T-cell epitope strength in WAP-T mouse mammary carcinomas is an important determinant in PD1/PD-L1 immune checkpoint blockade therapy

Suppression of 4.1R enhances the potency of NKG2D-CAR T cells against pancreatic carcinoma via activating ERK signaling pathway

Pancreatic carcinoma (PC) is one of the most common malignancies. Chimeric antigen receptor (CAR)-modified T cells has achieved remarkable efficacy in the treatment of hematological malignancies. However, lack of tumor-specific targets and the existence of inhibitory factors limit the function of CAR T cells when treating solid tumors. 4.1R has been reported to suppress the anti-tumor activity of T cell responses. In this study, we investigated the anti-tumor activity of 4.1R deletion in natural killer group 2D (NKG2D)-CAR T cells against PC. The CAR T cells were obtained by transfecting T cells with lentiviral vector carrying NKG2D-CAR, NC-NKG2D-CAR, or KD2-NKG2D-CAR. In vitro, NKG2D-CAR T cells showed higher cytotoxicity than Mock T cells. However, compared to NKG2D-CAR T cells, furtherly higher cytotoxicity against PC cells in a dose-dependent manner was found in KD2-NKG2D-CAR T cells. In addition, the proliferation rate and cytotoxic activity of KD2-NKG2D-CAR T cells were significantly higher than those of NKG2D-CAR T cells. Besides, the inhibitory receptors PD-1 and TIM-3 were expressed in lower level on KD2-NKG2D-CAR T cells. In vivo, KD2-NKG2D-CAR T cells suppressed tumor growth more effectively in a xenograft model compared to NKG2D-CAR T cells. Mechanistically, 4.1R regulated CAR T cell function via activating ERK signaling pathway. Therefore, the study provides a new idea to enhance the anti-tumor efficiency of CAR T therapy.

Infiltration of Immune Competent Cells into Primary Tumors and Their Surrounding Connective Tissues in Xenograft and Syngeneic Mouse Models

To fight cancer more efficiently with cell-based immunotherapy, more information about the cells of the immune system and their interaction with cancer cells in vivo is needed. Therefore paraffin wax embedded primary breast cancers from the syngeneic mouse WAP-T model and from xenografted tumors of breast, colon, melanoma, ovarian, neuroblastoma, pancreatic, prostate, and small cell lung cancer were investigated for the infiltration of immunocompetent cells by immunohistochemistry using antibodies against leukocyte markers. The following markers were used: CD45 as a pan-leukocyte marker, BSA-I as a dendritic cell marker, CD11b as an NK cell marker, and CD68 as a marker for macrophages. The labeled immune cells were attributed to the following locations: adjacent adipose tissue, tumor capsule, intra-tumoral septae, and cancer cells directly. In xenograft tumors, the highest score of CD45 and CD11b positive, NK, and dendritic cells were found in the adjacent adipose tissue, followed by lesser infiltration directly located at the cancer cells themselves. The detected numbers of CD45 positive cells differed between the tumor entities: few infiltrating cells in breast cancer, small cell lung cancer, neuroblastoma, a moderate infiltration in colon cancer, melanoma and ovarian cancer, strongest infiltration in prostate and pancreatic cancer. In the syngeneic tumors, the highest score of CD45 and CD11b positive, NK and dendritic cells were observed in the tumor capsule, followed by a lesser infiltration of the cancer tissue. Our findings argue for paying more attention to investigate how immune-competent cells can reach the tumor cells directly.

PD-L1/PD-1 axis as a potent therapeutic target in breast cancer

Although both the incidence and the mortality rate of breast cancer is rising, there is no potent and practical option for the treatment of these patients, particularly in advanced stages. One of the most critical challenges for treatment is the presence of complicated and extensive tumor escape mechanisms in the tumor microenvironment. Immune checkpoint molecules are of the main immunosuppressive mechanisms used by cancerous cells to block anti-cancer immune responses. Among these molecules, PD-1 (Programmed cell death) and PD-L1 (programmed cell death-ligand 1) have been considered as worthy therapeutic targets for breast cancer therapy. In this review, we intend to discuss the immunobiology and signaling of the PD-1/PD-L1 axis and highlight its importance as a worthy therapeutic target in breast cancer. We believe that the prognostic value of PD-L1 depends on the breast cancer subtype. Moreover, the combination of PD-1/PD-L1 targeting with immune-stimulating vaccines can be considered as an effective therapeutic strategy in breast cancer.

Antitumor activity of CD56-chimeric antigen receptor T cells in neuroblastoma and SCLC models

The CD56 antigen (NCAM-1) is highly expressed on several malignancies with neuronal or neuroendocrine differentiation, including small-cell lung cancer and neuroblastoma, tumor types for which new therapeutic options are needed. We hypothesized that CD56-specific chimeric antigen receptor (CAR) T cells could target and eliminate CD56-positive malignancies. Sleeping Beauty transposon-generated CD56R-CAR T cells exhibited αβT-cell receptors, released antitumor cytokines upon co-culture with CD56⁺ tumor targets, demonstrated a lack of fratricide, and expression of cytolytic function in the presence of CD56⁺ stimulation. The CD56R-CAR⁺ T cells are capable of killing CD56⁺ neuroblastoma, glioma, and SCLC tumor cells in in vitro co-cultures and when tested against CD56⁺ human xenograft neuroblastoma models and SCLC models, CD56R-CAR⁺ T cells were able to inhibit tumor growth in vivo. These results indicate that CD56-CARs merit further investigation as a potential treatment for CD56⁺ malignancies.

Immunotherapy of WAP-TNP mice with early stage mammary gland tumors

The SV40 transgenic BALB/c mouse based WAP-T/WAP-T_NP model for triple-negative breast cancer allows the analysis of parameters influencing immunotherapeutic approaches. Except for WAP-T_NP tumors expressing the immune-dominant LCMV NP-epitope within SV40 T-antigen (T-Ag_NP) which is not expressed by T-Ag of WAP-T tumors, the tumors are extremely similar. Comparative anti-PD1/PD-L1 immunotherapy of WAP-T and WAP-T_NP mice supported the hypothesis that the immunogenicity of tumor antigen T-cell epitopes strongly influences the success of immune checkpoint blockade therapy, with highly immunogenic T-cell epitopes favoring rapid CTL exhaustion. Here we analyzed the immune response in NP8 mice during early times of tumor development. LCMV infection of lactating NP8 mice induced lifelong tumor protection by memory CTLs. Immunization with LCMV after involution and appearance of T-Ag_NP expressing parity-induced tumor progenitor cells could not cure the mice, as memory CTLs became exhausted. However, immunization significantly prolonged the time of tumor outgrowth. Elimination of exhausted CTLs and of immunosuppressive cells by sub-lethal γ-irradiation, followed by adoptive transfer of NP-epitope specific CTLs into NP8 tumor mice with early lesions, completely prevented tumor outgrowth, when lymphocytes obtained after injection of weakly immunogenic NP8 tumor-derived cells into BALB/c mice were transferred. Transfer of lymphocytes obtained after infection of BALB/c mice with highly immunogenic LCMV into such mice delayed tumor outgrowth for a significant period, but could not prevent it. We conclude that eliminating exhausted CTLs and immune-suppressive cells followed by transfer or generation of low-avidity tumor antigen-specific CTLs might be a promising approach for curative tumor immunotherapy.