Gene expression of spheres made from mammary tumors of FRS2b hetero mice and knock-out mice

Precancerous tissue microenvironment is thought to be important for tumorigenesis when cancer stem-like cells (CSCs) begin to grow, though underlying mechanisms remain unclear. Here, we uncovered critical roles of luminal progenitor cells expressing FRS2β, an inhibitory adaptor for ErbB signaling, to create the cytokines-rich CSC niche in mammary tissues. Deficiency of FRS2β greatly decreased mammary tumorigenesis with decreased tumor stroma in mouse mammary tumor virus (MMTV)-ErbB2 mice. Moreover, FRS2β-deficient precancerous mammary tissues did not allow tumorigenesis derived from xenografted wild type FRS2β tumor cells. Insulin-like growth factor (IGF) 1 and CXC chemokine ligand (CXCL) 12, stemness- and stroma-inducing cytokines, respectively, were expressed at low levels in FRS2β-deficient precancerous mammary cells. Treatment with inhibitors against these cytokines in precancerous mice greatly decreased tumorigenic potential. In addition, human breast cancer tissues in which FRS2β is highly expressed in tumor cells harbor more stroma, and are associated with poor prognosis. Thus, cytokines-rich CSC niche and tumor microenvironment induced by FRS2β expressed in luminal progenitor cells and tumor cells play important roles for tumorigenesis. Comparison of expression between spheres made from mammary tumors of FRS2beta hetero and knock-out mice. We conducted three replicates.