Overexpression of the low molecular weight cyclin E in transgenic mice induces metastatic mammary carcinomas through the disruption of the ARF-p53 pathway

In tumor cells, cyclin E deregulation results in the appearance of five low molecular weight (LMW) isoforms. When overexpressed in breast cancer cells, these forms of cyclin E induce genomic instability, resistance to inhibition by p21 and p27, and resistance to antiestrogen therapy. Additionally, the LMW forms of cyclin E strongly correlate with decreased survival in patients with breast cancer. However, the oncologic role of the LMW forms of cyclin E in breast cancer tumorigenesis is yet to be determined. To this end, we generated transgenic mice expressing full-length cyclin E alone (M46A), full-length and the EL4 isoforms (EL1/EL4), or the EL2/3 isoforms of cyclin E (T1) under the control of the mouse mammary tumor virus promoter. Compared with full-length cyclin E, LMW cyclin E overexpression induces delayed mammary growth during the pubertal phase and abnormal cell morphology during lactation. Both primary mammary tumor formation and metastasis were markedly enhanced in LMW cyclin E transgenic mice. LMW cyclin E overexpression in mammary epithelial cells of mice is sufficient by itself to induce mammary adenocarcinomas in 34 of 124 (27%) animals compared with 7 of 67 (10.4%) mice expressing only the full-length cyclin E (P < 0.05). In addition, metastasis was seen in 25% of LMW cyclin E tumor-bearing animals compared with only 8.3% of tumors in the full-length cyclin E background (P < 0.05). Moreover, LMW cyclin E overexpression selects for inactivation of p53 by loss of heterozygosity and spontaneous and frequent inactivation of ARF. Therefore, LMW cyclin E overexpression strongly selects for spontaneous inactivation of the ARF-p53 pathway in vivo, canceling its protective checkpoint function and accelerating progression to malignancy.     

Cyclin E deregulation alters the biologic properties of ovarian cancer cells

We have previously shown that the low molecular weight (LMW) forms (trunk 1 and trunk 2) of cyclin E are biochemically hyperactive and induce G1/S progression in normal epithelial cells. Here we investigate the biologic consequences of LMW cyclin E expression in ovarian cancer cells. Using a panel of ovarian carcinoma tumors we find that cyclin E overexpression is invariably due to the presence of LMW forms and that expression of these forms appears to correlate with more advanced grade and stage of disease. Despite similar expression of p21 and p27, cyclin E overexpressing tumors have higher kinase function. Using an isogenic ovarian cancer model, we find that clones that overexpress the trunk 1 (T1) protein have a 10-fold increase in cyclin E kinase function, a 20% increase in S-phase fraction, a 10-15% decrease in doubling time and a 20% increase in colony formation compared to parental cells that express only the FL cyclin E protein. T1 clones were resistant to G1 arrest but more sensitive to cisplatin. Therefore, in ovarian tumors, the presence of LMW cyclin E forms confers altered biologic properties. Our data provides a potential mechanism for the poor prognosis of patients with LMW cyclin E expressing tumors.     

Cyclin E in breast tumors is cleaved into its low molecular weight forms by calpain

Abundant levels of the hyperactive low molecular weight (LMW) forms of cyclin E contribute to deregulation of Cdk2 in breast tumors, but the mechanism through which they arise is not fully understood. Here, we explored the hypothesis that post-translational processing by a protease generates the LMW forms of cyclin E in breast tumors. In ZR75 tumor cell lysates, calcium-induced cyclin E truncation into peptides corresponding in size with LMW forms of cyclin E in tumor tissues. Calpeptin inhibited calcium-stimulated cyclin E truncation, indicating that cleavage resulted from activity of the calcium-dependent protease, calpain. Consistently, calcium+calpain caused truncation of cyclin E immunoprecipitated from tumor cells and tissues. Calcium also caused truncation of the calpain regulatory subunit in tumor cell lysates, indicating that elevated calpain activity accompanies cyclin E truncation. Increased levels of the calpain small subunit were also observed in breast tumors, and significant amounts of its proteolyzed forms indicated increased calpain activity. While elastase also caused cyclin E truncation, the cleavage pattern was distinct from that generated by calpain, suggesting discrete mechanisms in regulating the formation of LMW cyclin E in breast tumors. Treatment of ZR75 cultures with calcium+A23187 recapitulated the formation of the calcium/calpain-induced LMW forms of cyclin E. Altered calcium homeostasis and/or inability of the endogenous calpain inhibitor to control the activity of high levels of the calpain small subunit may contribute to increased calpain activity in breast tumors, causing abundant levels of LMW cyclin E.     

Low-molecular weight forms of cyclin E differentiate ovarian carcinoma from cells of mesothelial origin and are associated with poor survival in ovarian carcinoma

BACKGROUND: The authors recently reported on the role of cyclin E in differentiating ovarian/primary peritoneal carcinoma from malignant peritoneal mesothelioma using gene expression arrays. In the current study, they analyzed the expression of low-molecular weight (LMW) forms of cyclin E in ovarian carcinoma, malignant mesothelioma, and benign reactive effusions. METHODS: Cyclin E protein expression was analyzed in 98 effusions (72 ovarian carcinomas, 14 malignant mesotheliomas, and 12 reactive specimens) using immunoblotting. Sixty-two ovarian carcinoma effusions were studied further for cyclin E expression using immunohistochemistry. The correlations between cyclin E expression in ovarian carcinoma and clinical parameters, including chemotherapy response, were analyzed. RESULTS: LMW forms of cyclin E were identified in 54 of 72 ovarian carcinoma effusions (75%) compared with 1 of 14 malignant mesothelioma effusions (7%) and 1 of 12 reactive effusions (8%) (P < .001). Their presence in ovarian carcinoma was associated with a higher percentage of cyclin E-positive cells (P = .001) and increased staining intensity (P < .001) using immunohistochemistry. The presence of LMW forms of cyclin E was correlated with shorter overall survival (P = .021) and progression-free survival (P = .020). The presence of a higher percentage of cyclin E-positive cells using immunohistochemistry was correlated with shorter progression-free survival (P = .026). No association with chemotherapy response was observed. CONCLUSIONS: LMW forms of cyclin E differentiated ovarian carcinoma from benign and malignant mesothelial cells and were associated with increased protein expression using immunohistochemistry. The expression of LMW cyclin E forms was not associated with chemotherapy response, although it may be a marker of aggressive disease in patients with metastatic ovarian carcinoma.     

Processing of cyclin E differs between normal and tumor breast cells

Cyclin E is a G1 cyclin essential for G1 to S-phase transition of the cell cycle with a profound role in oncogenesis. In tumor cells and tissues, cyclin E is overexpressed and present in its lower molecular weight (LMW) isoforms, and it can be used as a prognosticator for poor patient outcome. In this study, we have examined differences in the processing of cyclin E between normal mammary epithelial and breast cancer cell lines. Five NH2-terminally deleted epitope-tagged (FLAG) cyclin E vectors were constructed spanning the range of LMW forms observed in tumor cells. These constructs were transfected into normal and tumor cells and analyzed for the production of cyclin E-FLAG protein products by Western blot analysis with FLAG and cyclin E antibodies. Our results show that only tumor cells had the machinery to process these cyclin E-FLAG constructs to their LMW forms, whereas normal cells mainly expressed the full-length unprocessed form of each protein. Tumor and normal cells always process the cyclin E-FLAG protein in the same way as endogenously expressed cyclin E. This phenomenon is consistent with all of the cell lines used, regardless of transfection efficiency, time of processing posttransfection, or method of transfection. Furthermore, measurement of FLAG-associated kinase activity in the transfectants revealed that the protein products of the cyclin E-FLAG constructs are 10 times more active in tumor cells than in normal cells. These studies suggest that the LMW forms of cyclin E detected at a much higher level in tumor cells arise from posttranslational action of a protease.     

Specific Overexpression of Cyclin E·CDK2 in Early Preinvasive and Primary Breast Tumors in Female ACI Rats Induced by Estrogen

Overexpressed Aurora A, amplified centrosomes, and aneuploidy are salient features of estrogen-induced mammary preinvasive lesions and tumors in female August--Copenhagen Irish (ACI) rats. Intimately involved in these events are cyclins and their associated cyclin-dependent kinase (CDK) partners. Cyclin E1·CDK2 overexpression plays an important dual role in late G1/S phase of the cell cycle in cancer cells. It increases DNA replication providing growth advantage to cancer cells and facilitates aberrant centrosome duplication, generating chromosomal instability and aneuploidy leading to tumor development. Presented herein, a 24.0- and 45.0-fold elevation in cyclin E1 and CDK2 was found in 17β-estradiol (E(2))-induced ACI rat mammary tumors (MTs), respectively. Cyclin E·CDK2 positive staining was confined to the large round cells found within focal dysplasias, ductal carcinomas in situ, and invasive MTs. Co-immunoprecipitation and in vitro kinase activity of these tumors revealed that these cell cycle entities are functional. When mammary tissue derived from untreated normal, E(2)-induced hyperplasia and primary tumors were normalized to cyclin E1 levels, low molecular weight (LMW) cyclin E1 forms (33- and 45-kDa) were detected in all of these tissue groups. Moreover, increasing concentrations of protease inhibitor in tissue lysates resulted in a marked reduction of LMW forms, indicating that the presence of cyclin E1 LMW forms can be markedly reduced. Significant increases in cyclin E1 mRNA (2.1-fold) were detected in primary ACI rat E(2)-induced breast tumors, and quantitative real-time polymerase chain reaction revealed a 20% amplification of the cyclin E1 gene (CCNE1). Collectively, these results support the involvement of cyclin E1·CDK2 in centrosome overduplication during each stage of E(2)-induced mammary tumorigenesis.     

恶性黑色素瘤的黑色素含量与其进展和转移相关性探讨

  目的  探讨黑色素含量与细胞周期蛋白D1（cyclin D1）表达在恶性黑色素瘤中的临床病理意义。  方法  采用组织芯片和免疫组织化学（immunohistochemistry,IHC）方法,检测购于西安艾丽娜生物有限公司189例恶性黑色素瘤患者组织中的黑色素含量和cyclin D1表达。  结果  189例恶性黑色素瘤组织中的黑色素高含量者为76例（40.2%）,cyclin D1高表达者为80例（45.7%）。黑色素含量与患者的年龄、性别、肿瘤组织来源和有无淋巴结转移无关,与肿瘤的侵袭深度（P=0.001）和临床分期（P=0.038）有关。T3、T4期黑色素瘤中的黑色素含量明显低于T1、T2期。同时,临床分期Ⅲ、Ⅳ期皮肤恶性黑色素瘤中的黑色素含量也明显低于Ⅰ、Ⅱ期。cyclin D1表达与年龄、性别、侵袭深度、临床分期、有无淋巴结转移和肿瘤组织来源无关。黑色素含量和cyclin D1表达在58例淋巴结转移性恶性黑色素瘤中呈负相关（r=-0.271,P=0.039）。  结论  黑色素含量下调可能与恶性黑色素瘤的侵袭、进展和转移有关。为恶性黑色素瘤的预后因素分析和病理诊断提供新的依据。      

Tumor-specific low molecular weight forms of cyclin E induce genomic instability and resistance to p21, p27, and antiestrogens in breast cancer

The deregulated expression of cyclin E as measured by the overexpression of its low molecular weight (LMW) isoforms is a powerful predictor of poor outcome in patients with breast cancer. The mechanism by which these LMW forms give tumor cells a growth advantage is not known and is the subject of this article. In this article, we provide the pathobiological mechanisms of how these LMW forms are involved in disease progression. Specifically, we show that overexpression of the LMW forms of cyclin E but not the full-length form in MCF-7 results in (a) their hyperactivity because of increased affinity for cdk2 and resistance to inhibition by the cyclin-dependent kinase inhibitors p21 and p27, (b) resistance to the growth inhibiting effects of antiestrogens, and (c) chromosomal instability. Lastly, tumors from breast cancer patients overexpressing the LMW forms of cyclin E are polyploid in nature and are resistant to endocrine therapy. Collectively, the biochemical and functional differences between the full-length and the LMW isoforms of cyclin E provide a molecular mechanism for the poor clinical outcome observed in breast cancer patients harboring tumors expressing high levels of the LMW forms of cyclin E. These properties of the LMW forms cyclin E suggest that they are not just surrogate markers of poor outcome but bona fide mediators of aggressive disease and potential therapeutic targets for patients whose tumors overexpress these forms.     

Fully human antibodies to MCAM/MUC18 inhibit tumor growth and metastasis of human melanoma

MCAM/MUC18 expression correlates with tumor thickness and metastatic potential of human melanoma cells in nude mice. Moreover, ectopic expression of MUC18 in primary cutaneous melanoma cells leads to increased tumor growth and metastasis in vivo. Here we tested the effect of a fully human anti-MUC18 antibody, ABX-MA1, on angiogenesis, tumor growth, and metastasis. ABX-MA1 had no effect on melanoma cell proliferation rate in vitro. However, when cells of the metastatic melanoma lines A375SM and WM2664 (which express high levels of MUC18) were injected s.c. into nude mice and treated with ABX-MA1 (100 micro g, weekly, i.p. for 5 weeks), tumor growth was significantly inhibited compared with control IgG-treated mice. ABX-MA1 treatment also suppressed experimental lung metastasis of these melanoma cells. ABX-MA1 disrupted spheroid formation by melanoma cells expressing MUC18 (homotypic interaction) and the ability of these cells to attach to human vascular endothelial cells [HUVECs (MUC18 positive)] in vitro. ABX-MA1 treatment of melanoma cells in vitro significantly inhibited the promoter and collagenase activity of matrix metalloproteinase 2, resulting in decreased invasion through Matrigel-coated filters. Decreased expression of matrix metalloproteinase 2 was also observed in the implanted tumors in vivo. Moreover, because HUVECs also express MUC18, ABX-MA1 directly disrupted the tube-like formation by HUVECs in an in vitro vessel formation assay. Collectively, these results point to usefulness of ABX-MA1 as a modality to treat melanoma either alone or in combination with conventional chemotherapy or other antitumor agents.     

Tumor-specific hyperactive low-molecular-weight cyclin E isoforms detection and characterization in non-metastatic colorectal tumors

PURPOSE: Several molecules involved in cancer biology have been studied as potential prognostic markers. Recently, overexpression of cyclin E and its low-molecular-weight (LMW) isoforms has been reported to be the most prominent prognostic marker in breast cancer, surpassing proliferation index, ploidy, and axillary nodal involvement. Furthermore, cyclin E and p53 are considered the main factors controlling the euploid equilibrium in human cells. We investigated the status of cyclin E and p53 in cell lines and tissue samples of colorectal cancer, one of the leading causes of death from a tumor in the Western world. EXPERIMENTAL DESIGN: We analyzed colorectal cancer cells, from established cell lines and patient specimens, to determine the protein levels of cyclin E and p53, and to detect p53 and APC mutations, microsatellite and chromosome instability. In addition, we assessed the presence of cyclin E LMW isoforms and their enzymatic activity. RESULTS: Colorectal cancer cells expressed hyperactive LMW forms both in vitro and in vivo. These tumor-specific isoforms are correlated to genomic instability even in p53-proficient cells, and represented a constant feature in the tumors analyzed. CONCLUSIONS: In colorectal cancer, the formation of cyclin E LMW forms is an early event leading to DNA-damage checkpoint-independent proliferation. Collectively, our results provide evidence that evaluation of LMW forms could represent a novel tool in the molecular characterization of colorectal tumors aimed at identifying sensitive prognostic factors and uncovering subsets of high-risk patients within the traditional categories.     

Targeting melanoma growth and metastasis with systemic delivery of liposome-incorporated protease-activated receptor-1 small interfering RNA

The thrombin receptor [protease-activated receptor-1 (PAR-1)] is overexpressed in highly metastatic melanoma cell lines and in patients with metastatic lesions. Activation of PAR-1 leads to cell signaling and up-regulation of genes involved in adhesion, invasion, and angiogenesis. Herein, we stably silence PAR-1 through the use of lentiviral short hairpin RNA and found significant decreases in both tumor growth (P < 0.01) and metastasis (P < 0.001) of highly metastatic melanoma cell lines in vivo. The use of viruses for therapy is not ideal as it can induce toxic immune responses and possible gene alterations following viral integration. Therefore, we also used systemic delivery of PAR-1 small interfering RNA (siRNA) incorporated into neutral liposomes [1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC)] to decrease melanoma growth and metastasis in vivo. Significant decreases in tumor growth, weight, and metastatic lung colonies (P < 0.001 for all) were found in mice treated with PAR-1 siRNA-DOPC. The in vivo effects of PAR-1 on invasion and angiogenesis were analyzed via immunohistochemistry. Concomitant decreases in vascular endothelial growth factor, interleukin-8, and matrix metalloproteinase-2 expression levels, as well as decreased blood vessel density (CD31), were found in tumor samples from PAR-1 siRNA-treated mice, suggesting that PAR-1 is a regulator of melanoma cell growth and metastasis by affecting angiogenic and invasive factors. We propose that siRNA incorporated into DOPC nanoparticles could be delivered systemically and used as a new modality for melanoma treatment.     

Low-molecular-weight cyclin E: the missing link between biology and clinical outcome

Cyclin E, a key mediator of transition during the G₁/S cellular division phase, is deregulated in a wide variety of human cancers. Our group recently reported that overexpression and generation of low-molecular-weight (LMW) isoforms of cyclin E were associated with poor clinical outcome among breast cancer patients. However, the link between LMW cyclin E biology in mediating a tumorigenic phenotype and clinical outcome is unknown. To address this gap in knowledge, we assessed the role of LMW isoforms in breast cancer cells; we found that these forms of cyclin E induced genomic instability and resistance to p21, p27, and antiestrogens in breast cancer. These findings suggest that high levels of LMW isoforms of cyclin E not only can predict failure to endocrine therapy but also are true prognostic indicators because of their influence on cell proliferation and genetic instability.     

Identification of genes expressed in malignant cells that promote invasion

To systematically identify genes related to invasion a three-dimensional multicellular matrix invasion assay was used to classify human tumor cell lines as stromal invasion positive or stromal invasion negative. Cells from two of the primary cell types of the stromal compartment [endothelial cells (HMVEC) and myofibroblasts (HDF)] were assayed for invasion into tumor cell clusters (breast carcinoma, ovarian carcinoma, prostate carcinoma, lung carcinoma, and melanoma). Four tumor cell lines (MDA-MB231, SKOV-3, A375, and MEL624) scored invasion positive, and four tumor cell lines (LNCaP, DU145, PC3, and A549) scored invasion negative. Serial analysis of gene expression (SAGE) libraries generated from the tumor cell lines were analyzed by GeneSpring Hierarchical clustering, t test, and chi(2) test. Clusters emerged that reflected the behavior in the cell culture assay. Of the 47 most highly differentially expressed genes, 30 were selected for confirmation by real-time PCR, and 9 had good correlation with normalized serial analysis of gene expression tag counts. The strongest correlations were for bone marrow stromal antigen 2, stathmin-like 3, tumor necrosis factor receptor superfamily member 5, and hepatocyte growth factor tyrosine kinase substrate. In situ hybridization of metastatic and nonmetastatic ovarian cancer demonstrated selective expression of bone marrow stromal antigen 2 and tumor necrosis factor receptor superfamily member 5 in the metastatic disease. This combination approach appears to be a powerful tool for identifying genes that may be useful as diagnostic markers and/or as therapeutic targets for invasive solid tumors.     

RNA interference inhibition of matrix metalloproteinase-1 prevents melanoma metastasis by reducing tumor collagenase activity and angiogenesis

Melanoma incidence is increasing worldwide, and metastatic melanoma is almost completely resistant to every known therapy. New approaches to treating melanoma are urgently needed, and a greater understanding of the biology of melanoma invasion and metastasis will aid in their creation. A high proportion of invasive melanomas have a constitutively active Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) signaling cascade; however, the downstream effectors of ERK signaling that contribute to melanoma invasion and metastasis are unknown. ERK signaling drives the production of the interstitial collagenase matrix metalloproteinase-1 (MMP-1), which is expressed specifically by invasive melanomas. Using short hairpin RNAs (shRNA) to knock down MMP-1 expression in a human melanoma cell line, we investigated the role of MMP-1 in melanoma metastasis in a xenograft model. Knockdown of MMP-1 had no effect on primary tumor growth, but reduction of MMP-1 expression significantly decreased the ability of the melanoma to metastasize from the orthotopic site in the dermis to the lung. Mechanistically, tumor cells expressing MMP-1 shRNAs had diminished collagenase activity, which is required for tumor cell invasion. Additionally, attenuation of MMP-1 expression reduced angiogenesis. These results show, for the first time, that targeted inhibition of MMP-1, a single effector of the Raf/MEK/ERK signaling cascade, prevents the progression of melanoma from a primary to metastatic tumor and, as such, may represent a useful therapeutic tool in controlling this disease.     

HuR contributes to cyclin E1 deregulation in MCF-7 breast cancer cells

Many cancers overexpress cyclin E1 and its tumor-specific low molecular weight (LMW) isoforms. However, the mechanism of cyclin E1 deregulation in cancers is still not well understood. We show here that the mRNA-binding protein HuR increases cyclin E1 mRNA stability in MCF-7 breast carcinoma cells. Thus, mRNA stabilization may be a key event in the deregulation of cyclin E1 in MCF-7 cells. Compared with MCF10A immortalized breast epithelial cells, MCF-7 cells overexpress full-length cyclin E1 and its LMW isoforms and exhibit increased cyclin E1 mRNA stability. Increased mRNA stability is associated with a stable adenylation state and an increased ratio of cytoplasmic versus nuclear HuR. UV cross-link competition and UV cross-link immunoprecipitation assays verified that HuR specifically bound to the cyclin E1 3'-untranslated region. Knockdown of HuR with small interfering RNA (siRNA) in MCF-7 cells decreased cyclin E1 mRNA half-life (t(1/2)) and its protein level: a 22% decrease for the full-length isoforms and 80% decrease for the LMW isoforms. HuR siRNA also delayed G(1)-S phase transition and inhibited MCF-7 cell proliferation, which was partially recovered by overexpression of a LMW isoform of cyclin E1. Overexpression of HuR in MCF10A cells increased cyclin E1 mRNA t(1/2) and its protein level. Taken together, our data show that HuR critically contributes to cyclin E1 overexpression and its growth-promoting function, at least in part by increasing cyclin E1 mRNA stability, which provides a new mechanism of cyclin E1 deregulation in breast cancer.     

Higher levels of melanin and inhibition of cdk2 activity in primary human melanoma cells WM115 overexpressing nPKCdelta

Many studies have attempted to define the state of differentiation of melanoma cells and to correlate it with other critical parameters of malignancy such as the tumorigenic and metastatic nature of the cells. In the present paper we focused on the possible relationships between the novel protein kinase C isoform nPKCdelta, melanin synthesis and proliferative capacity in a primary human melanoma cell line WM115. Cells were transfected to produce overexpression of this isoform and the effects on melanin synthesis, cyclin-E dependent kinase (cdk2) activity and cyclin E expression were studied. It was shown that translocation of nPKCdelta into the nucleus affects melanin synthesis and inhibits cdk2 activity. As a compensatory effect, the level of cyclin E increases. In view of these results we suggest a model for the role of nPKCdelta in melanoma cells that may offer a new therapeutic perspective.     

Lupeol inhibits growth of highly aggressive human metastatic melanoma cells in vitro and in vivo by inducing apoptosis

PURPOSE: Poor prognosis of metastatic melanoma mandates the development of novel strategies for its treatment and prevention. In this study, the effect of lupeol, a diet-based triterpene, was determined on the growth and tumorigenicity of human melanoma cells in vitro and in vivo. EXPERIMENTAL DESIGN: Normal human melanocytes, and human metastatic (451Lu) and nonmetastatic (WM35) cells were treated with lupeol; its effect on growth, proliferation, and apoptosis were evaluated. Further athymic nude mice bearing 451Lu cell-originated tumors were administered with lupeol thrice a week, and its effect on tumor growth and surrogate biomarkers was evaluated. RESULTS: Lupeol significantly decreased the viability of 451Lu and WM35 melanoma cells but had only a marginal effect on normal human melanocyte cells at similar doses. Lupeol treatment of 451Lu cells caused (a) G(1)-S phase cell cycle arrest and apoptosis; (b) down-regulation of Bcl2 and up-regulation of Bax; (c) activation of caspase-3 and induction of poly(ADP)ribose polymerase cleavage; (d) decreased expression of cyclin D1, cyclin D2, and cdk2; and (e) increased expression of p21 protein. Next, lupeol significantly reduced 451Lu tumor growth in athymic nude mice and modulated the expression of proliferation markers, apoptotic markers, and cell cycle regulatory molecules in tumor xenografts. CONCLUSION: Our findings showed the anticancer efficacy of lupeol with mechanistic rationale against metastatic human melanoma cells. We suggest that lupeol, alone or as an adjuvant to current therapies, could be useful for the management of human melanoma.