Towards understanding the role of cellular force in cancer progression

Emon, Md Abul Bashar

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https://hdl.handle.net/2142/121477 Copy

Description

Title

Towards understanding the role of cellular force in cancer progression

Author(s)

Emon, Md Abul Bashar

Issue Date

2023-07-13

Director of Research (if dissertation) or Advisor (if thesis)

Saif, M. Taher A.

Doctoral Committee Chair(s)

Saif, M. Taher A.

Committee Member(s)

• Jasiuk, Iwona
• Bhargava, Rohit
• Smith, Andrew

Department of Study

Mechanical Sci & Engineering

Discipline

Theoretical & Applied Mechans

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Cellular force
• cancer progression
• metastasis
• mechanobiology of cancer

Abstract

Cell generated force plays critical roles in regulating tissue mechanics and functions during many physiological and pathological processes. In the tumor microenvironment (TME), cancer cells recruit and transform the stromal fibroblasts into cancer associated fibroblasts (CAFs) that become highly contractile. Increased CAF contractility increases mechanical stiffness of the extracellular matrices (ECM) in the stroma and helps the cancer cells to metastasize. This doctoral research focused on how the TME stiffness and CAF contractility change with time; and how this process regulates pro-metastatic crosstalk between CAFs and cancer cells. The first challenge in the study was measuring cell force for an extended period of time using monochromatic light for traction force microscopy. It was found that light adversely affects the CAFs and relaxes their contractility. To avoid photo-toxicity, we sought to find a light intensity that is safe for long exposure during experiments. After rigorous investigation of cell traction relaxation with intensity and wavelength sweep, we determined dose-independent threshold intensities for common wavelengths used in microscopy. The safe imaging protocol enabled us to measure cell contractility and examine the role of CAF force in metastasis of colorectal cancer (CRC). We controlled cell force by tuning substrate stiffness (elastic modulus, E = 1, 10 and 40 kPa) and found that CAF contractility increases with increasing stiffness. Genome-wide transcriptome analyses identified that higher force upregulates expressions of pro-metastatic genes such as TGFβ, ILs, FGFs, CXCLs; and pathways linked to Yes Associated Protein (YAP). Remarkably, we found that activin A (a cytokine from the TGFβ family) secretion by the CAFs highly increases with elevated cell force. We also found that CAF-secreted activin A induces cancer cell migration and epithelial to mesenchymal transition (EMT), indicating that increased TME stiffness leads to force-mediated activin A signaling. These experiments provided novel insights, with the limitation of having cells on 2D substrates. However, cells in the TME generate traction on the surrounding three-dimensional matrices that change with time. There was no method available to directly quantify single-cell forces and matrix remodeling in 3D. To address this gap, we microfabricated a high-resolution sensor that hosts a 3D tissue formed by self-assembly of cells and ECM. This sensor can measure cell forces (with 1-nN resolution) and changes in the tissue stiffness. We measured single and multicellular force dynamics and found that CAF/cancer cell co-culture significantly increased ECM (collagen I) stiffness. This provided evidence that crosstalk between cancer cells and CAFs facilitates matrix remodeling and metastatic progression. Enabled by the sensor, we explored the biomolecular origin of cell response to stiffness/force in 3D and tested the hypothesis that CAF-cancer cell crosstalk is sustained by force-activated YAP (a transcription co-activator that controls critical oncogenes including TGFβ). YAP is mechanosensitive; however, mechanical activation of YAP remains unclear. To understand the mechanism of YAP activation, we controlled cell traction phenotypes utilizing a diverse set of culture microenvironments (2D to 3D); and assessed how stiffness and ECM affect force dynamics to identify the role of stiffness, cell spreading area, force, and nuclear deformation in activating YAP. These results showed that force induced nuclear deformation has the strongest correlation with YAP activation. Going forward, a future study can be investigating whether YAP is implicated in crosstalk between CAF and cancer cells. We can also explore the possibility of utilizing cell force, nuclear deformation, and YAP to develop novel prognostic and therapeutic strategies against cancer.

Graduation Semester

2023-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Md Abul Bashar Emon

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