SLC25A21 downregulation promotes KRAS-mutant colorectal cancer progression by increasing glutamine anaplerosis
Sha-Sha Hu, Yue Han, Tian-Yuan Tan, Hui Chen, Jia-Wen Gao, Lan Wang, Min-Hui Yang, Li Zhao, Yi-Qing Wang, Yan-Qing Ding, Shuang Wang
Sha-Sha Hu, Yue Han, Tian-Yuan Tan, Hui Chen, Jia-Wen Gao, Lan Wang, Min-Hui Yang, Li Zhao, Yi-Qing Wang, Yan-Qing Ding, Shuang Wang
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Research Article Gastroenterology Metabolism

SLC25A21 downregulation promotes KRAS-mutant colorectal cancer progression by increasing glutamine anaplerosis

Abstract

Emerging evidence shows that KRAS-mutant colorectal cancer (CRC) depends on glutamine (Gln) for survival and progression, indicating that targeting Gln metabolism may be a promising therapeutic strategy for KRAS-mutant CRC. However, the precise mechanism by which Gln metabolism reprogramming promotes and coordinates KRAS-mutant CRC progression remains to be fully investigated. Here, we discovered that solute carrier 25 member 21 (SLC25A21) expression was downregulated in KRAS-mutant CRC, and that SLC25A21 downregulation was correlated with poor survival of KRAS-mutant CRC patients. SLC25A21 depletion selectively accelerated the growth, invasion, migration, and metastasis of KRAS-mutant CRC cells in vitro and in vivo, and inhibited Gln-derived α-ketoglutarate (α-KG) efflux from mitochondria, thereby potentiating Gln replenishment, accompanied by increased GTP availability for persistent KRAS activation in KRAS-mutant CRC. The restoration of SLC25A21 expression impaired the KRAS-mutation-mediated resistance to cetuximab in KRAS-mutant CRC. Moreover, the arrested α-KG efflux that occurred in response to SLC25A21 depletion inhibited the activity of α-KG–dependent DNA demethylases, resulting in a further decrease in SLC25A21 expression. Our studies demonstrate that SLC25A21 plays a significant role as a tumor suppressor in KRAS-mutant CRC by antagonizing Gln-dependent anaplerosis to limit GTP availability for KRAS activation, which suggests potential alternative therapeutic strategies for KRAS-mutant CRC.

Authors

Sha-Sha Hu, Yue Han, Tian-Yuan Tan, Hui Chen, Jia-Wen Gao, Lan Wang, Min-Hui Yang, Li Zhao, Yi-Qing Wang, Yan-Qing Ding, Shuang Wang

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Figure 4

SLC25A21 downregulation promotes glutaminolysis by restricting Gln-derived α-KG efflux to replenish the TCA cycle in KRAS-mutant CRC cells.

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SLC25A21 downregulation promotes glutaminolysis by restricting Gln-deriv...
(A) Relative subcellular α-KG levels in CRC cells with and without SLC25A21 knockdown (n = 3 biologically independent experiments). (B) Diagram of Gln catabolic pathway using [U-13C5]Gln as a tracer (red) (upper) and relative abundances of labeled intracellular metabolites in HCT116 cells determined by LC-MS (bottom; n = 5 biologically independent samples). (C) Representative images (upper) and quantification (bottom) showing the colony-forming capacity of CRC cells with or without KRAS mutation cultured in medium under Gln-containing, Gln-free, and various α-KG–supplemented conditioned medium, treated as shown (n = 3 biologically independent experiments). Gln+, full medium containing Gln (2 mM); Gln–, Gln-free medium; Gln– + α-KG, Gln-free medium with various contents of dm-KG (cell-permeable analog of α-KG). (D) Representative images (upper) and quantification (bottom) of the colony-forming capacity of KRAS-mutant CRC cells with or without SLC25A21 overexpression cultured under the indicated condition, treated as shown (n = 3 biologically independent experiments). (E) Heatmap showing the relative levels of subcellular α-KG in KRAS-mutant CRC cells from D, treated as shown (n = 3 biologically independent experiments). Gln+, full medium containing Gln (Gln 2 mM); α-KG+, 2 mM α-KG; Gln–, Gln-free medium; A21-OE, SLC25A21 overexpression. (F) Relative levels of ATP and ROS and relative ratio of NADP+/NADPH in CRC cells with or without SLC25A21 knockdown (n = 3 biologically independent experiments). Data are presented as the mean ± SD. Statistical significance was calculated by unpaired, 2-sided t test (A, B, D, and F) and 1-way ANOVA with Tukey‘s post hoc test (C). *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.