Leveraging Optical Anisotropy of the Morpho Butterfly Wing for Quantitative, Stain-Free, and Contact-Free Assessment of Biological Tissue Microstructures.

Changes in the density and organization of fibrous biological tissues often accompany the progression of serious diseases ranging from fibrosis to neurodegenerative diseases, heart disease and cancer. However, challenges in cost, complexity, or precision faced by existing imaging methodologies pose barriers to elucidating the role of tissue microstructure in disease. Here, we leverage the intrinsic optical anisotropy of the Morpho butterfly wing and introduce Morpho-Enhanced Polarized Light Microscopy (MorE-PoL), a stain- and contact-free imaging platform which enhances and quantifies the birefringent material properties of fibrous biological tissues. We develop a mathematical model, based on Jones calculus, which quantifies fibrous tissue density and organization. As a representative example, we analyze collagen-dense and collagen-sparse human breast cancer tissue sections and leverage our technique to assess the microstructural properties of distinct regions of interest. We compare our results with conventional Hematoxylin and Eosin (H&E) staining procedures and second harmonic generation (SHG) microscopy for fibrillar collagen detection. Our findings demonstrate that our MorE-PoL technique provides a robust, quantitative, and accessible route toward analyzing biological tissue microstructures, with great potential for application to a broad range of biological materials.

Update on Epithelial-Mesenchymal Plasticity in Cancer Progression.

Epithelial-mesenchymal transition (EMT) is a cellular process by which epithelial cells lose their characteristics and acquire mesenchymal traits to promote cell movement. This program is aberrantly activated in human cancers and endows tumor cells with increased abilities in tumor initiation, cell migration, invasion, metastasis, and therapy resistance. The EMT program in tumors is rarely binary and often leads to a series of gradual or intermediate epithelial-mesenchymal states. Functionally, epithelial-mesenchymal plasticity (EMP) improves the fitness of cancer cells during tumor progression and in response to therapies. Here, we discuss the most recent advances in our understanding of the diverse roles of EMP in tumor initiation, progression, metastasis, and therapy resistance and address major clinical challenges due to EMP-driven phenotypic heterogeneity in cancer. Uncovering novel molecular markers and key regulators of EMP in cancer will aid the development of new therapeutic strategies to prevent cancer recurrence and overcome therapy resistance.

Glutamine-Directed Migration of Cancer-Activated Fibroblasts Facilitates Epithelial Tumor Invasion.

Tumors are complex tissues composed of transformed epithelial cells as well as cancer-activated fibroblasts (CAF) that facilitate epithelial tumor cell invasion. We show here that CAFs and other mesenchymal cells rely much more on glutamine than epithelial tumor cells; consequently, they are more sensitive to inhibition of glutaminase. Glutamine dependence drove CAF migration toward this amino acid when cultured in low glutamine conditions. CAFs also invaded a Matrigel matrix following a glutamine concentration gradient and enhanced the invasion of tumor cells when both cells were cocultured. Accordingly, glutamine directed invasion of xenografted tumors in immunocompromised mice. Stimulation of glutamine-driven epithelial tumor invasion by fibroblasts required previous CAF activation, which involved the TGFß/Snail1 signaling axis. CAFs moving toward Gln presented a polarized Akt2 distribution that was modulated by the Gln-dependent activity of TRAF6 and p62 in the migrating front, and depletion of these proteins prevented Akt2 polarization and Gln-driven CAF invasion. Our results demonstrate that glutamine deprivation promotes CAF migration and invasion, which in turn facilitates the movement of tumor epithelial cells toward nutrient-rich territories. These results provide a novel molecular mechanism for how metabolic stress enhances invasion and metastasis. SIGNIFICANCE: Cancer-associated fibroblasts migrate and invade toward free glutamine and facilitate invasion of tumor epithelial cells, accounting for their movement away from the hostile conditions of the tumor towards nutrient-rich adjacent tissues. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/2/438/F1.large.jpg.

Snail1-Dependent Activation of Cancer-Associated Fibroblast Controls Epithelial Tumor Cell Invasion and Metastasis.

Snail1 transcriptional factor is essential for triggering epithelial-to-mesenchymal transition (EMT) and inducing tumor cell invasion. We report here an EMT-independent action of Snail1 on tumor invasion, as it is required for the activation of cancer-associated fibroblasts (CAF). Snail1 expression in fibroblasts requires signals derived from tumor cells, such as TGFß; reciprocally, in fibroblasts, Snail1 organizes a complex program that stimulates invasion of epithelial cells independent of the expression of Snail1 in these cells. Epithelial cell invasion is stimulated by the secretion by fibroblast of diffusible signaling molecules, such as prostaglandin E2 The capability of human or murine CAFs to promote tumor invasion is dependent on Snail1 expression. Inducible Snail1 depletion in mice decreases the invasion of breast tumors; moreover, epithelial tumor cells coxenografted with Snail1-depleted fibroblasts originated tumors with lower invasion than those transplanted with control fibroblasts. Therefore, these results demonstrate that the role of Snail1 in tumor invasion is not limited to EMT, but it is also dependent on its activity in stromal fibroblasts, where it orchestrates the cross-talk with epithelial tumor cells. Cancer Res; 76(21); 6205-17. ©2016 AACR.