People rarely die from their primary tumor, rather it is the spread of their tumor to other organs (metastasis) that leads to death, and when that occurs there is a general lack of treatment options. Crosstalk between tumor cells and their associated cellular, physical, and chemical environment is now appreciated to be critical for tumor progression, metastasis, and response to therapy, yet the cellular and molecular basis for these tumor-environment communications is complex and not fully understood. Our lab is interested in understanding how cancers invade and spread throughout the body with the goal to identify and understand molecular pathways important for metastasis and then develop effective and selective ways to prevent the spread of cancer by targeting these pathways. To address this problem we employ aspects of biochemistry, cell biology, developmental biology, biophysics, genetics, and cell and in vivo imaging.
We are interested in understanding the molecular mechanisms regulating epithelia formation and dynamic remodeling during development and adult pathological conditions such as cancer and fibrosis.
(A) Epithelial Mesenchymal Transitions (EMT) – how localized tumors acquire the ability to invade and migrate to give rise to metastases. We are interested in identifying the environmental signals regulating EMT and how they do so within the context of cancer progression.
Discoidin Domain Receptor 2 controls collagen fiber orientation at tumor-stromal boundary.
Second Harmonic (SHG) images of breast tumors. Normal breast tumor (left) and breast tumor lacking DDR2 (right). Yellow line denotes the tumor (lower left) stromal (upper right) boundary. Green lines are collagen fibers < 100 mm of the tumor boundary. Red lines are collagen fibers >100 mm away from the tumor boundary. Perpendicular fibers facilitate invasion; parallel fibers are not optimal for tumor cell invasion
Only mice with SNAIL1 expressing primary breast cancers (left) go on to develop lung metastases. We have generated mice that contain an allele of SNAIL1 that express a SNAIL1 protein fused to bioluminescent clic beetle red (SNAIL1-CBR) under the control of the endogenous SNAIL1 promoter. This allows us to monitor SNAIL1 expression in real time in live animals during cancer development, progression, and metastasis.
(B) The Role of the Rho GTPase family of GTP-binding proteins in formation and remodeling of cell-cell adhesion, epithelia polarity, epithelial cell morphology, and cell migration.
Clonal depletion of Rho1 in the remodeling epithelium of Drosophila pupal eyes increases apical size.
Adherens junctions (DE-cadherin (red)) and basolateral membranes (Coracle (blue)). Epithelial cells with reduced Rho1 expression exhibit increased apical cell size (green stars). When two Rho1 mutant cells are adjacent, apical size increases and adherens junctions are disrupted (white stars). To explain the adherens junction phenotype we have found that Rho regulates both DE-cadherin endocytosis and trafficking from the common recycling endosome to recycling vesicles.
(C) How fibrosis in tumors develops, its biophysical implications for cancer progression and metastasis, and potential avenues for therapeutic intervention.
The Hippo pathway is the major pathway regulating cell and organ growth and mutations in this pathway lead to the development of cancer. We have identified a family of negative regulators of this pathway: The AJUBA LIM protein family. We are trying to understand the biochemical basis for how these proteins work to limit Hippo pathway activity and the in vivo consequence when this regulation is disrupted.
Genetic deletion of drosophila AJUBA (djub) greatly diminishes eye size
Action of AJUBA LIM proteins in regulation of the Hippo signaling pathway
Deletion of dJub in the wing reduces the number of cells per wing and thus wing size
We are interested in understanding how mechanical and physical properties within a tumor regulate tumor cell invasion and spread. This is a collaborative effort with mechanical and chemical engineers and theoretical physicist at both Johns Hopkins University and Washington University. We study the biophysical properties of single cell and collective cell migration in 2D and 3D systems. For example, how do cell-cell interactions affect cell-matrix adhesions, and vice versa, during collective cell migration and throughout the group of moving tumor cells.
Particle Image Velocimetry (PIV). From high-resolution phase contrast movies (A) a vector velocity field is plotted (B). This is 1 for 1 representation of the phase image. Migratory speed is calculated from the magnitude of the vectors C. The radial correlation function is generated by computing the correlation between pairs of vectors as a function of their separation distance (concentric circles show radial distance bins). The vectors with black bases fall a specific distance R away from an example index vector (red). The polar (or directional) correlation is computed as a function of both distance and direction between pairs of vectors (relative to the heading of the index vector). The direction subdivisions for the example index vector are shown by the colored sectors, and the color of each arrow in the example distance bin shows the direction sector to which it belongs. D. Using graph theory based methods to partition the velocity field data; collectively moving groups of cells can be identified. The 15 largest clusters from a single image location within zone A are shown as pseudocolored zones for each cell type.
Tracking the position of fluorescent microspheres embedded in the polyacrylamide gel and computing displacements relative to their unstressed locations measure cell tractions. The left panel is a high magnification sub-region of the bead image (from red box on right) showing stressed (green) and unstressed bead positions. A map of displacements is shown on the right and used to compute traction forces using Fourier Transform Traction Cytometry.