Jen-Tsan Ashley Chi, MD, PhD

Associate Professor in Molecular Genetics and Microbiology
Assistant Professor of Medicine
Assistant Professor in Radiation Oncology
Associate Professor of Pharmacology and Cancer Biology
Member of the Duke Cancer Institute
Campus mail 101 Science Dr, Dumc3382, Room 2177A, CIEMAS Bldg, Durham, NC 27708
Phone (919) 668-4759
Email address jentsan.chi@duke.edu

We are using functional genomic approaches to investigate the nutrient signaling and stress adaptations of cancer cells when exposed to various nutrient deprivations and microenvironmental stress conditions. Recently, we focus on two areas. First, we are elucidating the genetic determinants and disease relevance of ferroptosis, a newly recognized form of cell death. Second, we have identified the mammalian stringent response pathway which is highly similar to bacterial stringent response, but with some very interesting twists and novel mechanisms.

A. The genetic determinants and disease relevance of ferroptosis

Ferroptosis is a newly recognized form of cell death that is characterized by iron dependency and lipid peroxidation. The importance of ferroptosis is being recognized in many human diseases, including cancers, ischemia injuries, and neurodegeneration. Previously, we have identified the profound cystine addiction of renal cell carcinoma (1), breast cancer cells (2, 3), and ovarian cancer cells (4). Based on the concept that cystine deprivation triggers the ferroptosis due to the unopposed oxidative stresses, we have performed functional genomic screens to identify many novel genetic determinants of ferroptosis. For example, we have found that DNA damage response and ATM kinase regulate ferroptosis via affecting iron metabolism (5). This finding supports the potential of ionizing radiation to trigger DNA damage response and synergize with ferroptosis to treat human cancers. In addition, we found that ferroptosis is highly regulated by cell density. When cells are grown at low density, they are highly susceptible to ferroptosis. In contrast, the same cells become resistant to ferroptosis when grown at high density and confluency. we have found the Hippo pathway effectors TAZ and YAP are responsible for the cell density-dependent ferroptosis (4, 6, 7). Right now, we are pursuing several other novel determinants of ferroptosis that will reveal surprising insights into this new form of cell death.

B. A new stress pathway – mammalian stress response

All living organisms encounter a wide variety of nutrient deprivations and environmental stresses. Therefore, all organisms have developed various mechanisms to respond and promote survival under stress. In bacteria, the main strategy is “stringent response” triggered by the accumulation of the alarmone (p)ppGpp (shortened to ppGpp below) via regulation of its synthetase RelA and its hydrolase SpoT (8). The ppGpp binds to the transcription factor DksA and RNA polymerase to orchestrate extensive transcriptional changes that repress proliferation and promote stress survival (8, 9). While highly conserved among bacteria, the stringent response had not been reported in metazoans. However, a recent study identified Drosophila and human MESH1 (Metazoan SpoT Homolog 1) as the homologs of the ppGpp hydrolase domain of the bacterial SpoT (10). Both MESH1 proteins exhibit ppGpp hydrolase activity, and the deletion of Mesh1 in Drosophila led to a transcriptional response reminiscent of the bacterial stringent response (10). Recently, we have found that the genetic removal of MESH1 in tumor cells triggers extensive transcriptional changes and confers protection against oxidative stress-induced ferroptosis (11). Importantly, MESH1 removal also triggers proliferative arrest and other robust anti-tumor effects. Therefore, MESH1 knockdown leads to both stress survival and proliferation arrest, two cardinal features highly reminiscent of the bacterial stringent response. Therefore, we termed this pathway as “mammalian stringent response” (12). We have found that NADPH is the relevant MESH1 in the contexts of ferroptosis (13). Now, we are investigating how MESH1 removal leads to proliferation of arrests and anti-tumor phenotypes. Furthermore, we have found several other substrates of MESH1. We are investigating their function using culture cells, MESH1 KO mice, and other model organisms.

 

C. Genomic and single cell RNA analysis of Red Blood Cells

Red blood cells (RBC) are responsible for oxygen delivery to muscles during vigorous exercise. Therefore, many doping efforts focus on increasing RBC number and function to boost athletic performance during competition. For many decades, RBC were thought to be merely identical “sacs of hemoglobin” with no discernable differences due to factors such as age or pre-transfusion storage time. Additionally, because RBC lose their nuclei during terminal differentiation, they were not believed to retain any genetic materials.  These long-held beliefs have now been disproven and the results have significant implications for detecting autologous blood transfusion (ABT) doping in athletes.  We were among the first to discover that RBCs contain abundant and diverse species of RNAs. Using this knowledge, we subsequently optimized protocols and performed genomic analysis of the RBC transcriptome in sickle cell disease; these results revealed that heterogeneous RBCs could be divided into several subpopulations, which had implications for the mechanisms of malaria resistance. As an extension of these studies, we used high resolution Illumina RNA-Seq approaches to identify hundreds of additional known and novel microRNAs, mRNAs, and other RNA species in RBCs. This dynamic RBC transcriptome represents a significant opportunity to assess the impact that environmental factors (such as pre-transfusion refrigerate storage) on the RBC transcriptome. We have now identified a >10-fold change in miR-720 as well as several other RNA transcripts whose levels are significantly altered by RBC storage (14) which gained significant press coverage. We are pursuing the genomic and single cell analysis of RNA transcriptome in the context of blood doping, sickle cell diseases and other red cell diseases.

 

 

 

 

1.         Tang X, Wu J, Ding CK, Lu M, Keenan MM, Lin CC, et al. Cystine Deprivation Triggers Programmed Necrosis in VHL-Deficient Renal Cell Carcinomas. Cancer Res. 2016;76(7):1892-903.

2.         Tang X, Ding CK, Wu J, Sjol J, Wardell S, Spasojevic I, et al. Cystine addiction of triple-negative breast cancer associated with EMT augmented death signaling. Oncogene. 2017;36(30):4379.

3.         Lin CC, Mabe NW, Lin YT, Yang WH, Tang X, Hong L, et al. RIPK3 upregulation confers robust proliferation and collateral cystine-dependence on breast cancer recurrence. Cell Death Differ. 2020.

4.         Yang WH, Huang Z, Wu J, Ding C-KC, Murphy SK, Chi J-T. A TAZ-ANGPTL4-NOX2 axis regulates ferroptotic cell death and chemoresistance in epithelial ovarian cancer. Molecular Cancer Research. 2019: molcanres.0691.2019.

5.         Chen PH, Wu J, Ding CC, Lin CC, Pan S, Bossa N, et al. Kinome screen of ferroptosis reveals a novel role of ATM in regulating iron metabolism. Cell Death Differ. 2019.

6.         Yang W-H, Chi J-T. Hippo pathway effectors YAP/TAZ as novel determinants of ferroptosis. Molecular & Cellular Oncology. 2019:1699375.

7.         Yang WH, Ding CKC, Sun T, Hsu DS, Chi JT. The Hippo Pathway Effector TAZ Regulates Ferroptosis in Renal Cell Carcinoma Cell Reports. 2019;28(10):2501-8.e4.

8.         Potrykus K, Cashel M. (p)ppGpp: still magical? Annu Rev Microbiol. 2008;62:35-51.

9.         Kriel A, Bittner AN, Kim SH, Liu K, Tehranchi AK, Zou WY, et al. Direct regulation of GTP homeostasis by (p)ppGpp: a critical component of viability and stress resistance. Mol Cell. 2012;48(2):231-41.

10.       Sun D, Lee G, Lee JH, Kim HY, Rhee HW, Park SY, et al. A metazoan ortholog of SpoT hydrolyzes ppGpp and functions in starvation responses. Nat Struct Mol Biol. 2010;17(10):1188-94.

11.       Dixon SJ, Lemberg KM, Lamprecht MR, Skouta R, Zaitsev EM, Gleason CE, et al. Ferroptosis: an iron-dependent form of nonapoptotic cell death. Cell. 2012;149(5):1060-72.

12.       Ding C-KC, Rose J, Wu J, Sun T, Chen K-Y, Chen P-H, et al. Mammalian stringent-like response mediated by the cytosolic NADPH phosphatase MESH1. bioRxiv. 2018.

13.       Ding C-KC, Rose J, Sun T, Wu J, Chen P-H, Lin C-C, et al. MESH1 is a cytosolic NADPH phosphatase that regulates ferroptosis. Nature Metabolism. 2020.

14.       Yang WH, Doss JF, Walzer KA, McNulty SM, Wu J, Roback JD, et al. Angiogenin-mediated tRNA cleavage as a novel feature of stored red blood cells. Br J Haematol. 2018.

 

 

Education and Training

  • Postdoctoral Research, Biochemistry, Stanford University, 2000 - 2004
  • Ph.D., Stanford University, 2000
  • M.D., National Taiwan University (Taiwan), 1991

Publications

Mestre, Alexander A., Pei Zhou, and Jen-Tsan Chi. “Metazoan stringent-like response mediated by MESH1 phenotypic conservation via distinct mechanisms.” Computational and Structural Biotechnology Journal, May 2022. https://doi.org/10.1016/j.csbj.2022.05.001.

Full Text

Chi, Jen-Tsan, Pao-Hwa Lin, Vladimir Tolstikov, Lauren Howard, Emily Y. Chen, Valerie Bussberg, Bennett Greenwood, Niven R. Narain, Michael A. Kiebish, and Stephen J. Freedland. “Serum metabolomic analysis of men on a low-carbohydrate diet for biochemically recurrent prostate cancer reveals the potential role of ketogenesis to slow tumor growth: a secondary analysis of the CAPS2 diet trial.” Prostate Cancer Prostatic Dis, March 25, 2022. https://doi.org/10.1038/s41391-022-00525-6.

PMID
35338353
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Sun, Tianai, Chien-Kuang Cornelia Ding, Yuning Zhang, Yang Zhang, Chao-Chieh Lin, Jianli Wu, Yasaman Setayeshpour, et al. “MESH1 knockdown triggers proliferation arrest through TAZ repression.” Cell Death Dis 13, no. 3 (March 10, 2022): 221. https://doi.org/10.1038/s41419-022-04663-6.

PMID
35273140
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Schirmer, Amelia U., Lucy M. Driver, Megan T. Zhao, Carrow I. Wells, Julie E. Pickett, Sean N. O’Bryne, Benjamin J. Eduful, et al. “Non-canonical role of Hippo tumor suppressor serine/threonine kinase 3 STK3 in prostate cancer.” Mol Ther 30, no. 1 (January 5, 2022): 485–500. https://doi.org/10.1016/j.ymthe.2021.08.029.

PMID
34450249
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Chi, Jen-Tsan, Pao-Hwa Lin, Vladimir Tolstikov, Lauren Howard, Emily Chen, Valerie Bussberg, Bennett Greenwood, Niven Narain, Michael Kiebish, and Stephen Freedland. “Serum metabolomic analysis of men on a low-carbohydrate diet for biochemically recurrent prostate cancer reveal the potential role of ketogenesis to slow tumor growth: A secondary analysis of the CAPS2 diet trial,” January 3, 2022. https://doi.org/10.1101/2021.12.29.474437.

Full Text

Jain, Vaibhav, Wen-Hsuan Yang, Jianli Wu, John D. Roback, Simon G. Gregory, and Jen-Tsan Chi. “Single Cell RNA-Seq Analysis of Human Red Cells.” Frontiers in Physiology 13 (January 2022): 828700. https://doi.org/10.3389/fphys.2022.828700.

PMID
35514346
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Park, Han-Sang, Hillel Price, Silvia Ceballos, Jen-Tsan Chi, and Adam Wax. “Single Cell Analysis of Stored Red Blood Cells Using Ultra-High Throughput Holographic Cytometry.” Cells 10, no. 9 (September 17, 2021). https://doi.org/10.3390/cells10092455.

PMID
34572104
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Du, Kuo, Seh Hoon Oh, Rajesh K. Dutta, Tianai Sun, Wen-Hsuan Yang, Jen-Tsan Chi, and Anna Mae Diehl. “Inhibiting xCT/SLC7A11 induces ferroptosis of myofibroblastic hepatic stellate cells but exacerbates chronic liver injury.” Liver Int 41, no. 9 (September 2021): 2214–27. https://doi.org/10.1111/liv.14945.

PMID
33991158
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Lin, Chao-Chieh, Chien-Kuang Cornelia Ding, Tianai Sun, Jianli Wu, Kai-Yuan Chen, Pei Zhou, and Jen-Tsan Chi. “The regulation of ferroptosis by MESH1 through the activation of the integrative stress response.” Cell Death Dis 12, no. 8 (July 22, 2021): 727. https://doi.org/10.1038/s41419-021-04018-7.

PMID
34294679
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Moon, Eui Jung, Stephano S. Mello, Caiyun G. Li, Jen-Tsan Chi, Kaushik Thakkar, Jacob G. Kirkland, Edward L. Lagory, et al. “The HIF target MAFF promotes tumor invasion and metastasis through IL11 and STAT3 signaling.” Nat Commun 12, no. 1 (July 14, 2021): 4308. https://doi.org/10.1038/s41467-021-24631-6.

PMID
34262028
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