Cancer stem cells synthesize proline to attenuate oxidative stress
Weichi Wu, Po Zhang, Donghai Wang, Xujia Wu, Qiulian Wu, Daqi Li, Tengfei Huang, Rui Wang, Huan Li, Hailong Mi, Suchet Taori, Fanen Yuan, Tingting Duan, Zhiye Chen, Huairui Yuan, Jeremy N. Rich
Weichi Wu, Po Zhang, Donghai Wang, Xujia Wu, Qiulian Wu, Daqi Li, Tengfei Huang, Rui Wang, Huan Li, Hailong Mi, Suchet Taori, Fanen Yuan, Tingting Duan, Zhiye Chen, Huairui Yuan, Jeremy N. Rich
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Research Article Cell biology Metabolism Oncology

Cancer stem cells synthesize proline to attenuate oxidative stress

Abstract

Cancers reprogram their metabolism to provide anabolic needs without driving excessive oxidative stress. Attention has focused on glucose metabolism, yet amino acid synthesis and degradation also promote tumor cell states and growth. Here, we assessed amino acids that maintain cancer stem cells in glioblastoma and found increased proline levels relative to differentiated tumor progeny through increased proline synthesis. Cancer stem cells preferentially expressed the signaling molecule FAM3C induced by the stem cell transcription factor SOX2 to drive expression of proline synthesis enzymes. FAM3C classically mediated cellular responses as a secreted protein but gained intracellular functions in cancer stem cells through binding the histone reader spindlin 1 (SPIN1), thereby preventing its lysosomal degradation, assisting its nuclear localization, and promoting epigenetic regulation of proline synthesis. Proline synthesis depleted ROS, and genetic targeting of FAM3C attenuated ROS scavenging, whereas SPIN1 OE restored ROS levels. Molecular docking identified tucatinib as a brain-penetrant pharmacologic disruptor of FAM3C-SPIN1 interactions, promoting SPIN1 degradation and reducing intracellular proline levels. Thus, cancer stem cells induced a favorable metabolic state through proline synthesis and ROS depletion, revealing potential therapeutic dependencies.

Authors

Weichi Wu, Po Zhang, Donghai Wang, Xujia Wu, Qiulian Wu, Daqi Li, Tengfei Huang, Rui Wang, Huan Li, Hailong Mi, Suchet Taori, Fanen Yuan, Tingting Duan, Zhiye Chen, Huairui Yuan, Jeremy N. Rich

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Figure 1

GSCs upregulate proline biosynthesis and proline-related genes.

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GSCs upregulate proline biosynthesis and proline-related genes. (A) Summ...
(A) Summary of intracellular amino acid levels across GSCs and DGCs from 5 biological replicates (12). The fold changes (FCs) in amino acid levels relative to the average of GSCs are displayed. Statistical analysis was determined by 2-tailed, unpaired t test. (B) Summary of intracellular proline levels across GSCs and NSCs from 5 biological replicates (12). Data are presented as the mean ± SD. Statistical significance was determined by 1-way ANOVA followed by a multiple-comparison test. (C) Schematic of the proline biosynthesis pathway in mitochondria. (D–F) P5C (D), NAD+ (E), and proline (F) detected by LC-MS in 2 CD133+ GSC lines and paired CD133– DGCs (n = 4 independent experiments) (21). Data are presented as the mean ± SD. Statistical significance was determined by 2-tailed, unpaired t test. (G–I) H3K27ac ChIP-seq tracks at ALDH18A1 (P5CS) (G), PYCR1 (H), and PYCR2 (I) gene loci (GSE129438). (J) Summary of gene expression in matched GSCs and DGCs (GSE54791). (K) GSEA of arginine and proline metabolism among DEGs from matched GSCs and DGCs. Normalized enrichment score (ES) and nominal P values are shown. (L) Immunoblot analysis of matched GSCs and DGCs.