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Updated: Mar 19, 2026
Inducible and Reversible Dominant-negative DN Protein Inhibition
Published on: January 7, 2019
A novel CBL-Bflox/flox mouse model allows tissue-selective fully conditional CBL/CBL-B double-knockout: CD4-Cre
Benjamin Goetz1, Wei An1, Bhopal Mohapatra1,2
1Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA.
Abstract:
CBL-family ubiquitin ligases are critical negative regulators of tyrosine kinase signaling, with a clear redundancy between CBL and CBL-B evident in the immune cell and hematopoietic stem cell studies. Since CBL and CBL-B are negative regulators of immune cell activation, elimination of their function to boost immune cell activities could be beneficial in tumor immunotherapy. However, mutations of CBL are associated with human leukemias, pointing to tumor suppressor roles of CBL proteins; hence, it is critical to assess the tumor-intrinsic roles of CBL and CBL-B in cancers. This has not been possible since the only available whole-body CBL-B knockout mice exhibit constitutive tumor rejection. We engineered a new CBL-Bflox/flox mouse, combined this with an existing CBLflox/flox mouse to generate CBLflox/flox; CBL-Bflox/flox mice, and tested the tissue-specific concurrent deletion of CBL and CBL-B using the widely-used CD4-Cre transgenic allele to produce a T-cell-specific double knockout. Altered T-cell development, constitutive peripheral T-cell activation, and a lethal multi-organ immune infiltration phenotype largely resembling the previous Lck-Cre driven floxed-CBL deletion on a CBL-B knockout background establish the usefulness of the new model for tissue-specific CBL/CBL-B deletion. Unexpectedly, CD4-Cre-induced deletion in a small fraction of hematopoietic stem cells led to expansion of certain non-T-cell lineages, suggesting caution in the use of CD4-Cre for T-cell-restricted gene deletion. The establishment of a new model of concurrent tissue-selective CBL/CBL-B deletion should allow a clear assessment of the tumor-intrinsic roles of CBL/CBL-B in non-myeloid malignancies and help test the potential for CBL/CBL-B inactivation in immunotherapy of tumors.
Insights
Researchers developed a new mouse model to study CBL and CBL-B proteins in T-cells, crucial for understanding cancer immunotherapy and potential tumor suppressor roles.
Area of Science:
- Immunology
- Molecular Biology
- Oncology
Background:
- CBL-family ubiquitin ligases (CBL and CBL-B) negatively regulate tyrosine kinase signaling.
- These proteins are critical in immune cell function, suggesting potential roles in tumor immunotherapy.
- However, CBL mutations are linked to leukemia, indicating tumor suppressor functions that need investigation.
Purpose of the Study:
- To develop a novel mouse model for tissue-specific, concurrent deletion of CBL and CBL-B.
- To assess the roles of CBL and CBL-B in T-cell development and activation.
- To enable the study of tumor-intrinsic roles of CBL/CBL-B in cancer.
Main Methods:
- Engineered novel CBL-Bflox/flox mice and combined with existing CBLflox/flox mice to create CBLflox/flox; CBL-Bflox/flox mice.
- Utilized the CD4-Cre transgenic allele for tissue-specific deletion of CBL and CBL-B in T-cells.
- Analyzed T-cell development, activation, and immune infiltration phenotypes.
Main Results:
- The new model successfully generated T-cell-specific double knockouts, showing altered T-cell development and constitutive activation.
- A lethal multi-organ immune infiltration phenotype was observed, similar to previous models.
- Unexpected expansion of non-T-cell lineages occurred due to CD4-Cre activity in hematopoietic stem cells, highlighting potential limitations.
Conclusions:
- The established mouse model is valuable for tissue-specific deletion of CBL/CBL-B, aiding research in non-myeloid malignancies.
- Findings underscore the need for caution when using CD4-Cre for T-cell-restricted gene deletion.
- This model will facilitate assessment of CBL/CBL-B inactivation in cancer immunotherapy.
