Role of epidermal growth factor receptor signaling in RAS-driven melanoma

Melanoma: A Historical Walk-through from Palliative Treatment to Modern-day Practice

"Melanoma is one of the most common types of malignancy in the world, and one known to carry a very poor prognosis until recent years. This review aims to outline the events in the history of the disease and the impact made by the discoveries along the way, as well as the modern-day consensus by referencing the updated literature regarding the present approach and future directions. In the last two decades, several studies and research have brought significant improvement in the diagnosis and clinical management of melanomas. The development of sentinel lymph node biopsy has brought major changes to the surgical approach to the disease, and modern therapies based on recently developed knowledge changed the death sentence this diagnosis once meant to a manageable condition despite its aggressiveness, keeping in mind that early diagnosis and safe margin excision remain the best and most optimistic course of treatment. "

Current understanding of epigenetics role in melanoma treatment and resistance

Melanoma is the most aggressive form of skin cancer resulting from genetic mutations in melanocytes. Several factors have been considered to be involved in melanoma progression, including genetic alteration, processes of damaged DNA repair, and changes in mechanisms of cell growth and proliferation. Epigenetics is the other factor with a crucial role in melanoma development. Epigenetic changes have become novel targets for treating patients suffering from melanoma. These changes can alter the expression of microRNAs and their interaction with target genes, which involves cell growth, differentiation, or even death. Given these circumstances, we conducted the present review to discuss the melanoma risk factors and represent the current knowledge about the factors related to its etiopathogenesis. Moreover, various epigenetic pathways, which are involved in melanoma progression, treatment, and chemo-resistance, as well as employed epigenetic factors as a solution to the problems, will be discussed in detail.

Control of cell signaling by Arf GTPases and their regulators: Focus on links to cancer and other GTPase families

The ADP-ribosylation factors (Arfs) comprise a family of regulatory GTP binding proteins. The Arfs regulate membrane trafficking and cytoskeleton remodeling, processes critical for eukaryotes and which have been the focus of most studies on Arfs. A more limited literature describes a role in signaling and in integrating several signaling pathways to bring about specific cell behaviors. Here, we will highlight work describing function of Arf1, Arf6 and several effectors and regulators of Arfs in signaling.

EGFR Pathway-Based Gene Signatures of Druggable Gene Mutations in Melanoma, Breast, Lung, and Thyroid Cancers

EGFR, BRAF, PIK3CA, and KRAS genes play major roles in EGFR pathway, and accommodate activating mutations that predict response to many targeted therapeutics. However, connections between these mutations and EGFR pathway expression patterns remain unexplored. Here, we investigated transcriptomic associations with these activating mutations in three ways. First, we compared expressions of these genes in the mutant and wild type tumors, respectively, using RNA sequencing profiles from The Cancer Genome Atlas project database (n = 3660). Second, mutations were associated with the activation level of EGFR pathway. Third, they were associated with the gene signatures of differentially expressed genes from these pathways between the mutant and wild type tumors. We found that the upregulated EGFR pathway was linked with mutations in the BRAF (thyroid cancer, melanoma) and PIK3CA (breast cancer) genes. Gene signatures were associated with BRAF (thyroid cancer, melanoma), EGFR (squamous cell lung cancer), KRAS (colorectal cancer), and PIK3CA (breast cancer) mutations. However, only for the BRAF gene signature in the thyroid cancer we observed strong biomarker diagnostic capacity with AUC > 0.7 (0.809). Next, we validated this signature on the independent literature-based dataset (n = 127, fresh-frozen tissue samples, AUC 0.912), and on the experimental dataset (n = 42, formalin fixed, paraffin embedded tissue samples, AUC 0.822). Our results suggest that the RNA sequencing profiles can be used for robust identification of the replacement of Valine at position 600 with Glutamic acid in the BRAF gene in the papillary subtype of thyroid cancer, and evidence that the specific gene expression levels could provide information about the driver carcinogenic mutations.

EGFRAP encodes a new negative regulator of the EGFR acting in both normal and oncogenic EGFR/Ras-driven tissue morphogenesis

Activation of Ras signaling occurs in ~30% of human cancers. However, activated Ras alone is insufficient to produce malignancy. Thus, it is imperative to identify those genes cooperating with activated Ras in driving tumoral growth. In this work, we have identified a novel EGFR inhibitor, which we have named EGFRAP, for EGFR adaptor protein. Elimination of EGFRAP potentiates activated Ras-induced overgrowth in the Drosophila wing imaginal disc. We show that EGFRAP interacts physically with the phosphorylated form of EGFR via its SH2 domain. EGFRAP is expressed at high levels in regions of maximal EGFR/Ras pathway activity, such as at the presumptive wing margin. In addition, EGFRAP expression is up-regulated in conditions of oncogenic EGFR/Ras activation. Normal and oncogenic EGFR/Ras-mediated upregulation of EGRAP levels depend on the Notch pathway. We also find that elimination of EGFRAP does not affect overall organogenesis or viability. However, simultaneous downregulation of EGFRAP and its ortholog PVRAP results in defects associated with increased EGFR function. Based on these results, we propose that EGFRAP is a new negative regulator of the EGFR/Ras pathway, which, while being required redundantly for normal morphogenesis, behaves as an important modulator of EGFR/Ras-driven tissue hyperplasia. We suggest that the ability of EGFRAP to functionally inhibit the EGFR pathway in oncogenic cells results from the activation of a feedback loop leading to increase EGFRAP expression. This could act as a surveillance mechanism to prevent excessive EGFR activity and uncontrolled cell growth.

Activation of Ras signalling occurs in ~30% of human cancers. However, activated Ras alone is insufficient to produce malignancy. Thus, the discovery of genes cooperating with Ras in cancer is imperative to understand tumoral growth driven by Ras activating mutations. A key output of over-activated EGFR/Ras signalling is the induction of a complex and dynamic set of transcriptional networks leading to changes in gene expression. As a result of these changes, the normal function of some genes can become adjusted in a tumorigenic context. In this work, using the Drosophila wing imaginal disc as model system, we have identified a new EGFR inhibitor, EGFRAP, which function is redundant for proper morphogenesis, yet becomes an important limiter of the overgrowth driven by oncogenic EGFR/Ras activity. We show that the specificity of EGFRAP in cells with high levels of EGFR activity arises from activation of a negative feedback loop resulting in increased EGFRAP levels. This could act to prevent excessive EGFR activity and uncontrolled cell growth. We believe the identification of other factors behaving like EGFRAP, will help in our fight against cancer, as it might lead to the identification of new therapeutic drugs affecting cancer but not normal cells, a top priority in cancer research.

Aloysia Citrodora Essential Oil Inhibits Melanoma Cell Growth and Migration by Targeting HB-EGF-EGFR Signaling

Patients diagnosed with melanoma have a poor prognosis due to regional invasion and metastases. The receptor tyrosine kinase epidermal growth factor receptor (EGFR) is found in a subtype of melanoma with a poor prognosis and contributes to drug resistance. Aloysia citrodora essential oil (ALOC-EO) possesses an antitumor effect. Understanding signaling pathways that contribute to the antitumor of ALOC-EO is important to identify novel tumor types that can be targeted by ALOC-EO. Here, we investigated the effects of ALOC-EO on melanoma growth and tumor cell migration. ALOC-EO blocked melanoma growth in vitro and impaired primary tumor cell growth in vivo. Mechanistically, ALOC-EO blocked heparin-binding-epidermal growth factor (HB-EGF)-induced EGFR signaling and suppressed ERK1/2 phosphorylation. Myelosuppressive drugs upregulated HB-EGF and EGFR expression in melanoma cells. Cotreatment of myelosuppressive drugs with ALOC-EO improved the antitumor activity and inhibited the expression of matrix metalloproteinase-7 and -9 and a disintegrin and metalloproteinase domain-containing protein9. In summary, our study demonstrates that ALOC-EO blocks EGFR and ERK1/2 signaling, with preclinical efficacy as a monotherapy or in combination with myelosuppressive drugs in melanoma.

WIPI1 promotes fission of endosomal transport carriers and formation of autophagosomes through distinct mechanisms

Autophagosome formation requires PROPPIN/WIPI proteins and monophosphorylated phosphoinositides, such as phosphatidylinositol-3-phosphate (PtdIns3P) or PtdIns5P. This process occurs in association with mammalian endosomes, where the PROPPIN WIPI1 has additional, undefined roles in vesicular traffic. To explore whether these functions are interconnected, we dissected routes and subreactions of endosomal trafficking requiring WIPI1. WIPI1 specifically acts in the formation and fission of tubulo-vesicular endosomal transport carriers. This activity supports the PtdIns(3,5)P₂-dependent transport of endosomal cargo toward the plasma membrane, Golgi, and lysosomes, suggesting a general role of WIPI1 in endosomal protein exit. Three features differentiate the endosomal and macroautophagic/autophagic activities of WIPI1: phosphoinositide binding site II, the requirement for PtdIns(3,5)P₂, and bilayer deformation through a conserved amphipathic α-helix. Their inactivation preserves autophagy but leads to a strong enlargement of endosomes, which accumulate micrometer-long endosomal membrane tubules carrying cargo proteins. WIPI1 thus supports autophagy and protein exit from endosomes by different modes of action. We propose that the type of phosphoinositides occupying its two lipid binding sites, the most unusual feature of PROPPIN/WIPI family proteins, switches between these effector functions.

Abbreviations: EGF: epidermal growth factorEGFR: epidermal growth factor receptorKD: knockdownKO: knockoutPtdIns3P: phosphatidylinositol-3-phosphatePtdIns5P: phosphatidylinositol-5-phosphatePtdIns(3,5)P₂: phosphatidylinositol-3,5-bisphosphateTF: transferrinTFRC: transferrin receptorWT: wildtype

Effects of somatic alterations at pathway level are more mechanism-explanatory and clinically applicable to quantity of liver metastases of colorectal cancer

BACKGROUND

The quantity of metastases lesions is an important reference when it comes to making a more informed treatment decision for patients with colorectal cancer liver metastases. However, the molecular alterations in patients with different numbers of lesions have not been systematically studied.

METHODS

We investigated somatic alterations and microsatellite instability (MSI) of liver metastases from patients with single, multiple or diffuse metastasis lesions. A new algorithm "Pathway Damage Score" was developed to comprehensively assess the functional impact of somatic alterations at the pathway level. Pathogenic pathways of different metastasis were identified and their prognosis effects were evaluated. Furthermore, the subnetworks and affected phenotypes of the altered genes in each pathogenic pathway were analyzed.

RESULTS

Somatic alterations and altered genes occurred sporadically as well as in MSI state in different metastasis types, although MSS patients had more metastatic lesions than that of the MSI patients. Every metastasis group has their own pathogenic pathways and damaged "Cargo recognition for clathrin-mediated endocytosis" is significantly associated with poor prognosis (P < 0.001). Further pathway subnetwork analysis showed that except conventional drivers, other genes could also contribute to metastasis formation.

CONCLUSIONS

Progression of liver metastasis could be driven by the coefficient of all altered genes belonging to the pathways. Thus, compared to somatic alterations and genes, pathway level analysis is more reasonable for functional interpretations of molecular alterations in clinical samples.

A high-performance liquid chromatography-tandem mass spectrometry method for the determination of lifrafenib, a novel RAF kinase and EGFR inhibitor, in human plasma and urine and its application in clinical pharmacokinetic study

Lifirafenib (BGB-283), a dual inhibitor trageting BRAF kinase and EGFR, showed favorable efficacy and safety in treating patients with different cancer types harboring mutations in BRAF, KRAS and NRAS. In order to support the clinical pharmacokinetic study, a sensitive high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated to quantify lifirafenib concentration in human plasma and urine. Plasma samples were purified using protein precipitation. Urine samples were pre-treated by adding tween 80 with the purpose of preventing non-specific adsorption, then extracted by centrifugation. Chromatographic separation was achieved on Phenomenex Luna C₁₈ column with a gradient elution. The mass detection was performed using electrospray ionization (ESI) source under multiple reaction monitoring (MRM) in positive ionization mode. The method was fully validated, and the result of inter-assay and intra-assay precisions were less than 15% and the accuracy within the scope of ±15%. The linear range for plasma and urine covered from 10 to 10,000 ng/mL and 1 to 200 ng/mL, respectively, with correlation coefficients of 0.99. The validation for matrix effect, recovery, stability and carryover were met the acceptance criteria. The method showed robust and sensitive, it successfully fulfilled the requirement of clinical pharmacokinetic study of lifirafenib in Chinese patients with locally advanced or metastatic solid tumors.

Reversal of Resistance in Targeted Therapy of Metastatic Melanoma: Lessons Learned from Vemurafenib (BRAFV600E-Specific Inhibitor)

Malignant melanoma is the most aggressive form of skin cancer and has a very low survival rate. Over 50% of melanomas harbor various BRAF mutations with the most common being the V600E. BRAF^V600E mutation that causes constitutive activation of the MAPK pathway leading to drug-, immune-resistance, apoptosis evasion, proliferation, survival, and metastasis of melanomas. The ATP competitive BRAF^V600E selective inhibitor, vemurafenib, has shown dramatic success in clinical trials; promoting tumor regression and an increase in overall survival of patients with metastatic melanoma. Regrettably, vemurafenib-resistance develops over an average of six months, which renders melanomas resistant to other therapeutic strategies. Elucidation of the underlying mechanism(s) of acquisition of vemurafenib-resistance and design of novel approaches to override resistance is the subject of intense clinical and basic research. In this review, we summarize recent developments in therapeutic approaches and clinical investigations on melanomas with BRAF^V600E mutation to establish a new platform for the treatment of melanoma.

EGFR/ARF6 regulation of Hh signalling stimulates oncogenic Ras tumour overgrowth

Multiple signalling events interact in cancer cells. Oncogenic Ras cooperates with Egfr, which cannot be explained by the canonical signalling paradigm. In turn, Egfr cooperates with Hedgehog signalling. How oncogenic Ras elicits and integrates Egfr and Hedgehog signals to drive overgrowth remains unclear. Using a Drosophila tumour model, we show that Egfr cooperates with oncogenic Ras via Arf6, which functions as a novel regulator of Hh signalling. Oncogenic Ras induces the expression of Egfr ligands. Egfr then signals through Arf6, which regulates Hh transport to promote Hh signalling. Blocking any step of this signalling cascade inhibits Hh signalling and correspondingly suppresses the growth of both, fly and human cancer cells harbouring oncogenic Ras mutations. These findings highlight a non-canonical Egfr signalling mechanism, centered on Arf6 as a novel regulator of Hh signalling. This explains both, the puzzling requirement of Egfr in oncogenic Ras-mediated overgrowth and the cooperation between Egfr and Hedgehog.

EGFR signalling is required for oncogenic Ras driven tumorigenesis. In this study, using a Drosophila tumour model the authors demonstrate that depletion of Arf6, a Ras-related GTP-binding protein activated by EGFR, supresses oncogenic Ras driven overgrowth via modulation of Hedgehog signalling.

Tumor-promoting effects of cannabinoid receptor type 1 in human melanoma cells

The role of endocannabinoid system in melanoma development and progression is actually not fully understood. This study was aimed at clarifying whether cannabinoid-type 1 (CB1) receptor may function as tumor-promoting or -suppressing signal in human cutaneous melanoma. CB1 receptor expression was measured in human melanoma cell lines by real-time PCR. A genetic deletion of CB1 receptors in selected melanoma cells was carried out by using three different short hairpin RNAs (shRNAs). Performance of target gene silencing was verified by real-time PCR and Western blot. The effects of CB1 receptor silencing on cell growth, clonogenicity, migration capability, cell cycle progression, and activation of mitogenic signals was tested. Lentiviral shRNAs vectors targeting different regions of the human CB1 gene led to a significant reduction in CB1 receptor mRNA and a near complete loss of CB1 receptor protein, compared to control vector (LV-c). The number of viable cells, the colony-forming ability and cell migration were significantly reduced in cells transduced with CB1 lentiviral shRNAs compared to LV-c. Cell cycle analyses showed arrest at G1/S phase. p-Akt and p-ERK expression were decreased in transduced versus control cells. Findings of this study suggest that CB1 receptor might function as tumor-promoting signal in human cutaneous melanoma.

Genetic Testing in the Multidisciplinary Management of Melanoma

Melanoma is increasing in incidence and represents an aggressive type of cancer. Efforts have focused on identifying genetic factors in melanoma carcinogenesis to guide prevention, screening, early detection, and targeted therapy. This article reviews the hereditary risk factors associated with melanoma and the known molecular pathways and genetic mutations associated with this disease. This article also explores the controversies associated with genetic testing and the latest advances in identifying genetic targets in melanoma, which offer promise for future application in the multidisciplinary management of melanoma.

The melanoma revolution: from UV carcinogenesis to a new era in therapeutics

Melanoma, the deadliest form of skin cancer, is an aggressive disease that is rising in incidence. Although melanoma is a historically treatment-resistant malignancy, in recent years unprecedented breakthroughs in targeted therapies and immunotherapies have revolutionized the standard of care for patients with advanced disease. Here, we provide an overview of recent developments in our understanding of melanoma risk factors, genomics, and molecular pathogenesis and how these insights have driven advances in melanoma treatment. In addition, we review benefits and limitations of current therapies and look ahead to continued progress in melanoma prevention and therapy. Remarkable achievements in the field have already produced a paradigm shift in melanoma treatment: Metastatic melanoma, once considered incurable, can now be treated with potentially curative rather than palliative intent.

Cooperative interactions of PTEN deficiency and RAS activation in melanoma metastasis

Melanoma displays frequent activation of RAS/RAF/MAPK and PI3K/AKT signaling pathways as well as inactivation of CDKN2A (INK4a/ARF) and PTEN tumor suppressors via genetic and epigenetic alterations. Pathogenetic roles of these melanoma-prone mutations and their genetic interactions have been established in genetically engineered mouse models. Here, we catalog frequent genetic alterations observed in human melanomas and describe mouse models of melanoma initiation and progression, including our recent study that investigated the genetic interactions of RAS activation and PTEN loss in a CDKN2A (INK4a/ARF) null melanoma prone genetic background. We showed that loss of PTEN cooperates with HRAS activation, leading to increased development of melanoma and emergence of metastasis. Moreover, we observed that RNA i-mediated PTEN inactivation in RAS-driven melanomas enhanced migration and invasion with concomitant downregulation of E-cadherin, the major regulator of epithelial and mesenchymal transition, and enhanced AKT2 phosphorylation, which has been previously linked to invasion and metastasis of several cancer types, including breast and ovary. These data show that activated RAS cooperates with PTEN loss in melanoma genesis and progression.

Hybrid molecule from Farnesylthiosalicylic acid-diamine and phenylpropenoic acid as Ras-related signaling inhibitor with potent antitumor activities

Novel series of Farnesylthiosalicylic acid-diamine/phenylpropenoic acid hybrids were designed and synthesized. Their in vitro growth inhibitory assays showed that most compounds displayed strong antiproliferation activity against seven cancer cells. Especially, the new hybrid 12 f, by the conjugation of 10a with ferulic acid, could selectively suppress the proliferation of tumor cells and display significantly lower toxicities to normal cells than its intermediate 10a. Furthermore, 12 f dose-dependently induced SMMC-7721 cell apoptosis. Additionally, our observations demonstrated that 12 f inhibited both Ras-related signaling and phosphorylated NF-κB synergistically, which may be advantageous to the strong antitumor activities of 12 f. Our findings suggest that these novel hybrids may hold a great promise as therapeutic agents for the intervention of human cancers.

Induction of pancreatic cancer cell migration by an autocrine epidermal growth factor receptor activation

Pancreatic cancer is characterized by aggressive local invasion and early metastasis formation. Active migration of the pancreatic cancer cells is essential for these processes. We have shown previously that the pancreatic cancer cells lines CFPAC1 and IMIM-PC2 show high migratory activity, and we have investigated herein the reason for this observation. Cell migration was assessed using a three-dimensional, collagen-based assay and computer-assisted cell tracking. The expression of receptor tyrosine kinases was determined by flow-cytometry and cytokine release was measured by an enzyme-linked immunoassay. Receptor function was blocked by antibodies or pharmacological enzyme inhibitors. Both cells lines express the epidermal growth factor receptor (EGFR) as well as its family-member ErbB2 and the platelet-derived growth factor receptor (PDGFR)α, whereas only weak expression was detected for ErbB3 and no expression of PDGFRβ. Pharmacological inhibition of the EGFR or ErbB2 significantly reduced the migratory activity in both cell lines, as did an anti-EGFR antibody. Interestingly, combination of the latter with an anti-PDGFR antibody led to an even more pronounced reduction. Both cell lines release detectable amounts of EGF. Thus, the high migratory activity of the investigated pancreatic cancer cell lines is due to autocrine EGFR activation and possibly of other receptor tyrosine kinases.

Aberrant apoptotic machinery confers melanoma dual resistance to BRAF(V600E) inhibitor and immune effector cells: immunosensitization by a histone deacetylase inhibitor

BRAF(V600E)-inhibitors (BRAFi; e.g., vemurafenib) and modern immune-based therapies such as PD-1/PD-L1 and CTLA-4 checkpoints blockade and adoptive cell transfer (ACT) have significantly improved the care of melanoma patients. Having these two effective (BRAFi and immunotherapy) therapies raises the question whether there is a rational biological basis for using them in combination. We developed an in vitro model to determine whether tumor resistance mechanisms to a small molecule inhibitor of a driver oncogene, and to cytotoxic T lymphocyte (CTL)- and natural killer (NK) cell-delivered apoptotic death signals were exclusive or intersecting. We generated melanoma sublines resistant to BRAFi vemurafenib and to CTL recognizing the MART-1 melanoma antigen. Vemurafenib-resistant (VemR) sublines were cross-resistant to MART CTL and NK cells indicating that a common apoptotic pathway governing tumor response to both modalities was disrupted. Pretreatment of VemR melanomas with a histone deacetylase inhibitor (HDACi) restored sensitivity to MART CTL and NK apoptosis by skewing the apoptotic gene programs towards a proapoptotic phenotype. Our in vitro findings suggest that during the course of acquisition of BRAFi resistance, melanomas develop cross-resistance to CTL- and NK-killing. Further, aberrant apoptotic pathways, amenable by an FDA-approved chromatin remodeling drug, regulate tumor resistance mechanisms to immune effector cells. These results may provide rational molecular basis for further investigations to combine these therapies clinically.

Genetics and genomics of melanoma

The rapidly increasing incidence of melanoma, coupled with its highly aggressive metastatic nature, is of urgent concern. In order to design rational therapies, it is of critical importance to identify the genetic determinants that drive melanoma formation and progression. To date, signaling cascades emanating from the EGF receptor, c-MET and other receptors are known to be altered in melanoma. Important mutations in signaling molecules, such as BRAF and N-RAS, have been identified. In this review, some of the major genetic alterations and signaling pathways involved in melanoma will be discussed. Given the great deal of genetic heterogeneity observed in melanoma, it is likely that many more genetic determinants exist. Through the use of powerful genomic technologies, it is now possible to identify these additional genetic alterations in melanoma. A critical step in this analysis will be culling bystanders from functionally important drivers, as this will highlight genetic elements that will be promising therapeutic targets. Such technologies and the important points to consider in understanding the genetics of melanoma will be reviewed.

The matrikine tenascin-C protects multipotential stromal cells/mesenchymal stem cells from death cytokines such as FasL

Multipotential stromal cells/mesenchymal stem cells (MSCs) are attractive candidates for regenerative therapy due to the ability of these cells to differentiate and positively influence neighboring cells. However, on implantation for wound reconstruction, these cells are lost as they are challenged by nonspecific inflammation signals generated in the wound environment and in response to any implanted foreign body. We have previously shown that sustained and surface-restricted epidermal growth factor receptor (EGFR) signaling by a tethered form of its prototypal ligand EGF enhances survival of MSC in the presence of death cytokines such as FasL, serum deprivation, and low oxygen in vitro. This was proposed to be due to the plasma membrane restriction of EGFR signaling. Interestingly, during wound repair, an extracellular matrix (ECM) component Tenascin-C (TNC) containing EGF-like repeats (EGFL) and fibronectin-like repeats (FNL) is upregulated. A few of the 14 EGFL on each of the 6 arms, especially the 14th, bind as low-affinity/high-avidity ligands to EGFR causing sustained surface-restricted EGFR signaling. We queried whether signaling by this physiologically relevant EGFR matrikine also protects MSCs from FasL-induced death. MSCs grown on TNC and Collagen I (as TNC by itself is antiadhesive) displayed a survival advantage in the presence of FasL. TNC neither sequestered nor neutralized FasL; rather, the effects of survival were via cell signaling. This survival was dependent on TNC activating EGFR and downstream pathways of Erk and Akt through EGFL; to a much lesser extent, the FNL of TNC also contributed to survival. Taken together, these results suggest that providing MSCs with a nonimmunogenic naturally occurring ECM moiety such as TNC enhances their survival in the presence of death factors, and this advantage occurs via signaling through EGFR primarily and integrins only to a minor extent. This matrix component is proposed to supplement MSC delivery on the scaffolds to provide a survival advantage against death upon in vivo implantation.

An ERBB3/ERBB2 oncogenic unit plays a key role in NRG1 signaling and melanoma cell growth and survival

We recently identified neuregulin-1 (NRG1) as a novel target of Notch1 required in Notch-dependent melanoma growth. ERBB3 and ERBB4, tyrosine kinase receptors specifically activated by NRG1, have been shown to be either elevated in melanoma cell lines and tumors or to be mutated in 20% of melanomas, respectively. While these data support key roles of NRG1 and its receptors in the pathogenesis of melanoma, whether ERBB3 and ERBB4 display redundant or exclusive functions is not known. Here, we show that ERBB3 and ERBB4 inhibition results in distinct outcomes. ERBB3 inhibition ablates the cellular responses to NRG1, results in AKT inactivation and leads to cell growth arrest and apoptotic cell death. In contrast, ERBB4 knockdown mildly affects cell growth, has no effects on cell survival and, importantly, does not alter the responses to NRG1. Finally, we identified ERBB2 as a key coreceptor in NRG1-dependent ERBB3 signaling. ERBB2 forms a complex with ERBB3, and its inhibition recapitulates the phenotypes observed upon ERBB3 ablation. We propose that an NRG1-ERBB3-ERBB2 signaling unit operates in melanoma cells where it promotes growth and survival.

Drug targets and predictive biomarkers in the management of metastatic melanoma

Melanoma is the leading cause of fatal skin cancer, and in the past few decades, there has been an increase in the incidence of and mortality from metastatic melanoma. Until recently, the therapeutic options for treatment of metastatic melanoma were limited. The approval of ipilimumab (an anti-CTLA-4 antibody) and vemurafenib (mutant B-RAF^V600E kinase inhibitor) by the Federal Drug Administration has led to a new era in melanoma treatment, and additional promising drugs and drug combinations are currently being investigated. As the choices of treatment for melanoma have expanded, the need to identify predictive biomarkers to tailor treatment strategies to individual tumor or immune system characteristics has become necessary. Such strategies have the potential of maximizing antitumor effect while minimizing toxicity and improving clinical benefit. In this article, we review the currently approved targeted therapies in melanoma and discuss the future of personalized therapy for this disease.

EGF receptor is required for KRAS-induced pancreatic tumorigenesis

Initiation of pancreatic ductal adenocarcinoma (PDA) is definitively linked to activating mutations in the KRAS oncogene. However, PDA mouse models show that mutant Kras expression early in development gives rise to a normal pancreas, with tumors forming only after a long latency or pancreatitis induction. Here, we show that oncogenic KRAS upregulates endogenous EGFR expression and activation, the latter being dependent on the EGFR ligand sheddase, ADAM17. Genetic ablation or pharmacological inhibition of EGFR or ADAM17 effectively eliminates KRAS-driven tumorigenesis in vivo. Without EGFR activity, active RAS levels are not sufficient to induce robust MEK/ERK activity, a requirement for epithelial transformation.

MAP kinase signaling and inhibition in melanoma

The mitogen-activated protein kinase (MAPK) pathway is critical to oncogenic signaling in the majority of patients with malignant melanoma. Driver mutations in both NRAS and BRAF have important implications for prognosis and treatment. The development of inhibitors to mediators of the MAPK pathway, including those to CRAF, BRAF, and MEK, has led to major advances in the treatment of patients with melanoma. In particular, the selective BRAF inhibitor vemurafenib has been shown to improve overall survival in patients with tumors harboring BRAF mutations. However, the duration of benefit is limited in many patients and highlights the need for understanding the limitations of therapy in order to devise more effective strategies. MEK inhibitors have proven to particularly active in BRAF mutant melanomas also. Emerging knowledge about mechanisms of resistance as well as a more complete understanding of the biology of MAPK pathway signaling provides insight into rational combination regimens and sequences of molecularly targeted therapies.

Hyperactivation of constitutively dimerized oncogenic EGF receptors by autocrine loops

The epidermal growth factor (EGF) receptor (EGFR) has a key role in normal embryonic development, adult tissue homeostasis and many pathological processes, in particular tumour formation. Aberrant EGFR activation occurs in many cancer types, and inhibition of this receptor is a promising anti-tumour strategy. Besides overexpression of the wild-type receptor, mutated oncogenic EGFR variants are often associated with malignant transformation. In human non-small-cell lung cancers, kinase mutants of the EGFR are rather common. Human glioblastoma often express the truncated EGFRvIII version as well as other dimerized and permanently activated mutants of the receptor, which are considered as tumour drivers. Similarly, the mutated and dimerized EGFR variant Xiphophorus melanoma receptor kinase (Xmrk) is causative for the development of malignant pigment cell tumours in medaka and Xiphophorus melanoma models. It is generally believed that oncogenic receptors that are active due to dimerizing mutations are ligand independent. Here, we show that different EGFR variants from fish and human efficiently induce autocrine loops by inducing EGFR ligands such as amphiregulin and HB-EGF. Importantly, the pre-dimerized oncogenic EGFR versions Xmrk from Xiphophorus and human EGFR(C600F), though already active in absence of ligands, respond to ligand stimulation with enhanced oncogenic signalling. In summary, our data show that autocrine or paracrine loops are still acting on pre-dimerized oncogenic EGFRs and contribute to their pro-tumorigenic signalling.

Advances in melanoma senescence and potential clinical application

Normal cells possess a limited proliferative life span, after which they enter a state of irreversible growth arrest, called replicative senescence, which acts as a potent barrier against transformation. Transformed cells have escaped the process of replicative senescence and theoretically can not re-enter senescence. However, recent observations showed that transformed cells, and particularly the melanoma cells, can still undergo oncogene or stress-induced senescence. This senescence state is accompanied by many of the markers associated with replicative senescence, such as flattened shape, increased acidic β-galactosidase activity, characteristic changes in gene expression and growth arrest. Interestingly, in some cancers, senescence induction following chemotherapy has been correlated with a favorable patient outcome. In this review, we gathered recent results describing senescence-like phenotype induction in melanoma cells and discuss why senescence may also be exploited as a therapeutic strategy in melanoma.

Personalized Medicine in Non–Small-Cell Lung Cancer: Is KRAS a Useful Marker in Selecting Patients for Epidermal Growth Factor Receptor–Targeted Therapy?

In patients with metastatic colorectal cancer, the predictive value of KRAS mutational status in the selection of patients for treatment with anti–epidermal growth factor (EGFR) monoclonal antibodies is established. In patients with non–small-cell lung cancer (NSCLC), the utility of determining KRAS mutational status to predict clinical benefit to anti-EGFR therapies remains unclear. This review will provide a brief description of Ras biology, provide an overview of aberrant Ras signaling in NSCLC, and summarize the clinical data for using KRAS mutational status as a negative predictive biomarker to anti-EGFR therapies. Retrospective investigations of KRAS mutational status as a negative predictor of clinical benefit from anti-EGFR therapies in NSCLC have been performed; however, small samples sizes as a result of low prevalence of KRAS mutations and the low rate of tumor sample collection have limited the strength of these analyses. Although an association between the presence of KRAS mutation and lack of response to EGFR tyrosine kinase inhibitors (TKIs) has been observed, it remains unclear whether there is an association between KRAS mutation and EGFR TKI progression-free and overall survival. Unlike colorectal cancer, KRAS mutations do not seem to identify patients who do not benefit from anti-EGFR monoclonal antibodies in NSCLC. The future value of testing for KRAS mutational status may be to exclude the possibility of an EGFR mutation or anaplastic lymphoma kinase translocation or to identify a molecular subset of patients with NSCLC in whom to pursue a drug development strategy that targets the KRAS pathway.

Cooperative interactions of PTEN deficiency and RAS activation in melanoma metastasis

Mitogen-activated protein kinase (MAPK) and AKT pathways are frequently co-activated in melanoma through overexpression of receptor tyrosine kinases, mutations in their signaling surrogates, such as RAS and BRAF, or loss of negative regulators such as PTEN. As RAS can be a positive upstream regulator of PI3-K, it has been proposed that the loss of PTEN and the activation of RAS are redundant events in melanoma pathogenesis. Here, in genetically engineered mouse models of cutaneous melanomas, we sought to better understand the genetic interactions between HRAS activation and PTEN inactivation in melanoma genesis and progression in vivo. We showed that HRAS activation cooperates with Pten+/- and Ink4a/Arf-/- to increase melanoma penetrance and promote metastasis. Correspondingly, gain- and loss-of-function studies established that Pten loss increases invasion and migration of melanoma cells and non-transformed melanocytes, and such biological activity correlates with a shift to phosphorylation of AKT2 isoform and E-cadherin down-regulation. Thus, Pten inactivation can drive the genesis and promote the metastatic progression of RAS activated Ink4a/Arf deficient melanomas.

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

Background

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

Results

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

Conclusions

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

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

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

Recent advances on skin-resident stem/progenitor cell functions in skin regeneration, aging and cancers and novel anti-aging and cancer therapies

Recent advances in skin-resident adult stem/progenitor cell research have revealed that these immature and regenerative cells with a high longevity provide critical functions in maintaining skin homeostasis and repair after severe injuries along the lifespan of individuals. The establishment of the functional properties of distinct adult stem/progenitor cells found in skin epidermis and hair follicles and extrinsic signals from their niches, which are deregulated during their aging and malignant transformation, has significantly improved our understanding on the etiopathogenesis of diverse human skin disorders and cancers. Particularly, enhanced ultraviolet radiation exposure, inflammation and oxidative stress and telomere attrition during chronological aging may induce severe DNA damages and genomic instability in the skin-resident stem/progenitor cells and their progenies. These molecular events may result in the alterations in key signalling components controlling their self-renewal and/or regenerative capacities as well as the activation of tumour suppressor gene products that trigger their growth arrest and senescence or apoptotic death. The progressive decline in the regenerative functions and/or number of skin-resident adult stem/progenitor cells may cause diverse skin diseases with advancing age. Moreover, the photoaging, telomerase re-activation and occurrence of different oncogenic events in skin-resident adult stem/progenitor cells may also culminate in their malignant transformation into cancer stem/progenitor cells and skin cancer initiation and progression. Therefore, the anti-inflammatory and anti-oxidant treatments and stem cell-replacement and gene therapies as well as the molecular targeting of their malignant counterpart, skin cancer-initiating cells offer great promise to treat diverse skin disorders and cancers.

Annexins--modulators of EGF receptor signalling and trafficking

At the cell surface, activation of the epidermal growth factor (EGF) receptor triggers a complex network of signalling events that regulate a variety of cellular processes. For signal termination, the activated EGF receptor is internalised and targeted to lysosomes for degradation. Microdomain localization at the plasma membrane and endocytic transport of the EGFR is important for the formation of compartment-specific signalling complexes and is regulated by scaffolding and targeting proteins. This includes Ca2+-effector proteins, such as calmodulin and annexins (Anx), in particular AnxA1, AnxA2, AnxA6 and as shown recently,AnxA8. Given that these annexins show differences in their expression patterns, subcellular localization and mode of action, they are likely to differentially contribute and cooperate in the fine-tuning of EGFR activity. In support of this hypothesis, current literature suggests these annexins to be involved in different steps that control the endocytic transport and signalling of the EGF receptor. This review summarizes how the coordinated activity of AnxA1, AnxA2, AnxA6 and AnxA8 can contribute to regulate EGF receptor localization and activity.

UV-induced EGFR signal transactivation is dependent on proligand shedding by activated metalloproteases in skin cancer cell lines

Exposure to extensive ultraviolet (UV) rays is a major cause of skin cancer, which is thought to be initiated by DNA mutations. Members of the epidermal growth factor receptor (EGFR) family are important in various pathophysiologic processes like cancer and are shown to be phosphorylated upon UV exposure. Here we show that EGFR phosphorylation by modest UV doses is dependent on metalloprotease activity and resultant epidermal growth factor (EGF) family proligand shedding. This proligand cleavage releases the mature ligand, which then binds to and activates EGFR. We show that UV induced EGFR phosphorylation in transformed cell lines of melanocyte and keratinocyte origin, which was reduced upon preincubation with a broad-spectrum metalloprotease inhibitor, BB94. UV also activated EGFR downstream signaling via Erk and Akt pathways in a BB94-sensitive manner. Furthermore, using neutralizing antibodies we found that proligand amphiregulin was required for UV-induced EGFR activation in SCC-9 cells. Using RNAi this EGFR activation was further shown to depend on the metalloproteases ADAM9 and ADAM17 in SCC-9 cells. cDNA array hybridization and RT-PCR analysis showed overexpression of a Disintegrin and a Metalloproteases (ADAMs) and EGF family proligands in melanoma cell lines. Additionally, blocking EGFR signal transactivation by BB94 led to increased apoptosis in UV-irradiated cells. EGFR signal transactivation also led to increased stability of the DNA repair protein, PARP, under UV stress. Thus, both antiapoptotic and DNA repair pathways are activated simultaneously by EGFR signal transactivation. Together, our data provide novel insights into the mechanism of UV-induced EGFR activation, suggesting broad relevance of the UV-ADAM-proligand-EGFR-Erk/Akt pathway and its significance in skin cancer.

Melanoma and the tumor microenvironment

Melanoma arises through the accrual of mutations in genes critical for proliferation and survival. Although melanoma had been traditionally conceptualized as a cell-autonomous event, increasing evidence supports the notion that these tumors are not isolated entities but rather depend, interact with, and react to the adjacent microenvironment. Melanoma is composed of not only the malignant cells but also the supporting stroma, which includes fibroblasts, endothelial cells, immune cells, soluble molecules, and the extracellular matrix (ECM). Tumor cells actively interact with the microenvironment in a bidirectional manner through molecular signals that modulate the malignant phenotype. This article briefly reviews the molecular basis of melanomagenesis as well as the interplay of melanoma with other cells of the tumor microenvironment and components of the ECM. It also discusses the influence of the microenvironment on therapeutic targeting of melanoma, highlighting recent studies that propose novel strategies to target tumor-microenvironment interactions.

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

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

Distinct functions of H-Ras and K-Ras in proliferation and survival of primary hepatocytes due to selective activation of ERK and PI3K

Ras proteins mediate signals both via extracellular signal-regulated kinase 1 and 2 (ERK), and phosphoinositide 3-kinase (PI3K). These signals are key events in cell protection and compensatory cell growth after exposure to cell damaging and pro-apoptotic stimuli, thus maintaining homeostasis. By transfection techniques, we found that both H-Ras and K-Ras were expressed and appeared functionally active in primary hepatocytes. We compared the ability of H-Ras and K-Ras homologues to preferentially activate one of the two pathways, thereby differentially controlling cell survival and growth. We found that ectopic expression of dominant negative (DN) H-RasN17, but not DN K-RasN17, efficiently inhibited both phosphorylation and translocation of ERK to the nuclear compartment, which are prerequisites for cell cycle progression. Furthermore, ectopic expression of constitutive active (CA) H-RasV12, but not CA K-RasV12, potentiated EGF-induced proliferation. We also found that expression of CA mutants of either H-Ras or K-Ras protected hepatocytes from transforming growth factor-beta1 (TGF-beta1)-induced apoptosis. However, H-Ras-induced survival was mediated by ERK/RSK as well as by PI3K, whereas K-Ras-induced survival was mediated by PI3K only. In conclusion, H-Ras and K-Ras had differential functions in proliferation and survival of primary hepatocytes. H-Ras was the major mediator of ERK-induced proliferation and survival, whereas H-Ras and K-Ras both mediated PI3K-induced survival.

A structural model of the extracellular domain of the oncogenic EGFR variant Xmrk

The epidermal growth factor receptor (EGFR) variant Xmrk of the Mexican fish Xiphophorus is one of the first oncogenes described. Its overexpression in pigment cells of the skin occurs after certain repeated cross-breedings between the platyfish Xiphophorus maculatus and the swordtail Xiphophorus hellerii. Xmrk overexpression results in melanoma with a high malignant potential. The Xiphophorus melanoma model provides a valuable tool for the understanding of melanoma development in general. The xmrk gene is the duplicated version of the proto-oncogene egfr-b. Compared to this, it contains 14 nonsynonymous mutations. Two of these mutations lead to a permanent protein dimerization which results in constitutive signaling. For a better understanding of the structural conditions responsible for this effect, the authors modeled the extracellular domain of Egfr-b, based on the crystal structure of the closely related human EGFR, and introduced the mutations G336R or C555S. The resulting protein models show that in either mutation the formation of an intramolecular disulfide bridge is very likely prevented, leading to an intermolecular disulfide bridge between released cysteine residues. In the G336R model, the distance between the membrane-proximal domains from both chains is smaller than in the C555S model, confirming the previous observation than Egfr-b-G336R is more tumorigenic than Egfr-b-C555S in vivo.

p38alpha MAP kinase is essential in lung stem and progenitor cell proliferation and differentiation

Stem cell function is central for the maintenance of normal tissue homeostasis. Here we show that deletion of p38alpha mitogen-activated protein (MAP) kinase in adult mice results in increased proliferation and defective differentiation of lung stem and progenitor cells both in vivo and in vitro. We found that p38alpha positively regulates factors such as CCAAT/enhancer-binding protein that are required for lung cell differentiation. In addition, p38alpha controls self-renewal of the lung stem and progenitor cell population by inhibiting proliferation-inducing signals, most notably epidermal growth factor receptor. As a consequence, the inactivation of p38alpha leads to an immature and hyperproliferative lung epithelium that is highly sensitized to K-Ras(G12V)-induced tumorigenesis. Our results indicate that by coordinating proliferation and differentiation signals in lung stem and progenitor cells, p38alpha has a key role in the regulation of lung cell renewal and tumorigenesis.

RaLP, a New Member of the Src Homology and Collagen Family, Regulates Cell Migration and Tumor Growth of Metastatic Melanomas

The Src homology and collagen (Src) family of adaptor proteins comprises six Shc-like proteins encoded by three loci in mammals (Shc, Rai, and Sli). Shc-like proteins are tyrosine kinase substrates, which regulate diverse signaling pathways and cellular functions, including Ras and proliferation (p52/p46Shc), phosphatidylinositol 3-kinase and survival (p54Rai), and mitochondrial permeability transition and apoptosis (p66Shc). Here, we report the identification, cloning, and sequence characterization of a new member of the Shc family that we termed RaLP. RaLP encodes a 69-kDa protein characterized by the CH2-PTB-CH1-SH2 modularity, typical of the Shc protein family, and expressed, among adult tissues, only in melanomas. Analysis of RaLP expression during the melanoma progression revealed low expression in normal melanocytes and benign nevi, whereas high levels of RaLP protein were found at the transition from radial growth phase to vertical growth phase and metastatic melanomas, when tumor cells acquire migratory competence and invasive potential. Notably, silencing of RaLP expression in metastatic melanomas by RNA interference reduced tumorigenesis in vivo. Analysis of RaLP in melanoma signal transduction pathways revealed that (a) when ectopically expressed in RaLP-negative melanocytes and nonmetastatic melanoma cells, it functions as a substrate of activated insulin-like growth factor-1 and epidermal growth factor receptors and increases Ras/mitogen-activated protein kinase (MAPK) signaling and cell migration, whereas (b) its silencing in RaLP-positive melanoma cells abrogates cell migration in vitro, without affecting MAPK signaling, suggesting that RaLP activates both Ras-dependent and Ras-independent migratory pathways in melanomas. These findings indicate that RaLP is a specific marker of metastatic melanomas, a critical determinant in the acquisition of the migratory phenotype by melanoma cells, and a potential target for novel anti-melanoma therapeutic strategies.

Human adult epidermal melanocytes cultured without chemical mitogens express the EGF receptor and respond to EGF

We describe a novel chemical mitogen-free in vitro culture technique for obtaining pure melanocyte cultures using normal human adult epidermis as a source. The culture medium consists equal parts of the commercially available Keratinocyte Basal and AIM-V media (both from Gibco), as basal medium, which is supplemented with fetal bovine serum, bovine pituitary extract and recombinant human epidermal growth factor (EGF). Melanocytes harvested from human adult skin proliferate extensively and can be passaged serially up to 10-15 times using this medium. We have verified the identity of the cultured cells by tyrosinase mRNA expression and TRP-1 protein staining. Moreover, we showed that autologous human serum alone, without additional supplements is able to provide sufficient growth support for the cultured cells in the basal medium, making this culture technique suitable for autologous melanocyte transplantation. In this culture system normal human adult melanocytes expressed both EGF receptor (EGFR) mRNA and protein and EGF showed a dose dependent mitogenic effect on the cells. EGF itself had no significant influence on EGFR mRNA expression.

The EGF A61G Polymorphism Is Associated with Disease-Free Period and Survival in Malignant Melanoma

An earlier study reported that a common polymorphism in the 5' untranslated region of the epidermal growth factor (EGF) gene is associated with increased risk for cutaneous malignant melanoma (MM) and Breslow thickness. Since then, several independent studies have reported conflicting results that have challenged this hypothesis. However, none of the previous studies examined survival as the primary outcome. We therefore sought to study the association between this polymorphism and survival. One hundred and thirty patients diagnosed with MM with a Breslow thickness of >1.5 mm were included in this study. In our collective, the G/G genotype represented a significant risk factor for both shorter disease-free period (hazard ratio of 2.246, 95% CI: 1.06-4.78, P=0.036) and overall MM-specific survival (hazard ratio of 3.8, 95% CI: 1.5-9.5, P=0.004) compared with the A/A genotype, while the heterozygous A/G genotype showed an intermediate risk. In the present study, we demonstrate for the first time that the EGF A61G polymorphism is associated with survival. Our data suggest that this polymorphism is a potential marker for disease severity that predicts earlier progression of MM.

Malignant melanoma: genetics and therapeutics in the genomic era

Cell for cell, probably no human cancer is as aggressive as melanoma. It is among a handful of cancers whose dimensions are reported in millimeters. Tumor thickness approaching 4 mm presents a high risk of metastasis, and a diagnosis of metastatic melanoma carries with it an abysmal median survival of 6-9 mo. What features of this malignancy account for such aggressive behavior? Is it the migratory history of its cell of origin or the programmed adaptation of its differentiated progeny to environmental stress, particularly ultraviolet radiation? While the answers to these questions are far from complete, major strides have been made in our understanding of the cellular, molecular, and genetic underpinnings of melanoma. More importantly, these discoveries carry profound implications for the development of therapies focused directly at the molecular engines driving melanoma, suggesting that we may have reached the brink of an unprecedented opportunity to translate basic science into clinical advances. In this review, we attempt to summarize our current understanding of the genetics and biology of this disease, drawing from expanding genomic information and lessons from development and genetically engineered mouse models. In addition, we look forward toward how these new insights will impact on therapeutic options for metastatic melanoma in the near future.

Genetics and biology of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death in the United States with a median survival of <6 mo and a dismal 5-yr survival rate of 3%-5%. The cancer's lethal nature stems from its propensity to rapidly disseminate to the lymphatic system and distant organs. This aggressive biology and resistance to conventional and targeted therapeutic agents leads to a typical clinical presentation of incurable disease at the time of diagnosis. The well-defined serial histopathologic picture and accompanying molecular profiles of PDAC and its precursor lesions have provided the framework for emerging basic and translational research. Recent advances include insights into the cancer's cellular origins, high-resolution genomic profiles pointing to potential new therapeutic targets, and refined mouse models reflecting both the genetics and histopathologic evolution of human PDAC. This confluence of developments offers the opportunity for accelerated discovery and the future promise of improved treatment.

NF-kappaB activation in melanoma

Metastatic melanoma is an aggressive skin cancer that is notoriously resistant to current cancer therapies. In human melanoma, nuclear factor-kappa B (NF-kappaB) is upregulated, leading to the deregulation of gene transcription. In this review, we discuss (i) the relationship between gene alteration in melanoma and upregulation of NF-kappaB, (ii) mechanisms by which activated NF-kappaB switch from pro-apoptotic to anti-apoptotic functions in melanoma and (iii) autocrine mechanisms that promote constitutive activation of NF-kappaB in metastatic melanoma.

Tailoring Ras-pathway--inhibitor combinations for cancer therapy

Constitutive activation of Ras pathways plays a critical role in cancer development and maintenance. Inhibitors of such pathways are already in use for cancer therapy, with significant but as yet only partial success in the most deadly types of human cancers, against which even combinations of Ras-pathway inhibitors with classic cytotoxic drugs or irradiation are insufficient. Combinations of farnesyl transferase inhibitors (FTI's), inhibitors of Ras pathways, are now in use in clinical trials. In this review we analyze possible reasons for the limited efficacy--including the diverse and sometimes even contradictory effects of active Ras pathways in tumor cells--and propose possible alternative methods of tailoring Ras-pathway inhibitor combinations for cancer therapy. Such tailoring is now possible thanks to increased knowledge of the complexity of Ras pathways, their cooperation with other oncogenic pathways, and their "addictive" nature. We provide examples demonstrating that this knowledge can be translated into useful drug combinations that disrupt multiple oncogenic pathways and hit a weak point of a given tumor cell. One such example is combination treatment with a Ras inhibitor and a glycolysis blocker for pancreatic tumor cells. The future design of such potential drug combination therapies and the follow-up of their outcome will undoubtedly be facilitated by gene-expression profiling and proteomic methods.