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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - NuSiCC (Modelling the therapeutic potential of NUAK1 suppression in colorectal cancer)

Teaser

Summary

\"Colorectal cancer (CRC) kills up to 170,000 Europeans annually. Although 10-year survival rates have increased at a reasonably steady rate, resistance to therapy is an ongoing concern and new therapies are certainly needed. Colorectal cancer is somewhat unique in that the mutations that commonly drive the disease coalesce around a limited number of well-defined genetic pathways, and the Cancer Genome Atlas project has shown that increased activity of the MYC oncogene in particular appears to be a unifying feature of the disease. MYC however is a poor target for direct pharmacological inhibition. We have therefore sought to identify indirect means of exploiting the consequences of MYC deregulation, rather than targeting MYC itself. The concept of \"\"synthetic lethality\"\" offers one such approach: Synthetic lethality is said to exist when mutation in either one of a pair of genes is tolerable but simultaneous mutation of both kills the cell. Synthetic dosage lethality is conceptually similar, except that one of the genes may be overexpressed rather than mutated. Our previous work identified a synthetic dosage lethal interaction between MYC and a little-known kinase called NUAK1: we demonstrated that cancer cells overexpressing MYC are highly dependent upon co-expression of NUAK1 and thereby highly sensitive to suppression of NUAK1. Because NUAK1 appears to be an excellent target for small molecule inhibition, the implication is thus that it may be possible to kill tumour cells that overexpress MYC by inhibiting NUAK1. Inhibitors of NUAK1 are presently at an early stage of development that precludes directly testing this concept in vivo. We have therefore taken a genetic approach to examine the requirement for NUAK1 during tumour development in a genetically engineered mouse model of sporadic Beta-Catenin-driven CRC. Our preliminary results showed that NUAK1 is required for CR tumour initiation and, more importantly, that NUAK1 depletion shrinks pre-existing tumours, suggesting that NUAK1 is an excellent candidate target for treatment of CRC. Hence, the main objectives of the project were to thoroughly evaluate NUAK1 as a target for therapy in CRC and to use a combination of proteomic, phosphor-proteomic and metabolomic analysis to determine the mechanism by which NUAK1 suppression erodes tumour cell viability.
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Work performed

During the time-frame of the project we could show by using mouse models of colorectal cancer (CRC) that NUAK1 deletion inhibits colon tumour initiation, and acute genetically-mediated depletion of NUAK1 by shRNA in established tumours significantly reduces tumour burden after just 7 days of shRNA activation. Importantly, depletion of NUAK1 in mouse wildtype intestine had no impact on cell death, proliferation or differentiation, and wildtype 3D organoids were resistant to NUAK1 inhibition. Using human CRC cell lines and transformed 3D organoid cultures, we have confirmed that the NRF2 oxidative stress response is compromised in NUAK1 depleted cells, and treatment with a ROS scavenger can rescue the detrimental consequences of this in vitro, ex vivo and in vivo. Mechanistically, we found that NUAK1 is necessary for the nuclear accumulation of NRF2 by counteracting negative regulation of this process by GSK3Î².
In summary, we are proposing a new and conserved mechanism of redox signal transduction in which activation of NUAK1 coordinates PP1Î²MYPT1 inhibition, with AKT activation in order to suppress GSK3Î²-dependent inhibition of NRF2 nuclear import. Exploiting the heightened sensitivity of tumour cells to ROS is emerging as a plausible strategy for cancer therapy and is implicated in the resistance to chemotherapy. Therefore, inhibiting the anti-oxidant response via transient inhibition of NUAK1 may offer a new strategy for improving therapeutic outcomes in cancer.
Results of this project were presented at several national and international conferences and a research article published (Cancer Discov. 2018 May;8(5):632-647). Furthermore, several datasets were published that were generated while working on the project.

Final results

The socio-economic impact of the project is manifold. The newly developed mouse model (Vil-CreER;Apcfl/+;DI-shNuak1) and antibody (p-NUAK1) will be available for other researchers to use and will make a further advancement of the role of NUAK1 and its potential utilization for anti-cancer therapy possible. In the longer term the finding that colorectal tumours require NUAK1 for protection from oxidative stress could be exploited as a novel therapeutic approach by inhibiting the anti-oxidant response via transient inhibition of NUAK1. Hence, colorectal cancer patients could potentially benefit from the development of new therapies resulting in prolonged survival combined with a better quality of life. Given the widespread deregulation of MYC across a broad spectrum of human cancer types, it is plausible to hope that the strategy of targeting NUAK1 will prove effective in many cancers beyond CRC.
As a kinase, NUAK1 holds much promise as a target for small molecule inhibition and several tool compounds are already available, attesting to the feasibility of inhibiting NUAK1. Our pre-clinical data could potentially encourage investment in NUAK1-selective drug development, generating new sources of revenue and employment within the pharmaceutical sector. The University of Glasgow is benefiting a) from any commercial outputs arising from this work and b) from the prestige garnered as a result of the scientific advances made during this project.