CCR2 Influences T Regulatory Cell Migration to Tumors and Serves as a Biomarker of Cyclophosphamide Sensitivity

Abstract

The CCL2 chemokine receptor CCR2 drives cancer by mediating the recruitment of monocytes and myeloid-derived suppressor cells to the tumor microenvironment. In this study, we extend the significance of CCR2 in this setting by identifying a new role for it in mediating recruitment of CD4 T regulatory cells (Treg). Following tumor initiation, an expanded population of CCR2 Tregs required CCR2 expression to traffic between draining lymph nodes (dLN) and the tumor. This Treg subset was enriched in the fraction of tumor antigen-specific cells in the dLN, where they displayed an activated immunosuppressive phenotype. Notably, in mouse models, low-dose cyclophosphamide treatment preferentially depleted CCR2 Treg, enhancing priming of tumor-specific CD8 T cells. In the MMTV-PyMT transgenic mouse model of breast cancer and in oral squamous cell carcinoma patients, tumor development was associated with decreased blood frequency and inversely increased tumor frequency of CCR2 Tregs. Our results define a novel subset of CCR2 Treg involved in tumoral immune escape, and they offer evidence that this Treg subset may be preferentially eradicated by low-dose cyclophosphamide treatment. Cancer Res; 76(22); 6483-94. ©2016 AACR.

Blocking inflammation to improve immunotherapy of advanced cancer

“…61 Of note, low-dose cyclophosphamide can also induce Treg depletion by inhibiting their proliferation and intratumoral migration and to dampen their activity by decreasing the FOXP3 and GITR expression. [62][63][64][65][66] Consistent with the above findings, a very recent review 67 discussed cyclooxygenase-2 inhibitors among drugs under investigation in combination with anti-PD-1 antibody immunotherapy.…”

“…More recently, we demonstrated the effectiveness of combination therapy with the anti‐PD‐1 antibody, nivolumab, and cyclophosphamide, an immunomodulatory chemotherapy agent that down‐regulates macrophage activity and inhibits pro‐inflammatory cytokine synthesis, thereby synergistically enhancing the action of immunotherapy . Of note, low‐dose cyclophosphamide can also induce Treg depletion by inhibiting their proliferation and intratumoral migration and to dampen their activity by decreasing the FOXP3 and GITR expression …”

Analysis of monocyte infiltration in MPTP mice reveals that microglial CX3CR1 protects against neurotoxic over-induction of monocyte-attracting CCL2 by astrocytes

“…Likewise, while in the brain CCR2 is mainly expressed by infiltrating monocytes, other cell types (even neurons) might express low CCR2 levels (not detected by CCR2-GFP) and mediate the neurotoxic effect of CCL2 over-induction. Of note, CCR2 can also be expressed by a (minor) subpopulation of T lymphocytes (subsets of Treg cells) [46]; however, all CCR2-GFP + cells we detected in the affected SNpc were also positive for CD11b or Iba1, suggesting monocytes.…”

Intratumoral regulatory T cells: markers, subsets and their impact on anti‐tumor immunity

“…However, recent studies have demonstrated a chemotactic role for CCR2 in T cells during inflammation . Interestingly, a subset of CCR2 + Treg cells was enriched in both tumor and draining lymph nodes of mice bearing transplantable OVA‐expressing murine sarcoma (MCA‐OVA), but CCR2‐deficient Treg cells failed to infiltrate the TME . Furthermore, CCR2‐deficient Treg cells resulted in reduced CD25 expression, rendering them less suppressive, suggesting an alternative non‐chemotactic role for CCR2 in Treg cells.…”