Cancer cell migration within 3D layer-by-layer microfabricated photocrosslinked PEG scaffolds with tunable stiffness

Abstract

Our current understanding of 3-dimensional (3D) cell migration is primarily based on results from fibrous scaffolds with randomly organized internal architecture. Manipulations that change the stiffness of these 3D scaffolds often alter other matrix parameters that can modulate cell motility independently or synergistically, making observations less predictive of how cells behave when migrating in 3D. In order to decouple microstructural influences and stiffness effects, we have designed and fabricated 3D polyethylene glycol (PEG) scaffolds that permit orthogonal tuning of both elastic moduli and microstructure. Scaffolds with log-pile architectures were used to compare the 3D migration properties of normal breast epithelial cells (HMLE) and Twist-transformed cells (HMLET). Our results indicate that the nature of cell migration is significantly impacted by the ability of cells to migrate in the third dimension. 2D ECM-coated PEG substrates revealed no statistically significant difference in cell migration between HMLE and HMLET cells among substrates of different stiffness. However, when cells were allowed to move along the third dimension, substantial differences were observed for cell displacement, velocity and path straightness parameters. Furthermore, these differences were sensitive to both substrate stiffness and the presence of the Twist oncogene. Importantly, these 3D modes of migration provide insight into the potential for oncogene-transformed cells to migrate within and colonize tissues of varying stiffness.

Bioprinting for cancer research

“…Bioprinting can be used to generate precise biocompatible scaffolds for culturing cells with controllable structural features and composition. Digital micromirror device-based projection printing has been used to fabricate 3D polyethylene glycol (PEG) scaffolds with log-pile microarchitecture ( Figure 2B-F) [52]. The elastic modulus of the scaffold was controlled by varying the PEG concentration without altering the structural or mechanical properties, allowing the effects of stiffness to be isolated and examined.…”

Cell type-specific adaptation of cellular and nuclear volume in micro-engineered 3D environments

“…To better understand cell behavior in 3D environments, reductionist approaches are needed to correlate cellular responses to particular chemical and physical properties of the 3D substrate. To this end, a number of artificial 3D systems, including micro-carriers [28,29], synthetic hydrogels [30,31], and micro-well arrays [5][6][7] have been established. These systems offer reproducible biochemical conditions and some of them can even mimic ECM porosity, but they frequently lack the architectural, mechanical, and biochemical versatility necessary for comprehensive cell-biological studies.…”

The need for complex 3D culture models to unravel novel pathways and identify accurate biomarkers in breast cancer

“…As mentioned above, the BM is generally lost in invasive breast cancers, and given that these cells are unable to form an endogenous BM due to destruction by MMPs [51], tumors in vivo are surrounded by different ECM/ECM-peptides; for the study of breast cancer cells, lrECM therefore may not be entirely reflective. In addition, we know that ECM stiffness is an important regulator of the cellular response, and that tumors are stiffer than normal tissue [52–55](Fig. 3).…”

“…For the study of breast cancer, (A) Conventional monolayer cell cultures [120,121,146]; (B) Spheroid cultures, where cells spontaneously aggregate either growing in low attachment plates (left) or hanging drops (right) [80,118,138,147]; (C) 3D lrECM cultures, where cells are either embedded (left) or growing on top of the ECM overlaid with a dilute solution of lrECM (right) [39,40,49,111]; and (D) Natural or synthetic polymers and macroporous scaffolds support the formation of 3D structures of cells [52,97], have been employed.…”