Total Cellular ATP Production Changes With Primary Substrate in MCF7 Breast Cancer Cells.

Cancer growth is predicted to require substantial rates of substrate catabolism and ATP turnover to drive unrestricted biosynthesis and cell growth. While substrate limitation can dramatically alter cell behavior, the effects of substrate limitation on total cellular ATP production rate is poorly understood. Here, we show that MCF7 breast cancer cells, given different combinations of the common cell culture substrates glucose, glutamine, and pyruvate, display ATP production rates 1.6-fold higher than when cells are limited to each individual substrate. This increase occurred mainly through faster oxidative ATP production, with little to no increase in glycolytic ATP production. In comparison, non-transformed C2C12 myoblast cells show no change in ATP production rate when substrates are limited. In MCF7 cells, glutamine allows unexpected access to oxidative capacity that pyruvate, also a strictly oxidized substrate, does not. Pyruvate, when added with other exogenous substrates, increases substrate-driven oxidative ATP production, by increasing both ATP supply and demand. Overall, we find that MCF7 cells are highly flexible with respect to maintaining total cellular ATP production under different substrate-limited conditions, over an acute (within minutes) timeframe that is unlikely to result from more protracted (hours or more) transcription-driven changes to metabolic enzyme expression. The near-identical ATP production rates maintained by MCF7 and C2C12 cells given single substrates reveal a potential difficulty in using substrate limitation to selectively starve cancer cells of ATP. In contrast, the higher ATP production rate conferred by mixed substrates in MCF7 cells remains a potentially exploitable difference.

预计癌症生长需要大量的底物分解代谢和三磷酸腺苷（ATP）周转，以驱动不受限制的生物合成和细胞生长。虽然底物限制可显著改变细胞行为，但底物限制对细胞总ATP产生速率的影响却鲜为人知。在此，我们发现，给予MCF7乳腺癌细胞常见细胞培养底物葡萄糖、谷氨酰胺和丙酮酸的不同组合时，其ATP产生速率比细胞仅限于每种单一底物时高1.6倍。这种增加主要是通过更快的氧化ATP产生实现的，糖酵解ATP产生几乎没有增加。相比之下，未转化的C2C12成肌细胞在底物受限时ATP产生速率没有变化。在MCF7细胞中，谷氨酰胺能出人意料地使细胞获得氧化能力，而丙酮酸（同样是一种严格氧化的底物）却不能。当丙酮酸与其他外源性底物一起添加时，通过增加ATP的供应和需求，提高了底物驱动的氧化ATP产生。总体而言，我们发现MCF7细胞在不同底物受限条件下，在一个不太可能由更持久（数小时或更长时间）的转录驱动的代谢酶表达变化导致的急性（数分钟内）时间范围内，在维持细胞总ATP产生方面具有高度灵活性。给予单一底物时，MCF7细胞和C2C12细胞维持的几乎相同的ATP产生速率表明，利用底物限制选择性地使癌细胞缺乏ATP可能存在困难。相比之下，MCF7细胞中混合底物带来的更高的ATP产生速率仍然是一个可能可利用的差异。