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 5

FAM3C regulates SPIN1 stability and nuclear translocation to fuel proline biosynthesis.

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FAM3C regulates SPIN1 stability and nuclear translocation to fuel prolin...
(A) Immunoblot analysis of SPIN1 and FAM3C expression in GSCs (GSC23 and GSC387) with or without FAM3C KD, with or without SPIN1 OE, or in combination with FAM3C KD and SPIN1 OE. (B and C) Relative intracellular proline levels (n = 5 biologically independent samples) in GSC23 (B) and GSC387 (C) GSCs under the different treatment conditions in A. Data are presented as the mean ± SD. Statistical analysis between shCONT and SPIN1-OE was performed using a 2-tailed, unpaired t test. Statistical analysis between shFAM3C and shFAM3C plus SPIN1-OE was performed using ordinary 1-way ANOVA. (D and E) Immunoblot analysis of SPIN1 and FAM3C expression of GSC23 (D) and GSC387 (E) GSCs with or without FAM3C KD, after treatment with chloroquine to inhibit lysosomal degradation. (F) Representative images of SPIN1 (green) and a lysosomal marker, LAMP1 (red), in GSC23 GSCs. DAPI (blue). Scale bars: 10 μm. (G) Schematic diagram of the interaction between FAM3C and SPIN1 proteins to prevent the lysosomal degradation of SPIN1 and promote the nuclear localization of SPIN1.