Dr Samantha Stehbens

Dr Stehbens is a cell biologist with a long-standing interest in understanding the fundamental mechanisms that regulate cell adhesion and the cytoskeleton. She has made key contributions to the fields of quantitative microscopy, cell motility, adhesion and the cytoskeleton with publications spanning multiple fields from ion channels in brain cancer, to growth factor signalling and autophagy. Her research group (joint between AIBN and IMB) aims to understand the fundamental principles of how cells integrate secreted and biomechanical signals from their local microenvironment to facilitate movement and survival. They have uncovered an entirely novel role for the microtubule cytoskeleton in protecting cells from cortical and nuclear rupture during cell migration in 3D cell migration and invasion. Using patient-derived tumour cells, coupled to genetic alteration and substrate microfabrication, they use state-of-the-art microscopy to understand the mechanisms of cell migratory behaviour required for cancer cells to traverse the body during metastasis.

Her graduate work in the laboratory of Alpha Yap (IMB IQ) discovered how the microtubule cytoskeleton regulates cell-cell adhesion. After which she relocated to The University of California San Francisco (UCSF) to work with Prof Wittmann, a microtubule biologist who is an expert in live-cell spinning disc microscopy. Here she worked at the cutting edge of biology imaging advancements as the greater bay area research community combines several of the top-laboratories for imaging technologies. Supported by a competitive American Heart Fellowship Post-Doctoral fellowship, she identified how microtubules coordinate protease secretion during migration to mediate cell-matrix adhesion disassembly. In 2013, she returned to Australia to expand her imaging-based skill set to focus on models of cancer cell biology. Working with Prof. Pamela Pollock (QUT) she uncovered how activating FGFR2 mutations resulted in a loss of cell polarity potentiating migration and invasion in endometrial cancer. Following this, she worked with Prof. Nikolas Haass (UQDI) a melanoma expert, investigating the role of microtubule +TIP proteins in 3D models of metastatic invasion before starting her lab at the Institute for Molecular Bioscience as an ARC Future Fellow.

Lab Overview

Cells in living organisms navigate highly crowded three-dimensional environments, where their coordinated migration provides the driving force behind developmental and homeostatic tissue maintenance. Our research aims to understand the fundamental principles underpinning how cells integrate secreted and biomechanical signals from their local microenvironment to facilitate cell movement and survival. We apply these findings to understand how cancer cells exploit this to metastasise or spread to distal tissues. We hypothesise that targeting the crosstalk between the cytoskeleton and the mechanical micro-environment, can be developed as an anti-metastatic approach.

Cancer cells spread aggressively through tissues by adapting their cell shape to fit the environment in addition to altering their environment so they can squeeze through tight tissue spaces. Cancer cells sense and become more invasive following changes in the biophysical properties their microenvironment including increases in stromal stiffness and interstitial fluid pressures. These changes make cancer cells mechanically compliant and adaptive to fluctuations in their surrounding environment allowing them to alter their shape to fit matrix physical attributes. As such, cells need mechanisms in place to 1) detect these physical limits, 2) deform their cortex whilst producing mechanical force for forward locomotion and 3) orient themselves to move through tissues. We focus on understanding- at the molecular level- how the microtubule cytoskeleton and microtubule associated proteins called +TIPs, regulate how cells move through physically challenging environments. To do this we utilize cutting-edge methodology including microchannel fabrication, novel light sheet microscopy, quantitative imaging methods in combination with patient-derived cell and 3D hydrogel models to recapitulate the 3D microenvironment.

Our research areas include:

• Cytoskeleton
• Cell adhesion
• Cell migration
• Cell mechanics
• Cancer cell biology

Areas of Expertise

Microtubules and Cell-Cell Adhesion

My early research, in the laboratory of Professor Alpha Yap, focused on understanding how the microtubule cytoskeleton regulates E-cadherin-based cell-cell adhesion. This work was the first to discover that it was the dynamacity, not simply the tethering, of the microtubule cytoskeleton that was critical for E-cadherin accumulation and junctional reinforcement. This was in addition to defining a previously unappreciated role for the cytokinetic machinery (Ect2) in regulating cell-cell adhesion

• Stehbens, S.J., …,and Yap, A. S. (2006). Dynamic Microtubules Regulate the Local Concentration of E-cadherin at Cell-Cell Contacts. Journal of Cell Science 119: 1801-1811
• Ratheesh, A., … Stehbens, S.J., and Yap, A.S. (2012). Centralspindlin and α-catenin regulate Rho signalling at the epithelial zonula adherens. Nature Cell Biology 14(8): 818-28

Microtubules and Cell-Matrix Adhesion

Following my PhD, I relocated to the University of California San Francisco to work with Professor Torsten Wittmann, an expert in live-cell spinning disc microscopy and microtubule functions during cell motility. This work was dogma changing and established how the microtubule interacting protein, CLASP, facilitates targeted protease secretion at focal adhesions during epithelial sheet migration to mediate cell-matrix adhesion disassembly, from the inside-out. It includes the first observation of live, directed exocytosis of the matrix protease MT1MMP at focal adhesions. Our work pioneered the combined application of quantitative live-cell protein dynamics and the application of the novel super resolution imaging technique, SAIM (Scanning Angle Interference Microscopy). During my time at UCSF I learnt how to custom design live-cell microscopes with these live-cell imaging platforms now commercially distributed as the Spectral Diskovery and Andor Dragonfly.

• Stehbens, S.J., … and Wittmann., T (2014). CLASPs link focal-adhesion-associated microtubule capture to localized exocytosis and adhesion site turnover. Nature Cell Biology 16(6): 558-570
• Stehbens, S.J., and Witmann, T. (2014) Analysis of focal adhesion turnover: a quantitative live-cell imaging example. Methods in Cell Biology 123: 335-46
• Stehbens, S.J., and Witmann, T. (2012) Targeting and transport: how microtubules control focal adhesion dynamics. Journal of Cell Biology 20, 198(4): 481-9

Cell Morphology and Cancer Biology

In 2013 I returned to Australia, joining the lab of Pamela Pollock with focus on applying my skill set to have translational impact. Here I described the impact of activating FGFR2b-mutations on endometrial cancer progession. These findings uncovered collective cell polarity and invasion as common targets of disease-associated FGFR2 mutations that lead to shorter survival in endometrial cancer patients.

Stehbens, S.J, Ju, R.J and Pollock P.M. (2018) FGFR2b activating mutations disrupt cell polarity to potentiate migration and invasion in endometrial cancer. Journal of Cell Science, 131(15)

Microtubules in Metastatic Plasticity

In 2017, I joined the Experimental Melanoma Group at UQDI, where I work together with Professor Nikolas Haass in applying innovative live-cell spinning disc confocal imaging and biosensor approaches to understand cell-cell and cell-matrix interactions of melanoma with its microenvironment. Our work explores the adaptive role that the microtubule cytoskeleton plays in facilitating cell shape plasticity, matrix remodelling and resistance to compression during migration in complex 3D matrix models of metastatic melanoma invasion. We are fundamentally interested in understanding the reciprocal biophysical relationship between the microtubule cytoskeleton and the microenvironment during melanoma invasion, with the aim to expand our findings to other metastatic cancers.

Ju, Robert J., Stehbens, Samantha J., Haass, Nikolas K. 2018, 'The Role of Melanoma Cell-Stroma Interaction in Cell Motility, Invasion, and Metastasis', Frontiers in Medicine, vol. 5