Prostate cancer (PCa) is a major global health concern, particularly in advanced stages where chemotherapy resistance and androgen-independent tumor growth reduce survival rates to below 30%. Toll-like receptor 3 (TLR3), regulated by tumor suppressor p53, is a promising therapeutic target due to its role in tumor cell apoptosis. However, chronic exposure to inorganic arsenic (iAs), a known carcinogen, has been linked to PCa progression and reduced TLR3 expression and activation by polyinosinic/polycytidylic acid (Poly(I/C)), a synthetic ligand used in PCa immunotherapy. Here, we demonstrate that chronic sodium arsenite (NaAsO) exposure increases p53 transcript and protein levels in immortalized prostate epithelial cells. Despite this, key p53 target genes, including TLR3, CDKN1A, and BAX, were significantly downregulated, indicating a transcriptionally inactive p53. Chromatin immunoprecipitation (ChIP) confirmed diminished p53 binding to TLR3 and CDKN1A promoters, while sequencing ruled out TP53 mutations. A bioinformatic analysis revealed elevated TP53 but reduced TLR3 and CDKN1A in prostate adenocarcinoma, suggesting that iAs-induced oxidative stress disrupts p53 function. These findings reveal a novel mechanism by which iAs promotes PCa progression through impaired p53 activity, highlighting the need to explore post-translational and epigenetic factors affecting p53. Restoring p53 transcriptional activity may offer a therapeutic strategy for PCa patients exposed to NaAsO.

Programmed cell death (PCD) in unicellular organisms is not well characterized. This study investigated the transcriptomic response of Acanthamoeba castellanii to G418-induced PCD, focusing on the role of alternative splicing (AS). RNA sequencing revealed extensive transcriptional changes, affecting approximately 70% of annotated genes over six hours of treatment. This analysis also highlighted significant alterations in pathways related to cell cycle, proteolysis, and RNA splicing. Analysis of AS events identified 18,748 differentially spliced events, predominantly intron retention (IR). Interestingly, retained introns displayed a 3′ bias in untreated cells, a pattern that shifted towards uniform distribution throughout the gene body during PCD. Additionally, we characterized retained introns during trophozoite stage and during PCD of the amoeba. Correlational analysis revealed a significant negative correlation between IR and transcript levels, suggesting a complex interplay between transcriptional and post-transcriptional regulation. The predominance of IR, coupled with its dynamic positional shift during PCD, points to a novel regulatory mechanism in A. castellanii PCD. These findings provide insights into the molecular mechanisms underlying PCD in this organism, potentially identifying new therapeutic targets and allowing us a better understanding of such process in A. castellanii, a facultative human pathogen.