Aspartate is a limiting metabolite for cancer cell proliferation under hypoxia and in tumours

Abstract

As oxygen is essential for many metabolic pathways, tumour hypoxia may impair cancer cell proliferation. However, the limiting metabolites for proliferation under hypoxia and in tumours are unknown. Here, we assessed proliferation of a collection of cancer cells following inhibition of the mitochondrial electron transport chain (ETC), a major metabolic pathway requiring molecular oxygen. Sensitivity to ETC inhibition varied across cell lines, and subsequent metabolomic analysis uncovered aspartate availability as a major determinant of sensitivity. Cell lines least sensitive to ETC inhibition maintain aspartate levels by importing it through an aspartate/glutamate transporter, SLC1A3. Genetic or pharmacologic modulation of SLC1A3 activity markedly altered cancer cell sensitivity to ETC inhibitors. Interestingly, aspartate levels also decrease under low oxygen, and increasing aspartate import by SLC1A3 provides a competitive advantage to cancer cells at low oxygen levels and in tumour xenografts. Finally, aspartate levels in primary human tumours negatively correlate with the expression of hypoxia markers, suggesting that tumour hypoxia is sufficient to inhibit ETC and, consequently, aspartate synthesis in vivo. Therefore, aspartate may be a limiting metabolite for tumour growth, and aspartate availability could be targeted for cancer therapy.

Tumor-Stroma Mechanics Coordinate Amino Acid Availability to Sustain Tumor Growth and Malignancy

“…Among these metabolites, we found Asp production by CAF crucial to sustain CCs proliferation. Consistent with these results, recent reports have shown that aspartate acquisition is a metabolic limitation encountered by tumors in their native in vivo environment and that overcoming this limitation is advantageous for tumour growth(Garcia-Bermudez et al, 2018; Sullivan et al, 2018). Together, our results clarify the importance of Asp in tumor progression and demonstrate a fine-tuneable mechanism by which CCs are able to adjust their Asp needs depending on tumor niche stiffness.…”

SLC 1A3 contributes to L‐asparaginase resistance in solid tumors

“…More specifically, we observed increased vascular endothelial growth factor A (VEGFA) mRNA levels after combinational treatment in PC3 cells (Fig EV4A), in line with previous observations that suggested a negative correlation between VEGFA and aspartate level (Garcia‐Bermudez et al , ). Moreover, the decreased mRNA level of lactate dehydrogenase A (LDHA) can explain the depletion in lactate level measured by metabolites profiling (Fig E).…”

“…SLC1A3 is mainly expressed in brain tissues (Fig EV1C), critical for the termination of excitatory neurotransmission (Kanai et al , ). Recent studies have highlighted the importance of SLC1A3‐mediated aspartate uptake for cancer cell proliferation under hypoxia and crosstalk between cancer cells and cancer‐associated fibroblasts in the tumor niche (Alkan et al , ; Garcia‐Bermudez et al , ; Sullivan et al , ; Tajan et al , ; Bertero et al , ). We also observed elevated SLC1A3 RNA levels in several tumor types from the TCGA database [especially kidney renal clear cell carcinoma (KIRC, P = 5.5 × 10 −30 ), kidney renal papillary cell carcinoma (KIRP, P = 2.1 × 10 −10 ), liver hepatocellular carcinoma (LIHC, P = 3.2 × 10 −10 ), and stomach adenocarcinoma (STAD, P = 6.1 × 10 −5 )] (Fig EV1D).…”

Decreased glucose bioavailability and elevated aspartate metabolism in prostate cancer cells undergoing epithelial‐mesenchymal transition

“…However, the primary substrate for oxidation in cancer cells is often not glucose but glutamine, indicating that aerobic glycolysis is not a replacement but a parallel process (Sullivan, 2015). Under oxidation deficiency such as in the case of electron transport chain inhibition and hypoxia, L‐aspartate serves as a limiting metabolite for cancer cell proliferation and adenine nucleotide synthesis (Garcia‐Bermudez et al, 2018; Sullivan et al, 2015). L ‐asparagine, which is synthesized from L‐aspartate, plays a critical role in the regulation of cellular adaptation to glutamine depletion (Zhang et al, 2014).…”