Publications

Unjamming transitions from a solid-like to a fluid-like state are a gateway to breast epithelial cancer invasion. However, the mechanical interplay between phase transitions and dimension transitions, in particular wetting, remains elusive, despite being critical for understanding the onset of metastatic dissemination. This study shows that unjamming, mediated by the RAB5A GTPase, alters carcinoma spheroid fluidity, rigidity, and rewires adhesion mechanics to drive supracellular active wetting as a new mode of tumor expansion. Spheroid fluidification enhances the selective expression of integrin subunits and increases focal adhesion dynamics, inducing a fluid-like spreading behavior on specific matrix ligands. Notably, nanoscale regulation of integrin clustering can select for distinct phase transitions at the collective scale upon wetting. In this framework, fluidized spheroids polarize into cohesive "supracells", and maintain a stiff peripheral actin bundle as measured by nanomechanical mapping. Furthermore, a combination of Brillouin microscopy and 2.5D traction force analysis reveals a mechanical switch within the spheroid core, characterized by significant cell softening and a reduction in compressive forces exerted on the substrate, thereby mimicking the wetting of a liquid droplet. These findings establish unjamming-driven active wetting as a key mechanism to comprehend the molecular and biophysical underpinnings of solid tumor invasion.

JTD Keywords: Adhesion, Biophysics, Dynamics, Epithelia, Integrin, Mechanobiology, Mechanotransduction, Mesenchymal transitions, Paxillin, Rab5a-mediated breast carcinoma fluidification, Snai, Softening, Spheroid wetting, Supracellular motilit

The FOXA family of transcription factors regulates chromatin structure and gene expression especially during embryonic development. In normal breast tissue FOXA1 acts throughout mammary development; whereas in breast carcinoma its expression promotes luminal phenotype and correlates with good prognosis. However, the role of FOXA2 has not been previously studied in breast cancer. Our purpose was to analyze the expression of FOXA2 in breast cancer cells, to explore its role in breast cancer stem cells, and to correlate its mRNA expression with clinicopathological features and outcome in a series of patients diagnosed with breast carcinoma. We analyzed FOXA2 mRNA expression in a retrospective cohort of 230 breast cancer patients and in cell lines. We also knocked down FOXA2 mRNA expression by siRNA to determine the impact on cell proliferation and mammospheres formation using a cancer stem cells culture assay. In vitro studies demonstrated higher FOXA2 mRNA expression in Triple-Negative/Basal-like cells. Further, when it was knocked down, cells decreased proliferation and its capability of forming mammospheres. Similarly, FOXA2 mRNA expression was detected in 10 % (23/230) of the tumors, especially in Triple-Negative/Basal-like phenotype (p < 0.001, Fisher's test). Patients whose tumors expressed FOXA2 had increased relapses (59 vs. 79 %, p = 0.024, log-rank test) that revealed an independent prognostic value (HR = 3.29, C.I.95 % = 1.45-7.45, p = 0.004, Cox regression). Our results suggest that FOXA2 promotes cell proliferation, maintains cancer stem cells, favors the development of Triple-Negative/Basal-like tumors, and is associated with increase relapses.

JTD Keywords: Breast carcinoma, Cancer stem cells, FOXA2, Prognosis