Secretoglobin Family 2A, Member 2 (SCGB2A2) is a 93-amino-acid protein belonging to the secretoglobin superfamily. It is primarily expressed in normal breast and skin tissues and forms a secreted heterodimer with lipophilin B. SCGB2A2 is highly tissue-specific and is overexpressed in 40–80% of human breast cancers, making it a valuable biomarker for breast cancer diagnosis, early metastasis detection, and potential immunotherapy targets. Its low expression in normal mammary epithelium and elevated levels in malignancies highlight its clinical significance. Additionally, SCGB2A2 is conserved across species, including chimpanzees, dogs, and cows, indicating its evolutionary importance.Besides,Prolactin Induced Protein (PIP) has been identified as an interactor of SCGB2A2, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant mouse SCGB2A2 and recombinant human PIP . Briefly, biotin-linked SCGB2A2 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100μl were then transferred to PIP-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50μl stop solution to the wells and read at 450nm immediately. The binding activity of recombinant mouse SCGB2A2 and recombinant human PIP was shown in Figure 1, the EC50?for this effect is 0.021 μg/mL.