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Supplementary Figure 6 from BRAF Inhibition Increases Tumor Infiltration by T cells and Enhances the Antitumor Activity of Adoptive Immunotherapy in Mice

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posted on 2023-03-31, 18:05 authored by Chengwen Liu, Weiyi Peng, Chunyu Xu, Yanyan Lou, Minying Zhang, Jennifer A. Wargo, Jie Qing Chen, Haiyan S. Li, Stephanie S. Watowich, Yan Yang, Dennie Tompers Frederick, Zachary A. Cooper, Rina M. Mbofung, Mayra Whittington, Keith T. Flaherty, Scott E. Woodman, Michael A. Davies, Laszlo G. Radvanyi, Willem W. Overwijk, Gregory Lizée, Patrick Hwu

PDF file - 82K, Administration of PLX4720 in vivo increases tumor infiltration of adoptively transferred T cells and enhances antitumor responses

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ARTICLE ABSTRACT

Purpose: Treatment of melanoma patients with selective BRAF inhibitors results in objective clinical responses in the majority of patients with BRAF-mutant tumors. However, resistance to these inhibitors develops within a few months. In this study, we test the hypothesis that BRAF inhibition in combination with adoptive T-cell transfer (ACT) will be more effective at inducing long-term clinical regressions of BRAF-mutant tumors.Experimental Design:BRAF-mutated human melanoma tumor cell lines transduced to express gp100 and H-2Db to allow recognition by gp100-specific pmel-1 T cells were used as xenograft models to assess melanocyte differentiation antigen–independent enhancement of immune responses by BRAF inhibitor PLX4720. Luciferase-expressing pmel-1 T cells were generated to monitor T-cell migration in vivo. The expression of VEGF was determined by ELISA, protein array, and immunohistochemistry. Importantly, VEGF expression after BRAF inhibition was tested in a set of patient samples.Results: We found that administration of PLX4720 significantly increased tumor infiltration of adoptively transferred T cells in vivo and enhanced the antitumor activity of ACT. This increased T-cell infiltration was primarily mediated by the ability of PLX4720 to inhibit melanoma tumor cell production of VEGF by reducing the binding of c-myc to the VEGF promoter. Furthermore, analysis of human melanoma patient tumor biopsies before and during BRAF inhibitor treatment showed downregulation of VEGF consistent with the preclinical murine model.Conclusion: These findings provide a strong rationale to evaluate the potential clinical application of combining BRAF inhibition with T-cell–based immunotherapy for the treatment of patients with melanoma. Clin Cancer Res; 19(2); 393–403. ©2012 AACR.

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