We found that IFITM1 and PLSCR1 were constitutively overexpressed in AI-resistant MCF-7:5C breast cancer cells and AI-resistant tumors and that siRNA knockdown of IFITM1 significantly inhibited the ability of the resistant cells to proliferate, migrate, and invade.
Tumors from the PLSCR1-transfected cells were greatly reduced in size, showed increased infiltration of leukocytes and macrophages, and appeared to undergo differentiation to a more uniform and spindle-shaped morphology that markedly contrasted the highly undifferentiated and pleiomorphic cell shape normally observed for HEY1B cells in vitro or for vector-transfected control HEY1B cells both in vitro and in vivo.