Molecular, Biological and Structural Features of VL CDR-1 Rb44 Peptide, Which Targets the Microtubule Network in Melanoma Cells.

Microtubules are important drug targets in tumor cells, owing to their role in supporting and determining the cell shape, organelle movement and cell division. The complementarity-determining regions (CDRs) of immunoglobulins have been reported to be a source of anti-tumor peptide sequences, independently of the original antibody specificity for a given antigen. We found that, the anti-Lewis B mAb light-chain CDR1 synthetic peptide Rb44, interacted with microtubules and induced depolymerization, with subsequent degradation of actin filaments, leading to depolarization of mitochondrial membrane-potential, increase of ROS, cell cycle arrest at G2/M, cleavage of caspase-9, caspase-3 and PARP, upregulation of Bax and downregulation of Bcl-2, altogether resulting in intrinsic apoptosis of melanoma cells. The in vitro inhibition of angiogenesis was also an Rb44 effect. Peritumoral injection of Rb44L1 delayed growth of subcutaneously grafted melanoma cells in a syngeneic mouse model. L1-CDRs from immunoglobulins and their interactions with tubulin-dimers were explored to interpret effects on microtubule stability. The opening motion of tubulin monomers allowed for efficient L1-CDR docking, impairment of dimer formation and microtubule dissociation. We conclude that Rb44 VL-CDR1 is a novel peptide that acts on melanoma microtubule network causing cell apoptosis in vitro and melanoma growth inhibition in vivo.

Immunomodulatory Protective Effects of Rb9 Cyclic-Peptide in a Metastatic Melanoma Setting and the Involvement of Dendritic Cells.

The cyclic VHCDR3-derived peptide (Rb9) from RebMab200 antibody, directed to a NaPi2B phosphate-transport protein, displayed anti-metastatic melanoma activity at 50-300 µg intraperitoneally injected in syngeneic mice. Immune deficient mice failed to respond to the peptide protective effect. Rb9 induced increased CD8+ T and low Foxp3+ T cell infiltration in lung metastases and high IFN-γ and low TGF-ß in lymphoid organs. The peptide co-localized with F-actin and a nuclear site in dendritic cells and specifically bound to MIF and CD74 in a dot-blot setting. Murine bone-marrow dendritic cells preincubated with Rb9 for 6 h were treated with MIF for short time periods. The modulated responses showed stimulation of CD74 and inhibition of pPI3K, pERK, and pNF-κB as compared to MIF alone. Rb9 in a melanoma-conditioned medium, stimulated the M1 type conversion in bone marrow-macrophages. Functional aspects of Rb9 in vivo were studied in therapeutic and prophylactic protocols using a melanoma metastatic model. In both protocols Rb9 exhibited a marked anti-melanoma protection. Human dendritic cells were also investigated showing increased expression of surface markers in response to Rb9 incubation. Rb9 either stimulated or slightly inhibited moDCs submitted to inhibitory (TGF-ß and IL-10) or activating (LPS) conditions, respectively. Lymphocyte proliferation was obtained with moDCs stimulated by Rb9 and tumor cell lysate. In moDCs from cancer patients Rb9 exerted immunomodulatory activities depending on their functional status. The peptide may inhibit over-stimulated cells, stimulate poorly activated and suppressed cells, or cause instead, little phenotypic and functional alterations. Recently, the interaction MIF-CD74 has been associated to PD-L1 expression and IFN-γ, suggesting a target for melanoma treatment. The effects described for Rb9 and the protection against metastatic melanoma may suggest the possibility of a peptide reagent that could be relevant when associated to modern immunotherapeutic procedures.

Understanding the cytotoxic effects of new isovanillin derivatives through phospholipid Langmuir monolayers.

Twenty-one isovanillin derivatives were prepared in order to evaluate their cytotoxic properties against the cancer cell lines B16F10-Nex2, HL-60, MCF-7, A2058 and HeLa. Among them, seven derivatives exhibited cytotoxic activity. We observed that for obtaining smaller IC50 values and for increasing the index of selectivity, two structural features are very important when compared with isovanillin (1); a hydroxymethyl group at C-1 and the replacement of the hydroxyl group at C-3 by different alkyl groups. As the lipophilicity of the compounds was changed, we decided to investigate the interaction of the cytotoxic isovallinin derivatives on cell membrane models through Langmuir monolayers by employing the lipids DPPC (1,2-diplamitoyl-sn-glycero-3-phosphocoline) and DPPS (1,2-diplamitoyl-sn-glycero-3-phosphoserine). The structural changes on the scaffold of the compounds modulated the interaction with the phospholipids at the air-water interface. These results were very important to understand the biophysical aspects related to the interaction of the cytotoxic compounds with the cancer cell membranes.

Blockade of MIF-CD74 Signalling on Macrophages and Dendritic Cells Restores the Antitumour Immune Response Against Metastatic Melanoma.

Mounting an effective immune response against cancer requires the activation of innate and adaptive immune cells. Metastatic melanoma is the most aggressive form of skin cancer. While immunotherapies have shown a remarkable success in melanoma treatment, patients develop resistance by mechanisms that include the establishment of an immune suppressive tumor microenvironment. Thus, understanding how metastatic melanoma cells suppress the immune system is vital to develop effective immunotherapies against this disease. In this study, we find that macrophages (MOs) and dendritic cells (DCs) are suppressed in metastatic melanoma and that the Ig-CDR-based peptide C36L1 is able to restore MOs and DCs' antitumorigenic and immunogenic functions and to inhibit metastatic growth in lungs. Specifically, C36L1 treatment is able to repolarize M2-like immunosuppressive MOs into M1-like antitumorigenic MOs, and increase the number of immunogenic DCs, and activated cytotoxic T cells, while reducing the number of regulatory T cells and monocytic myeloid-derived suppressor cells in metastatic lungs. Mechanistically, we find that C36L1 directly binds to the MIF receptor CD74 which is expressed on MOs and DCs, disturbing CD74 structural dynamics and inhibiting MIF signaling on these cells. Interfering with MIF-CD74 signaling on MOs and DCs leads to a decrease in the expression of immunosuppressive factors from MOs and an increase in the capacity of DCs to activate cytotoxic T cells. Our findings suggest that interfering with MIF-CD74 immunosuppressive signaling in MOs and DCs, using peptide-based immunotherapy can restore the antitumor immune response in metastatic melanoma. Our study provides the rationale for further development of peptide-based therapies to restore the antitumor immune response in metastatic melanoma.

Circadian variation and in vitro cytotoxic activity evaluation of volatile compounds from leaves of Piper regnellii (Miq) C. DC. var. regnellii (C. DC.) Yunck (Piperaceae).

Aiming detection of circadian variation in the chemical composition of volatiles from Piper regnellii, the leaves were collected during four different periods (8, 12, 16 and 20 h) in the same day. After extraction by hydrodistillation and GC/MS analysis, no significant variation was observed for the main compounds: germacrene D (45.6 ± 1.5-51.4 ± 3.1%), α-chamigrene (8.9 ± 1.3-11.3 ± 2.7%) and ß-caryophyllene (8.2 ± 0.9-9.5 ± 0.3%). Evaluation of in vitro cytotoxicity against several cancer and non-tumourigenic cells indicated promising activity, especially to HeLa (human cervical carcinoma) with IC50 ranging from 11 ± 3 to 17 ± 3 µg/mL. The obtained volatile oils were pooled and subjected to fractionation to afford pure ß-caryophyllene, α-chamigrene and germacrene D, being this last compound the more active against HeLa cells with IC50 of 7 ± 1 µg/mL (34 ± 5 µM). Therefore, the predominance of germacrene D in all analysed oils could justify, at least in part, the activity observed for the volatile compounds from P. regnellii leaves.

Neolignans isolated from Nectandra leucantha induce apoptosis in melanoma cells by disturbance in mitochondrial integrity and redox homeostasis.

Six neolignans including three previously undescribed metabolites: 1-[(7R)-hydroxy-8-propenyl]-3-[3'-methoxy-1'-(8'-propenyl)-phenoxy]-4,5-dimethoxybenzene, 4-hydroxy-5-methoxy-3-[3'-methoxy-1'-(8'-propenyl)phenoxy]-1-(7-oxo-8-propenyl)benzene and 4,5-dimethoxy-3-[3'-methoxy-1'-(8'-propenyl)phenoxy]-1-(7-oxo-8-propenyl)benzene were isolated from twigs of Nectandra leucantha Nees & Mart (Lauraceae) using bioactivity-guided fractionation. Cytotoxic activity of isolated compounds was evaluated in vitro against cancer cell lines (SK BR-3, HCT, U87-MG, A2058, and B16F10), being dehydrodieugenol B and 4-hydroxy-5-methoxy-3-[3'-methoxy-1'-(8'-propenyl)phenoxy]-1-(7-oxo-8-propenyl)benzene the most active metabolites. These compounds displayed IC50 values of 78.8 ± 2.8 and 82.2 ± 3.5 µM, respectively, against murine melanoma. Different in vitro mechanism of induced cytotoxicity for this cell line is proposed for both compounds. Obtained results indicated a remarkable effect during the induction of morphological, biochemical and enzymatic features of apoptosis, such as disruption of mitochondrial membrane potential (ΔΨm), exposure of phosphatidylserine in the outer cell membrane, and genomic DNA condensation and fragmentation. Dehydrodieugenol B induced caspase-3 and PARP activation and 4-hydroxy-5-methoxy-3-[3'-methoxy-1'-(8'-propenyl)phenoxy]-1-(7-oxo-8-propenyl)benzene downregulated the levels of Bcl-2 protein. These effects were accompanied by increased levels of reactive oxygen species as a consequence of mitochondrial damage, followed by F-actin aggregation during the cell death process. Dehydrodieugenol B showed oxidative properties and both compounds, especially 4-hydroxy-5-methoxy-3-[3'-methoxy-1'-(8'-propenyl)phenoxy]-1-(7-oxo-8-propenyl)benzene, displayed potential to alkylate nucleophiles, suggesting an accessory mechanism of tumor-induced cytotoxicity by these metabolites.

Terpenoids from Leaves of Guarea macrophylla Display In Vitro Cytotoxic Activity and Induce Apoptosis In Melanoma Cells.

Guarea macrophylla is a Brazilian plant species that has been used in folk medicine to treat a range of diseases. Our ongoing work focuses on the discovery of new bioactive natural products derived from Brazilian flora. The current study describes the identification of cytotoxic compounds from the EtOH extract of leaves from G. macrophylla using bioactivity-guided fractionation. This approach resulted in the isolation and characterization of four compounds: cycloart-23E-ene-3ß,25-diol (1), (23S*,24S*)-dihydroxycicloart-25-en-3-one (2), isopimara-7,15-diene-2α,3ß-diol (3), and isopimara-7,15-dien-3ß-ol (4), in which 2 and 3 are identified as new derivatives. In vitro assays were conducted to evaluate the cytotoxic activity of compounds 1-4 against a panel of cancer cell lines and to determine the possible mechanism(s) related to the activity of the compounds on B16F10Nex2 cells. The most active compound 1 induced cytotoxic effects on tumor cells, with IC50 values of 18.3, 52.1, and 58.9 µM against HL-60, HeLa, and B16F10-Nex2 tumor cells, respectively. Furthermore, it was observed in melanoma cells that compound 1 induced several specific apoptotic hallmarks, such as morphological changes in the cell shape structure, nuclear DNA condensation, specific chromatin fragmentation, and disruption in the mitochondrial membrane potential, which are related to the intrinsic apoptotic pathway.

AC-1001 H3 CDR peptide induces apoptosis and signs of autophagy in vitro and exhibits antimetastatic activity in a syngeneic melanoma model.

Antibody-derived peptides modulate functions of the immune system and are a source of anti-infective and antitumor substances. Recent studies have shown that they comprise amino acid sequences of immunoglobulin complementarity-determining regions, but also fragments of constant regions. VH CDR3 of murine mAb AC-1001 displays antimetastatic activities using B16F10-Nex2 murine melanoma cells in a syngeneic model. The peptide was cytotoxic in vitro in murine and human melanoma cells inducing reactive oxygen species (ROS) and apoptosis by the intrinsic pathway. Signs of autophagy were also suggested by the increased expression of LC3/LC3II and Beclin 1 and by ultrastructural evidence. AC-1001 H3 bound to both G- and F-actin and inhibited tumor cell migration. These results are important evidence of the antitumor activity of Ig CDR-derived peptides.

The Ig VH complementarity-determining region 3-containing Rb9 peptide, inhibits melanoma cells migration and invasion by interactions with Hsp90 and an adhesion G-protein coupled receptor.

The present work aims at investigating the mechanism of action of the Rb9 peptide, which contains the VHCDR 3 sequence of anti-sodium-dependent phosphate transport protein 2B (NaPi2B) monoclonal antibody RebMab200 and displayed antitumor properties. Short peptides corresponding to the hypervariable complementarity-determining regions (CDRs) of immunoglobulins have been associated with antimicrobial, antiviral, immunomodulatory and antitumor activities regardless of the specificity of the antibody. We have shown that the CDR derived peptide Rb9 induced substrate hyperadherence, inhibition of cell migration and matrix invasion in melanoma and other tumor cell lines. Rb9 also inhibited metastasis of murine melanoma in a syngeneic mouse model. We found that Rb9 binds to and interferes with Hsp90 chaperone activity causing attenuation of FAK-Src signaling and downregulation of active Rac1 in B16F10-Nex2 melanoma cells. The peptide also bound to an adhesion G-protein coupled receptor, triggering a concentration-dependent synthesis of cAMP and activation of PKA and VASP signaling as well as IP-3 dependent Ca2+ release. Hsp90 is highly expressed on the cell surface of melanoma cells, and synthetic agents that target Hsp90 are promising cancer therapeutic drugs. Based on their remarkable antitumor effects, the CDR-H3-derived peptides from RebMab200, and particularly the highly soluble and stable Rb9, are novel candidates to be further studied as potential antitumor drugs, selectively acting on cancer cell motility and invasion.

Camphene isolated from essential oil of Piper cernuum (Piperaceae) induces intrinsic apoptosis in melanoma cells and displays antitumor activity in vivo.

Natural monoterpenes were isolated from the essential oil of Piper cernuum Vell. (Piperaceae) leaves. The crude oil and the individual monoterpenes were tested for cytotoxicity in human tumor cell lineages and B16F10-Nex2 murine melanoma cells. In the present work we demonstrate the activity of camphene against different cancer cells, with its mechanism of action being investigated in vitro and in vivo in murine melanoma. Camphene induced apoptosis by the intrinsic pathway in melanoma cells mainly by causing endoplasmic reticulum (ER) stress, with release of Ca(2+) together with HmgB1 and calreticulin, loss of mitochondrial membrane potential and up regulation of caspase-3 activity. Importantly, camphene exerted antitumor activity in vivo by inhibiting subcutaneous tumor growth of highly aggressive melanoma cells in a syngeneic model, suggesting a promising role of this compound in cancer therapy.

A novel microtubule de-stabilizing complementarity-determining region C36L1 peptide displays antitumor activity against melanoma in vitro and in vivo.

Short peptide sequences from complementarity-determining regions (CDRs) of different immunoglobulins may exert anti-infective, immunomodulatory and antitumor activities regardless of the specificity of the original monoclonal antibody (mAb). In this sense, they resemble early molecules of innate immunity. C36L1 was identified as a bioactive light-chain CDR1 peptide by screening 19 conserved CDR sequences targeting murine B16F10-Nex2 melanoma. The 17-amino acid peptide is readily taken up by melanoma cells and acts on microtubules causing depolymerization, stress of the endoplasmic reticulum and intrinsic apoptosis. At low concentrations, C36L1 inhibited migration, invasion and proliferation of B16F10-Nex2 cells with cell cycle arrest at G2/M phase, by regulating the PI3K/Akt signaling axis involving Rho-GTPase and PTEN mediation. Peritumor injection of the peptide delayed growth of subcutaneously grafted melanoma cells. Intraperitoneal administration of C36L1 induced a significant immune-response dependent anti-tumor protection in a syngeneic metastatic melanoma model. Dendritic cells stimulated ex-vivo by the peptide and transferred to animals challenged with tumor cells were equally effective. The C36 VL CDR1 peptide is a promising microtubule-interacting drug that induces tumor cell death by apoptosis and inhibits metastases of highly aggressive melanoma cells.

Chemical composition and in vitro cytotoxic effects of the essential oil from Nectandra leucantha leaves.

CONTEXT: Nectandra (Lauraceae) species have been used in folk medicine as an antidiarrheal, analgesic, antifungal, etc., and have many pharmacological proprieties. OBJECTIVE: Investigation of the chemical composition and cytotoxicity of essential oil from Nectandra leucantha Nees & Mart. leaves. This is the first study involving N. leucantha reported in the literature. MATERIAL AND METHODS: The essential oil of N. leucantha leaves was obtained by hydrodistillation. Its chemical composition was determined using a combination of GC/FID, GC/MS, and determination of Kovats index (KI). In vitro cytotoxic activity was evaluated against six cancer cell lines - murine melanoma (B16F10-Nex2), human glioblastome (U-87), human cervical carcinoma (HeLa), human colon carcinoma (HCT), human breast adenocarcinoma (MCF7), and human cervical tumor (Siha) as well as against one non-tumorigenic cell line - human foreskin fibroblast (HFF). RESULTS: Thirty-three compounds were identified primarily sesquiterpenes (81.41%), the main compounds being bicyclogermacrene (28.44%), germacrene A (7.34%), spathulenol (5.82%), and globulol (5.25%). Furthermore, monoterpenes were also found in the analyzed oil (12.84%), predominantly α- and ß-pinenes (6.59 and 4.57%, respectively). The crude essential oil displayed significant cytotoxic activity against B16F10-Nex2 (IC50 33 ± 1 µg/mL) and U87 (IC50 75.95 ± 0.03 µg/mL) and HeLa (IC50 60 ± 12 µg/mL) cell lines. The main identified compound, bicyclogermacrene, displayed IC50 ranging from 3.1 ± 0.2 to 21 ± 6 µg/mL. DISCUSSION AND CONCLUSION: The results indicate that the crude oils from leaves of N. leucantha displayed cytotoxic activity being bicyclogermacrene, the main compound identified in the crude oil responsible, at least in part, for this potential.

Mastoparan induces apoptosis in B16F10-Nex2 melanoma cells via the intrinsic mitochondrial pathway and displays antitumor activity in vivo.

Mastoparan is an α-helical and amphipathic tetradecapeptide obtained from the venom of the wasp Vespula lewisii. This peptide exhibits a wide variety of biological effects, including antimicrobial activity, increased histamine release from mast cells, induction of a potent mitochondrial permeability transition and tumor cell cytotoxicity. Here, the effects of mastoparan in malignant melanoma were studied using the murine model of B16F10-Nex2 cells. In vitro, mastoparan caused melanoma cell death by the mitochondrial apoptosis pathway, as evidenced by the Annexin V-FITC/PI assay, loss of mitochondrial membrane potential (ΔΨm), generation of reactive oxygen species, DNA degradation and cell death signaling. Most importantly, mastoparan reduced the growth of subcutaneous melanoma in syngeneic mice and increased their survival. The present results show that mastoparan induced caspase-dependent apoptosis in melanoma cells through the intrinsic mitochondrial pathway protecting the mice against tumor development.

Antitumor activity of kielmeyera coriacea leaf constituents in experimental melanoma, tested in vitro and in vivo in syngeneic mice.

PURPOSE: The antitumor activity of Kielmeyera coriacea (Clusiaceae), a medicinal plant used in the treatment of parasitic, as well as fungal and bacterial infections by the Brazilian Cerrado population, was investigated. METHODS: A chloroform extract (CE) of K. coriacea was tested in the murine melanoma cell line (B16F10-Nex2) and a panel of human tumor cell lines. Tumor cell migration was determined by the wound-healing assay and the in vivo antitumor activity of CE was investigated in a melanoma cell metastatic model. 1H NMR and GC/MS were used to determine CE chemical composition. RESULTS: We found that CE exhibited strong cytotoxic activity against murine melanoma cells and a panel of human tumor cell lines in vitro. CE also inhibited growth of B16F10-Nex2 cells at sub lethal concentrations, inducing cell cycle arrest at S phase, and inhibition of tumor cell migration. Most importantly, administration of CE significantly reduced the number of melanoma metastatic nodules in vivo. Chemical analysis of CE indicated the presence of the long chain fatty compounds, 1-eicosanol, 1-docosanol, and 2-nonadecanone as main constituents. CONCLUSION: These results indicate that K. coriacea is a promising medicinal plant in cancer therapy exhibiting antitumor activity both in vitro and in vivo against different tumor cell lines.

A subtraction tolerization method of immunization allowed for Wilms' tumor protein-1 (WT1) identification in melanoma and discovery of an antitumor peptide sequence.

On searching for melanoma transcription factors in a project focusing on internal antitumor peptide sequences from transcription factors, we found that a highly immunogenic component emerged upon using a subtraction tolerization method of immunization. While several conventional immunization procedures using whole melanoma cells induced a plethora of low affinity antibodies of various specificities, the subtraction tolerization method efficiently elicited mono-specific antibodies that recognized Wilms' tumor protein 1 (WT1), which is known as an important marker in melanoma prognosis and treatment. For the tolerization step, pre-immunization of Balb/c mice with a membrane-rich preparation of glioblastoma U87 cells was used. The subsequent immunizations with SK-MEL-28 melanoma cells elicited antibodies strongly reacting with 50 and 55 kDa proteins, identified as WT1. Remarkably, this was the only component strongly reactive with these antibodies in a melanoma cell lysate. WT1 was then chosen as a target for selecting internally bioactive peptides. A hydrophilic Trojan peptide containing most of the zinc finger-2 domain of WT1 was synthesized and shown to inhibit SK-MEL-28 melanoma growth in vitro. The peptide WT1-pTj was also protective in vivo in a metastatic melanoma model and peptide-stimulated syngeneic dendritic cells reproduced the anti-melanoma effect of the unprotected peptide. Identification of antitumor peptides derived from major transcription factors represents a new tool to be explored in cancer research aiming at new therapeutic drugs.

Pyrostegia venusta heptane extract containing saturated aliphatic hydrocarbons induces apoptosis on B16F10-Nex2 melanoma cells and displays antitumor activity in vivo.

BACKGROUND: Pyrostegia venusta (Ker. Gawl.) Miers (Bignoniacea) is a medicinal plant from the Brazilian Cerrado used to treat leucoderma and common diseases of the respiratory system. OBJECTIVE: To investigate the antitumor activity of P.venusta extracts against melanoma. MATERIALS AND METHODS: The cytotoxic activity and tumor induced cell death of heptane extract (HE) from P. venusta flowers was evaluated against murine melanoma B16F10-Nex2 cells in vitro and in a syngeneic model in vivo. RESULTS: We found that HE induced apoptosis in melanoma cells by disruption of the mitochondrial membrane potential, induction of reactive oxygen species and late apoptosis evidenced by plasma membrane blebbing, cell shrinkage, chromatin condensation and DNA fragmentation, exposure of phosphatidylserine on the cell surface and activation of caspase-2,-3,-8,-9. HE was also protective against singeneyc subcutaneous melanoma HE compounds were also able to induce cell cycle arrest at G2/M phases on tumor cells. On fractionation of HE in silica gel we isolated a cytotoxic fraction that contained a mixture of saturated hydrocarbons identified by (1)H NMR and GC-MS analyses. Predominant species were octacosane (C28H58-36%) and triacontane (C30H62-13%), which individually showed significant cytotoxic activity against murine melanoma B16F10-Nex2 cells in vitro and a very promising antitumor protection against subcutaneous melanoma in vivo. CONCLUSION: The results suggest that the components of the heptane extract, mainly octasane and triacontane, which showed antitumor properties in experimental melanoma upon regional administration, might also be therapeutic in human cancer, such as in the mostly epidermal and slowly invasive melanomas, such as acral lentiginous melanoma, as an adjuvant treatment to surgical excision.

A novel cell-penetrating peptide derived from WT1 enhances p53 activity, induces cell senescence and displays antimelanoma activity in xeno- and syngeneic systems.

The Wilms tumor protein 1 (WT1) transcription factor has been associated in malignant melanoma with cell survival and metastasis, thus emerging as a candidate for targeted therapy. A lysine-arginine rich peptide, WT1-pTj, derived from the ZF domain of WT1 was evaluated as an antitumor agent against A2058 human melanoma cells and B16F10-Nex2 syngeneic murine melanoma. Peptide WT1-pTj quickly penetrated human melanoma cells and induced senescence, recognized by increased SA-ß-galactosidase activity, enhanced transcriptional activity of p53, and induction of the cell cycle inhibitors p21 and p27. Moreover, the peptide bound to p53 and competed with WT1 protein for binding to p53. WT1-pTj treatment led to sustained cell growth suppression, abrogation of clonogenicity and G2/M cell cycle arrest. Notably, in vivo studies showed that WT1-pTj inhibited both the metastases and subcutaneous growth of murine melanoma in syngeneic mice, and prolonged the survival of nude mice challenged with human melanoma cells. The 27-amino acid cell-penetrating WT1-derived peptide, depends on C(3) and H(16) for effective antimelanoma activity, inhibits proliferation of WT1-expressing human tumor cell lines, and may have an effective role in the treatment of WT1-expressing malignancies.

Jacaranone induces apoptosis in melanoma cells via ROS-mediated downregulation of Akt and p38 MAPK activation and displays antitumor activity in vivo.

BACKGROUND: Malignant melanoma is a deadly type of metastatic skin cancer with increased incidence over the past 30 years. Despite the advanced knowledge on the biology, immunobiology and molecular genetics of melanoma, the alternatives of treatment are limited with poor prognosis. On clinical trials, natural products and among them redox-active quinones have been tested in the attempt to control the growth of cancer cells. Recently, we isolated jacaranone from Pentacalia desiderabilis, a benzoquinone derivative that showed a broad antitumor activity and protective anti-melanoma effect in a syngeneic model. The purified substance is active at micromolar concentrations, is not hemolytic, and is not toxic in naïve mice. METHODOLOGY/PRINCIPAL FINDINGS: The jacaranone antitumor activity was shown against several human cancer cell lines in vitro. Moreover, the induction of apoptosis in murine melanoma cells and jacaranone antitumor activity in vivo, in a melanoma experimental model, were also shown. Jacaranone renders antiproliferative and proapoptotic responses in tumor cells, by acting on Akt and p38 MAPK signaling pathways through generation of reactive oxygen species (ROS). The free radical scavenger N-acetyl-cysteine (NAC) was able to completely suppress cell death induced by jacaranone as it blocked Akt downregulation, p38 MAPK activation as well as upregulation of proapoptotic Bax. Notably, treatment of melanoma growing subcutaneously in mice with jacaranone significantly extended the mean survival times in a dose-dependent manner. CONCLUSIONS/SIGNIFICANCE: The results provide evidence for the mechanisms of action of jacaranone and emphasize the potential use of this quinone for the treatment of melanoma.