Application of group A streptococcal collagen-like protein 1-expressing Lactococcus as a novel immunotherapeutic against pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is a fatal malignancy characterized by an immunosuppressive tumor environment. Neutrophil extracellular traps (NETs) have gained recognition in playing a critical role in cancer progression and formulation of the PDAC TME, making them a target for novel PDAC therapies. Herein, we utilize a Lactococcus strain expressing group A streptococcal collagen-like protein 1 (Scl1) to stimulate anti-tumor immunity and inhibit cancer promoting NETs. Orthotopically implanted male and female C57BL6/J or NET-deficient PAD4−/− mice were intra-tumorally or intra-peritoneally injected with Lactococcus wild-type lacking Scl1, Scl1-producing Lactococcus::620, or PBS control. Sera were collected to assess circulating NET markers. A decreased tumor burden, as well as infiltration of anti-tumor CD8 + T and dendritic cells was observed in mice treated with Scl1-expressing Lactococcus::620 compared to Lactococcus wild-type and PBS control. Mice treated with Lactococcus::620 showed reduced cell-free DNA in their sera as a marker for decreased NETosis. These effects were abrogated in PAD4−/− mice, suggesting a NET-dependent anti-tumor effect by Scl1. This study demonstrates a novel therapeutic concept against PDAC using an engineered Scl1-expressing Lactococcus strain. Our results advocate for Scl1-based cancer therapy as an immunomodulator of the PDAC tumor microenvironment.