Pigmentation-dependent expression of pheomelanogenesis-related genes in human melanoma cells

Introduction
Melanin synthesis is regulated by a complex genetic network, and its dysregulation can promote malignant transformation. Pheomelanin, a lighter and more photoreactive form of melanin, contributes to oxidative stress and may facilitate melanoma development. Its abundance varies with skin phototype, but its role in melanoma cell biology remains poorly characterized, highlighting the need to study pheomelanogenic gene expression in cells with distinct pigmentary.

Aim
To address this, we analysed the expression of 44 genes related to melanocyte development and pigmentation, focusing on those directly or indirectly involved in pheomelanogenesis. Moreover, the melanin content in the examined cell lines was estimated.

Material and methods
The study was conducted in two human melanoma cell lines that display contrasting pigmentation, amelanotic C32 and melanotic G361, using real-time RT-PCR to quantify gene expression levels. The melanin content in both cell lines was evaluated using Py-GC/MS/MS.

Results
The content of melanin markers, normalised to one million cells, was 62% lower in amelanotic C32 cells than in melanotic G361 cells. Within the total isolated melanin pool, pheomelanin accounted for 0.52% in the C32 line and 0.78% in the G361 line. Melanoma cell lines with divergent melanin content also exhibited distinct gene-expression profiles: G361 cells showed higher expression of POMC, MC1R, TYRP1, TYR, SLC45A2 and CTNS, whereas SLC7A11 and DCT were more abundantly expressed in C32 cells.

Conclusions
These findings indicate that variation in melanin content is closely linked to molecular heterogeneity in melanoma, underscoring the contribution of pheomelanin-related pathways to divergent melanoma phenotypes.