A Phase 2, Single-Arm, Open-Label Clinical Trial on Adjuvant Peptide-Based Vaccination in Dogs with Aggressive Hemangiosarcoma Undergoing Surgery and Chemotherapy.

To test the antitumor effect and safety of peptide-based anticancer vaccination in dogs with hemangiosarcoma undergoing the standard of care (SOC; surgery and doxorubicin), canine hemangiosarcoma cells were infected with Salmonella typhi Ty21a to release immunogenic endoplasmic reticulum stress-related peptides into the extracellular milieu via CX43 hemichannels opening. The infected tumor cell secretome constituted the vaccine. Following the SOC, dogs with biologically aggressive hemangiosarcoma were vaccinated a total of five times, once every 3 weeks, and were followed up with serial imaging. A retrospective population of dogs undergoing the SOC alone served as controls. The primary endpoints were the time to progression (TTP) and overall survival (OS), and the secondary endpoints were toxicity and immune responses. A total of 28 dogs were vaccinated along with the SOC, and 32 received only the SOC. A tumor-specific humoral response along with a vaccine-specific T-cell response was observed. Toxicity did not occur. The TTP and OS were significantly longer in vaccinated versus unvaccinated dogs (TTP: 195 vs. 160 days, respectively; p = 0.001; OS: 276 vs. 175 days, respectively; p = 0.002). One-year survival rates were 35.7% and 6.3% for vaccinated and unvaccinated dogs, respectively. In dogs with hemangiosarcoma undergoing the SOC, the addition of a peptide-based vaccine increased the TTP and OS, while maintaining a safe profile. Moreover, vaccinated dogs developed a tumor-specific response, supporting the feasibility of future phase three studies.

Sensitizing cancer cells to immune checkpoint inhibitors by microbiota-mediated upregulation of HLA class I.

Recent data have shown that gut microbiota has a major impact on the clinical response to immune checkpoint inhibitors (ICIs) in the context of solid tumors. ICI-based therapy acts by unlocking cognate cytotoxic T lymphocyte (CTL) effector responses, and increased sensitivity to ICIs is due to an enhancement of patients' tumor antigen (TA)-specific CTL responses. Cancer clearance by TA-specific CTL requires expression of relevant TAs on cancer cells' HLA class I molecules, and reduced HLA class I expression is a common mechanism used by cancer cells to evade the immune system. Here, we show that metabolites released by bacteria, in particular, phytosphingosine, can upregulate HLA class I expression on cancer cells, sensitizing them to TA-specific CTL lysis in vitro and in vivo, in combination with immunotherapy. This effect is mediated by postbiotic-induced upregulation of NLRC5 in response to upstream MYD88-NF-κB activation, thus significantly controlling tumor growth.

A Target Animal Effectiveness Study on Adjuvant Peptide-Based Vaccination in Dogs with Non-Metastatic Appendicular Osteosarcoma Undergoing Amputation and Chemotherapy.

Despite efforts to develop novel treatment strategies, human and canine osteosarcomas continue to have poor prognosis and limited overall survival. The aim of this clinical trial was to test the antitumor effect and safety of multiple dermal administrations of a peptide-based anticancer vaccine in dogs with non-metastatic appendicular osteosarcoma undergoing standard of care (SOC), consisting of limb amputation and adjuvant chemotherapy. Salmonella-infected canine osteosarcoma cells were induced to release immunogenic peptides in the extracellular space via Cx43 hemichannels opening; the secretome was collected and constituted the vaccine. Dogs with non-metastatic appendicular osteosarcoma were eligible for recruitment. Following limb amputation and adjuvant carboplatin, dogs were vaccinated on a monthly basis for six times and followed up with serial thoracic radiographs. A population of dogs undergoing SOC treatment (amputation and adjuvant carboplatin) before the vaccine was available served as controls. Primary endpoints were time to metastasis (TTM) and tumor-specific survival (TSS). Secondary endpoints were feasibility, toxicity, T-cell and humoral immune responses. A total of 20 dogs were vaccinated along with SOC and 34 received SOC only. Vaccine-specific humoral and T-cell responses were observed; their amplitude correlated with TSS. Vaccine-associated toxicity was not recorded. TTM and TSS were significantly longer in vaccinated versus unvaccinated dogs (TTM: 308 vs. 240 days, respectively; p = 0.010; TSS: 621 vs. 278 days, respectively; p = 0.002). In dogs with non-metastatic osteosarcoma undergoing SOC, the addition of a bacteria-based vaccination strategy increased TTM, thereby prolonging survival, while maintaining a safe profile. Additionally, vaccinated dogs developed a long-term tumor-specific response, as documented by the immunomonitoring of these patients over time. These results hold promise for future management of canine osteosarcoma.

Identification of a class of non-conventional ER-stress-response-derived immunogenic peptides.

Efforts to overcome resistance to immune checkpoint blockade therapy have focused on vaccination strategies using neoepitopes, although they cannot be applied on a large scale due to the "private" nature of cancer mutations. Here, we show that infection of tumor cells with Salmonella induces the opening of membrane hemichannels and the extracellular release of proteasome-generated peptides by the exacerbation of endoplasmic reticulum (ER) stress. Peptides released by cancer cells foster an antitumor response in vivo, both in mice bearing B16F10 melanomas and in dogs suffering from osteosarcoma. Mass spectrometry analysis on the supernatant of human melanoma cells revealed 12 peptides capable of priming healthy-donor CD8+ T cells that recognize and kill human melanoma cells in vitro and when xenotransplanted in vivo. Hence, we identified a class of shared tumor antigens that are generated in ER-stressed cells, such as tumor cells, that do not induce tolerance and are not presented by healthy cells.