Figure 1. Pretreatment of Tumor Cells with Platelets Promotes Lung Metastasis by Increasing Tumor Cell Seeding and Inducing an EMT-Like Invasive Phenotype.

(A) Numbers of metastatic foci at the surface of lungs (2 largest lobes) 14 days after tail-vein injection of MC38GFP cells or Ep5 cells stably expressing ZsGreen (Ep5-ZsGreen) pretreated with buffer (vehicle) or platelets for 40h (n=5–12).

(B) Numbers of tumor cells at the surface of lungs 48h after tail-vein injection of MC38GFP or Ep5-ZsGreen cells pretreated with buffer or platelets for 40h (n=6–11).

(C) Phase-contrast micrographs of MC38GFP or Ep5 cells treated with buffer or platelets for the times indicated. Scale bar=50μm.

(D) Relative fold change in mRNA expression in MC38GFP or Ep5 cells treated with buffer or platelets for 40h (n=3). Values are normalized to Gapdh expression.

(E) Detection of E-cadherin protein levels by immunoblotting of lysates of MC38GFP or Ep5 cells treated as in (D). Amounts of platelets equal to those used to treat cells were also loaded as control (no cells). β-tubulin was used as loading control.

(F) Zymography for MMP-9 in the conditioned medium of MC38GFP or Ep5 cells treated as in (D). Amounts of platelets equal to those used to treat cells were also loaded as control (no cells).

(G) MC38GFP and Ep5 cells were added at the top of transwells coated with Matrigel and treated with buffer or platelets. The total number of cells that invaded to the bottom of the transwell was counted after 48h (n=3).

For panels A, B, D and G bars represent the mean ± SEM. *p<0.05, **p<0.01, ***p<0.001 were determined by Student’s t-test.

See also Figure S1.