mangostin and Melanoma

α-Mangostin (αM), a traditional natural product with promising application of treating a series of diseases, was limited use in clinical due to its hydrophobicity. Herein, MPEG-PCL nanomicelles were used to embed the αM for resolving hydrophobicity and improving the anti-melanoma effect of the αM. The anti-melanoma activity and potential mechanisms of biodegradable αM/MPEG-PCL nanomicelles were investigated. The αM/MPEG-PCL nanomicelles possessed a stronger effect on anti-melanoma compared to the free αM both in vitro and in vivo with a low cytotoxicity in non-tumor cell lines. In the research of mechanisms, the αM/MPEG-PCL nanomicelles inhibited the proliferation of melanoma cell, induced apoptosis via both apoptosis pathways of intrinsic and exogenous in vitro, as well as suppressed tumor growth and restrained angiogenesis in vivo, which implied that the αM/MPEG-PCL nanomicelles have potential application as a novel chemotherapeutic agent in melanoma therapy.

Topics: Animals; Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Cell Proliferation; Drug Delivery Systems; Human Umbilical Vein Endothelial Cells; Humans; Hydrophobic and Hydrophilic Interactions; Melanoma; Membrane Potential, Mitochondrial; Micelles; Nanoparticles; Polyesters; Polyethylene Glycols; Rats; Rats, Sprague-Dawley; Skin Neoplasms; Xanthones

α-Mangostin is a dietary xanthone that displays various biological activities, and numerous reports have shown its efficacy in cancer prevention and inhibition. As most agents have been shown to be ineffective as single-agent therapy for malignant melanoma (MM), the principle of targeted chemotherapy for MM is to use effective inhibitors and combination methods. In this study, we tested the cytotoxicity of several kinase inhibitors, including the glycogen synthase kinase (GSK)-3 inhibitor CHIR99021, and rapamycin, in combination with a dietary xanthone, α-mangostin, by screening from a kinase inhibitor library for melanogenesis in SK-MEL-2 MM cells, and verified these by clone formation efficiency, terminal dUTP nick end labelling, and expression of apoptosis-related proteins. We also explored the molecular mechanisms for the apoptosis-inducing effects reported. We found a marked synergistic effect of CHIR99021 or rapamycin in combination with α-mangostin, which we verified through apoptosis-related methods. These data provide a strong rationale for the use of α-mangostin as an adjunct to GSK-3 inhibitor or mammalian target of rapamycin inhibitor treatment. The intrinsic mechanism behind α-mangostin might be inhibition of phosphatidylinositol 3-kinase/AKT signalling and autophagy, and induction of reactive oxygen species generation.

Topics: Apoptosis; Autophagy; Cell Line, Tumor; Cell Proliferation; Cytotoxins; Drug Synergism; Drug Therapy, Combination; Glycogen Synthase Kinase 3; Humans; Melanoma; Melanoma, Cutaneous Malignant; Protein Kinase Inhibitors; Pyridines; Pyrimidines; Sirolimus; Skin Neoplasms; TOR Serine-Threonine Kinases; Xanthones

Melanogenesis is a key pathway for the regulation of skin pigmentation and the development of skin-lightening/skin-whitening drugs or cosmetics. In this study, we found that β-mangostin from seedcases of Garcinia mangostana inhibited α-melanocyte-stimulating hormone (α-MSH)-mediated melanogenesis in B16F10 melanoma cells and a three-dimensional human skin model. β-Mangostin significantly inhibited the protein level of tyrosinase induced by α-MSH in UPS (ubiquitin proteasome system)-independent and lysosome-dependent manner. The inhibition of autophagy by 3-methyladenine treatment or ATG5 knockdown effectively recovered premelanosome protein as well as tyrosinase degraded by the β-mangostin treatment. However, rapamycin, a representative non-selective autophagy inducer, triggered autophagy in α-MSH-stimulated cells, which was characterized by a considerable decrease in p62, but it was unable to inhibit melanogenesis. Melanosome-engulfing autophagosomes were observed using transmission electron microscopy. Furthermore, previously formed melanin could be degraded effectively in an autophagy-dependent manner in β-mangostin-treated cells. Taken together, our results suggest that β-mangostin inhibits the melanogenesis induced by α-MSH via an autophagy-dependent mechanism, and thus, the depigmentation effect of β-mangostin may depend on autophagy targeted at the melanosome rather than non-selective autophagy.

Topics: Adenine; alpha-MSH; Animals; Autophagy; Cell Survival; Garcinia mangostana; Humans; Inflammation; Melanins; Melanocytes; Melanoma; Melanoma, Experimental; Melanosomes; Mice; Microscopy, Electron, Transmission; Monophenol Monooxygenase; Pigmentation; Plant Extracts; Proteasome Endopeptidase Complex; Seeds; Skin; Skin Neoplasms; Ubiquitin; Xanthones

BACKGROUND The identification and use of novel compounds alone or in combination hold promise for the fight against NRAS mutant melanoma. MATERIAL AND METHODS We screened a kinase-specific inhibitor library through combining it with α-Mangostin in NRAS mutant melanoma cell line, and verified the enhancing effect of α-Mangostin through inhibition of the tumorigenesis pathway. RESULTS Within the kinase inhibitors, retinoic acid showed a significant synergistic effect with α-Mangostin. α-Mangostin also can reverse the drug resistance of retinoic acid in RARa siRNA-transduced sk-mel-2 cells. Colony assay, TUNEL staining, and the expressions of several apoptosis-related genes revealed that a-Mangostin enhanced the effect of retinoic acid-induced apoptosis. The combination treatment resulted in marked induction of ROS generation and inhibition of the AKT/S6 pathway. CONCLUSIONS These results indicate that the combination of these novel natural agents with retinoid acid may be clinically effective in NRAS mutant melanoma.

Topics: Apoptosis; Biological Products; Cell Line, Tumor; Down-Regulation; Gene Expression Regulation, Neoplastic; GTP Phosphohydrolases; Humans; Melanoma; Membrane Proteins; Mutation; Phosphorylation; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Reactive Oxygen Species; Reproducibility of Results; Signal Transduction; Tretinoin; Xanthones

α-Mangostin is a natural product commonly used in Asia for cosmetic and medicinal applications including topical treatment of acne and skin cancer. Towards finding new pharmacological strategies that overcome NRAS mutant melanoma, we performed a cell proliferation-based combination screen using a collection of well-characterized small molecule kinase inhibitors and α-Mangostin. We found that α-Mangostin significantly enhances Sorafenib pharmacological efficacy against an NRAS mutant melanoma cell line. The synergistic effects of α-Mangostin and Sorafenib were associated with enhanced inhibition of activated AKT and ERK, induced ER stress, and reduced autophagy, eventually leading to apoptosis. The structure of α-Mangostin resembles several inhibitors of the Retinoid X receptor (RXR). MITF expression, which is regulated by RXR, was modulated by α-Mangostin. Molecular docking revealed that α-Mangostin can be accommodated by the ligand binding pocket of RXR and may thereby compete with RXR-mediated control of MITF expression. In summary, these data demonstrate an unanticipated synergy between α-Mangostin and sorafenib, with mechanistic actions that convert a known safe natural product to a candidate combinatorial therapeutic agent.

Topics: Cell Line, Tumor; Cell Proliferation; Genes, ras; Humans; Melanoma; Niacinamide; Phenylurea Compounds; Receptors, Retinoic Acid; Sorafenib; Xanthones

We previously demonstrated that α-mangostin, γ-mangostin, and 8-deoxygartanin have significant cytotoxic effects on human melanoma SK-MEL-28 cell line. The current study revealed the underlying mechanisms. α-Mangostin (7.5  μg/mL) activated caspase activity, with a 3-fold and 4-fold increased caspase 8 and 9 activity, respectively. The molecular mechanisms were investigated by qRT-PCR for mRNA related to cell cycle arrest in G1 phase (p21(WAF1) and cyclin D1), apoptosis (cytochrome C, Bcl-2, and Bax), and survival pathways (Akt1, NFκB, and IκBα). α-Mangostin significantly upregulated mRNA expression of cytochrome C and p21(WAF1) and downregulated that of cyclin D1, Akt1, and NFκB. γ-Mangostin significantly downregulated mRNA expression of Akt1 and NFκB and upregulated p21(WAF1) and IκBα. 8-Deoxygartanin significantly upregulated the mRNA expression of p21(WAF1) and downregulated that of cyclin D1 and NFκB. The three xanthones significantly inhibited the mRNA expression of the BRAF V600E mutation. Moreover, α-mangostin and γ-mangostin significantly downregulated Akt phosphorylation at Ser473. In conclusion, the three xanthones induced an inhibitory effect on SK-MEL-28 cells by modulating the molecular targets involved in the apoptotic pathways.

Topics: Apoptosis; Caspase 8; Caspase 9; Cell Line, Tumor; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; G1 Phase Cell Cycle Checkpoints; Gene Expression Regulation, Neoplastic; Humans; I-kappa B Kinase; Melanoma; Phosphorylation; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; RNA, Messenger; RNA, Neoplasm; Up-Regulation; Xanthones

This study aimed at investigating the anti-invasive activities of α-mangostin on human melanoma SK-MEL-28 and squamous cell carcinoma A-431 cell lines.. Cytotoxicity was tested by the crystal violet assay; anti-invasive activity was detected by the wound healing, cell-matrix adhesion, and boyden chamber assays; and gene regulatory effects by qRT-PCR. Treatments were at non-toxic concentrations (0-1.25 μg/ml for A-431 cells and 0-2.5 μg/ml for SK-MEL-28 cells).. α-Mangostin inhibited motility, adhesion, migration and invasion. Invasive ability was reduced to 4% and 20% following α-mangostin treatment compared with untreated A-431 and SK-MEL-28 cells, respectively. Inhibition of gene expression of MMP-2, MMP-9, NF-κB, and Akt1 was involved in the anti-invasive activities on A-431 cells. Inhibition of MMP-2, NF-κB and IκBα was involved for SK-MEL-28 cells.. α-Mangostin suppressed the metastatic processes of SK-MEL-28 and A-431 cell lines by differentially regulating metastasis-related genes, showing potential as an anti-metastatic agent.

Topics: Carcinoma, Squamous Cell; Cell Adhesion; Cell Line, Tumor; Cell Movement; Garcinia mangostana; Gene Expression; Humans; Melanoma; Neoplasm Invasiveness; Neoplasm Metastasis; Plant Extracts; Skin Neoplasms; Xanthones

Mangosteen (Garcinia mangostana Linn.) is a tropical tree from South East Asia and its fruit pericarp is a well-known traditional medicine. In this study, the cytotoxic effect of three xanthone compounds (α-mangostin, γ-mangostin, and 8-deoxygartanin) from mangosteen pericarp was investigated using the human melanoma SK-MEL-28 cell line. Significant dose-dependent reduction in % cell viability was induced. γ-Mangostin and 8-deoxygartanine at 5 μg/ml increased the cell cycle arrest in G(1) phase (90% and 92%) compared with untreated cells (78%). All compounds induced apoptosis, of the highest being α-mangostin at 7.5 μg/ml that induced 59.6% early apoptosis, compared to 1.7% in untreated cells. The apoptotic effect of α-mangostin was via caspase activation and disruption of mitochondrial membrane pathways as evidenced by 25-fold increased caspase-3 activity and 9-fold decreased mitochondrial membrane potential when compared to untreated cells. In conclusion, these xanthones, especially α-mangostin, are potential candidates as anti-melanoma agents.

Topics: Antineoplastic Agents, Phytogenic; Caspase 3; Cell Line, Tumor; Dose-Response Relationship, Drug; Garcinia; Humans; Melanoma; Membrane Potentials; Mitochondria; Xanthones