Breast cancer is a heterogeneous disease and stratification of tumors is paramount to achieve better clinical outcomes. While it is common to stratify and treat breast tumors as a single entity, insights from studies on intra-tumoral heterogeneity and cancer stem cells raise the possibility that multiple breast cancer subtypes may co-exist within a tumor. A role for plasticity in driving dynamic conversions between breast cancer subtypes is proposed and the clinical implications would be a need for combinatorial therapeutic strategies that account for the discrete disease entities and their plasticity. Accordingly, the advent of single-cell technologies will be crucial in enabling the diagnosis and stratification of distinct disease subtypes down to the cellular level.

Cancer stem-like cells contribute to tumor heterogeneity and have been implicated in disease relapse and drug resistance. Here we show the co-existence 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 (EMT) 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 and TGFß/Smad pathways, respectively. Further, combining the Stat3 inhibitor Stattic and the Tgfß-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.

Background: Ca 2+ is known to be involved in a number of metastatic processes including motility and proliferation which can result in store-depletion of Ca 2+ . Up regulation of genes which contribute to store operated channel (SOC) activity may plausibly be necessary for these processes to take place efficiently. TRPC proteins constitute a family of conserved Ca 2+ -permeable channels that have been shown to contribute to SOC activity.

Cancer-associated fibroblasts (CAFs) are activated fibroblasts that constitute the major components of tumor microenvironment (TME) and play crucial roles in tumor development and metastasis. Here, we generated fibroblast-specific inducible focal adhesion kinase (FAK) knockout (cKO) mice in a breast cancer model to study potential role and mechanisms of FAK signaling in CAF to promote breast cancer metastasis in vivo. While not affecting primary tumor development and growth, FAK deletion significantly suppressed breast cancer metastasis in vivo. Analyses of CAFs derived from cKO mice as well as human CAFs showed that FAK is required for their activity to promote mammary tumor cell migration. We further showed that FAK ablation in CAFs decreased their exosome amount and functions to promote tumor cell migration and other activities, which could contribute to the reduced metastasis observed in cKO mice. Lastly, profiling of miRs from CAF exosomes showed alterations of several exosomal miRs in FAK-null CAFs, and further analysis suggested that miR-16 and miR-148a enriched in exosomes from FAKnull CAFs contribute to the reduced tumor cell activities and metastasis. Together, these results identify a new role for FAK signaling in CAFs that regulate their intercellular communication with tumor cells to promote breast cancer metastasis.

Autophagy is an evolutionarily conserved cellular process controlled through a set of essential autophagy genes (Atgs). However, there is increasing evidence that most, if not all, Atgs also possess functions independent of their requirement in canonical autophagy, making it difficult to distinguish the contributions of autophagy-dependent or -independent functions of a particular Atg to various biological processes. To distinguish these functions for FIP200 (FAK family-interacting protein of 200 kDa), an Atg in autophagy induction, we examined FIP200 interaction with its autophagy partner, Atg13. We found that residues 582-585 (LQFL) in FIP200 are required for interaction with Atg13, and mutation of these residues to AAAA (designated the FIP200-4A mutant) abolished its canonical autophagy function in vitro. Furthermore, we created a FIP200-4A mutant knock-in mouse model and found that specifically blocking FIP200 interaction with Atg13 abolishes autophagy in vivo, providing direct support for the essential role of the ULK1/Atg13/FIP200/Atg101 complex in the process beyond previous studies relying on the complete knockout of individual components. Analysis of the new mouse model showed that nonautophagic functions of FIP200 are sufficient to fully support embryogenesis by maintaining a protective role in TNFα-induced apoptosis. However, FIP200-mediated canonical autophagy is required to support neonatal survival and tumor cell growth. These studies provide the first genetic evidence linking an Atg's autophagy and nonautophagic functions to different biological processes in vivo.