RCAd-LTH-shPD-L1, a double-gene recombinant oncolytic adenovirus with enhanced antitumor immunity, increases lymphocyte infiltration and reshapes the tumor microenvironment

Abstract

BackgroundWith the successful development of modern immunotherapy, immune checkpoint inhibitors (ICIs) are currently considered potential therapeutic options for patients with cancer. However, the therapeutic potential of ICIs in human cancer is mainly limited by their systemic toxicity and low response rate, which suggests the necessity of local drug delivery with an effective vector and reshaping the immunosuppressive tumor microenvironment (TME) to enhance ICI therapy. Here, we constructed a novel double-gene recombinant oncolytic adenovirus named RCAd-LTH-shPD-L1 based on the RCAd virus platform armed with a DNA fragment encoding an anti-VEGF antibody and shRNA to inhibit PD-L1 expression.MethodsThe correct assembly of RCAd-LTH-shPD-L1 was characterized by analyzing its secretion, antigen specificity, and replication using western blotting, ELISA and quantitative PCR, respectively. The in vitro effects of RCAd-LTH-shPD-L1 on cell proliferation, vasculogenic, and cell migration were assessed. Antitumor effects and therapeutic mechanisms were evaluated in vivo using immunodeficient and humanized immune system mouse models. The TME was studied by ELISA, immunohistochemistry and flow cytometry.ResultsRCAd-LTH-shPD-L1 cells secreted anti-VEGF antibodies and inhibited the expression of PD-L1 in cancer cells. Moreover, RCAd-LTH-shPD-L1 exerted a specific cytotoxic effect on human cancer cells, but not on murine cancer cells or normal human cells. RCAd-LTH-shPD-L1 elicited a more potent antitumor effect in an immunodeficient mouse model and a humanized immune system mouse model than RCAd-shPD-L1, as demonstrated by the significant decrease in tumor growth. Furthermore, RCAd-LTH-shPD-L1 modulated the TME, which led to lymphocyte infiltration and alteration of their immune phenotype, as characterized by downregulation of anoxic factor HIF-1α and angiogenesis marker CD31, upregulation of cytokine such as IFN-γ, IL-6 and IL-12.ConclusionsIn summary, our data demonstrated that the localized delivery of anti-VEGF antibodies and shPD-L1 by engineered RCAd-LTH-shPD-L1 is a highly effective and safe strategy for cancer immunotherapy. Moreover, the data underscore the potential of combining local virotherapy and anti-angiogenic therapy with ICIs as an effective TME therapy for poorly infiltrating tumors.

Ultrasound -Induced Thermal Effect Enhances the Efficacy of Chemotherapy and Immunotherapy in Tumor Treatment

“…The PD-L1/PD-1 checkpoint blockade, although a promising approach, faces challenges due to insufficient CD8 + T cell infiltration and an immunosuppressive tumor microenvironment. 12 , 42 , 53 Transforming “cold tumors“ with inadequate immune cell infiltration into ”hot tumors” represents a crucial strategy for augmenting the effectiveness of immune checkpoint inhibitors. 54–56 Chemotherapy can induce immunogenic cell death (ICD) and elicit the immune response, rendering it a common adjunct to PD-L1/PD-1 checkpoint blockade immunotherapy in clinical settings.…”

“…The disorganized structure gives rise to physiological challenges, such as compromised perfusion and uneven blood flow distribution, which hinder the diffusion of antitumor drugs and impede the infiltration of CD8 + T cells. 11 , 12 Additionally, the aberrant vascular system results in a hypoxic tumor microenvironment, thereby promoting resistance to chemotherapy and exacerbating immunosuppression. The concept of normalizing tumor blood vessels to enhance drug and immune cell penetration was initially proposed by Rakesh K. Jain in 2001.…”