Copper bioavailability is a KRAS-specific vulnerability in colorectal cancer

Abstract

Despite its importance in human cancers, including colorectal cancers (CRC), oncogenic KRAS has been extremely challenging to target therapeutically. To identify potential vulnerabilities in KRAS-mutated CRC, we characterize the impact of oncogenic KRAS on the cell surface of intestinal epithelial cells. Here we show that oncogenic KRAS alters the expression of a myriad of cell-surface proteins implicated in diverse biological functions, and identify many potential surface-accessible therapeutic targets. Cell surface-based loss-of-function screens reveal that ATP7A, a copper-exporter upregulated by mutant KRAS, is essential for neoplastic growth. ATP7A is upregulated at the surface of KRAS-mutated CRC, and protects cells from excess copper-ion toxicity. We find that KRAS-mutated cells acquire copper via a non-canonical mechanism involving macropinocytosis, which appears to be required to support their growth. Together, these results indicate that copper bioavailability is a KRASselective vulnerability that could be exploited for the treatment of KRAS-mutated neoplasms.

Targeting copper metabolism to defeat KRAS-driven colorectal cancer

“…Using ratiometric fluorescent probes to monitor labile pools of copper, 9 which contribute to metabolism, we found that KRAS mutation was linked to increased levels of bioavailable copper. 7 Consistent with this, we found that ATP7A participates in the regulation of several cuproenzymes, including Cytochrome C Oxidase (CCO) and the pathway leading to ERK1/2 (extracellular signal-regulated kinases 1/2) activation, which helps explain its observed essentiality in KRAS-mutated cells. 7 Our results have shown that KRAS-mutated cells are more sensitive to copper chelators, such as ammonium tetrathiomolybdate (TTM), than wild-type counterparts, suggesting that copper metabolism may be a potential therapeutic target for KRAS-mutated CRC.…”

“…7 Consistent with this, we found that ATP7A participates in the regulation of several cuproenzymes, including Cytochrome C Oxidase (CCO) and the pathway leading to ERK1/2 (extracellular signal-regulated kinases 1/2) activation, which helps explain its observed essentiality in KRAS-mutated cells. 7 Our results have shown that KRAS-mutated cells are more sensitive to copper chelators, such as ammonium tetrathiomolybdate (TTM), than wild-type counterparts, suggesting that copper metabolism may be a potential therapeutic target for KRAS-mutated CRC. Anti-Cu agents, such as TTM, choline tetrathiomolybdate (ATN-224), trientine, and D-penicillamine were previously shown to inhibit cancer cell growth in preclinical studies.…”

“…6 Using the macropinocytosis inhibitor 5-(N-ethyl-N-isopropyl) amiloride (EIPA), we found that macropinocytosis regulates intracellular copper levels and is required for KRAS-mutated CRC growth. 7 While macropinocytosis may not be the exclusive mode of copper uptake, our results indicate that it is required to fuel copper metabolism in KRAS-mutated CRC cells.…”

“…Using a proteogenomic approach to study mutant KRASmediated transformation of intestinal epithelial cells, we have identified the copper-transporter ATP7A (Coppertransporting ATPase 1) as a potent synthetic lethal target for KRAS-mutant CRC. 7 Combining cutting-edge cell-surface proteomics with CRISPR/Cas9 screens, we found that ATP7A is selectively elevated at the surface of KRAS G12V -transformed intestinal cells and plays essential roles in tumor growth in vitro and in vivo. Intriguingly, we found that ATP7A upregulation occurred in a transcription-independent manner that involved copper-dependent protein stabilization and intracellular transport, as described elsewhere.…”

“…Our results have shown that KRAS-mutant cells express reduced levels of CTR1 compared to control cells, and that its expression is dispensable for KRAS-dependent tumor growth. 7 Given that CTR1independent routes for copper uptake are not well described in humans, we evaluated the contribution of macropinocytosis, which is upregulated in KRAS-mutated cells and previously shown to participate in nutrient uptake. 6 Using the macropinocytosis inhibitor 5-(N-ethyl-N-isopropyl) amiloride (EIPA), we found that macropinocytosis regulates intracellular copper levels and is required for KRAS-mutated CRC growth.…”