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

Abstract

L‐asparaginase (ASNase) serves as an effective drug for adolescent acute lymphoblastic leukemia. However, many clinical trials indicated severe ASNase toxicity in patients with solid tumors, with resistant mechanisms not well understood. Here, we took a functional genetic approach and identified SLC1A3 as a novel contributor to ASNase resistance in cancer cells. In combination with ASNase, SLC1A3 inhibition caused cell cycle arrest or apoptosis, and myriads of metabolic vulnerabilities in tricarboxylic acid (TCA) cycle, urea cycle, nucleotides biosynthesis, energy production, redox homeostasis, and lipid biosynthesis. SLC1A3 is an aspartate and glutamate transporter, mainly expressed in brain tissues, but high expression levels were also observed in some tumor types. Here, we demonstrate that ASNase stimulates aspartate and glutamate consumptions, and their refilling through SLC1A3 promotes cancer cell proliferation. Lastly, in vivo experiments indicated that SLC1A3 expression promoted tumor development and metastasis while negating the suppressive effects of ASNase by fueling aspartate, glutamate, and glutamine metabolisms despite of asparagine shortage. Altogether, our findings identify a novel role for SLC1A3 in ASNase resistance and suggest that restrictive aspartate and glutamate uptake might improve ASNase efficacy with solid tumors.

Asparagine Synthetase in Cancer: Beyond Acute Lymphoblastic Leukemia

“…However, although, intuitively, ASNS induction has been correlated with resistance to ASNase, it has been known for many years that ASNase-resistant ALL cells present a complex phenotype. Indeed, if ASNS overexpression is sufficient to induce the ASNase-resistant phenotype in specific ALL cell models (22), adequate availability of the ASNS substrates Gln and aspartate (Asp) requires multiple adaptation mechanisms (26,27) (Figure 1).…”

“…Central panel, ASNS induction and increase in GS protein expression are not able to rescue ASNase-induced apoptotis due to poor availability of their substrates Asp and Glu. Lower panel, the overexpression of EAAT1 or EAAT3 anionic amino acid transporters provides Glu (for the synthesis of Gln, through Glutamine Syntethase) and Asp (27). Both Gln and Asp are needed for Asn synthesis via ASNS and for an effective cell rescue.…”

“…Both Gln and Asp are needed for Asn synthesis via ASNS and for an effective cell rescue. The model is mainly based on data obtained with prostate cancer cells by Sun et al (27) but it may apply to other low-ASNS cancers.…”

“…Membrane transport can limit cell availability of Asp, which, at the levels present in human plasma, relies on the activity of high-affinity, sodium-dependent EAAT transporters (84,85). A member of the family, EAAT1, coded by SLC1A3, has been identified as an important contributor of resistance to ASNase in several lines of prostate cancer cells (27). In one of these models, although ASNS is heavily induced upon ASNase treatment, cell death is not prevented if EAAT1 is pharmacologically inhibited (27).…”

T-ALL Proliferation Relies on Glutamine Uptake and EAAT1-dependent Conversion of Glutamine to Aspartate and Nucleotides

“…Similar processes are likely to occur in other cancers. Indeed, recently EAAT1 has been implicated in supporting proliferation in several cancer cell lines representing solid cancers [62,63]. Both studies showed a main role for EAAT1 in the uptake of aspartate from the medium, especially under conditions of glutamine deprivation or asparaginase treatment.…”