Building on an effort to reverse-engineer gene networks in order to identify cancer-causing genes, a team from the Wyss Institute was able to identify the main culprit in breast cancer: the HoxA1 gene. 

This discovery led to a novel method of treating the cancerous cells with siRNA, which blocks only the HoxA1 gene. The siRNA was loaded into lipidiods—nanoparticles that allow the gene to remain silenced within the body for weeks—and injected directly thought the nipples into the milk ducts of cancer-prone mice, which resulted in the mice remaining cancer-free while the untreated mice when on to develop breast cancer.

By injecting nanoparticles carrying a gene-silencing snippet of RNA directly into the nipple, Wyss Institute scientists delivered this therapy to the entire milk-duct network, where breast cancer first gets started.