Li Guan

All Publications

• Targeted proteomic quantitation of NRF2 signaling and predictive biomarkers in HNSCC. Molecular & cellular proteomics : MCP Wamsley, N. T., Wilkerson, E. M., Guan, L., LaPak, K. M., Schrank, T. P., Holmes, B. J., Sprung, R. W., Gilmore, P. E., Gerndt, S. P., Jackson, R. S., Paniello, R. C., Pipkorn, P., Puram, S. V., Rich, J. T., Townsend, R. R., Zevallos, J. P., Zolkind, P., Le, Q. T., Goldfarb, D., Ben Major, M. 2023: 100647

  Abstract

  The NFE2L2(NRF2) oncogene and transcription factor drives a gene expression program that promotes cancer progression, metabolic reprogramming, immune evasion and chemoradiation resistance. Patient stratification by NRF2 activity may guide treatment decisions to improve outcome. Here, we developed a mass spectrometry (MS)-based targeted proteomics assay based on internal standard triggered parallel reaction monitoring (IS-PRM) to quantify 69 NRF2 pathway components and targets, as well as 21 proteins of broad clinical significance in head and neck squamous cell carcinoma (HNSCC). We improved an existing IS-PRM acquisition algorithm, called SureQuantTM, to increase throughput, sensitivity, and precision. Testing the optimized platform on 27 lung and upper aerodigestive cancer cell models revealed 35 NRF2 responsive proteins. In formalin-fixed paraffin-embedded (FFPE) HNSCCs, NRF2 signaling intensity positively correlated with NRF2 activating mutations and with SOX2 protein expression. Protein markers of T-cell infiltration correlated positively with one another and with human papilloma virus (HPV) infection status. CDKN2A (p16) protein expression positively correlated with the HPV oncogenic E7 protein, and confirmed the presence of translationally active virus. This work establishes a clinically actionable HNSCC protein biomarker assay capable of quantifying over 600 peptides from frozen or FFPE archived tissues in under 90 minutes.

  View details for DOI 10.1016/j.mcpro.2023.100647

  View details for PubMedID 37716475

• Galectin-1 mediates chronic STING activation in tumors to promote metastasis through MDSC recruitment. Cancer research Nambiar, D. K., Viswanathan, V., Cao, H., Zhang, W., Guan, L., Chamoli, M., Holmes, B., Kong, C., Hildebrand, R., Koong, A. J., von Eyben, R., Plevritis, S., Li, L., Giaccia, A., Engleman, E., Le, Q. T. 2023

  Abstract

  The immune system plays a crucial role in the regulation of metastasis. Tumor cells systemically change immune functions to facilitate metastatic progression. Through this study, we deciphered how tumoral Galectin-1 (Gal1) expression shapes the systemic immune environment to promote metastasis in head and neck cancer (HNC). In multiple preclinical models of HNC and lung cancer in immunogenic mice, Gal1 fostered the establishment of a pre-metastatic niche through polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), which altered the local microenvironment to support metastatic spread. RNA sequencing of MDSCs from pre-metastatic lungs in these models demonstrated the role of PMN-MDSCs in collagen and extracellular matrix remodeling in the pre-metastatic compartment. Gal1 promoted MDSC accumulation in the pre-metastatic niche through the NF-κB signaling axis, triggering enhanced CXCL2-mediated MDSC migration. Mechanistically, Gal1 sustained NF-κB activation in tumor cells by enhancing STING protein stability, leading to prolonged inflammation-driven MDSC expansion. These findings suggest an unexpected pro-tumoral role of STING activation in metastatic progression and establish Gal1 as an endogenous positive regulator of STING in advanced-stage cancers.

  View details for DOI 10.1158/0008-5472.CAN-23-0046

  View details for PubMedID 37409887

• Association between locoregional failure and NFE2L2/KEAP1/CUL3 pathway mutations in NRG/RTOG 9512: A randomized trial of hyperfractionation vs. conventional fractionation in T2N0 glottic squamous cell carcinoma (SCC). Guan, L., Torres-Saavedra, P. A., Zhao, X., Major, M. B., Holmes, B. J., Nguyen, N., Kumaravelu, P., Hodge, T., Diehn, M., Zevallos, J., Emami, B., Sagar, S. M., Morrison, W. H., Schultz, C. J., Caudell, J. J., Jones, C. U., Yom, S. S., Harris, J., Le, Q., Hayes, D. N. LIPPINCOTT WILLIAMS & WILKINS. 2023

  View details for Web of Science ID 001053772003175

• NFE2L2 mutations enhance radioresistance in head and neck cancer by modulating intratumoral myeloid cells. Cancer research Guan, L., Nambiar, D. K., Cao, H., Viswanathan, V., Kwok, S., Hui, A. B., Hou, Y., Hildebrand, R., von Eyben, R., Holmes, B. J., Zhao, J., Kong, C. S., Wamsley, N., Zhang, W., Major, M. B., Seol, S. W., Sunwoo, J. B., Hayes, D. N., Diehn, M., Le, Q. T. 2023

  Abstract

  Radiotherapy is one of the primary treatments of head and neck squamous cell carcinoma (HNSCC), which has a high risk of locoregional failure (LRF). Presently, there is no reliable predictive biomarker of radioresistance in HNSCC. Here, we found that mutations in NFE2L2, which encodes Nrf2, are associated with a significantly higher rate of LRF in patients with oral cavity cancer treated with surgery and adjuvant (chemo)radiotherapy but not in those treated with surgery alone. Somatic mutation of NFE2L2 led to Nrf2 activation and radioresistance in HNSCC cells. Tumors harboring mutant Nrf2E79Q were substantially more radioresistant than tumors with wild-type Nrf2 in immunocompetent mice, while the difference was diminished in immunocompromised mice. Nrf2E79Q enhanced radioresistance through increased recruitment of intratumoral polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) and reduction of M1-polarized macrophages. Treatment with the glutaminase inhibitor CB-839 overcame the radioresistance induced by Nrf2E79Q or Nrf2E79K. Radiotherapy increased expression of PMN-MDSC-attracting chemokines, including CXCL1, CXLC3 and CSF3, in Nrf2E79Q-expressing tumors via the TLR4, which could be reversed by CB-839. This study provides insights into the impact of NFE2L2 mutations on radioresistance and suggests that CB-839 can increase radiosensitivity by switching intratumoral myeloid cells to an anti-tumor phenotype, supporting clinical testing of CB-839 with radiation in HNSCC with NFE2L2 mutations.

  View details for DOI 10.1158/0008-5472.CAN-22-1903

  View details for PubMedID 36652552

• The BRCA1 BRCT promotes antisense RNA production and double-stranded RNA formation to suppress ribosomal R-loops. Proceedings of the National Academy of Sciences of the United States of America Chang, C. W., Singh, A. K., Li, M., Guan, L., Le, N., Omabe, K., Liang, F., Liu, Y. 2022; 119 (50): e2217542119

  Abstract

  R-loops, or RNA:DNA hybrids, can induce DNA damage, which requires DNA repair factors including breast cancer type 1 susceptibility protein (BRCA1) to restore genomic integrity. To date, several pathogenic mutations have been found within the tandem BRCA1 carboxyl-terminal (BRCT) domains that mediate BRCA1 interactions with proteins and DNA in response to DNA damage. Here, we describe a nonrepair role of BRCA1 BRCT in suppressing ribosomal R-loops via two mechanisms. Through its RNA binding and annealing activities, BRCA1 BRCT facilitates the formation of double-stranded RNA between ribosomal RNA (rRNA) and antisense-rRNA (as-rRNA), hereby minimizing rRNA hybridization to ribosomal DNA to form R-loops. BRCA1 BRCT also promotes RNA polymerase I-dependent transcription of as-rRNA to enhance double-stranded rRNA (ds-rRNA) formation. In addition, BRCA1 BRCT-mediated as-rRNA production restricts rRNA maturation in unperturbed cells. Hence, impairing as-rRNA transcription and ds-rRNA formation due to BRCA1 BRCT deficiency deregulates rRNA processing and increases ribosomal R-loops and DNA breaks. Our results link ribosomal biogenesis dysfunction to BRCA1-associated genomic instability.

  View details for DOI 10.1073/pnas.2217542119

  View details for PubMedID 36490315

• Aldehyde dehydrogenase 3A1 deficiency leads to mitochondrial dysfunction and impacts salivary gland stem cell phenotype. PNAS nexus Viswanathan, V., Cao, H., Saiki, J., Jiang, D., Mattingly, A., Nambiar, D., Bloomstein, J., Li, Y., Jiang, S., Chamoli, M., Sirjani, D., Kaplan, M., Holsinger, F. C., Liang, R., Von Eyben, R., Jiang, H., Guan, L., Lagory, E., Feng, Z., Nolan, G., Ye, J., Denko, N., Knox, S., Rosen, D., Le, Q. 2022; 1 (2): pgac056

  Abstract

  Adult salivary stem/progenitor cells (SSPC) have an intrinsic property to self-renew in order to maintain tissue architecture and homeostasis. Adult salivary glands have been documented to harbor SSPC, which have been shown to play a vital role in the regeneration of the glandular structures postradiation damage. We have previously demonstrated that activation of aldehyde dehydrogenase 3A1 (ALDH3A1) after radiation reduced aldehyde accumulation in SSPC, leading to less apoptosis and improved salivary function. We subsequently found that sustained pharmacological ALDH3A1 activation is critical to enhance regeneration of murine submandibular gland after radiation damage. Further investigation shows that ALDH3A1 function is crucial for SSPC self-renewal and survival even in the absence of radiation stress. Salivary glands from Aldh3a1 -/- mice have fewer acinar structures than wildtype mice. ALDH3A1 deletion or pharmacological inhibition in SSPC leads to a decrease in mitochondrial DNA copy number, lower expression of mitochondrial specific genes and proteins, structural abnormalities, lower membrane potential, and reduced cellular respiration. Loss or inhibition of ALDH3A1 also elevates ROS levels, depletes glutathione pool, and accumulates ALDH3A1 substrate 4-hydroxynonenal (4-HNE, a lipid peroxidation product), leading to decreased survival of murine SSPC that can be rescued by treatment with 4-HNE specific carbonyl scavengers. Our data indicate that ALDH3A1 activity protects mitochondrial function and is important for the regeneration activity of SSPC. This knowledge will help to guide our translational strategy of applying ALDH3A1 activators in the clinic to prevent radiation-related hyposalivation in head and neck cancer patients.

  View details for DOI 10.1093/pnasnexus/pgac056

  View details for PubMedID 35707206

• Relationship between KEAP1/NFE2L2 pathway activation and radiation resistance in oral cavity cancer. Guan, L., Cao, H., Hui, A., Kwok, S., Viswanathan, V., Nambiar, D., Eyben, R. V., Holmes, B., Kong, C., Diehn, M., Quynh-Thu Le AMER ASSOC CANCER RESEARCH. 2021

  View details for Web of Science ID 000641160600094

• Geminin facilitates FoxO3 deacetylation to promote breast cancer cell metastasis JOURNAL OF CLINICAL INVESTIGATION Zhang, L., Cai, M., Gong, Z., Zhang, B., Li, Y., Guan, L., Hou, X., Li, Q., Liu, G., Xue, Z., Yang, M., Ye, J., Chin, Y., You, H. 2017; 127 (6): 2159–75

  Abstract

  Geminin expression is essential for embryonic development and the maintenance of chromosomal integrity. In spite of this protective role, geminin is also frequently overexpressed in human cancers and the molecular mechanisms underlying its role in tumor progression remain unclear. The histone deacetylase HDAC3 modulates transcription factors to activate or suppress transcription. Little is known about how HDAC3 specifies substrates for modulation among highly homologous transcription factor family members. Here, we have demonstrated that geminin selectively couples the transcription factor forkhead box O3 (FoxO3) to HDAC3, thereby specifically facilitating FoxO3 deacetylation. We determined that geminin-associated HDAC3 deacetylates FoxO3 to block its transcriptional activity, leading to downregulation of the downstream FoxO3 target Dicer, an RNase that suppresses metastasis. Breast cancer cells depleted of geminin or HDAC3 exhibited poor metastatic potential that was attributed to reduced suppression of the FoxO3-Dicer axis. Moreover, elevated levels of geminin, HDAC3, or both together with decreased FoxO3 acetylation and reduced Dicer expression were detected in aggressive human breast cancer specimens. These results underscore a prominent role for geminin in promoting breast cancer metastasis via the enzyme-substrate-coupling mechanism in HDAC3-FoxO3 complex formation.

  View details for DOI 10.1172/JCI90077

  View details for Web of Science ID 000402620800016

  View details for PubMedID 28436938

  View details for PubMedCentralID PMC5451250

• FoxO3 Inactivation Promotes Human Cholangiocarcinoma Tumorigenesis and Chemoresistance Through Keap1-Nrf2 Signaling HEPATOLOGY Guan, L., Zhang, L., Gong, Z., Hou, X., Xu, Y., Feng, X., Wang, H., You, H. 2016; 63 (6): 1914–27

  Abstract

  FoxO transcription factors have been reported to play pivotal roles in tumorigenesis and drug resistance. The mechanisms underlying the tumor suppression function of FoxOs in human cancers remain largely unknown. Aberrant expression and activation of Nrf2 often correlate with chemoresistance and poor prognosis. Here, we report that FoxO3 directs the basal transcription of Kelch-like ECH-associated protein 1 (Keap1), an adaptor protein that bridges Nrf2 to Cul3 for degradation. FoxO3 depletion resulted in Keap1 down-regulation, thereby activating Nrf2 signaling. We further demonstrated that inhibition of the FoxO3-Keap1 axis accounts for Nrf2 induction and activation induced by constitutively active AKT signaling or tumor necrosis factor α treatment. Unlike previous findings, FoxO3 silencing led to decreased reactive oxygen species production, therefore protecting cells from oxidative stress-induced killing in an Nrf2-dependent manner. Importantly, FoxO3 deficiency strongly potentiated tumor formation in nude mice and rendered cholangiocarcinoma xenografts resistant to cisplatin-induced cell death by activating Nrf2. Additionally, we found that clinical cholangiocarcinoma samples displayed FoxO3-Keap1 down-regulation and Nrf2 hyperactivation, underscoring the essential roles of these proteins in cholangiocarcinoma development.Our results unravel a unique mechanism underlying the tumor suppressor function of FoxO3 through constraining Nrf2 signaling. (Hepatology 2016;63:1914-1927).

  View details for DOI 10.1002/hep.28496

  View details for Web of Science ID 000376361800019

  View details for PubMedID 26857210

• Chaperone-mediated autophagy prevents apoptosis by degrading BBC3/PUMA AUTOPHAGY Xie, W., Zhang, L., Jiao, H., Guan, L., Zha, J., Li, X., Wu, M., Wang, Z., Han, J., You, H. 2015; 11 (9): 1623–35

  Abstract

  Autophagy is a potentially inimical pathway and together with apoptosis, may be activated by similar stress stimuli that can lead to cell death. The molecular cues that dictate the cell fate choice between autophagy and apoptosis remain largely unknown. Here we report that the proapoptotic protein BBC3/PUMA (BCL2 binding component 3) is a bona fide substrate of chaperone-mediated autophagy (CMA). BBC3 associates with HSPA8/HSC70 (heat shock 70kDa protein 8), leading to its lysosome translocation and uptake. Inhibition of CMA results in stabilization of BBC3, which in turn sensitizes tumor cells to undergo apoptosis. We further demonstrate that upon TNF (tumor necrosis factor) treatment, IKBKB/IKKβ (inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase β)-mediated BBC3 Ser10 phosphorylation is crucial for BBC3 stabilization via blocking its degradation by CMA. Mechanistically, Ser10 phosphorylation facilitates BBC3 translocation from the cytosol to mitochondria. BBC3 stabilization resulting from either Ser10 phosphorylation or CMA inhibition potentiates TNF-induced apoptotic cell death. Our findings thus reveal that the selective degradation of BBC3 underlies the prosurvival role of CMA and define a previously unappreciated proapoptotic role of IKBKB that acts through phosphorylation-mediated stabilization of BBC3, thereby promoting TNF-triggered apoptosis.

  View details for DOI 10.1080/15548627.2015.1075688

  View details for Web of Science ID 000361629400013

  View details for PubMedID 26212789

  View details for PubMedCentralID PMC4590652

• TRIM39 regulates cell cycle progression and DNA damage responses via stabilizing p21 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Zhang, L., Mei, Y., Fu, N., Guan, L., Xie, W., Liu, H., Yu, C., Yin, Z., Yu, V. C., You, H. 2012; 109 (51): 20937–42

  Abstract

  The biological function of Tripartite Motif 39 (TRIM39) remains largely unknown. In this study, we report that TRIM39 regulates the steady-state levels of p21 and is a pivotal determinant of cell fate. Ablation of TRIM39 leads to destabilization of p21 and increased G1/S transition in unperturbed cells. Furthermore, DNA damage-induced p21 accumulation is completely abolished in cells with depleted TRIM39. As a result, silencing of TRIM39 abrogates the G2 checkpoint induced by genotoxic stress, leading to increased mitotic entry and, ultimately, apoptosis. Importantly, we show p21 is a crucial downstream effector of TRIM39 mediating G1/S transition and DNA damage-induced G2 arrest. Mechanistically, TRIM39 interacts with p21, which subsequently prevents Cdt2 from binding to p21, therefore blocking ubiquitylation and proteasomal degradation of p21 mediated by CRL4(Cdt2) E3 ligase. Strikingly, we found a significant correlation between p21 abundance and TRIM39 expression levels in human hepatocellular carcinoma samples. Our findings identify a causal role for TRIM39 in regulating cell cycle progression and the balance between cytostasis and apoptosis after DNA damage via stabilizing p21.

  View details for DOI 10.1073/pnas.1214156110

  View details for Web of Science ID 000313123700043

  View details for PubMedID 23213251

  View details for PubMedCentralID PMC3529087