The heterogeneous nuclear ribonucleoprotein-A2/B1 (hnRNP-A2/B1) was recently shown to be up-regulated in th e early stage of lung cancer. This protein plays an important role in biogenesis and transport of mRNA. Up-regulation of hnRNP usually precedes morphological differentiation and is considered a good biomarker in the early stages of cancer development. HnRNP-A2/B1 proteins were localized primarily in the nucleus, excluding the nucleolus, although the expression of A2 protein was weaker than that of B1 protein. hnRNP-A2/B1 proteins were apparently expressed in nonmalignant alveolar cells as well as cancer cells, although the expression in alveolar cells was weaker than that of cancer cells.Synonyms: HNRPA2B1, Heterogeneous nuclear ribonucleoproteins A2/B1, hnRNP A2 / hnRNP B1