PD-1 blockade restores helper activity of tumor-infiltrating, exhausted PD-1hiCD39+ CD4 T cells

Abstract

Tumor antigen–specific CD4 T cells accumulate at tumor sites, evoking their involvement in antitumor effector functions in situ. Contrary to CD8 cytotoxic T lymphocyte exhaustion, that of CD4 T cells remains poorly appreciated. Here, using phenotypic, transcriptomic, and functional approaches, we characterized CD4 T cell exhaustion in patients with head and neck, cervical, and ovarian cancer. We identified a CD4 tumor-infiltrating lymphocyte (TIL) population, defined by high PD-1 and CD39 expression, which contained high proportions of cytokine-producing cells, although the quantity of cytokines produced by these cells was low, evoking an exhausted state. Terminal exhaustion of CD4 TILs was instated regardless of TIM-3 expression, suggesting divergence with CD8 T cell exhaustion. scRNA-Seq and further phenotypic analyses uncovered similarities with the CD8 T cell exhaustion program. In particular, PD-1 hi CD39 + CD4 TILs expressed the exhaustion transcription factor TOX and the chemokine CXCL13 and were tumor antigen specific. In vitro, PD-1 blockade enhanced CD4 TIL activation, as evidenced by increased CD154 expression and cytokine secretion, leading to improved dendritic cell maturation and consequently higher tumor-specific CD8 T cell proliferation. Our data identify exhausted CD4 TILs as players in responsiveness to immune checkpoint blockade.

Potential Role of CXCL13/CXCR5 Signaling in Immune Checkpoint Inhibitor Treatment in Cancer

“…Although the effects of ICI have been thoroughly explored in CD8 + T cells, the roles played by CD4 + T cells in response to ICI remain poorly understood. Balança et al studied exhausted CD4 + T cells in head and neck, cervical, and ovarian cancers [ 95 ]. With exhausted CD4 + T cells defined as those cells presenting high PD-1 and CD39 levels, which were found to secrete CXCL13 and express the transcription factor thymocyte selection-associated high mobility group box (TOX).…”

“…Balança et al studied the role of CD4 + T cells in immunotherapy during the attack on cancer cells [ 95 ]. They applied single-cell RNA sequencing analysis to patient-derived samples of head and neck, cervical, and ovarian cancer to detect the expression of transcription factor TOX and the chemokine CXCL13.…”

CD4+ T cells in classical Hodgkin lymphoma express exhaustion associated transcription factors TOX and TOX2

“… 33–35 More important in the setting of our study, they are essential for the development of Tfh cells and the induction of exhaustion in both CD4+ and CD8+ T cells. 36–41 Corresponding with our DEG, TOX can induce the expression of the Tfh defining chemokine CXCL13, and immune checkpoint molecule PD-1, which is a well-established marker of exhaustion. 42 , 43 Of note, in our immunohistochemistry analysis, T cells expressing TOX and/or TOX2 outnumbered cells expressing CXCL13 and PD-1, confirming a previous report that the exhaustion phenotype is a dominant feature in the cHL TME.…”

Harnessing Antitumor CD4+ T Cells for Cancer Immunotherapy

“…More recently, CD39 has been identified as a marker for tumor-specific CD4 + T cell population in human TILs suggesting that CD39 could be used to identify, isolate and expand tumor-reactive T cell population before ACT immunotherapy [ 183 ]. Since another team has demonstrated that this tumor-specific CD39 + CD4 + TILs population expresses CXCL13, PD-1 and TOX exhaustion makers and this population could contribute to tumor-specific CD8 + T cell proliferation and DC maturation through in situ reactivation with PD-1 blockade [ 184 ]. In addition to clinical and therapeutic success of TILs, several cytokines were used to enhance ACT efficacy and overcome immunosuppressive TME.…”