Early Detection of Tumor Cells by Innate Immune Cells Leads to Treg Recruitment through CCL22 Production by Tumor Cells

Abstract

In breast carcinomas, patient survival seems to be negatively affected by the recruitment of regulatory T cells (T reg ) within lymphoid aggregates by CCL22. However, the mechanisms underpinning this process, which may be of broader significance in solid tumors, have yet to be described. In this study, we determined how CCL22 production is controlled in tumor cells. In human breast carcinoma cell lines, CCL22 was secreted at low basal levels that were strongly increased in response to inflammatory signals [TNF-a, IFN-g, and interleukin (IL)-1b], contrasting with CCL17. Primary breast tumors and CD45þ infiltrating immune cells appeared to cooperate in driving CCL22 secretion, as shown clearly in cocultures of breast tumor cell lines and peripheral blood mononuclear cells (PBMC) or their supernatants. We determined that monocyte-derived IL-1b and TNF-a are key players as monocyte depletion or neutralization of these cytokines attenuated secretion of CCL22. However, when purified monocytes were used, exogenous human IFN-g was also required to generate this response suggesting a role for IFN-g-producing cells within PBMCs. In this setting, we found that human IFN-g could be replaced by the addition of (i) IL-2 or K562-activated natural killer (NK) cells or (ii) resting NK cells in the presence of anti-MHC class I antibody. Taken together, our results show a dialogue between NK and tumor cells leading to IFN-g secretion, which in turn associates with monocyte-derived IL-1b and TNF-a to drive production of CCL22 by tumor cells and subsequent recruitment of T reg . As one validation of this conclusion in primary breast tumors, we showed that NK cells and macrophages tend to colocalize within tumors. In summary, our findings suggest that at early times during tumorigenesis, the detection of tumor cells by innate effectors (monocytes and NK cells) imposes a selection for CCL22 secretion that recruits T reg to evade this early antitumor immune response.

Cancer cell-derived IL-1α induces CCL22 and the recruitment of regulatory T cells

“…These findings are seemingly contradictory to a former study reporting CCL22 upregulation in human breast cancer cell lines upon culture in PBMC supernatants. 39 This may, however, be explained by the addition of IFNg in incubation protocols of that study, which is known to induce CCL22 in epithelial cells. 41,42 Although the regulation of CCL22 has been investigated in several further studies, 3,6,35,43 we describe here for the first time its induction through IL-1a by cancer cells.…”

“…Data displayed were obtained in two independent experiments. immune cells can secrete CCL22, 38,39 in most other types of cancer, however, CCL22 is secreted by tumor-infiltrating immune cells. 40 In HCC, CCL22 upregulation was shown in HBVinfected HCC cell lines and HBVC primary HCC tumors on mRNA level.…”

TLR4 has a TP53-dependent dual role in regulating breast cancer cell growth

“…Our data also indicate that the TP53 mutational context of a breast tumor epithelial cell can significantly affect the tumor microenvironment by regulating the extracellular cytokine secretions of tumor cells, and have a profound effect on response to targeted therapy. The tumor growth and immunomodulatory roles of TLR4 may be integrated, because cytokines in the tumor microenvironment play an important role in attracting or evading antitumor immunity (23). Therefore, the roles of TLR4 in regulating tumor growth and cytokine secretion may act together in promoting the growth of epithelial TP53 mutant tumor cells and in suppressing any antitumor immune response.…”

Regulatory T cells in cancer immunotherapy

“…For this purpose, surface molecules expressed specifically or selectively on effector Treg cells are good targets. For example, CCR4 is predominantly expressed by effector Treg cells, not by naive Treg cells and Th2 cells which do not contribute significantly to tumor immunity regulation in humans [67], and Treg migration and infiltration into various tumor tissues appear to be dependent on the expression of CCR4 ligands (i.e., CCL17 and CCL22) produced by tumor cells or infiltrating macrophages [48,68]. Indeed, the use of anti-CCR4 antibody has been shown to be effective in depleting effector Treg cells selectively and augmenting the induction of tumor antigen-specific CD4 + and CD8 + T cells in vivo [67].…”