A Novel Small-Molecule Inhibitor of MRCK Prevents Radiation-Driven Invasion in Glioblastoma

Glioblastoma (GBM) is an aggressive and incurable primary brain tumor that causes severe neurologic, cognitive, and psychologic symptoms. Symptoms are caused and exacerbated by the infiltrative properties of GBM cells, which enable them to pervade the healthy brain and disrupt normal function. Recent research has indicated that although radiotherapy (RT) remains the most effective component of multimodality therapy for patients with GBM, it can provoke a more infiltrative phenotype in GBM cells that survive treatment. Here, we demonstrate an essential role of the actin-myosin regulatory kinase myotonic dystrophy kinase-related CDC42-binding kinase (MRCK) in mediating the proinvasive effects of radiation. MRCK-mediated invasion occurred via downstream signaling to effector molecules MYPT1 and MLC2. MRCK was activated by clinically relevant doses per fraction of radiation, and this activation was concomitant with an increase in GBM cell motility and invasion. Furthermore, ablation of MRCK activity either by RNAi or by inhibition with the novel small-molecule inhibitor BDP-9066 prevented radiation-driven increases in motility both in vitro and in a clinically relevant orthotopic xenograft model of GBM. Crucially, treatment with BDP-9066 in combination with RT significantly increased survival in this model and markedly reduced infiltration of the contralateral cerebral hemisphere.Significance: An effective new strategy for the treatment of glioblastoma uses a novel, anti-invasive chemotherapeutic to prevent infiltration of the normal brain by glioblastoma cells.Cancer Res; 78(22); 6509-22. ©2018 AACR.

Abstract 1933: A novel small molecule inhibitor of MRCK shows utility in blocking radiation induced invasion of glioblastoma cells in vitro and in vivo

Myotonic dystrophy kinase-related CDC42-binding kinases MRCKα and MRCKβ regulate actin-myosin contractility and are members of the AGC family of serine/threonine kinases. MRCKs are closely related to the Rho-regulated ROCK kinases, which is reflected in their shared abilities to phosphorylate a similar set of substrates, including myosin II light chain proteins (MLC) and myosin phosphatase target subunit 1 (MYPT1). However, MRCK and ROCK may phosphorylate these substrates at different subcellular localisations leading to diverging effects on cell invasion and migration.

Glioblastoma (GBM) is an aggressive and incurable primary brain tumor. Patients are treated with surgery, radiotherapy and chemotherapy but prognosis remains poor, with a median survival of 15 months. Complete surgical resection of GBM is difficult because these tumours are frequently invasive. Recent research has indicated that, while radiotherapy extends life expectancy of patients, it can provoke a more infiltrative phenotype in those GBM cells that survive treatment.

We have developed potent and selective small molecule MRCK inhibitors exemplified by BDP-9066, which inhibits pMLC in a selective cellular assay with an EC50 28.3 nM, whilst displaying high selectivity over ROCK1 where the EC50 10.6 µM. This compound, and others in the series, have been used in numerous cellular assay systems to demonstrate that MRCK inhibition suppresses the invasion and migration of cancer cells including, breast, skin SCC and glioblastoma.

We have used BDP-9066 to demonstrate that MRCK inhibition is effective at perturbing radiation-induced migration of GBM cells in culture at concentrations that block phosphorylation of MLC. Using a clinically relevant intracranial mouse model that recapitulates key histological features of the disease, we have shown that BDP-9066 inhibits the invasion of G7 GBM cells into the contralateral hemisphere of the brain. These experiments highlight the potential utility of MRCK inhibition in the treatment of GBM in patients.

Citation Format: Heather J. McKinnon, Joanna Birch, Laura McDonald, Mairi Sime, Daniel Croft, Diane Crighton, Martin Drysdale, Lesley Gilmore, Christopher Gray, Jennifer Konczal, Duncan McArthur, Patricia McConnell, Mokdad Mezna, Alexander Schuettelkopf, Karen Strathdee, Justin Bower, Michael F. Olson, Anthony J. Chalmers. A novel small molecule inhibitor of MRCK shows utility in blocking radiation induced invasion of glioblastoma cells in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1933.

Discovery of Potent and Selective MRCK Inhibitors with Therapeutic Effect on Skin Cancer

The myotonic dystrophy-related Cdc42-binding kinases MRCKα and MRCKβ contribute to the regulation of actin-myosin cytoskeleton organization and dynamics, acting in concert with the Rho-associated coiled-coil kinases ROCK1 and ROCK2. The absence of highly potent and selective MRCK inhibitors has resulted in relatively little knowledge of the potential roles of these kinases in cancer. Here, we report the discovery of the azaindole compounds BDP8900 and BDP9066 as potent and selective MRCK inhibitors that reduce substrate phosphorylation, leading to morphologic changes in cancer cells along with inhibition of their motility and invasive character. In over 750 human cancer cell lines tested, BDP8900 and BDP9066 displayed consistent antiproliferative effects with greatest activity in hematologic cancer cells. Mass spectrometry identified MRCKα S1003 as an autophosphorylation site, enabling development of a phosphorylation-sensitive antibody tool to report on MRCKα status in tumor specimens. In a two-stage chemical carcinogenesis model of murine squamous cell carcinoma, topical treatments reduced MRCKα S1003 autophosphorylation and skin papilloma outgrowth. In parallel work, we validated a phospho-selective antibody with the capability to monitor drug pharmacodynamics. Taken together, our findings establish an important oncogenic role for MRCK in cancer, and they offer an initial preclinical proof of concept for MRCK inhibition as a valid therapeutic strategy.Significance: The development of selective small-molecule inhibitors of the Cdc42-binding MRCK kinases reveals their essential roles in cancer cell viability, migration, and invasive character. Cancer Res; 78(8); 2096-114. ©2018 AACR.

A novel small-molecule MRCK inhibitor blocks cancer cell invasion

BACKGROUND

The myotonic dystrophy kinase-related CDC42-binding kinases MRCKα and MRCKβ regulate actin-myosin contractility and have been implicated in cancer metastasis. Along with the related ROCK1 and ROCK2 kinases, the MRCK proteins initiate signalling events that lead to contractile force generation which powers cancer cell motility and invasion. A potential strategy for cancer therapy is to reduce metastasis by blocking MRCK activity, either alone or in combination with ROCK inhibition. However, to date no potent small molecule inhibitors have been developed with selectivity towards MRCK.

RESULTS

Screening a kinase-focused small molecule chemical library resulted in the identification of compounds with inhibitory activity towards MRCK. Medicinal chemistry combined with in vitro enzyme profiling led to the discovery of 4-chloro-1-(4-piperidyl)-N-[5-(2-pyridyl)-1H-pyrazol-4-yl]pyrazole-3-carboxamide (BDP00005290; abbreviated as BDP5290) as a potent MRCK inhibitor. X-ray crystallography of the MRCKβ kinase domain in complex with BDP5290 revealed how this ligand interacts with the nucleotide binding pocket. BDP5290 demonstrated marked selectivity for MRCKβ over ROCK1 or ROCK2 for inhibition of myosin II light chain (MLC) phosphorylation in cells. While BDP5290 was able to block MLC phosphorylation at both cytoplasmic actin stress fibres and peripheral cortical actin bundles, the ROCK selective inhibitor Y27632 primarily reduced MLC phosphorylation on stress fibres. BDP5290 was also more effective at reducing MDA-MB-231 breast cancer cell invasion through Matrigel than Y27632. Finally, the ability of human SCC12 squamous cell carcinoma cells to invade a three-dimensional collagen matrix was strongly inhibited by 2 μM BDP5290 but not the identical concentration of Y27632, despite equivalent inhibition of MLC phosphorylation.

CONCLUSIONS

BDP5290 is a potent MRCK inhibitor with activity in cells, resulting in reduced MLC phosphorylation, cell motility and tumour cell invasion. The discovery of this compound will enable further investigations into the biological activities of MRCK proteins and their contributions to cancer progression.

A nursing intervention to decrease depression in family caregivers of persons with dementia

The goal of this study was to evaluate a community-based psychoeducational-nursing intervention designed to teach home caregivers to manage behavioral problems of persons with Alzheimer's disease and related dementias (ADRD) using the Progressively Lowered Stress Threshold (PLST) model, and to compare this intervention with routine information and referrals for case management, community-based services, and support groups. Previous caregiver studies have overwhelmingly pointed to the adverse effects of caregiving on the caregivers' physical and mental health, and high prevalence rates of depression among caregivers of persons with ADRD have consistently been reported. Therefore, a primary aim was to evaluate the impact of the intervention on caregivers' affective responses, especially depression. Data from both the Profile of Moods States and the Geriatric Depression Rating Scale support the effectiveness of this intervention in decreasing depression among caregivers who received the experimental training. Additional analysis of factors associated with caregiver depression are also reported. The pivotal role of psychiatric nurses in the assessment and treatment of depression among caregivers of persons with ADRD is discussed.