侵袭性癌症通常以高速率将葡萄糖发酵为乳酸,即使是在氧气的存在下.这被称为有氧糖酵解,或者“Warburg效应”。“人们普遍认为这是糖酵解酶上调的结果。致癌驱动因子可以增加糖酵解途径中大多数蛋白质的表达,包括从细胞质中输出H+等价物的最终步骤。质子出口商保持碱性细胞质pH值,可以增强所有糖酵解酶的活性,即使没有癌基因相关的表达变化。基于这一观察,我们假设,葡萄糖的摄取和发酵代谢增加可能是由细胞中H+当量的排出引起的。
为了检验这一假设,我们稳定转染低糖酵解MCF-7,U2-OS,和糖酵解HEK293细胞表达质子输出系统:PMA1(质膜ATPase1,酵母H-ATPase)或CA-IX(碳酸酐酶9)。通过葡萄糖消耗测量,任一出口商在体外增强有氧糖酵解的表达,乳酸生产,和细胞外酸化率。这导致细胞内pH增加,代谢组学分析表明,这与丙酮酸激酶上游所有糖酵解酶的通量增加有关。这些细胞还在体外表现出增加的迁移和侵袭表型,这些在体内被更积极的行为所概括,由此,产酸细胞形成了具有更高转移率的高级别的肿瘤。用口服缓冲液中和肿瘤酸度降低了转移负担。
因此,增加H+当量输出的癌细胞随后增加细胞内碱化,即使没有致癌驱动突变,这足以改变癌症的新陈代谢,使其朝着有氧糖酵解的上调方向发展,Warburg表型。总的来说,我们已经表明,对癌细胞有利于糖酵解和随后的细胞外酸化的传统理解并不总是线性的。细胞可以,独立于新陈代谢,通过质子输出者活动酸化可以充分驱动它们向糖酵解的新陈代谢,为生存提供重要的健身优势。
Aggressive cancers commonly ferment glucose to lactic acid at high rates, even in the presence of oxygen. This is known as aerobic glycolysis, or the \"
Warburg Effect.\" It is widely assumed that this is a consequence of the upregulation of glycolytic enzymes. Oncogenic drivers can increase the expression of most proteins in the glycolytic pathway, including the terminal step of exporting H+ equivalents from the cytoplasm. Proton exporters maintain an alkaline cytoplasmic pH, which can enhance all glycolytic enzyme activities, even in the absence of oncogene-related expression changes. Based on this observation, we hypothesized that increased uptake and fermentative metabolism of glucose could be driven by the expulsion of H+ equivalents from the cell.
To test this hypothesis, we stably transfected lowly glycolytic MCF-7, U2-OS, and glycolytic HEK293 cells to express proton-exporting systems: either PMA1 (plasma membrane ATPase 1, a yeast H+-ATPase) or CA-IX (carbonic anhydrase 9). The expression of either exporter in vitro enhanced aerobic glycolysis as measured by glucose consumption, lactate production, and extracellular acidification rate. This resulted in an increased intracellular pH, and metabolomic analyses indicated that this was associated with an increased flux of all glycolytic enzymes upstream of pyruvate kinase. These cells also demonstrated increased migratory and invasive phenotypes in vitro, and these were recapitulated in vivo by more aggressive behavior, whereby the acid-producing cells formed higher-grade tumors with higher rates of metastases. Neutralizing tumor acidity with oral buffers reduced the metastatic burden.
Therefore, cancer cells which increase export of H+ equivalents subsequently increase intracellular alkalization, even without oncogenic driver mutations, and this is sufficient to alter cancer metabolism towards an upregulation of aerobic glycolysis, a
Warburg phenotype. Overall, we have shown that the traditional understanding of cancer cells favoring glycolysis and the subsequent extracellular acidification is not always linear. Cells which can, independent of metabolism, acidify through proton exporter activity can sufficiently drive their metabolism towards glycolysis providing an important fitness advantage for survival.