西元1924年，Otto Warbug提出癌細胞具有高效率的糖解作用並作為主要的能量來源，即使在正常氧濃度下仍不偏向進行氧化磷酸化；這現象也依據他命名為“瓦氏效應”。瓦氏效應不但能促進腫瘤細胞的生長，對於癌細胞的抗藥性、轉移也有重要的影響。M2型丙酮酸激酶（PKM2）為促成瓦氏效應的主要因子係由於PKM2的活性能受致癌基因的調控，使癌細胞能有效的利用葡萄糖做為合成反應的骨架。在腫瘤發展過程中，缺氧是一個重要的環境因素；且缺氧是一個造成瓦氏效應的可能性機制。低氧刺激會使PKM2表現量增加，顯示缺氧、PKM2及瓦氏效應的關聯性。
為了探討PKM2對於缺氧的影響，因此我建立PKM2持續性沉默細胞。抑制細胞的PKM2表現對於細胞的生長、型態並沒有顯著的影響，對於細胞粒線體膜電位則有提升的作用。在HeLa與A549細胞中，抑制PKM2會使ROS生成減少；在H1299細胞中則是會增加ROS生成量。ROS生成量與細胞面對氧化壓力的敏感性有關，過去的研究指出PKM2能進入細胞核調控細胞凋亡；顯示PKM2的表現與氧化壓力的抵抗性的可能關聯性。粒線體中的電子傳遞鏈抑制物能增加細胞的ROS生成量而導致細胞凋亡，選擇以複合體I抑制物–Rotenone處理細胞；結果顯示沉默PKM2表現能有較高的存活率，初步證實PKM2能促進細胞在氧化壓力下的細胞凋亡。
分析細胞處理低氧後的存活、死亡比例，在HeLa-shPKM2、A549-shPKM2的存活率比野生型細胞高；顯示PKM2表現能誘導低氧環境中的細胞凋亡。H1299細胞處理低氧後，主要是進行細胞壞死；而野生型H1299與H1299-shPKM2的細胞壞死程度沒有差異。低氧會使缺氧誘導因子1與p53表現量增加，兩者交互作用能決定細胞凋亡與否。抑制PKM2能減少p53在低氧刺激的上升量，顯示PKM2能促進p53的穩定表現。持續性沉默PKM2穩定細胞株在低氧處理後的缺氧誘導因子1表現較多，且低氧處理後的過氧化氫生成量也較高；顯示抑制PKM2表現有助於低氧誘導因子1的穩定。這些結果都顯示PKM2能在低氧環境調控p53與缺氧誘導因子1表現而影響細胞凋亡。

In 1924, Otto Warburg proposed a concept that cancer cells with high efficiency glycolysis as the major source of energy; even in normal oxygen concentration, cancer cells did not tend to carry out oxidative phosphorylation; which was the basis of his being named as “ Warburg effect”. Warburg effect not only promotes the growth of tumor cell, but also has important implications for tumor drug-resistant and metastasis. The main factor promoting Warburg effect is PKM2, as a result of its activity could be regulated by oncogene, so cancer cells can effectively use glucose as the skeleton for anabolism. In the process of tumor development, hypoxia is an important environmental factors; hypoxia is a possibile mechanism for Warburg effect. Hypoxia stimulates increasing the level of PKM2, indicating the correlation between hypoxia, PKM2, and Warburg effect.
In order to explore the impact of PKM2 on hypoxia, so I established the stable PKM2-silence cell line. Suppression of PKM2 has no apparent impact on cell growth and morphology, but enhancing the intensity of mitochondrial membrane potential. In HeLa and A549 cells, inhibition of PKM2 would reduce ROS generation; suppression of PKM2 in H1299 cell led to increase in ROS generation. ROS producing amount was relevant in of sensitiveness to oxidative stress, the past research pointed out that PKM2 could translocate to nucleus and control apoptosis; these results showed the association of PKM2 and oxidative resistance. Mitochondrial electron transport chain inhibitor could improve ROS generation leading to apoptosis; firstly, I chose complex I inhibitor-Rotenone to treat with cells. The results revealed that repression of PKM2 could provide higher survival rate, preliminary identified PKM2 could promote apoptosis under oxidative stress.
Analysis of cell survival after hypoxia treatment, the survival rate of HeLa-shPKM2 and A549-shPKM2 are higher than wild-type cells; indicating PKM2 could cause apoptosis in hypoxic. Dealing H1299 cells with hypoxic primarily lead to cell necrosis; there is no difference in the degree of cell necrosis between wild-type H1299 and H1299-shPKM2 cell lines. Hypoxia causes increase in Hypoxia-inducible factor-1 and p53 expression, whether or not apoptosis is dependent on the interaction between the two. Suppression of PKM2 could reduce the increase in p53 under hypoxic stimulus, showing PKM2 could promote the stability of p53 expression. The stable PKM2-silence cells expressed higher hypoxia-inducible factor 1 and hydrogen peroxide generation than wild-type cells after hypoxia treatment, pointing that inhibition of PKM2 contributed to hypoxia-inducible factor 1 stability. These results indicate that PKM2 can influence apoptosis in hypoxia by regulating p53 and hypoxia-inducible factor 1.

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