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  • During World War I, one of the horrors of trench warfare

  • was a poisonous yellow cloud called mustard gas.

  • For those unlucky enough to be exposed,

  • it made the air impossible to breathe, burned their eyes,

  • and caused huge blisters on exposed skin.

  • Scientists tried desperately to develop an antidote to this vicious weapon of war.

  • In the process they discovered the gas was irrevocably damaging the bone marrow

  • of affected soldiershalting its ability to make blood cells.

  • Despite these awful effects, it gave scientists an idea.

  • Cancer cells share a characteristic with bone marrow: both replicate rapidly.

  • So could one of the atrocities of war

  • become a champion in the fight against cancer?

  • Researchers in the 1930s investigated this idea

  • by injecting compounds derived from mustard gas

  • into the veins of cancer patients.

  • It took time and trial and error to find treatments that did more good than harm,

  • but by the end of World War II,

  • they discovered what became known as the first chemotherapy drugs.

  • Today, there are more than 100.

  • Chemotherapy drugs are delivered through pills and injections

  • and use "cytotoxic agents," which means compounds that are toxic to living cells.

  • Essentially, these medicines cause some level of harm to all cells in the body

  • even healthy ones.

  • But they reserve their most powerful effects for rapidly-dividing cells,

  • which is precisely the hallmark of cancer.

  • Take, for example, those first chemotherapy drugs,

  • which are still used today and are called alkylating agents.

  • They're injected into the bloodstream,

  • which delivers them to cells all over the body.

  • Once inside, when the cell exposes its DNA in order to copy it,

  • they damage the building blocks of DNA's double helix structure,

  • which can lead to cell death unless the damage is repaired.

  • Because cancer cells multiply rapidly,

  • they take in a high concentration of alkylating agents,

  • and their DNA is frequently exposed and rarely repaired.

  • So they die off more often than most other cells,

  • which have time to fix damaged DNA

  • and don't accumulate the same concentrations of alkylating agents.

  • Another form of chemotherapy involves compounds called microtubule stabilizers.

  • Cells have small tubes that assemble to help with cell division

  • and DNA replication, then break back down.

  • When microtubule stabilizers get inside a cell,

  • they keep those tiny tubes from disassembling.

  • That prevents the cell from completing its replication, leading to its death.

  • These are just two examples of the six classes of chemotherapy drugs

  • we use to treat cancer today.

  • But despite its huge benefits, chemotherapy has one big disadvantage:

  • it affects other healthy cells in the body that naturally have to renew rapidly.

  • Hair follicles, the cells of the mouth, the gastrointestinal lining,

  • the reproductive system, and bone marrow are hit nearly as hard as cancer.

  • Similar to cancer cells, the rapid production of these normal cells

  • means that they're reaching for resources more frequently

  • and are therefore more exposed to the effects of chemo drugs.

  • That leads to several common side effects of chemotherapy,

  • including hair loss, fatigue, infertility, nausea, and vomiting.

  • Doctors commonly prescribe options to help manage these side-effects,

  • such as strong anti-nausea medications.

  • For hair loss, devices called cold caps can help lower the temperature

  • around the head and constrict blood vessels,

  • limiting the amount of chemotherapy drugs that reach hair follicles.

  • And once a course of chemo treatment is over,

  • the healthy tissues that've been badly affected by the drug will recover

  • and begin to renew as usual.

  • In 2018 alone, over 17 million people world-wide received a cancer diagnosis.

  • But chemotherapy and other treatments have changed the outlook for so many.

  • Just take the fact that up to 95% of individuals with testicular cancer

  • survive it, thanks to advances in treatment.

  • Even in people with acute myeloid leukemiaan aggressive blood cancer

  • chemotherapy puts an estimated 60% of patients under 60

  • into remission following their first phase of treatment.

  • Researchers are still developing more precise interventions

  • that only target the intended cancer cells.

  • That'll help improve survival rates while leaving healthy tissues

  • with reduced harm,

  • making one of the best tools we have in the fight against cancer even better.

During World War I, one of the horrors of trench warfare

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化学療法の効果は?- ヒョンス・ジョシュア・ノ (How does chemotherapy work? - Hyunsoo Joshua No)

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    shoushou に公開 2021 年 01 月 14 日
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