PTM Based Tumor Microenvironment Monitoring: A Method for Tracking Changes in ECM Rigidity Using Tumor Spheroids

- In tumor invasion, the peripheral tumor cells undergo epithelial-to-mesenchymal transition or EMT, resulting in the local degradation of the extracellular matrix or ECM. We can study the interaction of tumor cells with ECM in vitro.

For studying these interactions, transfer a preformed spheroid derived from pancreatic tumor cells to a plate containing collagen scaffold along with embedded fluorescent tracer probes and culture media. Tumor spheroid releases proteases, which degrade collagen and reduce ECM rigidity, resulting in the free movement of tracer probes in the ECM.

Incubate the plate for desired time duration. Observe the sample under a light microscope to look at the grid of sample points in the collagen scaffold and record video data from them. The region of the matrix near the spheroid shows maximum collagen degradation. Therefore, it has increased probe motion. In contrast, the area farther from the spheroid shows less collagen degradation, resulting in restricted movement of probe molecules.

This technique of examining the rheological properties of ECM by measuring the trajectories of tracer particles is known as particle-tracking microrheology or PTM. In the followi