Abstract P2-05-13: A novel mutagenesis screen identifies SHARPIN as a breast cancer metastasis gene that predicts survival of breast cancer patients

Abstract

Abstract Breast cancer (BC) is a heterogeneous disease and the second leading cause of malignancy among women in the U.S.. Metastasis of the primary tumor results in poor prognosis and increased mortality and the molecular mechanisms by which metastatic tumors occur are not well understood. Identifying the genes that drive the metastatic process could provide targets for improved therapy and biomarkers to improve outcomes for BC patients. Here, we utilized a replication-incompetent gammaretroviral vector (γRV) to perform a forward insertional mutagenesis screen to identify genes involved in BC metastasis. In this approach, BC cells mutagenized with a γRV were xenotransplanted into the mammary fat pad of immunodeficient mice, and primary tumors and metastases were allowed to develop. Metastatic lesions were collected and analyzed for proviral integration sites to identify vector integration sites and nearby candidate metastasis genes. The γRV has a bacterial origin of replication and kanamycin resistance gene that allows for rescue in bacteria and rapid identification of vector integration sites. Using this approach, we identified the previously described metastasis gene WWTR1, and several other novel candidate metastasis genes including SHARPIN. SHARPIN was then independently validated as a BC metastasis gene in vivo using RNAi. Analysis of patient data showed that SHARPIN expression predicts metastasis-free survival after adjuvant chemotherapy (p < 0.005, Concordance Index = 55.3, Risk Groups Hazard Ratio = 1.87). Our replication-incompetent γRV approach is efficient and has broad potential to identify genes involved in oncogenic processes for BC and other cancers. Keywords Insertional mutagenesis screen, Gammaretroviral vector (γRV), Metastasis, Inducible shRNA, Prognostic biomarker. Citation Format: Bii VM, Rae DT, Trobridge GD. A novel mutagenesis screen identifies SHARPIN as a breast cancer metastasis gene that predicts survival of breast cancer patients. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-05-13.