Half of melanomas encode an oncogenic mutant BRAFV600E kinase, which phosphorylates MEK1/2 kinases and in turn ERK1/2, thereby activating the MAPK pathway to promote melanoma. Allosteric ATP inhibitors specific to mutant BRAF have revolutionized the treatment of this disease, providing a therapeutic response in more than half of patients with mutant BRAF-positive aggressive disease. However, patients invariably develop resistance to these inhibitors, typically through reactivation of the MAPK pathway through a variety of genetic changes. In this regard, an allosteric ATP inhibitor against MEK1/2 kinase of the MAPK pathway has been shown to clinically enhance the anti-neoplastic effects of a BRAF inhibitor. Thus, MEK1/2 are clinically validated targets for the treatment of BRAF-positive late stage melanoma. Inhibiting ATP is not the only way to target MEK1/2. Specifically, we discovered that dietary copper (Cu) is a co-factor for these two enzymes. Moreover, we also found that reducing expression of the primary Cu transporter CTR1 or mutating the Cu-binding sites on MEK1 inhibits the tumor growth of BRAFV600E-positive tumor cell lines. Importantly, high Cu levels in patients with Wilson's disease are clinically lowered wih Cu-reducing drugs. Excitingly, treatment of mice with one of these drugs, TM, reduced the tumor growth of BRAFV600E-positive tumor cell lines and extended the lifespan of mice genetically engineered to develop metastatic melanoma. Thus, TM is a MEK1/2 inhibitor that has a completely novel mechanism of action that is fundamentally different from current allosteric ATP inhibitors of these enzymes. Based on these new data, we initiated a clinical cancer trial (NCT02068079) to test the combination of a Cu chelator with a BRAF inhibitor on BRAF mutation-positive, late stage melanoma patients. Given these advances, we have reformulated the A1 grant to now focus on the next most clinically relevant and pressing issues, namely identifying the most effective cancer settings to implement Cu chelation (aim 1) and improving upon the anti- neoplastic activity of Cu chelators (aim 2). Completion of these aims will thus determine how best to capitalize upon the advantages of Cu chelation as a means to inhibit MEK1/2 for the treatment of BRAF mutation-positive, late stage melanoma, and develop a pipeline of novel therapeutic approaches that improve upon Cu chelators for future clinical analysis.
Upwards of a fifth of cancers, and half of melanomas have an activating mutation in the gene BRAF. Thus, the proposed studies repurpose relatively safe and economical drugs used to lower Cu levels in humans for the treatment of BRAF mutation-positive cancers like melanoma are directly relevant to public health.
|Brady, Donita C; Crowe, Matthew S; Greenberg, Danielle N et al. (2017) Copper Chelation Inhibits BRAFV600E-Driven Melanomagenesis and Counters Resistance to BRAFV600E and MEK1/2 Inhibitors. Cancer Res 77:6240-6252|