rWTC-MBTA: autologous vaccine prevents metastases via antitumor immune responses

Abstract

Background Autologous tumor cell-based vaccines (ATVs) aim to prevent and treat tumor metastasis by activating patient-specific tumor antigens to induce immune memory. However, their clinical efficacy is limited. Mannan-BAM (MB), a pathogen-associated molecular pattern (PAMP), can coordinate an innate immune response that recognizes and eliminates mannan-BAM-labeled tumor cells. TLR agonists and anti-CD40 antibodies (TA) can enhance the immune response by activating antigen-presenting cells (APCs) to present tumor antigens to the adaptive immune system. In this study, we investigated the efficacy and mechanism of action of rWTC-MBTA, an autologous whole tumor cell vaccine consisting of irradiated tumor cells (rWTC) pulsed with mannan-BAM, TLR agonists, and anti-CD40 antibody (MBTA), in preventing tumor metastasis in multiple animal models. Methods The efficacy of the rWTC-MBTA vaccine was evaluated in mice using breast (4T1) and melanoma (B16-F10) tumor models via subcutaneous and intravenous injection of tumor cells to induce metastasis. The vaccine’s effect was also assessed in a postoperative breast tumor model (4T1) and tested in autologous and allogeneic syngeneic breast tumor models (4T1 and EMT6). Mechanistic investigations included immunohistochemistry, immunophenotyping analysis, ELISA, tumor-specific cytotoxicity testing, and T-cell depletion experiments. Biochemistry testing and histopathology of major tissues in vaccinated mice were also evaluated for potential systemic toxicity of the vaccine. Results The rWTC-MBTA vaccine effectively prevented metastasis and inhibited tumor growth in breast tumor and melanoma metastatic animal models. It also prevented tumor metastasis and prolonged survival in the postoperative breast tumor animal model. Cross-vaccination experiments revealed that the rWTC-MBTA vaccine prevented autologous tumor growth, but not allogeneic tumor growth. Mechanistic data demonstrated that the vaccine increased the percentage of antigen-presenting cells, induced effector and central memory cells, and enhanced CD4+ and CD8+ T-cell responses. T-cells obtained from mice that were vaccinated displayed tumor-specific cytotoxicity, as shown by enhanced tumor cell killing in co-culture experiments, accompanied by increased levels of Granzyme B, TNF-α, IFN-γ, and CD107a in T-cells. T-cell depletion experiments showed that the vaccine’s antitumor efficacy depended on T-cells, especially CD4+ T-cells. Biochemistry testing and histopathology of major tissues in vaccinated mice revealed negligible systemic toxicity of the vaccine. Conclusion The rWTC-MBTA vaccine demonstrated efficacy in multiple animal models through T-cell mediated cytotoxicity and has potential as a therapeutic option for preventing and treating tumor metastasis with minimal systemic toxicity.

Application of toll-like receptors (TLRs) and their agonists in cancer vaccines and immunotherapy

“…In our preceding study, in a colon carcinoma preclinical mouse model, compared to control or injecting irradiated whole tumor cells alone, we found that subcutaneous injection of the rWTC-MBTA vaccine (irradiated whole tumor cells mixed with MBTA) caused a substantial decrease in tumor volumes and improved overall survival ( 199 ). In one of our recently published manuscripts, we demonstrated that the rWTC-MBTA vaccine effectively inhibited the metastasis and impeded the growth of tumors in animal models of both breast cancer and melanoma ( 202 ). Additionally, in a therapeutically mimicking postoperative model of breast cancer, it prevented the metastasis of residual tumors and extended the survival ( 202 ).…”

“…In one of our recently published manuscripts, we demonstrated that the rWTC-MBTA vaccine effectively inhibited the metastasis and impeded the growth of tumors in animal models of both breast cancer and melanoma ( 202 ). Additionally, in a therapeutically mimicking postoperative model of breast cancer, it prevented the metastasis of residual tumors and extended the survival ( 202 ). Our results also demonstrated that the rWTC-MBTA vaccine effectively prevented the growth of autologous tumors but rendered ineffective against allogeneic tumors ( 202 ).…”

“…This vaccine is called rWTC-MBTA, comprising of irradiated autologous tumor cells (rWTC) mixed with mannan-BAM, TLR agonists, and anti-CD40 antibody (MBTA) ( 199 – 202 ). This vaccination strategy was initiated with the utilization of TLR agonists accompanied by concurrent labeling of tumor cells with phagocytosis-inducing ligands leading to enhanced recognition of the tumor cells by the different immune cells ( 203 , 204 ).…”

“…The Th1 family of inflammatory cytokines endorse the switching of CD4 + T cells from Th2 subtype to Th1 subtype, increase CD8 + effector T-cell responses, and impede the immunosuppressive activity of Treg cells ( 126 ). The MBTA vaccine approach manipulates the TME, by the application of TLR agonists to turn the cold TME to hot, and it was evident by the efficacy of rWTC-MBTA on curbing immunogenically cold tumors like glioblastoma multiforme (GBM) ( 200 ) or triple-negative breast cancer ( 202 ).…”

rWTC‐MBTA Vaccine Induces Potent Adaptive Immune Responses Against Glioblastomas via Dynamic Activation of Dendritic Cells

“…[ 21 ] This vaccine strategy inhibited tumor growth in the CT26‐colon carcinoma model, an immunologically “hot” tumor model, [ 21 , 22 ] and also prevented early metastasis in preclinical models. [ 23 ] However, it is still unknown whether this strategy can treat immunologically “cold” tumors such as GBM, considering the specialized immune microenvironment in the brain. [ 24 ] Also, the detailed effects of the rWTC‐MBTA vaccine on DC subsets and TME have not been well characterized.…”