HAO1-mediated oxalate metabolism promotes lung pre-metastatic niche formation by inducing neutrophil extracellular traps

Metabolic reprogramming has been shown to be involved in cancer-induced pre-metastatic niche (PMN) formation, but the underlying mechanisms have been insufficiently explored. Here, we showed that hydroxyacid oxidase 1 (HAO1), a rate-limiting enzyme of oxalate synthesis, was upregulated in the alveolar epithelial cells of mice bearing metastatic breast cancer cells at the pre-metastatic stage, leading to oxalate accumulation in lung tissue. Lung oxalate accumulation induced neutrophil extracellular trap (NET) formation by activating NADPH oxidase, which facilitated the formation of pre-metastatic niche. In addition, lung oxalate accumulation promoted the proliferation of metastatic cancer cells by activating the MAPK signaling pathway. Pharmacologic inhibition of HAO1 could effectively suppress the lung oxalate accumulation induced by primary cancer, consequently dampening lung metastasis of breast cancer. Breast cancer cells induced HAO1 expression and oxalate accumulation in alveolar epithelial cells by activating TLR3-IRF3 signaling. Collectively, these findings underscore the role of HAO1-mediated oxalate metabolism in cancer-induced lung PMN formation and metastasis. HAO1 could be an appealing therapeutic target for preventing lung metastasis of cancer.