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

Exploring the Binding Mechanism of NRG1-ERBB3 Complex and Discovery of Potent Natural Products to Reduce Diabetes-Assisted Breast Cancer Progression

Diabetes mellitus significantly contributes to breast cancer progression, where hyperglycemia upregulates specific genes, leading to more aggressive tumor growth. In patients with BC that develop diabetes, neuregulin 1 (NRG1) and epidermal growth factor receptor 3 (ERBB3) overexpression exacerbate tumor growth and progression. Since the interaction between NRG1 and ERBB3 is critical for tumor growth, understanding the molecular mechanisms underlying NRG1-ERBB3 complex formation is essential for elucidating diabetes-assisted breast cancer progression. However, the key residues forming the NRG1-ERBB3 complex remain unknown. Here, we substituted specific residues in NRG1 with alanine and studied its interactions with ERBB3 using computational structural biology tools. We further screened the South African natural compounds database to target the complex's interface residues to discover potential inhibitors. The conformational stability and dynamic features of NRG1-WT, -H2A, -L3A, and -K35A complexed with ERBB3 were subjected to 400 ns molecular dynamics simulations. The free binding energies of all NRG1-ERBB3 complexes were calculated using the molecular mechanics-generalized Born surface area (MM/GBSA). The H2 and L3 alanine substitutions caused a loss of interaction with ERBB3 residue D73, weakening the interaction with ERBB3. Screening 1300 natural compounds identified four (SANC00643, SANC00824, SANC00975, and SANC00335) with the best potential to inhibit ERRB3-NRG1 coupling. The binding free energies for each complex were - 48.55 kcal/mol for SANC00643, - 47.68 kcal/mol for SANC00824, - 46.04 kcal/mol for SANC00975, and - 45.29 kcal/mol for SANC00335, showing their overall stronger binding with ERBB3 than NRG1 and their potential to act as ERBB3-NRG1 complex inhibitors. In conclusion, this complex may represent a residue-specific drug target to inhibit BC progression.

UHRF2 promotes Hepatocellular Carcinoma Progression by Upregulating ErbB3/Ras/Raf Signaling Pathway

Emerging evidence revealed that UHRF2 was implicated in a variety of human diseases, especially in cancer. However, the biological function, clinical significance and underly mechanisms of UHRF2 in hepatocellular carcinoma (HCC) is largely unknown. We analyzed the expression of UHRF2 in 371 HCC tissues and 50 para-cancerous tissues of TCGA database. We found that UHRF2 was significantly upregulated in HCC tissues, which was further confirmed in HCC cells and tissues by western blot. More importantly, the level of UHRF2 was correlated with pathological grade and clinical stage, and the patients with high level of UHRF2 had lower overall survival, disease-free survival and higher recurrence rate than those with low UHRF2 level. Univariate and multivariate Cox regression analysis revealed that high level of UHRF2 might be an independent prognostic factor for HCC patients. Functional investigations suggested that ectopic expression of UHRF2 could promote the proliferation, migration and invasion of HCC cell lines, whereas knock down of UHRF2 exhibited an opposite effect. Additionally, gene set enrichment analysis indicated that ERBB signaling pathway was upregulated in patients with high level of UHRF2. Pearson correlation analysis indicated that the expression of UHRF2 was positively correlated with ErbB3 and its downstream targets SOS1, Ras and Raf-1. Furthermore, we found that overexpression of UHRF2 could upregulate the expression of ErbB3, SOS1, Ras and Raf-1. Our findings suggested that UHRF2 might accelerate HCC progression by upregulating ErbB3/Ras/Raf signaling pathway and it might serve as a diagnostic marker and therapeutic target for HCC patients.

Genetic alteration of Chinese patients with rectal mucosal melanoma

Background

Rectal mucosal melanoma (RMM) is a rare and highly aggressive disease with a poor prognosis. Due to the rarity of RMM, there are few studies focusing on its genetic mechanism. This retrospective study aimed to analyze the genetic spectrum and prognosis of RMM in China and lay a foundation for targeted therapy.

Methods

36 patients with primary RMM from Peking University Cancer Hospital were enrolled in this study. The Next-generation sequencing (NGS) data of the tumor samples were fitted into the TruSight™ Oncology 500 (TSO500) Docker pipeline to detect genomic variants. Then, the univariate and multivariate Cox hazard analysis were performed to evaluate the correlations of the variants with the overall survival (OS), along with Kaplan-Meier and log-rank test to determine their significance.

Results

BRAF mutations, NRG1 deletions and mitotic index were significant prognostic factors in the univariate analysis. In multivariable analysis of the OS-related prognostic factors in primary RMM patients, it revealed 2 significant alterations: BRAF mutations [HR 7.732 (95%CI: 1.735–34.456), P = 0.007] and NRG1 deletions [HR 14.976 (95%CI: 2.305–97.300), P = 0.005].

Conclusions

This is the first study to show genetic alterations exclusively to Chinese patients with RMM. We confirmed genetic alterations of RMM differ from cutaneous melanoma (CM). Our study indicates that BRAF and NRG1 were correlated with a poor prognostic of RMM and may be potential therapeutic targets for RMM treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08383-6.

Personalized and targeted mutational analysis of multiple second primary melanomas under kinase inhibitors

BACKGROUND

Second primary melanomas (SPMs) are new developed primary melanomas occurring in a subset of patients affected by BRAF-mutated metastatic melanoma during treatment with BRAF-inhibitors. A drug-induced paradoxical activation of mitogen-activated protein kinase (MAPK) signaling pathway in BRAF-wild type/RAS-mutated cells have been proposed as a possible molecular mechanism but data on the mutational status of SPMs are lacking. In order to better understand genetic alterations affecting the biological mechanism of SPMs, we performed a personalized and targeted next-generation sequencing analysis of a patient affected by metastatic melanoma who developed multiple SPMs during treatment with encorafenib (LGX818).

METHODS

Using a cancer panel of 50 genes for solid tumors enriched with a custom panel of 10 genes specifically involved in melanoma pathogenesis, we analyzed the primary melanoma, two SPMs, one benign compound nevus and the normal DNA extracted from blood lymphocytes of the patient.

RESULTS

We identified HRAS Q61 somatic mutation in one SPM developed in a pre-existing nevus. In the primary melanoma, besides the BRAF mutation, we identified the clinically actionable IDH1 R132C somatic mutation. Both SPMs were BRAF wild type. The patient harbors the recently recognized pathogenetic germline variant KDR Q472. We observed that mutations detected in tumor samples involving genes related to melanoma pathogenesis (TP53, PIK3CA, FGFR3, ATF1, KIT, HRAS and MAP2K2) were present in heterozygosis in the germline status of the patient.

CONCLUSIONS

Our results support the paradoxical mechanism of MAPK pathway for SPMs under BRAF inhibitors. Moreover, they suggest that targeted mutational assessment based on matching somatic and germline analysis represent a promising approach to detect the neoplastic landscape of the tumor and to identify most accurate treatment in metastatic melanoma patient.

Functional interplay between secreted ligands and receptors in melanoma

Melanoma, the most aggressive form of skin cancer, results from the malignant transformation of melanocytes located in the basement membrane separating the epidermal and dermal skin compartments. Cutaneous melanoma is often initiated by solar ultraviolet radiation (UVR)-induced mutations. Melanocytes intimately interact with keratinocytes, which provide growth factors and melanocortin peptides acting as paracrine regulators of proliferation and differentiation. Keratinocyte-derived melanocortins activate melanocortin-1 receptor (MC1R) to protect melanocytes from the carcinogenic effect of UVR. Accordingly, MC1R is a major determinant of susceptibility to melanoma. Despite extensive phenotypic heterogeneity and high mutation loads, the molecular basis of melanomagenesis and the molecules mediating the crosstalk between melanoma and stromal cells are relatively well understood. Mutations of intracellular effectors of receptor tyrosine kinase (RTK) signalling, notably NRAS and BRAF, are major driver events more frequent than mutations in RTKs. Nevertheless, melanomas often display aberrant signalling from RTKs such as KIT, ERRB1-4, FGFR, MET and PDGFR, which contribute to disease progression and resistance to targeted therapies. Progress has also been made to unravel the role of the tumour secretome in preparing the metastatic niche. However, key aspects of the melanoma-stroma interplay, such as the molecular determinants of dormancy, remain poorly understood.

Oncogenic function and clinical implications of SLC3A2-NRG1 fusion in invasive mucinous adenocarcinoma of the lung

The neuregulin 1 (NRG1) fusion is a recently identified novel driver oncogene in invasive mucinous adenocarcinoma of the lung (IMA). After identification of a case of SLC3A2-NRG1 in a patient with IMA, we verified this fusion gene in a cohort of 59 patients with IMA. Targeted cancer panel sequencing and RT-PCR identified the possible coexistence of other driver oncogenes. Among 59 IMAs, we found 16 NRG1 fusions (13 SLC3A2-NRG1 and 3 CD74-NRG1). Of 16 patients with NRG1 fusions, concurrent KRAS codon 12 mutations were found in 10 cases. We also found concurrent NRAS Q61L mutation and EML4-ALK fusion in additional two cases with NRG1 fusions. When comparing overall survival (OS) according to the presence of NRG1 fusions showed that patients harboring NRG1 fusions had significantly inferior OS than those without NRG1 fusions (hazard ratio = 0.286; 95% confidence interval, .094 to .865). Ectopic expression of the SLC3A2-NRG1 fusion in lung cancer cells increased cell migration, proliferation and tumor growth in vitro and in xenograft models, suggesting oncogenic function for the fusion protein. We found that the SLC3A2-NRG1 fusion promoted ERBB2-ERBB3 phosphorylation and heteroduplex formation and activated the downstream PI3K/AKT/mTOR pathway through paracrine signaling. These findings suggested that the SLC3A2-NRG1 fusion was a driver in IMA with an important prognostic impact. SLC3A2-NRG1 should be considered a therapeutic target for patients with IMA.

The natural compound fucoidan from New Zealand Undaria pinnatifida synergizes with the ERBB inhibitor lapatinib enhancing melanoma growth inhibition

Melanoma remains one of the most aggressive and therapy-resistant cancers. Finding new treatments to improve patient outcomes is an ongoing effort. We previously demonstrated that melanoma relies on the activation of ERBB signaling, specifically of the ERBB3/ERBB2 cascade. Here we show that melanoma tumor growth is inhibited by 60% over controls when treated with lapatinib, a clinically approved inhibitor of ERBB2/EGFR. Importantly, tumor growth is further inhibited to 85% when the natural compound fucoidan from New Zealand U. pinnatifida is integrated into the treatment regimen. Fucoidan not only enhances tumor growth inhibition, it counteracts the morbidity associated with prolonged lapatinib treatment. Fucoidan doubles the cell killing capacity of lapatinib. These effects are associated with a further decrease in AKT and NFκB signaling, two key pathways involved in melanoma cell survival. Importantly, the enhancing cell killing effects of fucoidan can be recapitulated by inhibiting ERBB3 by either a specific shRNA or a novel, selective ERBB3 neutralizing antibody, reiterating the key roles played by this receptor in melanoma. We therefore propose the use of lapatinib or specific ERBB inhibitors, in combination with fucoidan as a new treatment of melanoma that potentiates the effects of the inhibitors while protecting from their potential side effects.

miR-200c Regulation of Metastases in Ovarian Cancer: Potential Role in Epithelial and Mesenchymal Transition

Among the gynecological malignancies, ovarian cancer is the most fatal due to its high mortality rate. Most of the identified cases are epithelial ovarian cancer (EOC) with five distinct subtypes: high-grade serous carcinoma, low-grade serous carcinoma, mucinous carcinoma, endometrioid carcinoma, and clear-cell carcinoma. Lack of an early diagnostic approach, high incidence of tumor relapse and the heterogenous characteristics between each EOC subtypes contribute to the difficulties in developing precise intervention and therapy for the patients. MicroRNAs (miRNAs) are single-stranded RNAs that have been shown to function as tumor suppressors or oncomiRs. The miR-200 family, especially miR-200c, has been shown to be implicated in the metastasis and invasion of ovarian carcinoma due to its functional regulation of epithelial-to-mesenchymal transition (EMT). This mini review is aimed to summarize the recent findings of the miR-200c functional role as well as its validated targets in the metastasis cascade of ovarian cancer, with a focus on EMT regulation. The potential of this miRNA in early diagnosis and its dual expression status are also discussed.

Combinatorial drug screening and molecular profiling reveal diverse mechanisms of intrinsic and adaptive resistance to BRAF inhibition in V600E BRAF mutant melanomas

Over half of BRAFV600E melanomas display intrinsic resistance to BRAF inhibitors, in part due to adaptive signaling responses. In this communication we ask whether BRAFV600E melanomas share common adaptive responses to BRAF inhibition that can provide clinically relevant targets for drug combinations. We screened a panel of 12 treatment-naïve BRAFV600E melanoma cell lines with MAP Kinase pathway inhibitors in pairwise combination with 58 signaling inhibitors, assaying for synergistic cytotoxicity. We found enormous diversity in the drug combinations that showed synergy, with no two cell lines having an identical profile. Although the 6 lines most resistant to BRAF inhibition showed synergistic benefit from combination with lapatinib, the signaling mechanisms by which this combination generated synergistic cytotoxicity differed between the cell lines. We conclude that adaptive responses to inhibition of the primary oncogenic driver (BRAFV600E) are determined not only by the primary oncogenic driver but also by diverse secondary genetic and epigenetic changes ("back-seat drivers") and hence optimal drug combinations will be variable. Because upregulation of receptor tyrosine kinases is a major source of drug resistance arising from diverse adaptive responses, we propose that inhibitors of these receptors may have substantial clinical utility in combination with inhibitors of the MAP Kinase pathway.

Synchronized Targeting of Notch and ERBB Signaling Suppresses Melanoma Tumor Growth through Inhibition of Notch1 and ERBB3

Despite significant advances in melanoma therapy, melanoma remains the deadliest form of skin cancer, with a 5-year survival rate of only 15%. Thus, novel treatments are required to address this disease. Notch and ERBB are evolutionarily conserved signaling cascades required for the maintenance of melanocyte precursors. We show that active Notch1 (Notch1(NIC)) and active (phosphorylated) ERBB3 and ERBB2 correlate significantly and are similarly expressed in both mutated and wild-type BRAF melanomas, suggesting these receptors are co-reactivated in melanoma to promote survival. Whereas blocking either pathway triggers modest effects, combining a ?-secretase inhibitor to block Notch activation and a tyrosine kinase inhibitor to inhibit ERBB3/2 elicits synergistic effects, reducing cell viability by 90% and hampering melanoma tumor growth. Specific inhibition of Notch1 and ERBB3 mimics these results, suggesting these are the critical factors triggering melanoma tumor expansion. Notch and ERBB inhibition blunts AKT and NF?B signaling. Constitutive expression of NF?B partially rescues cell death. Blockade of both Notch and ERBB signaling inhibits the slow cycling JARID1B-positive cell population, which is critical for long-term maintenance of melanoma growth. We propose that blocking these pathways is an effective approach to treatment of melanoma patients regardless of whether they carry mutated or wild-type BRAF.

Systems Analysis of Adaptive Responses to MAP Kinase Pathway Blockade in BRAF Mutant Melanoma

Fifty percent of cutaneous melanomas are driven by activated BRAF^V600E, but tumors treated with RAF inhibitors, even when they respond dramatically, rapidly adapt and develop resistance. Thus, there is a pressing need to identify the major mechanisms of intrinsic and adaptive resistance and develop drug combinations that target these resistance mechanisms. In a combinatorial drug screen on a panel of 12 treatment-naïve BRAF^V600E mutant melanoma cell lines of varying levels of resistance to mitogen-activated protein kinase (MAPK) pathway inhibition, we identified the combination of PLX4720, a targeted inhibitor of mutated BRaf, and lapatinib, an inhibitor of the ErbB family of receptor tyrosine kinases, as synergistically cytotoxic in the subset of cell lines that displayed the most resistance to PLX4720. To identify potential mechanisms of resistance to PLX4720 treatment and synergy with lapatinib treatment, we performed a multi-platform functional genomics analysis to profile the genome as well as the transcriptional and proteomic responses of these cell lines to treatment with PLX4720. We found modest levels of resistance correlated with the zygosity of the BRAF V600E allele and receptor tyrosine kinase (RTK) mutational status. Layered over base-line resistance was substantial upregulation of many ErbB pathway genes in response to BRaf inhibition, thus generating the vulnerability to combination with lapatinib. The transcriptional responses of ErbB pathway genes are associated with a number of transcription factors, including ETS2 and its associated cofactors that represent a convergent regulatory mechanism conferring synergistic drug susceptibility in the context of diverse mutational landscapes.

Orchestration of ErbB3 signaling through heterointeractions and homointeractions

Members of the ErbB family of receptor tyrosine kinases are capable of both homointeractions and heterointeractions. Because each receptor has a unique set of binding sites for downstream signaling partners and differential catalytic activity, subtle shifts in their combinatorial interplay may have a large effect on signaling outcomes. The overexpression and mutation of ErbB family members are common in numerous human cancers and shift the balance of activation within the signaling network. Here we report the development of a spatial stochastic model that addresses the dynamics of ErbB3 homodimerization and heterodimerization with ErbB2. The model is based on experimental measures for diffusion, dimer off-rates, kinase activity, and dephosphorylation. We also report computational analysis of ErbB3 mutations, generating the prediction that activating mutations in the intracellular and extracellular domains may be subdivided into classes with distinct underlying mechanisms. We show experimental evidence for an ErbB3 gain-of-function point mutation located in the C-lobe asymmetric dimerization interface, which shows enhanced phosphorylation at low ligand dose associated with increased kinase activity.

Fibroblast-derived neuregulin 1 promotes compensatory ErbB3 receptor signaling in mutant BRAF melanoma

Rapidly accelerated fibrosarcoma (RAF) inhibitors are first-line treatments for patients harboring V600E/K mutant BRAF melanoma. Although RAF inhibitors produce high response rates, the degree of tumor regression is heterogeneous. Compensatory/adaptive responses to targeted inhibitors are frequently initiated by the activation of growth factor receptor tyrosine kinases, including ErbB3, and factors from the tumor microenvironment may play an important role. We have shown previously that mutant v-raf murine sarcoma viral oncogene homolog B1 (BRAF) melanoma cells have enhanced activation of ErbB3 following RAF inhibition. However, the source of neuregulin 1 (NRG1), the ligand for ErbB3, is unknown. In this study, we demonstrate that NRG1 is highly expressed by dermal fibroblasts and cancer-associated fibroblasts (CAFs) isolated from mutant BRAF melanomas. Conditioned medium from fibroblasts and CAFs enhanced ErbB3 pathway activation and limited RAF inhibitor cytotoxicity in V600 mutant BRAF-harboring melanomas. Targeting the ErbB3/ErbB2 pathway partially reversed the protective effects of fibroblast/CAF-derived NRG1 on cell growth properties of RAF inhibitor-treated melanoma cells. These findings support the idea that NRG1, acting in a paracrine manner, promotes resistance to RAF inhibitors and emphasize that targeting the ErbB3/ErbB2 pathway will likely improve the efficacy of RAF inhibitors for mutant BRAF melanoma patients.

The broad-spectrum receptor tyrosine kinase inhibitor dovitinib suppresses growth of BRAF-mutant melanoma cells in combination with other signaling pathway inhibitors

BRAF inhibitors have revolutionized treatment of mutant BRAF metastatic melanomas. However, resistance develops rapidly following BRAF inhibitor treatment. We have found that BRAF-mutant melanoma cell lines are more sensitive than wild-type BRAF cells to the small molecule tyrosine kinase inhibitor dovitinib. Sensitivity is associated with inhibition of a series of known dovitinib targets. Dovitinib in combination with several agents inhibits growth more effectively than either agent alone. These combinations inhibit BRAF-mutant melanoma and colorectal carcinoma cell lines, including cell lines with intrinsic or selected BRAF inhibitor resistance. Hence, combinations of dovitinib with second agents are potentially effective therapies for BRAF-mutant melanomas, regardless of their sensitivity to BRAF inhibitors.

The role of microRNAs and long non-coding RNAs in the pathology, diagnosis, and management of melanoma

Melanoma is frequently lethal and its global incidence is steadily increasing. Despite the rapid development of different modes of targeted treatment, durable clinical responses remain elusive. A complete understanding of the molecular mechanisms that drive melanomagenesis is required, both genetic and epigenetic, in order to improve prevention, diagnosis, and treatment. There is increased appreciation of the role of microRNAs (miRNAs) in melanoma biology, including in proliferation, cell cycle, migration, invasion, and immune evasion. Data are also emerging on the role of long non-coding RNAs (lncRNAs), such as SPRY4-IT1, BANCR, and HOTAIR, in melanomagenesis. Here we review the data on the miRNAs and lncRNAs implicated in melanoma biology. An overview of these studies will be useful for providing insights into mechanisms of melanoma development and the miRNAs and lncRNAs that might be useful biomarkers or future therapeutic targets.

Melanoma: clinical features and genomic insights

Recent efforts in genomic research have enabled the characterization of molecular mechanisms underlying many types of cancers, ushering novel approaches for diagnosis and therapeutics. Melanoma is a molecularly heterogeneous disease, as many genetic alterations have been identified and the clinical features can vary. Although discoveries of frequent mutations including BRAF have already made clinically significant impact on patient care, there is a growing body of literature suggesting a role for additional mutations, driver and passenger types, in disease pathophysiology. Although some mutations have been strongly associated with clinical phenotypes of melanomas (such as physical distribution or morphologic subtype), the function or implications of many of the recently identified mutations remains less clear. The phenotypic and clinical impact of genomic mutations in melanoma remains a promising opportunity for progress in the care of melanoma patients.

ERBB3 is required for metastasis formation of melanoma cells

Melanoma is curable when it is at an early phase but is lethal once it becomes metastatic. The recent development of BRAF(V600E) inhibitors (BIs) showed great promise in treating metastatic melanoma, but resistance developed quickly in the treated patients, and these inhibitors are not effective on melanomas that express wild-type BRAF. Alternative therapeutic strategies for metastatic melanoma are urgently needed. Here we report that ERBB3, a member of the epidermal growth factor receptor family, is required for the formation of lung metastasis from both the BI-sensitive melanoma cell line, MA-2, and the BI-resistant melanoma cell line, 451Lu-R. Further analyses revealed that ERBB3 does not affect the initial seeding of melanoma cells in lung but is required for their further development into overt metastases, indicating that ERBB3 might be essential for the survival of melanoma cells after they reach the lung. Consistent with this, the ERBB3 ligand, NRG1, is highly expressed in mouse lungs and induces ERBB3-depdnent phosphorylation of AKT in both MA-2 and 451Lu-R cells in vitro. These findings suggest that ERBB3 may serve as a target for treating metastatic melanomas that are resistant to BIs. In support of this, administration of the pan-ERBB inhibitor, canertinib, significantly suppresses the metastasis formation of BI-resistant melanoma cell lines.

Comparative analysis of melanoma deregulated miRNAs in the medaka and Xiphophorus pigment cell cancer models

Malignant melanoma is the most aggressive and deadly form of skin cancer, with an almost 100% development of resistance to current therapeutic approaches at progression stages. The incidence of melanoma is steadily increasing worldwide. Although many details leading to the development of malignant melanoma are known, the complex process of melanomagenesis is poorly understood. MicroRNAs (miRNAs) are a class of small noncoding-RNAs of ~22nt length that regulate gene expression at the post-transcriptional level. It is now well established that deregulated miRNA expression is seen in many cancers including melanoma. To further study the miRNA functions in melanoma formation and progression we use a transgenic melanoma model in Japanese ricefish (medaka; Oryzias latipes) and the natural Xiphophorus melanoma model. In these fishes, dependent on the genetic background various histo- and patho-types of tumors appear, comparable to human melanoma types. We have studied expression profiles of ten known human melanoma-associated miRNAs and their respective target gene expression in the fish melanoma models. We show that miRNAs of the miR-17-92 cluster (miR-20a2, miR-92a1, miR-17 and miR-18a), miR-126, miR-182, miR-210 and miR-214 are upregulated and their respective target genes (RUNX1, HIF1A, TGFBR2, THBS1 and JAK2) are down-regulated in melanoma. MicroRNA-125b is down-regulated and the target genes (ERBB3a and ERBB3b) are upregulated in fish melanomas. Results provide clear evidence that the fish melanoma-associated miRNAs and respective target genes are deregulated generally like in human melanoma. Our results confirm the value of fish; such as medaka and Xiphophorus as good model systems to identify and decipher molecular mechanisms associated with malignant melanoma.

Notch signaling in melanoma: interacting pathways and stromal influences that enhance Notch targeting

The Notch signaling pathway is an evolutionarily conserved, intercellular signaling cascade. Notch was first described in the early 1900s when a mutant Drosophila showed notches on the wing margins. Studies of the role of Notch signaling have ever since flourished, and the pleiotropic nature of the Notch gene is now evident. Indeed, the Notch signaling pathway plays key roles in cell fate decisions, tissue patterning, and morphogenesis during development. However, deregulation of this pathway can contribute to cell transformation and tumorigenesis. Several reports have now highlighted the role of Notch signaling in a variety of malignancies where Notch can either be an oncogene or a tumor suppressor depending on the cell context. Here, we summarize the major components of Notch signaling with an aim to emphasize the contribution of deregulated Notch signaling in melanomagenesis.