Theranostics 2020; 10(2):516-536. doi:10.7150/thno.37472

Research Paper

ANKRD22, a novel tumor microenvironment-induced mitochondrial protein promotes metabolic reprogramming of colorectal cancer cells

Tianhui Pan1*, Jingwen Liu1*, Song Xu1, Qiao Yu1, Hongping Wang1, Hongxiang Sun3, Jia Wu1, Yue Zhu5, Jianwei Zhou2✉, Yongliang Zhu1,4✉

1. Laboratory of Gastroenterology Department, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China;
2. Gynecology Department, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China;
3. Laboratory of Natural Drug, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China;
4. Key Laboratory of Tumor Microenviroment and Immune Therapy of Zhejiang Province, Hangzhou, Zhejiang 310009, China.
5. College of Stormotologry, Wenzhou Medical University, Zhejiang325035, China.
* These two authors contributed equally to this work.

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Citation:
Pan T, Liu J, Xu S, Yu Q, Wang H, Sun H, Wu J, Zhu Y, Zhou J, Zhu Y. ANKRD22, a novel tumor microenvironment-induced mitochondrial protein promotes metabolic reprogramming of colorectal cancer cells. Theranostics 2020; 10(2):516-536. doi:10.7150/thno.37472. Available from http://www.thno.org/v10p0516.htm

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Abstract

Background: The leading cause of poor prognosis in colorectal cancer (CRC) is the presence of colorectal cancer-initiating cells (CCICs). The interplay between the tumor microenvironment (TME) and CRC cells induces reacquisition of initiating cell characteristics, but the underlying mechanisms remain elusive.

Methods: Candidate molecules were screened by global differential cDNA expression profiles of CCICs, which were enriched from patient-derived tumor xenograft models. Luciferase reporters and chromatin immunoprecipitation assays were used to explore the mechanism of TME factors regulating the transcription of ANKRD22. The effects of Ankyrin repeat domain-containing protein 22 (ANKRD22) on energy metabolism were monitored by extracellular flux and 13C-based metabolic flux analysis. Mass spectrometry was used to identify the interacting partners of ANKRD22. Morphological changes of CCICs overexpressing ANKRD22 were observed by electron microscopy. The effects of ANKRD22 on mitochondrial lipid metabolism were analyzed by lipidomics.

Results: We identified a novel nucleus-encoded mitochondrial membrane protein, ANKRD22, which was upregulated in CCICs. We found that ANKRD22 was induced by the p38/MAX pathway activated by different TME stimuli. As a key transcription factor, MAX promoted the transcription of ANKRD22. Expression of ANKRD22 promoted glycolysis associated with a decrease in ATP/ADP and an increase in AMP/ATP levels, which were related to its interaction with pyruvate dehydrogenase kinase isoform 1 (PDK1) and multiple subunits of ATP synthase. Further, in CCICs, ANKRD22 cooperated with the lipid transport protein, Extended Synaptotagmin-1 (E-Syt1), to transport excess lipids into mitochondria and reduced the number of mitochondria in an autophagy-independent manner, thus meeting the metabolic requirements of CCICs.

Conclusion: ANKRD22 induced by TME promotes the metabolic reprogramming of CRC cells. Our study has identified ANKRD22/E-Syt1 as a potential target for eradicating CCICs.

Keywords: Colorectal cancer, Tumor microenvironment, Cancer-initiating cells, ANKRD22, Metabolic reprogramming