上兩集簡述了癌細胞缺氧的成因,以及缺氧導致癌細胞相對上更為依賴葡萄糖作新陳代謝用途。412Please respect copyright.PENANAcW31YmdJqp412Please respect copyright.PENANAsUsMIvwoGR
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三十秒科學–腫瘤的周遭環境412Please respect copyright.PENANA2kcxf5arsM
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三十秒科學–癌細胞嗜糖的原因412Please respect copyright.PENANAfQiU4GoQkw
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今集我們會講述缺氧對癌細胞自身發展的其中一道好處。412Please respect copyright.PENANAziw59etsWn
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(圖2)當DNA出現異變的時候,細胞裡名為p53的蛋白質便會出手幫忙,號令細胞停止生長(Cell cycle arrest),給予時間讓其他蛋白質幫忙協助修復DNA。412Please respect copyright.PENANAW1JytTcUpr412Please respect copyright.PENANAkxilS63xq7
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若果細胞最後還是無法處理修復DNA的工作,p53便會指示細胞趨向死亡程序(Apoptosis)。412Please respect copyright.PENANAWkckaQZPpT
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腫瘤的出現,是無數DNA變異得出來的成果。因此在這方面來看,p53是防止癌細胞出現的好幫手,因為p53會確保細胞的DNA不會出現變異,或指令出現DNA變異的細胞消失。412Please respect copyright.PENANA53dohFls2W
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但是,有一點非常矛盾的是,大部份普通細胞的p53蛋白質表達率非常低,它能否防止癌細胞出現這一點使人存疑。412Please respect copyright.PENANAPcCLNVziV3
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(圖3)事實上,非常諷刺的是,氧氣含量越低的話,P53蛋白質的表達率便會越高。412Please respect copyright.PENANAPqDkkStEAe412Please respect copyright.PENANAI1CLrT2JM7
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而在缺氧的環境下,擁有p53的蛋白質的細胞便會自動進行死亡。412Please respect copyright.PENANAlkbuo0b6fD
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(圖4)重大的問題是,有部份缺氧的癌細胞會發展出變異版本的p53,失去原有的功能。412Please respect copyright.PENANAn501Hpuhj9
在缺氧施加的壓力下,擁有正常p53版本的細胞會一一死去,變相幫忙篩選出擁有變異版本p53的細胞,使它們逐漸成為大多數。412Please respect copyright.PENANANZkCiQfQ95412Please respect copyright.PENANAaoMnClz0Wy
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而這些擁有變異版本p53的細胞,修復DNA的能力會大幅度被削弱,因而加劇了DNA變異速度,促成腫瘤繼續長大。412Please respect copyright.PENANAFlylIhm4qb
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(圖5)圖中為腫瘤形成的其中一道概論,癌細胞自製的缺氧環境,變相提供了一道挑選擁有更強DNA變異能力細胞的環境。412Please respect copyright.PENANAzNcra2b1uF
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現實中大部分的的癌細胞均擁有p53變異,而擁有p53變異的細胞更具抵抗化療藥物cis-platin的能力。412Please respect copyright.PENANAPMxduHU9fK
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除缺氧外,大陽的紫外光亦是促使p53變異的好幫手,不少皮膚癌細胞均出現至少一處的p53變異。412Please respect copyright.PENANAPOFXMS4mlp
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那些不塗防曬便與陽光玩遊戲的人,一直是在玩命。412Please respect copyright.PENANAo535XMmySb
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Ref1:https://pubmed.ncbi.nlm.nih.gov/8538748/412Please respect copyright.PENANA0d3dFMB0yT