Evaluating targeting of the G2 catenation checkpoint as a novel tumour specific vulnerability

Primary Supervisor: Tanya Soliman, Queen Mary University of London

Secondary supervisor: Miraz Rahman, King’s College London

Project

Small molecule inhibitors targeting protein kinases is an active area of drug discovery. Recent work by the Soliman and Rahman laboratories (Nature Communications, 2020) has demonstrated that more complex biology underlies signalling through protein kinases which presents a new opportunity to selectively target pathways driving genome instability and aneuploidy. We have shown that a post-translational modification of Aurora B kinase by phosphorylation of S227 not only effects the downstream signalling output, but does so through a conformational change resulting in a switch in substrate specificity. This change in conformation reveals differences in structure for which the Rahman lab have designed a preliminary series of inhibitors for the two Aurora B phospho-species. We will use advanced computational techniques to screen in-house compounds library containing 26,000 drug like chemical scaffolds and Zinc compound database to identify compounds against both phospho-species. The synthesis candidates will be selected after performing MD simulation of candidate compounds.

Once compounds have been designed and synthesised, the student will progress to testing the efficacy of the compounds structurally (by NMR spectroscopy), biochemically and biologically. The lead compound/s will be taken forward to test in our model exploiting a known tumour specific vulnerability. Targeting vulnerabilities acquired by cancer cells (and thereby avoiding normal, non-cancerous tissue) is a promising anti-cancer strategy, the use of PARP inhibitors in homologous recombination defective tumours, is an example of one such strategy. Our data suggests that a subset of tumours (eg. non-small cell lung carcinoma, high grade serous ovarian cancer) have a defective G2 catenation checkpoint; cells enter mitosis before adequately detangling (decatenating) replicated chromosomes which can lead to segregation errors and genomic instability. Our prior work demonstrated cells with a defective G2 catenation checkpoint are reliant on signalling through the kinase Aurora B which has been phosphorylated at S227, to delay transit through mitosis until catenation is resolved. Taken together, we now hypothesise that G2 checkpoint defective cells may rely heavily on this alternative failsafe pathway, presenting an opportunity to target Aurora B signalling pathways and specifically kill tumour cells through mitotic catastrophe. Tumour cells with a defective G2 catenation checkpoint can be sensitised to Aurora B-dependent pathway signalling with topoisomerase 2 catalytic inhibitors, a number of which are approved for clinical use.

The specific aims of the project are:

1. to design and synthesise small molecule kinase inhibitors against Aurora B S227 phospho-species.
2. examine the in vitro and in vivo effects of the lead compound/s on Aurora B structure, activity and signalling
3. assess the efficacy of Aurora B inhibition in G2 catenation checkpoint deficient cell models.

In this multidisciplinary project, the student will acquire skills in organic synthesis, including the development of new synthetic schemes, purification and characterisation of small molecules. This will be complemented by training in molecular biology, cancer biology, drug screening and the mechanistic evaluation of candidate drugs.

Candidate background

The project would be suitable for a candidate with a background in biomedical sciences and a keen interest in drug discovery and cancer cell biology. A knowledge of biochemistry or medicinal chemistry would be an advantage but not essential.

Potential Research Placements

1. Mark Pfuhl, Randall Centre, King’s College London
2. Pedro Cutillas, Mass Spectrometry Core Facility, Barts Cancer Institute, Queen Mary University of London
3. Agostino Cilibrizzi, IPS, King’s College London

References

1. Kelly, J.R., et al, 2020. The Aurora B specificity switch is required to protect from non-disjunction at the metaphase/anaphase transition. Nature Communications 11, 1396. https://doi.org/10.1038/s41467-020-15163-6
2. Deiss, K., et al., 2019. A genome-wide RNAi screen identifies the SMC5/6 complex as a non-redundant regulator of a Topo2a-dependent G2 arrest. Nucleic Acids Research 47, 2906?2921. https://doi.org/10.1093/nar/gky1295
3. Lewis, T., Corcoran, D. B., Thurston, D. E., Giles, P. J., Ashelford, K., Walsby, E. J., Fegan, C. D., Pepper, A. G., Rahman, K. M., and Pepper, C. (2021) Novel pyrrolobenzodiazepine benzofused hybrid molecules inhibit nuclear factor-?B activity and synergize with bortezomib and ibrutinib in hematologic cancers, haematologica 106, 958.
4. Corcoran, D. B., Lewis, T., Nahar, K. S., Jamshidi, S., Fegan, C., Pepper, C., Thurston, D. E., and Rahman, K. M. (2019) Effects of Systematic Shortening of Noncovalent C8 Side Chain on the Cytotoxicity and NF-kappa B Inhibitory Capacity of Pyrrolobenzodiazepines (PBDs), Journal of Medicinal Chemistry 62, 2127-2139.