MDK and ovarian cancer: In particular, the panel contains CA125 and HE4, as well as 90 other cancer-related protein markers, including several that have been linked to ovarian cancer, such as ERBB2 [25, 26], ERBB3 [27], ERBB4 [28], vascular endothelial growth factor receptor (VEGFR) 2 [29], midkine [30–33], kallikrein 6 [34], kallikrein 11 [35], folate receptor-alpha [36], interleukin-6 [37–40], and transforming growth factor-alpha [41].