Gut Microbiota-Based Immunotherapy: Engineered Escherichia coli Nissle 1917 for Oral Delivery of Glypican-1 in Pancreatic Cancer Original paper

What was studied?

Engineered Escherichia coli Nissle 1917 glypican-1 pancreatic cancer immunotherapy was investigated as an oral, microbiota-based vaccine strategy for pancreatic ductal adenocarcinoma (PDAC). This tumor overexpresses the heparan-sulfate proteoglycan GPC1 and is resistant to most systemic treatments. The authors constructed an EcN strain expressing a glypican-1–flagellin fusion (GPC1-FL) under a constitutive promoter, enabling the probiotic to survive in the gut, continuously release the tumour-associated antigen, and simultaneously provide a built-in adjuvant signal via TLR5 stimulation. They confirmed stable GPC1-FL expression in vitro, the recovery of engineered EcN from feces, and the persistence of antigen in the gastrointestinal tract after oral dosing, demonstrating that EcN can function as a living oral vaccine chassis in the gut environment.

Who was studied?

The work utilized murine pancreatic cancer PANC02 cells that were transfected to express human GPC1, allowing for the testing of antigen-specific responses against a relevant tumor target. This was confirmed by Western blot and flow cytometry, which showed that GPC1 did not alter cell growth and was present on the cell surface. Female C57BL/6 mice (three groups of five) then received oral immunizations on three spaced cycles with either engineered EcN GPC1-FL, wild-type EcN, or PBS, using gavage and feed mixing to ensure mucosal exposure. After the final dose, spleens, serum, and faeces were collected to assess systemic humoral responses, cytokine production, and in vivo bacterial persistence, providing a complete small-animal model of oral cancer vaccination with a probiotic vector.

Most important findings

Engineered EcN GPC1-FL induced a clear systemic anti-GPC1 IgG response that was significantly higher than both wild-type EcN and PBS, showing that oral delivery alone was sufficient to move the reaction from mucosal priming to systemic antibody production, a key step for any cancer vaccine. Cytokine analysis revealed a trend toward higher levels of IL-2 and IFN-γ in splenocytes restimulated with GPC1-expressing PANC02 cells. Still, the differences were not statistically significant, while serum IL-10 rose sharply in the EcN GPC1-FL group, indicating that the mucosal presentation of a self-related tumor antigen in the gut elicits a mixed activating–regulatory profile rather than a purely Th1 response. Western blotting of re-isolated EcN from faeces confirmed that the engineered strain persisted and continued to express the 110 kDa GPC1-FL protein in vivo, validating the gut as a production site. No weight loss or clinical toxicity occurred despite GPC1 baseline expression in normal tissues, supporting the preliminary safety of this oral EcN tumour vaccine concept.

Key implications

These data position engineered Escherichia coli Nissle 1917 glypican-1 pancreatic cancer vaccination as a plausible, patient-friendly immunotherapy that harnesses the gut–immune axis to present PDAC-associated antigens without injections. However, they also show that the antigen alone will not be enough to drive strong cytotoxic T cell responses and tumor rejection. Future iterations will need to combine the EcN GPC1-FL chassis with additional mucosal adjuvants, Th1-biasing signals, or checkpoint blockade to overcome the IL-10–skewed regulation seen here and to generate effector CD8⁺ T cells against GPC1⁺ tumours. For microbiome-signature databases, the study defines a precise construct—EcN background, constitutive GPC1-FL expression, oral route, detectable faecal antigen, systemic IgG, raised IL-10—that can be linked to PDAC cases with GPC1 overexpression and potentially to other GPC1⁺ malignancies such as breast and cholangiocarcinoma.