Influence of the microenvironment on the biomechanical properties of pancreatic ductal adenocarcinoma (PDAC) cells

Abstract

The pancreas is an abdominal organ with digestive and endocrine functions. Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease with low survival rates and poor prognosis, which occurs in the digestive part of the pancreas, specifically due to the conversion of healthy epithelial cells to cancer cells. There are continuous efforts to understand the mechanisms of disease progression, as well as for expanding viable options for therapy. PDAC is characterised by a dense and fibrotic extra-cellular matrix (ECM), which is a dense mass of protein fibers. There are also many cancer-associated cell types. Together, they form the unique milieu of the tumour microenvironment (TME). The various components of the TME promote the aggressive progression and metastasis of PDAC. While the molecular, genetic, and epigenetic mechanisms of the PDAC and its TME have been studied for a long time, the stiffness and mechanical properties of the TME are slowly emerging as important factors in the poor prognosis of PDAC. This work used Atomic Force Microscopy (AFM) to elucidate the subtleties of PDAC mechanics. Two modes were used to study two distinct mechanical aspects: the stiffness or viscoelasticity of PDAC cells and the extent of cell-cell interaction. The AFM is a type of scanning probe microscope that detects piconewton-scale forces. A cantilever with a reflective gold coating on the back is indented upon a sample, and the deflection of the cantilever is detected by an optical-lever. A cantilever with an integrated tip was used to probe the viscoelastic properties of PDAC cell lines. A cantilever with an attached live cell was used to press against other cells, to probe the extent of cell-cell interaction via cell adhesion. A small study on the impact of measurement parameters like experimental CO2 concentration and loading force of the cantilever was also carried out. Four PDAC cell lines were studied in this work: two from the primary cancer site of the pancreas, one from a lymph node metastasis, and one from liver metastasis. The effect of physical cell confinement and ECM-based hydrogels on cell viscoelasticity was studied. The cell-cell interaction within the cancer cells, as well as the extent of their interaction with endothelial cells, was studied. The effect of a potential drug on cell-cell interaction was also studied. Through this work, a mechanical paradigm of pancreatic cancer cells can be established. The interplay between cancer cells and the TME via mechanical clues can be understood better.