Reduction-responsive RNAi nanoplatform to reprogram tumor lipid metabolism and repolarize macrophage for combination pancreatic cancer therapy

Pancreatic cancer (PAC) is one of the most lethal malignant neoplasms with poor prognosis and high mortality. Emerging evidence has revealed that abnormal tumor lipid metabolism and tumor-associated macrophages (TAMs) significantly contribute to PAC development and progression. Therefore, concurrently reprogramming tumor lipid metabolism and regulating TAMs function could be a promising strategy for effective PAC therapy. Herein, we identified an important enzyme catabolizing lipids (monoacylglycerol lipase, MGLL) and a key receptor regulating macrophage phenotype (endocannabinoid receptor-2, CB-2) that are over-expressed in PAC cells and on TAMs, respectively. Based on this finding, we developed a reduction-responsive poly (disulfide amide) (PDSA)-based nanoplatform for systemic co-delivery of MGLL siRNA (siMGLL) and CB-2 siRNA (siCB-2). This nanoplatform could utilize its reduction-responsive characteristic to rapidly release siRNA for efficient silencing of MGLL and CB-2, inducing concurrent suppression of free fatty acids (FFAs) generation in PAC cells and repolarization of TAMs into tumor-inhibiting M1-like phenotype. With this suppressed FFAs generation to inhibit nutrient supply for tumor cells and repolarized TAMs to secrete tumoricidal cytokines such as TNF-α and IL-12, a combinational anticancer effect could be achieved in both xenograft and orthotopic PAC tumor models.