Intracellular Doppler Signatures of Platinum Sensitivity Captured by Biodynamic Profiling in Ovarian Xenografts.

Daniel Merrill,John Turek,Daniela Matei,David Nolte,Hao Sun,Ran An,Bakhtiyor Yakubov

doi:10.1038/srep18821

Abstract

Three-dimensional (3D) tissue cultures are replacing conventional two-dimensional (2D) cultures for applications in cancer drug development. However, direct comparisons of in vitro 3D models relative to in vivo models derived from the same cell lines have not been reported because of the lack of sensitive optical probes that can extract high-content information from deep inside living tissue. Here we report the use of biodynamic imaging (BDI) to measure response to platinum in 3D living tissue. BDI combines low-coherence digital holography with intracellular Doppler spectroscopy to study tumor drug response. Human ovarian cancer cell lines were grown either in vitro as 3D multicellular monoculture spheroids or as xenografts in nude mice. Fragments of xenografts grown in vivo in nude mice from a platinum-sensitive human ovarian cell line showed rapid and dramatic signatures of induced cell death when exposed to platinum ex vivo, while the corresponding 3D multicellular spheroids grown in vitro showed negligible response. The differences in drug response between in vivo and in vitro growth have important implications for predicting chemotherapeutic response using tumor biopsies from patients or patient-derived xenografts.

Highlights

Cytoskeletal forces and to membrane modulation[28]
The same cell lines cultured as spheroids were used to generate intraperitoneal xenografts in nude female mice, and the millimeter-scale tumor explants were used for analysis
The results of BDI for spheroids and xenograft fragments are presented in several modalities, one of which is motility contrast imaging (MCI) shown in Fig. 1e for spheroids

Summary

Introduction

Cytoskeletal forces and to membrane modulation[28]. One of the imaging formats of BDI is called tissue-dynamics spectroscopy (TDS) that provides functional imaging by analyzing fluctuating speckle-intensity time-series into individual ultra-low frequency (ULF) Doppler components. All the constituents of cells are in motion, producing Doppler frequency shifts in the scattered light proportional to the longitudinal speed of the scattering particle ωD = q⋅ v0 , where q is the momentum transfer and v0 is the particle velocity (Fig. 1b). Doppler spectroscopy of intracellular motions is broadband because intracellular motions in 3D are isotropic, and directed motions have finite correlation (or persistence) time t0. These characteristics produce an ensemble of Rayleigh flights (rather than a Wiener process). Distinct physiological processes produce multiple spectra that superpose into a broadband spectrum with multiple knee frequencies ω k (Fig. 1c). Applied therapeutics modify the individual spectra differently, producing distinct fingerprints of the modified physiological effects[30]

Methods

Results

Conclusion