Human Regulatory T Cells Kill Tumor Cells through Granzyme-Dependent Cytotoxicity upon Retargeting with a Bispecific Antibody

Abstract

A major mechanism by which human regulatory T cells (Tregs) have been shown to suppress and kill autologous immune cells is through the granzyme-perforin pathway. However, it is unknown whether Tregs also possess the capacity to kill tumor cells using similar mechanisms. Bispecific antibodies (bscAbs) have emerged as a promising class of therapeutics that activate T cells against tumor antigens without the need for classical MHC-restricted TCR recognition. Here, we show that a bscAb targeting the tumor-specific mutation of the epidermal growth factor receptor, EGFRvIII, redirects human CD4+CD25+FoxP3+ Tregs to kill glioblastoma (GBM) cells. This activity was significantly abrogated by inhibitors of the granzyme-perforin pathway. Notably, analyses of human primary GBM also displayed diffuse infiltration of granzyme-expressing FoxP3+ T cells. Together, these data suggest that despite their known suppressive functions, tumor-infiltrating Tregs possess potent cytotoxic mechanisms that can be co-opted for efficient tumor cell lysis.

Tregs activated by bispecific antibodies

“…They reported an efficient elimination of target antigen-expressing glioblastoma cells by anti-CD3-anti-EGFRvIII bsAbredirected Tregs. 5,6 There are several potential technical explanations for the observed differences between Choi's and our results. First, we used sorted CD4 C CD25 C CD127 low CD45RA C Tregs as starting population as it is well known that these cells have the highest capacity to maintain phenotypic and functional Treg properties after prolonged in vitro cultivation.…”

CD137 Agonist Therapy Can Reprogram Regulatory T Cells into Cytotoxic CD4+ T Cells with Antitumor Activity

“…These results provide indirect evidence that the Foxp3 + Eomes + CD4 + T cells may not mediate immunosuppressive effects on conventional T cells and are therefore distinct from the Treg population described by Loebbermann et al (39). It has recently been shown that granzyme B-producing Tregs can kill tumor target cells (40). However, these cells were redirected by bispecific Abs and classical TCR involvement in specific tumor cell recognition was absent.…”

Involvement of Perforin/Granzyme B-Dependent Signaling Pathway in Cytotoxic Activity of Dendritic Cells Towards Human Glioblastoma Cells

“…В пользу этого предпо-ложения свидетельствуют данные ряда авторов об оппозитном эффекте IL-4 и IFNα на экспрес-сию перфорина и гранзима Б. Так, IL-4 являет-ся негативным регулятором экспрессии генов гранзима Б и перфорина в IL2-активированных NK-клетках [10]. Кроме того, IL-4 дозозависи-мо подавляет экспрессию и продукцию гранзи-ма Б в регуляторных Т-клетках (Treg), а также гранзим Б-опосредованную противоопухолевую цитотоксичность Treg [9]. В отношении IFNα, наоборот, показано стимулирующее влияние на экспрессию гранзима Б на уровне гена и са-мого белка в NK-клетках и их цитотоксическую активность [27], а также на экспрессию мРНК перфорина [20].…”