Scientists have been testing a type of RNA called small interfering RNA, or siRNA, as a brain tumor treatment. SiRNA can block the expression of genes that drive cancer growth. But RNA is fragile. To help it survive in the body long enough to have an effect, it has to be packaged in some type of microscopic carrier.
Source: https://www.nih.gov/news-events/nih-research-matters/delivering-rna-therapies-brain-tumors