## Materials and Methods  
### Cell Culturing and Manufacturing of Fluidic Chambers  
A descriptive schematic of the used fluidic chip, in which the cells were cultured, is shown in Figure 1a. Three entrances of the fluidic chip were used for seeding the cells inside the channel, providing the cells with cellular medium and treating the cells with TGF-\(\beta\) respectively. The inlet channels had a thickness of 50 \(\upmu\)m and a length of 5 mm, the main channel had a thickness of 150 \(\upmu\)m and a length of 7 mm. The channel had a height of 250 \(\upmu\)m. All inlets and the outlet had a diameter of 1 mm. Overall, the fluidic chip had a surface area of 1.8 \(\times\) 10\({}^{6}\)\(\upmu\)m\({}^{2}\) and a volume of 4.5 \(\times\) 10\({}^{8}\)\(\upmu\)m\({}^{3}\). The fluidic chip was fabricated by replica molding from an SU-8 (MicroChem)/silicon master based on a ratio of 10:1 to curing agent. The master mold was produced by ultraviolet (UV) lithography. After pouring polydimethylsiloxane (PDMS) on a mold, the mixture was degassed in a vacuum chamber for air bubble removal and cured at 80 \({}^{\circ}\)C for 1 h in the oven. Bonding to a glass slide was done after oxygen plasma of both surfaces and conformal contact (Harrick Plasma cleaner/sterilizer, 4 mbar, 120 s). Assembly quality control and characterization were done by optical 3D profilometry (VK-X250, KEYENCE, Germany). An image of the manufactured fluidic chip is shown in Figure 1b. Figure 1: **(a)** A descriptive figure of the used fluidic chip. Three entrances of the fluidic chip were used for seeding the cells inside the channel, providing the cells with cellular medium and treating the cells with TGF-\(\beta\) respectively. **(b)** An image of the manufactured fluidic chip. **(c)** A schematic view of the used digital holographic microscopy (DHM) setup. A 527 nm He-Ne laser is used as a coherent light source. The piezo motor is used for phase stepping and the integrated charge coupled device (CCD) sensor for capturing the interferogram which is synchronized with the motion of the actuator. **(d)** Our experimental setup based on a phase-stepping Mach–Zehnder interferometry. A 6-axis Hexapod is used to move the observed sample in the lateral axis in order to focus on different cells during a single experiment. During the sample preparation procedure, cancer cells were suspended in their respective mediums with a density of 10 \(\times\) 10\({}^{7}\) cells/mL, injected in the lower inlet of the fluidic chip using a syringe. Concentration of the cells inside the chip were 25,000 cells per cubic millimeter when the cells were first seeded. The cells were then left to incubate for 15 min in CO\({}_{2}\) at 37 \({}^{\circ}\)C for cross-linking. Then, the fluidic chips were modified by polydopamine (Sigma-Aldrich, St. Louis, MO, USA) and 3-Aminopropyl triethoxysilane (Sigma-Aldrich) for immobilization of circulating tumor cells (CTCs). A homogeneous cell solution was added to the modified surfaces in a sterile environment. After 8 h, the modified surface was washed with cell culture medium and all non-adherent cells were removed. The cells were then cultured inside these fluidic chips for 24 h and subsequently treated with the TGF-\(\beta\) enzyme which starts the epithelial-mesenchymal transition process. After this process, the cell culture was observed throughout a 48 h period with 6 h intervals. The cells were only taken out of the incubator for imaging during the 48 h process. The imaging of a single sample took approximately 7 min and the cells were kept in sterile conditions in order to prevent apoptosis. The used cell lines were HCT-116, ONCO-DG-1, MDA-MB-231, and HUVEC.