1. Medical Research Center, Changsha Central Hospital, University of South China, Changsha, Hunan 410004, P.R. China
2. Department of Oncology, Third Xiangya Hospital, Central South University, Changsha, Hunan 410013, P.R. China
3. Reproductive Medicine Center, Foshan Maternal and Child Health Care Hospital, Southern Medical University, Foshan, Guangdong 528000, P.R. China