Modulating the PPARγ Pathway Upregulates NECTIN4 and Enhances Chimeric Antigen Receptor (CAR) T Cell Therapy in Bladder Cancer - Beyond the Abstract
Our study demonstrates that modulating the PPARγ pathway increases the expression of NECTIN4, a key protein target on urothelial cancer cells, which enhances the effectiveness of our newly developed NECTIN4-directed CAR T cell therapy.
We found that repurposing the diabetes drug rosiglitazone, a highly selective and potent PPARγ agonist, can be used to "prime" tumor cells. This short-term priming augmented NECTIN4 expression in cancer cells, making them more susceptible to NECTIN4-CAR T cell-mediated killing. This approach addresses a major challenge in solid tumor immunotherapy: heterogeneous or low expression of target antigens (TAAs), which often leads to CAR T cell resistance or escape. We found that PPARγ, which we previously showed to be critical for luminal differentiation in urothelial carcinoma cells, acts as a transcriptional regulator that controls the transcription of the NECTIN4 gene by binding directly to the NECTIN4 promoter.
We leveraged this finding by showing that treatment with rosiglitazone, even in a short-term pulse, increased NECTIN4 mRNA and total and surface NECTIN4 protein expression in multiple bladder cancer cell lines and tumor xenograft models. We then showed that our NECTIN4-CAR T cells, which are engineered receptors designed to recognize NECTIN4-expressing cells and kill them, exhibited enhanced killing efficacy and led to improved tumor growth inhibition and overall survival in mouse models. Importantly, we also showed that rosiglitazone pre-treatment did not increase potential on-target, off-tumor toxicity against normal skin keratinocytes or normal bladder epithelial cells, as these normal cells expressed significantly lower levels of NECTIN4 compared to cancer cells.
Finally, we found that the majority of patients who develop resistance to the ADC, enfortumab vedotin (EV), still retain NECTIN4 expression in the tumor. We then showed that NECTIN4-CAR T cells had potent anti-tumor activity even against EV-resistant cells in preclinical models, suggesting that NECTIN4-CAR T cell therapy offers a viable alternative targeting modality, likely due to non-overlapping mechanisms of resistance. We believe that our findings provide rationale for clinical translation to evaluate NECTIN4-CAR T cell therapy in both EV-naïve and EV-refractory settings, and suggest a therapeutically actionable drug combination leveraging PPARγ agonists like rosiglitazone to increase antigen density and expand the efficacy of NECTIN4-targeting therapies.
Written by: Jonathan Chou, MD, PhD, Helen Diller Family Comprehensive Cancer Center, University of California; Division of Hematology/Oncology, Department of Medicine, University of California, San Francisco, CA
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