Green fluorescent protein (GFP) was originally discovered in a jellyfish named Aequorea victoria. The jellyfish protein fluoresces beautifully green when illuminated by either blue light or UV light. Scientists figured out the DNA sequence in the jellyfish’s genome that instructs the cell to make the GFP. You can read the actual gene code yourself (below) (bunch of A’s, T’s, C’s, and G’s). Each set of three letters encodes an amino acid, and apparently GFP is made up of 300 amino acids.
Scientists then started genetically modifying cancer cells by inserting the GFP gene sequence into the cancer cell’s genome, thereby creating GFP-cancer cells. Shining a blue light or UV light on the cells, makes them fluoresce a beautifully bright green! Scientists started to track these cancer cells through the body of mice harboring GFP-cancers, to learn about cancer metastasis (spread).
However, there is one big problem with this method of researching cancer metastasis. A normal mouse has an immune system that exists to identify and attack anything that is foreign and doesn’t belong in the body. Certainly, there is nothing in common between Aequora victoria and Mus musculus (typical laboratory mouse). Indeed, when I’ve injected GFP-cancer cells into lab mice, it grows very slowly, if at all, unlike its native non-GFP counterpart, which grows wildly and aggressively, spreading to other organs. The foreign GFP makes the cancer cells stand out like a sore thumb in the eyes of the mouse’s immune system. It’s like making James Bond wear a bright fluorescent green jacket with the words “MI6”! I don’t think he’d be a very effective and stealth spy anymore.
Therefore, for our “What Makes Cancer Cells Metastasize” project, we developed a cancer cell that wears a jacket like James Bond, but it’s invisible to the immune system. Although we can’t just shine a blue light to visualize our custom-designed cancer cell, at least the immune system doesn’t see it either, and our custom-designed cancer cell acts normally (growing and spreading aggressively as it did before the modification). It’s really important to us that in studying how cancer and the immune system interact with each other, we don’t introduce any unnatural alterations, or as Captain James T. Kirk would say, “we must uphold the Prime Directive.”
photo credit for green glowing jellyfish
Daniel 228, Inc. 