No abstract

Vasculogenic mimicry (VM), a newly defined pattern of tumor microvascularization differs from angiogenesis and vasculogenesis in its noninvolvement of endothelial cells, by which highly aggressive tumor cells can form vessel-like structures themselves, because of their high plasticity. The presence of VM has been shown to be strongly associated with a poor prognosis in several types of cancer, but biological features of tumor cells that form VM remains unknown. Human breast cancer, characterized by a group of highly heterogeneous lesions, is the most common cancer in women and one of the leading causes of cancer-related deaths worldwide. The epithelialmesenchymal transition (EMT) state in breast cancer has been associated with cancer stem cell (CSC) properties, self-renewal capabilities, resistance to conventional therapies, and a tendency for posttreatment recurrence. With increasing knowledge about cancer stem cell phenotypes and functions, they are implicated in VM formation. Studies also indicate that EMT is relevant to the acquisition and maintenance of stem cell-like characteristics and is involved in VM. This review discusses the correlation between CSCs, EMT, and VM formation with a focus on breast cancer. Also, the signalling molecules and pathways involved in VM and some recently defined direct VM targeting strategies in breast cancer are reviewed here.

Up to 41% of hepatocellular carcinomas (HCCs) result from activating mutations in the CTNNB1 gene encoding β-catenin. HCC-associated CTNNB1 mutations stabilize the β-catenin protein, leading to nuclear and/or cytoplasmic localization of β-catenin and downstream activation of Wnt target genes. In patient HCC samples, β-catenin nuclear and cytoplasmic localization are typically patchy, even among HCC with highly active CTNNB1 mutations. The functional and clinical relevance of this heterogeneity in β-catenin activation are not well understood. To define mechanisms of β-catenin-driven HCC initiation, we generated a Cre-lox system that enabled switching on activated β-catenin in (1) a small number of hepatocytes in early development; or (2) the majority of hepatocytes in later development or adulthood. We discovered that switching on activated β-catenin in a subset of larval hepatocytes was sufficient to drive HCC initiation. To determine the role of Wnt/β-catenin signaling heterogeneity later in hepatocarcinogenesis, we performed RNA-seq analysis of zebrafish β-catenin-driven HCC. At the single-cell level, 2.9% to 15.2% of hepatocytes from zebrafish β-catenin-driven HCC expressed two or more of the Wnt target genes axin2, mtor, glula, myca and wif1, indicating focal activation of Wnt signaling in established tumors. Thus, heterogeneous β-catenin activation drives HCC initiation and persists throughout hepatocarcinogenesis.

EMT is the process by which epithelial cells, characterized by well-developed intercellular contacts, transdifferentiate into motile and invasive mesenchymal cells. This process is associated with the loss of transmembrane intercellular adhesion molecule E-cadherin and disruption of cell-cell junctions along with acquisition of migratory properties. EMT is integral in embryonic development, wound healing, and stem cell behavior; however, its aberrant activation by micro-environmental alterations and abnormal stimuli can lead to cancer progression. Here, we review the different molecular changes associated with EMT that are responsible for downregulation of epithelial genes. Increased knowledge of the EMT process is essential for therapeutic targeting of cancer cells.