Intratumoral FoxP3+Helios+ Regulatory T Cells Upregulating Immunosuppressive Molecules Are Expanded in Human Colorectal Cancer

Abstract

Regulatory T cells (Tregs) can be antitumorigenic or pro-tumorigenic in colorectal cancer (CRC) depending on the presence of different Treg subsets with various immunosuppressive molecules. Some studies reported the phenotypic characteristics of tumor-infiltrating immune cells in CRC, but limited studies have focused on the co-expression of suppressive molecules on immune cells. The aim of this study was to characterize immune cells in the tumor microenvironment (TME), compared to paired adjacent non-tumor colon tissue of CRC patients. Additionally, we investigated co-expression of immunosuppressive molecules on different Treg subsets in the TME, normal colon tissue, and peripheral blood of CRC patients and healthy donors. In this preliminary study, we report that the majority of CD3+ T cells in the TME are CD4+ T cells with high co-expression of programmed death 1 (PD-1)/cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and PD-1/CD39 molecules. Levels of CD4+FoxP3+Helios+ Tregs were significantly increased in the TME. Furthermore, we observed increased levels of PD-1/CTLA-4 and PD-1/CD39 co-expressing cells within FoxP3+Helios+ and FoxP3+Helios− Treg subsets, indicative of their potent immunosuppressive potential. These results suggest synergistic associations between PD-1/CTLA-4 and PD-1/CD39 in dampening T-cell activation and function along with suppressing tumor-specific immune responses, suggesting that dual blockade of these molecules could be a more effective strategy for inducing antitumor immune responses in CRC.

Immune checkpoint inhibitors in cancer therapy: a focus on T‐regulatory cells

“…54 It has been reported that in patients with breast cancer and CRC, Tregs co-express high levels of PD-1 and CTLA-4 within the TME to create an immune-subversive environment for the survival of tumor cells. 17,50 PD-L1 can alter T-cell differentiation pathway by reducing CD4 + IFNc + Th1 and CD4 + IL17 + Th17 and increasing Treg activation probably by inhibiting the PI3K/AKT/ mTOR signaling pathway. 78 Additionally, it has been reported that upregulation of PD-L1 in tumor cells and FOXP3 in intratumoral Tregs synergistically upregulates their expression in the TME of patients with breast cancer, which favors tumor immune evasion.…”

“…45 ICI strategies have shown significant success in clinical studies of nonsmall-cell lung cancer, renal cell carcinoma, and melanoma, even though the responses are limited to 10-20%. 46,47 Several studies reported that the majority of intratumoral Tregs upregulate immune checkpoint molecules 17,[48][49][50] , making Tregs as a key target for ICI. Despite the clinical success to date, the exact mechanism of ICI is still elusive.…”

DNA methylation of immune checkpoints in the peripheral blood of breast and colorectal cancer patients

“…Studies reported that expressions of multiple ICs including PD-1 and CTLA-4 were elevated in the circulation of both PBC 19,20 and CRC. 21 We have recently reported that the promoter demethylation and post-translational histone modifications play a role in the regulation of immune checkpoints in PBC and CRC tumor tissues. 12,13 Herein, we investigated the expression of various ICs/ligand and found that multiple immune checkpoints were elevated in the circulation of both PBC and CRC.…”

Regulatory T‐cell heterogeneity and the cancer immune response

“…PD‐1‐expressing FOXP3 + Tregs had genetic signatures that correlated with exhaustion and Treg activation 62 . Tregs in tumours of CRC patients also upregulated immunosuppressive markers present on populations of exhausted effector T cells, but these FOXP3 + Tregs were proposed to be activated and highly suppressive due to high expression of CD39 and LAP 63 …”

“…62 Tregs in tumours of CRC patients also upregulated immunosuppressive markers present on populations of exhausted effector T cells, but these FOXP3 + Tregs were proposed to be activated and highly suppressive due to high expression of CD39 and LAP. 63 Other immune cells from CRC tumours are able to modulate the function of Tregs. FOXP3 + Tregs from CRC tissue, compared to the same cells from non-tumour tissue, had upregulated expression of genes associated with the promotion of inflammation.…”