In conclusion, the results from this study suggest that P4 increased the complex formation of PR-cSrc-SHP2, which increased the binding between SHP2 and caveolin-1, subsequently reducing complex formation of cSrc-Csk and cSrc-p140Cap, leading to decreased phosphorylation of cSrc527 and prolonged cSrc activation, and eventually promoted breast cancer cell proliferation and migration. Here, CSK is linked to breast cancer.