FLT3L Release by Natural Killer Cells Enhances Response to Radioimmunotherapy in Preclinical Models of HNSCC

Abstract

Purpose: Natural killer (NK) cells are type I innate lymphoid cells that are known for their role in killing virally infected cells or cancer cells through direct cytotoxicity. In addition to direct tumor cell killing, NK cells are known to play fundamental roles in the tumor microenvironment through secretion of key cytokines, such as FMS-like tyrosine kinase 3 ligand (FLT3L). Although radiotherapy is the mainstay treatment in most cancers, the role of radiotherapy on NK cells is not well characterized. Experimental Design: This study combines radiation, immunotherapies, genetic mouse models, and antibody depletion experiments to identify the role of NK cells in overcoming resistance to radiotherapy in orthotopic models of head and neck squamous cell carcinoma. Results: We have found that NK cells are a crucial component in the development of an antitumor response, as depleting them removes efficacy of the previously successful combination treatment of radiotherapy, anti-CD25, and anti-CD137. However, in the absence of NK cells, the effect can be rescued through treatment with FLT3L. But neither radiotherapy with FLT3L therapy alone nor radiotherapy with anti-NKG2A yields any meaningful tumor growth delay. We also identify a role for IL2 in activating NK cells to secrete FLT3L. This activity, we show, is mediated through CD122, the intermediate affinity IL2 receptor, and can be targeted with anti-CD25 therapy. Conclusions: These findings highlight the complexity of using radio-immunotherapies to activate NK cells within the tumor microenvironment, and the importance of NK cells in activating dendritic cells for increased tumor surveillance.

Dichotomous effects of cellular expression of STAT3 on tumor growth of HNSCC

“…Our past work has highlighted the role of IL-2 stimulation on activating NK cells, and the role of activated NK cells on increased tumor surveillance and tumor cell kill. 15 The effect of IL-2 on NK cells is amplified when signaling goes through CD122, the intermediate IL-2 receptor, and not CD25, the high affinity IL-2 receptor. 15 Here, NK cells activated by IL-2 show increased levels of pSTAT3 (Figure 5C).…”

“…15 The effect of IL-2 on NK cells is amplified when signaling goes through CD122, the intermediate IL-2 receptor, and not CD25, the high affinity IL-2 receptor. 15 Here, NK cells activated by IL-2 show increased levels of pSTAT3 (Figure 5C). Phosphorylation of STAT3 was increased when anti-CD25 antibody was added, with IL-2 signaling occurring through CD122 suggesting STAT3 plays a role in NK cell activation (Figure 5C).…”

“…STAT3 has also been shown to increase tumor growth through regulation within the cancer cell itself, 12 and others have identified a role for STAT3 in regulating anti-tumor activity by NK cells through production of granzymes. 13 Both Tregs 14 and NK cells 15 significantly impact development of the HNSCC TME, and the role STAT3 plays in governing their actions requires further clarification.…”

“…For our studies, we used two orthotopically implanted models of murine HPV-unrelated HNSCC, MOC2 and LY2. Our previous work with these tumor models has identified Tregs 9,14 and NK cells 15 as important predictors of treatment outcome, yet the role of STAT3 in the cancer cell, and these immune cells remains unknown. To accomplish this, we used a CRISPR knockout system for genetic deletion of STAT3 within the cancer cells to understand its contribution to tumor growth and development of resistance.…”

Natural killer cell-related prognosis signature characterizes immune landscape and predicts prognosis of HNSCC

“…Many single-cell sequencing analyses have come to similar conclusions, with fewer NK cells in tumors than in normal tissue ( 8 ). In fighting solid tumors, NK cells may have an advantage over T cells like enhancing the response to radioimmunotherapy and chemotherapy ( 9 , 10 ), thus exhibiting important prognostic significance ( 11 – 14 ), despite having less tumor immune infiltration ( 15 ).…”