Methods and materials providing a route for the use of transgenic plants as bio-factories to produce therapeutic miRNAs are described. The plants can be ingestible and can be used to deliver to a subject in need thereof a therapeutic miRNA by ingestion of the bioengineered plant tissue that carries an exogenous genetic sequence for the therapeutic miRNA. The therapeutic miRNA can be useful in treating a disease state such as cancer. The therapeutic miRNA can be a mammalian tumor suppressor miRNA.