Expression of immune checkpoints and T cell exhaustion markers in early and advanced stages of colorectal cancer

Abstract

Despite recent advances in colorectal cancer (CRC) treatment, a large proportion of patients show limited responses to therapies, especially in advanced stages. There is an urgent need to identify prognostic biomarkers and/or therapeutic targets in advanced stages, aiming to improve the efficacy of current treatments. We aimed to determine prognostic biomarkers in tumor tissue and circulation of CRC patients, with a special focus on T cell exhaustion markers. We found that mRNA levels of PD-1, TIM-3, CTLA-4, TIGIT, CD160, CD244, KLRG1, TOX2, TOX3, Ki-67, and PRDM1 were elevated in CRC tumor tissues. We also investigated differences in gene expression between early and advanced disease stages. We found that TOX and potentially TIM-3, CTLA-4, VISTA, TIGIT, KLRG1, TOX2, SIRT1, Ki-67, and Helios mRNA levels in tumor tissue were elevated in advanced disease stages, suggesting their potential roles in CRC progression. In contrast, PD-1 and CD160 levels in tumor tissue were downregulated in advanced stages. In the circulation of CRC patients, mRNA levels of PD-1, VISTA and LAG-3 were higher than those of healthy individuals. Moreover, in circulation, PD-1, CTLA-4 and TIGIT mRNA levels were reduced in advanced stages. Interestingly, levels of PD-1 in both tumor tissue and circulation were reduced in advanced stages, suggesting that targeting PD-1 in patients with advanced stages could be less effective. Altogether, these findings suggest some potential T cell exhaustion markers that could be utilized as prognostic biomarkers and/or therapeutic targets for CRC. However, further investigations and validations in larger cohorts are required to confirm these findings.

Differential gene expression of tumor-infiltrating CD4 + T cells in advanced versus early stage colorectal cancer and identification of a gene signature of poor prognosis

“…35 Additionally, upregulation of immune checkpoints including PD-1, CTLA-4, and TIM-3 and alterations in transcriptional/metabolic pathways are considered as the hallmark of T cell exhaustion. 36 In concordance with these reports, we found that the majority of T-cell exhaustion markers, including the expression of PDCD1 (gene for PD-1), TOX2 and MKI67, were upregulated in the early stages of CRC, compared with advanced stages. These data evidently discriminate phenotypical and functional characteristics of CD4 + TILs in early and advanced stages of CRC.…”

Differential gene expression of tumor-infiltrating CD8+T cells in advanced versus early-stage colorectal cancer and identification of a gene signature of poor prognosis

“…Together, these data potentially implicate that CD8 + TILs in advanced stages have not only impaired activation and effector functions, but also limited capacity of cell proliferation and differentiation to memory T cells. Moreover, the downregulation of PDCD1 gene (which encodes PD-1; IC) in CD8 + TILs from advanced stages is parallel with our recent findings in bulk tumors from patients with CRC with advanced stages, 26 implicating that anti-PD-1/ PD-L1 therapies may not be effective in patients with CRC with advanced stages.…”

“… 54 Furthermore, TOX3 , T cell exhaustion marker 56 ; FOXP3 , master transcription factor for Treg differentiation 57 ; and CCR6 , chemokine receptor associated with Treg chemotaxis to tumor tissues, 58 were upregulated in advanced stages, suggesting that cytotoxic T cell dysfunction in patients with CRC with advanced stages could be associated with T cell exhaustion and CD8 + Treg differentiation. On the other hand, activation marker PDCD1 26 59 ; inflammatory cytokines IL17A, IL7F and IL22 60 , TCR stimulation-related gene HLA-DRA 61 62 ; and inducers of programmed cell death and CD8 + T cell-mediated apoptosis FASLG and TNFRSF9 , 63 64 were downregulated in advanced disease stages, suggesting that CD8 + TILs in advanced stages could be dysfunctional and may lack the capacity of inducing antitumor activities. Together, these data potentially implicate that CD8 + TILs in advanced stages have not only impaired activation and effector functions, but also limited capacity of cell proliferation and differentiation to memory T cells.…”

“…Tumor tissue specimens were processed and stored, as we have previously described. 26 27 Using mechanical disaggregation, cells were dissociated from bulk tumor tissues, and single cell suspensions were obtained for subsequent experiments as we have previously described. 27 The experimental pipeline is shown in figure 1A .…”

Tumor-Infiltrating Lymphoid Cells in Colorectal Cancer Patients with Varying Disease Stages and Microsatellite Instability-High/Stable Tumors

“…In contrast, ICOS serves as a co-stimulatory molecule with opposing effects on T cell activation, proliferation and functionality [ 19 ]. The prognostic significance of ICs in CRC has been explored previously [ 11 , 40 ]. We identified that only CD8 + T cells expressing different ICs were found at lower levels in CRC patients with advanced stage disease.…”