Abstract
Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) has been reported to be overexpressed in lung cancer and in other cancers such as breast, pancreas, and liver. However, a mechanism linking hnRNP A2/B1 overexpression and progression to cancer has not yet been definitively established. To elucidate this mechanism, we have silenced hnRNPA2/B1 mRNA in non-small-cell lung cancer cell lines A549, H1703, and H358. These cell lines present different levels of expression of epithelial-to-mesenchymal transition (EMT) markers such as E-cadherin, fibronectin, and vimentin. Microarray expression analysis was performed to evaluate the effect of silencing hnRNP A2/B1 in A549 cells. We identified a list of target genes, affected by silencing of hnRNP A2/B1, that are involved in regulation of migration, proliferation, survival, and apoptosis. Silencing hnRNP A2/B1 induced formation of cell clusters and increased proliferation. In the anchorage-independent assay, silencing hnRNP A2/B1 increased colony formation by 794% in A549 and 174% in H1703 compared with a 25% increase in proliferation, in both cell lines, in a two-dimensional proliferation assay. Silencing hnRNP A2/B1 decreased migration in intermediate cell line A549 and mesenchymal cell line H1703; however, no changes in proliferation were observed in epithelial cell line H358. Silencing hnRNP A2/B1 in A549 and H1703 cells correlated with an increase of E-cadherin expression and downregulation of the E-cadherin inhibitors Twist1 and Snai1. These data suggest that expression of hnRNP A2/B1 may play a role in EMT, in nonepithelial lung cancer cell lines A549 and H1703, through the regulation of E-cadherin expression.
Highlights
Heteregeneous nuclear ribonucleoprotein A2/B1 is a member of the hnRNP family of proteins
Silencing hnRNP A2/B1 in lung cancer cell lines siA and siD sequences are separated by only 12 nucleotides, the silencing effects observed with these oligonucleotides are very different. siD was able to show a moderate but not consistent silencing of hnRNP A2/B1. siE had no effect in silencing hnRNP A2/B1. siA was the only construct that showed consistent and significant silencing of hnRNP A2/B1 compared with empty vector (EV) (Fig. 1A)
Because previous observations have suggested a cooperative interaction between hnRNP A2/B1 and hnRNP A1, we evaluated expression of hnRNP A1 after silencing hnRNP A2/B1
Summary
Heteregeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) is a member of the hnRNP family of proteins. HnRNP A2/B1 overexpression has been described in many cancers, including breast, pancreas, liver, and gastrointestinal cell lines [5,6,7,8]. Recent reports have described a critical role of hnRNP A2/B1 in the regulation of fundamental biology especially related to cancer, such as migration [9] and aerobic glycolysis [10]. Authors' Affiliations: 1Laboratory of Lung Cancer Biology, Section of Medical Oncology, Rush University Medical Center, Chicago, Illinois; 2NCI Angiogenesis Core Facility, National Cancer Institute, NIH, Advanced Technology Center, Gaithersburg, Maryland; 3Science Applications International Corporation, Rockville, Maryland; and 4Biometric Research Branch, Division on Cancer Treatment and Diagnosis, National Cancer Institute, NIH, Bethesda, Maryland. Corresponding Author: Jordi Tauler, Rush University Medical Center, Room 1413, Jelke Building, 1750 West Harrison Street, Chicago, IL 60612. Phone: 312-942-3595; Fax: 312-563-3377; E-mail: Jordi_Tauler@ rush.edu
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