Background: Cancer is the term used to describe a group of diseases, which are all characterised by mutation of normal cells and their uncontrollable growth in different parts of the body. Cancer also has the ability to metastasise, which makes it highly malignant and allows it to quickly spread through the body proving quickly fatal. Mechanobiology is a field of science that studies how differences in the mechanical properties of cells affect cellular properties and disease. Cellular contractility is the ability of cells to exert contraction and generate force by cell-matrix interaction. This cell-matrix interaction results in the exertion of cell traction forces, which is essential for cell migration, maintaining cell homeostasis and cell structure. Histone deacetylase 6 (HDAC6) is an enzyme in humans and HDAC6 gene expression correlates with increased carcinogenesis and metastasis of cancer cells.
Aim: To determine the effect of HDAC6 on contractile forces of metastasising human BJ fibroblasts and the molecular mechanisms that control these contractile forces.
Methods: To measure contractile forces of cells, isogenically matched normal, immortalized, transformed, and metastatic human BJ fibroblast cells were cultured on polyacrylamide gels and cells were imaged using Traction force microscopy (TFM). Contractile forces were also measured after HDAC6 inhibition and HDAC6 siRNA knockdown of metastasising cells. Confocal microscopy was also performed to image the cell-matrix adhesions and cell spreading area between the cellular components and extracellular matrix. Cell migration assays were used to evaluate the effect of HDAC6 inhibition or knockdown on the morphological properties of metastasising fibroblast cells. The intracellular force of the nucleus was also measured in metastasising and HDAC6 inhibited cells.
Results: Metastasising cells have increased cellular contractility than normal BJ fibroblasts, but this contractility is reduced significantly when HDAC6 is inhibited using tubacin in metastasising cells. However, this trend is significantly reversed in siRNA knockdown of HDAC6 since contractile forces increase when compared to untreated metastasising cells. Metastasising cells have decreased nuclear forces than normal BJ fibroblasts and this force decreases further when HDAC6 is inhibited. Metastasising cells have smaller cell-matrix adhesions and decreased cell spreading area compared to normal BJ fibroblasts.
Conclusion: Increased cellular contractility in metastasising cells makes them more invasive. This is dependent on HDAC6 activity via its deacetylase and protein-binding functions. Understanding the molecular mechanisms that control this contractility will allow for the development of drugs that can help reduce metastasis of cancer and mortality rates.
