Understanding Cancer: The Evolution of Cells

Everyone has a vague idea of what it means to live a healthy life. Eating a balanced diet: good. Smoking: bad. Breaking a sweat regularly: good. Binge drinking: bad. Getting a restful night’s sleep: bonus. Being happy: double bonus. Some of us may choose to disregard these basic tenets on occasion, but for the most part, we know the difference between the habits that help us stay youthful and strong, and those that can detract from our well-being.

Cancer is self-generated in the sense that it’s our own cells gone awry. There’s no outside invader. No foreign organism or contagion with a mind of its own and a cellular makeup unlike ours. Cancer is like a sleeping giant lying dormant in all of us. Sometimes, he briefly awakens, inciting a collection of odd cells called a tumor, but, in most cases, before long he’s tamed and lulled back to sleep by the body’s arsenal of artful mechanisms. But occasionally, often when we least expect it, this giant manages to get past our trusty gatekeepers. Something in our defense mechanisms breaks down, throwing off the checks and balances that came so automatically and reliably before, and this causes cellular dysfunction that leads to the growth of cancerous tumors.

Cancer isn’t nearly as straightforward as infectious diseases. Diagnosing, categorizing, and treating make a lot of sense for infectious diseases because infections are species they speciate and divide out, and as such need to be treated like the invaders that they are. In the case of an infectious disease, be it caused by a virus or a bacterium, if we target the Achilles’ heel of the intruder, we win. We don’t need to know anything about the host; we just need to know who the intruder is and how to kill it.

The problem also becomes one of scale: with infectious disease, we only need to consider one scale–the virus or bacterium. But with other human diseases, we need to consider multiple scales, such as the diseased cell, the organ it involves, other nearby organs, the whole body, and so on. It’s no longer a one-on-one battle where one side just needs the right gun. It’s an inscrutable morass of battles, some of it resembling a small civil war and some of it echoing a large war crossing borders.

On the molecular level, cancer happens after changes to cellular genes. Normal cells are equipped with powerful genetic signals that instruct when and how cells can divide to create more cells. Some genes activate cellular propagation, acting like little accelerators of growth. Others behave like molecular brakes, halting growth. This explains why, for example, when a skin wound heals, the cells involved in the mending know when to stop producing new cells so you’re not left with clumps of extra skin. But in a cancer cell, this brilliant balance between active growth and inactivity is disrupted.

The green and red lights that normally control the traffic of growth are misfiring and generating too many green lights. The cell is then left without its regulator and doesn’t know how to stop growing.

Cancer is an interaction of a cell that is no longer under growth control within the environment. What’s even more important to grasp is that cancer isn’t just about uncontrolled cell division and the proliferation of a cellular clan; it’s about another critical characteristic that embodies cancer: its ability to evolve over time. Although people like to envision cancer as a static mad cellular copying ma-chine, it’s much more clever and dynamic than that. Every time a new generation of cancer cells is born, those cells harbor new mutations that go beyond those already present in the genes that are supposed to regulate growth. Making matters worse, when cancer is exposed to chemotherapy, drug-resistant mutants can escape. In other words, just as resistant strains of bacteria can result from antibiotic use, anticancer drugs can produce resistant cancer cells.

From looking at cancer cells, evolution selects for cancer’s appearance, not its genetics. Yes, cancers all have different genes, but they all look alike. There may be fifty different molecular ways to arrive at a particular body “cancer,” such as breast, colon. lung, brain, or prostate, but they all appear and act the same way in the end.

Cancer isn’t a disease of the genes. Rather, it’s a disease where cells evolve to look and behave a certain way, using gene alterations to get there.

Consider someone you know who has cancer. That person used to be somebody who didn’t have cancer, and he or she still has the same DNA in the cells of the body. The difference between having cancer and not having cancer doesn’t solely reside in the genome. Most of that person’s cells are not turning into cancer.

Source : The End of Illness by David B. Agus

Goodreads : https://www.goodreads.com/book/show/12750840-the-end-of-illness