OPN was identified as the proinflammatory cytokine that contributed to calcium deposition in HK-2 cells treated with calcium oxymonohydrate and in a mouse model of renal calculi, and further study found that inhibition of the liver X receptor upregulated OPN to promote the initiation of nephrolithiasis (Chen et al., 2019). The gene discussed is SPP1; the disease is nephrolithiasis.