This study explores the impact of antiretroviral administration on the expression of human endogenous retroviruses (HERVs), cell growth, and invasive capability of human melanoma cell lines in culture. We investigated three antiretrovirals—lamivudine, doravirine, and cabotegravir—in A375, FO-1, and SK-Mel-28, BRAF-mutated, and in MeWo, P53-mutated, melanoma cell lines. The findings indicate a general capability of these drugs to downregulate the expression of HERV-K Pol and Env genes and hinder cell viability, mobility, and colony formation capacity of melanoma cells. The antiretroviral drugs also demonstrate selectivity against malignant cells, sparing normal human epithelial melanocytes. The study reveals that the integrase inhibitor cabotegravir is particularly effective in inhibiting cell growth and invasion across different cell lines in comparison with lamivudine and doravirine, which are inhibitors of the viral reverse transcriptase enzyme. The investigation further delves into the molecular mechanisms underlying the observed effects, highlighting the potential induction of ferroptosis, apoptosis, and alterations in cell cycle regulatory proteins. Our findings showed cytostatic effects principally revealed in A375, and SK-Mel-28 cell lines through a downregulation of retinoblastoma protein phosphorylation and/or cyclin D1 expression. Signs of ferroptosis were detected in both A375 cells and FO-1 cells by a decrease in glutathione peroxidase 4 and ferritin expression, as well as by an increase in transferrin protein levels. Apoptosis was also detected in FO-1 and SK-Mel-28, but only with cabotegravir treatment. Moreover, we explored the expression and activity of the stimulator of interferon genes (STING) protein and its correlation with programmed death-ligand 1 (PD-L1) expression. Both the STING activity and PD-L1 expression were decreased, suggesting that the antiretroviral treatments may counteract the detrimental effects of PD-L1 expression activation through the STING/interferon pathway triggered by HERV-K. Finally, this study underscores the potential therapeutic significance of cabotegravir in melanoma treatment. The findings also raise the prospect of using antiretroviral drugs to downregulate PD-L1 expression, potentially enhancing the therapeutic responses of immune checkpoint inhibitors.

Melanoma is an aggressive cancer characterized by rapid growth, early metastasis, and poor prognosis, with resistance to current therapies being a significant issue. BRAF mutations drive uncontrolled cell division by activating the MAPK pathway. In this study, A375 and FO-1, BRAF-mutated melanoma cell lines, were treated for 4–5 months with RAF inhibitor dabrafenib or AZ628, leading to drug resistance over time. The resistant cells showed altered molecular signatures, with differences in cell cycle regulation and the propensity of cell death. Dabrafenib-resistant cells maintained high proliferative activity, while AZ628-resistant cells, especially A375 cells, exhibited slow-cycling, and a senescent-like phenotype with high susceptibility to ferroptosis, a form of cell death driven by iron. Antiretroviral drugs doravirine and cabotegravir, known for their effects on human endogenous retroviruses, were tested for their impact on these resistant melanoma cells. Both drugs reduced cell viability and colony formation in resistant cell lines. Doravirine was particularly effective in reactivating apoptosis and reducing cell growth in highly proliferative resistant cells by increasing tumor-suppressor proteins p16^Ink4a and p27^Kip1. These findings suggest that antiretroviral drugs can influence apoptosis and cell proliferation in RAF-inhibitor-resistant melanoma cells, offering potential therapeutic strategies for overcoming drug resistance.

Oxidative stress is a major driver of neuroinflammation, yet the molecular redox mechanisms that shape microglial activation remain incompletely defined. Among reversible redox modifications, protein S-glutathionylation has emerged as a key regulator of signaling cascades under conditions of elevated Reactive Oxygen Species (ROS). While IFNγ is known to activate STAT1 and promote a pro-inflammatory microglial phenotype, the contribution of oxidative stress to this process is poorly understood. Here, we investigated the interplay between ROS and STAT1 signaling in IFNγ-stimulated microglial cells. We demonstrate that ROS not only enhance STAT1 phosphorylation but also promote its S-glutathionylation, a modification that sustains STAT1 transcriptional activity. This dual regulation leads to prolonged expression of pro-inflammatory mediators, including iNOS, COX2, TNFα, and IL-6. Importantly, STAT1-deficient cells fail to mount these responses, confirming STAT1 as a central redox-sensitive hub in microglial polarization. Our findings identify S-glutathionylation as a molecular switch that links oxidative stress to persistent STAT1 activation and M1 polarization. These results suggest that targeting STAT1 redox regulation could help control microglial overactivation and may offer new opportunities for therapeutic intervention in neuroinflammatory and neurodegenerative diseases.

Advanced melanoma remains difficult to treat due to its intrinsic resistance to conventional therapies and the frequent development of acquired resistance to targeted agents, such as BRAF inhibitors. Onconase (ONC), an amphibian ribonuclease with established antitumor activity, had been previously shown to have selective cytotoxicity toward melanoma cells. In this study, we investigated the molecular mechanisms underlying ONC-induced cytotoxicity in BRAF-mutated melanoma cell lines that are either sensitive or resistant to the BRAF inhibitor dabrafenib. We focused on oxidative stress regulation, mitochondrial dynamics, and cell death-related signaling pathways. ONC treatment resulted in a marked increase in reactive oxygen species (ROS) levels, concomitant with a pronounced downregulation of NRF2 and multiple NRF2-dependent antioxidant proteins. These effects were particularly evident in dabrafenib-resistant melanoma cells. In parallel, ONC impaired mitochondrial plasticity by inhibiting mitochondrial biogenesis and fission, as evidenced by reduced PGC1α, DRP1, and FIS1 expression. Confocal analysis confirmed the presence of more enlarged mitochondria in ONC-treated cells. Mitophagy and autophagy are hindered by ONC due to the downregulation of PINK1, beclin1, ATG3 expression, as well as the lack of LC3B activation. These mitochondrial defects were associated with mitochondrial-dependent apoptosis, characterized by caspase-9 activation and strong downregulation of the antiapoptotic protein survivin. Lipid peroxidation was also induced by ONC, especially in the A375 cell line. Additionally, ONC inhibited key proliferation-related signaling pathways, including STAT3 and NF-κB, and reduced cyclin-dependent kinase 1, 2, and 4 activities. Collectively, these findings demonstrate that ONC disrupts redox homeostasis, mitochondrial function, and survival signaling in melanoma cells, exerting particularly potent effects in BRAF inhibitor-resistant populations. This study provides mechanistic insight into the anti-melanoma activity of ONC and supports its potential therapeutic application in drug-resistant melanoma.