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In between mining Vespene gas and constructing additional pylons, gamers have been unknowingly learning about how cancer works, and maybe how to beat it. [caption id="attachment_7781" align="aligncenter" width="644" caption="Kerrigan, leader of the Zerg swarm"][/caption] Amid the frantic clicking and hot-keying that goes on in homes and internet cafes around the world, players of the immensely popular computer game StarCraft have been unknowingly gaining a working knowledge of cancer. But the insight into the illness depends on which of the three races in the game you play. The future-minded Terran speak to dreams of human expansion in space. The telepathic Protoss keep spirituality in a galaxy dominated by science. However, the last race--the all-consuming Zerg--is more than a horde of ravenous genetic abominations reminiscent of John Carpenter's The Thing; they are fitting analogs for possibly the most dreaded ailment of all. Cancer is a Zerg rush of the human body. In form, function, and strategy, the Zerg of StarCraft were designed to overwhelm opponents with numbers and genetic versatility. In the canon, the Zerg sweep through the galaxy to assimilate the genetic material of the strongest species. They artificially select themselves to succeed, as we do with dogs or cabbage. As any regular player of the game will know, it's not just a hard carapace or regenerative biology that make the Zerg so dangerous; it's the swarm. Inexperienced players can be swarmed within five minutes of starting a multiplayer match. Some players even type "gg" ("good game") at the mere sight of a mass of rapidly moving Zerg heading towards their base (trust me). A gamer controlling the Zerg has direct control over them, but just based on the biology that the canon has set up, it's a safe bet that the swarm would be just as successful without a central leader, as we see in swarms of fish, locusts, and birds. (Like locusts, the Zerg move and act like insects of the Starship Troopers variety, and even bear striking resemblances to real world insect biology.) A real and much more frightening swarm is cancer. A simple mistake in a cell can cause it to continue dividing instead of stopping (or killing itself). One cell becomes two, two become four, four eventually become a tumor. Survival rates for different cancers vary from decent to terminal, but the chances of getting cancer are strikingly high. The chance of a US man or woman being diagnosed with some form of cancer is around 40 percent. Cancer is so dangerous and difficult to treat because of the similarities the disease shares with the Zerg. Genetic versatility and sheer numbers are cancer's strengths. A cancerous cell that the body can't naturally destroy is a study in natural selection. As the cell uncontrollably divides, each successive division brings with it a chance for the new cancer cell to contain a mutation--DNA replication is never perfect. Most of the mutations will do nothing, but given how many cells are dividing--billions upon billions--mutations can spring up that give the cancer a selective advantage. Maybe the mutation accelerates cell division. Maybe it redirects more blood flow to the growing mass of cells parasitically throbbing in your body. And maybe the mutation even helps the new cells evade the immune system. Cancer is real-time evolution, and your body is the selective pressure. The Zerg function in much the same way. Through rampant expansion, they are able to search out beneficial genetic material from the hardiest species, and intentionally put themselves in hostile environments to force their own, pressured evolution. The Zerg extend "creep" in order to colonize more land, as does cancer with metastasis--the spreading of cells that eventually grow more tumors. Only the strong survive in StarCraft, and the Zerg are a galactic cancer. The rapid evolution of a cancer is at the heart of why it is so hard to treat. Surgery is sometimes possible, but even a few cells left over can fuel the swarm again. Similarly, a solitary Zerg drone can become a whole hive if left unchecked. The best StarCraft players fight the Zerg like surgeons: If you see a tumor, you have to get it all to survive. If surgery isn't an option, then targeted therapies like chemotherapy or radiation are the best lines of defense we have against cancer. But like how a cancer can thrive under the selective pressure of our bodies, treatments to get rid of it are even more pressures to evolve. Chemotherapy fails, for example, because by the time the cancer is treated a number of the cancer cells could have a mutation that gives them resistance to it. The chemo will hopefully wipe out everything else, but those resistant remain to divide and conquer. Evolution is ultimately why cancer is so deadly. Take two biopsies from different sides of a tumor and they can be genetically very different, making it that much harder to fight. Variation is the toolbox of evolution, and this variation gives cancer strength. But variation may also be cancer's Achilles' heel. Carl Zimmer in the New York Times recently reported on a clever way to possibly combat the mutations that can give cancer its deadly power. Treatments fail when a cancer has evolved to the point of resistance, but the more treatments that are provided simultaneously, the less likely a cancer cell is to have resistance to them. The likelihood that a cancer cell has the mutation to resist two treatments is significantly less likely than resisting one treatment alone. This approach still has to be tested clinically, but it could be our way through cancer's swarm. StarCraft strategy already mimics a simultaneous assault on cancer. To win, you have to apply pressure quickly, consistently, and from all possible angles. One Terran battlecruiser with a Yamato Cannon is unlikely to stop the Zerg rush; throw in a simultaneous nuclear strike just to be safe (science has shown that the Terran would be the galactic victors, after all). The similarities between cancer and the Zerg don't stop there. To spread, the Zerg actually put down tumors; their wide genetic variation also makes them deadly; and because the Zerg have DNA like the rest of us, they are also vulnerable to concentrated blasts of radiation like cancer is (the same kind of thing that killed Kirk). In many respects, the Zerg are StarCraft's cancer. Millions of players have been tirelessly clicking as analog oncologists wiping out a rapidly evolving foe, unknowingly discovering how real cancer works and possibly how to fight it. Science can creep up on you like that. -- Image Credit: Statue of Kerrigan, Queen of Blades from StarCraft at BlizzCon 2010 by Brian J. Matis Hydralisk concept art by Tr??ng