Transforming tumor microenvironments: nanotechnology and gene therapy in cellular signaling and epigenetic insight into chemo-resistance.

Chemoresistance remains the primary cause of cancer treatment failure, yet current understanding remains fragmented across isolated mechanistic studies. This review provides a unified framework linking tumor microenvironment (TME) signaling, epigenetic reprogramming, and nanotherapeutic intervention as an integrated axis driving and potentially reversing chemoresistance. We systematically examine how TME components: hypoxia (HIF-1α pathway), acidosis, cancer-associated fibroblasts (TGF-β/PDGF signaling), and immune cells (NF-κB-mediated immunosuppression) activate signaling cascades that directly interface with epigenetic machinery. These TME-activated pathways recruit DNA methyltransferases, histone-modifying enzymes, and regulate microRNA (miRNA) networks, establishing stable resistant phenotypes including epithelial-mesenchymal transition, cancer stem cells, and metabolic adaptation. Critically, miRNA dysregulation serves as a central integrator, creating bidirectional crosstalk between signaling pathways and epigenetic modifications through self-reinforcing circuits. Unlike previous reviews focusing on isolated resistance mechanisms, we demonstrate how this integrated TME-epigenetic axis creates specific therapeutic vulnerabilities exploitable through rationally designed nanotechnology platforms delivering epigenetic modulators (DNMT inhibitors, HDAC inhibitors, EZH2 inhibitors) and gene therapy tools (CRISPR-Cas9 epigenetic editors, miRNA mimics/antagomirs). We critically evaluate clinical translation challenges, including EPR effect heterogeneity, delivery barriers, and biomarker gaps, providing a balanced perspective on both potential and obstacles. This mechanistic framework guides the development of next-generation combination therapies targeting multiple nodes within the TME-epigenetic-nanotherapy axis.