Enhancement of antitumor immunity by combining anti-cytotoxic T lymphocyte antigen-4 antibodies and cryotreated tumor lysate-pulsed dendritic cells in murine osteosarcoma

Abstract

Abstract.Immunotherapy with tumor lysate-loaded dendritic cells (DCs) is one of the most promising strategies to induce antitumor immune responses. However, the antitumor activity of cytotoxic T cells may be restrained by their expression of the inhibitory T-cell coreceptor cytotoxic T lymphocyte antigen-4 (CTLA-4). By relieving this restraint, CTLA-4-blocking antibodies promote tumor rejection, but the full scope of their most suitable applications has yet to be fully determined. In the present study, we offer proof of a preclinical concept in a C3H mouse osteosarcoma (LM8) model that CTLA-4 blockade cooperates with cryotreated tumor lysatepulsed DCs in a primary tumor to prevent the outgrowth of lung metastasis. To evaluate immune response activation, we established the following four groups of C3H mice (60 mice in total): i) control immunoglobulin G (IgG)-treated mice; ii) tumor lysate-pulsed DC-treated mice; iii) anti-CTLA-4 antibody-treated mice and iv) tumor lysate-pulsed DC-and anti-CTLA-4 antibody-treated mice. The mice that received the tumor lysate-pulsed DCs and anti-CTLA-4 antibody displayed reduced numbers of regulatory T lymphocytes and increased numbers of CD8 + T lymphocytes inside the metastatic tumor, inhibition of metastatic growth, a prolonged lifetime, reduced numbers of regulatory T lymphocytes in the spleen and high serum interferon-γ levels. Combining an anti-CTLA-4 antibody with tumor lysate-pulsed DCs enhanced the systemic immune response. To the best of our knowledge, these findings document for the first time an effect of the combination of tumor lysate-pulsed DCs and CTLA-4-blocking antibodies in osteosarcoma. We suggest that cryotreated tumor lysatepulsed DCs, although insufficient on their own, may mediate the rejection of metastatic lesions and prevent recurrence of the disease when combined with CTLA-4 blockade in osteosarcoma patients in the clinical setting. IntroductionOsteosarcoma is the most common primary malignant tumor of bone. Remarkable advances in the treatment of osteosarcoma have occurred, including the introduction of adjuvant chemotherapy and appropriate surgical excision (1-4). However, there have also been advances in the field of immunotherapy for the treatment of osteosarcoma that have received less attention (5,6). Following cryotreatment, the necrotic tumor lesion remains within the body, and the release of tumor antigens by dying cells has been hypothesized to activate a tumor-specific immune response via antigen presentation by antigen-presenting cells (APCs) such as dendritic cells (DCs) to T cells (7,8). A number of tumor studies combining immunomodulation methods such as the injection of Toll-like receptor agonists with cryotreatment have demonstrated a synergistic effect on tumor rejection, and this was attributed to the enhanced activation of APC function (9,10). We developed a method using cryotreated tumor tissue and DCs to enhance tumor-specific immunoreactions since DCs are the main APCs initiating cell-mediated immune responses in vivo (11,12).Mon...

Increased CTLA-4+ T cells and an increased ratio of monocytes with loss of class II (CD14+ HLA-DRlo/neg) found in aggressive pediatric sarcoma patients

“…CTLA-4 expression was noted in OS cell lines and patient tumor samples [ 31 ] and CTLA-4 + 49G/A polymorphism was associated with increased risk of developing OS [ 32 ]. Combined treatment with anti-CTLA-4 antibody and tumor lysate-pulsed dendritic cells in mice with OS lead to decreased Tregs and increased CD8 T cells in metastatic tumor leading to decreased metastasis and increased EFS [ 33 ]. Taken together, CTL-4 targeted therapy may be beneficial, and it will be important to evaluate the effect of this therapy based on the expression on T cells or tumor tissue.…”

Dendritic cells combined with anti-GITR antibody produce antitumor effects in osteosarcoma

“…Our aims were to evaluate Tregs by using the Foxp3 and CD4, in the spleens of mice; measure the levels of Foxp3 and determine the numbers of CD8 + T lymphocytes inside the primary and The group treated with the combination of tumor lysate-pulsed DCs and the anti-GITR antibody displayed smaller tumor lesions and the life time was prolonged. Importantly, the result of tumor rejection in the combined therapy group correlated with the intratumor ratio of CD8 + T cells to Tregs (26). This suggests that controlling immunosuppressive factors may facilitate the activity of DCs and CTLs in the tumor.…”

T-Cell-Based Immunotherapy for Osteosarcoma: Challenges and Opportunities

“…To prevent immune-escape and obtain complete control of a carcinoma, combination immunotherapy of CTLA-4 and PD-L1 blockades was investigated in animal models of metastatic osteosarcoma ( 133 ). Combining anti-CTLA-4 antibody and tumor lysate-pulsed DCs can promote antitumor reaction in murine osteosarcomas ( 134 ). These data indicate that combination of CTLA-4 blockade with other immunotherapies against osteosarcoma shows great clinical promise.…”