Altered patterns of expression of members of the heterogeneous nuclear ribonucleoprotein (hnRNP) family in lung cancer

Abstract

hnRNP A2/B1 has been suggested as a useful early detection marker for lung carcinoma. hnRNP A2/B1 is a member of a large family of heterogeneous nuclear ribonucleoproteins (hnRNP proteins) involved in a variety of functions, including regulation of transcription, mRNA metabolism, and translation. In lung cancer, we have evaluated the expression and cellular localization of several members of the hnRNP family, hnRNP A1, A2, B1, C1, C2 and K. 16 cell lines (SCLC and NSCLC) and biopsies from 32 lung cancer patients were analyzed. Our results suggest that, besides hnRNP A2/B1, the expression of other members of the hnRNP family is altered both in SCLC and NSCLC. In the biopsies, negative or low expression of the hnRNP proteins analyzed was observed in normal epithelial cells whereas lung cancer cells showed highly intense nuclear or cytoplasmic immunolocalization. In all the lung cancer cell lines, the mRNA for all the hnRNP proteins was detected. In general, higher levels of hnRNP mRNAs were found in SCLC as compared with NSCLC. Our results also suggest that the expression and processing of each hnRNP protein in lung cancer is independently regulated and is not exclusively related to proliferation status. In SCLC cell lines, hnRNP A1 protein expression correlated with that of Bcl-x(L). In the lung cancer cell lines, hnRNP K protein localization varied with the cellular confluence.