Cytidinyl/Cationic Lipids-siRNA Delivery Silences MYC to Reprogram Macrophages and Circadian Rhythm for Cancer Treatment

Nonsmall cell lung cancer (NSCLC) remains a leading cause of cancer-related mortality, with <i>MYC</i> oncogene overexpression driving tumor progression and immunosuppression. MYC has been deemed "undruggable" for a long period, and the impact of its silencing on the tumor associated macrophage polarization and circadian rhythm remains unexplored. Here, we developed a lipid nanoparticle (siMYC@Dmix) composed of cytidinyl lipid (DNCA), gemini-like cationic lipid (CLD), and DSPE-PEG2000 for efficient <i>MYC</i> siRNA delivery. In vitro, siMYC@Dmix showed robust cellular uptake, lysosomal escape, and ∼77% <i>MYC</i> mRNA silencing in Lewis Lung Carcinoma (LLC) cells. In vivo, siMYC@Dmix treatment significantly inhibited tumor growth in C57BL/6J mice and induced a profound remodeling of the tumor immune microenvironment. This was characterized by a shift in macrophage polarization toward the M1 phenotype, increased infiltration and cytotoxic function of CD8⁺ T cells, enhanced natural killer (NK) cell activity, and maturation of dendritic cells (DCs). Crucially, <i>MYC</i> silencing restored the expression of core circadian clock genes. Our findings unveil a promising RNAi-based strategy that concurrently targets <i>MYC</i>-driven tumorigenesis, corrects circadian dysfunction, and reinstates antitumor immunity, presenting a multifaceted therapeutic approach for NSCLC.