Metformin Bicarbonate-Mediated Efficient RNAi for Precise Targeting of Deficiency in Colon and Rectal Cancers.

Colon and rectal cancers are the leading causes of cancer-related deaths in the United States and effective targeted therapies are in need for treating them. Our genomic analyses show hemizygous deletion of , an important tumor suppressor gene, is highly frequent in both cancers, and the 5-year survival of patients with the more prevalent colon cancer is significantly reduced in the patients with the cancer harboring such deletion, although such reduction is not observed for rectal cancer. Unfortunately, direct targeting has been unsuccessful for cancer therapy. Interestingly, , a gene essential for cell survival and proliferation, is almost always deleted together with in colon and rectal cancers. Therefore, RNA interference (RNAi) with small interfering RNAs (siRNAs) to precisely target/inhibit may be an effective strategy for selectively killing cancer cells with deficiency. However, the difficulty of delivering siRNAs specifically into the cytosol where they perform their function, is a major barrier for siRNA-based therapies. Here, metformin bicarbonate (MetC) is synthesized to develop pH-responsive MetC-nanoparticles with a unique "bomb" for effective cytosolic delivery of siRNA, which greatly facilitates its endo/lysosomal escape into the cytosol and augments its therapeutic efficacy of cancer harboring deficiency. Moreover, the MetC-based nanoparticles without functional siRNA show notable therapeutic effect with no evident toxicity or immunogenicity.