Abstract 2188: Effect of the protein complex formation of a novel tumor suppressor HLJ1 and nuclear protein p54nrb on human lung adenocarcinoma cell migration and invasion

Lung cancer is the most common cause of cancer deaths in the world, and the incidence is increasing each year. In the previous studies, we have identified and characterized a novel tumor/invasion suppressor gene HLJ1 (human liver DnaJ-like protein, also called DNAJB4) in a lung cancer cell line model with different invasion capability. However, the suppressive mechanism of HLJ1 is unclear. Therefore, the objective of this study is to investigate and characterize the proteins interacting with HLJ1. To obtain the novel HLJ1-binding protein, the differentially cultured density of tumor cell is employed to mimic metastatic characteristics in vitro. We identified two proteins, p54nrb and PSF, that can interact with HLJ1 in high cell culture density by immunoprecipitation assay and MALDI-TOF analysis. The complex of HLJ1 and p54nrb was confirmed in vitro and in vivo by co-immunoprecipitation, GST pull-down and mammalian two-hybrid assay. In addition, the results of GST pull-down assay indicated that p54nrb can interact with HLJ1 through HTH motif. We also found that the expressions of both HLJ1 and p54nrb are increased in A549, CL1-0, CL1-5 and CL1-5F4 cancer cell lines while are culturing in high cell density. The results of immunofluorescent staining and cytosolic/nuclear protein fraction revealed that p54nrb is mainly located in the nucleus. Furthermore, we found that over-expression of p54nrb protein in the highly invasive lung cancer cell line, CL1-5, can reduce cancer cell proliferation, colony formation, invasion and migration. On the other hand, p54nrb was decreased when most cells are in DNA synthesis phase. Once over-expression of p54nrb in CL1-5 cell line, the cell cycle would arrest in G1 phase to reduce cancer cell proliferation. Investigating the action mechanism of HLJ1-p54nrb interaction is important, it may not only provide a new insight to understand the pathway of metastasis and growth regulation but also be as the new target molecule for anti-cancer therapy in the future. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2188. doi:10.1158/1538-7445.AM2011-2188