This image depicts an obstacle race of sorts: it shows a number of cells trying to move along micron-scale channels to test their response to their chemical environment. When living cells sense a concentration gradient of some chemical they’re interested in so that, say, they sense some nutrient is bigger over there than back-over-here, they may try to hobble over to make the most out of the situation. (And, of course, depending on the kind of cell they may be quite proficient at hobbling over.)
These particular cells are human breast cancer cells racing towards a nutrient called epidermial growth factor. Under normal conditions, these cells are in fact the tendril-tips of an expanding cancerous tumour that’s ready to metastasise – that is, to spread to other tissues and organs. Metastasising cancer cells to not in fact simply drift along wherever the blood or lymphatic fluid it’s in will take them; rather, they actively seek out nice nesting places for offshoot tumours to grow. The study this picture forms part of tries to understand where and why the invading cancer cells will try to move, in an effort to interfere with the process and stop cancer from spreading.
Here the cells completely block the 12-micron channels they’re in which allows researchers to make the concentration different on the forward and backward sides of each cell; this concentration is shown in green. The image technique is also quite interesting for me. The nucleus and mitochondriae have been dyed so that they’ll fluoresce in blue and red, and the rest of the cell, which would normally be invisible, is captured using phase contrast microscopy, which uses interference with a secondary light beam to detect slight delays in light travel time through the cell as compared to the surrounding fluid.