Data from Treg-Dominant Tumor Microenvironment Is Responsible for Hyperprogressive Disease after PD-1 Blockade Therapy

Abstract

<div>Abstract<p>Programmed cell death 1 (PD-1) blockade therapy can result in dramatic responses in some patients with cancer. However, about 15% of patients receiving PD-1 blockade therapy experience rapid tumor progression, a phenomenon termed “hyperprogressive disease” (HPD). The mechanism(s) underlying HPD has been difficult to uncover because HPD is challenging to reproduce in animal models. Near-infrared photoimmunotherapy (NIR-PIT) is a method by which specific cells in the tumor microenvironment (TME) can be selectively depleted without disturbing other cells in the TME. In this study, we partially depleted CD8<sup>+</sup> T cells with NIR-PIT by targeting the CD8β antigen thereby temporarily changing the balance of T-cell subsets in two different syngeneic tumor models. PD-1 blockade in these models led to rapid tumor progression compared with controls. CD3ε<sup>+</sup>CD8α<sup>+</sup>/CD3ε<sup>+</sup>CD4<sup>+</sup>FoxP3<sup>+</sup> (T<sub>eff</sub>/T<sub>reg</sub>) ratios in the PD-1 and NIR-PIT groups were lower than in controls. Moreover, in a bilateral tumor model, low-dose CD8β-targeted NIR-PIT with anti–PD-1 blockade showed rapid tumor progression only in the tumor exposed to NIR light. In this experiment CD8β-targeted NIR-PIT in the exposed tumor reduced local CD8<sup>+</sup> T cells resulting in a regulatory T-cell (Treg)–dominant TME. In conclusion, this reports an animal model to simulate the Treg-dominant TME, and the data generated using the model suggest that HPD after PD-1 blockade therapy can be attributed, at least in part, to imbalances between effector T cells and Tregs in the TME.</p></div>