Abstract
Amino-acid metabolism plays a vital role in mammalian target of rapamycin (mTOR) signaling, which is the pivot in colorectal cancer (CRC). Upregulated chaperone-mediated autophagy (CMA) activity contributes to the regulation of metabolism in cancer cells. Previously, we found that sorting nexin 10 (SNX10) is a critical regulator in CMA activation. Here we investigated the role of SNX10 in regulating amino-acid metabolism and mTOR signaling pathway activation, as well as the impact on the tumor progression of mouse CRC. Our results showed that SNX10 deficiency promoted colorectal tumorigenesis in male FVB mice and CRC cell proliferation and survival. Metabolic pathway analysis of gas chromatography–mass spectrometry (GC-MS) data revealed unique changes of amino-acid metabolism by SNX10 deficiency. In HCT116 cells, SNX10 knockout resulted in the increase of CMA and mTOR activation, which could be abolished by chloroquine treatment or reversed by SNX10 overexpression. By small RNA interference (siRNA), we found that the activation of mTOR was dependent on lysosomal-associated membrane protein type-2A (LAMP-2A), which is a limiting factor of CMA. Similar results were also found in Caco-2 and SW480 cells. Ultra-high-performance liquid chromatography–quadrupole time of flight (UHPLC-QTOF) and GC-MS-based untargeted metabolomics revealed that 10 amino-acid metabolism in SNX10-deficient cells were significantly upregulated, which could be restored by LAMP-2A siRNA. All of these amino acids were previously reported to be involved in mTOR activation. In conclusion, this work revealed that SNX10 controls mTOR activation through regulating CMA-dependent amino-acid metabolism, which provides potential target and strategy for treating CRC.
Highlights
Colorectal cancer (CRC) is the third most commonly diagnosed cancer in males and the second in females, with an estimated 1.4 million cases and 693 900 deaths occurring globally in 20121
Our metabolomics characterization of sorting nexin 10 (SNX10) KO CRC male mice is consistent with the hallmarks of cancer metabolism[20], suggesting that the accumulative amino acids caused by SNX10 KO have profound effect on the CRC cell growth
(see figure on previous page) Fig. 5 Persistent activation of chaperone-mediated autophagy (CMA) degradation caused by SNX10 deficiency activates mammalian target of rapamycin (mTOR) signaling. a Representative western blots showed the expression of indicated proteins in WT and SNX10 KO HCT116 cells with the treatment of Earles balanced salt solution (EBSS) for 24 h
Summary
Colorectal cancer (CRC) is the third most commonly diagnosed cancer in males and the second in females, with an estimated 1.4 million cases and 693 900 deaths occurring globally in 20121. 40% of CRC are diagnosed at early localized stage and the 5-year survival is 13% when the disease has spread to distant organs[3]. The discovery of new therapeutic strategies in CRC treatment is an urgent need and has attracted a great deal of research interest[4,5,6]. Cancer is widely known as a genetic disease, Official journal of the Cell Death Differentiation Association. Le et al Cell Death and Disease (2018)9:666. Autophagy has significant effects on cancer cell survival and may play dual role in carcinogenesis[13]
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