Polo-like kinase 1 (Plk1) is one of the most attractive targets for anti-cancer therapy. Efforts to generate Plk1-specific inhibitors by targeting the catalytic activity of Plk1 have proven to be difficult due to similarities with the catalytic domains of other structurally related kinases. Here, we propose to develop a new class of mono-specific Plk1 inhibitors by employing a novel approach of targeting the non-catalytic, but functionally essential, PBD of Plk1. To this end, we have carried out a high throughput screen in collaboration with National Center for Advancing Translational Sciences (NCATS), Bethesda, MD. My NIH X01 grant proposal was approved for this particular project. From this screen, we have identified 3,000 compounds from a primary screen, which were narrowed down to the final 2 compounds (1S and B7) through secondary medium throughput and tertiary cell-based assays. For optimization of the final two compounds, we carried out molecular modeling/docking of the parent compounds in the Plk1 PBD to design and synthesize more water-soluble analogs (in collaboration with Dr. Terry Burke at NCI-Frederick). As a result of our initial effort to optimize the 1S compound, we obtained six significantly improved compounds, which showed Plk1 PBD inhibition activity at levels similar to that of PLHSpT (Kd = 450 nM) in an in vitro ELISA. Since the original HTS leads may belong to a class known as pan-assay interference compounds, or PAINS, we will further incorporate many drug-like characteristics during the hit-to-lead optimization in order to obtain a high-impact chemical probe that ultimately exhibits the desired efficacy against the Plk1 PBD in proof-of-concept mouse tumor models.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Investigator-Initiated Intramural Research Projects (ZIA)
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Park, Jung-Eun; Hymel, David; Burke Jr, Terrence R et al. (2017) Current progress and future perspectives in the development of anti-polo-like kinase 1 therapeutic agents. F1000Res 6:1024
Park, Jung-Eun; Kim, Tae-Sung; Kim, Bo Yeon et al. (2015) Selective blockade of cancer cell proliferation and anchorage-independent growth by Plk1 activity-dependent suicidal inhibition of its polo-box domain. Cell Cycle 14:3624-34
Qian, Wen-Jian; Park, Jung-Eun; Grant, Robert et al. (2015) Neighbor-directed histidine N (?)-alkylation: A route to imidazolium-containing phosphopeptide macrocycles. Biopolymers 104:663-73
Lee, Kyung S; Burke Jr, Terrence R; Park, Jung-Eun et al. (2015) Recent Advances and New Strategies in Targeting Plk1 for Anticancer Therapy. Trends Pharmacol Sci 36:858-877
Kim, Ju Hee; Ku, Bonsu; Lee, Kyung S et al. (2015) Structural analysis of the polo-box domain of human Polo-like kinase 2. Proteins :
Jia, Jia-Lin; Han, Young-Hyun; Kim, Hak-Cheol et al. (2015) Structural basis for recognition of Emi2 by Polo-like kinase 1 and development of peptidomimetics blocking oocyte maturation and fertilization. Sci Rep 5:14626
Qian, Wen-Jian; Park, Jung-Eun; Lim, Dan et al. (2014) Mono-anionic phosphopeptides produced by unexpected histidine alkylation exhibit high Plk1 polo-box domain-binding affinities and enhanced antiproliferative effects in HeLa cells. Biopolymers 102:444-55
Srinivasrao, Ganipisetti; Park, Jung-Eun; Kim, Sungmin et al. (2014) Design and synthesis of a cell-permeable, drug-like small molecule inhibitor targeting the polo-box domain of polo-like kinase 1. PLoS One 9:e107432
Kim, Sun-Ok; Sakchaisri, Krisada; Thimmegowda, N R et al. (2013) STK295900, a dual inhibitor of topoisomerase 1 and 2, induces G(2) arrest in the absence of DNA damage. PLoS One 8:e53908
Qian, Wenjian; Park, Jung-Eun; Liu, Fa et al. (2013) Effects on polo-like kinase 1 polo-box domain binding affinities of peptides incurred by structural variation at the phosphoamino acid position. Bioorg Med Chem 21:3996-4003

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