Summary: Galectin-1 (Gal-1) has been identified as a PET imaging biomarker that predicts tumor responses to immune checkpoint blockade (ICB) therapy, aiding in patient stratification and optimizing immunotherapy.

Key Takeaways

  1. New Diagnostic Biomarker: Galectin-1 (Gal-1) emerges as a PET imaging biomarker, enhancing predictions and treatment planning for immune checkpoint blockade (ICB) therapy in cancer patients.
  2. Improved Patient Selection: Gal-1 PET imaging aids in accurately selecting patients for immunotherapy, leading to more effective treatment outcomes.
  3. Advancing Personalized Medicine: Research highlights the role of PET in designing personalized treatment strategies, offering real-time, non-invasive assessment and potential for better patient care.


The protein galectin-1 (Gal-1) has been identified as a new PET imaging biomarker for immune checkpoint blockade (ICB) therapy, allowing physicians to predict the tumor responses before beginning treatment. Information garnered from Gal-1 PET imaging could also be used to facilitate patient stratification and optimize immunotherapy, enabling targeted interventions and improving patient outcomes. This research was published in the May issue of The Journal of Nuclear Medicine.

Immunotherapies, such as ICB, have produced promising clinical outcomes in melanoma, non-small cell lung cancer, and several other types of tumors. However, only a subgroup of patients experiences positive outcomes with objective response rates spanning between 5% and 60%.

Immunotherapy Effectiveness Prediction

“Developing reliable approaches for assessing responses and selecting eligible patients for immunotherapy remains challenging,” says Zhaofei Liu, PhD, Boya Distinguished Professor at Peking University in Beijing, China. 

Liu adds, “Current clinical criteria for monitoring solid tumor responses to immunotherapy are based on CT and MRI scans, but these methods result in a considerable delay between treatment commencement and response evaluation. Molecular imaging techniques, especially PET, have emerged as robust tools for predicting immunotherapy effectiveness through the real-time, quantitative, and noninvasive assessment of biomarkers in vivo.”

Predicting ICB Therapy Response

In the study, a mouse model was utilized to identify new imaging biomarkers for tumor responses to ICB therapy. Through a proteomic analysis (separation, identification, and quantification of proteins in a tumor), researchers found that tumors exhibiting low Gal-1 expression responded positively to ICB therapy.

Next, Gal-1 was labeled with 124I and the radiotracer (124I-α-Gal-1) and small animal PET imaging and biodistribution studies were conducted to assess the specificity of the radiotracer. PET imaging with 124I-αGal-1 showed the immunosuppressive status of the tumor microenvironment, thus enabling the prediction of ICB resistance in advance of treatment. For tumors that were not predicted to respond well to ICB therapy, researchers developed a rescue strategy that utilized a Gal-1 inhibitor that significantly improved the chance for success.

Personalized Approaches in Cancer Care

“Gal-1 PET opens avenues for the early prediction of ICB efficacy before treatment initiation and facilitates the precision design of combinational regimes,” notes Liu. “This sensitive approach has the potential to achieve individualized precision treatment for patients in the future.”