Heterogeneous nucleus ribonucleoprotein (hnRNP) K is a component of the hnRNP complex, encoding for a 464 amino acid protein that mediates DNA and RNA binding. It is involved in the transcription, splicing and translation processes and recently implicated in tumorigenesis. Several oncogenes, such as c-Src, eIF4E and c-myc are regulated by hnRNP K. Correlation between elevated expression of hnRNP K and tumor development and progression are well documented. It has also been found to enhance cell proliferation and neoplastic transformation.

In normal tissues, hnRNP K is present primarily in the nucleus. Nuclear and aberrant cytoplasmic overexpression have been described in colorectal, prostate, hepatic, esophageal, and breast cancers that have been significantly associated with poor prognosis.