Since the first report of the RNA interference (RNAi) phenomenon in 1990, and the debut of the terminology and theory of RNAi on the center stage of science in 1998, RNAi pathways, including the exogenously synthesized small interfering RNAs (siRNAs) and short-hairpin RNAs (shRNAs), and the endogenously self-produced microRNAs (miRNAs) and other kinds of non-coding RNAs (ncRNAs), have been confirmed to cause gene silencing in various species. The techniques of sequencing, bioinformatic tools, and the public depository of various kinds of sequencing data lead to the discovery of more and more RNAi subjects (miRNAs, ncRNAs, siRNAs and shRNAs), their gene targets, and the extensive pathways they involve, forming a huge network regulated by different levels of feedback. The subjects found in RNAi are commonly seen participating in the pathogenesis, diagnosis, treatment, and prognosis of different kinds of cancer.

Thanks to the development of the above techniques and the cut-down in research costs, the number of miRNAs discovered has increased rapidly, as well as the discovery of other RNAi subjects, the pathways they involve, and their roles in different species and diseases. Therefore, it is of significant importance to keep up with the new findings in this hot research field so as to provide new clues for the clinical applications of RNAi.

The purpose of this Special Issue is to collate the latest updates in basic, translational, pharmacological, and clinical research on the comprehensive roles of RNAi in cancer-regulating gene modification, cancer cell origination, surveillance, proliferation, migration, invasion, and metastasis, as well as the diagnosis, prognosis, treatment, and drug resistance of clinical cases. Original research and review articles are welcome.

Potential topics include but are not limited to the following:

• Cancer-regulating gene modification using RNAi
• Novel techniques to discover and analyze RNAi subjects and their gene targets
• Comparison of efficiency and toxicity of techniques to deliver RNAs into cells and the off-target effects
• The role and application of extracellular vesicles in cancer
• RNAi in cancer stem cells
• RNAi mechanisms in cancer cell proliferation, metastasis, and cancer recurrence
• RNAi in cancer immune regulation and inflammatory response
• RNAi in the diagnosis, prognosis, treatment, and drug development and resistance of cancer cases
• RNAi in other important and novel aspects of cancer