STAT5 Phosphorylation in Malignant Melanoma Is Important for Survival and Is Mediated Through SRC and JAK1 Kinases

Breviscapine ameliorates autophagy by activating the JAK2/STAT5/BCL2 pathway in a transient cerebral ischemia rat model

Breviscapine (Bre), an extract from Erigeron breviscapus, has been widely used to treat cerebral ischemia but the mechanisms of its neuroprotective effects need to be clarified. The present study investigated whether Bre could alleviate excessive autophagy induced by cerebral ischemia in the rat middle cerebral artery occlusion (MCAO) ischemia model via activating the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 5 (STAT5)/B-cell lymphoma 2 (BCL2) pathway. Rats were randomly divided into 5 groups, i.e. Sham group, MCAO+saline group, MCAO+Bre group, MCAO+DMSO (Dimethyl sulfoxide) group, and MCAO+Bre+AG490 (Tyrphostin AG490, the inhibitor of STAT5) group. The model was established and neuroprotection was evaluated by determining infarct volumes and conducting neurological behavioral tests. Autophagy levels in the infarct penumbra were detected using transmission electron microscopy and Western blotting. The expression of proteins in the JAK2/STAT5/BCL2 pathway was tested by Western blotting. Compared to the MCAO+saline group, the infarct volumes in the MCAO+Bre group were significantly reduced and neurological behavior improved. Breviscapine administration also significantly increased p-JAK2, p-STAT5, and BCL2 expression but decreased autolysosome numbers; it also downregulated Beclin-1 expression and the LC3II/LCI ratio. The JAK2 inhibitor AG490 reversed these effects. These findings indicate that breviscapine can improve neural recovery following ischemia through alleviating excessive autophagy and activation of the JAK2/STAT5/BCL2 axis.

NAMPT mediates PDGF-induced pulmonary arterial smooth muscle cell proliferation by TLR4/NF-κB/PLK4 signaling pathway

Nicotinamide phosphoribosyltransferase (NAMPT), a pleiotropic protein, promotes the proliferation and migration of pulmonary artery smooth muscle cells (PASMCs), which is associated with the genesis and progression of pulmonary arterial hypertension (PAH). NAMPT is highly increased in PAH patient's plasma and highly relevant to PAH severity. The mRNA and protein levels of NAMPT are elevated in PAH animal models. However, the underlying molecular mechanisms how NAMPT mediated platelet-derived growth factor (PDGF)-induced PASMCs proliferation are still unclear. The present study aimed to address these issues. Primary cultured PASMCs were attained from male Sprague-Dawley (SD) rats. Western blotting, RT-PCR, ELISA, cell transfection, Cell Counting Kit-8 (CCK-8) and EdU incorporation assays were used in the experiments. We showed that PDGF upregulated NAMPT expression through the activation of signal transducers and activators of transcription 5 (STAT5), and elevated extracellular NAMPT further promoted the activation of NF-κB through Toll-like receptor 4 (TLR4), which ultimately upregulated polo-like kinase 4 (PLK4) expression leading to PASMCs proliferation. Knockdown of STAT5, NAMPT or PLK4, and inhibition of TLR4 or NF-κB suppressed PDGF-induced PASMCs proliferation. Our study suggests that NAMPT plays an essential role in PDGF-induced PASMCs proliferation via TLR4/NF-κB/PLK4 pathway, suggesting that targeting NAMPT might be valuable in ameliorating pulmonary arterial hypertension.

pSTAT5 is associated with improved survival in patients with thick or ulcerated primary cutaneous melanoma

Identifying prognostic biomarkers to predict clinical outcomes in stage I and II cutaneous melanomas could guide the clinical application of adjuvant and neoadjuvant therapies. We aimed to investigate the prognostic value of phosphorylated signal transducer and activator of transcription 5 (pSTAT5) as a biomarker in early-stage melanoma. This study evaluated all initially staged Ib and II melanoma patients undergoing sentinel node biopsy at a tertiary centre in Brisbane, Australia between 1994 and 2007, with survival data collected from the Queensland Cancer Registry. Primary melanoma tissue from 189 patients was analysed for pSTAT5 level through immunohistochemistry. Cox regression modelling, with adjustment for sex, age, ulceration, anatomical location, and Breslow depth, was applied to determine the association between pSTAT5 detection and melanoma-specific survival. Median duration of follow-up was 7.4 years. High pSTAT5 detection was associated with ulceration and increased tumour thickness. However, multivariate analysis indicated that high pSTAT5 detection was associated with improved melanoma-specific survival (hazard ratio: 0.15, 95% confidence interval: 0.03-0.67) as compared to low pSTAT5 detection. This association persisted when pSTAT5 detection was limited to immune infiltrate or the vasculature, as well as when sentinel node positivity was accounted for. In this cohort, staining for high-pSTAT5 tumours identified a subset of melanoma patients with increased survival outcomes as compared to low-pSTAT5 tumours, despite the former having higher-risk clinicopathological characteristics at diagnosis. pSTAT5 is likely an indicator of local immune activation, and its detection could represent a useful tool to stratify the risk of melanoma progression.

Intracellular angiopoietin-1 promotes TKI-resistance via activation of JAK/STAT5 pathway in chronic myeloid leukemia

Drug resistance from BCR-ABL tyrosine kinase inhibitors (TKIs) and other chemotherapeutics results in treatment failure and disease progression in chronic myeloid leukemia (CML). However, the mechanism is still uncertain. In this study, we investigated the role of angiopoietin-1 (ANG-1) as a potential prognostic factor for drug resistance in CML. Both intracellular and secretory ANG-1 (iANG-1 and sANG-1) were overexpressed in multidrug-resistant CML samples. The IC₅₀ value was higher in primary CD34⁺ CD38^- cells with more ANG-1. Silencing ANG-1significantly sensitized three TKI-resistant CML cell lines to imatinib (IM) while recombinant human ANG-1 failed to retain cell survival in vitro. This indicated the important role of iANG-1 as opposed to sANG-1 in CML drug resistance. Moreover, a similar effect was observed in xenograft mice models bearing ANG-1-silenced CML cells. Subsequently, pathway analysis and protein validation experiments showed activation of the JAK/STAT pathway and augmentation of STAT5a phosphorylation in ANG-1 restored CML cells. Upstream Src phosphorylation, which plays a crucial role in CML drug resistance, was also upregulated as a key event in iANG-1-related JAK/STAT pathway activation. In conclusion, our study elucidated a new BCR-ABL independent molecular mechanism induced by intracytoplasmic ANG-1 overexpression as a potential strategy for overcoming CML resistance.

Src family kinases (SFKs): critical regulators of microglial homeostatic functions and neurodegeneration in Parkinson's and Alzheimer's diseases

c-Src was the first protein kinase to be described as capable of phosphorylating tyrosine residues. Subsequent identification of other tyrosine-phosphorylating protein kinases with a similar structure to c-Src gave rise to the concept of Src family kinases (SFKs). Microglia are the resident innate immune cell population of the CNS. Under physiological conditions, microglia actively participate in brain tissue homeostasis, continuously patrolling the neuronal parenchyma and exerting neuroprotective actions. Activation of pathogen-associated molecular pattern (PAMP) and damage-associated molecular pattern (DAMP) receptors induces microglial proliferation, migration toward pathological foci, phagocytosis, and changes in gene expression, concurrent with the secretion of cytokines, chemokines, and growth factors. A significant body of literature shows that SFK stimulation positively associates with microglial activation and neuropathological conditions, including Alzheimer's and Parkinson's diseases. Here, we review essential microglial homeostatic functions regulated by SFKs, including phagocytosis, environmental sensing, and secretion of inflammatory mediators. In addition, we discuss the potential of SFK modulation for microglial homeostasis in Parkinson's and Alzheimer's diseases.

Tumor NLRP3-Derived IL-1β Drives the IL-6/STAT3 Axis Resulting in Sustained MDSC-Mediated Immunosuppression

Tumors evade the immune system by inducing inflammation. In melanoma, tumor-derived IL-1β drives inflammation and the expansion of highly immunosuppressive myeloid-derived suppressor cells (MDSCs). Similar in many tumors, melanoma is also linked to the downstream IL-6/STAT3 axis. In this study, we observed that both recombinant and tumor-derived IL-1β specifically induce pSTAT3(Y705), creating a tumor-autoinflammatory loop, which amplifies IL-6 signaling in the human melanoma cell line 1205Lu. To disrupt IL-1β/IL-6/STAT3 axis, we suppressed IL-1β-mediated inflammation by inhibiting the NOD-like receptor protein 3 (NLRP3) using OLT1177, a safe-in-humans specific NLRP3 oral inhibitor. In vivo, using B16F10 melanoma, OLT1177 effectively reduced tumor progression (p< 0.01); in primary tumors, OLT1177 decreased pSTAT3(Y705) by 82% (p<0.01) and II6 expression by 53% (p<0.05). Disruption of tumor-derived NLRP3, either pharmacologically or genetically, reduced STAT3 signaling in bone marrow cells. In PMN-MDSCs isolated from tumor-bearing mice treated with OLT1177, we observed significant reductions in immunosuppressive genes such as Pdcd1l1, Arg1, Il10 and Tgfb1. In conclusion, the data presented here show that the inhibition of NLRP3 reduces IL-1β induction of pSTAT3(Y705) preventing expression of immunosuppressive genes as well as activity in PMN-MDSCs.

Overcoming resistance to BRAFV600E inhibition in melanoma by deciphering and targeting personalized protein network alterations

BRAFV600E melanoma patients, despite initially responding to the clinically prescribed anti-BRAFV600E therapy, often relapse, and their tumors develop drug resistance. While it is widely accepted that these tumors are originally driven by the BRAFV600E mutation, they often eventually diverge and become supported by various signaling networks. Therefore, patient-specific altered signaling signatures should be deciphered and treated individually. In this study, we design individualized melanoma combination treatments based on personalized network alterations. Using an information-theoretic approach, we compute high-resolution patient-specific altered signaling signatures. These altered signaling signatures each consist of several co-expressed subnetworks, which should all be targeted to optimally inhibit the entire altered signaling flux. Based on these data, we design smart, personalized drug combinations, often consisting of FDA-approved drugs. We validate our approach in vitro and in vivo showing that individualized drug combinations that are rationally based on patient-specific altered signaling signatures are more efficient than the clinically used anti-BRAFV600E or BRAFV600E/MEK targeted therapy. Furthermore, these drug combinations are highly selective, as a drug combination efficient for one BRAFV600E tumor is significantly less efficient for another, and vice versa. The approach presented herein can be broadly applicable to aid clinicians to rationally design patient-specific anti-melanoma drug combinations.

Xmrks the Spot: Fish Models for Investigating Epidermal Growth Factor Receptor Signaling in Cancer Research

Studies conducted in several fish species, e.g., Xiphophorus hellerii (green swordtail) and Xiphophorus maculatus (southern platyfish) crosses, Oryzias latipes (medaka), and Danio rerio (zebrafish), have identified an oncogenic role for the receptor tyrosine kinase, Xmrk, a gene product closely related to the human epidermal growth factor receptor (EGFR), which is associated with a wide variety of pathological conditions, including cancer. Comparative analyses of Xmrk and EGFR signal transduction in melanoma have shown that both utilize STAT5 signaling to regulate apoptosis and cell proliferation, PI3K to modulate apoptosis, FAK to control migration, and the Ras/Raf/MEK/MAPK pathway to regulate cell survival, proliferation, and differentiation. Further, Xmrk and EGFR may also modulate similar chemokine, extracellular matrix, oxidative stress, and microRNA signaling pathways in melanoma. In hepatocellular carcinoma (HCC), Xmrk and EGFR signaling utilize STAT5 to regulate cell proliferation, and Xmrk may signal through PI3K and FasR to modulate apoptosis. At the same time, both activate the Ras/Raf/MEK/MAPK pathway to regulate cell proliferation and E-cadherin signaling. Xmrk models of melanoma have shown that inhibitors of PI3K and MEK have an anti-cancer effect, and in HCC, that the steroidal drug, adrenosterone, can prevent metastasis and recover E-cadherin expression, suggesting that fish Xmrk models can exploit similarities with EGFR signal transduction to identify and study new chemotherapeutic drugs.

ERBB1/2/3 Expression, Prognosis, and Immune Infiltration in Cutaneous Melanoma

Background

The four ERBB tyrosine kinase family members [ERBB1 (epidermal growth factor receptor, EGFR), ERBB2 (HER2), ERBB3 (HER3), and ERBB4 (HER4)] (ERBB receptor family) have been shown, according to previous studies, to be related to the cutaneous melanoma. ERBB3 is the only member of the ERBBs that lacks tyrosine kinase activity and thus needs to dimer with other tyrosine kinases receptors to trigger the signaling pathway, while ERBB3 may dimer with all members of the ERBB family. Melanoma progression depends on activation of ERBB signaling, especially the ERBB3/ERBB2 cascade. There are lymphocytes and T cell infiltrates in melanoma. Numerous pieces of evidences indicate that local immune status plays an important role in the formation of anti-tumor immune responses. However, the relationship between the ERBBs and prognosis and immune infiltration in cutaneous melanoma is not completely clear.

Methods

The expression of the ERBBs was analyzed through the Oncomine database, Gene Expression Profiling Interactive Analysis (GEPIA), respectively. Immunohistochemistry of ERBBs was obtained from the Human Protein Atlas is increased before HPA database. ERBBs genes expression and mutation analysis in cutaneous melanoma from the cBioPortal. Functional annotation and Kyoto Encyclopedia of Genes and Genomes is increased before KEGG pathway enrichment analysis from the Metascape. Correlations between ERBBs and 31 genes that were close to each other and frequently altered were explored by GEPIA. Using the GEPIA database, we also investigated the relationship between ERBBs and myeloid-derived suppressor cells (MDSC) in cutaneous melanoma. The disease-free survival and different tumor stages of ERBBs were evaluated by GEPIA. The correlation of ERBBs and tumor-infiltrating immune cells and prognostic(5 years survival rates) was tested by the Tumor Immune Estimation Resource (TIMER).

Results

In general, the expression levels of ERBB1/2 in cutaneous melanoma were lower than those in normal skin tissue. By contrast, the ERBB3 expression level was higher in cutaneous melanoma than in normal skin tissue. Low expression of ERBB1/2 and high expression of ERBB3 were detrimental to the 5 years survival of cutaneous melanoma patients (ERBB1: log-rank P: 0.03; ERBB2: log-rank P: 0.008; ERBB3: log-rank P: 0.039). ERBB4 expression may not affect the prognosis of patients with cutaneous melanoma. ERBBs may not play a role in the tumor stage and disease-free survival in cutaneous melanoma patients. The relationship between the ERBB family and 31 genes that were close to each other and frequently altered is demonstrated as the genes regulated by the ERBB family being mainly concentrated in the RAS/RAF/MEK/ERK signaling pathway. ERBB2 can induce infiltration of CD8⁺ T cells and B cells, while ERBB3 can induce infiltration of CD4⁺ T cells, CD8⁺ T cells, and Neutrophil cells. ERBBs are more significantly associated with M1 macrophages, dendritic cells, Th1, Th2, Th17, and Treg cellular immune markers (Cor > 0.2). ERBB2/3 were related to MDSC in cutaneous melanoma, including human mononuclear myeloid-derived suppressor cells (M-MDSC) and polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC), and may influence the progression of cutaneous melanoma through MDSC, but the conclusion needs further probing.

Conclusion

This study investigated the prognosis and immune infiltration of the ERBB family in cutaneous melanoma. Our results suggest that ERBB1/2/3 may serve as early prognostic markers and potential therapeutic targets in cutaneous melanoma.

A self-designed CpG ODN enhanced the anti-melanoma effect of pimozide

Melanomas represent the deadliest form of skin cancers. Due to the intricacy of tumorigenesis, it is emergent to find effective therapies for melanomas. Researches have proved that pimozide inhibits the growth of melanoma, but the limited curing effect needs to be further improved. Nowadays, tumor immunotherapy has been widely recognized as the sole therapy that can eradicate cancers. Cytosine-phosphate-guanine oligodeoxynucleotide (CpG ODN), TLR9 receptor agonist, can significantly enhance anti-tumor immune responses. This study explored the therapeutic effect of pimozide combined with CpG ODN on melanoma-bearing mice. The results showed that pimozide combined with CpG ODN effectively inhibited the growth of melanoma and prolonged the survival of melanoma-bearing mice, inhibited the expression of MMP2 and p-Stat5, increased the infiltration of CD4⁺ and CD8⁺ T cells in tumor, raised the ratios of CD4⁺, CD8⁺ T cells and NK cells. These all indicated that the combination treatment improved the anti-tumor effect of pimozide on mice. The anti-tumor mechanism might be attributed to cell apoptosis induction, invasion inhibition, and immune regulation. A more effective combination treatment concerning with pimozide is being under investigation.

Structural Implications of STAT3 and STAT5 SH2 Domain Mutations

Src Homology 2 (SH2) domains arose within metazoan signaling pathways and are involved in protein regulation of multiple pleiotropic cascades. In signal transducer and activator of transcription (STAT) proteins, SH2 domain interactions are critical for molecular activation and nuclear accumulation of phosphorylated STAT dimers to drive transcription. Sequencing analysis of patient samples has revealed the SH2 domain as a hotspot in the mutational landscape of STAT proteins although the functional impact for the vast majority of these mutations remains poorly characterized. Despite several well resolved structures for SH2 domain-containing proteins, structural data regarding the distinctive STAT-type SH2 domain is limited. Here, we review the unique features of STAT-type SH2 domains in the context of all currently reported STAT3 and STAT5 SH2 domain clinical mutations. The genetic volatility of specific regions in the SH2 domain can result in either activating or deactivating mutations at the same site in the domain, underscoring the delicate evolutionary balance of wild type STAT structural motifs in maintaining precise levels of cellular activity. Understanding the molecular and biophysical impact of these disease-associated mutations can uncover convergent mechanisms of action for mutations localized within the STAT SH2 domain to facilitate the development of targeted therapeutic interventions.

Balancing STAT Activity as a Therapeutic Strategy

Driven by dysregulated IL-6 family member cytokine signaling in the tumor microenvironment (TME), aberrant signal transducer and activator of transcription (STAT3) and (STAT5) activation have been identified as key contributors to tumorigenesis. Following transformation, persistent STAT3 activation drives the emergence of mesenchymal/cancer-stem cell (CSC) properties, important determinants of metastatic potential and therapy failure. Moreover, STAT3 signaling within tumor-associated macrophages and neutrophils drives secretion of factors that facilitate metastasis and suppress immune cell function. Persistent STAT5 activation is responsible for cancer cell maintenance through suppression of apoptosis and tumor suppressor signaling. Furthermore, STAT5-mediated CD4+/CD25+ regulatory T cells (T_regs) have been implicated in suppression of immunosurveillance. We discuss these roles for STAT3 and STAT5, and weigh the attractiveness of different modes of targeting each cancer therapy. Moreover, we discuss how anti-tumorigenic STATs, including STAT1 and STAT2, may be leveraged to suppress the pro-tumorigenic functions of STAT3/STAT5 signaling.

STAT3 and STAT5 Targeting for Simultaneous Management of Melanoma and Autoimmune Diseases

Melanoma is a skin cancer which can become metastatic, drug-refractory, and lethal if managed late or inappropriately. An increasing number of melanoma patients exhibits autoimmune diseases, either as pre-existing conditions or as sequelae of immune-based anti-melanoma therapies, which complicate patient management and raise the need for more personalized treatments. STAT3 and/or STAT5 cascades are commonly activated during melanoma progression and mediate the metastatic effects of key oncogenic factors. Deactivation of these cascades enhances antitumor-immune responses, is efficient against metastatic melanoma in the preclinical setting and emerges as a promising targeting strategy, especially for patients resistant to immunotherapies. In the light of the recent realization that cancer and autoimmune diseases share common mechanisms of immune dysregulation, we suggest that the systemic delivery of STAT3 or STAT5 inhibitors could simultaneously target both, melanoma and associated autoimmune diseases, thereby decreasing the overall disease burden and improving quality of life of this patient subpopulation. Herein, we review the recent advances of STAT3 and STAT5 targeting in melanoma, explore which autoimmune diseases are causatively linked to STAT3 and/or STAT5 signaling, and propose that these patients may particularly benefit from treatment with STAT3/STAT5 inhibitors.

Regeneration Enhances Metastasis: A Novel Role for Neurovascular Signaling in Promoting Melanoma Brain Metastasis

Neural repair after stroke involves initiation of a cellular proliferative program in the form of angiogenesis, neurogenesis, and molecular growth signals in the surrounding tissue elements. This cellular environment constitutes a niche in which regeneration of new blood vessels and new neurons leads to partial tissue repair after stroke. Cancer metastasis has similar proliferative cellular events in the brain and other organs. Do cancer and CNS tissue repair share similar cellular processes? In this study, we identify a novel role of the regenerative neurovascular niche induced by stroke in promoting brain melanoma metastasis through enhancing cellular interactions with surrounding niche components. Repair-mediated neurovascular signaling induces metastatic cells to express genes crucial to metastasis. Mimicking stroke-like conditions in vitro displays an enhancement of metastatic migration potential and allows for the determination of cell-specific signals produced by the regenerative neurovascular niche. Comparative analysis of both in vitro and in vivo expression profiles reveals a major contribution of endothelial cells in mediating melanoma metastasis. These results point to a previously undiscovered role of the regenerative neurovascular niche in shaping the tumor microenvironment and brain metastatic landscape.

STAT5 expression correlates with recurrence and survival in melanoma patients treated with interferon-α

Interferons (IFN) have a direct growth-inhibiting effect on tumor cells through Janus kinase-dependent activation of the transcription factor signal transducer and activator of transcription (STAT1). In vitro, signaling through STAT5 has been demonstrated to counteract this effect and lead to IFN resistance of melanoma cell lines. In 32 patients treated with IFN-α in an adjuvant setting, we investigated paraffin-embedded tumor tissue from primary melanomas and melanoma metastases for expression of STAT3 and STAT5, by immunohistochemistry, and for expression of phosphorylated signaling transduction activating transcription factor (pSTAT)3 and pSTAT5, by immunofluorescence. Tumor cell expression levels of these proteins were correlated with patient characteristics and clinical outcomes. The patient cohort consisted of 12 (37.5%) patients at AJCC stage I/II (primary melanoma) and 20 (62.5%) at stage III/IV (metastatic melanoma). Recurrence was observed for 25 (78.1%) either during or after IFN-α therapy. χ Correlation of staining intensities with clinical data revealed association of pSTAT3 and STAT5 expression with sex (P=0.003 and 0.016, respectively) and of STAT3 with tumor stage (P=0.019). Recurrence of melanoma was found to be associated with high STAT5 expression (P=0.017). Multivariable regression analysis revealed STAT5 expression as an independent factor for predicting progression-free survival (P<0.0001) and overall survival (P=0.022). In summary, high expression of STAT5 correlated with melanoma recurrence and survival of patients treated with IFN-α in the adjuvant setting. Recently, it has been suggested that mutations of Janus kinases are involved in resistance to immune checkpoint blocker treatments implying a possible role of STAT5 for immune checkpoint resistance.

Reactive Oxygen Species and Oncoprotein Signaling-A Dangerous Liaison

SIGNIFICANCE

There is evidence to implicate reactive oxygen species (ROS) in tumorigenesis and its progression. This has been associated with the interplay between ROS and oncoproteins, resulting in enhanced cellular proliferation and survival. Recent Advances: To date, studies have investigated specific contributions of the crosstalk between ROS and signaling networks in cancer initiation and progression. These investigations have challenged the established dogma of ROS as agents of cell death by demonstrating a secondary function that fuels cell proliferation and survival. Studies have thus identified (onco)proteins (Bcl-2, STAT3/5, RAS, Rac1, and Myc) in manipulating ROS level as well as exploiting an altered redox environment to create a milieu conducive for cancer formation and progression.

CRITICAL ISSUES

Despite these advances, drug resistance and its association with an altered redox metabolism continue to pose a challenge at the mechanistic and clinical levels. Therefore, identifying specific signatures, altered protein expressions, and modifications as well as protein-protein interplay/function could not only enhance our understanding of the redox networks during cancer initiation and progression but will also provide novel targets for designing specific therapeutic strategies.

FUTURE DIRECTIONS

Not only a heightened realization is required to unravel various gene/protein networks associated with cancer formation and progression, particularly from the redox standpoint, but there is also a need for developing more sensitive tools for assessing cancer redox metabolism in clinical settings. This review attempts to summarize our current knowledge of the crosstalk between oncoproteins and ROS in promoting cancer cell survival and proliferation and treatment strategies employed against these oncoproteins. Antioxid. Redox Signal.

Exploring major signaling cascades in melanomagenesis: a rationale route for targetted skin cancer therapy

Although most melanoma cases may be treated by surgical intervention upon early diagnosis, a significant portion of patients can still be refractory, presenting low survival rates within 5 years after the discovery of the illness. As a hallmark, melanomas are highly prone to evolve into metastatic sites. Moreover, melanoma tumors are highly resistant to most available drug therapies and their incidence have increased over the years, therefore leading to public health concerns about the development of novel therapies. Therefore, researches are getting deeper in unveiling the mechanisms by which melanoma initiation can be triggered and sustained. In this context, important progress has been achieved regarding the roles and the impact of cellular signaling pathways in melanoma. This knowledge has provided tools for the development of therapies based on the intervention of signal(s) promoted by these cascades. In this review, we summarize the importance of major signaling pathways (mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)-Akt, Wnt, nuclear factor κ-light-chain-enhancer of activated B cell (NF-κB), Janus kinase (JAK)-signal transducer and activator of transcription (STAT), transforming growth factor β (TGF-β) and Notch) in skin homeostasis and melanoma progression. Available and developing melanoma therapies interfering with these signaling cascades are further discussed.

The enhanced antitumour response of pimozide combined with the IDO inhibitor L‑MT in melanoma

Melanoma is one of the most fatal and therapy-resistant types of cancer; therefore, identifying novel therapeutic candidates to improve patient survival is an ongoing effort. Previous studies have revealed that pimozide is not sufficient to treat melanoma; therefore, enhancing the treatment is necessary. Indoleamine 2, 3‑dioxygenase (IDO) is an immunosuppressive, intracellular rate-limiting enzyme, which contributes to immune tolerance in various tumours, including melanoma, and inhibition of IDO may be considered a novel therapeutic strategy when combined with pimozide. The present study aimed to assess the antitumour activities of pimozide in vitro, and to investigate the effects of pimozide combined with L‑methyl-tryptophan (L‑MT) in vivo. For in vitro analyses, the B16 melanoma cell line was used. Cell cytotoxicity assay, cell viability assay, wound‑healing assay and western blotting were conducted to analyse the effects of pimozide on B16 cells. Furthermore, B16 cell-bearing mice were established as the animal model. Haematoxylin and eosin staining, immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick end-labelling staining, western blotting and flow cytometry were performed to determine the effects of monotherapy and pimozide and L‑MT cotreatment on melanoma. The results demonstrated that pimozide exhibited potent antitumour activity via the regulation of proliferation, apoptosis and migration. Furthermore, the antitumour effects of pimozide were enhanced when combined with L‑MT, not only via regulation of proliferation, apoptosis and migration, but also via immune modulation. Notably, pimozide may regulate tumour immunity through inhibiting the activities of signal transducer and activator of transcription (Stat)3 and Stat5. In conclusion, the present study proposed the use of pimozide in combination with the IDO inhibitor, L‑MT, as a potential novel therapeutic strategy for the treatment of melanoma.

Expression of the serotonin receptor 2B in uveal melanoma and effects of an antagonist on cell lines

Uveal melanoma (UM) is the most common primary tumor in the adult, and disseminates to the liver in half of patients. A 15-gene expression profile prognostic assay allows to determine the likelihood of metastasis in patients using their ocular tumor DNA, but a cure still remains to be discovered. The serotonin receptor 2B represents the discriminant gene of this molecular signature with the greatest impact on the prognosis of UM. However, its contribution to the metastatic potential of UM remains unexplored. The purpose of this study was to investigate the effects of a selective serotonin receptor 2B antagonist on cellular and molecular behaviours of UM cells. UM cell lines expressing high level of serotonin receptor 2B proteins were selected by Western blotting. The selective serotonin receptor 2B antagonist PRX-08066 was evaluated for its impact on UM cells using viability assays, phosphorylated histone H3 immunostainings, clonogenic assays, migration assays, invasion assays and membrane-based protein kinase phosphorylation antibody arrays. The pharmacological inhibition of the serotonin receptor 2B reduced the viability of UM cells and the population in mitosis, and impaired their clonogenicity and potential of migration. It also decreased the phosphorylation of kinases from signaling pathways classically activated by the serotonin receptor 2B, as well as kinases β-catenin, Proline-rich tyrosine kinase 2, and Signal transducer and activator of transcription 5. Our findings support a role for the serotonin receptor 2B in the proliferation and migration of UM cells, through activation of many signaling pathways such as WNT, Focal adhesion kinase and Janus kinase/STAT.

Pivotal role of NAMPT in the switch of melanoma cells toward an invasive and drug-resistant phenotype

In BRAF^V600E melanoma cells, a global metabolomic analysis discloses a decrease in nicotinamide adenine dinucleotide (NAD⁺) levels upon PLX4032 treatment that is conveyed by a STAT5 inhibition and a transcriptional regulation of the nicotinamide phosphoribosyltransferase (NAMPT) gene. NAMPT inhibition decreases melanoma cell proliferation both in vitro and in vivo, while forced NAMPT expression renders melanoma cells resistant to PLX4032. NAMPT expression induces transcriptomic and epigenetic reshufflings that steer melanoma cells toward an invasive phenotype associated with resistance to targeted therapies and immunotherapies. Therefore, NAMPT, the key enzyme in the NAD⁺ salvage pathway, appears as a rational target in targeted therapy-resistant melanoma cells and a key player in phenotypic plasticity of melanoma cells.

Genetic and pharmacological inhibition of microRNA-92a maintains podocyte cell cycle quiescence and limits crescentic glomerulonephritis

Crescentic rapidly progressive glomerulonephritis (RPGN) represents the most aggressive form of acquired glomerular disease. While most therapeutic approaches involve potentially toxic immunosuppressive strategies, the pathophysiology remains incompletely understood. Podocytes are glomerular epithelial cells that are normally growth-arrested because of the expression of cyclin-dependent kinase (CDK) inhibitors. An exception is in RPGN where podocytes undergo a deregulation of their differentiated phenotype and proliferate. Here we demonstrate that microRNA-92a (miR-92a) is enriched in podocytes of patients and mice with RPGN. The CDK inhibitor p57^Kip2 is a major target of miR-92a that constitutively safeguards podocyte cell cycle quiescence. Podocyte-specific deletion of miR-92a in mice de-repressed the expression of p57^Kip2 and prevented glomerular injury in RPGN. Administration of an anti-miR-92a after disease initiation prevented albuminuria and kidney failure, indicating miR-92a inhibition as a potential therapeutic strategy for RPGN. We demonstrate that miRNA induction in epithelial cells can break glomerular tolerance to immune injury.

Crescentic rapidly progressive glomerulonephritis is a severe form of glomerula disease characterized by podocyte proliferation and migration. Here Henique et al. demonstrate that inhibition of miRNA-92a prevents kidney failure by promoting the expression of CDK inhibitor p57^Kip2 that regulates podocyte cell cycle.

Targeting growth hormone receptor in human melanoma cells attenuates tumor progression and epithelial mesenchymal transition via suppression of multiple oncogenic pathways

Recent reports have confirmed highest levels of growth hormone (GH) receptor (GHR) transcripts in melanoma, one of the most aggressive forms of human cancer. Yet the mechanism of GH action in melanoma remains mostly unknown. Here, using human malignant melanoma cells, we examined the effects of GH excess or siRNA mediated GHR knock-down (GHRKD) on tumor proliferation, migration and invasion. GH promoted melanoma progression while GHRKD attenuated the same. Western blot analysis revealed drastic modulation of multiple oncogenic signaling pathways (JAK2, STAT1, STAT3, STAT5, AKT, mTOR, SRC and ERK1/2) following addition of GH or GHRKD. Further, we show that GH excess upregulates expression of markers of epithelial mesenchymal transition in human melanoma, while the effects were reversed by GHRKD. Interestingly, we observed consistent expression of GH transcript in the melanoma cells as well as marked modulation of the IGF receptors and binding proteins (IGF1R, IGF2R, IR, IGFBP2, IGFBP3) and the oncogenic HGF-MET mRNA, in response to excess GH or GHRKD. Our study thus identifies the mechanistic model of GH-GHR action in human melanoma and validates it as an important pharmacological target of intervention.

Transient receptor potential cation 3 channel regulates melanoma proliferation and migration

Melanoma has an extremely poor prognosis due to its rapidly progressive and highly metastatic nature. Several therapeutic drugs have recently become available, but are effective only against melanoma with specific BRAF gene mutation. Thus, there is a need to identify other target molecules. We show here that Transient receptor potential, canonical 3 (TRPC3) is widely expressed in human melanoma. We found that pharmacological inhibition of TRPC3 with a pyrazole compound, Pyr3, decreased melanoma cell proliferation and migration. Similar inhibition was observed when the TRPC3 gene was silenced with short-hairpin RNA (shRNA). Pyr3 induced dephosphorylation of signal transducer and activator of transcription (STAT) 5 and Akt. Administration of Pyr3 (0.05 mg/kg) to mice implanted with human melanoma cells (C8161) significantly inhibited tumor growth. Our findings indicate that TRPC3 plays an important role in melanoma growth, and may be a novel target for treating melanoma in patients.

KITD816V Induces SRC-Mediated Tyrosine Phosphorylation of MITF and Altered Transcription Program in Melanoma

The oncogenic D816V mutation of the KIT receptor is well characterized in systemic mastocytosis and acute myeloid leukemia. Although KIT^D816V has been found in melanoma, its function and involvement in this malignancy is not understood. Here we show that KIT^D816V induces tyrosine phosphorylation of MITF through a triple protein complex formation between KIT, MITF, and SRC family kinases. In turn, phosphorylated MITF activates target genes that are involved in melanoma proliferation, cell-cycle progression, suppression of senescence, survival, and invasion. By blocking the triple protein complex formation, thus preventing MITF phosphorylation, the cells became hypersensitive to SRC inhibitors. We have therefore delineated a mechanism behind the oncogenic effects of KIT^D816V in melanoma and provided a rationale for the heightened SRC inhibitor sensitivity in KIT^D816V transformed cells.Implications: This study demonstrates that an oncogenic tyrosine kinase mutant, KIT^D816V, can alter the transcriptional program of the transcription factor MITF in melanoma Mol Cancer Res; 15(9); 1265-74. ©2017 AACR.

Subcellular localization of EGFR in esophageal carcinoma cell lines

BACKGROUND

The EGF receptor is a therapeutic target in cancer cells, whereby mutations of EGFR and/or signalling members act as predictive markers. EGFR however also exhibits dynamic changes of subcellular localization, leading to STAT5 complex formation, nuclear translocation and induction of Aurora-A expression in squamous cancer cells. We previously described high EGFR and Aurora-A expression in esophageal cancer cells. Here, we investigated subcellular localization of EGFR and STAT5 in esophageal cancer cells.

RESULTS

Quantitative immunofluorescence analyses of four esophageal cancer cell lines reflecting esophageal squamous cell carcinomas (ESCC) and esophageal adenocarcinomas (EAC) revealed that the subcellular localization of EGFR was shifted from a membranous to cytoplasmic localization upon EGF-stimulation in OE21 (ESCC) cells. Thereby, EGFR in part co-localized with E-Cadherin. In parallel, phosphorylated STAT5-Tyr694 appeared to increase in the nucleus and to decrease at the cell membrane. In three additional cell lines, EGFR was only marginally (Kyse-410/ESCC; OE19/EAC) and weakly (OE33, EAC) detectable at the cell membrane. Partial co-localization of EGFR and E-Cadherin occurred in OE33 cells. Post EGF-stimulation, EGFR was detected in the cytoplasm, resembling endosomal compartments. Furthermore, OE19 and OE33 exhibited nuclear STAT5-Tyr694 phosphorylation upon EGF-stimulation. None of the four cell lines showed nuclear EGFR expression and localization.

CONCLUSION

In contrast to other (squamous) cancer cells, activation of EGFR in esophageal squamous cancer cells does not result in nuclear translocation of EGFR. Still, the subcellular localization of EGFR may influence STAT5-associated signaling pathways in esophageal cancer cells and hence possibly also the responses to ErbB, respective EGFR-targeted therapies.

The importance of Src signaling in sarcoma

Src is a tyrosine kinase that is of significance in tumor biology. The present review focuses on Src, its molecular structure, and role in cancer, in addition to its expression and function in sarcoma. In addition, the feasibility of Src as a potential drug target for the treatment of sarcoma is also discussed. Previous studies have suggested that Src has essential functions in cell proliferation, apoptosis, invasion, metastasis and the tumor microenvironment. Thus, it may be a potential target for cancer therapy. Src has been found to enhance proliferation, reduce apoptosis and promote metastasis in certain subtypes of sarcoma, including osteosarcoma, chondrosarcoma and Ewing's sarcoma. Furthermore, a number of novel effective therapeutic agents, such as SI-83, which target Src have been investigated in vitro and in vivo. Bosutinib and dasatinib, which inhibit Src, have been approved by the U.S. Food and Drug Administration for the treatment of chronic myelogenous leukemia. In addition, vandetanib is approved for the treatment of medullary thyroid cancer. Furthermore, the Src inhibitor, saracatinib, is currently in clinical trials for the treatment of a variety of solid tumors, including breast and lung cancers. Thus, Src is considered to be an important factor in sarcoma progression and may present a novel clinical therapeutic target. This review demonstrates the importance and clinical relevance of Src in sarcoma, and discusses a number of small molecular inhibitors of src kinase, such as dasatinib and sarcatinib, which are currently in clinical trials for the treatment of sarcoma patients.

STAT5 is Activated by Epidermal Growth Factor and Induces Proliferation and Invasion in Trophoblastic Cells

Epidermal growth factor (EGF) is expressed by decidual and trophoblast cells and influences manifold cellular functions during embryo implantation. Thus far, signaling of EGF via Signal Transducer and Activator of Transcription 5 (STAT5) has been only partially investigated. STAT5 stimulates proliferation and cell cycle progression in several cell types. Its dysregulation is associated with pregnancy. The aim of this study was to investigate STAT5 activation and function mediated by EGF in 2 trophoblastic cell lines, namely, HTR8/SVneo and JAR. Additionally, expression of STAT5B messenger RNA (mRNA) in trophoblast models has been compared to that of primary cells isolated from term placentas. Our results demonstrate the highest STAT5B mRNA expression in isolated trophoblast cells, lower expression in HTR8/SVneo cells, and the significantly lowest in JAR cells. Moreover, EGF-mediated STAT5 activation increases cell proliferation and viability in both cell lines. The STAT5 knockdown results in significant decrease in cell viability induced by EGF. Only in HTR8/SVneo cells, invasion decreases after STAT5 silencing and this effect cannot be rescued by further addition of EGF. These results demonstrate that STAT5 activated by EGF constitutes an important cascade for the regulation of cell proliferation and invasion in trophoblast cells.

Actin filament-associated protein 1 is required for cSrc activity and secretory activation in the lactating mammary gland

Actin filament-associated protein 1 (AFAP1) is an adaptor protein of cSrc that binds to filamentous actin and regulates the activity of this tyrosine kinase to affect changes to the organization of the actin cytoskeleton. In breast and prostate cancer cells, AFAP1 has been shown to regulate cellular responses requiring actin cytoskeletal changes such as adhesion, invadopodia formation and invasion. However, a normal physiologic role for AFAP1 has remained elusive. In this study, we generated an AFAP1 knockout mouse model that establishes a novel physiologic role for AFAP1 in lactation. Specifically, these animals displayed a defect in lactation that resulted in an inability to nurse efficiently. Histologically, the mammary glands of the lactating knockout mice were distinguished by the accumulation of large cytoplasmic lipid droplets in the alveolar epithelial cells. There was a reduction in lipid synthesis and the expression of lipogenic genes without a corresponding reduction in the production of β-casein, a milk protein. Furthermore, these defects were associated with histologic and biochemical signs of precocious involution. This study also demonstrated that AFAP1 responds to prolactin, a lactogenic hormone, by forming a complex with cSrc and becoming tyrosine phosphorylated. Taken together, these observations pointed to a defect in secretory activation. Certain characteristics of this phenotype mirrored the defect in secretory activation in the cSrc knockout mouse, but most importantly, the activity of cSrc in the mammary gland was reduced during early lactation in the AFAP1-null mouse and the localization of active cSrc at the apical surface of luminal epithelial cells during lactation was selectively lost in the absence of AFAP1. These data define, for the first time, the requirement of AFAP1 for the spatial and temporal regulation of cSrc activity in the normal breast, specifically for milk production.

Comparative studies to evaluate relative in vitro potency of luteolin in inducing cell cycle arrest and apoptosis in HaCaT and A375 cells

Luteolin is a naturally occurring flavonoid present in many plants with diverse applications in pharmacology. Despite several studies elucidating its significant anti-cancer activity against various cancer cells, the mechanism of action in skin cancer is not well addressed. Hence, we investigated the effects of luteolin in HaCaT (human immortalized keratinocytes) and A375 (human melanoma) cells. The radical scavenging abilities of luteolin were determined spectrophotometrically, prior to a cytotoxic study (XTT assay). Inhibitory effects were assessed by colony formation assay. Further, the capability of luteolin to induce cell cycle arrest and apoptosis were demonstrated by flow cytometry and cellular DNA fragmentation ELISA, respectively. The results revealed that luteolin possesses considerable cytotoxicity against both HaCaT and A375 cells with IC50 values of 37.1 μM and 115.1 μM, respectively. Luteolin also inhibited colony formation and induced apoptosis in a dose and time-dependent manner by disturbing cellular integrity as evident from morphological evaluation by Wright- Giemsa staining. Accumulation of cells in G2/M (0.83-8.14%) phase for HaCaT cells and G0/G1 (60.4-72.6%) phase for A375 cells after 24 h treatment indicated cell cycle arresting potential of this flavonoid. These data suggest that luteolin inhibits cell proliferation and promotes cell cycle arrest and apoptosis in skin cancer cells with possible involvement of programmed cell death, providing a substantial basis for it to be developed into a potent chemopreventive template for skin cancer.

Apoptosis-associated tyrosine kinase 1 inhibits growth and migration and promotes apoptosis in melanoma

Apoptosis-associated tyrosine kinase 1 (AATK1) was initially identified as a protein that was dramatically overexpressed during growth arrest and apoptosis of 32Dcl myeloblastic leukemia cells. AATK is expressed in different regions of the brain and may have a role in normal nervous system development by its dual functions of enhancing apoptosis of mature granule cells and promoting terminal neuronal differentiation of developing neurons. However, its function in cancer has never been studied. Melanoma is a tumor composed of transformed cells within the melanocyte lineage deriving from the embryonic neural crest. It has been shown that developmental pathways in neural crest cells have a direct bearing on melanoma formation and human metastatic melanoma cells express a dedifferentiated phenotype. We found that the expression levels of AATK are lower in metastatic melanoma cell lines compared with primary melanoma cell lines and normal human melanocytes. We found that depletion of AATK mRNA in metastatic melanoma cell lines enhanced cell migration in cell line derived from metastatic melanomas. Overexpression of AATK inhibited cell proliferation, colony formation, and promoted apoptosis in melanoma cell lines derived from primary and metastatic melanomas. Signal transduction pathway analysis revealed that Src is involved in regulating AATK. Our results demonstrate for the first time that AATK inhibits cell proliferation, colony formation, and migration, and also promotes apoptosis in melanoma cells.

The inhibition of stat5 by a Peptide aptamer ligand specific for the DNA binding domain prevents target gene transactivation and the growth of breast and prostate tumor cells

The signal transducer and activator of transcription Stat5 is transiently activated by growth factor and cytokine signals in normal cells, but its persistent activation has been observed in a wide range of human tumors. Aberrant Stat5 activity was initially observed in leukemias, but subsequently also found in carcinomas. We investigated the importance of Stat5 in human tumor cell lines. shRNA mediated downregulation of Stat5 revealed the dependence of prostate and breast cancer cells on the expression of this transcription factor. We extended these inhibition studies and derived a peptide aptamer (PA) ligand, which directly interacts with the DNA-binding domain of Stat5 in a yeast-two-hybrid screen. The Stat5 specific PA sequence is embedded in a thioredoxin (hTRX) scaffold protein. The resulting recombinant protein S5-DBD-PA was expressed in bacteria, purified and introduced into tumor cells by protein transduction. Alternatively, S5-DBD-PA was expressed in the tumor cells after infection with a S5-DBD-PA encoding gene transfer vector. Both strategies impaired the DNA-binding ability of Stat5, suppressed Stat5 dependent transactivation and caused its intracellular degradation. Our experiments describe a peptide based inhibitor of Stat5 protein activity which can serve as a lead for the development of a clinically useful compound for cancer treatment.

Variant G6PD levels promote tumor cell proliferation or apoptosis via the STAT3/5 pathway in the human melanoma xenograft mouse model

Background

Glucose-6-phosphate dehydrogenase (G6PD), elevated in tumor cells, catalyzes the first reaction in the pentose-phosphate pathway. The regulation mechanism of G6PD and pathological change in human melanoma growth remains unknown.

Methods

HEM (human epidermal melanocyte) cells and human melanoma cells with the wild-type G6PD gene (A375-WT), G6PD deficiency (A375-G6PD∆), G6PD cDNA overexpression (A375-G6PD∆-G6PD-WT), and mutant G6PD cDNA (A375-G6PD∆-G6PD-G487A) were subcutaneously injected into 5 groups of nude mice. Expressions of G6PD, STAT3, STAT5, cell cycle-related proteins, and apoptotic proteins as well as mechanistic exploration of STAT3/STAT5 were determined by quantitative real-time PCR (qRT-PCR), immunohistochemistry and western blot.

Results

Delayed formation and slowed growth were apparent in A375-G6PD∆ cells, compared to A375-WT cells. Significantly decreased G6PD expression and activity were observed in tumor tissues induced by A375-G6PD∆, along with down-regulated cell cycle proteins cyclin D1, cyclin E, p53, and S100A4. Apoptosis-inhibited factors Bcl-2 and Bcl-xl were up-regulated; however, apoptosis factor Fas was down-regulated, compared to A375-WT cells. Moderate protein expressions were observed in A375-G6PD∆-G6PD-WT and A375-G6PD∆-G6PD-G487A cells.

Conclusions

G6PD may regulate apoptosis and expression of cell cycle-related proteins through phosphorylation of transcription factors STAT3 and STAT5, thus mediating formation and growth of human melanoma cells. Further study will, however, be required to determine potential clinical applications.

[Mechanisms of EGF regulation of COX-2 through the STAT5 signaling pathway in human lung adenocarcinoma A549 cells]

BACKGROUND

It has been proved that cyclooxygenase-2 (COX-2) is a key factor in lung cancer oncogenesis. COX-2 can be induced by a number of cytokines and growth factors and can be regulated by the JAK/STAT signaling pathway. Inhibiting the expression of COX-2 can prevent the development of lung cancer. The aim fo this study is to investigate whether the epidermal growth factor (EGF) can stimulate the signal transducers and activators of transcription 5 (STAT5) as well as to discover the effects of the STAT5 signaling pathway on the COX-2 in human lung adenocarcinoma A549 cells.

METHODS

The phenomenon of STAT5 activation stimulated by the EGF was assayed through immunofluorescence and Western blot. The adenovirus containing the wild-type (WT)-STAT5 (AdWT-STAT5) plasmid, dominant-negative (DN)-STAT5 (Ad-CMV5Stat5aΔ740) plasmid, and STAT5 siRNA were transfected into A549 cells. The latter two groups were stimulated using EGF. Reverse transcriptase polymerase chain reaction was used to detect the mRNA expression of COX-2.

RESULTS

STAT5 was not activated in A549 cells in vitro. EGF stimulation significantly increased the level of the p-STAT5 protein and induces the shuttling of p-STAT5 from the cytoplasm into the nucleus. STAT5 activation was crucial for the COX-2 expression induced by the EGF. STAT5 was required for COX-2 expression, but can mediated the effects of the COX-2 expression through pathways that were independent of transcriptional activation.

CONCLUSIONS

COX-2 expression is dependent on STAT5 phosphorylation. A second pathway does not require STAT5 phosphorylation.

Role of the growth hormone-IGF-1 axis in cancer

A substantial body of evidence supports a role for the growth hormone (GH)-IGF-1 axis in cancer incidence and progression. This includes epidemiological evidence relating elevated plasma IGF-1 to cancer incidence as well as a lack of cancers in GH/IGF-1 deficiency. Rodent models lacking GH or its receptor are strikingly resistant to the induction of a wide range of cancers, and treatment with the GH antagonist pegvisomant slows tumor progression. While GH receptor expression is elevated in many cancers, autocrine GH is present in several types, and overexpression of autocrine GH can induce cell transformation. While the mechanism of autocrine action is not clear, it does involve both STAT5 and STAT3 activation, and probably nuclear translocation of the GH receptor. Development of a more potent GH receptor antagonist or secretion inhibitor is warranted for cancer therapy.

A phase 2 trial of dasatinib in advanced melanoma

BACKGROUND

Inhibiting src kinases (non-receptor tyrosine kinase signaling intermediates) reduces melanoma cell proliferation and invasion. Dasatinib inhibits c-kit, PDGFβR, and EPHA2 and src kinases c-src, c-Yes, Lck, and Fyn. A phase 2 trial of dasatinib in melanoma was conducted to assess response rate (RR), progression-free survival (PFS), and toxicity.

METHODS

Adults with stage 3/4 chemotherapy-naïve unresectable melanoma were eligible. Dasatinib was initially administered at 100 mg twice daily continuously to 17 patients. Due to toxicity, the starting dosage was decreased to 70 mg twice daily. Tumor assessments occurred every 8 weeks.

RESULTS

Thirty-nine patients were enrolled, 36 of whom were evaluable for activity and toxicity. Five, 4, and 3 patients had acral-lentiginous, ocular, or mucosal primaries, respectively. Two patients had confirmed partial responses lasting 64 and 24 weeks (RR 5%). Three patients had minor responses lasting 136, 64, and 28 weeks, and 1 patient who was responding discontinued due to noncompliance. The median PFS was 8 weeks; the 6-month PFS rate was 13%. One patient with an exon-13 c-kit mutation had a partial response, whereas disease in another patient with an exon-11 c-kit mutation progressed. Common toxicities were fatigue, dyspnea, and pleural effusion.

CONCLUSIONS

Daily dasatinib has minimal activity in unselected melanoma patients, excluding those with c-kit mutations. The study did not meet the prespecified endpoints of 30% response rate or 6-month PFS. Dasatinib was poorly tolerated overall, often requiring dose reduction or interruption. Because activity was observed in a small subset without c-kit mutations, identifying predictive biomarkers is important for future development of dasatinib in melanoma alone or in combination trials.

The role of Stat5 transcription factors as tumor suppressors or oncogenes

Stat5 is constitutively activated in many human cancers affecting the expression of cell proliferation and cell survival controlling genes. These oncogenic functions of Stat5 have been elegantly reproduced in mouse models. Aberrant Stat5 activity induces also mitochondrial dysfunction and reactive oxygen species leading to DNA damage. Although DNA damage can stimulate tumorigenesis, it can also prevent it. Stat5 can inhibit tumor progression like in the liver and it is a tumor suppressor in fibroblasts. Stat5 proteins are able to regulate cell differentiation and senescence activating the tumor suppressors SOCS1, p53 and PML. Understanding the context dependent regulation of tumorigenesis through Stat5 function will be central to understand proliferation, survival, differentiation or senescence of cancer cells.

MMP13 mediates cell cycle progression in melanocytes and melanoma cells: in vitro studies of migration and proliferation

Background

Melanoma cells are usually characterized by a strong proliferative potential and efficient invasive migration. Among the multiple molecular changes that are recorded during progression of this disease, aberrant activation of receptor tyrosine kinases (RTK) is often observed. Activation of matrix metalloproteases goes along with RTK activation and usually enhances RTK-driven migration. The purpose of this study was to examine RTK-driven three-dimensional migration of melanocytes and the pro-tumorigenic role of matrix metalloproteases for melanocytes and melanoma cells.

Results

Using experimental melanocyte dedifferentiation as a model for early melanomagenesis we show that an activated EGF receptor variant potentiates migration through three-dimensional fibrillar collagen. EGFR stimulation also resulted in a strong induction of matrix metalloproteases in a MAPK-dependent manner. However, neither MAPK nor MMP activity were required for migration, as the cells migrated in an entirely amoeboid mode. Instead, MMPs fulfilled a function in cell cycle regulation, as their inhibition resulted in strong growth inhibition of melanocytes. The same effect was observed in the human melanoma cell line A375 after stimulation with FCS. Using sh- and siRNA techniques, we could show that MMP13 is the protease responsible for this effect. Along with decreased proliferation, knockdown of MMP13 strongly enhanced pigmentation of melanocytes.

Conclusions

Our data show for the first time that growth stimuli are mediated via MMP13 in melanocytes and melanoma, suggesting an autocrine MMP13-driven loop. Given that MMP13-specific inhibitors are already developed, these results support the evaluation of these inhibitors in the treatment of melanoma.

Gene expression analysis after receptor tyrosine kinase activation reveals new potential melanoma proteins

BACKGROUND

Melanoma is an aggressive tumor with increasing incidence. To develop accurate prognostic markers and targeted therapies, changes leading to malignant transformation of melanocytes need to be understood. In the Xiphophorus melanoma model system, a mutated version of the EGF receptor Xmrk (Xiphophorus melanoma receptor kinase) triggers melanomagenesis. Cellular events downstream of Xmrk, such as the activation of Akt, Ras, B-Raf or Stat5, were also shown to play a role in human melanomagenesis. This makes the elucidation of Xmrk downstream targets a useful method for identifying processes involved in melanoma formation.

METHODS

Here, we analyzed Xmrk-induced gene expression using a microarray approach. Several highly expressed genes were confirmed by realtime PCR, and pathways responsible for their induction were revealed using small molecule inhibitors. The expression of these genes was also monitored in human melanoma cell lines, and the target gene FOSL1 was knocked down by siRNA. Proliferation and migration of siRNA-treated melanoma cell lines were then investigated.

RESULTS

Genes with the strongest upregulation after receptor activation were FOS-like antigen 1 (Fosl1), early growth response 1 (Egr1), osteopontin (Opn), insulin-like growth factor binding protein 3 (Igfbp3), dual-specificity phosphatase 4 (Dusp4), and tumor-associated antigen L6 (Taal6). Interestingly, most genes were blocked in presence of a SRC kinase inhibitor. Importantly, we found that FOSL1, OPN, IGFBP3, DUSP4, and TAAL6 also exhibited increased expression levels in human melanoma cell lines compared to human melanocytes. Knockdown of FOSL1 in human melanoma cell lines reduced their proliferation and migration.

CONCLUSION

Altogether, the data show that the receptor tyrosine kinase Xmrk is a useful tool in the identification of target genes that are commonly expressed in Xmrk-transgenic melanocytes and melanoma cell lines. The identified molecules constitute new possible molecular players in melanoma development. Specifically, a role of FOSL1 in melanomagenic processes is demonstrated. These data are the basis for future detailed analyses of the investigated target genes.

A mutated EGFR is sufficient to induce malignant melanoma with genetic background-dependent histopathologies

Melanoma is a tumor with a very low cure rate once metastasized. Although many genes important for melanoma induction, transformation, and metastasis have been identified, the process of melanomagenesis is only partly understood. Melanoma mediators are easiest to investigate in cell culture models, but animal models are required to evaluate their importance in the context of the whole organism. Here, we describe a transgenic melanoma model in medaka. The oncogenic receptor tyrosine kinase, Xmrk, responsible for melanoma formation in Xiphophorus, was stably expressed under the control of a pigment cell-specific promoter. The transgenic fish developed pigment cell tumors with a penetrance of 100%. The model was used for monitoring the in vivo relevance of several apoptosis and differentiation genes, and for induction of melanoma-relevant signal transduction pathways. We found that Stat5 activation, and Mitf and Bcl-2 levels correlated with a more aggressive stage of the malignancy. Interestingly, different types of pigment cell tumors occurred depending on the genetic background, namely invasive melanoma, uveal melanoma, or exophytic and less aggressive pigment cell tumors called xanthoerythrophoroma. Furthermore, on p53 mutant background, the expression of xmrk led to the appearance of giant focal pigment cell tumors, whereas tumor onset was unchanged compared with wild-type medaka.

A novel small molecule Met inhibitor, PF2362376, exhibits biological activity against osteosarcoma

The receptor tyrosine kinase Met is dysregulated in several human cancers including osteosarcoma (OSA) in which overexpression is a negative prognostic indicator and enforced Met expression in normal osteoblasts leads to genomic instability and malignant transformation. Met is also known to be inappropriately expressed in canine OSA tumour samples and cell lines. The purpose of this study was to evaluate the potential utility of an orally bioavailable small molecule Met inhibitor, PF2362376, against canine OSA cell lines as a prelude to future clinical work. PF2362376 inhibited phosphorylation of Met, Gab-1, Erk and Akt, but not of Src or STAT3. Furthermore, PF2362376 inhibited proliferation of canine OSA cell lines and induced cell death at biologically achievable concentrations. Last, activities associated with Met signalling including migration, invasion, branching morphogenesis and colony formation in soft agar were blocked by PF2362376. These studies support the notion that Met is a relevant target for therapeutic intervention in OSA.

Src activation in melanoma and Src inhibitors as therapeutic agents in melanoma

Src signaling has been implicated in several malignancies including melanoma. The prevalence of Src activation in human melanoma and the effect of the newer Src inhibitors, dasatinib, and bosutinib (SKI-606), as single agents or in combination, on melanoma cell lines is not well established. In the melanoma cell lines, A-375, SK-Mel-5, and SK-Mel-28, activity of Src inhibitors was assessed alone or in combination with standard chemotherapy agents; 50% growth inhibitory concentration was determined by MTS assay and immunoblotting was used to measure Src activation and downstream signaling. Staining for Src activation was measured by Src-phosphotyrosine 416. Immunohistochemistry was performed on primary cutaneous, mucosal, and metastatic melanoma. Src inhibitors blocked the growth of melanoma cell lines; furthermore, Src inhibitor treatment was synergized with cisplatin but not temozolomide or paclitaxel. Treatment with dasatanib increased the levels of pS473 Akt in A-375 melanoma cells but not in the other two cell lines. Forty-eight percent (17 of 35) of all melanoma stained weakly, moderately, or strongly for pY416 Src: cutaneous 61% (eight of 13), mucosal 31% (four of 13), metastatic 55% (five of nine). Most positive biopsies stained weakly and only one metastatic melanoma specimen stained strongly for Src-phosphotyrosine 416. pY416 Src is expressed in cutaneous, mucosal, and metastatic melanoma in various degrees. Src inhibitors may be a promising therapy in melanoma, either by themselves or in combination with chemotherapy (especially with platinum compounds) or inhibitors of the Akt/PI3k pathway.

c-Src tyrosine kinase co-associates with and phosphorylates signal transducer and activator of transcription 5b which mediates the proliferation of normal human B lymphocytes

c-Src is the normal human cellular protein homologue of the viral oncogene v-src. c-Src activity was reported recently to increase in CD40-activated human B lymphocytes, suggesting its involvement in proliferation. To elucidate the exact role of c-Src in this process, we investigated the effects of c-Src over-expression on normal B lymphocyte growth. B lymphocytes purified from human peripheral blood were infected with Ad5/F35 vector encoding either a constitutively active c-Src (c-Src/dominant-positive) or a dominant-negative c-Src (c-Src/DN). Little variation of B lymphocytes expansion could be observed between control enhanced yellow fluorescent protein and c-Src/dominant-positive-infected cells. In contrast, over-expression of c-Src/DN results in a 40% inhibition of B lymphocyte expansion. These results suggest that DN c-Src may compete with endogenous c-Src, resulting in partial inhibition of a transcriptional pathway involved in B lymphocyte proliferation. We demonstrate further that c-Src can phosphorylate signal transducer and activator of transcription 5b (STAT5b) on tyrosine 699 and that c-Src and STAT5b co-associate during B lymphocyte proliferation. These results confirm an important role for c-Src in the expansion of normal human B lymphocytes in vitro, in which c-Src may regulate STAT5b in the intracellular signalling pathway important for the proliferation of normal human B lymphocytes.

Effects of high-dose IFNalpha2b on regional lymph node metastases of human melanoma: modulation of STAT5, FOXP3, and IL-17

PURPOSE

Signal transducer and activator of transcription 5 (STAT5) and STAT3 oppose one another in regulation of the reciprocal development of CD4+CD25+FOXP3+ regulatory T cells (Treg) and T helper 17 (Th17). A reduction in STAT3 is associated with up-regulation of Treg, and STAT5 activation promotes Treg differentiation or function while constraining Th17 generation. The effects of IFNalpha on STAT signaling in relation to tumor tissue Treg and Th17 have not been documented in humans beyond the observations that IFNalpha2b down-regulates STAT3.

EXPERIMENTAL DESIGN

Following diagnostic biopsy and before definitive surgery, 20 doses of high-dose IFNalpha2b (HDI) were administered to patients with stage IIIB melanoma who gave written informed consent. Lymph node biopsies, in which both total STAT3 and phosphorylated STAT3 were down-regulated by HDI, were probed with STAT5, FOXP3, CD4, and interleukin 17 (IL-17) with immunohistochemistry and/or immunofluorescence techniques.

RESULTS

The percentage of FOXP3+ lymphocytes determined by immunohistochemistry was up-regulated from 3.06 +/- 0.65% to 9.86 +/- 1.27% (n = 13, P = 0.0002), and this observation was confirmed by immunofluorescence evaluation of CD4+FOXP3+ Tregs. HDI induced STAT5 up-regulation (five cases observed) in melanoma cells and lymphocytes but did not induce the generation of IL-17-expressing lymphocytes. Increased STAT5 expression was associated with increased FOXP3 expression among lymphocytes, and STAT5 was constitutively activated among both melanoma cells and lymphocytes.

CONCLUSION

IFNalpha2b up-regulates STAT5 and down-regulates STAT3, in conjunction with up-regulation of Treg and inhibition of IL-17-expressing lymphocytes in melanoma tissues. These findings suggest that the effects of IFNalpha may be potentiated through interference with the response of Tregs and/or STAT5.

Oncogene activation in melanocytes links reactive oxygen to multinucleated phenotype and senescence

Contrary to malignant melanoma, nevi are a benign form of melanocytic hyperproliferation. They are frequently observed as precursor lesions of melanoma, but they also feature biochemical markers of senescence. In particular, evidence for oncogene-induced melanocyte senescence as natural means to prevent tumorigenesis has been obtained in nevi with mutated B-Raf(V600E). Here, we demonstrate that strong oncogenic growth factor receptor signalling drives melanocytes into senescence, whereas weaker signals keep them in the proliferative state. Activation of oncogene-induced senescence also produces multinucleated giant cells, a long known histological feature of nevus cells. The protein levels of the senescence mediators, p53 and pRB, and their upstream activators do not correlate with senescence. However, strong oncogene signalling leads to pronounced reactive oxygen stress, and scavenging of reactive oxygen species (ROS) efficiently prevents the formation of multinucleated cells and senescence. Similarly, expression of oncogenic N-RAS results in ROS generation, DNA damage and the same multinuclear senescent phenotype. Hence, we identified oncogenic signalling-dependent ROS production as critical mediator of the melanocytic multinuclear phenotype and senescence, both of them being hallmarks of human nevus cells.

Src regulates cell cycle protein expression and renal epithelial cell proliferation via PI3K/Akt signaling-dependent and -independent mechanisms

Our recent studies showed that Src family kinases (SFKs) are important mediators of proliferation in renal proximal tubular cells (RPTC). In this study, we elucidate the signaling mechanisms that mediate SFK regulation of cell proliferation and cycle protein expression, and identify the SFK member responsible for these responses in a mouse RPTC line. Akt, a target of phosphoinositide-3-kinase (PI3K), and ERK1/2 were constitutively phosphorylated in RPTC cultured in the presence of serum. While treatment of cells with PP1, a specific SFK inhibitor, completely blocked phosphorylation of ERK1/2 and Akt, only inhibition of PI3K/Akt resulted in decreased RPTC proliferation. Incubation of cells with PP1 decreased cyclin D1 expression, decreased p27 and p57 phosphorylation, and increased p27 and p57 expression, two cyclin-dependent kinase inhibitors. Inhibition of the PI3K pathway decreased expression of cyclin D1 without altering expression of p27 and p57. In contrast, PP1 and PI3K inhibition had no effect on cyclin E and p21. Although RPTC expressed Src, Fyn, and Lyn, only siRNA-mediated knockdown of Src decreased RPTC proliferation, decreased cyclin D1 expression, and increased p27 and p57 expression. These data reveal that Src is a crucial mediator of RPTC proliferation and Src-mediated proliferation is associated with PI3K-dependent upregulation of cyclin D1 and PI3K-independent downregulation of p27 and p57.

In vivo identification of novel STAT5 target genes

STAT5A and STAT5B proteins belong to the family of signal transducers and activators of transcription. They are encoded by two separate genes with 91% identity in their amino acid sequences. Despite their high degree of conservation, STAT5A and STAT5B exert non-redundant functions, resulting at least in part from differences in target gene activation. To better characterize the differential contribution of STAT5A and STAT5B in gene regulation, we performed single or double knockdown of STAT5A and STAT5B using small interfering RNA. Subsequent gene expression profiling and RT-qPCR analyses of IL-3-stimulated Ba/F3-β cells led to the identification of putative novel STAT5 target genes. Chromatin immunoprecipitation assays analyzing the corresponding gene loci identified unusual STAT5 binding sites compared to conventional STAT5 responsive elements. Some of the STAT5 targets identified are upregulated in several human cancers, suggesting that they might represent potential oncogenes in STAT5-associated malignancies.