MKI67 and cancer: Immunoreactivity of the proliferative marker Ki-67 was detected in the nuclei of cancer cells in all the tumors; however, the KI was significantly lower in the A375/OVOS2–shRNA group than that in the A375 and A375/NC–shRNA groups (P = 0.001 and P < 0.001, compared with A375/NC-shRNA and untreated A375 cell groups, respectively; Fig 6E).