Melanogenesis in uveal melanoma cells: Effect of argan oil

Exploring recent advances in signaling pathways and hallmarks of uveal melanoma: a comprehensive review

The purpose of this review was to provide a comprehensive review of the latest insights on the pathogenesis of uveal melanoma (UM) and its intracellular pathways. This article covers the epidemiology of UM, racial predispositions, cytogenetic and chromosomal alterations, gene mutations, key defective pathways, and their underlying mechanisms, as well as the application of hallmarks of cancer to UM. A key knowledge gap remains in identifying the most effective targeted therapy and determining the central pathway linking multiple signaling networks. UM is a malignant tumor arising from uveal melanocytes, predominantly affecting the choroid, with both genetic and epigenetic contributors. Key cytogenetic alterations include monosomy 3, chromosome 6p gain, chromosome 1p loss, and chromosome 8q gain. The most important UM-related signaling pathways are RAS/MAPK, PI3K/Akt/mTOR, Hippo-YAP, retinoblastoma (Rb), and p53 pathways. In the RAS/MAPK pathway, GNAQ/GNA11 mutations occur which account for more than 80% of UM cases. The PI3K/Akt/mTOR pathway promotes cyclin D1 overexpression and MDM2 upregulation, leading to p53 pathway inhibition. GNAQ/GNA11 mutations activate YAP via the Trio-RhoGTPase/RhoA/Rac1 signaling circuit in the Hippo-YAP pathway. Rb pathway dysregulation results from cyclin D1 overexpression or cyclin-dependent kinase inhibitor (CDKI) inactivation. In the p53 pathway, UM is characterized by p53 mutations, MDM2 overexpression, and Bcl-2 deregulation. Eventually, the ARF-MDM2 axis serves as a critical link between the RAS and p53 pathways. Hallmarks of cancer, such as evasion of growth suppression and self-sufficiency in growth signals, are also evident in UM. Genetic and epigenetic alterations, including NSB1, MDM2 and CCND1 amplification, and BAP1 mutations, play pivotal roles in UM pathobiology. Thus, UM exhibits a multifactorial pathology. By consolidating key mechanisms underlying UM pathogenesis, this review provides a comprehensive perspective on the involved pathways, offering insights that may facilitate the development of effective therapeutic strategies.

The ubiquitin-proteasome system in melanin metabolism

BACKGROUND

The ubiquitin-proteasome system (UPS) is a highly conserved way of regulating intracellular protein balance. UPS mediates proteolysis and disruption of variation or misfolding, while finely regulating proteins involved in differentiation and other biological processes.

AIMS

The aim of this review is to systematically introduce UPS as a key regulator of melanin metabolism.

METHODS

Systematic search and retrospective review were performed on the published data.

RESULTS

Melanocyte-inducing transcription factor (MITF) is a substrate of the ubiquitin ligase VCHL1 and acts as a transcription factor to regulate the expression of key enzymes in melanin synthesis such as tyrosinase (TYR). The rate-limiting enzyme TYR is modified by the ubiquitin ligase Hrd1 during melanosynthesis. Melanin itself is also regulated by multiple ubiquitin ligases including Fbp1 and Vhl. By regulating the ubiquitination modification to target each link of melanin synthesis, it plays an important role in correcting the disorder of melanin metabolism. A number of chemical agents have been proven to inhibit the activity of ubiquitin ligase.

CONCLUSIONS

Drugs targeting E3 ligase and deubiquitinating enzymes have great potential in the treatment of melanin metabolism disorders.

Argania Spinosa Fruit Shell Extract-Induced Melanogenesis via cAMP Signaling Pathway Activation

We have previously reported that argan oil and argan press-cake from the kernels of Argania spinosa have an anti-melanogenesis effect. Here, the effect of argan fruit shell ethanol extract (AFSEE) on melanogenesis in B16F10 cells was determined, and the mechanism underlying its effect was elucidated. The proliferation of AFSEE-treated B16F10 cells was evaluated using the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay, while the melanin content was quantified using a spectrophotometric method. The expression of melanogenesis-related proteins was determined by Western blot and real-time PCR, while global gene expression was determined using a DNA microarray. In vitro analysis results showed that the melanin content of B16F10 cells was significantly increased by AFSEE, without cytotoxicity, by increasing the melanogenic enzyme tyrosinase (TRY), tyrosinase related-protein 1 (TRP1), and dopachrome tautomerase (DCT) protein and mRNA expression, as well as upregulating microphthalmia-associated transcription factor (MITF) expression through mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase (ERK) and p38, and the cyclic adenosine monophosphate (cAMP) signaling pathway, as indicated by the microarray analysis results. AFSEE’s melanogenesis promotion effect is primarily attributed to its polyphenolic components. In conclusion, AFSEE promotes melanogenesis in B16F10 cells by upregulating the expression of the melanogenic enzymes through the cAMP–MITF signaling pathway.AFSEE may be used as a cosmetics product component to promote melanogenesis, or as a therapeutic against hypopigmentation disorders.