Screening for DUSP4/6 small molecule inhibitors in lung adenocarcinoma

Lung cancer (LC) is the leading cause of cancer-related mortalities both in Canada and worldwide. This is due to limited treatment options with curative potential as a result of therapeutic resistance. This underlies the need for novel therapeutics with new gene targets and mechanisms of action. Patients with lung adenocarcinoma (LUAD) have a number of driver gene mutations that upregulate signaling through the mitogen activated protein kinase (MAPK) signaling pathway, and its key effectors, the extracellular signal regulated kinases (ERK1/2). Conventional targeted therapies aim to downregulate ERK signaling. However, recent findings have shown that excessive ERK1/2 signaling, termed ERK hyperactivation, can be toxic to cancer cells. ERK1/2 signaling is regulated by dual specificity phosphatases (DUSP) 4 and 6, highlighting the potential of DUSP4/6 inhibition as a novel avenue for LUAD therapeutic development. There is currently no dual inhibitor of DUSP4/6. The aim of this thesis work was to screen and identify small molecule dual inhibitors of DUSP4/6, and to evaluate their therapeutic potential in LUAD. Through enzymatic assays using purified DUSP4 and DUSP6, I screened two lead compounds and 57 derivatives for their ability to act as dual inhibitors. I identified a compound termed VPC002 as a candidate dual inhibitor and found that it is more potent than (E)-2-benzylidene-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one (BCI), a known DUSP6 inhibitor. In models of LUAD harbouring MAPK activating mutations, I found that VPC002 induced ERK hyperactivation. In those same models, VPC002 was able to reduce cell viability. Testing in LC lines without MAPK mutations also induced toxicity, potentially as a result of off-target effects. These results provide insight into VPC002’s mechanism of action and highlight the potential of dual DUSP inhibition as a therapeutic strategy in LUAD. Overall, this screening pipeline provides a foundation for the future development of novel LUAD therapeutics to improve patient outcomes.