Gating strategy for analysis and isolation of CSC populations (S1); Tumors that arise from transplanted sorted populations recapitulate features of parental tumors (S2); Tumors that arise from transplanted sorted populations display Stat3 and Smad2 activation (S3); Inhibition of autophagy after FIP200 deletion (S4).
ARTICLE ABSTRACTCancer stem-like cells contribute to tumor heterogeneity and have been implicated in disease relapse and drug resistance. Here we show the coexistence of distinct breast cancer stem-like cells (BCSC) as identified by ALDH+ and CD29hiCD61+ markers, respectively, in murine models of breast cancer. While both BCSC exhibit enhanced tumor-initiating potential, CD29hiCD61+ BCSC displayed increased invasive abilities and higher expression of epithelial-to-mesenchymal transition and mammary stem cell–associated genes, whereas ALDH+ BCSC were more closely associated with luminal progenitors. Attenuating the autophagy regulator FIP200 diminished the tumor-initiating properties of both ALDH+ and CD29hiCD61+ BCSC, as achieved by impairing either the Stat3 or TGFβ/Smad pathways, respectively. Furthermore, combining the Stat3 inhibitor Stattic and the Tgfβ-R1 inhibitor LY-2157299 inhibited the formation of both epithelial and mesenchymal BCSC colonies. In vivo, this combination treatment was sufficient to limit tumor growth and reduce BCSC number. Overall, our findings reveal a differential dependence of heterogeneous BCSC populations on divergent signaling pathways, with implications on how to tailor drug combinations to improve therapeutic efficacy. Cancer Res; 76(11); 3397–410. ©2016 AACR.