Enhanced systemic antitumor efficacy of PD-1/PD-L1 blockade with immunological response induced by photodynamic therapy

BACKGROUND

Photodynamic therapy (PDT) is an antitumor therapy and has traditionally been regarded as a localized therapy in itself. However, recent reports have shown that it not only exerts a direct cytotoxic effect on cancer cells but also enhances body's tumor immunity. We hypothesized that the immunological response induced by PDT could potentially enhance the efficacy of programmed death-1 (PD-1) / programmed death-ligand 1 (PD-L1) blockade.

METHODS

The cytotoxic effects of PDT on colon 26 cells were investigated in vitro using the WST assay. We investigated whether the antitumor effect of anti-PD-1 antibodies could be amplified by the addition of PDT. We performed combination therapy by randomly allocating tumor-bearing mice to four treatment groups: control, anti-PD-1 antibodies, PDT, and a combination of anti-PD-1 antibodies and PDT. To analyze the tumor microenvironment after treatment, the tumors were resected and pathologically evaluated.

RESULTS

The viability rate of colon 26 cells decreased proportionally with the laser dose. In vivo experiments for combined PDT and anti-PD-1 antibody treatment, combination therapy showed an enhanced antitumor effect compared with the control. Immunohistochemical findings of the tumor microenvironment 10 days after PDT indicated that the number of CD8+ cells, the area of Iba-1+ cells and the area expressing PD-L1 were significantly higher in tumors treated with combination therapy than in tumors treated with anti-PD-1 antibody alone, PDT alone, or the control.

CONCLUSIONS

PDT increased immune cell infiltration into the tumor microenvironment. The immunological response induced by PDT may enhance the efficacy of PD-1/PD-L1 blockade.

Bacteria Synergized with PD-1 Blockade Enhance Positive Feedback Loop of Cancer Cells-M1 Macrophages-T Cells in Glioma

Cancer immunotherapy is an attractive strategy because it stimulates immune cells to target malignant cells by regulating the intrinsic activity of the immune system. However, due to lacking many immunologic markers, it remains difficult to treat glioma, a representative "cold" tumor. Herein, to wake the "hot" tumor immunity of glioma, Porphyromonas gingivalis (Pg) is customized with a coating to create an immunogenic tumor microenvironment and further prove the effect in combination with the immune checkpoint agent anti-PD-1, exhibiting elevated therapeutic efficacy. This is accomplished not by enhancing the delivery of PD-1 blockade to enhance the effect of immunotherapy, but by introducing bacterial photothermal therapy to promote greater involvement of M1 cells in the immune response. After reaching glioma, the bacteria further target glioma cells and M2 phenotype macrophages selectively, enabling precise photothermal conversion for lysing tumor cells and M2 phenotype macrophages, which thereby enhances the positive feedback loop of cancer cells-M1 macrophages-T cells. Collectively, the bacteria synergized with PD-1 blockade strategy may be the key to overcoming the immunosuppressive glioma microenvironment and improving the outcome of immunotherapy toward glioma.

Co-delivery of dendritic cell vaccine and anti-PD-1 antibody with cryomicroneedles for combinational immunotherapy

Combinational immunotherapy of dendritic cell (DC) vaccines and anti-programmed cell death protein 1 antibodies (aPD1) has been regarded as a promising strategy for cancer treatment because it not only induces tumor-specific T cell immune responses, but also prevents failure of T cell functions by the immune suppressive milieu of tumors. Microneedles have emerged as an innovative platform for efficient transdermal immunotherapies. However, co-delivery of DC vaccines and aPD1 via microneedles has not been studied since conventional microneedle platforms are unsuitable for fragile therapeutics like living cells and antibodies. This study employs our newly invented cryomicroneedles (cryoMNs) to co-deliver DC vaccines and aPD1 for the combinational immunotherapy. CryoMNs are fabricated by stepwise cryogenic micromoulding of cryogenic medium with pre-suspended DCs and aPD1, which are further integrated with a homemade handle for convenient application. The viability of DCs in cryoMNs remains above 85%. CryoMNs are mechanically strong enough to insert into porcine and mouse skin, successfully releasing DCs and aPD1 inside skin tissue after melting. Co-delivery of ovalbumin (OVA)-pulsed DCs (OVA-DCs) and aPD1 via cryoMNs induced higher antigen-specific cellular immune responses compared with the mono-delivery of OVA-DCs or aPD1. Finally, administration with cryoMNs co-encapsulated with OVA-DCs and aPD1 increases the infiltration of effector T cells in the tumor, resulting in stronger anti-tumor therapeutic efficacy in both prophylactic and therapeutic melanoma models compared with administration with cryoMNs loaded with OVA-DCs or aPD1. This study demonstrates the great potential of cryoMNs as a co-delivery system of therapeutic cells and biomacromolecules for combinational therapies.

Optimum fractionation of radiation to combine PD-1 blockade

The optimum fractionation of radiation to combine with immune checkpoint blockade is controversial. This study aimed to investigate the fractionated radiation to maximize immunity during combination therapy. To evaluate the abscopal effect, C57BL/6 hPD-1 knock-in mice bearing two syngeneic contralateral MC38 murine colon cancer tumors were treated with four distinct regimens of radiotherapy. Three fractions of 8 Gy were chosen as the optimal fractionation to combine with anti-PD-1 as the optimal fractionation for maximizing immunity. Anti-PD-1 administration enhanced both local and systemic antitumor immunity in a cytotoxic T cell-dependent manner. Meanwhile, the spleen exhibited decreased myeloid-derived suppressor cells (MDSCs) under combination treatment. Furthermore, RNA-sequencing revealed significantly increased tumor necrosis factor (TNF) receptors and cytokines associated with lymphocyte infiltration in the combining group. Here we demonstrate that the hypofractionation of 8 Gy × 3f was the optimum-fractionated dosage to maximize immunity, and the combination of anti-PD-1 showed promising results in boosting abscopal effect. Underlying mechanisms may include the activation of T cells and the reduction of MDSCs, which is achieved through the action of TNF and related cytokines. This study indicates a radioimmunotherapy dosage painting method that can be developed to overcome present limitations in tumor immunosuppression.

Durable complete response to immunotherapy with anti-PD-1 antibody nivolumab in a patient with oral squamous cell carcinoma presenting with lung metastasis: A case report

Although the optimal treatment method for metastatic oral cancer remains largely unknown, the present case suggests that immunotherapy is a potentially promising alternative for metastatic oral cancer in which other therapies are no longer effective.

Tissue-specific tumor microenvironments influence responses to immunotherapies

Objectives

Investigation of variable response rates to cancer immunotherapies has exposed the immunosuppressive tumor microenvironment (TME) as a limiting factor of therapeutic efficacy. A determinant of TME composition is the tumor location, and clinical data have revealed associations between certain metastatic sites and reduced responses. Preclinical models to study tissue‐specific TMEs have eliminated genetic heterogeneity, but have investigated models with limited clinical relevance.

Methods

We investigated the TMEs of tumors at clinically relevant sites of metastasis (liver and lungs) and their impact on αPD‐1/αCTLA4 and trimAb (αDR5, α4‐1BB, αCD40) therapy responses in the 67NR mouse breast cancer and Renca mouse kidney cancer models.

Results

Tumors grown in the lungs were resistant to both therapies whereas the same tumor lines growing in the mammary fat pad (MFP), liver or subcutaneously could be completely eradicated, despite greater tumor burden. Assessment of tumor cells and drug delivery in 67NR lung or MFP tumors revealed no differences and prompted investigation into the immune TME. Lung tumors had a more immunosuppressive TME with increased myeloid‐derived suppressor cell infiltration, decreased T cell infiltration and activation, and decreased NK cell activation. Depletion of various immune cell subsets indicated an equivalent role for NK cells and CD8⁺ T cells in lung tumour control. Thus, targeting T cells with αPD‐1/αCTLA4 or trimAb was not sufficient to elicit a robust antitumor response in lung tumors.

Conclusion

Taken together, these data demonstrate that tissue‐specific TMEs influence immunotherapy responses and highlight the importance in defining tissue‐specific response patterns in patients.