Copper chelation suppresses epithelial-mesenchymal transition by inhibition of canonical and non-canonical TGF-beta signaling pathways in cancer

Background Metastatic cancer cells exploit Epithelial-mesenchymal-transition (EMT) to enhance their migration, invasion, and resistance to treatments. Recent studies highlight that elevated levels of copper are implicated in cancer progression and metastasis. Clinical trials using copper chelators are associated with improved patient survival; however, the molecular mechanisms by which copper depletion inhibits tumor progression and metastasis are poorly understood. This remains a major hurdle to the clinical translation of copper chelators. Here, we propose that copper chelation inhibits metastasis by reducing TGF-beta levels and EMT signaling. Given that many drugs targeting TGF-beta have failed in clinical trials, partly because of severe side effects arising in patients, we hypothesized that copper chelation therapy might be a less toxic alternative to target the TGF-beta/EMT axis. Results Our cytokine array and RNA-seq data suggested a link between copper homeostasis, TGF-beta and EMT process. To validate this hypothesis, we performed single-cell imaging, protein assays, and in vivo studies. Here, we used the copper chelating agent TEPA to block copper trafficking. Our in vivo study showed a reduction of TGF-beta levels and metastasis to the lung in the TNBC mouse model. Mechanistically, TEPA significantly downregulated canonical (TGF-beta/SMAD2&3) and non-canonical (TGF-beta/PI3K/AKT, TGF-beta/RAS/RAF/MEK/ERK, and TGF-beta/WNT/beta-catenin) TGF-beta signaling pathways. Additionally, EMT markers of MMP-9, MMP-14, Vimentin, beta-catenin, ZEB1, and p-SMAD2 were downregulated, and EMT transcription factors of SNAI1, ZEB1, and p-SMAD2 accumulated in the cytoplasm after treatment. Conclusions Our study suggests that copper chelation therapy represents a potentially effective therapeutic approach for targeting TGF-beta and inhibiting EMT in a diverse range of cancers.

Automated summary

Metastatic cancer cells use Epithelial-mesenchymal-transition (EMT) to enhance migration, invasion, and treatment resistance, and elevated levels of copper are implicated in cancer progression and metastasis. Copper chelation therapy can inhibit metastasis by reducing TGF-beta levels and EMT signaling, making it a potentially effective therapeutic approach for targeting TGF-beta and inhibiting EMT in various cancers.