A TROP2/Claudin Program Mediates Immune Exclusion to Impede Checkpoint Blockade in Breast Cancer

Wu, B.; Thant, W.; Bitman, E.; Liu, T.; Liu, J.; Paschalis, E. I.; Xu, K. H.; Nieman, L. T.; Ting, D. T.; Thimmiah, N.; Sun, S.; Abelman, R. O.; Isakoff, S. J.; Spring, L. M.; Bardia, A.; Ellisen, L. W.

doi:10.1101/2024.12.02.626446

bioRxiv · 10.1101/2024.12.02.626446

A TROP2/Claudin Program Mediates Immune Exclusion to Impede Checkpoint Blockade in Breast Cancer

Wu, B.·Thant, W.·Bitman, E.·Liu, T.·Liu, J.·Paschalis, E. I.·Xu, K. H.·Nieman, L. T.·Ting, D. T.·Thimmiah, N.·Sun, S.·Abelman, R. O.·Isakoff, S. J.·Spring, L. M.·Bardia, A.·Ellisen, L. W.

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Abstract

BackgroundImmune exclusion inhibits anti-tumor immunity and response to immunotherapy, but its mechanisms remain poorly defined. In triple-negative breast cancer (TNBC), an aggressive and generally immune-rich subtype, an immune-cold microenvironment predicts poor prognosis due to a limited response to chemotherapy and immune checkpoint inhibitors. This study aimed to identify mechanisms regulating immune infiltration in TNBC. MethodsWe performed spatial transcriptomic analysis comparing immune-enriched versus immune-cold treatment-naive TNBCs. Functional analyses, including loss-of-function and reconstitution experiments, were conducted to investigate the role of Trophoblast Cell-Surface Antigen 2 (TROP2), a key target of anti-cancer Antibody Drug Conjugates (ADCs), in promoting TNBC progression. A humanized TROP2 syngeneic TNBC model was used to assess the effects of TROP2-targeting in combination with anti-PD1 therapy. Additionally, data from patients treated with immune checkpoint blockade were used to test hypotheses from the preclinical findings. ResultsWe reveal that TROP2 controls barrier-mediated immune exclusion in TNBC through Claudin 7 association and tight junction regulation. TROP2 expression is inversely correlated with T cell infiltration and predicts poor outcomes in TNBC. We demonstrate that TROP2 is sufficient to drive tumor progression in vivo in a CD8 T cell-dependent manner, while its loss deregulates expression and localization of multiple tight junction proteins, enabling T cell infiltration. We show that TROP2 targeting via hRS7, the antibody component of the ADC Sacituzumab govitecan (SG), enhances the anti-PD1 response and improves T cell accessibility and effector function. Correspondingly, TROP2 expression is highly associated with lack of response to anti-PD1 therapy in human breast cancer. ConclusionsThis study defines a new mechanism of barrier-mediated immune exclusion in cancer controlled by TROP2-dependent tight junctions. This mechanism drives tumor progression but can be targeted via TROP2-directed therapy to activate anti-tumor immunity and enhance immunotherapy response. What is already known on this topicBarrier-mediated immune exclusion is emerging as a mechanism of immune evasion in cancer such as triple-negative breast cancer (TNBC), but its molecular underpinnings remain poorly understood. TROP2 is a surface glycoprotein targeted by antibody-drug conjugates such as Sacituzumab govitecan, yet its functional role beyond drug delivery has been unclear. What this study addsThis study identifies TROP2 as a key regulator of tight junction-mediated immune exclusion in TNBC, independent of its intracellular signaling function. TROP2 promotes an immune-cold tumor microenvironment by enforcing mechanical barriers that limit T cell infiltration. How this study might affect research, practice or policyThese findings establish TROP2 as a functional driver of immune evasion and provide a mechanistic rationale for combining TROP2-targeting therapies with immune checkpoint inhibitors to overcome resistance in immune-excluded tumors.

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Wu, B., Thant, W., Bitman, E., Liu, T., Liu, J., Paschalis, E. I., Xu, K. H., Nieman, L. T., Ting, D. T., Thimmiah, N., Sun, S., Abelman, R. O., Isakoff, S. J., Spring, L. M., Bardia, A., Ellisen, L. W.. 2024-12-05. A TROP2/Claudin Program Mediates Immune Exclusion to Impede Checkpoint Blockade in Breast Cancer. https://doi.org/10.1101/2024.12.02.626446

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