Gr1+ myeloid cells are a patrolling subpopulation of the tumor-infiltrating myeloid cells. Gr1+/c-fms+ myeloid cells (red/green) patrol in tumor vasculature (yellow) in the tumor-stroma border area while c-fms+/dextran+ macrophages (green/yellow) do not migrate in the same area. Gr1+ cells were labeled with Alexa-Fluor-647-conjugated anti-Gr1 antibodies (red), which were coinjected, i.v., with 70 kD rhodamine-conjugated dextran (yellow) in an MMTV-PyMT;ACTB-ECFP;c-fms-EGFP mouse.Dextran first labeled the blood vessels and was taken up by macrophages over time. Shown are the ECFP (blue, mostly epithelial cells), EGFP (green, myeloid cells), rhodamine (yellow, dextran) and Alexa-Fluor-647 (red, Gr1+ antibodies) channels. The movie is shown first with and then without the dextran channel. Time indicates time after injection of antibody and dextran. From Egeblad et al. (2008) Dis. Model. Mech., 1 155-167.

CD11c+ dendritic-like cells migrate at the tumor-stroma border. CD11c+ cells (green), expressing EGFP on their membranes as a fusion protein with the diphtheria toxin receptor (DTR), are seen migrating along the epithelium (blue) at the tumor-stroma border in an MMTV-PyMT;ACTB-ECFP;CD11c-DTR-EGFP mouse. From Egeblad et al. (2008) Dis. Model. Mech., 1 155-167.

Infiltration and migration of c-fms+ myeloid cells in the tumor microenvironment. c-fms+ myeloid cells migrate at the border of a late carcinoma, whereas migration within the tumor mass mostly occurs along blood vessels and in stromal patches. c-fms+ cells (green) are seen migrating at the border of the carcinoma (blue) in the bottom of the field, along c-fms+-dense tracks that penetrate into the tumor mass and along blood vessels inside the mass in an MMTV-PyMT;ACTB-ECFP;c-fms-EGFP mouse. Few of the c-fms+ cells that have infiltrated the carcinoma mass migrate. c-fms+ cells are also seen flowing through blood vessels inside the lesion (black areas on the surrounding background of blue cancer cells). From Egeblad et al. (2008) Dis. Model. Mech., 1 155-167.