Immunological Tolerance to Luciferase and Fluorescent Proteins using Tol Mice Enables Development of Improved Tumor Models for Investigating Immunity and Metastasis

Purpose

The purpose of this study was to develop and validate Tol mice, a novel transgenic mouse model that is immunologically tolerant to reporter proteins like luciferase (Luc2) and GFP. In typical wild-type (WT) mice, these reporter proteins trigger strong immune responses, leading to tumor rejection or slowed growth, which compromises the reliability of preclinical cancer models, especially when studying tumor immunity and metastasis.

Key Findings:

• Tumor cells expressing Luc2/GFP that are rejected in WT mice grow robustly in Tol mice.
• Tol mice specifically tolerate reporter proteins but still mount normal immune responses to other tumor antigens.
• Tumors grow faster and metastasize more extensively in Tol mice than in WT mice due to the lack of anti-reporter immune responses.
• Tol mice enabled advanced models of metastasis, including brain and spontaneous post-surgical metastasis, which is not feasible in WT mice.
• Immunotherapy responses (e.g., with anti-CTLA-4 and anti-PD-1) were stronger in WT mice due to immune responses against reporter proteins. This effect was absent in Tol mice, highlighting that WT models might overestimate treatment efficacy when reporter-expressing tumors are used.
  
  

Conclusion and Next Steps:

Tol mice provide a more accurate and immunologically relevant model for cancer research involving reporter-labeled tumors. They are especially useful for studying metastasis and evaluating immunotherapies without the confounding immune reactions against reporter proteins that occur in WT mice. Taken together, this work enables the use of more accurate preclinical cancer models that better reflect true tumor-immune interactions. By providing a system where reporter proteins do not artificially enhance the host immune response, the study of tumor immunity, metastasis, and immunotherapy will be improved.

References

Khan KA, Qureshi AA, Xu P, Kuo HY, Schumacher TN, Michael IP, Kerbel RS. Immunological Tolerance to Luciferase and Fluorescent Proteins Using Tol Mice Enables Development of Improved Tumor Models for Investigating Immunity and Metastasis. Cancer Res. 2025 Jun 16;85(12):2165-2178. doi: 10.1158/0008-5472.CAN-24-2418. PMID: 40228139.