Six-week-old control mice and VDR CKO mice were administered tamoxifen (100 mg/kg body weight) via intraperitoneal injection once daily for five consecutive days. After a two-week interval, mice of each genotype were randomly allocated into two groups: the saline group and the BLM group. On day 0, mice in the BLM subgroup received an intratracheal injection of BLM (1 mg/kg), while those in the saline subgroup were given an equivalent volume of saline via intratracheal injection. All mice were euthanized on day 21, and their lungs were harvested for 4D label-free quantitative proteomics analysis.