• Skip to main content
  • Skip to after header navigation
  • Skip to site footer
ERN: Emerging Researchers National Conference in STEM

ERN: Emerging Researchers National Conference in STEM

  • About
    • About AAAS
    • About the NSF
    • About the Conference
    • Partners/Supporters
    • Project Team
  • Conference
  • Abstracts
    • Undergraduate Abstract Locator
    • Graduate Abstract Locator
    • Abstract Submission Process
    • Presentation Schedules
    • Abstract Submission Guidelines
    • Presentation Guidelines
  • Travel Awards
  • Resources
    • Award Winners
    • Code of Conduct-AAAS Meetings
    • Code of Conduct-ERN Conference
    • Conference Agenda
    • Conference Materials
    • Conference Program Books
    • ERN Photo Galleries
    • Events | Opportunities
    • Exhibitor Info
    • HBCU-UP/CREST PI/PD Meeting
    • In the News
    • NSF Harassment Policy
    • Plenary Session Videos
    • Professional Development
    • Science Careers Handbook
    • Additional Resources
    • Archives
  • Engage
    • Webinars
    • ERN 10-Year Anniversary Videos
    • Plenary Session Videos
  • Contact Us
  • Login

Monitoring β-glucuronidase with catalyCEST MRI: A Method to Assess Antibody Directed Enzyme Prodrug Therapy

Graduate #39
Discipline: Chemistry and Chemical Sciences
Subcategory: Chemistry (not Biochemistry)

Gabriela Fernandez-Cuervo - University of Arizona
Co-Author(s): Kyle M. Jones and Mark D. Pagel, University of Arizona, Tucson, AZ



Tumors have heterogeneous biomarker expression, including the varying expression levels of antigens. If exploited for targeted therapies, low antigen expression can require an amplification mechanism to deliver sufficient active drug for an efficient treatment. To amplify therapy response, antibody-directed enzyme-activated prodrug therapy (ADEPT) uses enzymes as tools to selectively activate prodrugs in tumor tissue. ADEPT requires sufficient antigen expression, delivery of an antibody-enzyme conjugate, strong enzyme activity, and site-specific produrg delivery. A non-invasive diagnostic method is needed to ensure that these components are in place for successful ADEPT. Our overarching goal is to develop a catalyCEST MRI contrast agent that detects enzyme activity of β-glucuronidase (GUS) that is used in ADEPT.

A catalyCEST agent was synthesized that is a substrate for GUS. The optimized catalyCEST MRI protocol consisted of a CEST-FISP MRI pulse sequence with a 5-sec saturation pulse and 5 μT saturation power. The protocol was repeated at 96 saturation frequencies to generate a CEST spectrum. The imaging results were analyzed using fitting algorithms developed using MATLAB (version 2014b), which applies a spatial Gaussian filter, cubic splines, and Lorentzian line shape fitting of a CEST spectrum. A Hanes-Woolf CEST plot was used to determine exchange rates1. In the presence of GUS, the catalyCEST agent underwent saccharide hydrolysis to produce 4-aminosalicylic acid. This reaction converted the carbamate moiety into a free primary amine, and caused a loss of CEST at 4.25 ppm, showing that this agent can detect enzyme activity. The CEST signal at 9.25 ppm did not change, demonstrating that the CEST at 9.25 ppm was a good internal “control” signal. Proton exchange rate constants of the substrate were 1022 Hz for the carbamate moiety at 4.25 pm, and 799 Hz for the salicylic acid proton at 9.25 ppm. After the enzyme reaction, the chemical exchange rate of the remaining salicylic acid proton at 9.25 ppm was 1048 Hz. These results demonstrate that the catalyCEST agent can detect GUS activity by monitoring the change in CEST at 4.25 ppm. Future studies involve expanding this platform technology to evaluate other important enzymes for reporter gene imaging and targeted therapies, and to perform in vivo studies with mouse models of cancer.

1Randtke EA, et al. Magn. Reson. Med. 2014, 71:1603-1612.

Abstract-GFC.docx

Funder Acknowledgement(s): This project has been funded by the Biological Chemistry Program Training Grant: T32 GM008804 and was also supported by NIH R01 CA169774-01. Gabriela Fernandez-Cuervo is a Howard Hughes Medical Institute Gilliam Fellow.

Faculty Advisor: Mark D. Pagel, mpagel@email.arizona.edu

Sidebar

Abstract Locators

  • Undergraduate Abstract Locator
  • Graduate Abstract Locator

This material is based upon work supported by the National Science Foundation (NSF) under Grant No. DUE-1930047. Any opinions, findings, interpretations, conclusions or recommendations expressed in this material are those of its authors and do not represent the views of the AAAS Board of Directors, the Council of AAAS, AAAS’ membership or the National Science Foundation.

AAAS

1200 New York Ave, NW
Washington,DC 20005
202-326-6400
Contact Us
About Us

  • LinkedIn
  • Facebook
  • Instagram
  • Twitter
  • YouTube

The World’s Largest General Scientific Society

Useful Links

  • Membership
  • Careers at AAAS
  • Privacy Policy
  • Terms of Use

Focus Areas

  • Science Education
  • Science Diplomacy
  • Public Engagement
  • Careers in STEM

Focus Areas

  • Shaping Science Policy
  • Advocacy for Evidence
  • R&D Budget Analysis
  • Human Rights, Ethics & Law

© 2023 American Association for the Advancement of Science