Abstract 4376: Evaluation of PRP4 kinase as a potential drug target in cancer.
Authors: Gao Qiang , Mechin Ingrid , Kothari Nayantara , Guo Zhuyan , Deng Gejing , Wang Anlai , Wiederschain Dmitri , Rocnik Jennifer , Czechtizky Werngard , Liu Feng , Majid Tahir , Patel Vinod , Lengauer Christoph , Garcia-Echeverria Carlos , Zhang Bailin , Cheng Hong , Dorsch Marion , Huang Shih-Min A. 
Published: August 2014

Abstract
PRP4 kinase plays a crucial role in regulating pre-mRNA splicing, cell cycle progression, proliferation, and survival. The aforementioned functions have been well documented in Schizosaccharomyces pombe, Caenorhabditis elegans, and human cancer cell lines. For example, it was demonstrated that PRP4 kinase is essential for growth in fission yeast, and disruption of C. elegans PRP4 by RNAi resulted in a highly penetrant early embryonic lethality. In experiments utilizing siRNAs to screen for kinases essential for pancreatic cancer cell survival, PRP4 knockdown was demonstrated to increase apoptosis and decrease viability. In a genome-wide pooled shRNA screen, shRNAs against PRP4 was shown to reduce the viability of DLD-1, HCT-116, and HCC1954 cancer cell lines. Similarly, PRP4 kinase was identified as a potential therapeutic target in a pooled shRNA screen designed to identify genes required for proliferation and survival of diffuse large B-cell lymphoma cell lines. Moreover, in an effort to reveal potential kinase targets to treat multidrug resistance ovarian cancer, inhibition of PRP4 activity by shRNAs was shown to re-sensitize chemo-resistant human ovarian cancer to paclitaxel treatment. Interestingly, loss of PRP4 kinase was also demonstrated to enhance paclitaxel activity in breast cancer cells. To further investigate PRP4 kinase substrate spectrum and explore the druggability of PRP4 kinase, we utilize quantitative proteomics and structural biology to help achieve these objectives. In this report, we provided evidence that the kinase domain of PRP4 is essential for regulating cell growth and survival. In addition, through a global proteomics approach, we expanded the interactome and phosphoproteome of PRP4 kinase in cancer cells and identifed novel substrates of PRP4, including oncogenic PAK4 kinase. Subsequently, these substrates were substantiated in orthogonal biochemical and cellular assays. These new biological findings not only identify suitable biomarkers to monitor PRP4 kinase activity, but also provide interesting avenues for future in-depth interrogation of PRP4 functions in cancer biology and clinical development. Finally, we solve the X-ray structure of the PRP4 kinase domain and identify several features suitable for the rational design of PRP4 kinase inhibitors. We further provided the co-crystal structure of PRP4 kinase domain in complex with a small molecule and elucidated the exploitable mechanisms to synthesize potent and specific PRP4 inhibitors. Future efforts will be focused on understanding patient stratification strategy and assessing the utility of PRP4 kinase inhibitors in relevant pre-clinical models of cancer.
Citation Format: Qiang Gao, Ingrid Mechin, Nayantara Kothari, Zhuyan Guo, Gejing Deng, Anlai Wang, Dmitri Wiederschain, Jennifer Rocnik, Werngard Czechtizky, Feng Liu, Tahir Majid, Vinod Patel, Christoph Lengauer, Carlos Garcia-Echeverria, Bailin Zhang, Hong Cheng, Marion Dorsch, Shih-Min A. Huang. Evaluation of PRP4 kinase as a potential drug target in cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4376. doi:10.1158/1538-7445.AM2013-4376