miRNA–lncRNA Cross-Regulation Landscape in Cancer: From Molecular Mechanisms to Therapeutic and Diagnostic Applications

: Background/Objectives: Over the past two decades, non-coding RNAs (ncRNAs) have emerged as key regulators of gene expression, reshaping the classical view of the genome as predominantly protein-coding. Among them, microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) play central roles in controlling gene expression at multiple levels. Rather than acting independently, these molecules form complex and interconnected regulatory networks, and their interplay appears particularly relevant in cancer. This review aims to examine the mechanisms underlying miRNA-lncRNA cross-regulation and to explore their functional and clinical implications in tumor biology. Methods: We performed a comprehensive analysis of the current literature focusing on studies investigating miRNA-lncRNA interactions in cancer. Particular attention was given to mechanistic insights, including the competing endogenous RNA (ceRNA) hypothesis, as well as alternative regulatory models involving direct RNA interactions and chromatin-associated processes. Results: miRNA-lncRNA interactions have been associated with cancer progression and therapeutic response across different tumor types, although their mechanisms are highly context-dependent. While the ceRNA hypothesis, based on competition for shared microRNA response elements (MREs), provides a useful framework, it does not fully explain all observed phenomena. Evidence shows that miRNAs can directly regulate lncRNA stability, whereas lncRNAs can influence miRNA biogenesis. Additionally, chromatin-related mechanisms suggest that these interactions extend beyond post-transcriptional regulation. These RNA networks intersect with major oncogenic pathways, including PI3K/AKT/mTOR signaling, hypoxia responses, and epigenetic regulators such as EZH2, thereby affecting key cancer processes such as proliferation, epithelial-mesenchymal transition (EMT), and metabolic reprogramming. From a clinical perspective, the stability of ncRNAs in biological fluids highlights their potential as biomarkers. Combined miRNA-lncRNA signatures may improve diagnostic and prognostic accuracy compared to single markers, although further validation is required. Therapeutic strategies targeting ncRNA networks, such as miRNA mimics, antagomiRs, and lncRNA-directed approaches, are under investigation; however, challenges related to delivery, specificity, and toxicity remain. Conclusions: miRNA-lncRNA cross-regulation represents a complex and multifaceted layer of gene regulation in cancer. A deeper understanding of these interactions could support the development of more accurate diagnostic tools and more effective RNA-based therapeutic strategies, although significant technical and biological challenges still need to be addressed.