Abstract 4869: p27kip1 is a metastasis-associated antigen that promotes cell migration in osteosarcoma

Abstract

Abstract Metastasis is the leading cause of death in osteosarcoma (OS). Despite the advent of cancer therapy, patients with metastasis still have a dismal outcome. Hence, identification and characterization of new cellular targets that are critical to the metastatic process are urgently needed in order to improve both the treatment and detection of metastatic patients. Previous evidence has indicated that cancer patients produce autoantibodies. Many of these tumor-associated autoantibodies target cellular proteins that are essential for tumor formation. In this study, we used a high-density Human Protein Array (HPA) that contains over 8,000 purified proteins, to identify tumor-associated antigens that are associated with metastatic OS at the time of diagnosis. Plasma samples from patients with metastatic (n=10) or localized (n=16) OS, as well as hospitalized children with non-cancerous diseases (n=21) were pooled separately and analyzed using HPA. Totally, 16 autoantibodies were found to be reactive in metastatic OS. Of those, 6 of them showed higher prevalence in the metastatic cases relative to the localized cases and the control cases (p<0.01). One of these autoantibodies targets a cell cycle inhibitor protein, p27kip1, which is involved in tumor suppression and invasion. The higher prevalence of p27kip1 autoantibody in metastatic OS was subsequently validated using a novel HaloLink assay and individual plasma samples. To test if p27kip1 plays a role in metastatic OS, immunohistochemistry was performed on three pairs of metastatic OS cell lines and their parental, non-metastatic cell lines. We found that the p27kip1 protein, which is normally localized in the nucleus, was mislocalized in the cytoplasm in all three metastatic OS cell lines. Functional studies demonstrated that the wild type or CDK- mutant of p27kip1 harboring a nuclear export signal significantly induced OS cell migration in vitro. In summary, our results indicate that mislocalization of p27kip1 can promote metastatic potential of OS. Further characterization of p27kip1 and its related pathways may lead to the development of a novel therapeutic strategy for treating metastatic OS and other sarcomas. 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 4869. doi:10.1158/1538-7445.AM2011-4869