Phototherapy and anti-GITR antibody-based therapy synergistically reinvigorate immunogenic cell death and reject established cancers

Phototherapy and immunogenic cell death (ICD) are powerful strategies to fight cancer. However, their therapeutic outcomes are diminished by immunosuppressive and hypoxia microenvironment. Herein, a photo-based, immunomodulating and hypoxia-alleviated nanosystem, PDA-ICG@CAT-DTA-1, is proposed to achieve the synergism between phototherapy and immunotherapy. Catalase (CAT) and anti-GITR antibody (DTA-1) are loaded to photothermal agent and photosensitizer composed PDA-ICG nanoparticles. The PDA-ICG@CAT-DTA-1 exhibits intrinsic local hyperthermia and enhanced ROS generation in tumor, and abrogates tumor immune suppression. It results in reduction of intratumoral FOXP3⁺ regulatory T cells (4.3-fold) and increase of CD4⁺ effector T cells (1.5-fold) compare with the control, and promotes damage associated molecular patterns generation to reinvigorate ICD effect. The potent antitumor of PDA-ICG@CAT-DTA-1 is proved in 4T1 bilateral tumor-bearing mice, with inhibition ratio of 95.1% for primary cancers and 68.7% for abscopal cancers. Our findings highlight great promise of the constructed versatility nanosystem to fix bottlenecks for cancer therapy.

Agonist anti-GITR antibody significantly enhances the therapeutic efficacy of Listeria monocytogenes-based immunotherapy

Background

We previously demonstrated that in addition to generating an antigen-specific immune response, Listeria monocytogenes (Lm)-based immunotherapy significantly reduces the ratio of regulatory T cells (Tregs)/CD4⁺ and myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment. Since Lm-based immunotherapy is able to inhibit the immune suppressive environment, we hypothesized that combining this treatment with agonist antibody to a co-stimulatory receptor that would further boost the effector arm of immunity will result in significant improvement of anti-tumor efficacy of treatment.

Methods

Here we tested the immune and therapeutic efficacy of Listeria-based immunotherapy combination with agonist antibody to glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) in TC-1 mouse tumor model. We evaluated the potency of combination on tumor growth and survival of treated animals and profiled tumor microenvironment for effector and suppressor cell populations.

Results

We demonstrate that combination of Listeria-based immunotherapy with agonist antibody to GITR synergizes to improve immune and therapeutic efficacy of treatment in a mouse tumor model. We show that this combinational treatment leads to significant inhibition of tumor-growth, prolongs survival and leads to complete regression of established tumors in 60% of treated animals. We determined that this therapeutic benefit of combinational treatment is due to a significant increase in tumor infiltrating effector CD4⁺ and CD8⁺ T cells along with a decrease of inhibitory cells.

Conclusion

To our knowledge, this is the first study that exploits Lm-based immunotherapy combined with agonist anti-GITR antibody as a potent treatment strategy that simultaneously targets both the effector and suppressor arms of the immune system, leading to significantly improved anti-tumor efficacy. We believe that our findings depicted in this manuscript provide a promising and translatable strategy that can enhance the overall efficacy of cancer immunotherapy.