

Pyk2 activation triggers epidermal growth factor receptor signaling and cell motility after wounding sheets of epithelial cells

Activation of the epidermal growth factor receptor (EGFR) is a key signaling event that promotes cells to move and cover wounds in many epithelia. We have previously shown that wounding activates the EGFR through activation of the Src family kinases (SFKs), which induce proteolytic shedding of epidermal growth factor-like ligands from the cell surface. A major goal in wound healing research is to identify early signals that promote motility, and here we examined the hypothesis that members of the focal adhesion kinase family are upstream activators of the SFKs after wounding. We found that focal adhesion kinase is not activated by wounding but that a different family member, Pyk2 (PTK2B/RAFTK/CAKbeta), is activated rapidly and potently. Pyk2 interaction with c-Src is increased after wounding, as determined by co-immunoprecipitation experiments. Disruption of Pyk2 signaling either by small interfering RNA or by expression of a dominant negative mutant led to inhibition of wound-induced activation of the SFKs and the EGFR, and conversely, overexpression of wild-type Pyk2 stimulated SFK and EGFR kinase activities in cells. In wound healing studies, Pyk2 small interfering RNA or dominant negative inhibited cell migration. These results show that activation of Pyk2 is an early signal that promotes wound healing by stimulating the SFK/EGFR signaling pathway.

Drug targets for tumorigenesis: insights from structural analysis of EGFR signaling network

Deciphering the complex network structure is crucial in drug target identification. This study presents a framework incorporating graph theoretic and network decomposition methods to analyze system-level properties of the comprehensive map of the epidermal growth factor receptor (EGFR) signaling, which is a good candidate model system to study the general mechanisms of signal transduction. The graph theoretic analysis of the EGFR network indicates that it has small-world characteristics with scale-free topology. The employment of network decomposition analysis enlightened the system-level properties, such as network cross-talk, specific molecules in each pathway and participation of molecules in the network. Participating in a significant fraction of the fundamental paths connecting the ligands to the phenotypes, cofactor GTP and complex Gbeta/Ggamma were identified as "housekeeping" molecules, through which all pathways of EGFR network are cross-talking. c-Src-Shc complex is identified as important due to its role in all fundamental paths through tumorigenesis and being specific to this phenotype. Inhibitors of this complex may be good anti-cancer agents having very little or no effect on other phenotypes.

Pituitary adenylate cyclase-activating polypeptide 38-mediated Rin activation requires Src and contributes to the regulation of HSP27 signaling during neuronal differentiation

Pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) is a potent neuropeptide that acts through G-protein-coupled receptors. While it is well established that PACAP mediates both neurotrophic and neurodevelopmental effects, the signaling cascades that underlie these diverse actions remain incompletely characterized. Here we show that the Ras-related Rin GTP-binding protein, a GTPase that is expressed predominantly in neurons, is regulated by PACAP38 signaling, and loss-of-function analysis demonstrates that Rin makes an essential contribution to PACAP38-mediated pheochromocytoma cell differentiation. Rin is activated following stimulation of both Gsalpha and Gialpha cascades but does not rely upon cyclic AMP (cAMP)-, Ca(2+)-, or Epac-dependent signaling pathways. Instead, Rin is activated in a Src kinase-dependent manner. Surprisingly, Rin knockdown significantly inhibits PACAP38-mediated neurite outgrowth, without affecting mitogen-activated protein kinase signaling cascades. Instead, Rin loss attenuates PACAP38-mediated HSP27 activation by disrupting a cAMP-protein kinase A cascade. RNA interference-mediated HSP27 silencing suppresses both PACAP38- and Rin-mediated neurite outgrowth, while expression of a constitutively active Rin mutant increases both HSP27 protein and phospho-HSP27 levels, supporting a role for Rin-HSP27 signaling in neuronal differentiation. Together, these observations identify an unsuspected role for Rin in neuronal PACAP signaling and establish a novel Galpha-Src-Rin-HSP27 signal transduction pathway as a critical element in PACAP38-mediated neuronal differentiation signaling.

SOCS3 inhibiting migration of A549 cells correlates with PYK2 signaling in vitro

Background

Suppressor of cytokine signaling 3 (SOCS3) is considered to inhibit cytokine responses and play a negative role in migration of various cells. Proline-rich tyrosine kinase 2 (PYK2) is a non-receptor kinase and has been found crucial to cell motility. However, little is known about whether SOCS3 could regulate PYK2 pro-migratory function in lung cancer.

Methods

The methylation status of SOCS3 was investigated in HBE and A549 cell lines by methylation-specific PCR. A549 cells were either treated with a demethylation agent 5-aza-2'-deoxycytidine or transfected with three SOCS3 mutants with various functional domains deleted. Besides, cells were pretreated with a proteasome inhibitor β-lactacystin where indicated. The effects of SOCS3 up-regulation on PYK2 expression, PYK2 and ERK1/2 phosphorylations were assessed by western blot using indicated antibodies. RT-PCR was used to estimate PYK2 mRNA levels. Transwell experiments were performed to evaluate cell migration.

Results

SOCS3 expression was found impaired in A549 cells and higher PYK2 activity was correlated with enhanced cell migration. We identified that SOCS3 was aberrantly methylated in the exon 2, and 5-aza-2'-deoxycytidine restored SOCS3 expression. Reactivation of SOCS3 attenuated PYK2 expression and phosphorylation, cell migration was inhibited as well. Transfection studies indicated that exogenous SOCS3 interacted with PYK2, and both the Src homology 2 (SH2) and the kinase inhibitory region (KIR) domains of SOCS3 contributed to PYK2 binding. Furthermore, SOCS3 was found to inhibit PYK2-associated ERK1/2 activity in A549 cells. SOCS3 possibly promoted degradation of PYK2 in a SOCS-box-dependent manner and interfered with PYK2-related signaling events, such as cell migration.

Conclusion

These data indicate that SOCS3 negatively regulates cell motility and decreased SOCS3 induced by methylation may confer a migration advantage to A549 cells. These results also suggest a negative role of SOCS3 in PYK2 signaling, and a previously unidentified regulatory mechanism for PYK2 function.

Effect of knockdown of STAT3 gene expression by shRNA on the characteristics of gastric cancer cell line MKN-45 in vitro and in vivo

AIM: To determine the effect of knockdown of STAT3 expression by shRNA on the characteristics of human gastric carcinoma cell line MKN-45 in vitro and in vivo.

METHODS: Specific shRNA plasmids to STAT3 were constructed and identified, then transfected into MKN-45. Cells were divided into three groups: control group, psiRNA-H1 group as the negative group and psiRNA-H1/STAT3 group. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting were used to detect the expression of STAT3 mRNA and protein respectively. MTT and flow cytometry were used to assess cell growth suppression and cell cycle distribution respectively. Models of xenograft in nude mice were established using the three-group cells, and the growth of stable ones was then observed.

RESULTS: Compared with the negative control cells, semi-quantitative RT-PCR and Western blotting showed that the expression of STAT3 mRNA (0.612 ± 0.074 vs 1.937 ± 0.043, P < 0.05) and protein (0.668 ± 0.054 vs 2.005 ± 0.064, P < 0.01) was down-regulated in the psiRNA-H1/STAT3 group. The subcloned recombinant plasmid expressing shRNA effectively inhibited MKN-45 cell growth and proliferation (25.42 ± 3.48 vs 33.54 ± 2.91, P < 0.05) while empty plasmid had no such specific effect. The volumes of xenografts in the psiRNA-H1/STAT3 transfection group were larger than those in the other groups (4.47 cm³ ± 0.18 cm³ vs 13.65 cm³ ± 5.64 cm³, P < 0.05).

CONCLUSION: Recombinant plasmid psiRNA-H1/STAT3 shRNA can specifically inhibit not only the expression of STAT3 mRNA and protein in vitro, but also the growth of cell line MKN-45 in vitro and in vivo.

STAT-mediated EGFR signaling in cancer

The epidermal growth factor receptor (EGFR) and signal transducers and activators of transcription (STATs) are commonly expressed and activated in many malignancies. EGFR is an upstream activator of several pathways involved in tumor progression, and STATs activate selected genes involved in oncogenesis. There are several different mechanisms by which STAT proteins can mediate intracellular EGFR signaling, including direct activation of STATs by EGFR binding and indirect activation of STATs through Src-mediated EGFR signaling. EGFR likely activates STAT in a manner distinctive from other mechanisms of STAT activation; STAT5 can be phosphorylated in an EGF-dependent manner at unique sites, conferring novel functions. Cumulative evidence suggests that targeting EGFR signaling pathways at several levels may demonstrate synergistic therapeutic effects compared with targeting the upstream receptor alone. Thus, methods to inhibit EGFR in conjunction with oncogenic STATs may represent a novel therapeutic strategy for cancers characterized by upregulation of EGFR signaling.

STAT1 and STAT3 do not participate in FGF-mediated growth arrest in chondrocytes

Activating mutations in fibroblast growth factor receptor 3 (FGFR3) cause several human skeletal dysplasias as a result of attenuation of cartilage growth. It is believed that FGFR3 inhibits chondrocyte proliferation via activation of signal transducers and activators of transcription (STAT) proteins, although the exact mechanism of both STAT activation and STAT-mediated inhibition of chondrocyte growth is unclear. We show that FGFR3 interacts with STAT1 in cells and is capable of activating phosphorylation of STAT1 in a kinase assay, thus potentially serving as a STAT1 kinase in chondrocytes. However, as demonstrated by western blotting with phosphorylation-specific antibodies, imaging of STAT nuclear translocation, STAT transcription factor assays and STAT luciferase reporter assays, FGF does not activate STAT1 or STAT3 in RCS chondrocytes, which nevertheless respond to a FGF stimulus with potent growth arrest. Moreover, addition of active STAT1 and STAT3 to the FGF signal, by means of cytokine treatment, SRC-mediated STAT activation or expression of constitutively active STAT mutants does not sensitize RCS chondrocytes to FGF-mediated growth arrest. Since FGF-mediated growth arrest is rescued by siRNA-mediated downregulation of the MAP kinase ERK1/2 but not STAT1 or STAT3, our data support a model whereby the ERK arm but not STAT arm of FGF signaling in chondrocytes accounts for the growth arrest phenotype.

'Tuning' of type I interferon-induced Jak-STAT1 signaling by calcium-dependent kinases in macrophages

Immunoreceptor tyrosine-based activation motif (ITAM)-coupled receptors modulate the amplitude and nature of macrophage responses to Toll-like receptor and cytokine receptor stimulation. However, the molecular mechanisms enabling this receptor crosstalk are not known. Here we investigated the function of the calcium-dependent kinases CaMK and Pyk2 'downstream' of ITAM-associated receptors in the regulation of cytokine-induced activation of Jak kinases and STAT transcription factors. CaMK and Pyk2 relayed signals from integrins and the ITAM-containing adaptor DAP12 to augment interleukin 10- and interferon-alpha-induced Jak activation and STAT1-dependent gene expression. CaMK inhibition suppressed STAT1-mediated interferon-alpha signaling in a mouse model of systemic lupus erythematosus. Our results associate Pyk2 and Jak kinases with the linkage of signals emanating from cytokine and heterologous ITAM-dependent receptors.

RAFTK/Pyk2 regulates EGF-induced PC12 cell spreading and movement

The protein tyrosine kinase RAFTK, also termed Pyk2, is a member of the focal adhesion kinase (FAK) subfamily. In this report, we show the role of RAFTK in neuroendocrine PC12 cells upon epidermal growth factor (EGF) stimulation. Following EGF treatment, we observed that RAFTK was tyrosine-phosphorylated in a time- and dose-dependent manner, while FAK was constitutively phosphorylated and primarily regulated by cell adhesion. Moreover, we found that RAFTK associated with the phosphorylated EGF receptor (EGFR) upon EGF stimulation. RAFTK phosphorylation was mediated primarily through PLCgamma-IP3-Ca(2+) signaling and partially through PI3-Kinase. Furthermore, overexpression of PRNK, a specific dominant-negative construct of RAFTK, was sufficient to block EGF-induced cell spreading and movement. Paxillin, a key modulator of the actin cytoskeleton and an RAFTK substrate, was also phosphorylated following EGF treatment. EGF induced a dynamic reorganization of RAFTK and paxillin at neuronal adhesion sites, with the specific localization of paxillin at the inner juxtaposition of RAFTK. Additionally, we observed that RAFTK associated with the scaffold protein c-Cbl and mediated its phosphorylation. Our data demonstrate that while FAK mediated cell adhesion, RAFTK was localized at the cytoplasm where it mediated inside-out signaling through intracellular Ca(2+), thus leading to cell spreading and movement upon EGF stimulation.

Mechanisms of endothelin-1-induced MAP kinase activation in adrenal glomerulosa cells

G protein-coupled receptors (GPCRs) such as angiotensin II, bradykinin and endothelin-1 (ET-1) are critically involved in the regulation of adrenal function, including aldosterone production from zona glomerulosa cells. Whereas, substantial data are available on the signaling mechanisms of ET-1 in cardiovascular tissues, such information in adrenal glomerulosa cells is lacking. Bovine adrenal glomerulosa (BAG) cells express receptors for endothelin-1 (ET-1) and their stimulation caused phosphorylation of Src (at Tyr416), proline-rich tyrosine kinase (Pyk2 at Tyr402), extracellularly regulated signal kinases (ERK1/2), and their dependent proteins, p90 ribosomal S6 kinase (RSK-1) and CREB. ET-1 elicited these responses predominantly through activation of a G(i)-linked cascade with a minor contribution from the G(q)/PKC pathway. Whereas, selective inhibition of EGF-R kinase with AG1478 caused complete inhibition of EGF-induced ERK/RSK-1/CREB activation, it caused only partial reduction (30-40%) of such ET-1-induced responses. Consistent with this, inhibition of matrix metalloproteinases (MMPs) with GM6001 reduced ERK1/2 activation by ET-1, consistent with partial involvement of the MMP-dependent EGF-R activation in this cascade. Activation of ERK/RSK-1/CREB by both ET-1 and EGF was abolished by inhibition of Src, indicating its central role in ET-1 signaling in BAG cells. Moreover, the signaling characteristics of ET-1 in cultured BAG cells closely resembled those observed in clonal adrenocortical H295R cells. The ET-1-induced proliferation of BAG and H295 R cells was much smaller than that induced by Ang II or FGF. These data demonstrate that ET-1 causes ERK/RSK-1/CREB phosphorylation predominantly through activation of G(i) and Src, with a minor contribution from MMP-dependent EGF-R transactivation.

The tyrosine kinase pyk2 promotes migration and invasion of glioma cells

Glioblastoma multiforme is extraordinarily aggressive due to the propensity of cells to migrate away from the tumor core into the surrounding normal brain. In this report, we investigated the role of proline-rich tyrosine kinase 2 (Pyk2) and FAK with regard to influencing glioma cell phenotypes. Expression of Pyk2 stimulated glioma cell migration, whereas expression of FAK inhibited glioma cell migration and stimulated cell cycle progression. Pyk2 autophosphorylation was necessary, but not sufficient, to stimulate cellular migration. The N-terminal domain of Pyk2 is required for stimulation of migration as an N-terminally deleted variant of Pyk2 failed to stimulate migration, whereas expression of an autonomous Pyk2 N-terminal domain inhibited cell migration. Substitution of the C-terminal domain of Pyk2 with the corresponding domain of FAK stimulated cell migration as effectively as wild-type Pyk2; however, substitution of the N-terminal domain of Pyk2 with that of FAK inhibited cell migration, substantiating that the N-terminal domain of Pyk2 was required to stimulate migration. Silencing of Pyk2 expression by RNA interference significantly inhibited glioma migration. Cell migration was restored on re-expression of Pyk2, but expression of FAK in Pyk2 knockdown cells failed to restore migration. We conclude that Pyk2 plays a central role in the migratory behavior of glioblastomas.

Mechanisms of extracellularly regulated kinases 1/2 activation in adrenal glomerulosa cells by lysophosphatidic acid and epidermal growth factor

The regulation of adrenal function, including aldosterone production from adrenal glomerulosa cells, is dependent on a variety of G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). In many cell types, GPCR-mediated MAPK activation is mediated through transactivation of RTKs, in particular the epidermal growth factor (EGF) receptor (EGF-R). However, the extent to which this cross-communication between GPCRs and RTKs is operative in the adrenal glomerulosa has not been defined. Bovine adrenal glomerulosa cells express receptors for lysophosphatidic acid (LPA) and EGF. In cultured bovine adrenal glomerulosa cells, LPA, which is predominantly coupled to Gi and partially to Gq/protein kinase C alpha and epsilon, caused phosphorylation of Src (at Tyr416), proline-rich tyrosine kinase (Pyk2 at Tyr402), EGF-R, protein kinase B/Akt, extracellularly regulated signal kinases 1/2, and their dependent protein, p90 ribosomal S6 kinase. Overexpression of dominant negative mutants of Ras or EGF-R, and selective inhibition of EGF-R kinase with AG1478, significantly reduced LPA-induced ERK1/2 phosphorylation. However, this was not impaired by inhibition of matrix metalloproteinase (MMP) and heparin-binding EGF. LPA-induced ERK1/2 activation occurs predominantly through EGF-R transactivation by Gi/Src and partly through activation of protein kinase C, which acts downstream of EGF-R and Ras. In contrast, LPA-induced phosphorylation of Shc and ERK1/2 in clonal hepatocytes (C9 cells) was primarily mediated through MMP-dependent transactivation of the EGF-R. These observations in adrenal glomerulosa and hepatic cells demonstrate that LPA phosphorylates ERK1/2 through EGF-R transactivation in a MMP-dependent or -independent manner in individual target cells. This reflects the ability of GPCRs expressed in cell lines and neoplastic cells to utilize distinct signaling pathways that can elicit altered responses compared with those of native tissues.

A comprehensive pathway map of epidermal growth factor receptor signaling

The epidermal growth factor receptor (EGFR) signaling pathway is one of the most important pathways that regulate growth, survival, proliferation, and differentiation in mammalian cells. Reflecting this importance, it is one of the best-investigated signaling systems, both experimentally and computationally, and several computational models have been developed for dynamic analysis. A map of molecular interactions of the EGFR signaling system is a valuable resource for research in this area. In this paper, we present a comprehensive pathway map of EGFR signaling and other related pathways. The map reveals that the overall architecture of the pathway is a bow-tie (or hourglass) structure with several feedback loops. The map is created using CellDesigner software that enables us to graphically represent interactions using a well-defined and consistent graphical notation, and to store it in Systems Biology Markup Language (SBML).

Targeting multiple signaling pathways as a strategy for managing prostate cancer: multifocal signal modulation therapy

The aberrant behavior of cancer reflects upregulation of certain oncogenic signaling pathways that promote proliferation, inhibit apoptosis, and enable the cancer to spread and evoke angiogenesis. Theoretically, it should be feasible to decrease the activity of these pathways-or increase the activity of pathways that oppose them-with noncytotoxic agents. Since multiple pathways are dysfunctional in most cancers, and cancers accumulate new oncogenic mutations as they progress, the greatest and most durable therapeutic benefit will likely be achieved with combination regimens that address several targets. Thus, a multifocal signal modulation therapy (MSMT) of cancer is proposed. This concept has already been documented by researchers who have shown that certain combinations of signal modulators-of limited utility when administered individually-can achieve dramatic suppression of tumor growth in rodent xenograft models. The present essay attempts to guide development of MSMTs for prostate cancer. Androgen ablation is a signal-modulating measure already in standard use in the management of delocalized prostate cancer. The additional molecular targets considered here include the type 1 insulin-like growth factor receptor, the epidermal growth factor receptor, mammalian target of rapamycin, NF-kappaB, hypoxia-inducible factor-1alpha, hsp90, cyclooxygenase-2, protein kinase A type I, vascular endothelial growth factor, 5-lipoxygenase, 12-lipoxygenase, angiotensin II receptor type 1, bradykinin receptor type 1, c-Src, interleukin-6, ras, MDM2, bcl-2/bclxL, vitamin D receptor, estrogen receptor-beta, and PPAR-. Various nutrients and phytochemicals suspected to have potential utility in prostate cancer prevention and therapy, but whose key molecular targets are still unknown, might reasonably be incorporated into MSMTs for prostate cancer; these include lycopene, selenium, green tea polyphenols, genistein, and silibinin. MSMTs can be developed systematically by testing various combinations of signal-modulating agents, in concentrations that can feasibly be achieved and maintained clinically, on human prostate cancer cell lines; combinations that appear promising can then be tested in xenograft models and, ultimately, in the clinic. Some signal modulators can increase response to cytotoxic drugs by upregulating effectors of apoptosis. When MSMTs fail to raise the spontaneous apoptosis rate sufficiently to achieve tumor stasis or regression, incorporation of appropriate cytotoxic agents into the regimen may improve the clinical outcome.

The interplay between Src family kinases and receptor tyrosine kinases

Src family tyrosine kinases (SFKs) are involved in a diverse array of physiological processes, as highlighted in this review. An overview of how SFKs interact with, and participate in signaling from, receptor tyrosine kinases (RTKs) is discussed. And also, how SFKs are activated by RTKs, and how SFKs, in turn, can activate RTKs, as well as how SFKs can promote signaling from growth factor receptors in a number of ways including participation in signaling pathways required for DNA synthesis, control of receptor turnover, actin cytoskeleton rearrangements and motility, and survival are discussed.