The Src signaling pathway: a potential target in melanoma and other malignancies

Phytoconstituent-derived zingerone nanoparticles disrupt the cell adhesion mechanism and suppress cell motility in melanoma B16F10 cells

Combining phytochemicals and nanotechnology to improve the unfavorable innate properties of phytochemicals and develop them into potent nanomedicines to enhance antitumor efficacy has become a novel strategy for cancer chemoprevention. Melanoma is the most aggressive, metastatic, and deadly disease of the primary cutaneous neoplasms. In this study, we fabricated phytoconstituent-derived zingerone nanoparticles (NPs) and validated their effects on cell adhesion and motility in melanoma B16F10 cells. Our data indicated that zingerone NPs significantly induced cytotoxicity and anti-colony formation and inhibited cell migration and invasion. Moreover, zingerone NPs dramatically interfered with the cytoskeletal reorganization and markedly delayed the period of cell adhesion. Our results also revealed that zingerone NPs-mediated downregulation of MMPs (matrix metalloproteinases) activity is associated with inhibiting cell adhesion and motility. We further evaluated the effects of zingerone NPs on Src/FAK /Paxillin signaling, our data showed that zingerone NPs significantly inhibited the protein activities of Src, FAK, and Paxillin, indicating that they play important roles in zingerone NP-mediated anti-motility and anti-invasion in melanoma cells. Accordingly, the phytoconstituent-zingerone NPs can strengthen the inhibition of tumor growth, invasion, and metastasis in malignant melanoma. Altogether, these multi-pharmacological benefits of zingerone NPs will effectively achieve the purpose of melanoma prevention and invasion inhibition.

N- and s-substituted Pyrazolopyrimidines: A promising new class of potent c-Src kinase inhibitors with prominent antitumor activity

In this work, readily achievable synthetic pathways were utilized for construction of a library of N/S analogues based on the pyrazolopyrimidine scaffold with terminal alkyl or aryl fragments. Subsequently, we evaluated the anticancer effects of these novel analogs against the proliferation of various cancer cell lines, including breast, colon, and liver lines. The results were striking, most of the tested molecules exhibited strong and selective cytotoxic activity against the MDA-MB-231 cancer cell line; IC50 1.13 µM. Structure-activity relationship (SAR) analysis revealed that N-substituted derivatives generally enhanced the cytotoxic effect, particularly with aliphatic side chains that facilitated favorable target interactions. We also investigated apoptosis, DNA fragmentation, invasion assay, and anti-migration effects, and discussed their underlying molecular mechanisms for the most active compound 7c. We demonstrated that 7c N-propyl analogue could inhibit MDA-MB-231 TNBC cell proliferation by inducing apoptosis through the regulation of vital proteins, namely c-Src, p53, and Bax. In addition, our results also revealed the potential of these compounds against tumor metastasis by downregulating the invasion and migration modes. Moreover, the in vitro inhibitory effect of active analogs against c-Src kinase was studied and proved that might be the main cause of their antiproliferative effect. Overall, these compelling results point towards the therapeutic potential of these derivatives, particularly those with N-substitution as promising candidates for the treatment of TNBC type of breast cancer.

Src inhibition induces mitotic arrest associated with chromosomal passenger complex

The non-receptor tyrosine kinase Src plays a key role in cell division, migration, adhesion, and survival. Src is overactivated in several cancers, where it transmits signals that promote cell survival, mitosis, and other important cancer hallmarks. Src is therefore a promising target in cancer therapy, but the underlying mechanisms are still uncertain. Here we show that Src is highly conserved across different species. Src expression increases during mitosis and is localized to the chromosomal passenger complex. Knockdown or inhibition of Src induces multipolar spindle formation, resulting in abnormal expression of the Aurora B and INCENP components of the chromosomal passenger complex. Molecular mechanism studies have found that Src interacts with and phosphorylates INCENP. This then leads to incorrect chromosome arrangement and segregation, resulting in cell division failure. Herein, Src and chromosomal passenger complex co-localize and Src inhibition impedes mitotic progression by inducing multipolar spindle formation. These findings provide novel insights into the molecular basis for using Src inhibitors to treat cancer.

New small molecules in dermatology: for the autoimmunity, inflammation and beyond

OBJECTIVE AND DESIGN

The discovery of new inflammatory pathways and the mechanism of action of inflammatory, autoimmune, genetic, and neoplastic diseases led to the development of immunologically driven drugs. We aimed to perform a narrative review regarding the rising of a new class of drugs capable of blocking important and specific intracellular signals in the maintenance of these pathologies: the small molecules.

MATERIALS/METHODS

A total of 114 scientific papers were enrolled in this narrative review.

RESULTS

We describe in detail the families of protein kinases-Janus Kinase (JAK), Src kinase, Syk tyrosine kinase, Mitogen-Activated Protein Kinase (MAPK), and Bruton Tyrosine Kinase (BTK)-their physiologic function and new drugs that block these pathways of intracellular signaling. We also detail the involved cytokines and the main metabolic and clinical implications of these new medications in the field of dermatology.

CONCLUSIONS

Despite having lower specificity compared to specific immunobiological therapies, these new drugs are effective in a wide variety of dermatological diseases, especially diseases that had few therapeutic options, such as psoriasis, psoriatic arthritis, atopic dermatitis, alopecia areata, and vitiligo.

STAT3 mediates RCP-induced cancer cell invasion through the NF-κB/Slug/MT1-MMP signaling cascade

Rab coupling protein (RCP) has been known to induce cancer invasion and metastasis, and STAT3 is one of major oncogenic factors. In the present study, we identify the critical role of STAT3 in RCP-induced cancer cell invasion. Immunohistochemical data of ovarian cancer tissues presented that levels of RCP expression are closely correlated with those of phospho-STAT3 (p-STAT3). In addition, ovarian cancer patients with high expression of both RCP and p-STAT3 had significantly lower progress-free and overall survival rates compared to those with low either RCP or p-STAT3 expression. Mechanistically, RCP induced STAT3 phosphorylation in both ovarian and breast cancer cells. Silencing or pharmacological inhibition of STAT3 significantly inhibited RCP-induced cancer cell invasion. In addition, we provide evidence that the β1 integrin/EGFR axis is important for RCP-induced STAT3 phosphorylation. Furthermore, STAT3 activated NF-κB for Slug expression that in turn upregulated MT1-MMP expression for cancer cell invasion. Collectively, our present data demonstrate that STAT3 is located downstream of the β1 integrin/EGFR axis and induces Slug and MT1-MMP expression for cancer cell invasion.

SRC tyrosine kinase activates the YAP/TAZ axis and thereby drives tumor growth and metastasis

When properly employed, targeted therapies are effective cancer treatments. However, the development of such therapies requires the identification of targetable drivers of cancer development and metastasis. The expression and nuclear localization of the transcriptional coactivators Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) are increased in many human cancers, and experimental evidence indicates that aberrant YAP or TAZ activation drives tumor formation and metastasis. Although these findings make YAP and TAZ appealing therapeutic targets, both have important functions in adult tissues, so directly targeting them could cause adverse effects. The identification of pathways active in cancer cells and required for YAP/TAZ activity could provide a way to inhibit YAP and TAZ. Here, we show that SRC proto-oncogene, nonreceptor tyrosine kinase (SRC) is an important driver of YAP/TAZ activity in human breast cancer and melanoma cells. SRC activation increased YAP/TAZ activity and the expression of YAP/TAZ-regulated genes. In contrast, SRC inhibition or knockdown repressed both YAP/TAZ activity and the expression of YAP/TAZ-regulated genes. We also show that SRC increases the activity of YAP and TAZ by repressing large tumor suppressor homolog (LATS), and we identify the GTPase-activating protein GIT ArfGAP 1 (GIT1) as an SRC effector that regulates both YAP and TAZ. Importantly, we demonstrate that SRC-mediated YAP/TAZ activity promotes tumor growth and enhances metastasis and that SRC-dependent tumor progression depends, at least in part, on YAP and TAZ. Our findings suggest that therapies targeting SRC could help manage some YAP/TAZ-dependent cancers.

A Targeted Proteomic Approach for Heat Shock Proteins Reveals DNAJB4 as a Suppressor for Melanoma Metastasis

Heat shock proteins are molecular chaperones that are involved in protein folding. In this study, we developed a targeted proteomic method, relying on LC-MS/MS in the parallel-reaction monitoring (PRM) mode, for assessing quantitatively the human heat shock proteome. The method facilitated the coverage of approximately 70% of the human heat shock proteome and displayed much better throughput and sensitivity than the shotgun proteomic approach. We also applied the PRM method for assessing the differential expression of heat shock proteins in three matched primary/metastatic pairs of melanoma cell lines. We were able to quantify ∼45 heat shock proteins in each pair of cell lines, and the quantification results revealed that DNAJB4 is down-regulated in the three lines of metastatic melanoma cells relative to the corresponding primary melanoma cells. Interrogation of The Cancer Genome Atlas data showed that lower levels of DNAJB4 expression conferred poorer prognosis in melanoma patients. Moreover, we found that DNAJB4 suppresses the invasion of cultured melanoma cells through diminished expression and activities of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9). Together, we established, for the first time, a high-throughput targeted proteomics method for profiling quantitatively the human heat shock proteome and discovered DNAJB4 as a suppressor for melanoma metastasis.

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.

YAP/TAZ Activation as a Target for Treating Metastatic Cancer

Yes-Associated Protein (YAP) and Transcriptional Co-activator with PDZ-binding Motif (TAZ) have both emerged as important drivers of cancer progression and metastasis. YAP and TAZ are often upregulated or nuclear localized in aggressive human cancers. There is abundant experimental evidence demonstrating that YAP or TAZ activation promotes cancer formation, tumor progression, and metastasis. In this review we summarize the evidence linking YAP/TAZ activation to metastasis, and discuss the roles of YAP and TAZ during each step of the metastatic cascade. Collectively, this evidence strongly suggests that inappropriate YAP or TAZ activity plays a causal role in cancer, and that targeting aberrant YAP/TAZ activation is a promising strategy for the treatment of metastatic disease. To this end, we also discuss several potential strategies for inhibiting YAP/TAZ activation in cancer and the challenges each strategy poses.

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.

Novel therapeutic approaches in chondrosarcoma

Chondrosarcoma is a malignant tumor of bones, characterized by the production of cartilage matrix. Due to lack of effective treatment for advanced disease, the clinical management of chondrosarcomas is exceptionally challenging. Current research focuses on elucidating the molecular events underlying the pathogenesis of this rare bone malignancy, with the goal of developing new molecularly targeted therapies. Signaling pathways suggested to have a role in chondrosarcoma include Hedgehog, Src, PI3k-Akt-mTOR and angiogenesis. Mutations in IDH1/2, present in more than 50% of primary conventional chondrosarcomas, make the development of IDH inhibitors a promising treatment option. The present review discusses the preclinical and early clinical data on novel targeted therapeutic approaches in chondrosarcoma.

Naringin suppresses the metabolism of A375 cells by inhibiting the phosphorylation of c-Src

Elevation of glycolysis, increase in lactic acid production, and enhancement of mitochondrial biogenesis are all the changes of energy metabolism of melanoma cells. Melanoma cells' metabolism and energy production networks play an important role in cancer proliferation, survival, motility, invasiveness, metastasis, and angiogenesis. Since the Warburg theory was put forward in the 1930s, more researchers focus on finding new ways for effectively eliminating cancer cells by targeting their energy metabolism. In this study, we found naringin has the inhibitory effects on the glucose metabolism of A375 cells, a melanoma cell line, in a concentration-dependent manner. We also found that naringin could significantly reduce the phosphorylation of c-Src. In summary, we demonstrated that naringin inhibits the malignant phenotype of A375 cells by suppressing c-Src and its downstream signaling pathway. More importantly, we provide the novel mechanism that, as a natural inhibitor of c-Src, naringin could be an effective candidate for the treatment of melanoma.

Peroxiredoxin 6 triggers melanoma cell growth by increasing arachidonic acid-dependent lipid signalling

Tumour cells are reported to display an imbalance in the levels of ROS (reactive oxygen species). Frequently, elevated ROS production goes along with compensatory up-regulation of antioxidant enzymes. Accordingly, we found in a previous study that protein levels of several peroxiredoxins, including PRDX6 (peroxiredoxin 6), are highly elevated in experimentally induced melanomas. In the present study, we investigated the functional role of PRDX6 in human melanoma cells. PRDX6 is a bifunctional enzyme, which harbours iPLA2 (Ca(2+)-independent phospholipase A2) activity in addition to its peroxidase function. Our results show that PRDX6 is strongly expressed in most melanoma cells and its expression levels are maintained in a post-transcriptional manner, particularly by EGFR (epidermal growth factor receptor)-dependent signalling. PRDX6 enhances cell viability mainly by enhancing proliferation, which goes along with activation of Src family kinases. Interestingly, we were able to show that the phospholipase activity of the enzyme mediates the pro-proliferative effect of PRDX6. We identified AA (arachidonic acid) as a crucial effector of PRDX6-dependent proliferation and inducer of Src family kinase activation. These results support further the biological importance of the emerging field of lipid signalling in melanoma and highlight the particular functional relevance of PRDX6-dependent phospholipase activity.

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.

Phenotype-driven chemical screening in zebrafish for compounds that inhibit collective cell migration identifies multiple pathways potentially involved in metastatic invasion

In the last decade, high-throughput chemical screening has become the dominant approach for discovering novel compounds with therapeutic properties. Automated screening using in vitro or cultured cell assays have yielded thousands of candidate drugs for a variety of biological targets, but these approaches have not resulted in an increase in drug discovery despite major increases in expenditures. In contrast, phenotype-driven screens have shown a much stronger success rate, which is why we developed an in vivo assay using transgenic zebrafish with a GFP-marked migrating posterior lateral line primordium (PLLp) to identify compounds that influence collective cell migration. We then conducted a high-throughput screen using a compound library of 2160 annotated bioactive synthetic compounds and 800 natural products to identify molecules that block normal PLLp migration. We identified 165 compounds that interfere with primordium migration without overt toxicity in vivo. Selected compounds were confirmed in their migration-blocking activity by using additional assays for cell migration. We then proved the screen to be successful in identifying anti-metastatic compounds active in vivo by performing orthotopic tumor implantation assays in mice. We demonstrated that the Src inhibitor SU6656, identified in our screen, can be used to suppress the metastatic capacity of a highly aggressive mammary tumor cell line. Finally, we used CRISPR/Cas9-targeted mutagenesis in zebrafish to genetically validate predicted targets of compounds. This approach demonstrates that the migrating PLLp in zebrafish can be used for large-scale, high-throughput screening for compounds that inhibit collective cell migration and, potentially, anti-metastatic compounds.

Summary: We have developed a phenotype-driven screen for identifying new inhibitors of collective cell migration and demonstrated the screen can successfully identify compounds active in vivo and potentially new pathways for targeting cancer metastasis.

Antitumor activity of miR-1280 in melanoma by regulation of Src

MicroRNAs (miRNAs) play a key role in cancer progression by coordinately repressing target genes involved in cell proliferation, migration, and invasion. miRNAs regulate gene expression by repressing translation or directing sequence-specific degradation of complementary mRNA. Here, we report that expression of miR-1280 is significantly suppressed in human melanoma specimens when compared with nevi, and in human melanoma cell lines when compared with cultured normal human melanocytes. The proto-oncogene Src was identified as a target of miR-1280 action. Levels of Src expression were significantly higher in melanoma samples and cell lines than in nevi and normal melanocytes. miR-1280 overexpression significantly suppressed the luciferase activity of reporter plasmids containing the full-length 3' untranslated region of Src. miR-1280-mediated suppression of Src led to substantial decreases in melanoma cell proliferation, cell cycle progression, invasion, as well as induced melanoma cell apoptosis. The effects of miR-1280 overexpression on melanoma cell proliferation and growth were reversed by Src overexpression. Intratumoral delivery of miR-1280 significantly suppressed melanoma cell growth in vivo. Our results demonstrate a novel role for miR-1280 as a tumor suppressor in melanoma, identify the Src signaling pathway as a target of miR-1280 action, and suggest a potential therapeutic role for miR-1280 in melanoma.

A preclinical evaluation of a novel multikinase inhibitor, SKLB-329, as a therapeutic agent against hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a serious life-threatening malignant disease of liver. Molecular targeted therapies are considered a promising strategy for the treatment of HCC. Sorafenib is the first, and so far the only targeted drug approved by the US Food and Drug Administration (FDA) for clinical therapy of HCC. Despite being effective in some HCC patients, some demerits of sorafenib in the treatment of HCC, such as modest survival benefits, and drug resistance, have also been reported, which highlights the unmet medical need among patients with HCC. Here, we report a novel multikinase inhibitor discovered by us, SKLB-329, which potently inhibits angiogenesis-related kinases including VEGFR1/2/3, and FGFR2, and the Src kinase. SKLB-329 significantly inhibited endothelial cell growth, migration, invasion and tube formation. It showed potent anti-angiogenic activity in a transgenic zebrafish model. Moreover, SKLB-329 could efficiently restrain the proliferation of HCC cells through down-regulation of Src-mediated FAK and Stat3 activity. In vivo, oral administration of SKLB-329 considerably suppressed the tumor growth in HCC xenograft models (HepG2 and SMMC7721) in a dose-dependent manner. In all of the in vitro and in vivo assays of this investigation, sorafenib was used as a positive control, and in most assays SKLB-329 exhibited a higher potency compared with the positive control. In addition, SKLB-329 also bears favorable pharmacokinetic properties. Collectively, the results of preclinical studies presented here demonstrate that SKLB-329 is a promising drug candidate for HCC treatment.

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.

SRC family kinase inhibition as a novel strategy to augment melphalan-based regional chemotherapy of advanced extremity melanoma

BACKGROUND

Src kinase inhibition has been shown to augment the efficacy of chemotherapy. Dasatinib, a dual Src/Abl kinase inhibitor approved for the treatment of CML, is under investigation as monotherapy for tumors with abnormal Src signaling, such as melanoma. The goal of this study was to determine if Src kinase inhibition using dasatinib could enhance the efficacy of regionally administered melphalan in advanced extremity melanoma.

METHODS

The mutational status of c-kit and patterns of gene expression predictive of dysregulated Src kinase signaling were evaluated in a panel of 26 human melanoma cell lines. The effectiveness of dasatinib was measured by quantifying protein expression and activation of Src kinase, focal adhesion kinase, and Crk-associated substrate (p130(CAS)), in conjunction with in vitro cell viability assays using seven melanoma cell lines. Utilizing a rat model of regional chemotherapy, we evaluated the effectiveness of systemic dasatinib in conjunction with regional melphalan against the human melanoma cell line, DM443, grown as a xenograft.

RESULTS

Only the WM3211 cell line harbored a c-kit mutation. Significant correlation was observed between Src-predicted dysregulation by gene expression and sensitivity to dasatinib in vitro. Tumor doubling time for DM443 xenografts treated with systemic dasatinib in combination with regional melphalan (44.8 days) was significantly longer (p = 0.007) than either dasatinib (21.3 days) or melphalan alone (24.7 days).

CONCLUSIONS

Systemic dasatinib prior to melphalan-based regional chemotherapy markedly improves the efficacy of this alkylating agent in this melanoma xenograft model. Validation of this concept should be considered in the context of a regional therapy clinical trial.

Genetic and epigenetic loss of microRNA-31 leads to feed-forward expression of EZH2 in melanoma

MicroRNAs (miRs) play a key role in cancer etiology by coordinately repressing numerous target genes involved in cell proliferation, migration and invasion. The genomic region in chromosome 9p21 that encompasses miR-31 is frequently deleted in solid cancers including melanoma; however the expression and functional role of miR-31 has not been previously studied in melanoma. Here, we queried the expression status and performed functional characterization of miR-31 in melanoma tissues and cell lines. We found that down-regulation of miR-31 was a common event in melanoma tumors and cell lines and was associated with genomic loss in a subset of samples. Down-regulation of miR-31 gene expression was also a result of epigenetic silencing by DNA methylation, and via EZH2-mediated histone methylation. Ectopic overexpression of miR-31 in various melanoma cell lines inhibited cell migration and invasion. miR-31 targets include oncogenic kinases such as SRC, MET, NIK (MAP3K14) and the melanoma specific oncogene RAB27a. Furthermore, miR-31 overexpression resulted in down-regulation of EZH2 and a de-repression of its target gene rap1GAP; increased expression of EZH2 was associated with melanoma progression and overall patient survival. Taken together, our study supports a tumor suppressor role for miR-31 in melanoma and identifies novel therapeutic targets.

The bone marrow microenvironment in waldenstrom macroglobulinemia

Waldenstrom macroglobulinemia (WM) is a low-grade B-cell lymphoproliferative disorder characterized primarily by specific homing and growth of tumor cells within the bone marrow niches. The progressive growth of tumor cells throughout the bone marrow indicates that the tumor cells are capable of homing and adhering to specific niches that allow growth, survival and drug resistance. In this review we highlight the interaction of the tumor cells in WM and the bone marrow microenvironment including bone marrow stromal cells, endothelial cells and mast cells. Migration, adhesion and downstream activation of signaling pathways leads to cell trafficking and cell dissemination in WM. Future therapeutic agents need to target not only the tumor clone, but also its close interaction with the bone marrow microenvironment.

Dasatinib inhibits primary melanoma cell proliferation through morphology-dependent disruption of Src-ERK signaling

New strategies for the treatment of advanced melanoma are urgently required. The RAS/RAF/MAPK pathway and c-Src are deregulated in the majority of malignant melanomas, suggesting that they may interact functionally and are involved in the development and progression of the malignancy. Preclinical studies have demonstrated variable inhibition of melanoma cell growth by dasatinib in vitro. Src may act through different downstream signaling pathways. In the present study, we demonstrate that dasatinib induces changes in cell morphology, characterized by an arborized and contracted appearance, and accompanied by a reduction in cell proliferation in primary melanoma cells. This morphological change is demonstrated to be associated with the inhibition of nuclear translocation of activated ERK1/2. Together, these results indicate that Src may promote cell proliferation through the activation of the ERK signaling pathway in melanoma oncogenesis.

Functional analysis of GNG2 in human malignant melanoma cells

BACKGROUND

Previous studies have revealed that heterotrimeric G protein is composed of a Gα-subunit and a Gβγ-dimer and is correlated with c-Src and AKT activities. Our recent study showed reduced G protein γ2 subunit (Gng2/GNG2) expression levels in malignant melanoma cells compared with those in benign melanocytic cells in both mice and humans. At present, however, there is no evidence showing an effect of Gng2/GNG2 alone on cancer biology.

OBJECTIVE

The purpose of this study was to examine the biological significance of GNG2 in human malignant melanoma cells.

METHODS

Levels of proliferation and activities of signal transduction molecules were examined in both GNG2-overexpressed and -depleted human malignant melanoma cells.

RESULTS

Proliferation of GNG2-overexpressed SK-Mel28 human malignant melanoma cells was suppressed with decreased c-SRC and AKT activities and increased p21(Cip/WAF1) expression level in vitro. In contrast, proliferation of GNG2-depleted A375P human malignant melanoma cells was enhanced with increased c-SRC and AKT activities and decreased p21(Cip/WAF1) expression level in vitro. In the in vivo experiment, the mean tumor size of GNG2-overexpressed SK-Mel28 cells was less than 1/45th of that of control SK-Mel28 cells in nude mice at 95 days after inoculation.

CONCLUSION

We demonstrated for the first time that increased protein expression level of GNG2 alone inhibits proliferation of malignant melanoma cells in vitro and in vivo, suggesting that GNG2 could be a novel molecular target for malignant melanoma therapy.

Critical amino acid residues in proteins: a BioMart integration of Reactome protein annotations with PRIDE mass spectrometry data and COSMIC somatic mutations

The reversible phosphorylation of serine, threonine and tyrosine hydroxyl groups is an especially prominent form of post-translational modification (PTM) of proteins. It plays critical roles in the regulation of diverse processes, and mutations that directly or indirectly affect these phosphorylation events have been associated with many cancers and other pathologies. Here, we describe the development of a new BioMart tool that gathers data from three different biological resources to provide the user with an integrated view of phosphorylation events associated with a human protein of interest, the complexes of which the protein (modified or not) is a part, the reactions in which the protein and its complexes participate and the somatic mutations that might be expected to perturb those functions. The three resources used are the Reactome, PRIDE and COSMIC databases. The Reactome knowledgebase contains annotations of phosphorylated human proteins linked to the reactions in which they are phosphorylated and dephosphorylated, to the complexes of which they are parts and to the reactions in which the phosphorylated proteins participate as substrates, catalysts and regulators. The PRIDE database holds extensive mass spectrometry data from which protein phosphorylation patterns can be inferred, and the COSMIC database holds records of somatic mutations found in human cancer cells. This tool supports both flexible, user-specified queries and standard (‘canned’) queries to retrieve frequently used combinations of data for user-specified proteins and reactions. We demonstrate using the Wnt signaling pathway and the human c-SRC protein how the tool can be used to place somatic mutation data into a functional perspective by changing critical residues involved in pathway modulation, and where available, check for mass spectrometry evidence in PRIDE supporting identification of the critical residue.

Database URL:http://www.reactome.org/cgi-bin/mart

Expression and functional role of CRIPTO-1 in cutaneous melanoma

Background:

CRIPTO-1 (CR-1) is involved in the pathogenesis and progression of human carcinoma of different histological origin. In this study we addressed the expression and the functional role of CR-1 in cutaneous melanoma.

Methods:

Expression of CR-1 protein in melanomas and melanoma cell lines was assessed by immunohistochemistry, western blotting and/or flow cytometry. Levels of mRNA were evaluated by real-time PCR. Invasion assays were performed in Matrigel-coated modified Boyden chambers.

Results:

Expression of CR-1 protein and/or mRNA was found in 16 out of 37 primary human cutaneous melanomas and in 12 out of 21 melanoma cell lines. Recombinant CR-1 protein activated in melanoma cells c-Src and, at lesser extent, Smad signalling. In addition, CR-1 significantly increased the invasive ability of melanoma cells that was prevented by treatment with either the ALK4 inhibitor SB-431542 or the c-Src inhibitor saracatinib (AZD0530). Anti-CR-1 siRNAs produced a significant inhibition of the growth and the invasive ability of melanoma cells. Finally, a close correlation was found in melanoma cells between the levels of expression of CR-1 and the effects of saracatinib on cell growth.

Conclusion:

These data indicate that a significant fraction of cutaneous melanoma expresses CR-1 and that this growth factor is involved in the invasion and proliferation of melanoma cells.

A phase I ascending single-dose study of the safety, tolerability, and pharmacokinetics of bosutinib (SKI-606) in healthy adult subjects

PURPOSE

Bosutinib (SKI-606), a dual Src/Abl tyrosine kinase inhibitor, is in clinical development for the treatment of patients with chronic myelogenous leukemia (CML). To support clinical development, we conducted a dose-escalation and food-effect evaluation of safety, tolerability, and pharmacokinetics (PK) of bosutinib in healthy adults.

METHODS

This was a randomized, double-blind, placebo-controlled, single-ascending dose, sequential-group study of oral bosutinib. Subjects randomly received bosutinib 200, 400, 600, and 800 mg with food; 200 and 400 mg without food; or placebo. Plasma concentrations were determined by a liquid chromatography-tandem mass spectrometry assay. Non-compartmental PK analyses were performed, and power models assessed dose linearity.

RESULTS

Of 55 enrolled subjects, 33 (81%) subjects had adverse events (AEs) after receiving bosutinib. Common AEs included diarrhea (39%), nausea (29%), and headache (22%). Bosutinib 200-600 mg with food was safe and well tolerated. Bosutinib exposures (C (max) and AUC) were linear and dose proportional from 200 to 800 mg with food. Absorption was relatively slow; median time to C (max) was 6 h. Apparent volume of distribution (V (z)/F) was 131-214 L/kg, mean apparent clearance (CL/F) was 2.25-3.81 L/h/kg, and mean terminal elimination half-life (t (1/2)) was 32-39 h. Preliminary food effect assessment showed that exposure to bosutinib increased by ~2.52-fold (P = 0.002) for C (max) and ~2.28-fold (P = 0.002) for AUC when 200 mg bosutinib was administered with food compared with administration under fasting conditions; administration of 400 mg bosutinib with food increased AUC by ~1.5-fold (P = 0.037). Approximately 1% of administered dose was excreted in urine.

CONCLUSIONS

Bosutinib 200-600 mg with food was safe and well tolerated. Under fed conditions, bosutinib exposures were linear and dose proportional, and C (max) increased by ~1.5-fold. The t (1/2) supported a once-daily dosing regimen.

2D-DIGE analysis of phospho-enriched fractions from dasatinib-treated melanoma cell lines

Current therapeutic regimes for metastatic melanoma have failed to provide robust clinical responses. Dasatinib has shown anti-proliferative and anti-invasive effects in vitro; however, not all melanoma cells tested were sensitive to dasatinib. We used 2D-DIGE analysis of phospho-enriched fractions to identify phosphoproteins involved in regulating response to dasatinib in an isogenic pair of melanoma cell lines, one sensitive to dasatinib (WM-115) and the other resistant (WM-266-4). In WM-115 cells treated with dasatinib, 18 unique protein species with altered phosphorylation levels were detected. Dasatinib treatment of WM-266-4 cells resulted in phosphoprotein alterations to four unique protein species. Four phosphorylated forms of Annexin-A2 (ANXA2) were increased in WM-115 cells treated with dasatinib, whilst dasatinib treatment did not alter ANXA2 phosphoprotein levels in WM-266-4 cells. Immunoblotting confirmed that phosphorylation of ANXA2, on tyrosine residues, was increased in WM-115 cells treated with dasatinib. Subsequent knockdown of ANXA2 by siRNA significantly inhibited proliferation of WM-115 cells but did not significantly reduce proliferation of WM-266-4 cells. Therefore, ANXA2 plays a role in regulating proliferation in dasatinib-sensitive WM-115 cells and could potentially play a role in sensitivity to dasatinib in melanoma cells.

Effect of ketoconazole on the pharmacokinetics of oral bosutinib in healthy subjects

Bosutinib (SKI-606), a dual inhibitor of Src and Abl tyrosine kinases, is being developed for the treatment of chronic myelogenous leukemia. The effect of coadministration of ketoconazole on the pharmacokinetic (PK) profile of bosutinib was evaluated in an open-label, randomized, 2-period, crossover study. Healthy subjects (fasting) received a single dose of oral bosutinib 100 mg alone and with multiple once-daily doses of oral ketoconazole 400 mg. PK sampling occurred through 96 hours. The least square geometric mean treatment ratios (90% confidence interval [CI]) of C(max(bosutinib+ketoconazole))/C(max(bosutinib alone)), AUC(T(bosutinib+ketoconazole))/AUC(T(bosutinib alone)), and AUC((bosutinib+ketoconazole))/AUC((bosutinib alone)) were assessed. Compared with bosutinib administered alone, coadministration with ketoconazole increased bosutinib C(max) 5.2-fold, AUC(T) 7.6-fold, and AUC 8.6-fold. Ketoconazole coadministration decreased the mean apparent clearance of bosutinib approximately 9-fold and increased the mean (SD) terminal half-life from 46.2 (16.4) hours to 69.0 (29.1) hours. The incidence of adverse events (AEs) was comparable between the 2 treatments. The most common AEs were headache, nausea, and increased blood creatinine. No safety-related discontinuations or serious AEs occurred. These PK results indicate that bosutinib is susceptible to interaction with potent CYP3A4 inhibitors.

Medical therapies for meningiomas

Meningiomas are the most common primary brain tumor in adults. Although the majority of these tumors can be effectively treated with surgery and radiation therapy, an important subset of patients have inoperable tumors, or develop recurrent disease after surgery and radiotherapy, and require some form of medical therapy. There are increasing numbers of studies evaluating various medical therapies but the results remain disappointing. Chemotherapies and hormonal therapies have been generally ineffective, although somatostatin analogues may have therapeutic potential. There is also increasing interest in targeted molecular therapies. Agents inhibiting platelet derived growth factor receptors and epidermal growth factor receptors have shown little efficacy, but molecular agents inhibiting vascular endothelial growth factor receptors appear to have some promise. As with other tumors, advances in the medical therapies for meningiomas will require improved understanding of the molecular pathogenesis of these tumors, more predictive preclinical models, and efficient mechanisms for conducting clinical trials, given the small population of eligible patients.

Phase I safety, pharmacokinetics, and inhibition of SRC activity study of saracatinib in patients with solid tumors

PURPOSE

This dose-escalation study evaluated the safety, tolerability, and pharmacokinetics (PK) of the oral Src inhibitor saracatinib (AZD0530) in patients with advanced solid malignancies. Tumor biopsy samples were taken to investigate the effect of saracatinib on Src activity in tumors.

EXPERIMENTAL DESIGN

Part A of the study followed a multiple-ascending dose design to establish the maximum tolerated dose (MTD) of saracatinib. Part B was a randomized, parallel-group, cohort-expansion phase to further assess tolerated doses. Safety, tolerability, and Src activity (immunohistochemistry and lysate-based methodologies) were assessed after 21 days of once-daily oral dosing. PK was assessed after single and multiple dosing.

RESULTS

In part A, 30 patients received once-daily saracatinib at doses of 60 to 250 mg; the MTD was established as 175 mg. In part B, 51 patients were randomized to receive 50 mg (n = 16), 125 mg (n = 16), or 175 mg (n = 19) of saracatinib. The most common grade ≥3 events considered to be treatment related were anemia, diarrhea, and asthenia. Tumor Src activity was reduced following saracatinib treatment. The area under the concentration-time curve and C(max) of saracatinib increased with increasing dose. Saracatinib accumulated 4- to 5-fold on once-daily dosing to reach steady-state exposure after 10 to 17 days of dosing. The half-life was ∼40 hours.

CONCLUSIONS

Saracatinib was well tolerated in patients with advanced solid malignancies. A reduction in tumor Src activity was observed. PK data show that saracatinib is suitable for once-daily oral dosing. Based on this study, the recommended dose for the phase II studies was chosen to be 175 mg/d.

Immunologic consequences of signal transducers and activators of transcription 3 activation in human squamous cell carcinoma

Paracrine cross-talk between tumor cells and immune cells within the tumor microenvironment underlies local mechanisms of immune evasion. Signal transducer and activator of transcription 3 (STAT3), which is constitutively activated in diverse cancer types, is a key regulator of cytokine and chemokine expression in murine tumors, resulting in suppression of both innate and adaptive antitumor immunity. However, the immunologic effects of STAT3 activation in human cancers have not been studied in detail. To investigate how STAT3 activity in human head and neck squamous cell carcinoma (HNSCC) might alter the tumor microenvironment to enable immune escape, we used small interfering RNA and small-molecule inhibitors to suppress STAT3 activity. STAT3 inhibition in multiple primary and established human squamous carcinoma lines resulted in enhanced expression and secretion of both proinflammatory cytokines and chemokines. Although conditioned medium containing supernatants from human HNSCC inhibited lipopolysaccharide-induced dendritic cell activation in vitro, supernatants from STAT3-silenced tumor cells reversed this immune evasion mechanism. Moreover, supernatants from STAT3-silenced tumor cells were able to stimulate the migratory behavior of lymphocytes from human peripheral blood in vitro. These results show the importance of STAT3 activation in regulating the immunomodulatory mediators by human tumors and further validate STAT3 as a promising target for therapeutic intervention.

Small molecules and targeted therapies in distant metastatic disease

Chemotherapy, biological agents or combinations of both have had little impact on survival of patients with metastatic melanoma. Advances in understanding the genetic changes associated with the development of melanoma resulted in availability of promising new agents that inhibit specific proteins up-regulated in signal cell pathways or inhibit anti-apoptotic proteins. Sorafenib, a multikinase inhibitor of the RAF/RAS/MEK pathway, elesclomol (STA-4783) and oblimersen (G3139), an antisense oligonucleotide targeting anti-apoptotic BCl-2, are in phase III clinical studies in combination with chemotherapy. Agents targeting mutant B-Raf (RAF265 and PLX4032), MEK (PD0325901, AZD6244), heat-shock protein 90 (tanespimycin), mTOR (everolimus, deforolimus, temsirolimus) and VEGFR (axitinib) showed some promise in earlier stages of clinical development. Receptor tyrosine-kinase inhibitors (imatinib, dasatinib, sunitinib) may have a role in treatment of patients with melanoma harbouring c-Kit mutations. Although often studied as single agents with disappointing results, new targeted drugs should be more thoroughly evaluated in combination therapies. The future of rational use of new targeted agents also depends on successful application of analytical techniques enabling molecular profiling of patients and leading to selection of likely therapy responders.

Src tyrosine kinase regulates adhesion and chemotaxis in Waldenstrom macroglobulinemia

PURPOSE

Waldenstrom macroglobulinemia is a lymphoplasmacytic lymphoma characterized by widespread involvement of the bone marrow. Despite different options of therapy, Waldenstrom macroglobulinemia is still incurable. Src tyrosine kinase has been shown to play a central role in the regulation of a variety of biological processes, such as cell proliferation, migration, adhesion, and survival in solid tumors. We sought to determine whether the protein tyrosine kinase Src regulates adhesion, migration, and survival in Waldenstrom macroglobulinemia.

EXPERIMENTAL DESIGN

We tested the expression of Src tyrosine kinase in Waldenstrom macroglobulinemia and normal cells, and the effect of the specific Src inhibitor AZD0530 on the adhesion, migration, cell cycle, and survival of a Waldenstrom macroglobulinemia cell line and patient samples. Moreover, we tested the effect of AZD0530 on cytoskeletal and cell cycle signaling in Waldenstrom macroglobulinemia.

RESULTS

We show that Src is overexpressed in Waldenstrom macroglobulinemia cells compared with control B cells, and that the use of the Src inhibitor AZD0530 led to significant inhibition of adhesion, migration, and cytoskeletal signaling induced by SDF1. Moreover, inhibition of Src activity induced G(1) cell cycle arrest; however, it had minimal effect on survival of Waldenstrom macroglobulinemia cells, and no significant effect on survival of normal cells.

CONCLUSIONS

Taken together, these results delineate the role of Src kinase activity in Waldenstrom macroglobulinemia and provide the framework for future clinical trials using Src inhibitors in combination with other drugs to improve the outcome of patients with Waldenstrom macroglobulinemia.

Evaluation of new indole and bromoindole derivatives as pp60(c-Src) tyrosine kinase inhibitors

A series of N-benzyl-indole-3-imine-, amine derivatives and their 5-bromo congeners were synthesized and their biological activity were evaluated against the pp60(c-Src) tyrosine kinase target. To afford the imine derivatives, aldehydes were reacted with substituted benzylamines and the corresponding amine derivatives were obtained by NaBH(4) reduction of these imines. Except insoluble N-benzyl-indole-3-imine derivatives, all the derivatives showed some activity against the kinase target. Screening of these compounds for their biological activity revealed that among N-benzyl-indole derivatives, those bearing 5-bromo substitution have the enhanced potency, where the amine derivatives were more active than imines.

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.

The role of Src in solid tumors

The proto-oncogene c-Src (Src) encodes a nonreceptor tyrosine kinase whose expression and activity are correlated with advanced malignancy and poor prognosis in a variety of human cancers. Nine additional enzymes with homology to Src have been identified and collectively are referred to as Src family kinases (SFKs). Together, SFKs represent the largest family of nonreceptor tyrosine kinases and interact directly with receptor tyrosine kinases, G-protein-coupled receptors, steroid receptors, signal transducers and activators of transcription, and molecules involved in cell adhesion and migration. These interactions lead to a diverse array of biological functions including proliferation, cell growth, differentiation, cell shape, motility, migration, angiogenesis, and survival. Studies investigating mutational activation of Src in human cancers suggest that this may be a rare event and that wild-type Src is weakly oncogenic. Thus, the role of Src in the development and progression of human cancer remains unclear. Recently, it was suggested that increased SFK protein levels and, more importantly, SFK tyrosine kinase activity are linked to cancer progression and metastatic disease by facilitating the action of other signaling proteins. This accumulating body of evidence indicates that SFKs may represent a promising therapeutic target for the treatment of solid tumors. This review discusses the role of SFKs in solid tumors and the recent therapeutic advances aimed at targeting this family of tyrosine kinases in cancer.

Expression and functional analysis of the WAP four disulfide core domain 1 gene in human melanoma

The exact cellular and molecular mechanisms involved in melanoma tumorigenesis remain obscure. Previous gene expression profiling analyses performed upon NHEM and human melanoma samples identified WFDC1 as one of the most frequently down-regulated genes. Here we further showed that NHEM readily express WFDC1 but expression is reduced or completely lost in 80% of the patients-derived melanoma cell lines and tissue samples examined. Furthermore, we show that promoter hypermethylation accounts for the silencing of the WFDC1 gene in 20% of the melanoma cell lines examined. The over-expression of WFDC1 in two metastatic melanoma cell lines, A375 and LOX, resulted in a significant delay of tumor growth in a murine xenograft model, despite a non-significant difference in tumor cell growth in vitro. Gene expression microarray analysis and further expression validation suggests that the Dickkopf-1 (Dkk1) gene is up-regulated in WFDC1 over-expressing cell lines, suggesting that the tumor suppressive function of WFDC1 may be partially a result of up-regulated Dkk1 gene expression, which is known to be a potent inhibitor of the Wnt signaling pathway.

Inhibition of Src family kinases with dasatinib blocks migration and invasion of human melanoma cells

Src family kinases (SFK) are involved in regulating a multitude of biological processes, including cell adhesion, migration, proliferation, and survival, depending on the cellular context. Therefore, although SFKs are currently being investigated as potential targets for treatment strategies in various cancers, the biological responses to inhibition of SFK signaling in any given tumor type are not predictable. Dasatinib (BMS-354825) is a dual Src/Abl kinase inhibitor with potent antiproliferative activity against hematologic malignancies harboring activated BCR-ABL. In this study, we show that dasatinib blocks migration and invasion of human melanoma cells without affecting proliferation and survival. Moreover, dasatinib completely inhibits SFK kinase activity at low nanomolar concentrations in all eight human melanoma cell lines investigated. In addition, two known downstream targets of SFKs, focal adhesion kinase and Crk-associated substrate (p130(CAS)), are inhibited with similar concentrations and kinetics. Consistent with inhibition of these signaling pathways and invasion, dasatinib down-regulates expression of matrix metalloproteinase-9. We also provide evidence that dasatinib directly inhibits kinase activity of the EphA2 receptor tyrosine kinase, which is overexpressed and/or overactive in many solid tumors, including melanoma. Thus, SFKs and downstream signaling are implicated as having key roles in migration and invasion of melanoma cells.

Noninvasive imaging of alphaVbeta3 function as a predictor of the antimigratory and antiproliferative effects of dasatinib

Src family kinases (SFKs) are commonly deregulated in cancer cells. Among other functions, SFKs are critical for cellular migration and invasion. SFK inhibitors are being studied as targeted cancer drugs, but there are no biomarkers for noninvasive assessment of SFK inhibition. The aim of this study was to evaluate whether imaging of alpha(V)beta(3) integrin activity with positron emission tomography (PET) and [(64)Cu]DOTA-cyclo-(Arg-Gly-Asp-dPhe-Lys) {[(64)Cu]DOTA-c(RGDfK)} can be used for monitoring response to the SFK inhibitor dasatinib. Severe combined immunodeficient mice bearing U87MG xenografts were gavaged daily over 72 hours with 72 or 95 mg/kg of dasatinib or vehicle. Tumor uptake of [(64)Cu]DOTA-c(RGDfK) was measured by small-animal PET. In parallel, fluorodeoxyglucose (FDG) scans were performed to assess tumor metabolism in response to dasatinib treatment. Dasatinib significantly (P<0.0001) reduced [(64)Cu]DOTA-c(RGDfK) uptake by up to 59% in U87MG xenografts [2.10+/-0.14% injected dose/gram (ID/g) in the 95 mg/kg group and 3.12+/-0.18% ID/g in the 72 mg/kg group, versus 5.08+/-0.80% ID/g in controls]. In contrast, tumor FDG uptake showed no significant reduction with dasatinib therapy (8.13+/-0.45% ID/g in treated versus 10.39+/-1.04% ID/g in controls; P=0.170). Histologically, tumors were viable at the time of the follow-up PET scan but showed inhibition of focal adhesion kinase. Continued dasatinib treatment resulted in a significant inhibition of tumor growth (tumor size on day 10 of therapy: 21.13+/-2.60 mm(2) in treated animals versus 122.50+/-17.68 mm(2) in controls; P=0.001). [(64)Cu]DOTA-c(RGDfK) may provide a sensitive means of monitoring tumor response to SFK inhibition in alpha(V)beta(3)-expressing cancers early in the course of therapy.

Novel aminomethylindole derivatives as inhibitors of pp60c-Src tyrosine kinase: synthesis and biological activity

The pp60(c-Src) is one of the ubiquitously expressed Src family kinases and has important functions in malignant cells, including regulation of cell division, growth factor signaling, and movement. Therefore, investigating new small molecule inhibitors of pp60(c-Src) is important to discover and develop novel therapeutics for cancer and metastasis. Moreover, some of the small molecule inhibitors that do not qualify for therapeutic use may become very useful tool to explore the role of Src kinase in normal cells as well as in a variety of disease models. Our continuous efforts to find novel inhibitors of pp60(c-Src) aimed for therapeutic and research use, we synthesized newly designed aminomethylindole derivatives as novel small molecule inhibitors and investigated their inhibitory effect on pp60(c-Src) tyrosine kinase. Here, we report one potential inhibitor of the pp60(c-Src) from five active molecules of all nine compounds, which were synthesized and screened for the biological activity of the molecules against pp60(c-Src) target.

Activated stat-3 in melanoma

BACKGROUND

Recent studies have demonstrated that the Src-Stat pathway may play an important role in melanoma. We examined the expression of phosphorylated Stat-3 (pStat-3), activated Stat-1 (pStat-1) and interferon alpha receptor subunit 1(IFNAR-1) in human melanocytic neoplasms.

METHODS

Compound nevi (6), dysplastic nevi (4), congenital nevi (2), primary melanoma (14), and sentinel lymph node metastasis (40) were examined. Specimens were evaluated for phospho-Stat-1 (pStat-1), phospho-Stat-3 (pStat-3), and IFNAR-1 by immunohistochemistry. Staining was scored from 1 to 3 based on a composite score that took into account both the percentage of tumor cells staining and the intensity of stained cells.

RESULTS

Normal melanocytes or benign nevi expressed little pStat-1, pStat-3, or IFNAR-1. In primary cutaneous melanoma, 6 of 14 skin biopsies showed activated Stat-3. However, in melanoma metastatic to regional lymph nodes, 16 of 26 had activated Stat-3 but only 6 of 23 had activated Stat-1. Melanoma tumors had high levels of either pStat-3 or pStat-1 but not both. All melanoma specimens but not benign melanocytes had cytoplasmic IFNAR-1 staining. An increase in Stat-3 activity was seen in melanoma but not in benign nevi or skin melanocytes. There appeared to be an inverse correlation between the levels of pStat-3 and pStat-1 in a given specimen.

CONCLUSIONS

The relationship between activated Stat-3 and biological behavior of melanocytic lesions observed in this study warrants further exploration.

Preclinical evaluation of dasatinib, a potent Src kinase inhibitor, in melanoma cell lines

BACKGROUND

Metastatic melanoma is a highly chemotherapy resistant tumour. The use of newer targeted therapies alone and in combination with chemotherapy may offer new hope of improving response to treatment. Dasatinib, a multi-target kinase inhibitor, is currently approved for the treatment of chronic myeloid leukaemia and has shown promising results in preclinical studies in a number of solid tumours.

METHODS

We examined the effects of dasatinib on proliferation, chemo-sensitivity, cell cycle arrest, apoptosis, migration and invasion in human melanoma cell lines. Expression and activation of Src kinase, FAK and EphA2 were also examined in the melanoma cells.

RESULTS

Dasatinib inhibited growth of three of the five melanoma cell lines. Comparison with sorafenib showed that in these three cell lines dasatinib inhibited growth at lower concentrations than sorafenib. Dasatinib in combination with the chemotherapy drug temozolomide showed greater efficacy than either drug alone. Dasatinib induced cell cycle arrest and apoptosis and significantly inhibited cell migration and invasion of melanoma cells. Dasatinib inhibition of proliferation was associated with reduced phosphorylation of Src kinase, while decreased phosphorylation of FAK was implicated in dasatinib-mediated inhibition of migration and invasion in melanoma cells.

CONCLUSION

Dasatinib has both anti-proliferative and anti-invasive effects in melanoma cells and combined with chemotherapy may have clinical benefit in the treatment of malignant melanoma.

Impact of IFNalpha2b upon pSTAT3 and the MEK/ERK MAPK pathway in melanoma

PURPOSE

High-dose IFNalpha2b (HDI) was established as the first effective adjuvant therapy for patients with high-risk resected melanoma more than a decade ago, but its fundamental molecular mechanism of action remains unclear. STAT3 and the mitogen activated protein kinases (MAPKs), especially ERK (extracellular signal-regulating kinase) and MEK (MAPK/ERK kinase), play roles in melanoma progression and host immunity. We have therefore evaluated STAT3 and MEK/ERK MAP kinases in patients with regional lymph node metastasis (stage IIIB) of melanoma in the context of a prospective neoadjuvant trial of HDI (UPCI 00-008).

PATIENTS AND METHODS

In the context of this trial, HDI was administered daily for 20 doses following diagnostic biopsy, and prior to definitive surgery. Immunohistochemistry for pSTAT3, phospho-MEK1/2, phospho-ERK1/2, and EGFR was performed on paired fixed (nine patients) biopsies.

RESULTS

HDI was found to down-regulate pSTAT3 (P = 0.008) and phospho-MEK1/2 (P = 0.008) levels significantly in tumor cells. Phospho-ERK1/2 was down-regulated by HDI in tumor cells (P = 0.015), but not in lymphoid cells. HDI down-regulated EGFR (P = 0.013), but pSTAT3 activation appeared not to be associated with EGFR expression and the MEK/ERK MAPK pathway.

CONCLUSION

We conclude that HDI regulates MAPK signaling differentially in melanoma tumor cells and host lymphoid cells in vivo. STAT3 activation is independent of the EGFR/MEK/ERK signaling pathway.

Matricellular proteins produced by melanocytes and melanomas: in search for functions

Matricellular proteins are modulators of cell-matrix interactions and cellular functions. The group includes thrombospondin, osteopontin, osteonectin/SPARC, tenascin, disintegrins, galectins and CCN proteins. The production of matricellular proteins such as osteopontin, SPARC or tenascin is highly upregulated in melanoma and other tumors but little is known about their functions in tumor growth, survival, and metastasis. The distribution pattern of CCN3 differs from most other matricellular proteins, such that it is produced abundantly by normal melanocytes, but is not significantly expressed in melanoma cells. CCN3 is known to inhibit melanocyte proliferation and stimulate adhesion to collagen type IV, the main component of the basement membrane. CCN3 has a unique role in securing adhesion of melanocytes to the basement membrane distinct from other melanoma-produced matricellular proteins which act as de-adhesive molecules and antagonists of focal adhesion. Qualitative and quantitative changes in matricellular protein expression contribute to melanoma progression similar to the E-cadherin to N-cadherin class switch, allowing melanoma cells to escape from keratinocyte control.

Ectopic expression of methionine aminopeptidase-2 causes cell transformation and stimulates proliferation

Methionine aminopeptidase-2 (MetAP2) processes N-terminal methionine from nascent cellular proteins. Inhibition of MetAP2 has been shown to block angiogenesis and suppress tumor growth in preclinical tumor models. However, the biological role of MetAP2 in cancer is not well understood. We examined the effect of three distinct chemical classes of MetAP2 inhibitors on the growth of a panel of human cancer cells in vitro. All MetAP2 inhibitors caused inhibition of tumor cell growth in both anchorage-dependent and, particularly, in anchorage-independent manner. These data prompted us to examine the possible roles of MetAP2 in cancers. Ectopic expression of MetAP2 in NIH-3T3 cells caused transformation, evidenced by the formation of foci in monolayer culture and growth of large colonies in soft agar. Overexpression of MetAP2 in an immortalized bronchial epithelial cell line NL20 accelerated growth. These phenotypes induced by the overexpression of MetAP2 were reversed by the treatment with MetAP2 inhibitors, indicating that the catalytic function of MetAP2 was essential. Accordingly, overexpression of a catalytically inactive MetAP2 resulted in growth retardation of HT1080 tumor cells, suggesting a dominant-negative role of the inactive MetAP2 mutant. Finally, we analysed the expression of MetAP2 in patient cancer samples by immunohistochemistry. Moderate-to-high staining was identified in the majority of breast, colon, lung, ovarian and prostate carcinomas examined. These data suggest that MetAP2 plays an important role in tumor cell growth and may contribute to tumorigenesis.