Abstract 3345: Induction of apoptosis by high levels of oscillatory shear strain: proof of concept in a human colon cancer metastasis cell line.

Abstract

Abstract Purpose / Introduction: Mechanotransduction is a biological process enabling cells to convert mechanical cues into biological responses[1]. The apoptotic status of many cell types is regulated by the mechanical conditions of their environment [2,3]. In this context, and due to the incompressible nature of tissues, it is theoretically thinkable to selectively induce cellular death by the controlled application of low frequency oscillatory shear strain. Unlike e.g. HIFU (high intensity focused ultrasounds), here the energy deposited would by far not be sufficient to mechanically rupture cells, but would instead trigger specific signals within the cell. We establish the proof of concept for this proclaimed effect in a cell line of colon cancer metastasis. Subjects and Methods: DHDK12 colon cancer metastasis cells were grown in conventional conditions. At confluency, one plate was subjected for 4 hrs to a 90Hz uniaxial sinusoidal motion parallel to the cell layer by a rigidly linked modal exciter. One control plate was left without any vibration. The strain levels induced in the cell monolayer were measured on a control plate loaded with a thin layer of agarose gel (2g/l) and covered with liquid to simulate the medium. Shear strain images were obtained on a 7T MRI system using a spin echo elastography sequence synchronized with a 90Hz vibration of the imaged plate (TE/TR = 39/1744 ms) with 4 wave offsets, 3 encoding directions and a 300 μm isotropic resolution. Strain was evaluated as the maximum shear strain (difference between maximum and minimum eigenvalues of the strain tensor). At the end of the experiment, cells were, colored with trypan blue and the proportion of colored vs. uncolored cells was estimated using a hematocytometer. Levels of caspase-3 were assessed by western blotting, using β-actin as the loading marker. Results: Using shear strain imagin, it was determined that the setup yielded very elevated maximum shear strains on the order of 5.5 ± 1.1 % in the first 300μm immediately above the plastic surface. Vibrations were sufficient to induce cell death, as observed by the 4.2X increase in the count of dead cells after vibrations (pre: 2.9±1.5%, post: 4.5±1.4% for the control plate, vs. pre: 5.3±2.6%, post: 22.3±3.9 % for the vibrated plate). Caspase-3 levels were elevated in the cells having undergone vibrations, indicating that an activation of the apoptosis pathway was involved in the observed increase in cell deaths. Discussion/Conclusion: We show that the application of 5% maximum shear strain at 90Hz for 4 hours has the ability to induce apoptosis in vitro on a human cell line of cancer metastasis. This proof of concept indicates that the selective application of high strain shear waves of low frequency may become a viable alternative for tumor therapy. [1] Ingber, FASEB 2006 20(7) [2] Jaalouk, Nat Rev Mol Cell Biol, 2009 10(1) [3] Cheng, PLOS One, 2009 4(2) Citation Format: Philippe Garteiser, Sabrina Doblas, Simon Lambert, Mouniya Mebarki, Valerie Vilgrain, Bernard E. Van Beers, Valerie Paradis, Ralph Sinkus. Induction of apoptosis by high levels of oscillatory shear strain: proof of concept in a human colon cancer metastasis cell line. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3345. doi:10.1158/1538-7445.AM2013-3345