Anti-Programmed Cell Death Protein-1 Immunotherapy for Glioblastoma is Impaired by Systemic Chemotherapy but Enhanced in Combination With Locally Delivered Chemotherapy
Year: 2017
Type: article
Abstract: Glioblastoma (GBM) is the most common and aggressive primary adult brain tumor, with poor median survival of less than 18 mo despite the current aggressive treatments. Recently, new immunotherapies using checkpoint inhibitors to enable an antitumor immune response has led to dramatic regression of other cancer types. Programmed cell death protein-1 (PD-1) is a membrane receptor expressed on tumor infiltrating lymphocytes (TILs) that prevents autoimmunity by acting as an immune checkpoint. Binding and activation of PD-1 suppress the immune response by decreasing the survival of cytotoxic CD8+ T cells and cytokine production. GBM cells evade the immune system by overexpressing PD-L1, a ligand for PD-1 that activates this immune checkpoint. Checkpoint inhibitor agents such as monoclonal antibodies that bind PD-1 (anti-PD-1 mAb) block interactions between PD-1 and its ligands, thus potentially unleashing T cells for anti-GBM therapy. Recently, Mathios et al1 studied the interactions of anti-PD1 immunotherapy with adjuvant chemotherapy for GBM. Systemic chemotherapy (SC) has a well-known side effect of damaging bone marrow hematopoiesis, reducing a patient's ability to support an antitumor immune response. However, there are multiple methods to deliver local chemotherapy (LC) to tumors, including the FDA-approved slow-release carmustine-containing wafers. The authors assessed if LC combined with anti-PD1 immunomodulation is more effective than combining anti-PD1 with SC. First, the relative effects of SC and LC on the immune system were analyzed before combined treatment with immunotherapy. LC or SC was administered to mice 2 wk after intracranial implant of GL261 LUC cells to generate tumor xenografts. Treatment with carmustine LC and temozolomide SC showed similar results. SC was given 3 times a week for 2 wk, compared to one-time implantation of LC wafers resulting in constant (though nonlinear) drug release over 2 wk. SC-treated mice showed reduced CD3+ lymphocyte populations myelotoxicity noted by reduced bone marrow cellularity, compared to the LC and untreated control mice. Potentially irreversible lymphopenia in SC-treated mice persisted at 4 mo after treatment. Sixteen days following administration of chemotherapy, the LC group showed significantly higher lymphocyte levels compared to the SC and untreated control mice in blood, brain, and lymph nodes, and without signs of lymphopenia or myelotoxicity. There was no statistical significance between the LC and SC groups in long-term survival (LTS). When combined with the immunotherapy, LC+anti-PD-1 proved to be more effective than the monotherapies (SC alone, LC alone, or anti-PD-1 alone) or the SC+anti-PD-1 treatment. Anti-PD-1 was administered before the chemotherapy on the 10th d after implantation of tumor cells to allow growth of tumor xenograft. SC+anti-PD-1 showed similar LTS as anti-PD-1 alone. LC+anti-PD-1 treatment resulted in rapid tumor regression and significantly higher survival than SC+anti-PD-1 treatment. Additionally, SC+anti-PD-1 resulted in severe lymphodepletion, similar to that observed in mice treated with SC alone (Figure A). Lowering the SC dosage did not improve efficacy when paired with immunotherapy. Additionally, administering SC prior to anti-PD-1 abrogated the effects of the immunotherapy, resulting in LTS rates comparable to SC treatment alone.Figure.: LC+anti-PD-1 elicits a robust immune response, whereas SC+anti-PD-1 abrogates immune activation which the anti-PD-1 alone creates. A, SC in combination with anti-PD-1 resulted in lymphopenia in the peripheral blood, whereas LC+anti-PD-1 maintained high lymphocyte counts at all time pointe (n = 3 for all treatment groups). Bar plots show means ± SD. P values were calculated on the basis of 2-tailed Welch test. B–D, At day 21, LC+anti-PD-1 resulted in high numbers of TILs and increased percentage of Teff cells compared to SC+anti-PD-1 or LC alone. At day 30, SC groups showed lymphodepletion and decreased Teff function (decreased IFN-γ production). However, LC increased the Teff function, resulting in an increased ratio of Teff/Treg cells. Flow cytometry plots show results from a single mouse for each group. E, Box-and-whiskers plot and flow cytometry charts illustrating the percentage of tumor-infiltrating dendritic cells; gating on the CD45+ cells (leukocytes) infiltrating the brain and focusing on the CD11b+CD11c+ cells (dendritic cells). We observed an increased infiltration of dendritic cells in the LC-treated mice. From Mathios et al. Anti-PD-1 antitumor immunity is enhanced by local and abrogated by systemic chemotherapy in GBM. Sci Transl Med. 2016;8(370):370ra180. Reprinted with permission from AAAS.Enhanced TIL production in LC, anti-PD-1, and LC+anti-PD-1 treated mice was observed compared to untreated controls. Additionally, the ratio of effector T cells to regulatory T cells (Teff/Treg) in the brain was significantly higher in the anti-PD-1 and LC+anti-PD-1 compared to other treatment groups (Figure B), indicating an active antitumor immune response for those 2 treatments. Furthermore, the LC and LC+anti-PD-1 groups showed increased presence of tumor-infiltrating dendritic cells in the tumor microenvironment compared to other treatment groups, most notably the anti-PD-1 treatment and empty wafer control groups, indicating that LC may help recruit immune cells to the tumor microenvironment (Figure E). To further test immune system recruitment, mice were implanted with GL261 OVA+ cancer cells, and then administered adoptively transferred OVA-specific lymphocytes, then given chemotherapy 1 d after adoptive transfer. Flow cytometry analysis showed a higher percentage of OVA-specific T cells in the lymph nodes and tumor microenvironment in the LC+anti-PD-1 group than in other groups (anti-PD-1 alone, SC, and SC+anti-PD-1). These results were amplified more in tumor microenvironment than in lymph nodes, suggesting that LC+anti-PD-1 treatment increases antigen presentation and tumor antigen-specific immune activity. To test the immune memory response, long LTS mice (who survived the first treatment with GBM in remission) were rechallenged with new implantation of GL261 cells. In mice treated with the anti-PD-1, LC, or LC+anti-PD-1 regimens, new tumor growth was not observed, indicating an immune memory response based on tumor antigen recognition. Large tumors grew in long-term survivors of SC and SC+anti-PD-1 treatments that were rechallenged with new implants of GL261 cells. The abundance of memory T cells in the different groups was similar, but such cells were dysfunctional in the SC group. Overall, the results suggest that LC+anti-PD-1 treatment is superior to SC+anti-PD-1 treatment, as well as the other evaluated monotherapies. One reason may be that LC causes tumor cell apoptosis, exposing neoantigens in the tumor microenvironment to stimulate a robust immune response, shown especially by increased recruitment of effector T cells and antigen-presenting dendritic cells. LC can also promote an enhanced antitumor immune memory response, whereas the profound SC-associated immunosuppression is deleterious for proper development of antitumor immunity. These LC-mediated effects would synergize with anti-PD-1 treatment to stimulate and maintain active antitumor immunity. In addition to LC wafer strategy used in this study, there are many other strategies to locally deliver various therapeutic modalities to GBM cells in situ (ie, targeted agents, stereotactic radiation, focused ultrasound) that may synergize with immune checkpoint blockade or other immunomodulation strategies to further translating these results into efficacious combination strategies to improve GBM outcomes.
Source: Neurosurgery
Authors: Nathan A Ehrlich, Ray R Zhang, John S Kuo
Institution: University of Wisconsin–Madison
Language: English
Subfield: Genetics
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2771213459