title: Implications of the Hybrid Epithelial/Mesenchymal Phenotype in Metastasis.
abstract: Transitions between epithelial and mesenchymal phenotypes - the epithelial to -mesenchymal transition (EMT) and its reverse the mesenchymal to epithelial transition (MET) - are hallmarks of cancer metastasis. While transitioning between the epithelial and mesenchymal phenotypes, cells can also attain a hybrid epithelial/mesenchymal (E/M) (i.e., partial or intermediate EMT) phenotype. Cells in this phenotype have mixed epithelial (e.g., adhesion) and mesenchymal (e.g., migration) properties, thereby allowing them to move collectively as clusters. If these clusters reach the bloodstream intact, they can give rise to clusters of circulating tumor cells (CTCs), as have often been seen experimentally. Here, we review the operating principles of the core regulatory network for EMT/MET that acts as a "three-way" switch giving rise to three distinct phenotypes - E, M and hybrid E/M - and present a theoretical framework that can elucidate the role of many other players in regulating epithelial plasticity. Furthermore, we highlight recent studies on partial EMT and its association with drug resistance and tumor-initiating potential; and discuss how cell-cell communication between cells in a partial EMT phenotype can enable the formation of clusters of CTCs. These clusters can be more apoptosis-resistant and have more tumor-initiating potential than singly moving CTCs with a wholly mesenchymal (complete EMT) phenotype. Also, more such clusters can be formed under inflammatory conditions that are often generated by various therapies. Finally, we discuss the multiple advantages that the partial EMT or hybrid E/M phenotype have as compared to a complete EMT phenotype and argue that these collectively migrating cells are the primary "bad actors" of metastasis.
authors.affiliation: Center for Theoretical Biological Physics, Rice University , Houston, TX , USA ; Department of Bioengineering, Rice University , Houston, TX , USA.
authors.forename: Mohit Kumar
authors.initials: MK
authors.lastname: Jolly
authors.affiliation: Center for Theoretical Biological Physics, Rice University , Houston, TX , USA ; Institute of Physics, University of São Paulo , São Paulo , Brazil.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Boareto
authors.affiliation: Center for Theoretical Biological Physics, Rice University , Houston, TX , USA ; Department of Chemistry, Rice University , Houston, TX , USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Huang
authors.affiliation: Center for Theoretical Biological Physics, Rice University , Houston, TX , USA ; Graduate Program in Systems, Synthetic and Physical Biology, Rice University , Houston, TX , USA.
authors.forename: Dongya
authors.initials: D
authors.lastname: Jia
authors.affiliation: Center for Theoretical Biological Physics, Rice University , Houston, TX , USA.
authors.forename: Mingyang
authors.initials: M
authors.lastname: Lu
authors.affiliation: Center for Theoretical Biological Physics, Rice University , Houston, TX , USA ; School of Physics and Astronomy, and The Sagol School of Neuroscience, Tel-Aviv University , Tel-Aviv , Israel ; Department of Biosciences, Rice University , Houston, TX , USA.
authors.forename: Eshel
authors.initials: E
authors.lastname: Ben-Jacob
authors.affiliation: Center for Theoretical Biological Physics, Rice University , Houston, TX , USA ; Department of Chemistry, Rice University , Houston, TX , USA ; Department of Physics and Astronomy, Rice University , Houston, TX , USA ; Department of Biosciences, Rice University , Houston, TX , USA.
authors.forename: José N
authors.initials: JN
authors.lastname: Onuchic
authors.affiliation: Center for Theoretical Biological Physics, Rice University , Houston, TX , USA ; Department of Bioengineering, Rice University , Houston, TX , USA ; Department of Physics and Astronomy, Rice University , Houston, TX , USA ; Department of Biosciences, Rice University , Houston, TX , USA.
authors.forename: Herbert
authors.initials: H
authors.lastname: Levine
keywords: cancer stem cells; cancer systems biology; cell-fate decisions; intermediate EMT; partial EMT