Heterogeneous Nuclear Ribonucleoprotein K (hnRNP-K) Promotes Tumor Metastasis by Induction of Genes Involved in Extracellular Matrix, Cell Movement, and Angiogenesis

Cancer is a leading cause of death and still awaits effective therapies. Rapid industrialization has contributed to increase in incidence of cancer. One of the reasons why most of the cancers fail therapy is due to their metastatic property. Hence identification of factors leading to metastasis is highly important to design effective and novel anti-cancer therapeutics. In our earlier study (Inoue, A., Sawata, S. Y., Taira, K., and Wadhwa, R. (2007) Loss-of-function screening by randomized intracellular antibodies: identification of hnRNP-K as a potential target for metastasis. Proc. Natl. Acad. Sci. U.S.A. 104, 8983–8988), we had reported that the involvement of heterogeneous nuclear ribonucleoprotein K (hnRNP-K) in metastasis. Here, we established hnRNP-K-overexpressing and -underexpressing derivative cell lines and examined their proliferation and metastatic properties in vitro and in vivo. Whereas hnRNP-K compromised cells showed delayed tumor growth, its overexpression resulted in enhanced malignancy and metastasis. Molecular basis of the hnRNP-K induced malignant and metastatic phenotypes was dissected by cDNA microarray and pathway analyses. We found that the hnRNP-K regulates extracellular matrix, cell motility, and angiogenesis pathways. Involvement of the selected genes (Cck, Mmp-3, Ptgs2, and Ctgf) and pathways was validated by gene-specific expression analysis. Our results demonstrated that the hnRNP-K is a potential target for metastasis therapy.Background: Cancer metastasis is a major hurdle in cancer therapy and needs identification of novel targets for drug designing.Results: hnRNP-K is highly expressed in cancer cells and regulates extracellular matrix, cell motility, and angiogenesis pathways.Conclusion: hnRNP-K is a potential target for metastasis therapy.Significance: hnRNP-K expression level may serve as a marker of metastatic cancers, and hnRNP-K-inhibiting drugs could be candidate anti-cancer and anti-metastasis reagents.