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Updated: Oct 23, 2025
Induction of Invasive Transitional Cell Bladder Carcinoma in Immune Intact Human MUC1 Transgenic Mice: A Model for Immunotherapy Development
Published on: October 30, 2013
RNF144A deficiency promotes PD-L1 protein stabilization and carcinogen-induced bladder tumorigenesis
Shiuh-Rong Ho1, Yu-Cheng Lee2, Michael M Ittmann3
1Section of Hematology/Oncology, Department of Medicine, Baylor College of Medicine, Houston, TX, 77030, USA.
Abstract:
RNF144A is a DNA damage-induced E3 ubiquitin ligase that targets proteins involved in genome instability for degradation, e.g., DNA-PKcs and BMI1. RNF144A is frequently mutated or epigenetically silenced in cancer, providing the rationale to evaluate RNF144A loss of function in tumorigenesis. Here we report that RNF144A-deficient mice are more prone to the development of bladder tumors upon carcinogen exposure. In addition to DNA-PKcs and BMI1, we identify the immune checkpoint protein PD-L1 as a novel degradation target of RNF144A, since these proteins are expressed at higher levels in Rnf144a KO tumors. RNF144A interacts with PD-L1 in the plasma membrane and intracellular vesicles and promotes poly-ubiquitination and degradation of PD-L1. Therefore, Rnf144a KO stabilizes PD-L1 and leads to a reduction of tumor-infiltrating CD8+ T cell populations in the BBN-induced bladder tumors. The bladder tumors developed in WT and Rnf144a KO mice primarily express CK5 and CK14, markers of basal cancer subtype, as expected in BBN-induced bladder tumors. Intriguingly, the Rnf144a KO tumors also express GATA3, a marker for the luminal subtype, suggesting that RNF144A loss of function promotes features of cellular differentiation. Such differentiation features in Rnf144a KO tumors likely result from a decrease of EGFR expression, consistent with the reported role of RNF144A in maintaining EGFR expression. In summary, for the first time our study demonstrates the in vivo tumor suppressor activity of RNF144A upon carcinogenic insult. Loss of RNF144A promotes the expression of DNA-PKcs, BMI1 and PD-L1, likely contributing to the carcinogen-induced bladder tumorigenesis.
Insights
Loss of RNF144A, a tumor suppressor, accelerates bladder cancer in mice by increasing DNA-PKcs, BMI1, and PD-L1. This promotes tumor growth and alters cellular differentiation and immune response.
Area of Science:
- Oncology
- Molecular Biology
- Immunology
Background:
- RNF144A is a DNA damage-induced E3 ubiquitin ligase targeting genome instability proteins.
- RNF144A is frequently inactivated in cancer, suggesting a tumor suppressor role.
- Understanding RNF144A's function in tumorigenesis is crucial for cancer therapy.
Purpose of the Study:
- To investigate the in vivo tumor suppressor activity of RNF144A in bladder cancer development.
- To identify novel targets of RNF144A-mediated degradation.
- To elucidate the mechanisms by which RNF144A loss influences tumor characteristics and immune microenvironment.
Main Methods:
- Utilized RNF144A-deficient (Rnf144a KO) and wild-type (WT) mice exposed to a carcinogen (BBN) to induce bladder tumors.
- Analyzed protein expression levels (DNA-PKcs, BMI1, PD-L1, GATA3, EGFR) in tumors using Western blotting and immunohistochemistry.
- Assessed tumor-infiltrating CD8+ T cell populations via flow cytometry.
Main Results:
- Rnf144a KO mice exhibited increased susceptibility to carcinogen-induced bladder tumors.
- Loss of RNF144A led to elevated expression of DNA-PKcs, BMI1, and notably, the immune checkpoint protein PD-L1.
- RNF144A deficiency stabilized PD-L1, reduced CD8+ T cell infiltration, and promoted basal to luminal differentiation markers (GATA3) and decreased EGFR expression.
Conclusions:
- RNF144A functions as a tumor suppressor in vivo, protecting against carcinogen-induced bladder tumorigenesis.
- Loss of RNF144A promotes tumor development by stabilizing key oncogenic proteins (DNA-PKcs, BMI1) and immune-evasive factors (PD-L1).
- RNF144A deficiency alters tumor cell differentiation and impacts the tumor immune microenvironment, offering potential therapeutic targets.
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