LAUSR

The DAB2IP tumor suppressor protein is a member of the Ras GTPase-activating protein family and is often downregulated by epigenetic silencing in many advanced cancer types. Current literature indicates that DAB2IP plays a crucial role in suppression of the PI3K-Akt pathway and epithelial-mesenchymal transition. Loss of DAB2IP is often detected in advanced prostate cancer (PCa) and is associated with increased androgen receptor signaling and poor patient prognosis. Here we report that loss of DAB2IP is also resulted in chromosomal instability due to defects in kinetochore-microtubule (KT-MT) attachment and the spindle assembly checkpoint (SAC) during mitotic cell cycle transition. Chromosomal instability is one of the key hallmarks of carcinogenesis and has been linked to metastasis, poor prognosis, and therapy resistance in cancer. Our results further indicate that DAB2IP directly interacts with Plk1, and its loss attenuates Plk1 kinase activity and Plk1-dependent BubR1 phosphorylation which is required for BubR1 localization at the kinetochore during mitosis and SAC regulation. Consequently, loss of DAB2IP leads to increased resistance of PCa cells toward microtubule stabilizing drugs (paclitaxel, docetaxel) and Plk1 inhibitor (BI2536). Our findings demonstrate a novel function of DAB2IP in the maintenance of KT-MT structure and proper SAC regulation during mitosis to promote chromosomal stability and genome integrity. Citation Format: Lan Yu, Zeng-Fu Shang, Benjamin P. C. Chen, Debabrata Saha. Tumor suppressor protein DAB2IP participates in chromosomal stability maintenance through activating spindle assembly checkpoint and stabilizing kinetorchore-microtubule attachments [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr A39.