nc886 (= pre-miR-886 or vtRNA2-1) is a non-coding RNA that has been recently identified as a natural repressor for the activity of PKR (Protein Kinase R). The suppression of nc886 activates PKR and thereby provokes a cell death pathway. When combined with the fact that nc886 is suppressed in a wide range of cancer cells, the nc886-PKR relationship suggests a tumor surveillance model. When neoplastic cells develop and nc886 decreases therein, PKR is released from nc886 and becomes the active phosphorylated form, which initiates an apoptotic cascade to eliminate those cells. The nc886-PKR pathway is distinct from conventional mechanisms, such as the immune surveillance hypothesis or intrinsic mechanisms that check/proofread the genomic integrity, and thus represents a novel example of tumor surveillance.
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