Introduction

There is a current lack of molecularly targeted therapies that target tumour growth and dissemination for High Grade Serous Ovarian Cancer (HGSOC) patients. Myotonic dystrophy kinase-related CDC42-binding kinases (MRCK) α/β were identified as promising therapeutic targets based on results from multiplexed kinase inhibitor beads/mass spectrometry profiling of HGSOC tumour samples. Furthermore, MRCK inhibition was found to reduce the viability of ovarian cancer cells grown in 2D monolayers and 3D spheroids, consistent with MRCK representing a novel potential HGSOC target.

MRCK and Rho-associated Protein Kinase (ROCK) both contribute to Myosin II Regulatory Light Chain (MLC) and Myosin Phosphatase Target Subunit 1 (MYPT1) phosphorylation, thus contributing to changes in cell adhesion and motility. In addition, Focal Adhesion Kinase (FAK) is a validated driver of ovarian cancer proliferation and resistance to platinum based therapies. 

Methods/Results

To characterize the roles of MRCKα/β in ovarian cancer cells, CRISPR/Cas9 was used to knockout MRCKα and/or MRCK in OVCAR8 cells. In contrast to the ~ 50% decrease in MYPT1 phosphorylation following treatment of OVCAR8 cells with a potent and selective MRCK inhibitor, BDP9066, the single MRCKα, MRCKβ, or double MRCKα/β knockouts showed little decrease in MYPT1 phosphorylation. These observations suggested that there might be compensation for the reduction in MRCK signalling through another pathway such as RhoA/ROCK. Consistent with this possibility, the greatest decreases in MYPT1 and FAK phosphorylation were observed when MRCK and ROCK pharmacological inhibitors were combined.

Conclusion

Future studies will investigate the mechanistic basis for the compensation in MYPT1 and FAK phosphorylation following MRCK inhibition. The results of these studies will determine whether MRCK inhibition would be most effective when combined with ROCK or FAK inhibitors for HGSOC therapy.