Two-Channel Compartmentalized Microfluidic Chip for Real-Time Monitoring of the Metastatic Cascade

Metastases are the primary cause of death in cancer patients. Small animal models are helping in dissecting some key features in the metastatic cascade. Yet, tools for systematically analyzing the contribution of blood flow, vascular permeability, inflammation, tissue architecture, and biochemical stimuli are missing. In this work, a microfluidic chip is designed and tested to replicate in vitro key steps in the metastatic cascade. It comprises two channels, resting on the same plane, connected via an array of rounded pillars to form a permeable micromembrane. One channel acts as a vascular compartment and is coated by a fully confluent monolayer of endothelial cells, whereas the other channel is filled with a mixture of matrigel and breast cancer cells (MDA-MB-231) and reproduces the malignant tissue. The vascular permeability can be finely modulated by inducing pro-inflammatory conditions in the tissue compartment, which transiently opens up the tight junctions of endothelial cells. Permeability ranges from 1 mu m/s (tight endothelium) to 5 mu m/s (TNF-alpha at 50 ng/mL overnight) and up to similar to 10 mu m/s (no endothelium). Fresh medium flowing continuously in the vascular compartment is sufficient to induce cancer cell intravasation at rates of 8 cells/day with an average velocity of similar to 0.5 mu m/min. On the other hand, the vascular adhesion and extravasation of circulating cancer cells require TNF-alpha stimulation. Extravasation occurs at lower rates with 4 cells/day and an average velocity of similar to 0.1 mu m/min. Finally, the same chip is completely filled with matrigel and the migration of cancer cells from one channel to the other is monitored over a region of about 400 mu m. Invasion rates of 12 cells/day are documented upon TNF-alpha stimulation. This work demonstrates that the proposed compartmentalized microfluidic chip can efficiently replicate in vitro, under controlled biophysical and biochemical conditions, the multiple key steps in the cancer metastatic cascade.