Silent Guardians Gone Rogue: The Role of PIWI and piRNA in Malignant Transformation

ABSTRACT Malignant transformation is not merely the consequence of stochastic genetic mutations but rather a convergence of complex interplay between genetic, epigenetic, and environmental factors that collectively reprogram normal cells into cancerous ones. Central to these processes is the loss of tumor suppressor genes, activation of oncogenes, chromosomal instability, and widespread epigenetic remodeling. A pivotal aspect of this transformation involves the contribution of ncRNAs that have been recurrently implicated in malignant transformation. While much attention is directed toward miRNAs, circRNAs, and lncRNAs, piRNAs have remained comparatively overlooked in cancer biology. This is despite a growing body of evidence implicating piRNAs in regulating tumorigenic pathways, genomic stability, and epigenetic gene silencing. Our review explores the emerging role of the piRNAs and their regulatory protein PIWI in modulating key malignant features, including hyperproliferation, EMT, tumor evasion, migration, angiogenesis, and others. We also examine how this axis influences the initiation and progression of cancer, highlighting its potential to reshape established paradigms in cancer studies.