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We all start life as one single cell.
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Then that cell divides and we are two cells,
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then four,
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then eight.
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Cells form tissues,
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tissues form organs,
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organs form us.
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These cell divisions, by which we go from a single cell
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to 100 trillion cells,
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are called growth.
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And growth seems like a simple thing
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because when we think of it,
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we typically think of someone getting taller
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or, later in life, wider,
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but to cells, growth isn't simple.
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Cell division is an intricate chemical dance
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that's part individual, part community-driven.
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And in a neighborhood of 100 trillion cells,
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sometimes things go wrong.
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Maybe an individual cell's set of instructions, or DNA,
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gets a typo,
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what we call a mutation.
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Most of the time, the cell senses mistakes
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and shuts itself down,
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or the system detects a troublemaker
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and eliminates it.
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But, enough mutations can bypass the fail-safes,
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driving the cell to divide recklessly.
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That one rogue cell becomes two,
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then four,
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then eight.
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At every stage, the incorrect instructions
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are passed along to the cells' offspring.
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Weeks, months, or years
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after that one rogue cell transformed,
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you might see your doctor about a lump in your breast.
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Difficulty going to the bathroom could reveal
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a problem in your intestine,
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prostate,
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or bladder.
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Or, a routine blood test might count too many white cells
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or elevated liver enzymes.
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Your doctor delivers the bad news:
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it's cancer.
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From here your strategy will depend
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on where the cancer is and
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how far it's progressed.
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If the tumor is slow-growing and in one place,
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surgery might be all you need, if anything.
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If the tumor is fast-growing or invading nearby tissue,
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your doctor might recommend radiation
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or surgery followed by radiation.
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If the cancer has spread, or if it's inherently everywhere like a leukemia, your doctor will most likely recommend chemotherapy or a combination of radiation and chemo.
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Radiation and most forms of chemo work
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by physically shredding the cells' DNA
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or disrupting the copying machinery.
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But neither radiation nor chemotherapeutic drugs target only cancer cells.
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Radiation hits whatever you point it at,
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and your blood stream carries chemo-therapeutics
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all over your body.
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So, what happens when different cells get hit?
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Let's look at a healthy liver cell,
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a healthy hair cell,
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and a cancerous cell.
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The healthy liver cell divides only when it is stressed;
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the healthy hair cell divides frequently;
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and the cancer cell divides even more frequently and recklessly.
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When you take a chemotherapeutic drug,
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it will hit all of these cells.
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And remember that the drugs work typically by disrupting cell division.
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So, every time a cell divides,
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it opens itself up to attack,
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and that means the more frequently a cell divides,
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the more likely the drug is to kill it.
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So, remember that hair cell?
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It divides frequently and isn't a threat.
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And, there are other frequently dividing cells in your body
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like skin cells, gut cells, and blood cells.
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So the list of unpleasant side effects of cancer treatment
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parallels these tissue types:
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hair loss,
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skin rashes,
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nausea,
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vomiting,
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fatigue,
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weight loss,
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and pain.
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That makes sense because these are the cells that get hit the hardest.
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So, in the end, it is all about growth.
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Cancer hijacks cells' natural division machinery and forces them to put the pedal to the metal, growing rapidly and recklessly.
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But, using chemotherapeutic drugs,
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we take advantage of that aggressiveness,
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and we turn cancer's main strength
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into a weakness.