Figure 1.

EC330 inhibits the LIF/LIF-R signaling and blocks the promoting effects of LIF on growth and migration of cancer cells. (A) Chemical structure of compounds EC330, EC357, EC363, and EC364. (B) Cytotoxicity of EC330, EC357, EC363, and EC364 in MCF7 cells with or without ectopic LIF overexpression. Cells were treated with compounds for 24 h. (C) EC330 binds to hLIF-R in the presence of LIF (blue surface) as predicted by molecular modeling studies. (D) EC330 interacts with LIF-R. Cellular lysates of MCF7-LIF cells were incubated with Avitin-biotin-EC-330 or Control-Avidin beads. The ability of Avitin-biotin-EC330 to bind to LIFR was analyzed by Avidin beads pull-down followed with western blot assays. (E) Ectopic LIF expression increased the levels of p-STAT3^Y705 and p-AKT^S473 in MCF7 and MDA-MB231 cells, which was abolished by treatment of LIF neu Abs (200 ng/ml in MCF7 cells) or EC330 (1 μM) for 2 h. (F) Ectopic LIF expression in MCF7 cells promoted the proliferation of cells (left panel), which was largely abolished by LIF neu Abs (200 ng/ml) and EC330 (5 nM) (middle and right panels). (G) EC330 (1 mg/kg, i.p., 5 times/week for 24 days) preferentially inhibited the growth of xenograft tumors formed by MDA-MB231 cells with ectopic LIF expression (n ≥ 6/group). Left panel: growth curves of xenograft tumors. Right upper panel: relative tumor volume for all xenograft tumors of each group at the end of the experiment. Right lower panels: representative images of xenograft tumors. (H) The levels of p-STAT3 and total STAT3 in MDA-MB231 xenograft tumors. (I) EC330 preferentially inhibits the migration of cancer cells with LIF overexpression. MCF7 and MDA-MB231 cells with or without ectopic LIF expression were treated with EC330 (5 nM for MCF7 and 15 nM for MDA-MB231 cells). The migration abilities of cells were determined by trans-well assays. Data are presented as mean ± SD. ***P < 0.001.