Multi-Omic Evaluation of PLK1 Inhibitor—Onvansertib—In Colorectal Cancer Spheroids

Polo-like kinase 1 (Plk1) is a serine/threonine kinase involved in regulating the cell cycle. It is activated by aurora kinase B along with the cofactors Borealin, INCE, and survivin. Plk1 is involved in the development of resistances to chemotherapeutics such as doxorubicin, Taxol, and gemcitabine. It has been shown that patients with higher levels of Plk1 have lower survival rates. Onvansertib is a competitive ATP inhibitor for Plk1 in clinical trials for the treatment of tumors and has recently entered a trial for the treatment of KRAS mutant colorectal cancers (CRCs). In this study, we conducted an untargeted liquid chromatography–mass spectrometry (LC–MS) proteomics study as well as an untargeted lipidomics analysis of HCT 116 spheroids treated with onvansertib over a 72-h treatment time-course experiment. Mass spectrometry imaging (MSI) showed that onvansertib begins to accumulate most prominently after 12 h of treatment and continues to accumulate through 72 h. Proteomic results displayed alterations to cell cycle control proteins and an increasing abundance of aurora kinase B and Borealin. The proteomics data also showed alterations to many lipid metabolism enzymes. The MSI lipidomics data indicated alterations to phosphatidylcholine lipids, with many lipids increasing in abundance over time or increasing until 12 h of onvansertib treatment and decreasing after that time point. In summary, these results suggest that onvansertib is causing cells within the spheroid to halt at a certain phase of the cell cycle in accordance with previous literature. Our findings suggest the S phase is likely interrupted, with observed alterations in cell cycle control proteins and PC lipid abundance.