Search

Background: Histological examinations of MMTV-Wnt1 tumors reveal drastic differences in the tumor vasculature whenqcompared to MMTV-Her2 tumors. However, these differences have not been formally described, nor have any angiogenicqfactors been implicated to be involved in the Wnt1 tumors. Methodology/Principal Findings: Here, we show that MMTV-Wnt1 tumors were more vascularized than MMTV-Her2qtumors, and this correlated with significantly higher expression of a CXC chemokine, stromal cell-derived factor-1 (SDF1/qCXCL12) but not with VEGFA. Isolation of various cell types from Wnt1 tumors revealed that SDF1 was produced by bothqtumor myoepithelial cells and stromal cells, whereas Her2 tumors lacked myoepithelial cells and contained significantly lessqstroma. The growth of Wnt1 tumors, but not Her2 tumors, was inhibited by a neutralizing antibody to SDF1, but not byqneutralization of VEGFA. Anti-SDF1 treatment decreased the proportion of infiltrating Gr1+ myeloid cells in the Wnt1 tumors,qwhich correlated with a decrease in the percentage of endothelial cells. The involvement of Gr1+ cells was evident from theqretardation of Wnt1 tumor growth following in vivo depletion of these cells with an anti-Gr1-specific antibody. This degreeqof inhibition on Wnt1 tumor growth was comparable, but not additive, to the effect observed with anti-SDF1, indicative ofqoverlapping mechanisms of inhibition. In contrast, Her2 tumors were not affected by the depletion of Gr1+ cells. Conclusions/Significance: We demonstrated that SDF1 is important for Wnt1, but not for HER2, in inducing murineqmammary tumor and the role of SDF1 in tumorigenesis involves Gr1+ myeloid cells to facilitate growth and/or angiogenesis. [ABSTRACT FROM AUTHOR]