CLDN6 and breast carcinoma: To further determine the functional roles of the CLDN6/SENP1/HIF-1α axis in breast cancer metastasis, MDA-MB-231 cells carrying the luciferase gene were stably transfected with CLDN6 overexpression, CLDN6/HIF-1α overexpression, CLDN6/SENP1 overexpression and corresponding empty vectors and injected into nude mice.