Potential Target For Melanoma Therapy Research Articles

RIPK4 downregulation impairs Wnt3A-stimulated invasiveness via Wnt/β-catenin signaling in melanoma cells and tumor growth in vivo.

The role of Wnt signaling in oncogenesis and drug resistance is well known. Receptor-interacting protein kinase (RIPK4) contributing to the increased activity of many signaling pathways, including Wnt/β-catenin, may be an important target for designing new drugs for metastatic melanoma, but its role in melanoma is not fully understood. We tested the effect of genetic manipulation of RIPK4 (CRISPR/Cas9) on xenograft growth. In addition, immunohistochemistry was used to detect active β-catenin, Ki67 and necrosis in xenografts. Wnt signaling pathway activity was examined using Western blot and Top-Flash. The effect of RIPK4 knockout on melanoma cells in vitro stimulated Wnt3A on wound overgrowth, migration and invasion ability was then evaluated. Our study showed that CRISPR/Cas9-mediated RIPK4 knockout (KO) significantly reduced tumor growth in a mouse model of melanoma, particularly of WM266.4 cells. RIPK4 KO tumors exhibited lower percentages of Ki67+ cells as well as reduced necrotic area and decreased levels of active β-catenin. In addition, we observed that RIPK4 knockout impaired Wnt3A-induced activation of LRP6 and β-catenin, as manifested by a decrease in the transcriptional activity of β-catenin in Top-Flash in both tested melanoma cell lines, A375 and WM266.4. Prolonged incubation (48h) with Wnt3A showed reduced level of MMP9, C-myc, and increased SOX10, proteins whose transcription is also dependent on β-catenin activity. Moreover, RIPK4 knockout led to the inhibition of scratch overgrowth, migration and invasion of these cells compared to their controls. RIPK4 knockdown inhibits melanoma tumor growth and Wnt3A stimulated migration and invasion indicating that RIPK4 might be a potential target for melanoma therapy.

Targeted Nanotherapeutics Using LACTB Gene Therapy Against Melanoma.

Introductionβ-lactamase (LACTB) is a tumor suppressor gene in various tumors including melanoma. However, it remains challenging to efficiently deliver the LACTB gene into melanoma. Recently, we designed a nonviral nanocarrier iRGD/DOTAP/MPEG-PDLLA (iDPP) that could deliver gene targetedly to melanoma efficiently without obvious adverse effects.MethodsIn this study, the tumor-targeted nanoparticle iDPP was prepared to deliver LACTB gene to treat melanoma in vitro and in vivo. First, the expression level of LACTB in 6 clinical specimens of melanoma patients was evaluated. Subsequently, the characteristics of iDPP/LACTB nanocomplexes were studied. Afterwards, the in vitro and in vivo anti-tumor efficacy of the iDPP/LACTB nanocomplexes were explored utilizing the B16-F10 mouse melanoma cell line and the B16-F10 subcutaneous melanoma model.ResultsCompared with the normal epithelium, the expression level of LACTB in melanoma tissues was significantly downregulated. In vitro B16-F10 cell tests showed iDPP/LACTB nanocomplexes could increase the mRNA levels of P21, Bid, Bax, Pidd1, and Sival genes and up-regulate the p53 signaling pathway of melanoma cells, thus promoting cell apoptosis and blocking the cell cycle. Injected intravenously, iDPP nanoparticles could deliver DNA to the subcutaneous melanoma targetedly. Based on in vivo mouse xenograft model, iDPP/LACTB nanocomplexes could effectively inhibit tumor proliferation and induce tumor apoptosis, thus significantly inhibiting melanoma growth (tumor inhibition rate is about 68%) in the subcutaneous B16-F10 melanoma model.ConclusionThe downregulated LACTB might be a potential target for melanoma therapy. The iDPP/LACTB nanocomplexes could inhibit the growth of the mouse melanoma without obvious side effects, which provide a new option for melanoma gene therapy research.

Single-cell RNA-sequencing analyses identify heterogeneity of CD8+ T cell subpopulations and novel therapy targets in melanoma

CD8+ T cells are crucial to establish antitumor immunity, and their high infiltration associates with favorable prognoses. However, several CD8+ T cell subpopulations in the tumor microenvironment may play different roles in prognosis, progression, and immunotherapy. Here, we analyzed prior published single-cell RNA-sequencing (scRNA-seq) melanoma data to explore the heterogeneity of CD8+ T cell subpopulations and identified 7 major subpopulations. We found that high infiltration of exhausted CD8+ T cell subpopulation 2 would contribute to unfavorable prognoses. In contrast, a large proportion of naive/memory cells and cytotoxic CD8+ T cell subpopulation 3 would lead to favorable prognoses. Notably, the proportion of the cytotoxic CD8+ T cell subpopulation 3 would decrease in later-stage melanoma samples, while that of the exhausted CD8+ T cell subpopulation 2 would increase. We also found that high abnormal activities of metabolic pathways existed in exhausted CD8+ T cell subpopulation 1. Significantly, immunosuppressive checkpoints PD-1 and CTLA-4 signaling pathways were upregulated in exhausted CD8+ T cell subpopulations. In addition, a dynamic transcript landscape of immune checkpoints among different subpopulations was also depicted in this study. Moreover, we identified three overexpressed genes (PMEL, TYRP1, and EDNRB) that were significantly correlated to poor prognoses and only expressed in exhausted CD8+ T cell subpopulation 2. Importantly, they showed the highest expression in melanoma samples compared to other tumors. In general, we characterized the CD8+ T cell subpopulations in melanoma and identified that not only genes of immunosuppressive checkpoints but also PMEL, TYRP1, and EDNRB could serve as potential targets for melanoma therapy.

THE ROLE OF EPITHELIAL-TO-MESENCHYMAL TRANSITION AND AUTOPHAGY IN ANTITUMORAL RESPONSE OF MELANOMA CELL LINES TO TARGET INHIBITION OF MEK AND mTOR KINASES

Introduction. Cutaneous melanoma is a challenge to treat due to rapid progression of disease and acquired resistance to therapy. Autophagy and the epithelial-to-mesenchymal transition (EMT) are closely interrelated and play a key role in tumor progression. Targeted co-inhibition of MEK and mTOR kinases is a potential target for melanoma therapy by downregulatoin of the EMT.Objective: to study the effect of MEK and mTOR co-inhibition on cell viability, ability to form 3D-spheroids and migratory capacity of melanoma cell lines, and correlation of these changes with EMTand autophagy-related markers.Material and Methods. Melanoma cell lines Mel Z and Mel MTP were derived from patients, who were treated at the N.N. Blokhin National Medical Research Center of Oncology. The antiproliferative effect of binimetinib and/or rapamycin was studied by the MTT -test. 3D spheroids were formed using RGD peptides. Cell migration and invasion were assessed by a Boyden chamber migration assay. The expression levels of autophagy and EMT markers were investigated by immunocytochemistry or immunoblotting.Results. Rapamycin increased cytotoxicity of binimetinib in both 2D and 3D melanoma cell line cultures. At the same time, binimetinib and rapamycin reduced invasion, but not migration capacity of melanoma cells in vitro. The effectiveness of the combination was associated with a decrease in the EMT markers (N-cadherin and β-catenin) and autophagy markers (Beclin 1, p62/SQST M1 and LC3BII ) in melanoma cells.Conclusion. Inactivation of autophagy and EMT leads to overcoming the resistance to current anti-melanoma therapy and can be considered as a promising target for the treatment of melanoma.

THE ROLE OF EPITHELIAL-TO-MESENCHYMAL TRANSITION AND AUTOPHAGY IN ANTITUMORAL RESPONSE OF MELANOMA CELL LINES TO TARGET INHIBITION OF MEK AND mTOR KINASES

Introduction. Cutaneous melanoma is a challenge to treat due to rapid progression of disease and acquired resistance to therapy. Autophagy and the epithelial-to-mesenchymal transition (EMT) are closely interrelated and play a key role in tumor progression. Targeted co-inhibition of MEK and mTOR kinases is a potential target for melanoma therapy by downregulatoin of the EMT.Objective: to study the effect of MEK and mTOR co-inhibition on cell viability, ability to form 3D-spheroids and migratory capacity of melanoma cell lines, and correlation of these changes with EMTand autophagy-related markers.Material and Methods. Melanoma cell lines Mel Z and Mel MTP were derived from patients, who were treated at the N.N. Blokhin National Medical Research Center of Oncology. The antiproliferative effect of binimetinib and/or rapamycin was studied by the MTT -test. 3D spheroids were formed using RGD peptides. Cell migration and invasion were assessed by a Boyden chamber migration assay. The expression levels of autophagy and EMT markers were investigated by immunocytochemistry or immunoblotting.Results. Rapamycin increased cytotoxicity of binimetinib in both 2D and 3D melanoma cell line cultures. At the same time, binimetinib and rapamycin reduced invasion, but not migration capacity of melanoma cells in vitro. The effectiveness of the combination was associated with a decrease in the EMT markers (N-cadherin and β-catenin) and autophagy markers (Beclin 1, p62/SQST M1 and LC3BII ) in melanoma cells.Conclusion. Inactivation of autophagy and EMT leads to overcoming the resistance to current anti-melanoma therapy and can be considered as a promising target for the treatment of melanoma.

Upregulation of LINC00963 facilitates melanoma progression through miR-608/NACC1 pathway and predicts poor prognosis

Long noncoding RNAs (lncRNAs) are acknowledged as crucial regulators involved in multiple pathological processes, including cancer. Although some lncRNAs are studied in melanoma, the association between lncRNA and melanoma progression still remains vague. And the function of LINC00963 in melanoma is waiting for investigation. In this study, upregulated level of LINC00963 in melanoma tissues was observed. Notably, we found DNA copy-number-gain of LINC00963 contributes to its high expression. And high expression of LINC00963 predicts poor prognosis in patients with melanoma. Functional investigation indicated that LINC00963 knockdown dramatically suppressed melanoma cell proliferation, migration and invasion. Mechanistically, we found that LINC00963 could interact with miR-608 while miR-608 could target NACC1. Upregulated LINC00963 led to elevated expression of NACC1 through inhibiting miR-608, which consequently promoted melanoma malignant progression. Taken together, our results illustrated that LINC00963-miR-608-NACC1 pathway might be a potential target for melanoma therapy.

Glutathione reductase-mediated thiol oxidative stress suppresses metastasis of murine melanoma cells

Malignant melanoma is a highly metastatic and life-threatening cancer. Reactive oxygen species (ROS) play important roles in cancer initiation and progression including metastasis. It has been reported that the oxidative stress spontaneously generated in circulating melanoma cells was able to suppress distant metastasis in vivo. However, little is known regarding the effects and mechanism of glutathione reductase (GR) inhibition-induced oxidative stress in regulation of melanoma metastasis. Here, we demonstrate that GR inhibition generates oxidative stress and suppresses lung metastasis and subcutaneous growth of melanoma in vivo. In addition, inhibitory effects by GR activity reduction were observed on cell proliferation, colony formation, cell adhesion, migration and invasion in melanoma cells in vitro. GR inhibition-induced oxidative stress was also found to block epithelial-to-mesenchymal transition (EMT) by decreasing the expression of Vimentin, ERK1/2, transcription factor Snail and increasing the expression of E-cadherin. In addition, actin rearrangement, a key element involved in cell motility, was also affected by GR-mediated oxidative stress possibly through protein S-glutathionylation on actin. In conclusion, this study identifies GR as an effective regulator of oxidative stress that affects the multistep processes of metastasis in melanoma cells, and it becomes a potential target for melanoma therapy.

FAK regulates E-cadherin expression via p-SrcY416/p-ERK1/2/p-Stat3Y705 and PPARγ/miR-125b/Stat3 signaling pathway in B16F10 melanoma cells.

Focal adhesion kinase (FAK) is involved in tumor cell migration and metastasis. However, the underlying mechanism remains unclear. Here, we present a signaling pathway involved in the regulation of melanoma cell migration by FAK. We found that the interference of FAK expression suppressed B16F10 cell migration/metastasis, and altered the expressions of genes involved in melanoma migration/metastasis. The down-regulation of FAK inhibited the expression of p-SrcY416, p-ERK1/2, Stat3 and p-Stat3Y705, while promoted the expression of PPARγ, miR-125b and E-cadherin. Then we found that FAK inhibited E-cadherin expression via p-SrcY416/p-ERK1/2/ p-Stat3Y705 and PPARγ/miR-125b/Stat3 signaling pathway in B16F10 cell. Moreover, miR-125b inhibited B16F10 cell migration. Furthermore, we repeated the key data with human melanoma cell line A375. The results obtained from A375 cells fell in line with those from B16F10 cells. Using Oncomine database, we found that the mRNA levels of FAK, Src, ERK1/2 and Stat3 increased, while the mRNA levels of PPARγ, C21orf34 (miR-125b host gene) and E-cadherin decreased in human metastatic melanoma. The data from human breast cancer confirmed those from metastatic melanoma.Taken together, our study suggests that down-regulation of FAK promotes E-cadherin expression via p-SrcY416/p-ERK1/2/p-Stat3Y705 and PPARγ/miR-125b/Stat3 signaling pathway. Our findings provide a novel explanation regarding how FAK promotes melanoma cell migration, suggesting that FAK might be a potential target for melanoma therapy.

Actin-Binding Protein, Espin: A Novel Metastatic Regulator for Melanoma

Espin is a multifunctional actin-bundling protein with multiple isoforms, and has special connections to hair cell stereocilia and microvillar specializations of sensory cells in the inner ear. However, there have been no reports showing the expression and function of Espin in cancers, including melanoma. Here, it is demonstrated that Espin expression is significantly increased in melanomas that spontaneously developed in RET-transgenic mice (RET-mice). Importantly, the invasion capacity of Espin-depleted Mel-ret melanoma cells derived from a tumor of the RET-mouse was dramatically less than that of control melanoma cells with reductions of lamellipodia, focal adhesion kinase (FAK), and GTP-Rac1 activities. Correspondingly, the ratio of metastatic foci in Espin-depleted Mel-ret melanoma cells was significantly less than that of control melanoma cells in an in vivo melanoma metastasis model. Moreover, Espin could be a novel biomarker of melanoma in humans, because our immunohistochemical analysis data reveal that percentages of Espin-positive cells in human primary and metastatic melanomas were significantly higher than that of cells in melanocytic nevi. Together, these results indicate that Espin is not only a metastatic regulator for melanoma but also a potential biomarker of disease progression. Actin-binding protein Espin is expressed in melanoma, affects metastasis, and is a potential target for melanoma therapy.

BRAFV600E Cooperates with PI3K Signaling, Independent of AKT, to Regulate Melanoma Cell Proliferation

Mutationally activated BRAF(V600E) cooperates with PTEN silencing in the conversion of normal melanocytes to metastatic melanoma cells, but the mechanism underlying this cooperation is poorly understood. Here, the consequences of pharmacologic blockade of BRAF(V600E) or phosphoinositide 3-kinase (PI3K) signaling were explored using pathway-targeted inhibitors and a panel of human BRAF-mutated melanoma-derived cell lines. Blockade of BRAF(V600E) → MEK1/2 → ERK1/2 or class I PI3K inhibited melanoma proliferation, whereas inhibition of AKT had only modest effects, even in cells with mutated or amplified AKT. Although single-agent inhibition of either BRAF(V600E) or PI3K signaling elicited antiproliferative effects, combinatorial inhibition was more potent. Analysis of signaling downstream of BRAF(V600E) or PI3K revealed that these pathways cooperated to regulate protein synthesis through AKT-independent, mTOR complex 1 (mTORC1)-dependent effects on p70(S6K), ribosomal protein S6, and 4E-BP1 phosphorylation. Moreover, inhibition of mTORC1/2 inhibited cell proliferation as profoundly as single-agent inhibition of either BRAF(V600E) or PI3K signaling. These data reveal a mechanism by which BRAF(V600E) and PI3K signaling cooperate to regulate melanoma proliferation through AKT-independent effects on protein translation. Furthermore, this study provides a potential foundation for pathway-targeted combination therapy designed to enhance the therapeutic benefit to patients with melanoma that contain combined alterations in BRAF and PI3K signaling. PI3K, but not AKT, represent potential targets for melanoma therapy.

Expression of neddylation-related proteins in melanoma cell lines and the effect of neddylation on melanoma proliferation.

Neddylation promotes the process of ubiquitination, which plays a critical role in the degradation of numerous proteins, including cell cycle and apoptosis regulators. In our previous study, an increase in neddylation was identified in melanoma cell lines. In the present study, the upregulation of neddylation was detected in melanoma tissues which confirmed the results of our previous study on melanoma cell lines. To explore the mechanism by which the process of neddylation was increased, the enzymes that regulate the process were investigated. These neddylation-related regulatory enzymes are potential targets for melanoma therapy. Downregulation of UBA3, a subunit of the E1 enzyme, by RNA interference caused cell cycle arrest at G0/G1 in the M14 cell line. In addition, cyclin D expression declined, whereas p27, p21 and bax expression increased. These findings suggest that interfering with the neddylation pathway may decrease the proliferation of melanoma through the modulation of cell cycle regulators and apoptosis promoters.

Inhibition of the Prohormone Convertase Subtilisin-Kexin Isoenzyme-1 Induces Apoptosis in Human Melanoma Cells

Prohormone convertases (PCs) are endoproteases that process many substrates in addition to hormone precursors. Although overexpression of PCs is linked to carcinogenesis in some solid tumors, the role of subtilisin-kexin isoenzyme-1 (SKI-1) in this context is unknown. We show that SKI-1 is constitutively expressed in human pigment cells with higher SKI activity in seven out of eight melanoma cell lines compared with normal melanocytes. SKI-1 immunoreactivity is also detectable in tumor cells of melanoma metastases. Moreover, tissue samples of the latter display higher SKI-1 mRNA levels and activity than normal skin. From various stimuli tested, 12-O-tetradecanoylphorbol-13-acetate and tunicamycin affected SKI-1 expression. Importantly, SKI-1 inhibition by the cell-permeable enzyme inhibitor decanoyl-RRLL-chloromethylketone (dec-RRLL-CMK) not only suppressed proliferation and metabolic activity of melanoma cells in vitro but also reduced tumor growth of melanoma cells injected intracutaneously into immunodeficient mice. Mechanistic studies revealed that dec-RRLL-CMK induces classical apoptosis of melanoma cells in vitro and affects expression of several SKI-1 target genes including activating transcription factor 6 (ATF6). However, ATF6 gene silencing does not result in apoptosis of melanoma cells, suggesting that dec-RRLL-CMK induces cell death in an ATF6-independent manner. Our findings encourage further studies on SKI-1 as a potential target for melanoma therapy.

Abstract 431: Laminin-511 regulates melanoma cell function and tumor growth

Abstract Laminin family proteins are major non-collagenous components of basement membranes and have been found to be involved in modulating cell behavior. Laminin-511, composed of α5, β1, γ1 chains, is a major component of basement membrane of epithelia and blood vessels. Our lab has recently found increased expression of laminin-511 in malignant tumors. It has been found that tumor cells can synthesize and secrete laminin matrix to modify cellular environment and promote cell invasion. To explore the potential role of laminin-511 in melanoma, we blocked the expression of laminin-511 in human melanoma cell line SK-Mel-28 using RNA silencing strategy by transducing cells with lentiviral vector carrying laminin α5 chain specific shRNA (Lenti-Lα5 shRNA). Our data demonstrated that blocking the expression of laminin-511 significantly inhibited melanoma cell proliferation, attachment, migration and invasion in vitro, as well as tumor growth in vivo. In melanoma cells transduced with Lenti-Lα5 shRNA, compared with control melanoma cells, in cell proliferation analysis the total viable cells were 34.49% and 26.28% reduced on day 3 and day 5, respectively; in cell attachment assay the cell binding ability was decreased by 36.4%, 37.65% and 36.2% at 15, 30 and 60 minutes, respectively; in a chamber migration assay the cell migratory rate was dramatically down 90% at 24 hours; and in a Metrigel invasion assay the cell invasive capacity was markedly reduced by 89% at 24 hours. Furthermore, blocking laminin-511 expression significantly reduced tumor growth in vivo in nude mice. 18 tumors grew out of 20 injections with average volume 206 mm3 8 weeks post injection in cells tranduced with Lenti-Lα5 shRNA compared with 20 tumors out of 20 injections with average volume 590 mm3 in control cells. These findings revealed that laminin-511 plays important roles in melanoma cell function and tumor growth. In addition, our results strongly indicate laminin-511 a potential target for melanoma therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 431. doi:10.1158/1538-7445.AM2011-431

BMS-345541 Targets Inhibitor of κB Kinase and Induces Apoptosis in Melanoma: Involvement of Nuclear Factor κB and Mitochondria Pathways

Constitutive activation of inhibitor of kappaB kinase (IKK) confers melanoma resistance to apoptosis and chemotherapy. Whether IKK is able to serve as a therapeutic target in melanoma is unknown. We explored the possibility of exploiting IKK as a therapeutic target in melanoma by using BMS-345541, a novel compound with a highly selective IKKbeta inhibitory activity, to trigger melanoma cell apoptosis. Three human melanoma cell lines (SK-MEL-5, Hs 294T, and A375), all of which have high constitutive IKK activities, served as in vitro and in vivo melanoma models for treatment with BMS-345541. Two known antitumor drugs (temozolomide and bortezomib) were used as parallel controls for evaluation of the therapeutic efficiency and toxicity of BMS-345541. The effects of BMS-345541 on nuclear factor kappaB (NF-kappaB) signaling and on the apoptosis machinery were investigated. Inhibition of constitutive IKK activity by BMS-345541 resulted in the reduction of NF-kappaB activity, CXCL1 chemokine secretion by cultured melanoma cells and melanoma cell survival in vitro and in vivo. The effect of BMS-345541 on tumor cell growth was through mitochondria-mediated apoptosis, based on the release of apoptosis-inducing factor, dissipation of mitochondrial membrane potential, and reduced ratio of B cell lymphoma gene-2 (Bcl-2)/Bcl-associated X protein (Bax) in mitochondria. The BMS-345541 execution of apoptosis was apoptosis-inducing factor-dependent, but largely caspase-independent. BMS-345541 down-regulation of IKK activity results in mitochondria-mediated apoptosis of tumor cells because the programmed cell death machinery in melanoma cells is highly regulated by NF-kappaB signaling. Therefore, IKK may serve as a potential target for melanoma therapy.

Malignant melanoma.

The rapidly developing fields of melanoma research are revolutionizing the current concepts on melanoma etiology and pathogenesis and are introducing newer diagnostic techniques and potential therapeutic approaches. To present the most current concepts on the etiology and pathogenesis of melanoma and to introduce the recent diagnostic techniques and the potential therapeutic approaches. Data sources were reports on melanoma published in the English language literature and observations made using specimens available at Harvard University, Johns Hopkins Medical Center, Albany Medical College, Loyola University Medical Center, and University of Tennessee Health Science Center. Studies on melanoma containing chromosomal or genetic evaluation were selected for further analysis. Current clinical and pathologic categories with the reported genetic abnormalities were related to the latest information on pigment biology. The data extracted were used to develop a conceptual framework on the pathogenesis of melanoma; the generated model was then evaluated and used to suggest potential therapeutic approaches. (1) Melanoma is not genetically homogeneous, and the existing differences between the pathologic categories, particularly in areas such as type of growth phase (radial vs vertical growth), total vertical dimension, ulceration of primary tumor, and metastatic process, have profound prognostic and therapeutic implications. (2) Chromosomal aberrations and gene mutations are found in sporadic and familial melanomas; among the most important are those affecting the 9p21, which contains the p16 locus, a site known to be critical for normal progression of the cell cycle. Aberrant p16 expression is associated with more aggressive behavior. (3) Melanoma cells possess a remarkable repertoire of biosynthetic capacities represented by the production of hormones, growth factors, and their receptors that may sustain and accelerate tumor development and progression. For example, expression of the tumoral products alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone is regulated in vitro by ultraviolet light, a known carcinogen. (4) Melanomas differ from other tumors in their intrinsic capability to express melanogenic enzymes with the corresponding structural proteins to actually synthesize melanin. Melanogenesis-related proteins are rapidly entering the clinical arena, being used not only as diagnostic markers, but also as potential targets for melanoma therapy.

Malignant melanoma: An update

○ Context.-The rapidly developing fields of melanoma research are revolutionizing the current concepts on melanoma etiology and pathogenesis and are introducing newer diagnostic techniques and potential therapeutic approaches. Objectives.-To present the most current concepts on the etiology and pathogenesis of melanoma and to introduce the recent diagnostic techniques and the potential therapeutic approaches. Methods.-Data sources were reports on melanoma published in the English language literature and observations made using specimens available at Harvard University, Johns Hopkins Medical Center, Albany Medical College, Loyola University Medical Center, and University of Tennessee Health Science Center. Results.-Studies on melanoma containing chromosomal or genetic evaluation were selected for further analysis. Current clinical and pathologic categories with the reported genetic abnormalities were related to the latest information on pigment biology. The data extracted were used to develop a conceptual framework on the pathogenesis of melanoma; the generated model was then evaluated and used to suggest potential therapeutic approaches. Conclusions.-(1) Melanoma is not genetically homogenous, and the existing differences between the pathologic categories, particularly in areas such as type of growth phase (radial vs vertical growth), total vertical dimension, ulceration of primary tumor, and metastatic process, have profound prognostic and therapeutic implications. (2) Chromosomal aberrations and gene mutations are found in sporadic and familial melanomas; among the most important are those affecting the 9p21, which contains the p16 locus, a site known to be critical for normal progression of the cell cycle. Aberrant p16 expression is associated with more aggressive behavior. (3) Melanoma cells possess a remarkable repertoire of biosynthetic capacities represented by the production of hormones, growth factors, and their receptors that may sustain and accelerate tumor development and progression. For example, expression of the tumoral products α-melanocyte-stimulating hormone and adrenocorticotropic hormone is regulated in vitro by ultraviolet light, a known carcinogen. (4) Melanomas differ from other tumors in their intrinsic capability to express melanogenic enzymes with the corresponding structural proteins to actually synthesize melanin. Melanogenesis-related proteins are rapidly entering the clinical arena, being used not only as diagnostic markers, but also as potential targets for melanoma therapy.