CTLA-4 silencing in dendritic cells loaded with colorectal cancer cell lysate improves autologous T cell responses in vitro

Abstract

Dendritic cell (DC)-based immunotherapy has increased interest among anti-cancer immunotherapies. Nevertheless, the immunosuppressive mechanisms in the tumor milieu, e.g., inhibitory immune checkpoint molecules, have been implicated in diminishing the efficacy of DC-mediated anti-tumoral immune responses. Therefore, the main challenge is to overcome inhibitory immune checkpoint molecules and provoke efficient T-cell responses to antigens specifically expressed by cancerous cells. Among the inhibitory immune checkpoints, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expression on DCs diminishes their maturation and antigen presentation capability. Accordingly, we hypothesized that the expression of CTLA-4 on DCs inhibits the T cell-mediated anti-tumoral responses generated following the presentation of tumor antigens by DCs to T lymphocytes. In this study, we loaded colorectal cancer (CRC) cell lysate on DCs and inhibited the expression of CTLA-4 by small interfering RNA (siRNA) in them to investigate the DCs’ functional and phenotypical features, and T-cell mediated responses following DC/T cell co-culture. Our results demonstrated that blockade of CTLA-4 could promote stimulatory properties of DCs. In addition, CTLA-4 silenced CRC cell lysate-loaded DCs compared to the DCs without CTLA-4 silencing resulted in augmented T cell proliferation and cytokine production, i.e., IFN-γ and IL-4. Taken together, our findings suggest CTLA-4 silenced CRC cell lysate-loaded DCs as a promising therapeutic approach however further studies are needed before this strategy can be used in clinical practice.

Analysis of single nuclear chromatin accessibility reveals unique myeloid populations in human pancreatic ductal adenocarcinoma

“…Thus, while dendritic cells are critical for T cell activation, 99,37 overactivation can be detrimental and cause immunosuppression. 37,101,102 Such observations point to the heterogenous nature of the myeloid cell infiltrate in PDAC, which we demonstrate here. This heterogeneity is driven by the interplay between the many factors comprising the PDAC TME, such as tumour cells, stromal cells, immune cells and soluble factors, which can differently impact myeloid populations.…”

“…Additional clinical trials have utilised CD40 agonism to promote antigen presenting cells to stimulate a T cell response, 100 again with limited efficacy. This may be in part due to dendritic cells also having an immunosuppressive function in tumours by expressing cytotoxic T lymphocyte‐associated protein 4 (CTLA‐4) 101 or programmed cell death protein 1 (PD‐1), 102 preventing antigen presentation and T cell activation. Thus, while dendritic cells are critical for T cell activation, 99,37 overactivation can be detrimental and cause immunosuppression 37,101,102 .…”

“…This may be in part due to dendritic cells also having an immunosuppressive function in tumours by expressing cytotoxic T lymphocyte‐associated protein 4 (CTLA‐4) 101 or programmed cell death protein 1 (PD‐1), 102 preventing antigen presentation and T cell activation. Thus, while dendritic cells are critical for T cell activation, 99,37 overactivation can be detrimental and cause immunosuppression 37,101,102 . Such observations point to the heterogenous nature of the myeloid cell infiltrate in PDAC, which we demonstrate here.…”

Recent advances in mRNA‐based vaccine for cancer therapy; bench to bedside

“…According to a study, DCs treated with CRC cell lysate exhibit significantly improved maturation and stimulatory activity following CTLA-4 knockdown. 88 Additionally, compared to DCs that are merely pulsed with tumor lysate, these transformed DCs can significantly increase the activation and cytokine secretion of co-cultured T-cells. It is recommended that this anticancer therapy technique be further explored in preclinical investigations to validate this notion in light of these findings.…”

“…While other studies have loaded DCs with tumor lysates or inhibited them for inhibitory immunological checkpoints, no research has examined CTLA‐4 silencing in conjunction with tumor cell lysate loading on DCs. According to a study, DCs treated with CRC cell lysate exhibit significantly improved maturation and stimulatory activity following CTLA‐4 knockdown 88 . Additionally, compared to DCs that are merely pulsed with tumor lysate, these transformed DCs can significantly increase the activation and cytokine secretion of co‐cultured T‐cells.…”