A new invertebrate NPY-like polypeptide, ZoaNPY, from the Zoanthus sociatus, as a novel ligand of human NPY Y2 receptor rescues vascular insufficiency via PLC/PKC and Src- FAK-dependent signaling pathways.

Our recent multi-omics studies have revealed rich sources of novel bioactive proteins and polypeptides from marine organisms including cnidarians. In the present study, we initially conducted a transcriptomic analysis to review the composition profile of polypeptides from Zoanthus sociatus. Then, a newly discovered NPY-like polypeptide-ZoaNPY was selected for further in silico structural, binding and virtually pharmacological studies. To evaluate the pro-angiogenic effects of ZoaNPY, we employed an in vitro HUVECs model and an in vivo zebrafish model. Our results indicate that ZoaNPY, at 1-100 pmol, enhances cell survival, migration and tube formation in the endothelial cells. Besides, treatment with ZoaNPY could restore a chemically-induced vascular insufficiency in zebrafish embryos. Western blot results demonstrated the application of ZoaNPY could increase the phosphorylation of proteins related to angiogenesis signaling including PKC, PLC, FAK, Src, Akt, mTOR, MEK, and ERK1/2. Furthermore, through molecular docking and surface plasmon resonance (SPR) verification, ZoaNPY was shown to directly and physically interact with NPY Y2 receptor. In view of this, all evidence showed that the pro-angiogenic effects of ZoaNPY involve the activation of NPY Y2 receptor, thereby activating the Akt/mTOR, PLC/PKC, ERK/MEK and Src- FAK-dependent signaling pathways. Furthermore, in an excision wound model, the treatment with ZoaNPY was shown to accelerate the wound healing process in mice. Our findings provide new insights into the discovery and development of novel pro-angiogenic drugs derived from NPY-like polypeptides in the future.

Anti-Metastatic Effect of Pyruvate Dehydrogenase Kinase 4 Inhibition in Bladder Cancer via the ERK, SRC, and JNK Pathways.

Bladder cancer is a common global cancer with a high percentage of metastases and high mortality rate. Thus, it is necessary to identify new biomarkers that can be helpful in diagnosis. Pyruvate dehydrogenase kinase 4 (PDK4) belongs to the PDK family and plays an important role in glucose utilization in living organisms. In the present study, we evaluated the role of PDK4 in bladder cancer and its related protein changes. First, we observed elevated PDK4 expression in high-grade bladder cancers. To screen for changes in PDK4-related proteins in bladder cancer, we performed a comparative proteomic analysis using PDK4 knockdown cells. In bladder cancer cell lines, PDK4 silencing resulted in a lower rate of cell migration and invasion. In addition, a PDK4 knockdown xenograft model showed reduced bladder cancer growth in nude mice. Based on our results, PDK4 plays a critical role in the metastasis and growth of bladder cancer cells through changes in ERK, SRC, and JNK.

TRIM50 acts as a novel Src suppressor and inhibits ovarian cancer progression.

Src is a known proto-oncogene and its aberrant activity is involved in a variety of cancers, including ovarian cancer, whereas the regulatory mechanism of Src has not been fully clarified. In this study, we identified tripartite motif-containing (TRIM) 50 as a novel negative regulator of Src protein. Our data showed that TRIM50 directly interacted with SH3 domain of Src via its B-box domain; and TRIM50 reduced Src stability by inducing RING domain-dependent K48-linked poly-ubiquitous modification. We further demonstrated that TRIM50 acted as a tumor suppressor in ovarian cancer cells by its negative regulation of Src protein. In vivo animal model verified that TRIM50 inhibited the xenograft tumor growth of ovarian cancer by suppressing Src protein. Clinical investigation showed that expression of TRIM50 in clinical specimens was inversely correlated with the clinical stages, pathology grades and lymph node metastatic status of the patients, which indicated the involvement of aberrant TRIM50 expression in disease progression. Further analysis verified the negative correlation between TRIM50 and Src expression in clinical specimens. Altogether, we identified TRIM50 as a novel suppressor of Src protein, and demonstrated that TRIM50 inhibited ovarian cancer progression by targeting Src and reducing its activity, which provided a novel therapeutic strategy for Src over-activated cancers by positive regulation of TRIM50.

Inhibition of SRC/FAK cue: A novel pathway for the synergistic effect of rosuvastatin on the anti-cancer effect of dasatinib in hepatocellular carcinoma.

PURPOSE: Statins extended their hypocholestremic effect to show a promising anticancer activity. Hepatocellular carcinoma (HCC), the third common cause of cancer-related death, responded positively to statins. Some in-vitro studies reveal the rosuvastatin antitumor effect, but barely in-vivo studies. Hence, we evaluated the antitumor potential of rosuvastatin in a HCC model, the possible signaling cues involved, and whether it augments the dasatinib anticancer effect. METHOD: For the in-vitro study, the IC50 and the combination (CI)/dose reduction (DRI) indices were determined for HCC cell line (HepG2) treated with dasatinib and/or rosuvastatin. For the in-vivo study, mice with diethylnitrosamine-induced HCC were treated for 21 days with dasatinib and/or rosuvastatin (10 and 20 mg/kg, respectively). The p-focal adhesion kinase/p-rous sarcoma oncogene cellular homolog (p-FAK/p-Src) cascade and its downstream molecules were assessed. RESULTS: The in-vitro study confirmed the synergistic effect of rosuvastatin with dasatinib, which entailed the in-vivo results. The two drugs decreased the p-FAK/p-Src cue along with p-Ras/c-Raf, p-STAT-3, and p-Akt levels to enhance apoptosis by an increase in caspase-3 level and a decline in survivin level. Additionally, they inhibited HGF, VEGF, and the MMP-9. Moreover, the different treatments downregulated the expression of proliferative cell nuclear antigen (PCNA) and Ki-67. The best effect was mediated by the combination regimen that surpassed the effect of either drug alone. CONCLUSION: Our results highlighted some of the signals involved in rosuvastatin antitumor effect and nominate it as an adds-on therapy with dasatinib to yield a better effect in HCC through inhibiting the FAK/Src cascade.

Adhesion structures in leukemia cells and their regulation by Src family kinases.

Interaction of leukemia blasts with the bone marrow extracellular matrix often results in protection of leukemia cells from chemotherapy and in persistence of the residual disease which is on the basis of subsequent relapses. The adhesion signaling pathways have been extensively studied in adherent cells as well as in mature haematopoietic cells, but the adhesion structures and signaling in haematopoietic stem and progenitor cells, either normal or malignant, are much less explored. We analyzed the interaction of leukemia cells with fibronectin (FN) using interference reflection microscopy, immunofluorescence, measurement of adherent cell fraction, real-time microimpedance measurement and live cell imaging. We found that leukemia cells form very dynamic adhesion structures similar to early stages of focal adhesions. In contrast to adherent cells, where Src family kinases (SFK) belong to important regulators of focal adhesion dynamics, we observed only minor effects of SFK inhibitor dasatinib on leukemia cell binding to FN. The relatively weak involvement of SFK in adhesion structure regulation might be associated with the lack of cytoskeletal mechanical tension in leukemia cells. On the other hand, active Lyn kinase was found to specifically localize to leukemia cell adhesion structures and a less firm cell attachment to FN was often associated with higher Lyn activity (this unexpectedly occurred also after cell treatment with the inhibitor SKI-1). Lyn thus may be important for signaling from integrin-associated complexes to other processes in leukemia cells.

Receptor Protein Tyrosine Phosphatase α-Mediated Enhancement of Rheumatoid Synovial Fibroblast Signaling and Promotion of Arthritis in Mice.

OBJECTIVE: During rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) critically promote disease pathogenesis by aggressively invading the extracellular matrix of the joint. The focal adhesion kinase (FAK) signaling pathway is emerging as a contributor to the anomalous behavior of RA FLS. The receptor protein tyrosine phosphatase α (RPTPα), which is encoded by the PTPRA gene, is a key promoter of FAK signaling. The aim of this study was to investigate whether RPTPα mediates FLS aggressiveness and RA pathogenesis. METHODS: Through RPTPα knockdown, we assessed FLS gene expression by quantitative polymerase chain reaction analysis and enzyme-linked immunosorbent assay, invasion and migration by Transwell assays, survival by annexin V and propidium iodide staining, adhesion and spreading by immunofluorescence microscopy, and activation of signaling pathways by Western blotting of FLS lysates. Arthritis development was examined in RPTPα-knockout (KO) mice using the K/BxN serum-transfer model. The contribution of radiosensitive and radioresistant cells to disease was evaluated by reciprocal bone marrow transplantation. RESULTS: RPTPα was enriched in the RA synovial lining. RPTPα knockdown impaired RA FLS survival, spreading, migration, invasiveness, and responsiveness to platelet-derived growth factor, tumor necrosis factor, and interleukin-1 stimulation. These phenotypes correlated with increased phosphorylation of Src on inhibitory Y(527) and decreased phosphorylation of FAK on stimulatory Y(397) . Treatment of RA FLS with an inhibitor of FAK phenocopied the knockdown of RPTPα. RPTPα-KO mice were protected from arthritis development, which was due to radioresistant cells. CONCLUSION: By regulating the phosphorylation of Src and FAK, RPTPα mediates proinflammatory and proinvasive signaling in RA FLS, correlating with the promotion of disease in an FLS-dependent model of RA.

Cysteine-Mediated Redox Regulation of Cell Signaling in Chondrocytes Stimulated With Fibronectin Fragments.

OBJECTIVE: Oxidative posttranslational modifications of intracellular proteins can potentially regulate signaling pathways relevant to cartilage destruction in arthritis. In this study, oxidation of cysteine residues to form sulfenic acid (S-sulfenylation) was examined in osteoarthritic (OA) chondrocytes and investigated in normal chondrocytes as a mechanism by which fragments of fibronectin (FN-f) stimulate chondrocyte catabolic signaling. METHODS: Chondrocytes isolated from OA and normal human articular cartilage were analyzed using analogs of dimedone that specifically and irreversibly react with protein S-sulfenylated cysteines. Global S-sulfenylation was measured in cell lysates with and without FN-f stimulation by immunoblotting and in fixed cells by confocal microscopy. S-sulfenylation in specific proteins was identified by mass spectroscopy and confirmed by immunoblotting. Src activity was measured in live cells using a fluorescence resonance energy transfer biosensor. RESULTS: Proteins in chondrocytes isolated from OA cartilage were found to have elevated basal levels of S-sulfenylation relative to those of chondrocytes from normal cartilage. Treatment of normal chondrocytes with FN-f induced increased levels of S-sulfenylation in multiple proteins, including the tyrosine kinase Src. FN-f treatment also increased the levels of Src activity. Pretreatment with dimedone to alter S-sulfenylation function or with Src kinase inhibitors inhibited FN-f-induced production of matrix metalloproteinase 13. CONCLUSION: These results demonstrate for the first time the presence of oxidative posttranslational modification of proteins in human articular chondrocytes by S-sulfenylation. Due to the ability to regulate the activity of a number of cell signaling pathways, including catabolic mediators induced by fibronectin fragments, S-sulfenylation may contribute to cartilage destruction in OA and warrants further investigation.

The MEK1/2 inhibitor U0126 reverses imatinib resistance through down-regulating activation of Lyn/ERK signaling pathway in imatinib-resistant K562R leukemia cells.

Chronic myelogenous leukemia (CML) is triggered by the constitutively activated BCR-ABL oncoprotein and multiple downstream signaling pathways, including the Raf/MEK/ERK, Akt/mTOR, SRC, and STAT5 pathways. The BCR-ABL tyrosine kinase inhibitor imatinib is the standard treatment for CML. However, the development of imatinib resistance has become a new challenge for CML treatment. Here, we investigated the expression levels of the signaling pathways to explore the cause of imatinib resistance and seek new reversing drugs. Our results showed that abnormal activation of the BCR-ABL-independent Lyn/ERK signaling pathway was involved in imatinib-resistance of K562R cells. Furthermore, p-Lyn and p-ERK were up-regulated after treatment with imatinib alone. However, U0126, a MEK1/2 inhibitor, could counteract the up-regulation induced by imatinib, and the combination of imatinib and U0126 could overcome the resistance to imatinib in K562R cells. In conclusion, our studies suggest that the combination of imatinib and an inhibitor of the ERK signaling pathway may be effective in imatinib-resistant CML patients.

Early induction of stress-associated Src activator/Homo sapiens chromosome 9 open reading frame 10 protein following photodynamic therapy.

BACKGROUND: There are proteins, responsible for many basic cell functions (transmission of extracellular signals to cytoplasm or nucleus, cell growth, proliferation, migration, survival), which are activated and overexpressed in response to acute oxidative stress, especially tyrosine kinases. The oxidative stress-associated Src activator/Homo sapiens chromosome 9 open reading frame 10 protein (Ossa/C9orf10) protects cancer cells from oxidative stress-induced apoptosis by Src family kinases activation. METHODS: In this study precursor of protoporphyrin IX, 5-aminolevulinic acid and its encapsulated form were used in treating MCF-7 human breast cancer cells. After light illumination, cells were collected at different time points and used for evaluation (immunocytochemistry, Western blot analysis) of expression of above proteins, c-Src and Ossa. RESULTS: Our results showed that 5-aminolevulinic acid-mediated photodynamic therapy caused decrease of c-Src expression at 7h after irradiation. The strongest expression was observed at 24h after treatment. Encapsulated form of 5-aminolevulinic acid in terms of PDT caused similar changes of expression of c-Src protein. Furthermore, we observed strong Ossa expression at 7h after treatment in comparison to very low expression at time points 0, 18 and 24h. CONCLUSION: We would like to emphasize that our results showed high expression of Ossa at early time interval after PDT, which was accompanied by a low expression of c-Src kinase, what could protect cancer cells from PDT through activation of c-Src in response to oxidative stress.

Benzo-[a]-pyrene induces FAK activation and cell migration in MDA-MB-231 breast cancer cells.

Benzo-[a]-pyrene (B[a]P) is a family member of polycyclic aromatic hydrocarbons and a widespread environmental pollutant. It is a mammary carcinogen in rodents and contributes to the development of human breast cancer. However, the signal transduction pathways induced by B[a]P and its role in breast cancer progression have not been studied in detail. Here, we demonstrate that B[a]P induces cell migration through a lipoxygenase- and Src-dependent pathway, as well as the activation of focal adhesion kinase, Src, and the extracellular signal-regulated kinase 2 in MDA-MB-231 breast cancer cells. However, B[a]P is not able to promote migration in the mammary nontumorigenic epithelial cells MCF12A. Moreover, B[a]P promotes an increase of αvß3 integrin-cell surface levels and an increase of metalloproteinase (MMP)-2 and MMP-9 secretions. In summary, our findings demonstrate that B[a]P induces the activation of signal transduction pathways and biological processes involved in the invasion/metastasis process in MDA-MB-231 breast cancer cells.

Molecular subtype and response to dasatinib, an Src/Abl small molecule kinase inhibitor, in hepatocellular carcinoma cell lines in vitro.

UNLABELLED: Hepatocellular carcinoma (HCC) is the fifth most common malignancy and is the third leading cause of cancer death worldwide. Recently, the multitargeted kinase inhibitor sorafenib was shown to be the first systemic agent to improve survival in advanced HCC. Unlike other malignancies such as breast cancer, in which molecular subtypes have been clearly defined (i.e., luminal, HER2 amplified, basal, etc.) and tied to effective molecular therapeutics (hormone blockade and trastuzumab, respectively), in HCC this translational link does not exist. Molecular profiling studies of human HCC have identified unique molecular subtypes of the disease. We hypothesized that a panel of human HCC cell lines would maintain molecular characteristics of the clinical disease and could then be used as a model for novel therapeutics. Twenty human HCC cell lines were collected and RNA was analyzed using the Agilent microarray platform. Profiles from the cell lines in vitro recapitulate previously described subgroups from clinical material. Next, we evaluated whether molecular subgroup would have predictive value for response to the Src/Abl inhibitor dasatinib. The results demonstrate that sensitivity to dasatinib was associated with a progenitor subtype. Dasatinib was effective at inducing cell cycle arrest and apoptosis in "progenitor-like" cell lines but not in resistant lines. CONCLUSION: These findings suggest that cell line models maintain the molecular background of HCC and that subtype may be important for selecting patients for response to novel therapies. In addition, it highlights a potential role for Src family signaling in this progenitor subtype of HCC.

Zinc induces protein phosphatase 2A inactivation and tau hyperphosphorylation through Src dependent PP2A (tyrosine 307) phosphorylation.

The activity of protein phosphatase (PP) 2A is downregulated and promotes the hyperphosphorylation of tau in the brains of Alzheimer's disease (AD), but the mechanism for PP2A inactivation has not been elucidated. We have reported that PP2A phosphorylation at tyrosine 307 (Y307) is involved in PP2A inactivation. Here, we further studied the upstream mechanisms for PP2A phosphorylation and inactivation. We found that zinc, a heavy metal ion that is widely distributed in the normal brain and accumulated in the susceptible regions of AD brain, could induce PP2A inhibition, phosphorylation of PP2A at Y307 and tau hyperphosphorylation both in rat brains and cultured N2a cells, while zinc chelating prevented these changes completely. Upregulation of PP2A chemically or genetically attenuated zinc-induced tau hyperphosphorylation, whereas mutation of Y307 to phenylalanine abolished the zinc-induced tyrosine phosphorylation and inactivation of PP2A. Zinc could activate Src, while PP2, a specific Src family kinases inhibitor, attenuated zinc-induced PP2A phosphorylation and inactivation, indicating that zinc induces PP2A Y307 phosphorylation and inactivation through Src activation. In human tau transgenic mice, zinc chelator rescued PP2A activity, prevented Src activation, and reduced hyperphosphorylated and insoluble tau levels. We concluded that zinc induces PP2A inactivation and tau hyperphosphorylation through Src-dependent pathway, regulation of zinc homeostasis may be a promising therapeutic for AD and the related tauopathies.

A disintegrin and metalloproteinase 15 contributes to atherosclerosis by mediating endothelial barrier dysfunction via Src family kinase activity.

OBJECTIVE: Endothelium dysfunction is an initiating factor in atherosclerosis. A disintegrin and metalloproteinase 15 (ADAM 15) is a multidomain metalloprotease recently identified as a regulator of endothelial permeability. However, whether and how ADAM15 contributes to atherosclerosis remains unknown. METHODS AND RESULTS: Genetic ablation of ADAM15 in apolipoprotein E-deficient mice led to a significant reduction in aortic atherosclerotic lesion size (by 52%), plaque macrophage infiltration (by 69%), and smooth muscle cell deposition (by 82%). In vitro studies implicated endothelial-derived ADAM15 in barrier dysfunction and monocyte transmigration across mouse aortic and human umbilical vein endothelial cell monolayers. This role of ADAM15 depended on intact functioning of the cytoplasmic domain, as evidenced in experiments with site-directed mutagenesis targeting the metalloprotease active site (E349A), the disintegrin domain (Arginine-Glycine-Aspartic acid→Threonine-Aspartic acid-Aspartic acid), or the cytoplasmic tail. Further investigations revealed that ADAM15-induced barrier dysfunction was concomitant with dissociation of endothelial adherens junctions (vascular endothelial [VE]-cadherin/γ-catenin), an effect that was sensitive to Src family kinase inhibition. Through small interfering RNA-mediated knockdown of distinct Src family kinase members, c-Src and c-Yes were identified as important mediators of these junctional effects of ADAM15. CONCLUSIONS: These results suggest that endothelial cell-derived ADAM15, signaling through c-Src and c-Yes, contributes to atherosclerotic lesion development by disrupting adherens junction integrity and promoting monocyte transmigration.

Phosphotyrosine enrichment identifies focal adhesion kinase and other tyrosine kinases for targeting in canine hemangiosarcoma.

Canine hemangiosarcoma (HSA) is an endothelial cell malignancy driven, in part, by activating mutations in receptor and non-receptor tyrosine kinases. Proteomics, Western blots and a tyrosine kinase inhibitor were used to elucidate activating mechanisms in HSA cell lines. Phosphotyrosine peptides from focal adhesion kinase (FAK) STAT3, Lyn, Fyn and other signal transduction kinases were identified by mass spectrometry. FAK was constitutively activated at tyrosine 397, the autophosphorylation site, and this was reversible with high concentrations of a FAK inhibitor. FAK inhibitor-14 suppressed migration and phosphorylation of FAK tyrosine 397 and tyrosines 576/577 and was cytotoxic to HSA cells suggesting FAK signalling may be an important contributor to canine HSA survival.

Src-family tyrosine kinases as therapeutic targets in advanced cancer.

Src-family tyrosine kinases (SFK) play critical roles in mediating many cellular pathways such as proliferation, adhesion, survival, differentiation and cell motility. There is clear evidence that SFK activity is increased in many human cancers, either through gene amplification, transcriptional upregulation, posttranslational modification by activated upstream growth factor receptors, and even in rare cases, by mutations known to increase intrinsic tyrosine kinase activity in oncoviral forms of SFK. Many recent studies using animal models of human cancer seem to indicate that SFK may only be appropriate therapeutic targets in a subset of primary tumors because of the existence of multiple independent pathways that mediate oncogenic signaling. In contrast, SFK seem to be required for specific parameters of malignant progression, such as recurrence and/or metastasis- especially involving growth in the bone microenvironment. The resulting development of SFK antagonists, and their progression through clinical trials, has brought renewed focus on this tyrosine kinase family as critical mediators of the so-called lethal phenotype of cancer.

Glabridin inhibits migration, invasion, and angiogenesis of human non-small cell lung cancer A549 cells by inhibiting the FAK/rho signaling pathway.

This study reports the antimigration, anti-invasive effect of glabridin, a flavonoid obtained from licorice, in human non-small cell lung cancer A549 cells. Glabridin exhibited effective inhibition of cell metastasis by decreasing cancer cell migration and invasion of A549 cells. In addition, glabridin also decreased A549-mediated angiogenesis. Further investigation revealed that glabridin's inhibition of cancer angiogenesis was also evident in a nude mice model. Blockade of A549 cells migration was associated with an increase of ανß3 integrin proteosome degradation. Glabridin also decreased the active forms of FAK and Src, and enhanced levels of inactivated phosphorylated Src (Tyr 527), decreasing the interaction of FAK and Src. Inhibition of the FAK/Src complex by glabridin also blocked Akt activation, resulting in reduced activation of RhoA and myosin light chain phosphorylation. This study demonstrates that glabridin may be a novel anticancer agent for the treatment of lung cancer in 3 different ways: inhibition of migration, invasion, and angiogenesis.

The SRC family of protein tyrosine kinases: a new and promising target for colorectal cancer therapy.

Aberrant activation of the Src family of tyrosine kinases has been implicated in the development and progression of colorectal cancer (CRC). As a result, Src inhibitors are now being studied as possible therapeutic agents to treat metastatic disease. In this review, we discuss the effects of aberrant Src activation in CRC, Src as a target of single-agent drug therapy, and Src as a target of combination therapy with epidermal growth factor receptor inhibition and cytotoxic chemotherapy. The greatest potential for clinically relevant benefit most likely lies in combination regimens. Further evaluation with biomarkers will continue to define the molecular phenotype of patients with CRC who will benefit the most from Src-based therapy.

Naphtho[1,2-b]furan-4,5-dione disrupts Janus kinase-2 and induces apoptosis in breast cancer MDA-MB-231 cells.

Naphtho[1,2-b]furan-4,5-dione (NFD), prepared from 2-hydroxy-1,4-naphthoquinone and chloroacetaldehyde in an efficient one-pot reaction, exhibits an anti-carcinogenic effect. NFD-induced apoptosis in MDA-MB-231 cells, as indicated by the accumulation of sub-G1 population, externalization of phosphatidylserine, loss of mitochondrial membrane potential (DeltaPsim) with subsequent release of cytochrome c, and activation of both capase-9 and caspase-3. This correlated with up-regulation in Bax and Bad, and down-regulation of various anti-apoptotic proteins, including Bcl-2, Bcl-X(L), Mcl-1, and survivin in NFD-treated cells. In the analysis of signal transduction pathway, NFD suppressed the phosphorylation of JAK2 in MDA-MB-231 cells without altering the expression of JAK2 protein. Activation of STAT3, Src, and PI3K/Akt were also inhibited by NFD. Moreover, the JAK2 inhibitor AG490 blocked JAK2, STAT3, Src, PI3K, and Akt activation, whereas both Src inhibitor PP2 and PI3K inhibitor wortmannin did not affect JAK2 activation. This suggests that STAT3, Src, and PI3K/Akt are downstream molecules of the JAK2 signaling pathway. AG490 treatment also mimics the cytotoxic effects of NFD. Taken together, these results indicate that NFD disrupts JAK2 pathway and induces apoptosis in MDA-MB-231 cells.

5-deoxykaempferol plays a potential therapeutic role by targeting multiple signaling pathways in skin cancer.

Nontoxic small molecules with multitargeting effects are believed to have potential in cancer prevention. Dietary phytochemicals were shown to exhibit cancer-preventive effects attributed to their antioxidant capacities. In this report, we show that the natural compound 5-deoxykaempferol (5-DK) exerts a chemopreventive effect on UVB-induced skin carcinogenesis by targeting multiple signaling molecules. 5-DK suppressed the UVB-induced expression of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor in mouse skin epidermal JB6 P+ cells. Moreover, 5-DK inhibited phosphorylation of MKK3/6, MKK4, and Akt, but had no effect on phosphorylation of Src, extracellular signal-regulated kinases, or ribosomal S6 kinase (RSK). However, 5-DK affected multiple targets by reducing Src, phosphoinositide 3-kinase (PI3K), and RSK2 activities. In particular, pull-down assays revealed that 5-DK specifically bound to and competed with ATP for binding with Src, PI3K, and RSK2. Exposure to 5-DK significantly suppressed UVB-induced tumorigenesis in mouse skin in a dose-dependent manner, and it inhibited the UVB-induced expression of COX-2, proliferating cell nuclear antigen, vascular endothelial growth factor, and matrix metalloproteinase-9. Our data suggest that 5-DK docks at the ATP-binding site of Src, PI3K, and RSK2. For RSK2, the ATP-binding site is located between the N- and C-lobes of the kinase domain. Taken together, our results indicate that 5-DK holds promise for the treatment of UVB-induced skin cancer by targeting Src, PI3K, and RSK2 signaling.

Dasatinib: a potent SRC inhibitor in clinical development for the treatment of solid tumors.

SRC is a tyrosine kinase that plays a role in oncogenic, invasive and bone-metastatic processes. It has therefore been prioritized as a candidate therapeutic target in patients with solid tumors. Several SRC inhibitors are now in development, of which dasatinib has been most explored. Preclinical studies in a wide variety of solid tumor cell lines, including prostate, breast and glioma, have shown that that dasatinib acts as a cytostatic agent, inhibiting the processes of cell proliferation, invasion and metastasis. Dasatinib also inhibits the activity of osteoclasts, which have a major role in the development of metastatic bone lesions. Dasatinib has additive or synergistic activity in combination with a number of other agents, including cytotoxic agents and targeted therapies, providing a rationale for combination treatment in a clinical setting. Emerging clinical data with dasatinib support experimental observations, with preliminary phase 1 and 2 data demonstrating activity, both as a single agent and as combination therapy, in a range of solid tumors. Future clinical trials will further assess the clinical value of SRC inhibition with dasatinib.