| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Tumor Biology |
The Wistar Institute [K. S., G. L., B. V., D. P., M. H.], and Program of Cell and Molecular Biology, Biomedical Graduate Studies, University of Pennsylvania School of Medicine [G. L.], Philadelphia, Pennsylvania 19104
 |
ABSTRACT |
|---|
 Top ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
|
INTRODUCTION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
For normal melanocytes, benign nevus cells, and melanoma cells from the RGP and early VGP stage, IGF-1 is one of the most critical growth factor required for survival and growth of cells in chemically defined media (10 , 11) . IGF-1 or its substitute, insulin, is also a motility factor for melanoma cells (12 , 13) . The receptor for IGF-1 (and insulin), IGF-1R, is expressed by all melanocytic cells, and expression increases with progression (2 , 14 , 15) . Down-regulation of IGF-1R with antisense oligonucleotides inhibits melanoma growth in vivo (16) . Mice transgenic for IGF-1 under a keratin 1 promoter show marked thickening of the dermis and hypodermis, and the skin is more prone to transformation in initiation/promotion protocols (17) , suggesting that the constitutive production of IGF-1 is a critical factor in tumor development and progression. Breast and lung carcinoma cells produce IGF-1 for autocrine stimulation, but the tumor stroma, particularly the fibroblasts, produces IGF-1 for paracrine stimulation (18) . When the ligand binds to IGF-1R, signaling occurs through Ras-dependent phosphorylation of MAP kinase and subsequent activation of nuclear transcription factors (19 , 20) . Phosphorylation of Akt is also induced by IGF-1 in several tumors (21, 22, 23, 24) , suggesting a role for this growth factor as an antiapoptotic survival factor. IGF-1 produced by the tumor cells activates ß3 and ß1 integrins (25 , 26) , increases synthesis of collagen (27) , activates matrix metalloproteinase-9 (28) , and induces production of angiogenic growth factors such as vascular endothelial growth factor (29) . All of these events are intimately associated with aggressive tumor behavior. In melanoma, IGF-1 synthesis by tumor cells is not clear. Thus tumor cells must first activate the fibroblasts in the tumor stroma, which then produce IGF-1 for their stimulation. Activation of the stromal fibroblasts by melanoma cells apparently occurs through PDGF, which is produced by melanoma cells as either PDGF-AA or PDGF-BB (7) . Melanoma cells do not express the receptor for PDGF-B, PDGFR-ß. Thus, PDGF-B appears to be produced by melanoma cells solely for paracrine stimulation of fibroblasts in the tumor stroma.
The purpose of this study was to delineate how IGF-1 can have multiple roles in melanoma progression by acting as a survival, growth, and motility factor. We wanted to determine whether all biological events were the result of activation of the MAP kinase pathway or whether additional pathways played a role. Melanoma cells do not express IGF-1, excluding this growth factor from autocrine stimulation. Although all melanoma cells expressed the IGF-1R, we saw striking differences in the response to IGF-1 when the gene was transduced to 15 melanoma cell lines by an adenoviral vector for gene transfer or when cells were treated with the recombinant protein. Only melanoma cells with biological early malignant characteristics responded to IGF-1. The differences between biologically early and late melanoma cells were that in early cells we found the following distinct mechanisms of stimulation: IGF-1, as expected, activated the MAP kinase pathway for growth stimulation in RGP melanoma and activated PKB/Akt, which led to stabilization of ß-catenin. Activation of the Akt/ß-catenin pathway could be responsible for the increased survival of cells. These results demonstrate the complex and important role for this growth factor for tumor progression in melanoma.
|
MATERIALS AND METHODS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Materials.
IGF-1 and IGF-1R cDNA were provided by Dr. A. Ullrich, (Martinsried, Germany) and have been described previously (31
, 32)
. IGF-1 was detected with a RIA kit from Diagnostic Systems Laboratories (Webster, TX). MAP kinase, phospho-MAP kinase, Akt and phospho-Akt antibodies, and restriction enzymes were from New England Biolabs (Beverly, MA). Antibodies against IGF-1 and IGF-1R were from Santa Cruz Biotechnology Biotechnologies (Santa Cruz, CA). PY20, 4G10, and anti-ß-catenin antibodies were from Transduction Laboratories (Los Angeles, CA). Histone 1B was from Roche Pharmaceuticals (Indianapolis, IN). Tau protein was kindly provided by Dr. Virginia Lee (University of Pennsylvania, Philadelphia, PA). All tissue culture media were from Sigma (St. Louis, MO), except DMEM, which was purchased from Life Technologies (Rockville, MD). PD98059 and Wortmannin were from Calbiochem (San Diego, CA). All radioactive materials were from Amersham Radiochemicals (Arlington Heights, IL).
Immunoprecipitation and Western Analysis.
Immunoprecipitations for the detection of phosphorylated IGF-1R were performed essentially as described previously (33)
. In brief, melanoma cells were maintained in protein-free medium for 24 h before treatment with 50 ng/ml recombinant IGF-1 for 10 min. The cell monolayers were washed with cold PBS containing 1 mM Na3VO4 and rapidly scraped into immunoprecipitation solution, which consisted of 20 mM HEPES (pH 7.5); 150 mM KCl; 0.5% Triton X-100; 1 mM EDTA; 1 mM EGTA; 1 mM Na3VO4; 1 mM NaF; 2 mM Na Pi; 1 µg/ml each of aprotinin, leupeptin, and pepstatin; and 2 mM phenylmethylsulfonyl fluoride. After incubation on ice for 15 min, the extracts were separated by centrifugation at 13,000 x g for 15 min. The supernatants were used for immunoprecipitation with an anti-IGF-1R antibody overnight at 4°C. Immunoprecipitates were collected by a protein A/G mixture coupled to beads for 60 min and washed three times with immunoprecipitation buffer. The beads were suspended in sample-loading buffer, boiled for 3 min, and separated on a 7.5% SDS-polyacrylamide gel. After protein transfer onto PVDF membranes, extracts were probed with PY20 and 4G10 antibodies, and the specific bands were visualized by electrochemiluminescence (Amersham Biotechnologies). To analyze the kinase activities of Akt and GSK-3ß, the melanoma cells were maintained in protein-free medium after infections with the adenoviral vectors for 48 h. Akt kinase assays were performed as described previously (23)
, with rabbit polyclonal antibodies and histone H1B as substrate. GSK-3ß was assayed according to Valentinis et al. (33)
and Hong and Lee (34)
, using an anti-GSK-3ß antibody (Santa Cruz Biotechnology) and Tau protein as the substrate. Autoradiograms were subjected to densitometric analysis and quantified by NIH Image. Western analysis of Akt, phospho-Akt, MAP kinase, and phospho-MAP kinase were performed as follows: cell monolayers were treated with adenoviruses or recombinant IGF-1 for specific time periods and harvested according to conditions described by the manufacturer (New England Biolabs). After separation on 10% SDS-polyacrylamide gels, proteins were transferred onto PVDF membranes and analyzed using specific antibodies according to the manufacturer’s recommendations.
Cell Fractionation and Pulse Chase Analysis of ß-Catenin.
Melanoma cells were maintained in protein-free medium for 24 h and then treated with 50 ng/ml IGF-1 for 30 min. Cells were harvested, and soluble and insoluble fractions were isolated using NP40 as described (22)
. Equal amount of proteins were loaded and separated by 10% SDS-PAGE. Proteins were transferred to PVDF membranes and analyzed using ß-catenin monoclonal antibody as described above. For pulse chase experiments, cells were serum-starved for 24 h and treated with 100 µCi/ml Translabel (NEN Biosciences) for 4 h. The medium was replaced with 10 times the normal amount of methionine and cysteine for 30 min. Subsequently, the cells were treated with IGF-1 and harvested at the indicated times. Whole-cell extracts were prepared using radioimmunoprecipitation assay buffer and counted for radioactivity; protein concentrations were determined, and equal amounts of proteins were separated by 10% SDS-PAGE. The gels were dried and exposed for autoradiography.
[3H]Thymidine Incorporation Assay.
Melanoma cells were seeded at 30,000 cells/well in 96-well plates and infected with adenoviruses or incubated with recombinant proteins or inhibitors for 48 h. The cells were pulsed with 1 µCi/ml [3H]thymidine for 4 h, trypsinized, and harvested using an automatic cell harvester before counting in a beta counter. All experiments were performed in quadruplicate and repeated three times. Neutralization experiments were performed by incubating cells with neutralizing antibodies at 50 µg/ml for the indicated times before harvesting the cells. Trypan blue exclusion tests were used for cell counting assays. For cell survival in suspension experiments, 50,000 cells were plated on poly(HEMA)-coated 6-well plates (35)
. Cells were harvested, counted for viability by trypan blue dye exclusion, and analyzed for apoptosis/cell cycle distribution, using propidium iodide. For this analysis, harvested cells were fixed in 80% ethanol for 1 h, treated with RNase, and stained with propidium iodide (36)
.
Preparation of Adenoviral Vectors.
The recombinant adenovirus, IGF-1/Ad5, was generated by homologous recombination in 293 cells as described previously (37)
. Briefly, full-length cDNA was ligated into the transfer vector pAdCMV. In the plasmids, the full-length cDNA was flanked by a CMV promoter at the 5' end and SV-40 T-antigen intron/polyadenylation signal at the 3' end to form a complete transcriptional unit. Monolayers of 293 cells were transfected with linearized transfer vector along with dl7001 (Ad5 virus lacking E1 and E3 regions), using the CaPO4 precipitation method. The recombinant plaques were identified by Southern analysis and further propagated in 293 cells (37
, 38)
. Large-scale virus preparation was performed using the double CsCl proliferation method. Prior to infection of melanoma cells, the adenoviral vector was titrated in 293 cells to determine the pfu in the virus preparation.
Northern Analysis.
Total RNA from melanoma cell lines was extracted with RNAzol (Molecular Research Center Inc, Cincinnati, OH). Fifteen µg of RNA were separated on a 0.8% formaldehyde-agarose gel and transferred overnight onto a nylon membrane (Micron Separations, Inc., Westborough, MA). Membranes were probed with full-length cDNAs. Prehybridization and hybridizations were carried out in Church buffer at 65°C, and membranes were washed with 2x SSC-0.1% SDS at room temperature for 45 min with three changes. Subsequently, the membranes were washed with 0.1x SSC-0.1% SDS until the background counts were reduced to a minimum. The probes were prepared with a random labeling kit from Roche Pharmaceuticals, using [
-32P]dATP (3000 Ci/mmol).
|
RESULTS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
. The mRNA expression levels varied among cell lines when compared with glyceraldehyde-3-phosphate dehydrogenase controls, with slow-growing cells generally expressing the lower levels. All of 14 cell lines expressed the IGF-1 protein when tested by Western blotting (Fig. 1B)
. When we used a polyclonal antibody for detection, cell lines contained both mature and proforms of the receptor. None of the melanoma cell lines expressed IGF-1 when RNA from the cells was tested by reverse transcription-PCR, nor was protein secretion detected in six cell lines by immunoassays (not shown), suggesting the absence of an autocrine loop for this growth factor in melanoma cells. The stimulation of melanoma cells by IGF-1 was then tested by overexpressing the gene in melanoma cells with an adenoviral vector, using recombinant protein, or by incubating melanoma cells with culture supernatants from fibroblasts transduced with IGF-1. Maximal growth factor production of 300–400 ng/ml in supernatants of 90% confluent RGP primary melanoma cultures was achieved 72 h after transduction (Fig. 2A)
and use of 20 pfu/cell of the adenoviral vector (Fig. 2B)
. Infection levels were toxic to the cells. Secretion levels remained stable for 
8 days until the cells had to be subcultured. Subsequent culturing with proliferation of cells decreased the growth factor levels below detection levels after 3 weeks depending on the growth rate of the cells. Secretion levels of transduced fibroblasts were comparable to those for melanoma cells when the 50% lower cell densities of fibroblasts per culture surface were considered (Fig. 2C)
. The fibroblasts secreted low levels of IGF-1 when transduced with the control vector lacZ.
|
|
. Only RGP primary melanomas and cell lines representing a biologically early VGP primary stage were responsive, whereas all advanced VGP primary or metastatic cell lines were nonresponsive when tested in [3H]thymidine incorporation or cell-counting assays. Responding cell lines were up to 3-fold stimulated (Fig. 3A)
. The MAP kinase kinase inhibitor PD98059 and phosphatidylinositol 3'-kinase inhibitor Wortmannin inhibited stimulation of DNA synthesis by IGF-1 in SBcl2 cells (data not shown). Stimulation of RGP and early VGP primary melanoma cells, but not late VGP and metastatic melanoma cell lines was also achieved with recombinant IGF-1 added to the culture medium (data not shown). Culture supernatants of fibroblasts transduced with the IGF-1 gene (containing 100–200 ng/ml secreted IGF-1; see Fig. 2C
) were mitogenic for responding cell lines, and the mitogenic activity in the supernatant could be blocked with 1 µg of IGF-1R neutralizing antibodies (Fig. 3B)
. Survival of RGP melanomas that were maintained anchorage independently was enhanced after IGF-1 was transduced, whereas control cells showed high death rates within 24 h (Fig. 3C)
.
|
|
. The cells were first treated with recombinant IGF-1. Extracts were then immunoprecipitated with an anti-IGF-1R antibody, and the precipitates were analyzed for phosphorylation of the receptor, using antibodies for phosphorylated tyrosine kinases. Although there were variations in the level of phosphorylated receptor, the results suggest that the IGF-1R on melanoma cells from all stages of progression is functionally active. The effect of IGF-1 on MAP kinase activity in responding and nonresponding melanoma cells was then examined. Melanoma cells transduced for 24–72 h with IGF-1 at 20 pfu/cell of the adenoviral vector and maintained in protein-free medium were then examined for phosphorylation of Erk1 (p44) and Erk2 (p42), using phosphospecific antibodies (Fig. 5)
. At each time point, IGF-1 phosphorylated Erks in the responding RGP melanoma cell line SBcl2 (Fig. 5A)
. The specificity of Erk activation was confirmed by treating cells with PD98059, which abolished Erk phosphorylation (data not shown). Nonresponding cells, whether transduced with IGF-1 or the lacZ control vector, showed the same levels of phosphorylation of MAP kinase, demonstrating that the enzyme in these cells is constitutively active (Fig. 5B)
.
|
|
. The specificity of Akt activation was confirmed by treating cells with Wortmannin, which abolished Akt phosphorylation (data not shown). On the other hand, the activity of GSK-3ß, which is a downstream effector of Akt, differed between growth-responding and -nonresponding cell lines. When melanoma cells were tested for Akt-mediated histone H1B phosphorylation 48 h after IGF-1 transduction, RGP melanoma SBcl2 cells responded with a 4-fold increase whereas the metastatic cells 1205 Lu showed a much smaller increase (Fig. 6B)
. Similarly, when Tau was used as substrate for GSK-3ß, the RGP melanoma cells showed a significant decrease in activity compared with metastatic melanoma cell line (Fig. 6C)
. These results demonstrate that IGF-1 can activate the Akt signaling pathway in RGP melanoma cells but not as much in metastatic cells. Because ß-catenin is a downstream effector molecule of Akt, we then determined whether IGF-1 could modulate translocation and stabilization of ß-catenin. After 30 min of IGF-1 treatment in either responding RGP SBcl2 or nonresponding metastatic 1205 Lu cells, ß-catenin was increasingly localized in the soluble fraction of the RGP but not the metastatic cells (Fig. 7A)
. Pulse chase analysis of ß-catenin in these two cell lines suggested reduced stabilized protein in SBcl2 cells in the absence of IGF-1 and increased half-life after treatment with IGF-1, whereas 1205 Lu cells demonstrated a longer half-life for the protein even in the absence of IGF-1 (Fig. 7B)
. These results suggest that IGF-1, through activation of the Akt pathway, contributes to cell survival by stabilizing ß-catenin.
|
|
|
DISCUSSION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
IGF-1 has previously been described in normal cells as an activator of the MAP kinase pathway (40) . We could confirm this in our studies with melanoma cells. When provided to melanoma cells at supraphysiological levels, IGF-1 can also substitute for the second essential growth factor for melanoma cells, bFGF. We have previously shown that RGP primary melanoma cells require both IGF-1 and bFGF (41) . When bFGF is overexpressed in RGP cells at supraphysiological levels, the cells become independent not only of exogenous bFGF but also of IGF-1 (2 , 5) . As the cells progress to the advanced VGP stage of primary melanoma, they begin producing bFGF constitutively at higher levels and become independent of bFGF and, later, of IGF-1 (2 , 5) . Apparently endogenous bFGF activates the MAP kinase pathway in VGP primary and metastatic cells, constitutively rendering them insensitive to exogenous or endogenous growth factors. Neither exogenous bFGF (5) nor IGF-1 (this study) can stimulate the highly malignant and aggressive cells. The dominant role of bFGF as an autocrine growth factor was underscored by experiments with antisense oligonucleotides. Inhibition of expression of bFGF or its receptor FGFR1 inhibited melanoma growth both in vitro and in vivo (5 , 42) . Whether bFGF can also act as a paracrine growth factor to stimulate fibroblasts and endothelial cells is unclear but is likely based on our gene transfection studies with adenoviral vectors (43 , 44) .
RGP melanoma cells are unable to grow anchorage independently and undergo apoptosis. However, the cells can be rescued by IGF-1, suggesting that IGF-1 is a survival factor for them. Cell survival by IGF-1 is most likely mediated through stimulation of the PKB/Akt pathway or in combination with MAP kinase pathway. It has since been reported that one of the down-stream targets of Akt activation is inactivation by phosphorylation of the proapoptotic protein Bad, which is also a target for inactivation by MAP kinase (22
, 45
, 46)
. Akt activation also resulted in inhibition of GSK-3ß and stabilization of ß-catenin. This dual activation of the MAP kinase and ß-catenin pathways provides the cells with a powerful mechanism to survive during the arduous migration from the cytokine-rich environment of the epidermis to the dermis, in which the normal host cells are more scattered and surrounded by matrix components. The activation of Akt and stabilization of ß-catenin are similar to the activation of the MAP kinase pathway observed in RGP and to a lesser extent in metastatic melanoma cells, suggesting a similar constitutive activation in the more advanced cells. Indeed, ß-catenin has been found constitutively activated in melanoma through point mutations (47)
. It is known that Akt/PKB can act either synergistically or in opposition to the MAP kinase pathway, depending on the cell type and stage of differentiation. Every melanoma cell line can be activated by IGF-1 via phosphorylation of Akt/PKB. However, metastatic melanoma cell lines possess constitutively phosphorylated Erk1 and Erk2. These cells cannot be further stimulated to growth by IGF-1, suggesting that activation of Akt/PKB has no influence on the cell growth per se. Treatment of melanoma cells with IGF-1, which activates phosphorylation of Akt/PKB, has no significant influence in the phosphorylation status of Erk1 and -2 (Fig. 5B)
, suggesting no direct influence of Akt/PKB on Erk1 and -2. Whereas MAP kinase modulates genes that may be involved in protein synthesis, proliferation and extracellular matrix remodeling, Akt/PKB activates genes that regulate survival and apoptosis in tumor cells. Whether these pathways activate synergistically the key proteins to impart proliferative advantage warrants further study. ß-Catenin in melanoma cells can also be activated when cells bind through the N-cadherin adhesion molecule, which is found on all melanoma cells, and N-cadherin on melanoma cells allows them to establish gap junctions with fibroblasts for even more intimate cell-to-cell cross-talk (48)
. The functional consequences of gap junctions between melanoma cells and fibroblasts are not clear, but transport of small molecules appears to be bidirectional. Broader genomic and proteomic screening studies in the future should help to elucidate the spectrum of pathways that are activated by the most critical growth factors and cytokines in this tumor system.
|
FOOTNOTES |
|---|
1 This work was supported by Grants CA-25874, CA-47159, CA-76674, and CA-10815 from the National Institutes of Health (to M. H.). 
2 To whom requests for reprints should be addressed, at The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104. Phone: (215) 898-3950; Fax: (215) 898-0980; E-mail: herlynm{at}wistar.upenn.edu
3 The abbreviations used are: RGP, radial growth phase; VGP, vertical growth phase; IGF, insulin-like growth factor; MAP, mitogen-activated protein; PDGF, platelet-derived growth factor; PVDF, polyvinylidene difluoride; Ad, adenovirus; pfu, plaque-forming unit; bFGF, basic fibroblast growth factor.
Received 3/ 6/01. Accepted 7/26/01.
|
REFERENCES |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Vß3 integrin inhibits insulin-like growth factor I signaling in vascular smooth muscle cells. Proc. Natl. Acad. Sci. U S A, 95: 11217-11222, 1998.This article has been cited by other articles:
|
|
 |
|
  A. Boyer, M. Paquet, M.-N. Lague, L. Hermo, and D. Boerboom Dysregulation of WNT/CTNNB1 and PI3K/AKT signaling in testicular stromal cells causes granulosa cell tumor of the testis Carcinogenesis, May 1, 2009; 30(5): 869 - 878. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M.-N. Lague, M. Paquet, H.-Y. Fan, M. J. Kaartinen, S. Chu, S. P. Jamin, R. R. Behringer, P. J. Fuller, A. Mitchell, M. Dore, et al. Synergistic effects of Pten loss and WNT/CTNNB1 signaling pathway activation in ovarian granulosa cell tumor development and progression Carcinogenesis, November 1, 2008; 29(11): 2062 - 2072. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. S. Bhandarkar, J. Bromberg, C. Carrillo, P. Selvakumar, R. K. Sharma, B. N. Perry, B. Govindarajan, L. Fried, A. Sohn, K. Reddy, et al. Tris (Dibenzylideneacetone) Dipalladium, a N-Myristoyltransferase-1 Inhibitor, Is Effective against Melanoma Growth In vitro and In vivo Clin. Cancer Res., September 15, 2008; 14(18): 5743 - 5748. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Sekulic, P. Haluska Jr, A. J. Miller, J. G. De Lamo, S. Ejadi, J. S. Pulido, D. R. Salomao, E. C. Thorland, R. G. Vile, D. L. Swanson, et al. Malignant Melanoma in the 21st Century: The Emerging Molecular Landscape Mayo Clin. Proc., July 1, 2008; 83(7): 825 - 846. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Yi, J. Sun, G. E. Lim, I. G. Fantus, P. L. Brubaker, and T. Jin Cross Talk between the Insulin and Wnt Signaling Pathways: Evidence from Intestinal Endocrine L Cells Endocrinology, May 1, 2008; 149(5): 2341 - 2351. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 U. Apte, G. Zeng, M. D. Thompson, P. Muller, A. Micsenyi, B. Cieply, K. H. Kaestner, and S. P. S. Monga beta-Catenin is critical for early postnatal liver growth Am J Physiol Gastrointest Liver Physiol, June 1, 2007; 292(6): G1578 - G1585. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Fagiani, G. Giardina, L. Luzi, M. Cesaroni, M. Quarto, M. Capra, G. Germano, M. Bono, M. Capillo, P. Pelicci, et al. RaLP, a New Member of the Src Homology and Collagen Family, Regulates Cell Migration and Tumor Growth of Metastatic Melanomas Cancer Res., April 1, 2007; 67(7): 3064 - 3073. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. A. Samani, S. Yakar, D. LeRoith, and P. Brodt The Role of the IGF System in Cancer Growth and Metastasis: Overview and Recent Insights Endocr. Rev., February 1, 2007; 28(1): 20 - 47. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. K. Dearth, X. Cui, H.-J. Kim, I. Kuiatse, N. A. Lawrence, X. Zhang, J. Divisova, O. L. Britton, S. Mohsin, D. C. Allred, et al. Mammary Tumorigenesis and Metastasis Caused by Overexpression of Insulin Receptor Substrate 1 (IRS-1) or IRS-2 Mol. Cell. Biol., December 15, 2006; 26(24): 9302 - 9314. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Mirmohammadsadegh, A. Marini, S. Nambiar, M. Hassan, A. Tannapfel, T. Ruzicka, and U. R. Hengge Epigenetic Silencing of the PTEN Gene in Melanoma. Cancer Res., July 1, 2006; 66(13): 6546 - 6552. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Chen, A. Wu, H. Sun, R. Drakas, C. Garofalo, S. Cascio, E. Surmacz, and R. Baserga Functional Significance of Type 1 Insulin-like Growth Factor-mediated Nuclear Translocation of the Insulin Receptor Substrate-1 and {beta}-Catenin J. Biol. Chem., August 19, 2005; 280(33): 29912 - 29920. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. C. Mak, H. L. Kenerson, L. D. Aicher, E. A. Barnes, and R. S. Yeung Aberrant {beta}-Catenin Signaling in Tuberous Sclerosis Am. J. Pathol., July 1, 2005; 167(1): 107 - 116. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. H. Soltani, R. Pichardo, Z. Song, N. Sangha, F. Camacho, K. Satyamoorthy, O. P. Sangueza, and V. Setaluri Microtubule-Associated Protein 2, a Marker of Neuronal Differentiation, Induces Mitotic Defects, Inhibits Growth of Melanoma Cells, and Predicts Metastatic Potential of Cutaneous Melanoma Am. J. Pathol., June 1, 2005; 166(6): 1841 - 1850. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Sinha, Z. Wang, K. L. Ruchalski, J. S. Levine, S. Krishnan, W. Lieberthal, J. H. Schwartz, and S. C. Borkan Lithium activates the Wnt and phosphatidylinositol 3-kinase Akt signaling pathways to promote cell survival in the absence of soluble survival factors Am J Physiol Renal Physiol, April 1, 2005; 288(4): F703 - F713. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Hazarika, M. F. McCarty, V. G. Prieto, S. George, D. Babu, D. Koul, M. Bar-Eli, and M. Duvic Up-regulation of Flotillin-2 Is Associated with Melanoma Progression and Modulates Expression of the Thrombin Receptor Protease Activated Receptor 1 Cancer Res., October 15, 2004; 64(20): 7361 - 7369. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Yang, H. C. Dan, M. Sun, Q. Liu, X.-m. Sun, R. I. Feldman, A. D. Hamilton, M. Polokoff, S. V. Nicosia, M. Herlyn, et al. Akt/Protein Kinase B Signaling Inhibitor-2, a Selective Small Molecule Inhibitor of Akt Signaling with Antitumor Activity in Cancer Cells Overexpressing Akt Cancer Res., July 1, 2004; 64(13): 4394 - 4399. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Perlis and M. Herlyn Recent Advances in Melanoma Biology Oncologist, April 1, 2004; 9(2): 182 - 187. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. A. Morrison, A. J. Klingelhutz, and N. Raab-Traub Epstein-Barr Virus Latent Membrane Protein 2A Activates {beta}-Catenin Signaling in Epithelial Cells J. Virol., November 15, 2003; 77(22): 12276 - 12284. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Wu, K. Cui, K. Miyoshi, L. Hennighausen, J. E. Green, J. Setser, D. LeRoith, and S. Yakar Reduced Circulating Insulin-like Growth Factor I Levels Delay the Onset of Chemically and Genetically Induced Mammary Tumors Cancer Res., August 1, 2003; 63(15): 4384 - 4388. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Wang, V. L. DeGroff, and S. K. Clinton Tomato and Soy Polyphenols Reduce Insulin-Like Growth Factor-I-Stimulated Rat Prostate Cancer Cell Proliferation and Apoptotic Resistance In Vitro via Inhibition of Intracellular Signaling Pathways Involving Tyrosine Kinase J. Nutr., July 1, 2003; 133(7): 2367 - 2376. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Satyamoorthy, G. Li, M. R. Gerrero, M. S. Brose, P. Volpe, B. L. Weber, P. van Belle, D. E. Elder, and M. Herlyn Constitutive Mitogen-activated Protein Kinase Activation in Melanoma Is Mediated by Both BRAF Mutations and Autocrine Growth Factor Stimulation Cancer Res., February 15, 2003; 63(4): 756 - 759. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Herlyn, M. Padarathsingh, L. Chin, M. Hendrix, D. Becker, M. Nelson, Y. DeClerck, J. McCarthy, and S. Mohla New Approaches to the Biology of Melanoma: A Workshop of the National Institutes of Health Pathology B Study Section Am. J. Pathol., November 1, 2002; 161(5): 1949 - 1957. [Full Text] [PDF]
|
|
|
|
 |
|
 K. Satyamoorthy, G. Li, B. Vaidya, J. Kalabis, and M. Herlyn Insulin-like Growth Factor-I-induced Migration of Melanoma Cells Is Mediated by Interleukin-8 Induction Cell Growth Differ., February 1, 2002; 13(2): 87 - 93. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |
