Abstract 4139: TfhX13 cells link breast cancer immune suppression and adaptive memory
Authors: Gu-Trantien Chunyan , Migliori Edoardo , Larsimont Denis , Willard-Gallo Karen 
Published: July 2016

Abstract
Background:
Previously, we identified PD-1hiCD200hiCD4+ follicular helper T (Tfh) cells infiltrating human breast cancer (BC TIL) as principal producers of the B cell chemoattractant CXCL13 and correlated their presence with improved patient outcome. Our recent efforts have focused on understanding the relationship between Tfh, Th1 and Treg BC TIL, investigating the role(s) that CXCL13+CD4+ TIL play in tumor immunity and determining the condition(s) that favor their differentiation.
Methods:
Ten-color flow cytometry was used to characterize CD4+ TIL subpopulations in fresh tissues. Confocal microscopy was employed to study the in situ interaction between CXCL13+CD4+ T cells and B cells. CXCL13 was induced in normal PBMC in vitro.
Results:
Our data reveal that an exacerbated Treg response accompanies high CXCL13 expression within the activated CD4+ TIL compartment in BC. Th1 responses, using IFN-γ expression as a barometer, are limited. CXCL13+CD4+ TIL display both similar and distinct characteristics compared to their tonsillar counterparts. Tumor bed-localized CXCL13+ TIL, external to tertiary lymphoid structure (TLS) germinal centers (GC), are abundant in some tumors with extensive lymphoid infiltrates. Based on our observations, we designate the CXCL13+CD4+ TIL as TfhX13 cells.
A combination of PD-1 and ICOS can clearly segregate the CD4+ TIL into three distinct subpopulations: PD-1loICOSlo, PD-1hiICOSint and PD-1intICOShi. The PD-1hiICOSint TIL are enriched in TfhX13 and Th1 cells while the PD-1intICOShi TIL are principally FoxP3hi Treg. A linear correlation is observed between these two TIL subpopulations in 90% of BC while the remaining 10% contain an unbalanced, higher level of PD-1intICOShi Treg. qRT-PCR data confirmed the significant positive prognostic value of CXCL13 gene expression with ICOS expression signaling the adverse effects of Treg cell dominance observed in some BC. TfhX13 TIL abundance appears to parallel both a GC and post-TLS memory B cell presence. Confocal microscopy revealed TfhX13 TIL interact directly with B cells and plasma cells, potentially guiding B cell migration through the tumor and promoting TLS formation with functional GC. Finally, we show that IL-2 deprivation is critical for inducing CXCL13 while TGF-β1 treatment reduces IFN-γ and increases FoxP3 expression in normal CD4+ T cells.
Conclusion:
IL-2 consumption by Treg cells was shown to be essential for murine Tfh cell development and a subsequent GC response. Supported by this observation, our data indicate that TfhX13 cell differentiation is an important element of the Tfh cell program and suggests their propagation in BC occurs in response to Treg accumulation. CXCL13 expression may activate adaptive memory responses dependent upon in situ B cell maturation and thereby initiate a secondary attempt at protective anti-tumor immunity in the face of Treg-mediated immune suppression.
Citation Format: Chunyan Gu-Trantien, Edoardo Migliori, Denis Larsimont, Karen Willard-Gallo. TfhX13 cells link breast cancer immune suppression and adaptive memory. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4139.