1. Academic Validation
  2. Membrane-Associated RING-CH 8 Functions as a Novel PD-L1 E3 Ligase to Mediate PD-L1 Degradation Induced by EGFR Inhibitors

Membrane-Associated RING-CH 8 Functions as a Novel PD-L1 E3 Ligase to Mediate PD-L1 Degradation Induced by EGFR Inhibitors

  • Mol Cancer Res. 2021 Oct;19(10):1622-1634. doi: 10.1158/1541-7786.MCR-21-0147.
Guoqing Qian 1 Jianping Guo 2 Karin A Vallega 1 Changjiang Hu 2 Zhen Chen 1 Yunfu Deng 1 Qiming Wang 3 Songqing Fan 4 Suresh S Ramalingam 1 Taofeek K Owonikoko 1 Wenyi Wei 2 Shi-Yong Sun 5
Affiliations

Affiliations

  • 1 Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, Georgia.
  • 2 Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
  • 3 Department of Internal Medicine, The Affiliated Cancer Hospital of Zhengzhou University, Henan Cancer Hospital, Zhengzhou, Henan, China.
  • 4 Department of Pathology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.
  • 5 Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, Georgia. ssun@emory.edu.
Abstract

Expression of programmed death-ligand 1 (PD-L1) on Cancer cells is a critical mechanism contributing to immunosuppression and immune escape. PD-L1 expression may also affect therapeutic outcomes of epidermal growth factor receptor (EGFR)-targeted therapy (e.g., with osimertinib/AZD9291) against EGFR-mutant non-small cell lung cancers (NSCLC) and can even be altered during the treatment albeit with largely undefined mechanisms. This study primarily focuses on elucidating the mechanism by which osimertinib induces PD-L1 degradation in addition to validating osimertinib's effect on decreasing PD-L1 expression in EGFR-mutant NSCLC cells and tumors. Osimertinib and other EGFR inhibitors effectively decreased PD-L1 levels primarily in EGFR-mutant NSCLCs and xenografted tumors. Osimertinib not only decreased PD-L1 mRNA expression, but also prompted proteasomal degradation of PD-L1 protein, indicating both transcriptional and posttranslational mechanisms accounting for osimertinib-induced reduction of PD-L1. Knockdown of β-TrCP or inhibition of GSK3 failed to prevent PD-L1 reduction induced by osimertinib. Rather, knockdown of membrane-associated RING-CH 8 (MARCH8) that encodes a membrane-bound E3 ubiquitin Ligase rescued osimertinib-induced PD-L1 reduction. Furthermore, manipulation of MARCH8 expression accordingly altered PD-L1 degradation rate. Critically, MARCH8 interacted with PD-L1 through its N-terminal region and also ubiquitinated PD-L1 in cells. Collectively, these results strongly suggest that MARCH8 is a previously undiscovered E3 ubiquitin Ligase responsible for PD-L1 degradation including osimertinib-induced PD-L1 degradation, establishing a novel connection between MARCH8 and PD-L1 regulation. IMPLICATIONS: This study has demonstrated a previously undiscovered function of MARCH8 in mediating PD-L1 degradation induced by EGFR inhibitors in EGFR-mutant NSCLC cells, establishing a novel connection between MARCH8 and PD-L1 regulation.

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Products
  • Cat. No.
    Product Name
    Description
    Target
    Research Area
  • HY-15729
    99.79%, EGFR Inhibitor