Digoxin as a Potential Anticancer Agent in Melanoma Treatment ^†

Cutaneous melanoma (CM) is one of the most aggressive and lethal forms of skin cancer, characterized by a high rate of proliferation, marked local invasion, and high metastatic potential. The incidence of this type of cancer has increased significantly in recent decades, especially among the Caucasian population, which is frequently exposed to ultraviolet radiation. Although early diagnosis can lead to favorable survival rates, advanced forms of melanoma continue to pose major therapeutic challenges, particularly due to acquired resistance to standard therapies and rapid disease recurrence. In this context, oncological research has increasingly focused on repositioning existing drugs, especially those of natural origin, known for their clinical safety and well-established pharmacological profile [1,2]. One such compound is digoxin (Dgx), a cardiac glycoside extracted from the plant Digitalis purpurea, which has been used for over two centuries in the treatment of heart failure and arrhythmias [3]. Recently, Dgx has attracted the attention of researchers due to its antitumor effects, demonstrated in multiple experimental models, including melanoma cells [4] and ovarian cancer cells [5].

The present work was designed to evaluate the anticancer activity of Dgx as a potential alternative treatment for CM. The investigations were conducted on the A375 cell line, selected as an in vitro 2D experimental model for CM. Assessment of the cytotoxic potential of Dgx (75, 100, 125, 150, and 200 nM) was performed through a series of experiments on A375 cells, including determination of cell viability using the MTT technique, analysis of cell morphology and confluence, and examination of cell nuclei by staining with Hoechst 33,342 after a 24 h treatment. The results indicated that Dgx decreases the viability of CM cells in a dose-dependent manner (up to approximately 46%). The morphological cell analysis revealed a similar trend whereby increasing concentrations of Dgx enhanced the presence of dismorphologies (cell rounding, cell constriction, cell detachment from the plaque). In the same manner, cell confluency decreased with rising doses, confirming the dose-dependent effect of Dgx. In addition, staining with Hoechst 33,342 confirmed that the concentration of 200 nM Dgx induces apoptotic-like nuclear changes (such as nuclear condensation, nuclear shrinkage, and reduction in nuclear size).

In light of these findings, this study provides further support for the repositioning of Dgx as a potential adjuvant therapy for CM. In order to expand on these studies, investigating the exact mechanism of action, determining the impact in healthy experimental models, and verifying the biosafety profile will be fundamental aspects to explore. Future research directions include analyzing Dgx in other types of cancers, such as ovarian, breast, and prostate cancer, given the versatile biological properties that make this compound a potential candidate for alternative cancer treatments.