In a recent study published by Nature Communications, researchers uncovered a previously unknown method by which androgen-activated androgen receptors (ARs) increase fucosyltransferase 4 (FUT4) expression, which promotes melanoma invasiveness by interfering with adherens junctions (AJs).
Study: Androgen drives melanoma invasiveness and metastatic spread by inducing tumorigenic fucosylation. Image Credit: Image Point Fr/Shutterstock.com
Background
Melanoma incidence and death rates are higher in males than in females, and sex hormones play a crucial role in the disease's biology and progression. Studies have demonstrated that androgen and its receptor have tumorigenic functions in melanoma, although the underlying processes are poorly understood.
Men with advanced melanoma typically have lower clinical outcomes. Sex hormones, such as G protein-coupled estrogen receptor (GPER) signaling, inhibit tumor development and boost anti-programmed death cell death 1 (anti-PD-1) immune checkpoint blockade effectiveness in a female mouse model.
Global fucosylation disrupts as melanoma progresses, affecting cell motility and ribonucleic acid (RNA) processing.
About the study
In the present study, researchers investigated ways in which sex-hormone-regulated fucosylation leads to disparately poor outcomes in male melanoma patients.
The researchers investigated the effects of androgen-induced and transcriptionally active androgen receptors on melanoma biology and tumorigenicity. They concentrated on the AR-FUT4 signaling pathway and its role in male sex-related biological consequences in melanoma.
They confirmed the presence of a putative androgen response element (ARE) in the FUT4 5'-promoter region and created mutant promoter constructs.
The researchers further confirmed the androgen receptor-fucosyltransferase-4 axis modulation of cell signaling pathways in melanoma by creating empty vector (EV) controls or fucosyltransferase 4-overexpressing (FUT4-OE) melanoma cells.
They conducted phosphoproteomic profiling of empty vectors and Ari-treated or untreated FUT4-overexpressing cells, followed by multiple-stage comparative analysis. The study sought to understand how ARs regulate fucosylation machinery genes and their significance in melanoma biology.
The team discovered 368 distinct proteins (denoted by 484 phosphopeptide proteins) that were decreased by ≥2.0-fold in ARi-treated empty vector-WM793 cells (ARi-reduced phosphopeptide proteins).
They then classified the phosphopeptides as those that FUT4 overexpression could restore (AR-FUT4-based effector molecules, n=95) and those unrestored by fucosyltransferase-4 overexpression ("AR-based, FUT4-independent effector molecules, n=241).
The researchers performed further ingenuity pathway analysis (IPA) on 141 androgen receptor-fucosyltransferase-4 axis down- or upregulated signatures in WM1366 and WM793 cells.
They measured the contacts between β-catenin, N-cadherin, and δ1-catenin, primary cytoplasmic adherens junction interactors. They performed proliferation and motility experiments to confirm the phosphoproteomic results and determine the effect of AR-FUT4-AJ signaling on melanoma biology.
The team also investigated whether FUT8 contributes to the motility effects caused by FUT4. They also assessed AR expression and its relationships with downstream effectors in human melanoma samples.
Results
Researchers uncovered a method by which androgen-activated androgen receptors increase FUT4 expression, which promotes melanoma invasiveness by interacting with AJs. FUT4 is a critical transcriptional target of AR, disrupting cell-cell adhesion complexes in melanoma.
AR-FUT4-mediated melanoma metastasis requires L1CAM, a downstream effector fucosylated by FUT4. Tumor microarray and gene expression analysis revealed that AR-FUT4-L1CAM-AJs signaling is associated with clinical staging in melanoma patients.
The researchers found that sex hormone-regulated fucosylation leads to the poor outcomes seen in male melanoma patients.
The mechanism shows that androgen or its receptor signaling influences melanoma malignancy by increasing invasive and metastatic potential through tumorigenic fucosylation.
Androgen/AR regulates cellular fucosylation in melanoma, with AR binding sites found in four genes (FUT4, FUT1, SLC35C2, and FUK). Androgen stimulation causes FUK to downregulate while FUT4 upregulates, indicating that AR modulates FUK and FUT4 expression in melanoma cells.
The researchers discovered that 2FF and FUT4-OE reduce and promote melanoma cell motility, but ectopic FUT4 expression restores ARi-suppressed invasive potential. FUT4 levels are higher in metastatic lesions than in original melanoma tissues.
They identified L1CAM as an essential target for the AR-FUT4 axis-induced melanoma invasiveness. FUT4-overexpressing cell lines produced more fucosylated proteins than FUT4-knockdown cell lines.
DHT stimulation significantly elevated the fucosylation of L1CAM, and knockdown or overexpression of FUT4 resulted in lower or higher cellular levels of fucosylated L1CAM. L1CAM deletion inhibited DHT- or FUT4-induced melanoma motility.
AR levels were higher in metastatic tumors from male patients, as was activated AR. Single-cell segmentation analysis revealed that metastatic lesions included fewer activated AR-high cells than initial tumors, demonstrating AR's tumor-promoting involvement, particularly in male melanoma patients.
Conclusion
The study findings showed that androgen-triggered signaling is critical in melanoma, specifically targeting AR/FUT4 and its effectors.
It supports the use of AR antagonists to treat melanomas and advises employing androgen- and fucosylation-based indicators to stratify therapy.
AR activation enhances tumorigenic FUT4, resulting in worse clinical outcomes in male patients. The work also relates the AR transcriptional repertoire to oncogenic protein fucosylation, which promotes melanoma invasiveness in androgen-responsive melanomas.
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