Swirling motion of breast cancer cells radially aligns collagen fibers to enable collective invasion

Background and hypothesis:

Cancer metastasis is the development of secondary tumours at a site distinct from the original primary cancer site, by the cells that have escaped from the primary tumour. Metastasis is one of the major causes of patient mortality and the failure of cancer therapies. Previous studies have reported that cells from the primary tumour often migrate in clusters, and that such collective cell migration may be associated with adverse clinical outcomes. Furthermore, matrix stiffness affects tumour cell morphology and migration, with increased matrix stiffness promoting the invasive phenotype of cancer cells and denser matrices promoting collective invasion of cells. The preprinted study highlighted here aims to investigate the role of collagen matrix stiffness and mechanical plasticity in influencing the collective invasion of breast cancer cells. The study also aims to examine whether breast cancer cells themselves can collectively remodel the collagen-rich matrix into a TACS-3 architecture, suitable for collective invasion.

Key Findings:

Matrix mechanical plasticity, increased matrix stiffness with proteases and cell-cell adhesions promote collective invasion by breast cancer cells: The authors used an interpenetrating network of type-1 collagen and alginate (acIPNs) to mimic the ECM. The stiffness and plasticity of these acIPNs were modulated independently by varying the molecular weight and cross-linker concentration of alginate. To assess how matrix plasticity and stiffness mechanical properties regulate the invasion of breast cancer spheroids, MCF10AT spheroids were embedded in high-plasticity and low-plasticity matrices at 0.6, 1.2, and 3 kPa stiffnesses. Both collective and single-cell invasion were observed in the case of high-plasticity matrices across the range of stiffnesses, with increased stiffness promoting collective invasion over single-cell invasion. Upon broad inhibition of matrix metalloproteases, the authors observed a decrease in invading strand width in high plasticity acIPNs without an effect on the strand length of invading cells. This suggests that MMPs may not be strictly required for collective invasion. Furthermore, a knockdown of Ecad and p120-catenin in MF10AT spheroids led to a decrease in invasiveness in high plasticity acIPNs only at high stiffness (3kPa), indicating that cell-cell adhesion plays an essential role in collective invasion and that Ecad and p120 can facilitate invasion in high stiffness ECM of sufficient plasticity.

Radial alignment of col1 by collectively invading cells precedes invasion: In high-plasticity acIPNs embedded with spheroids, the authors observed a permanent remodelling of the alginate along with the radial alignment of col1 at the spheroid-matrix interface all around the spheroid. This remodelling, however, was not observed in low-plasticity matrices. Spheroids in low-plasticity matrices with pre-aligned col1 showed increased invasion, indicating that alignment of col1 supports collective invasion even in low-plasticity matrices. Additionally, the radial alignment of col1 was cell-cell adhesion-dependent, as Ecad and p120 KD spheroids failed to radially remodel col1.

Breast cancer cells exhibit a swirling motion before and during collective invasion: In high-plasticity acIPNs, the authors expected the radial alignment of col1 to be a result of the radial motion of cells at the spheroid-ECM interface. Contrary to this expectation, the authors observed that the cells migrated tangentially at the spheroid-ECM interface, which they described as a ‘swirling’ motion. This tangential mode of migration was observed in both the collectively invading strand and the non-invading front. The knockdown of Ecad and p120 hampered this motion, with the cells no longer exhibiting any swirling and appearing stuck in their positions. The tangential swirling motion of cells giving rise to radially arranged col1 could be attributed to the phenomenon of negative normal stress. In this case, the shearing of fibrous networks is due to the tangential motion of cells to the stretching of the fibres, generating radially contractile stresses. These stresses align col1 radially with the basement membrane acting as a mechanical insulator, preventing the remodelling of the col1.

What do I like the most about the preprint?

I am curious about understanding cellular behaviour and how cells interact with and modify their environment. Owing to these interests, I chose to highlight this preprint, which investigates how the pattern of movement of breast cancer cells arranges the collagen fibers of the ECM, promoting collective cell invasion. The study describes the role of breast cancer cells in remodelling the collagen fibers independent of other cells, such as cancer-associated fibroblasts. Furthermore, the authors also investigated the physiological relevance of their findings and correlated them to observations from invasive breast cancer.

Significance of the study:

This study highlights the relationship between tumour cells and extracellular matrix remodelling and provides important insights into the mechanistic basis for disease progression. Such results could prove important for developing therapeutic methodologies to prevent cancer progression and invasion.

Tags: ecm, matrix remodeling, spheroids

doi: https://doi.org/10.1242/prelights.40750

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