# Unraveling the vascular fate of deformable circulating tumor cells via a hierarchical computational model

## TL;DR

This study presents a hierarchical computational model combining fluid dynamics and cell mechanics to predict how circulating tumor cells of varying deformability interact with blood vessels, influencing metastasis.

## Contribution

It introduces a novel coupled Lattice-Boltzmann and Immersed Boundary Method model to simulate CTC vascular transport and adhesion based on cell deformability.

## Key findings

- Soft CTCs behave like RBCs in large vessels and tend to adhere firmly.
- Rigid CTCs are pushed away from vessel walls in large vessels.
- In small vessels, soft CTCs can rapidly establish firm adhesion.

## Abstract

Distant spreading of primary lesions is modulated by the vascular dynamics of circulating tumor cells (CTCs) and their ability to establish metastatic niches. While the mechanisms regulating CTC homing in specific tissues are yet to be elucidated, it is well documented that CTCs possess different size, biological properties and deformability. A computational model is presented to predict the vascular transport and adhesion of CTCs in whole blood. A Lattice-Boltzmann method, which is employed to solve the Navier-Stokes equation for the plasma flow, is coupled with an Immersed Boundary Method. The vascular dynamics of a CTC is assessed in large and small microcapillaries. The CTC shear modulus k ctc is varied returning CTCs that are stiffer, softer and equally deformable as compared to RBCs. In large microcapillaries, soft CTCs behave similarly to RBCs and move away from the vessel walls; whereas rigid CTCs are pushed laterally by the fast moving RBCs and interact with the vessel walls. Three adhesion behaviors are observed, firm adhesion, rolling and crawling over the vessel walls, depending on the CTC stiffness. On the contrary, in small microcapillaries, rigid CTCs are pushed downstream by a compact train of RBCs and cannot establish any firm interaction with the vessel walls; whereas soft CTCs are squeezed between the vessel wall and the RBC train and rapidly establish firm adhesion. These findings document the relevance of cell deformability in CTC vascular adhesion and provide insights on the mechanisms regulating metastasis formation in different vascular districts.