[Paper Review] The morphodynamics of 3D migrating cancer cells

Christopher Eddy, Xinyao Wang+2 more|arXiv (Cornell University)|Jul 27, 2018

Cellular Mechanics and Interactions3 citations

TL;DR

This study reveals that 3D migrating MDA-MB-231 cancer cells exhibit dynamic morphological fluctuations—termed morphodynamics—regulated by extracellular matrix (ECM) mechanics and Rho-signaling, which drive phenotype transitions between distinct migration modes. Using machine learning to classify five morphological phenotypes, the authors show that these transitions enhance invasive potential by enabling cells to search for and commit to more motile phenotypes, positioning morphodynamics as a key biomarker for cancer cell motility and metastasis.

ABSTRACT

Cell shape is an important biomarker that is directly linked to cell function. However, cell morphodynamics, namely the temporal fluctuation of cell shape is much less understood. We study the morphodynamics of MDA-MB-231 cells in type I collagen extracellular matrix (ECM). We find ECM mechanics, as tuned by collagen concentration, controls the morphodynamics but not the static cell morphology. We employ machine learning to classify cell shape into five different morphological phenotypes corresponding to different migration modes. As a result, cell morphodynamics is mapped into temporal evolution of morphological phenotypes. We systematically characterize the phenotype evolutions including occurrence probability, dwell time, transition flux, and 3D migrational characteristics. We find that manipulating Rho-signaling enhances the morphodynamics and phenotype transitions. Using a tumor organoid model, we show that the distinct invasion potentials of each phenotype modulate the phenotype homeostasis. Overall invasion of a tumor organoid is facilitated by individual cells searching for and committing to phenotypes of higher invasive potential. In conclusion, we show that 3D migrating cancer cells exhibit rich morphodynamics that is regulated by ECM mechanics, Rho-signaling, and is closely related with cell motility. Our results pave the way to the systematic characterization and functional understanding of cell morphodynamics as a new biomarker for normal and malignant cells.

Motivation & Objective

• To investigate how extracellular matrix (ECM) mechanics influence the temporal dynamics of cell shape (morphodynamics) in 3D migrating cancer cells.
• To classify dynamic cell shapes into distinct morphological phenotypes corresponding to different migration programs using machine learning.
• To determine how morphological phenotype transitions affect 3D motility and invasive potential in tumor organoids.
• To examine the role of Rho-signaling in regulating morphodynamic fluctuations and phenotype stability.
• To establish morphodynamics as a functional biomarker for cancer cell motility and metastatic potential in 3D environments.

Proposed method

• Time-lapse fluorescence microscopy of MDA-MB-231 cells in 3D type I collagen matrices at varying collagen concentrations (1.0–2.0 mg/mL).
• Cell segmentation and geometric feature extraction (area, perimeter, aspect ratio, solidity, form factor) to quantify cell shape at each time point.
• Machine learning-based classification of cell shapes into five morphological phenotypes: filopodial, lamellipodial, lobopodial, small blebbing, and hemispherical blebbing.
• Quantitative analysis of phenotype dynamics: occurrence probability, dwell time, transition flux, and 3D migrational characteristics (persistence, diffusivity).
• Pharmacological perturbation of Rho-signaling using ROCK inhibitor Y-27632 to assess its impact on morphodynamic behavior.
• Tumor organoid invasion assay to correlate phenotype composition of disseminated cells with invasive potential.

Experimental results

Research questions

• RQ1 How does ECM stiffness, tuned by collagen concentration, regulate the morphodynamics of 3D migrating MDA-MB-231 cells?
• RQ2 Which morphological phenotypes correspond to distinct migration programs, and how do their transition dynamics influence 3D motility?
• RQ3 How does Rho-signaling modulation affect the stability and dynamics of morphological phenotypes in 3D environments?
• RQ4 To what extent do phenotype transitions contribute to the invasive potential of cancer cells in a 3D tumor organoid model?
• RQ5 Can morphodynamics serve as a functional biomarker for cancer cell motility and metastatic behavior?

Key findings

• ECM mechanics, modulated by collagen concentration, significantly regulate morphodynamics but do not alter the ensemble distribution of static cell shapes.
• Cells exhibit rapid, dynamic shape fluctuations, sampling multiple morphological phenotypes over time, with transition rates increasing at higher collagen concentrations.
• The filopodial phenotype shows the highest persistence (0.77 μm/s) and diffusivity (0.48 μm²/s) at 1.5 mg/mL collagen, indicating optimal motility under intermediate stiffness.
• Rho-signaling perturbation via Y-27632 enhances morphodynamic activity, increasing shape fluctuation and transition rates between phenotypes.
• In tumor organoids, disseminating cells are predominantly composed of highly invasive phenotypes—especially filopodial and lamellipodial—indicating phenotype selection during invasion.
• Phenotype homeostasis shifts with ECM stiffness: at 2.0 mg/mL collagen, blebbing phenotypes dominate (60% occurrence), while at 1.0 mg/mL, mesenchymal phenotypes are more stable, highlighting context-dependent phenotype dynamics.