Panoply™ Human SLC7A11 Over-expressing Stable Cell Line

SLC7A11-mediated cystine uptake is essential for maintaining redox balance and cell survival. This study demonstrates that for cancer cells with high SLC7A11 expression, this process entails a significant metabolic cost. Due to the low solubility of cystine, its active uptake is potentially toxic, compelling SLC7A11-overexpressing cancer cells to continuously reduce it to the more soluble cysteine. This process heavily depletes intracellular NADPH pools, rendering these cells highly dependent on the pentose phosphate pathway (PPP). Restricting glucose supply to SLC7A11-overexpressing cancer cells leads to marked intracellular cystine accumulation, collapse of the redox system, and rapid cell death; conversely, interventions that inhibit disulfide accumulation can rescue these cells from death. Furthermore, the researchers found that glucose transporter (GLUT) inhibitors selectively kill SLC7A11-overexpressing cancer cells and suppress the growth of such tumors. These findings reveal a coupling between SLC7A11-mediated cystine metabolism and the PPP, identifying a metabolic vulnerability that can serve as a therapeutic target for cancers with high SLC7A11 expression.

Metabolomic analysis comparing SLC7A11-overexpressing 786-O cells with empty vector (EV) control cells revealed that SLC7A11 overexpression increased intracellular cysteine ​​levels but reduced levels of intracellular glutamate and glutamate-derived metabolites (such as α-ketoglutarate) (Figure 1a). Surprisingly, one of the significantly increased metabolites was 6-phosphogluconate (6PG), a metabolite of the pentose phosphate pathway (PPP) (Figure 1a, b). Further analysis showed elevated levels of other PPP metabolites and gluconate-a metabolite related to 6PG-in SLC7A11-overexpressing 786-O cells (Figure 1b). Metabolic flux analysis demonstrated that SLC7A11 overexpression led to an increase in lactate M1 labeling and a decrease in lactate M2 labeling (Figure 1c), resulting in a significant increase in the relative flux of glucose carbon entering the PPP (Figure 1d). Furthermore, as SLC7A11 overexpression did not affect the rate of glucose consumption, the absolute flux through the oxidative PPP increased (Figure 1e). The oxidative PPP plays a crucial role in generating cytosolic NADPH, which supports reductive biosynthetic pathways such as palmitate biosynthesis. Consistent with this, 3-2H-glucose tracing experiments showed an enhanced contribution of PPP enzymes to cytosolic NADPH production in SLC7A11-overexpressing 786-O cells (Figure 1f). Collectively, these data indicate that SLC7A11 promotes flux through the oxidative PPP.

Figure 1. SLC7A11 promotes the PPP flux. (Liu X, et al., 2020)