Related Experiment Video
Updated: Jun 5, 2025
Dynamic Contrast Enhanced Magnetic Resonance Imaging of an Orthotopic Pancreatic Cancer Mouse Model
Published on: April 18, 2015
Multimetric MRI Captures Early Response and Acquired Resistance of Pancreatic Cancer to KRAS Inhibitor Therapy
Purpose:
In pancreatic ductal adenocarcinoma (PDAC), KRAS mutations drive both cancer cell growth and formation of a dense stroma. Small molecule KRAS inhibitors (KRASi) represent a promising new treatment hence clinical tools that can assess early response, detect resistance and/or predict prolonged survival are desirable to understand clinical biology of KRASi. We hypothesized that diffusion-weighted MRI (DWI) can detect cell death while dynamic contrast enhanced MRI (DCE) and magnetization transfer ratio (MTR) imaging are sensitive to tumor microenvironment changes, and these metrics shed insights into tumor size change induced by KRASi treatment.
Experimental Design:
Multiple preclinical PDAC models including a genetically engineered mouse model (KPC) received MRTX1133, a KRASi specific for KRAS G12D mutation. Quantitative imaging markers were corroborated with immunohistochemistry (IHC) analyses.
Results:
Significant increase of tumor apparent diffusion coefficient (a DWI metric) was detected as early as 48h and persisted to Day7 after initiation of KRASi treatment and was strongly correlated with cell death and reduced cellularity, resulting in greatly prolonged median survival in treated mice. Capillary perfusion/permeability (a DCE metric) exhibited an inverse relationship with microvascular density. Distinct responses of KRAS G12C versus KRAS G12D tumors to MRTX1133 were captured by the MRI metrics corroborated with IHC. When tumors developed resistance to MRTX1133, the imaging marker values exhibited a reversal from those of responding tumors.
Conclusions:
Multiparametric MRI provides early biological insights of cancer and stromal response to KRASi treatment and sets the stage for testing the utility of these clinically ready MRI methods in patients receiving KRASi therapy.
Translational Relevance:
Emerging small molecule KRAS inhibitors (KRASi) represent a new class of therapy for PDAC. Clinical tools that can provide early biological insights of KRASi therapy are desirable. In PDAC models, we examined a clinically ready imaging protocol that combines MRI-based tumor size, diffusion-weighted MRI (DWI), dynamic contrast enhanced MRI (DCE), and magnetization transfer ratio (MTR) for detection of early response as well as acquired resistance to MRTX1133, a KRASi being evaluated in clinical trials. Our data show that DWI and DCE metrics provided key insights of significant cell death and tumor microenvironment changes underlying tumor size regression as early as 48 hours after KRASi treatment initiation. These MRI metrics also captured resistance to KRASi developed over prolonged treatment. This study has high translational relevance by employing clinically applied MRI methods, an investigational new drug and a genetically engineered mouse model that recapitulates salient features of human PDAC.
Insights
Multiparametric MRI detects early treatment response in pancreatic cancer. Advanced imaging markers reveal cell death and microenvironment changes, aiding patient management during KRAS inhibitor therapy.
Area of Science:
- Oncology
- Radiology
- Biomedical Imaging
Background:
- Pancreatic ductal adenocarcinoma (PDAC) is driven by KRAS mutations, necessitating novel therapies like KRAS inhibitors (KRASi).
- Current assessment of KRASi therapy relies on tumor size, lacking early biological response indicators.
- Developing clinical tools to monitor early treatment effects, resistance, and survival is crucial for PDAC patient management.
Purpose of the Study:
- To investigate the utility of multiparametric MRI, including diffusion-weighted MRI (DWI), dynamic contrast-enhanced MRI (DCE), and magnetization transfer ratio (MTR) imaging, in assessing early responses to KRAS inhibitors in PDAC.
- To correlate imaging markers with immunohistochemistry (IHC) findings and evaluate their ability to detect cell death, microenvironment changes, and resistance.
- To assess the potential of these clinically ready MRI methods for patient management during KRASi therapy.
Main Methods:
- Utilized multiple preclinical PDAC models, including a genetic engineered mouse model (KPC), treated with MRTX1133, a specific KRAS G12D inhibitor.
- Acquired multiparametric MRI data (DWI, DCE, MTR) at early time points (48h, day-7) and correlated with IHC.
- Analyzed imaging markers for changes in cell death, cellularity, perfusion, permeability, and stromal matrix, and assessed responses in KRAS G12C versus KRAS G12D mutant tumors and in resistant models.
Main Results:
- Quantitative imaging markers from DWI, DCE, and MTR revealed significant early changes indicative of cell death and microenvironment alterations within 48h and 7 days of KRASi treatment.
- These MRI markers correlated with IHC findings and provided insights beyond standard tumor size assessment.
- The study captured distinct responses based on KRAS mutation type (G12C vs. G12D) and identified reversal of imaging markers in tumors resistant to MRTX1133.
Conclusions:
- Multiparametric MRI (DWI, DCE, MTR) effectively detects early biological responses, including cell death and tumor microenvironment modifications, induced by KRAS inhibitors in PDAC.
- These clinically applicable imaging methods offer valuable insights for monitoring treatment efficacy, detecting resistance, and potentially predicting survival in patients undergoing KRASi therapy.
- The findings support the translation of these MRI techniques for clinical trials and patient management in PDAC treated with KRAS inhibitors.
