Optimal Population of FoxP3+ T Cells in Tumors Requires an Antigen Priming-Dependent Trafficking Receptor Switch

Abstract

FoxP3+ T cells populate tumors and regulate anti-tumor immunity. The requirement for optimal population of FoxP3+ regulatory T cells in tumors remains unclear. We investigated the migration requirement and stability of tumor-associated FoxP3+ T cells. We found that only memory, but not naïve, FoxP3+ T cells are highly enriched in tumors. Almost all of the tumor-infiltrating FoxP3+ T cells express Helios, an antigen associated either with thymus-generated FoxP3+ T cells or activated T cells in the periphery. The tumor-infiltrating FoxP3+ T cells largely lack CD62L and CCR7, two trafficking receptors required for T cell migration into secondary lymphoid tissues. Instead, the tumor infiltrating FoxP3+ T cells highly express memory/tumor-associated CCR8 and CXCR4. Antigen priming is required for induction of this trafficking receptor phenotype in FoxP3+ T cells and only antigen primed, but not antigen-inexperienced naive, FoxP3+ T cells can efficiently migrate into tumors. While the migration of FoxP3+ T cells into tumors was a readily detectable event, generation of induced FoxP3+ T cells within tumors was unexpectedly inefficient. Genetic marking of current and ex-FoxP3+ T cells revealed that tumor-infiltrating FoxP3+ T cells are highly stable and do not readily convert back to FoxP3− T cells. Taken together, our results indicate that population of tumors with thymus-generated FoxP3+ T cells requires an antigen priming-dependent trafficking receptor switch in lymphoid tissues.

Helios expression in FoxP3+T regulatory cells

“…Most Tregs in human glioblastoma multiforme and mouse brain tumours expressed Helios [12]. Additionally, tumour-infiltrating FoxP3 + Tregs are largely positive for Helios expression [6,13]. Consistent with this, we also found that the majority (75 and 81%) of FoxP3 + Tregs isolated from two human metastatic lesions express Helios ( Figure 1A).…”

“…All these studies indicate that increased levels in some tumours could be thymic-derived rather than tumourinduced Tregs. However, this should be interpreted carefully especially if Helios expression is additionally regulated by non-thymus factors [13]. In pre-malignant lesions of respiratory papillomas, enriched Tregs lacked the expression of Helios, which could indicate that these Tregs are induced [14].…”

Differential control of Helios+/− Treg development by monocyte subsets through disparate inflammatory cytokines

“…20,21 For example, Helios 1 Treg frequencies are increased in the peripheral blood of cancer patients, and most carcinoma-infiltrating Tregs are Helios positive. [8][9][10][11][12] In contrast, in premalignant tumors, such as nasal polyposis 13 and respiratory papillomas, 14 most infiltrating Tregs were shown to be Helios negative. Moreover, in type 2 diabetes mellitus, peripheral blood Helios 2 Treg numbers were decreased, although Helios 1 Treg counts were normal, 18 whereas in patients with myasthenia gravis, Helios 1 Treg frequency was lower.…”

“…6,7 In mice and man, Helios 1 Tregs represent about 70%, whereas Helios 2 Tregs constitute around 30% of Foxp3 1 T cells in the periphery. 5 However, these frequencies appear differently in malignancies, [8][9][10][11][12][13][14] autoimmunity, [15][16][17][18][19] and after infection. 20,21 For example, Helios 1 Treg frequencies are increased in the peripheral blood of cancer patients, and most carcinoma-infiltrating Tregs are Helios positive.…”

Low-dose cyclophosphamide depletes circulating naïve and activated regulatory T cells in malignant pleural mesothelioma patients synergistically treated with dendritic cell-based immunotherapy

“…nTregs differentiate into aTregs upon T-cell receptor stimulation by antigen recognition, 24,44,45 which could imply that patients having a relatively high percentage of peripheral nTregs have less tumor-specific Tregs. Due to their naïve phenotype, these nTregs are inefficient in infiltrating the tumor, 46 as is also illustrated by their low CCR4 expression, and thus these cells cannot exert immunosuppressive activity. Therefore, immunotherapy might be more effective in these patients, which is a possible explanation for this counterintuitive finding.…”