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  • We all start life as one single cell.

  • Then that cell divides and we are two cells,

  • then four,

  • then eight.

  • Cells form tissues,

  • tissues form organs,

  • organs form us.

  • These cell divisions, by which we go from a single cell

  • to 100 trillion cells,

  • are called growth.

  • And growth seems like a simple thing

  • because when we think of it,

  • we typically think of someone getting taller

  • or, later in life, wider,

  • but to cells, growth isn't simple.

  • Cell division is an intricate chemical dance

  • that's part individual, part community-driven.

  • And in a neighborhood of 100 trillion cells,

  • sometimes things go wrong.

  • Maybe an individual cell's set of instructions, or DNA,

  • gets a typo,

  • what we call a mutation.

  • Most of the time, the cell senses mistakes

  • and shuts itself down,

  • or the system detects a troublemaker

  • and eliminates it.

  • But, enough mutations can bypass the fail-safes,

  • driving the cell to divide recklessly.

  • That one rogue cell becomes two,

  • then four,

  • then eight.

  • At every stage, the incorrect instructions

  • are passed along to the cells' offspring.

  • Weeks, months, or years

  • after that one rogue cell transformed,

  • you might see your doctor about a lump in your breast.

  • Difficulty going to the bathroom could reveal

  • a problem in your intestine,

  • prostate,

  • or bladder.

  • Or, a routine blood test might count too many white cells

  • or elevated liver enzymes.

  • Your doctor delivers the bad news:

  • it's cancer.

  • From here your strategy will depend

  • on where the cancer is and

  • how far it's progressed.

  • If the tumor is slow-growing and in one place,

  • surgery might be all you need, if anything.

  • If the tumor is fast-growing or invading nearby tissue,

  • your doctor might recommend radiation

  • or surgery followed by radiation.

  • 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.

  • Radiation and most forms of chemo work

  • by physically shredding the cells' DNA

  • or disrupting the copying machinery.

  • But neither radiation nor chemotherapeutic drugs target only cancer cells.

  • Radiation hits whatever you point it at,

  • and your blood stream carries chemo-therapeutics

  • all over your body.

  • So, what happens when different cells get hit?

  • Let's look at a healthy liver cell,

  • a healthy hair cell,

  • and a cancerous cell.

  • The healthy liver cell divides only when it is stressed;

  • the healthy hair cell divides frequently;

  • and the cancer cell divides even more frequently and recklessly.

  • When you take a chemotherapeutic drug,

  • it will hit all of these cells.

  • And remember that the drugs work typically by disrupting cell division.

  • So, every time a cell divides,

  • it opens itself up to attack,

  • and that means the more frequently a cell divides,

  • the more likely the drug is to kill it.

  • So, remember that hair cell?

  • It divides frequently and isn't a threat.

  • And, there are other frequently dividing cells in your body

  • like skin cells, gut cells, and blood cells.

  • So the list of unpleasant side effects of cancer treatment

  • parallels these tissue types:

  • hair loss,

  • skin rashes,

  • nausea,

  • vomiting,

  • fatigue,

  • weight loss,

  • and pain.

  • That makes sense because these are the cells that get hit the hardest.

  • So, in the end, it is all about growth.

  • Cancer hijacks cells' natural division machinery and forces them to put the pedal to the metal, growing rapidly and recklessly.

  • But, using chemotherapeutic drugs,

  • we take advantage of that aggressiveness,

  • and we turn cancer's main strength

  • into a weakness.

We all start life as one single cell.

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B1 US TED-Ed cancer radiation frequently chemo healthy

【TED-Ed】How do cancer cells behave differently from healthy ones? - George Zaidan

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    Zenn posted on 2015/06/21
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